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Design of Printed Circuit Board for DC-DC converter
First fr0m the switching power supply design and production process to start the dession of it, first talk about the design of the printed circuit board. Switching power supply works in high frequency and high pulse state, which belongs to a special type of analog circuit. The principle of high frequency circuit wiring must be followed when laying the board.
Layout: The pulse voltage wiring shall be as short as possible, including the wiring fr0m the 1nput switching tube to the transformer and the wiring fr0m the output transformer to the rectifier tube. The pulse current loop is as small as possible, such as the 1nput filter capacitor positive to the transformer to the switch tube return capacitor negative. In the circuit fr0m the output end of the transformer in the output part to the rectifier tube to the output inductor to the output capacitor and back to the transformer, the X capacitor should be as close as possible to the 1nput end of the switching power supply, and the 1nput line should not be parallel to other circuits.
The Y capacitor shall be placed at the chassis ground terminal or FG connection. The common mode electric induction is kept at a distance fr0m the transformer to avoid magnetic coupling. If it is not easy to handle, a shield can be added between the common mode inductor and the transformer. The above items have a greater impact on the EMC performance of the switching power supply.
Generally, two output capacitors can be used, one close to the rectifier tube and the other close to the output terminal, which can affect the output ripple index of the power supply. The parallel effect of two small-capacity capacitors should be better than that of one large-capacity capacitor. Keep a certain distance between the heating device and the electrolytic capacitor to prolong the service life of the whole machine. The electrolytic capacitor is the bottleneck of the service life of the switching power supply. For example, the transformer, power tube and high-power resistor should keep a distance fr0m the electrolysis, and a heat dissipation space should be left between the electrolysis. If conditions permit, they can be placed at the air inlet.
Attention shall be paid to the control part: the wiring of the high-impedance weak signal circuit shall be as short as possible, such as the sampling feedback loop, which shall be avoided fr0m interference as far as possible during processing. The current sampling signal circuit, especially the current control circuit, may cause some unexpected accidents if it is not handled properly.


Composition structure of DC motor
The structure of DC motor shall be composed of stator and rotor. The stationary part of the DC motor during operation is called the stator. The main funct1on of the stator is to generate a magnetic field. It is composed of a frame, a main magnetic pole, a commutating pole, an end cover, a bearing and a brush device. The rotating part during operation is called the rotor, whose main funct1on is to generate electromagnetic torque and induced electromotive force. It is the hub for energy conversion of DC motor, so it is usually called the armature, which is composed of shaft, armature core, armature winding, commutator and fan.
Stator
(1) Main magnetic pole
The funct1on of the main magnetic pole is to generate an air gap magnetic field. The main magnetic pole is composed of a main magnetic pole iron core and an excitation winding. The iron core is generally made by laminating and riveting 0.5mm ~ 1.5mm thick silicon steel sheet. It is divided into a pole body and a pole shoe. The part above the excitation winding is called the pole body, and the part below the excitation winding is called the pole shoe. The pole shoe is wider than the pole body, which can not only adjust the distribution of the magnetic field in the air gap, but also facilitate the fixation of the excitation winding. The excitation winding is made of insulated copper wire and sleeved on the main pole core. The whole main magnetic pole is fixed on the machine base by a screw,
(2) Commutating pole
The commutating pole is used to improve the commutation and reduce the commutation spark that may be generated between the brush and the commutator during the operation of the motor. It is generally installed between two adjacent main magnetic poles and consists of a commutating pole core and a commutating pole winding. The commutating pole winding is formed by winding insulated wires and sleeved on the commutating pole iron core, and the number of the commutating poles is equal to that of the main magnetic poles.
(3) Frame
The casing of the motor stator is called the frame. There are two funct1ons of the base:
One is used for fixing the main magnetic pole, the commutating pole and the end cover, and plays the role of supporting and fixing the whole motor;
Secondly, the frame itself is also a part of the magnetic circuit, which constitutes the magnetic path between the poles, and the part through which the magnetic flux passes is called the yoke. In order to ensure that the base has sufficient mechanical strength and good magnetic permeability, it is generally made of cast steel or welded by steel plate.
(4) Brush device
The brush device is used to introduce or extract DC voltage and DC current. The electric brush device is composed of an electric brush, a brush holder, a brush rod and a brush rod seat. The brush is placed in the brush holder and pressed by the spring to ensure good sliding contact between the brush and the commutator. The brush holder is fixed on the brush rod, which is installed on the circular brush rod seat and must be insulated fr0m each other. The brush rod seat is installed on the end cover or the bearing inner cover, and the circumferential position can be adjusted and fixed after adjustment.


DC motor has the advantage of precise control, but it has large power consumption
As we all know, DC motor has the advantage of precise control, but it has large power consumption, low efficiency and small torque. If the high-power stepper motor is se1ected, the PWM constant current control method can be adopted in order to reduce power consumption.
A direct current machine is a rotating electrical machine that converts direct current electrical energy into mechanical energy (direct current motor) or converts mechanical energy into direct current electrical energy (direct current generator). It is a motor that can realize the mutual conversion of DC electric energy and mechanical energy. When it operates as a motor, it is a direct current motor that converts electrical energy into mechanical energy; When operating as a generator, it is a direct current generator that converts mechanical energy into electrical energy.
The DC motor consists of a stator and a rotor with a certain air gap between them. The main feature of its construction is an armature with a commutator. The stator of DC motor is composed of frame, main magnetic pole, commutating magnetic pole, front and rear end covers and brush holder. The main magnetic pole is the main component to produce the air gap magnetic field of the DC motor, which is composed of permanent magnets or laminated cores with DC excitation windings.
The rotor of DC motor is composed of armature, commutator (also called commutator) and shaft. The armature consists of an armature core and an armature winding. The armature core is made of laminated silicon steel sheets, and the slots are uniformly distributed on the outer circle of the armature core, and the armature windings are embedded in the slots. Commutator is a mechanical rectifying component. After the commutator segments are folded into a cylindrical shape, the commutator segments are formed into a whole by metal clips or plastics. The commutators are insulated fr0m each other. The quality of the commutator has a great influence on the operation reliability.
Basic composition of DC motor
The DC motor consists of a stator and a rotor with a certain air gap between them. Benefits: Reply to the information on the official account of the E-Fever Friends Network, and get a free set of model electricity information.
The stator of DC motor is composed of frame, main magnetic pole, commutating magnetic pole, front and rear end covers and brush holder. The main magnetic pole is the main component to produce the air gap magnetic field of the DC motor, which is composed of permanent magnets or laminated cores with DC excitation windings.
The rotor of DC motor is composed of armature, commutator (also called commutator) and shaft. The armature consists of an armature core and an armature winding. The armature core is made of laminated silicon steel sheets, and the slots are evenly distributed on the outer circle of the armature core, and the armature windings are embedded in the slots. \n Commutator is a mechanical rectifying component. After the commutator segments are folded into a cylindrical shape, the commutator segments are formed into a whole by metal clips or plastics. The commutators are insulated fr0m each other. The quality of the commutator has a great influence on the operation reliability.


The method to prevent the first electric explosion of the prototype
The method to prevent the first electric explosion of the prototype is very simple, that is, to connect an incandescent lamp in series with the 1nput line of the switching power supply for protection, as shown in the figure below.
Note that the series incandescent lamp does not need to be electrified with output load for the first time, and is directly electrified with no load. \n Without large current
If the incandescent lamp is not on, or it is on and then off when it is just powered on (the first light is caused by the 1nput surge current), it indicates that there is no large current 1nput to the switching power supply. At this time, you can test whether the output of the power supply is normal voltage. If the output is normal, the incandescent lamp can be removed for normal debugging.
If the output voltage is abnormal, it can continue to connect to the incandescent lamp until the cause is found and solved, and then remove the incandescent lamp for normal debugging.
In case of large current
If the incandescent lamp is on all the time after being powered on, or the incandescent lamp is in the intermittent cycle of on-off-on, it indicates that there is a large current inside the switching power supply. At this time, turn off the power supply and check the switching power supply carefully. Repeat this method until the no-load switching power supply is normal, and then remove the incandescence lamp for normal debugging.
Without large current
If the switching power supply does not enter a dangerous state (the output of the switching power supply is normal or the output voltage of the switching power source is jumping up and down but does not cause a large 1nput current), the 1nput current flowing into the switch power supply at this time is very weak, which can be equivalently regarded as a large Zo.
Assuming that the power consumption of the power supply is 2.2 W at this time, the average current on Zo is about 0.01 A, and the impedance on Zo is about 220/0.01, which is about 22 K.
The cold state resistance of an incandescent lamp with more than ten watts or tens of watts is about tens of ohms to hundreds of ohms. Here I assume that Z1 = 100Ω. According to the voltage division ratio of the impedance, the voltage drop on the incandescent lamp is very small, so the incandescent lamp does not light.
In case of large current 1nput
If the switching power supply does not enter the dangerous state (the 1nput of the switching power supply has a large current), the current is very large, which can be equivalently regarded as a very small Zo.
Assuming that the average current flowing into the power supply at this time is 5A, which is equivalent to the average current on Zo being 5A, the impedance on Zo is about 220/5, which is about 44Ω.
The cold state impedance of an incandescent lamp of more than ten watts or tens of watts is about tens of ohms to hundreds of ohms. Here I assume that Z1 = 100Ω. According to the voltage division ratio of the impedance, the voltage drop on the incandescent lamp is relatively large.
In addition, another characteristic of incandescent lamps is that the hot impedance is much larger than the cold impedance. The experiment shows that the hot impedance is about 10 times larger than the cold impedance. Here I assume that the thermal impedance is 10 times larger than the cool impedance.


low-cost method to prevent the prototype of the first time on the electric explosion machine problems
After so many years of switching power supply design, a very worrying thing for me is that the new prototype is powered on for the first time, and I am worried about the explosion of the machine. I believe that many engineers have the same deep understanding as me. They check their new prototype again and again before powering on, fearing that there will be wrong welding, reverse lap welding or short circuit in some places, and even sweep the workbench clean just in case.
According to the different experience of engineers and the different degree of care, the prototype has a certain probability of explosion when it is powered on for the first time, and it is on tenterhooks. Of course, the word "fear" can only be used for some engineers, some of whom are naturally not afraid of explosion and the "Zizi" sound when doing pressure-resistant experiments, and their faces do not change color and their hearts do not beat (I don't know if they are faking it).
It is very painful to blow up the machine, especially when such a brand new prototype has no power supply with good parameters, the power supply may be abnormal, and it will be more difficult to repair the explosion?
For this reason, due to the limited equipment configuration, many engineers use various methods and experience to avoid the explosion, such as slowly increasing the 1nput voltage while watching the state of the current, watching the power changes on the power meter, once the situation is not right, immediately cut off the power, which can indeed avoid some abnormal situations, but sometimes the hand speed is not fast enough to explode.
Below to share with you a pro-test effective, and very low-cost method to prevent the prototype of the first time on the electric explosion machine problems, the hands of AC source and other equipment engineers please ignore!


Design Summary of DC-DC Switching Power Supply
The layout of DC-DC is very important, which will directly affect the stability and EMI effect of the product. The experience/rules are summarized as follows: 1. Handle the feedback loop well. The feedback line should not go under Schottky, inductor (L1) or large capacitor, and should not be surrounded by a large current loop. If necessary, a 100 pF capacitor can be added to the sampling resistor to increase stability (but transients are slightly affected);
2. The feedback line should be thin rather than thick, because the wider the line is, the more obvious the antenna effect is, which affects the stability of the loop. A 6-12 mils thread is generally used;
3. All capacitors shall be as close to the IC as possible;
4. The inductance shall be se1ected according to the capacity of 120-130% of the specification, and shall not be too large, which will affect the efficiency and transient state;
5. Capacitor shall be se1ected according to 150% of the capacity in the specification. If chip ceramic capacitors are used, if 22uF is used, it is better to use two 10uF parallel capacitors. If the cost is not sensitive, the capacitance can be larger. Special tips: output capacitor, if the use of aluminum electrolytic capacitor, remember to use high-frequency low resistance, not casually put a low-frequency filter capacitor!
6. Reduce the surrounding area of large current loop as much as possible. If it is not convenient to narrow it, it can be made into a narrow slit by copper plating.
7. Do not use thermal resistance pads on critical loops, as they introduce unwanted inductance characteristics.
8. When using the ground plane, try to maintain the integrity of the ground plane under the 1nput switching loop. Any cutting of the ground plane in this area will reduce the effectiveness of the ground plane, and even the signal vias through the ground plane will increase its impedance.
9. Vias can be used to connect decoupling capacitors and the ground of the IC to the ground plane, which can minimize the loop. However, it is important to keep in mind that the via inductance is approximately between 0.1 and 0.5 nH, depending on the via thickness and length, which can increase the total loop inductance. The use of multiple vias is desirable for low impedance connections.
In the above example, the additional vias to the ground plane do not help to reduce the length of the CIN loop. But in another example, because the path of the top layer is very long, it is very effective to reduce the circuit area through the via hole.


PCB Design Considerations in Power Management
With the rapid development of science and technology products, the PCB design of power products is facing greater challenges, including power conversion efficiency, thermal analysis, power plane integrity and EMI (electromagnetic interference).
With the increasingly extensive and diversified applications in the industry, power supply products are also developing in the direction of high frequency, high efficiency, high density, low voltage, large current and diversification. At the same time, the packaging structure and dimensions of power supply products are becoming more and more standardized to meet the requirements of the global market.
The first is power conversion efficiency. Conversion efficiency refers to the ratio of the output power of the power supply to the 1nput power actually consumed. In practical applications, the electric energy can not be completely converted, and there will be a certain amount of energy consumption in the middle. Therefore, no matter what kind of circuit, there must be an efficiency problem in the power conversion. For a linear power supply, the heat dissipation of the LDO needs to be considered; For the switching power supply, the loss of the switch tube should be considered.
Secondly, energy loss will inevitably produce heat, which involves the problem of heat dissipation. In addition, as the load becomes heavier, the power consumption of the power supply chip increases, so the thermal distribution is a problem that has to be considered in the power supply design.
The third is the integrity design of the power plane. To maintain the integrity of the power supply is to maintain a stable power supply. In a real system, there is always noise of different frequencies. Such as PWM natural frequency or PFM variable frequency control signals, fast di/DT can produce current ripple signals, so a low impedance power plane design is necessary.
Finally, there is the issue of EMI (electromagnetic interference). Switching noise is generated when the switching power supply is switched on and off continuously. If the loop inductance is not considered in the design process, the excessive return path will cause EMI problems.
The industry is always looking for ways to improve the success rate of power PCB design. Experience shows that in the design process, if possible risks can be predicted and avoided in advance, the success rate will be greatly improved. Therefore, it is particularly important to choose a suitable design simulation tool.


LDO VS DC-DC converter
Generally speaking, DCDC must be se1ected for boost, and DCDC or LDO should be se1ected for buck in terms of cost, efficiency, noise and performance.
LDO is small in size and has less interference. When the voltage difference between the 1nput and output is large, the conversion efficiency is low.
The advantage of DC-DC is that it has high conversion efficiency and large current, but the output interference is large and the volume is relatively large.
LDO generally refers to a linear regulator, Low Drop Out, while DC/DC is a general term for linear and switching regulators.
If your output current is not very large (such as less than 3A), and the 1nput and output voltage difference is not large (such as 3.3 V to 2.5 V), you can use LDO regulator (the advantage is that the ripple of output voltage is very small). Otherwise, it is better to use a switching regulator. If it is a boost, it can only use a switching regulator (if the ripple control is not good, it will easily affect the system work).
Choice of LDO
When the designed circuit has the following requirements for the shunt power supply:
1. High noise and ripple rejection;
2, that occupy PCB board area is small, such as handheld electronic products such as mobile phone and the like;
3. Inductors are not allowed to be used for circuit power supply, such as mobile phones;
4. The power supply shall have the funct1ons of instantaneous calibration and output status self-check;
5. The voltage regulator is required to have low voltage drop and low power consumption;
6. Low line cost and simple scheme are required;
At this point, the LDO is the most appropriate choice, while meeting the various requirements of the product design. The above is the power chip se1ection method, I hope to help you, you need to design, according to the different projects to choose.


LDO VS DC-DC converter
DCDC means DC to DC (conversion of different DC power supply values). Anything that meets this definition can be called a DCDC converter, including an LDO. But the general saying is that the DC to (to) DC is realized by the switching mode of the device called DCDC.
LDO means low voltage drop, and here's a paragraph that explains: Low dropout (LDO) linear regulators have the advantages of low cost, low noise, and low quiescent current. It also requires few external components, typically just one or two bypass capacitors. The new LDO linear regulator achieves an output noise of 30 μV, a PSRR of 60 dB, a quiescent current of 6 μA, and a voltage drop of only 100 mV. The main reason why LDO linear regulators can achieve this level of performance is that the pass transistor is a P-channel MOSFET, while ordinary linear regulators use PNP transistors. The P-channel MOSFET is voltage-driven and does not require current, so the current consumed by the device itself is greatly reduced; On the other hand, in a circuit using a PNP transistor, in order to prevent the PNP transistor fr0m entering a saturated state and reducing the output capability, the voltage drop between the 1nput and the output should not be too low; The voltage drop across the P-channel MOSFET is approximately equal to the product of the output current and the on-resistance. Because the on-resistance of the MOSFET is very small, the voltage drop across it is very low.
If the 1nput voltage and the output voltage are very close, the LDO regulator is the best choice to achieve high efficiency. As a result, LDO regulators are often used in applications that convert the voltage fr0m a lithium-ion battery to a 3 V output voltage. Although the last 10% of the battery's energy is not used, the LDO regulator can still ensure that the battery operates for a long time with low noise.
If the 1nput voltage and the output voltage are not very close, it is necessary to consider using a switch-type DCDC, because fr0m the above principle, we can know that the 1nput current of the LDO is basically equal to the output current. If the voltage drop is too large, the energy consumed on the LDO is too large, and the efficiency is not high.
The DC-DC converter includes a boost, a buck, a boost/buck, and an inverter circuit. The DC-DC converter has the advantages of high efficiency, high output current, and low quiescent current. As integration increases, many new DC-DC converters require only a few external inductors and filter capacitors.


About the LDO
In the past, I often saw that the chip was LDO and thought it was the name of a company. Now we know that LDO is a low dropout regulator, which means a low dropout linear regulator, as opposed to a traditional linear regulator. Traditional linear regulators, such as 78xx series chips, require the 1nput voltage to be more than 2 V ~ 3 V higher than the output voltage, otherwise they will not work properly. However, in some cases, this condition is obviously too harsh, such as 5 V to 3. 3 V, the 1nput and output voltage difference is only 1. 7 V, obviously does not meet the conditions. In view of this situation, there is a LDO power conversion chip. There are many companies producing LDO chips, such as ALPHA, Linear (LT), Micrel, National semiconductor, TI and so on.
What is an LDO (Low Dropout) regulator?
An LDO is a linear voltage regulator. Linear regulators use transistors or FETs operating in their linear region to subtract excess voltage fr0m the applied 1nput voltage, producing a regulated output voltage. The droop voltage is the minimum value of the difference between the 1nput voltage and the output voltage required to maintain the output voltage within 100 mV above or below its rated value. An LDO (low dropout) regulator with a positive output voltage typically uses a power transistor (also known as a pass device) as the PNP. This transistor is allowed to saturate, so the regulator can have a very low dropout voltage, typically around 200 mV. In comparison, a conventional linear regulator using an NPN compound power transistor has a voltage drop of about 2 V. The negative output LDO uses NPN as its pass device and operates in a similar mode to the PNP device of the positive output LDO.
Newer developments use CMOS power transistors, which provide the lowest voltage drop. With CMOS, the only voltage drop across the regulator is due to the ON resistance of the power device load current. If the load is small, the voltage drop produced by this method is only tens of millivolts.


Power supply chip selection method
What is a power chip? What does it do? What should be considered when choosing a power supply chip? 1nput Voltage Linear Regulation: The relative effect of a linear change in 1nput voltage on the output voltage
Output voltage load regulation: the relative change of output voltage when the load current changes \n Output voltage accuracy: error range of the output voltage of the device
Load transient response: The fluctuation of the output voltage when the load current changes rapidly fr0m a small value to a maximum value.
Does the power chip choose DC/DC or LDO?
It depends on your application. For example, in the case of boosting, of course, only DC/DC can be used, because LDO is a voltage drop type and can not be boosted. In addition, look at their main features:
DC/DC: high efficiency, high noise;
LDO: Low noise, small quiescent current;
Therefore, if it is used in the case of large voltage drop, choose DC/DC because of its high efficiency, while LDO will lose a large part of its efficiency because of large voltage drop;
If the voltage drop is small, choose LDO because of its low noise, clean power supply, simple peripheral circuit and low cost.
LDO is a low dropout regulator, which means a low dropout linear regulator, as opposed to a traditional linear regulator. Traditional linear regulators, such as 78xx series chips, require the 1nput voltage to be more than 2 V ~ 3 V higher than the output voltage, otherwise they will not work properly. However, in some cases, this condition is obviously too harsh, such as 5 V to 3. 3 V, the 1nput and output voltage difference is only 1. 7 V, which obviously does not meet the conditions. In view of this situation, there is a LDO power conversion chip.
LDO linear step-down chip: The principle is equivalent to a resistor divider to achieve step-down, the energy loss is large, the reduced voltage is converted into heat, the greater the voltage difference and load current of step-down, the more obvious the chip heating. The package of this kind of chip is relatively large, which is convenient for heat dissipation.
LDO linear step-down chips such as: 2596, L78 series.
DC/DC step-down chip: In the process of step-down, the energy loss is relatively small, and the chip heating is not obvious. The chip package is relatively small, and PWM digital control can be realized.


how can the magnetic energy be converted into current when the circuit is disconnected
The magnetic energy in the inductor will be converted back into electricity when the inductor is powered off, but the question is: how can the magnetic energy be converted into current when the circuit is disconnected and the current has nowhere to go? Quite simply, a high voltage will appear across the inductor! How high is the voltage? Infinitely high until any medium that blocks the current fr0m proceeding is broken down. Here we look at the second characteristic of the inductor, the boost characteristic. When the circuit is broken, the energy in the inductor is converted back into electricity in the form of an infinite voltage, and how high the voltage can rise depends only on the breakdown voltage of the dielectric transformer.
When the oscillator in the system outputs a low level pulse, the switch vT will be turned off, which is equivalent to the switch being turned off. The 1nput voltage Vin is superposed with the induced voltage VL (positive on the right and negative on the left) on the inductor of the energy storage element to charge the capacitor C of the energy storage element through the diode VD (charging current iC), and the energy in the inductor is released, as shown in fig. 4. Due to the high frequency of the oscillator, typically tens of kilohertz to hundreds of kilohertz, the voltage across the capacitor VC = VIN + VL-VF over a certain period of time. Where VF is the forward voltage drop of the diode. The induced voltage VL generated on the inductor can generally reach tens of volts, so the voltage on VC can often reach tens of volts, and VIN is generally only 1.5-3 V. This is the basic operating principle of the boost circuit. The maximum voltage across the switch is equal to VL + VIN. Here, the diode VD mainly plays a blocking role to prevent the charged capacitor fr0m discharging to the ground through the switch tube when the switch tube is turned on. It can be seen fr0m fig. 3 that the peak current IPK of the inductor is much larger than the average current supplied to the load, typically 2-3 times IOUT.
Now let's make a summary of the above content:
Below is the positive voltage generator, where you keep flipping the switch and you get an infinitely high positive voltage fr0m the 1nput. How high the voltage goes depends on what you put on the other end of the diode to make the current go somewhere. If nothing is connected, the current has nowhere to go, so the voltage rises high enough to break down the switch, and the energy is dissipated as heat. Then there's the negative voltage generator, where you keep flipping the switch, and you get an infinitely high negative voltage fr0m the 1nput.
After understanding the boost circuit of the boost DC-DC converter, let's take a look at the operation principle of its voltage regulation circuit. In normal operation, the circuit does not stabilize the voltage. If a load is applied, the voltage VOUT will drop, and its output voltage is affected by the operating frequency of the oscillator and the size of the inductor L.


Principle of Inductive DC-DC Booster
Inductance is a component that we use for a long time in transformer design. Its main funct1on is to convert electric energy into magnetic energy and then store it. It should be noted that although the inductor is similar in structure to a transformer, it has only one winding. This article mainly introduces the principle of inductor DC-DC booster, and this article belongs to the basic nature, suitable for those who do not understand the characteristics of the inductor, but at the same time interested in the booster friends. Some of the theoretical knowledge in the article can be found on the Internet, so I will not repeat it here.
The boosting circuit of the boosting DC-DC converter consists of an oscillator for outputting square waves (pulses), a switching tube vT, an energy storage element inductor L, a unidirectional conduction diode VD and an energy storage element capacitor C. Because the switch tube works in the switching state, it can be represented by the switch s.
To fully understand the principle of inductive boost, we must first understand the characteristics of inductors, including electromagnetic conversion and magnetic energy storage. These two points are very important, because all the parameters we need are derived fr0m these two features. As you all know, the picture above is an electromagnet, and a battery energizes a coil. Some people may wonder, what is there to analyze such a simple picture? We are going to use this simple diagram to analyze what happens at the moment of power on and power off. Coils (later called inductors) have a characteristic-electromagnetic conversion, electricity can be changed into magnetism, and magnetism can be changed back into electricity. At the moment of energization, the electricity changes into magnetism and is stored in the inductor in the form of magnetism. The transient magnetic field will become electricity and be released fr0m the inductor when the power is off.
In the normal operation state of the converter, when the oscillator outputs a high level pulse, the switch tube vT is turned on, which is equivalent to the closing of the switch. The process is shown in Figure 2. At this time, the 1nput voltage VI flows through the inductor L and the switch s to the ground to form the inductor current iL, and the operation process is as shown in fig. 3. By the time the switch is turned off, the inductor current reaches its maximum value, PK, and energy is stored in the inductor. There is a very small on-resistance RDS (on) across the switch, so there is a small tube voltage drop Von (SW) across the switch.


Boost DC-DC Converter Circuits for Beginners
I believe that many electronic engineers will come into contact with a variety of circuits, according to different requirements to design different circuits, then many times will also come into contact with DC-DC circuits, so do you know how to design? Then let me lead you to learn it.
The DC-DC converter is divided into three types: a Boost boost type DC-DC converter, a BUCK buck type DC-DC converter, and a Boost-BUCK buck-boost type DC-DC converter.If the circuit adopts a DC-DC conversion circuit, the circuit should be a Boost boost type DCDC conversion circuit, The 1nput voltage and the output voltage are both DC voltages, and the 1nput voltage is lower than the output voltage. The basic topology is as shown in the figure
It is very necessary for the newcomers who have just begun to contact and learn circuit design to have a solid understanding and mastery of the operation of DC-DC converters. In normal work, as a common energy converter, boost DC-DC converter is often used in power, photovoltaic power transformation and other systems. This paper will briefly analyze and introduce the circuit operation principle of this DC-DC converter, hoping to be helpful to the work of designers.
The working principle is divided into two steps:
Step 1: The switch tube is closed (the MOS tube is conducted, which is equivalent to a wire), and the 1nput DC voltage flows through the inductor L. The funct1on of that diode D1 is to prevent the capacitor C fr0m discharge to the ground and at the same time to act as a freewheel. Because the 1nput voltage is DC, the current in the inductor increases linearly at a certain rate, which is related to the inductance factor. As the inductor current increases, some energy is stored in the inductor.
Here we take the most basic boost DC-DC converter as the object for analysis, in order to facilitate your understanding. On the premise of normal operation, the working circuit of this converter is mainly composed of two parts: the boost circuit and the voltage regulation circuit. We will introduce the operation of these two circuits for the designers and developers respectively.
Step 2, when that switch tube is tur off, because the current of the inductor can not change suddenly, that is to say, the current flowing through the inductor L doe not become zero immediately, but slowly becomes zero fr0m the value when the charging is completed, this require a process, and the original circuit loop has been disconnected, so the inductor can only discharge through a new circuit, that is to say, the inductor begins to charge the capacitor C2, and the voltage at both ends of the capacitor rises


automotive-grade high-isolation DC/DC power supply
Current Logic series is an automotive-grade high-isolation DC/DC power supply product planned and developed to meet the requirements of the automotive market for high withstand voltage, excellent EMI and SMD packaging of power modules. This series of products has an ultra-wide 1nput voltage range of 6-42VDC, high isolation withstand voltage of 3000VAC, enhanced insulation, efficiency up to 80%, and can meet the wide operating temperature range of -40 ℃ to + 105 ℃ (85 ℃ starts derating). The height of this series of products is as low as 8.5 mm, the creepage distance is 4.5 mm, and the electrical clearance is 4.2 mm. According to the IATF16949 system control, the whole machine meets the AEC-Q100 automotive standard and has a very high cost performance.
DC-DC power module is a kind of switching power supply which uses power semiconductor switching devices to realize DC-DC power conversion. DC-DC power module is widely used in remote and data communications, computers, office automation equipment, industrial instrumentation, military, aerospace and other fields, involving all walks of life in the national economy, and has broad application prospects in the field of remote and digital communications.
It can be widely used in automobile, industrial control, electric power, instrumentation, communication and other fields. CUWF2405J (Y) T-6 WR3 is used as the main power supply to supply power to the monitoring board when it is used in the super capacitor vehicle, which can monitor the heat change in the charging and discharging process of the super capacitor and the voltage deviation in the working process of the capacitor in real time. \n With the rapid development of electronic technology, the application field of switching power supply is more and more extensive, and the working environment is more and more severe. Statistics show that the reliability of electronic components decreases by 10% when the temperature rises by 2 ℃, and the life span at 50 ℃ is only 1/6 of that at 25 ℃.
● 7:1 ultra-wide 1nput voltage range: 6-42VDC
● Isolation voltage: 3000VAC, reinforced insulation
● Up to 80% efficiency
● 1nput undervoltage protection, output short circuit, overcurrent and overvoltage protection
● Creepage distance up to 4.5mm, electrical clearance up to 4.2mm
● Operating temperature range: -40 ℃ to + 105 ℃
● EMI meets automotive standard EN55025/CISPR25 level 4
● The complete machine meets the AEC-Q100 automotive standard (under test)
● Products are controlled according to IATF16949 system


Current Logic has planned and developed a series of low-power module power supplies
In the application of ultra-wide voltage 1nput, the power module has insufficient start-up ability at low 1nput voltage and large start-up circuit loss at high 1nput voltage, and the contradiction between the two cannot be solved. In order to adapt to the more severe 1nput voltage environment, some terminal devices require switching power supply with ultra-wide 1nput voltage range. In order to solve the above contradictions and broaden the 1nput voltage range and product layout, Current Logic has planned and developed a series of low-power module power supplies, which can be compatible with various nominal 1nput voltages such as 5V/12V/15V/24V. This series of products has an ultra-wide 1nput voltage range of 4.5-36VDC, an isolation withstand voltage of up to 3000 VDC, and can meet the operating temperature range of -40 ℃ to + 105 ℃. The no-load power consumption is as low as 0.12 W. It has 1nput undervoltage protection, output short circuit and overcurrent protection. It is a low-power power supply product with high cost performance.
DC-DC is a newly developed miniaturized power switch module, which is composed of small surface mount integrated circuits and miniature electronic components by using microelectronics technology. The use of DC-DC power supply module is helpful to simplify the design of power supply circuit, shorten the development cycle and achieve better performance. It can be widely used in various digital instruments and intelligent instruments.
II. Product Application
It can be widely used in medical, industrial control, electric power, instrumentation, communications and other fields.
III. Product Features
● 8:1 ultra-wide 1nput voltage range: 4.5-36VDC
● Low no-load power consumption of 0.12 W
● Isolation withstand voltage up to 3000VDC
● Operating temperature range: -40 ℃ to + 105 ℃
● 1nput undervoltage protection, output short circuit and overcurrent protection
● International standard pin mode
● Meet EN 62368 certification standard \n DC-DC power modules are widely used in power electronics, military industry, scientific research, industrial control equipment, communication equipment, instrumentation, switching equipment, access equipment, mobile communications, routers and other communication fields and industrial control, automotive electronics, aerospace and other fields. Because of the advantages of short design cycle, high reliability and easy system upgrade, power modules are used more and more widely. Especially in recent years, due to the rapid development of data services and the continuous promotion of distributed power supply system, the growth rate of power supply module has exceeded that of primary power supply.


How to Use High Power DC/DC in Single Board Computer Design
Single-board computers for industrial applications were once used only as simple logic controllers handling human-machine interfaces (HMIs), providing various control funct1ons and network communications. Today, single-board computers serve as the brains of complex systems used in industrial robotics, machine vision, and factory automation.
To provide the required processing power, the current generation of single-board computers contains 16 core central processing units (CPUs), 256 GB of double data rate-4 memory, multiple 10 Gigabit Ethernet and USB ports, digital I/O, and a Serial Advanced Technology Attachment interface. Next-generation systems also include field-programmable gate arrays, graphics processing units, and application-specific integrated circuits capable of running artificial intelligence and machine learning algorithms for voice control, object recognition, predictive maintenance, and process optimization, among other things.
All that processing power isn't cool or comfortable in a data center. The CPU must operate reliably 24/7 in the harsh environment of a production line or chemical processing facility.
n The increasing processing demands of single-board computers, coupled with the need for high reliability in harsh environments, pose new challenges to power management. High-performance single-board computers can easily consume 25 W and more. Ambient operating temperatures can reach 85C with little air cooling. The small size requires a multi-layer printed circuit board (PCB) stack, which increases high thermal stress and noise sensitivity. So whatever power solution you choose doesn't make the heat load worse.
Fortunately, semiconductor process and packaging technologies have advanced to meet the power management needs of high-performance industrial single-board computers. If you are designing a power solution for high performance processing applications that operate in harsh environments, you need converters that minimize heat dissipation, radiated noise, and solution size for higher reliability and lower system cost.
2. Power management challenges \n Industrial applications such as factory automation and control, robotics, and motor drives use power supply units (PSUs) that distribute the 24 V bus to power components in systems such as CPU boards. The output of the PSU is between 10 V and 3 V under various operating condition


Selecting Buck Converters and LDOs for Micro Industrial Automation Equipment
Considerations for se1ecting Buck Converters and LDOs for Micro Industrial Automation Equipment
Shipments of devices with sensors, such as field transmitters, machine vision, and position sensors, are increasing as the market for factory automation and control devices grows. As a result, there is a growing demand for feature-rich power integrated circuits (ICs) that can power these devices.
The non-isolated power subsystem (highlighted in red) consists of a low dropout regulator (LDO), a DC/DC converter, or a power module. In this article, I'll show you how to use a buck converter and an LDO for the same purpose.
2. High 1nput voltage, very significant thermal effect
There are many ways to regulate the 1nput DC voltage in factory automation and control equipment. We can use LDOs, DC/DC converters, or power modules. LDOs such as the TPS7A47 are often used in sensor power supplies because of their simple design and ability to attenuate 1nput noise and provide a ripple-free output voltage. DC/DC converters are ideal for applications that operate at lower output voltages, higher 1nput voltages, or higher output currents. For example, the Current Logic DC/DC converter supports a low shutdown current specification of 1 µa and an operating quiescent current specification of 7 µa. For loads with low output currents (less than 20 mA), these performance specifications ensure higher efficiency for 4 to 20 mA loop applications.
Big challenges, small solutions
Most field sensors are small, which limits the size of the printed circuit board (PCB). For example, an ultrasonic sensor with an M12 housing requires a PCB width of less than 9 mm. Integrating power components on a small PCB in a subsystem can be challenging for hardware designers.
Power modules with integrated inductors can solve this challenge because DC/DC converters require us to use additional components, such as inductors, to maintain high frequencies.


Choose the right battery protection and monitoring scheme for our lithium battery-powered system
Choose the right battery protection and monitoring scheme for our lithium battery-powered system
Lithium-ion batteries have high energy density and long cycle life, and they do not have the memory effect of other batteries. These characteristics make them very advantageous for portable electronic systems. But lithium-ion batteries also need to operate within specified limits in order to be used safely, so the batteries need electronics designed to respond or provide a signal to the system when the limits are exceeded.
Battery electronics monitor a variety of conditions, such as voltage, current, and temperature, and how they change over time. They need to sense the desired combination of these parameters to respond, whether it's sending a signal to the system, activating a switch to prevent charging or discharging, or opening a fuse.
The type of battery electronics depends on the type of battery pack. A simple battery pack may require only a simple protector, ranging fr0m a basic overvoltage protector to a more advanced protector that responds to an undervoltage, temperature fault, or current fault. The protector can also be used as an auxiliary device with a monitor or battery gauge.
2. se1ection of battery monitoring and protection scheme
Many advanced battery packs for higher cell count batteries require a battery monitor. The battery monitor measures the voltage, battery current, and temperature of the individual batteries and reports these values to the meter or microcontroller. The system uses this information to adjust performance accordingly; for example, if the temperature is too high, the operating current can be reduced. The battery monitor may provide a battery balancing funct1on to extend battery run time and battery life. The monitor may also include protection available in an integrated circuit (IC), but with greater configurability.
The meter IC integrates the funct1ons of the battery monitor with the controller to provide advanced metering algorithms. The meter IC reports remaining battery capacity, run time, and state of charge. Software-based algorithms can further enhance protection. Meters often include other useful features, such as a black box funct1on to help diagnose failed battery packs in the field, life data logging for minimum and maximum parameter conditions, dynamic charger control, or verification of safe batteries.


When does a single-output regulator has an advantage over a dual-output regulator
When the regulator must operate at high ambient temperatures, such as in an active antenna system, a single-output regulator has an advantage over a dual-output regulator.
For applications with high ambient temperatures, two single-output regulators are better than one because they spread the power consumption across two ICs, whereas a dual-output regulator concentrates the power consumption on a single IC. In the respective evaluation module layouts, R θJA is 29 ° C/W for the single-output regulator and 27 ° C/W for the dual-output regulator. Assuming that the IC heats up only 40 ° C in the application, the estimated power dissipation per output that each output regulator can handle is 1.38 W.
A dual-output regulator, on the other hand, would be limited to 1.48 W – or only 0.74 W per output. This lower maximum power dissipation in the dual output regulator to keep the temperature rise below 40 ° C limits the maximum current that the regulator can support in high ambient temperature applications. The power consumption of a dual output regulator can be reduced by operating at a lower switching frequency. However, the lower switching frequency increases the solution size, thereby negating the main advantage of a dual output regulator, the smaller solution size.
In addition, the pinout of a dual output regulator may end up being less optimized than a single output regulator, given the tradeoffs in pinout when placing two regulators in one IC. As a result, dual output regulators may need to turn on and off the power MOSFETs more slowly to keep the voltage stress within the device rating. Dual output regulators then have more switching losses than single output regulators, resulting in a greater difference in thermal performance. Single-output regulators can have a more optimized pinout to allow the power MOSFETs to turn on and off faster.
The VIN and GND pins on both sides of the TPS543620 package allow us to place a bypass capacitor on each side of the power stage to minimize printed circuit board (PCB) parasitic inductance. Minimizing PCB parasitic inductance minimizes switching node ringing. The TPS543620 also has a large SW pin that allows wider switch node traces to be used on the PCB layout to minimize PCB parasitic resistance. \n The single output regulator is also easier to use in terms of PCB layout by providing more layout optimization options.


When does a single-output regulator has an advantage over a dual-output regulator
When the regulator must operate at high ambient temperatures, such as in an active antenna system, a single-output regulator has an advantage over a dual-output regulator.
For applications with high ambient temperatures, two single-output regulators are better than one because they spread the power consumption across two ICs, whereas a dual-output regulator concentrates the power consumption on a single IC. In the respective evaluation module layouts, R θJA is 29 ° C/W for the single-output regulator and 27 ° C/W for the dual-output regulator. Assuming that the IC heats up only 40 ° C in the application, the estimated power dissipation per output that each output regulator can handle is 1.38 W.
A dual-output regulator, on the other hand, would be limited to 1.48 W – or only 0.74 W per output. This lower maximum power dissipation in the dual output regulator to keep the temperature rise below 40 ° C limits the maximum current that the regulator can support in high ambient temperature applications. The power consumption of a dual output regulator can be reduced by operating at a lower switching frequency. However, the lower switching frequency increases the solution size, thereby negating the main advantage of a dual output regulator, the smaller solution size.
In addition, the pinout of a dual output regulator may end up being less optimized than a single output regulator, given the tradeoffs in pinout when placing two regulators in one IC. As a result, dual output regulators may need to turn on and off the power MOSFETs more slowly to keep the voltage stress within the device rating. Dual output regulators then have more switching losses than single output regulators, resulting in a greater difference in thermal performance. Single-output regulators can have a more optimized pinout to allow the power MOSFETs to turn on and off faster.
The VIN and GND pins on both sides of the TPS543620 package allow us to place a bypass capacitor on each side of the power stage to minimize printed circuit board (PCB) parasitic inductance. Minimizing PCB parasitic inductance minimizes switching node ringing. The TPS543620 also has a large SW pin that allows wider switch node traces to be used on the PCB layout to minimize PCB parasitic resistance. \n The single output regulator is also easier to use in terms of PCB layout by providing more layout optimization options.


When to use single versus dual DCDC buck regulator
There are trade-offs when choosing between a single-output regulator and a dual-output regulator. In this article, I'll use Texas Instruments' (TI) single 6A TPS543620 output DC/DC regulator and dual 6A TPS541620 output DC/DC regulator as examples to discuss the benefits of both and highlight when to use either.
2. When to use a dual output regulator
Dual output regulators offer advantages over single output regulators in many applications. When our design requires the smallest solution size, we might consider using a dual output regulator, for example in a solid state drive. When the point of load, such as a data converter or processing unit, has multiple power rails in parallel, we can also choose a dual-output regulator, which allows us to place the regulator next to the device it is powering with minimal wiring. Finally, a dual-output regulator can provide more flexibility by paralleling two outputs together to power a supply rail that requires twice the current.
Dual output regulators also help reduce solution size. Even though a dual-output regulator has twice the package size of a single-output regulator, component clearance requirements require more area for two single-output regulators. For example, if the design rules require a 1 mm gap around the IC, a 5 mm X 3 mm dual output regulator would take up 24 mm 2, while two 2.5 mm X 3 mm single output regulators would take up 28 mm 2. Those whose designs require more clearance will see the added benefit of a dual output regulator.
Another way to minimize the size of a dual-output regulator solution is to reduce the required 1nput capacitance. When the high-side MOSFET of a typical single-output buck converter turns on, an inrush current is drawn fr0m the 1nput. With a dual-output regulator, the two outputs are switched 180 degrees out of phase, so this 1nput current surge occurs at different times. This can also be achieved with two single-output regulators that support synchronization to an external clock, such as the TPS543620. However, synchronizing two TPS543620 to a 180 degree out of phase clock does require another external circuit to generate the out of phase clock.


Regulated voltage rate is an important index of DC-DC converter
Regulated voltage rate is an important index of regulated power supply, which reflects the corresponding change of output voltage of regulated power supply when the load current changes. When the output current changes fr0m 0 to the rated maximum current, it usually depends on the output voltage and the change in output voltage. Expressed as a percentage value. For example, when the output current of a 5V DC regulated power supply increases fr0m 0 to the maximum current of 1A, its output voltage decreases fr0m 5.00 V to 4.50 V. The voltage drop is 0.5V divided by the nominal output voltage of 5V, which is 10%. This is the power load regulation rate.
The voltage regulation rate is due to a change in the output voltage of the power supply due to fluctuations in the power supply voltage when the power supply is fully loaded. Many people confuse the two adjustment rates.
The ratio of the difference between the no-load voltage of a transformer winding and the voltage of the same winding to the no-load voltage of the winding at a specified load and power factor is called the voltage regulation rate and is usually expressed as a percentage. The voltage regulation rate is related to parameters such as the DC resistance and short-circuit resistance values of the transformer windings. Voltage regulation rate is an important index of transformer, which plays an important role in the design of transformer and can not be omitted.
Voltage regulation rate is an important index to characterize the voltage regulation performance of voltage regulator. It is the relative percentage change in output voltage with respect to the 1nput under constant load and temperature conditions.
The regulation ratio of a transformer is the ratio of the difference between the secondary voltage at no load and the secondary voltage at load to the rated secondary voltage, expressed as a percentage and usually within 5%. In a power system, the measured voltage quality time is the ratio of the no-load voltage at the end of the power line to the difference between the load voltage and the no-load voltage at the end of the power line. In the process of research and design, there must be such problems, which requires our scientific researchers to constantly sum up the experience in the design process in order to promote the continuous innovation of products.


Analysis of the difference between voltage regulation and load regulation
Analysis of the difference between voltage regulation and load regulation
The ratio of the difference between the no-load voltage of a transformer winding and the voltage of the same winding at a specified load and power factor to the full-load voltage of the winding is called the voltage regulation, usually expressed as a percentage. The voltage regulation is related to parameters such as the DC resistance and the short-circuit impedance value of the transformer winding. Voltage regulation rate is an important index of transformer, which plays an important limiting role in the design of transformer and can not be omitted.
Voltage regulation rate is an important index to characterize the voltage regulation performance of voltage regulator. It is the relative percentage change in output voltage with respect to the 1nput under constant load and temperature conditions.
The voltage regulation rate of a transformer means that the primary voltage remains constant (e.g., rated). When a certain load characteristic (power factor) is a certain load current, the percentage formula of the difference between the secondary no-load voltage U1 and the load voltage U2 divided by the no-load voltage U1 is expressed as △ U% = [ ( (U1-U2)/U1] * 100%.
Power regulation (LINE REGULATION, also known as line voltage regulation). Power regulation is defined as the ability of a power supply to provide a stable output voltage when the 1nput voltage varies. This test verifies that the power supply is in a worst-case supply voltage environment, such as the lowest supply voltage at noon in the summer (when power demand is highest due to high temperatures) and the highest supply voltage at night in the winter (when power demand is lowest due to low temperatures). In the above two extreme cases, please confirm whether the stability of the output power of the power supply meets the requirements.
The power regulation rate is usually the percentage of the output voltage deviation rate (deviation) caused by the 1nput voltage change under normal fixed load (nominal load), as shown in the following formula: V0 (Max) -V0 (min)/V0 (normal) The power regulation rate can also be expressed in the following way: When the 1nput voltage changes, The deviation of the output voltage must be within the specified upper and lower limits, that is, within the absolute values of the upper and lower limits. Lower limit. The lower limit of the output voltage.
Voltage regulation rate = (no-load voltage of power supply under rated load-output voltage and power factor)/no-load voltage, usually expressed as a percentage;
Load regulation = (output voltage at rated load-output voltage at half load)/output voltage at rated load, usually expressed as a percentage. \n LOAD REGULATION A change in the load of a power supply will result in a change in the output of the power supply. The load increases and the output decreases.


Solution of DC-DC converter Overheating
1. To rectify the secondary side of the transformer, a more efficient synchronous rectification technique can be se1ected to reduce losses.
2. In order to reduce the conduction loss, the switch tube with low conduction resistance can be se1ected to reduce the conduction loss.
3. Losses in the switching process are caused by the gate charge and the switching time. In order to reduce the loss of the switching process, the equipment with faster switching speed and shorter recovery time can be se1ected.
4. The skin effect should be avoided as much as possible due to the losses caused by high frequency magnetic materials, and can be solved by winding a number of fine enameled wires.
5. It is important to reduce losses by devising better control methods and cushioning techniques. This loss can be greatly reduced, for example, by using soft-switching techniques.
6. Reduce the heat of the power diode. For AC rectifiers and snubber diodes, there will be no better control technique to reduce losses under normal conditions. You can reduce the loss by choosing a high quality diode.
7. Try winding the secondary with a thick wire. Attempt to rewind the tape by the original number of turns using a thick wire.
8. Replace with an iron core transformer with a larger cross-sectional area. Recalculate and debug. In addition, secondary half-wave rectification can be changed to full-bridge rectification to reduce the DC component in the transformer and reduce heat generation. In addition, the fan may be forced to dissipate heat.
A. Try to wrap the secondary with a thick wire. B. Replace with an iron-core transformer with a larger cross-sectional area. Where a is relatively simple, try to rewind the original number of turns with a thick line as long as the window allows, and B requires recalculation and debugging, which is likely to mess up for those who are not good at switching power supplies. In addition, secondary half-wave rectification can be changed to full-bridge rectification to reduce the DC component in the transformer and reduce heat generation. Also, add fans to force cooling.
In the process of research and design, there must be problems of one kind or another, which requires our scientific researchers to constantly sum up experience in the design process, so as to promote the continuous innovation of products.


Overheating of DC-DC converter and Some Common Treatment
Switching power supply transformer used for a long time will appear the phenomenon of heating, then, what is the reason for this phenomenon? In fact, the reason is very simple, because the switching power transformer is a power transformer with switching tubes, in addition to the voltage conversion funct1on of ordinary transformers in the circuit, it also has the funct1ons of insulation and power transmission, which is generally used in switching power supply and other occasions involving high-frequency circuits.
The main heating components in switching power supply are semiconductor switch tube, power diode, high frequency transformer (switching power supply transformer), filter inductor, etc. Different devices have different ways of controlling heat generation. fr0m this point of view, the heating of the switching power supply transformer is caused by the heating of the switching tube, which is caused by the loss. The loss of the switching tube is composed of the switching process loss and the conduction loss.
First of all, fr0m the point of view of the transformer itself, once the temperature rises too high, it is mainly caused by four problems: copper loss, winding process problems, transformer core loss and transformer design power is too small. The no-load heating is caused by the insulation of the transformer or the high 1nput voltage of the transformer. If the insulation is broken, the coil will need to be rewound. If the 1nput voltage is high, the 1nput voltage must be reduced or the number of coil turns must be increased. If the voltage is normal and gets hot when the load is applied, it indicates that the power transformer is overloaded and its load design needs to be changed.
Semiconductors, power diodes, etc. Are components that are prone to generate heat during use, and switching power supplies are no exception. The main heating components of switching power supply are semiconductor switch tube, power diode, high frequency transformer and filter inductor. Different devices have different ways of controlling heat generation. Power transistor is one of the devices that generate a lot of heat in high frequency switching power supply. Reducing its heat can not only improve the reliability of power transistors, but also improve the reliability of switching power supply and increase the mean time between failures.
In the design process of switching power supply transformer, the heating of MOS tube is the most serious, and its excessive temperature rise is caused by loss. The loss of MOS transistor is composed of switching loss and conduction loss. In order to reduce the conduction loss, the switch tube with low on-resistance can be se1ected to reduce the conduction loss. Losses in the switching process are caused by the gate charge and the switching time. Yes, in order to reduce the loss of the switching process, it can be reduced by choosing equipment with faster switching speed and shorter recovery time.


The difference between the switching power supply and the transformer
The difference between the switching power supply and the transformer is that the switching power supply can stably convert the voltage within a certain range into a very accurate low voltage or high voltage (for example, 110V-250 1nput, the output voltage can be stably controlled at the required voltage with a positive or negative difference of 0.5v)! The output voltage of the transformer is constantly changing with the 1nput voltage, that is, the output voltage increases when the 1nput voltage increases, and the output voltage decreases when the 1nput voltage decreases. Because the switching power supply converts the alternating current into the direct current firstly, the direct current is converted into the alternating current with higher frequency through the power switch tube, and the voltage conversion is carried out through the high-frequency transformer, not only the efficiency is improved, but also the volume is greatly reduced after the frequency is increased, and the copper and iron loss is also saved. Because it is controlled by the power switch tube, the switch tube has a short conduction time when the current is small, and the output voltage can be maintained.
Switching power supply is a kind of power supply which uses modern power electronics technology to control the time ratio of switching on and off to maintain a stable output voltage. Switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. With the development and innovation of power electronics technology, the technology of switching power supply is constantly innovating. At present, switching power supply is widely used in almost all electronic devices because of its small size, light weight and high efficiency, and it is an indispensable power supply mode for the rapid development of electronic information industry.
A transformer is a device that transforms voltage, current, and impedance based on the principle of electromagnetic induction. The primary of a transformer shall be used in an alternating current circuit. Switching power supply is a kind of power supply which uses modern power electronics technology to control the time ratio of switching transistor on and off to maintain a stable output voltage. Switching power supply can be divided into AC/DC and DC/DC two categories. According to the 1nput and output electrical isolation, it can be divided into two categories: one is called isolated DC/DC converter; The other is not isolated and is called a non-isolated DC/DC converter.


The principle of switching power supply
The principle of switching power supply is to convert power frequency AC into DC, and then convert DC into high frequency AC, through switching transformer, feedback voltage stabilization and other processes into the voltage you need, through rectification, filtering, and then into the process of DC, and MOSFET in the whole process through its continuous on and off, so that high voltage DC into high frequency AC process.
Because the voltage control of the switching power supply is achieved by adjusting the turn-on time or frequency of the power semiconductor device in the saturation region, there is no iron loss and copper loss, the loss of components can be ignored, and the efficiency is higher than that of a transformer; Because it only has components and circuit boards, it will be very small and light. The switching power supply is small in size, the power is related to the iron-core transformer and the control mode, the electromagnetic interference is large, and the ripple coefficient is large. Especially in the field of audio and video, it is very sensitive to electromagnetic interference. In sound, it is not pure and may have a silky sound. In video tables, it is very sensitive to electromagnetic interference.
Transformer is a kind of electrical equipment used for electric energy conversion, which is an essential and important device in the power grid. It can convert AC electric energy of one voltage and current into AC electric energy of another voltage and current with the same frequency. Transformer is used in almost all electronic products. Its principle is simple, but according to different use occasions (different uses), the winding process of the transformer will have different requirements. The main funct1ons of the transformer are: voltage conversion; Impedance transformation; Isolation, voltage regulation (magnetic saturation transformer), etc. The common core shapes of transformers are generally E-type and C-type cores.
Because the transformer is a kind of "electromagnetic-electric" conversion process, the existence of iron loss and copper loss is unavoidable. Linear looks heavy, the power depends entirely on the transformer and the regulator tube, although the efficiency is low, it will not introduce additional interference, that is to say, the electromagnetic interference is small, and the ripple coefficient is very low and can be ignored. For monitoring, there is no better advantage than this, and the quality of the image is closely related to the power supply. Especially for analog signals with small amplitude (audio source and video source, etc.), the requirements for power supply are very high, so some fever audio power supplies use transformers instead of switching power supplies. Since the structure of the transformer is two coils and an iron core, the voltage added across the coils does not change abruptly. It has a strong resistance to instantaneous high pressure.


Current Logic Meet Your
Recently, Current Logic received a large number of orders for "chassis switching power supply" fr0m overseas. After receiving the demand, the staff immediately responded and deployed to transport the goods to overseas quickly and safely.
Worry about customers' worries and take customers' requirements as our own responsibility
Affected by the epidemic, the global electronics industry structure and supply chain are facing a huge test, and the shortage of production capacity in the semiconductor industry is becoming more and more serious. In this case, strong and fast product delivery capability has become one of the core competitiveness of domestic and foreign power supply enterprises. At the same time, rapid expansion of production capacity and improvement of production efficiency have become an important way for power supply enterprises to participate in future competition.
In this case, Current Logic is fully prepared to ensure that products are delivered on time, in accordance with quality and quantity, adhering to the concept of high efficiency, high quality and high quantity. This rapid overseas shipment is the embodiment of Current Logic's strong delivery capability and emergency deployment capability.
Increased productivity and high degree of automation \n Faced with the massive demand for power supply during the epidemic period, Current Logic has already made corresponding arrangements to further expand the existing production area of 60000 square meters. It plans to start the construction of the fifth phase of the plant and increase the manpower of the production department to ensure the stable and high-speed operation of the production line. In addition, Current Logic insists on investing in automated production equipment to improve the automation rate of production. Up to now, Current Logic has established 20 + chip lines, with an overall automation level of more than 60%, and the automation level of some product lines can even be as high as 85%, with a production capacity of 121KK/year. Automatic production is smooth and quality control is excellent.


Insulation penetration distance
Insulation penetration distance:
The following regulations shall be complied with according to the working voltage and insulation application:
— — No thickness requirement for working voltage not exceeding 50 V (71 V AC peak or DC value);
— — The minimum thickness of additional insulation shall be 0.4mm;
— — The minimum thickness of reinforced insulation shall be 0.4 mm when it is not subjected to any mechanical stress that may cause deformation or degradation of the insulation material at normal temperatures.
The above requirement does not apply to a thin layer of insulating material, regardless of its thickness, if the insulation provided is used within the protective enclosure of the equipment and is not subject to knocks or bruises when maintained by the operator, and is either:;
— — For additional insulation, at least two layers of material shall be used, and each layer of material shall be able to pass the electric strength test for additional insulation;
— — Additional insulation composed of three layers of materials, in which the combination of any two layers of materials can pass the electric strength test of additional insulation;
— — For reinforced insulation, at least two layers of materials shall be used, each of which can pass the electric strength test for reinforced insulation;
— — Reinforced insulation consisting of three layers of insulating material, in which the combination of any two layers of material can pass the electric strength test of reinforced insulation.
Precautions for wiring process:
For example, flat components such as capacitors must be pasted flat without dispensing. If the distance between two conductors can be shortened by applying a force of 10 N and is less than the distance required by safety regulations, the part can be fixed by dispensing to ensure its electrical clearance.
When laying PVC film in some shell equipment, attention should be paid to ensuring the safety distance (pay attention to the processing technology). Pay attention not to make foreign bodies such as glue silk on the PCB board.
Insulation damage shall not be caused when parts are machined.
6. Requirements for flame-proof materials:
Heat shrinkable sleeve V-1 or VTM-2 or above; PVC sleeve V-1 or VTM-2 or above
Teflon sleeve V-1 or VTM-2 or above; plastic material such as silicone sheet, insulating tape V-1 or VTM-2 or above
PCB board 94V — 1 and above
About insulation level
(1) Working insulation: insulation required for normal operation of equipment
(2) Basic insulation: insulation providing basic protection against electric shock
(3) Additional insulation: Independent insulation applied in addition to the basic insulation to protect against electric shock in case of failure of the basic insulation.
(4) Double insulation: consisting of basic insulation and additional insulation


DC-DC converter
Determination of electrical clearance:
The distance is determined based on the measured operating voltage and insulation class
Refer to Table 3 and Table 4 for the electrical clearance dimension requirements of the primary side circuit
The electrical clearance size requirements for the secondary side circuit are generally as follows: for the AC part of the primary side: L — N ≥ 2.5mm in front of the fuse, L. N PE (ground) ≥ 2.5mm, there is no requirement behind the fuse device, but a certain distance should be kept as far as possible to avoid short circuit damage to the power supply.
AC to DC part of primary side ≥ 2.0mm \n Primary side DC grounding to earth ≥ 2.5mm (primary side floating grounding to earth)
Primary side part to secondary side part ≥ 4.0 mm, components bridged between primary and secondary sides
The electric gap of the secondary side is not less than 0.5mm.
Secondary side ground to earth ≥ 1.0mm \n Note: Before determining whether the requirements are met, the internal parts shall be applied with a force of 10N and the outer shell shall be applied with a force of 30N to reduce the distance, so that the space distance can still meet the requirements in the worst case.
III. Determination of creepage distance:
In general:
(1) AC part of primary side: L — N ≥ 2.5mm in front of the fuse, and ≥ 2.5mm L. N the ground. It is not required after the fuse, but a certain distance shall be kept as far as possible to avoid short circuit damage to the power supply.
(2) AC to DC part of primary side ≥ 2.0mm
(3) Primary side DC ground to ground ≥ 4.0mm, such as primary side ground to ground
(4) Primary side to secondary side ≥ 6.4mm, for example, the pin spacing of optocoupler, Y capacitor and other component parts ≤ 6.4mm shall be grooved.
(5) The distance between the secondary side parts ≥ 0.5mm
(6) Secondary side ground to earth ≥ 2.0mm
(7) Between two stages of transformer ≥ 8.0mm or above \n


Electrical isolation distance inside the transformer
Electrical isolation distance inside the transformer:
The electrical isolation distance inside the transformer refers to the sum of the widths of the retaining walls on both sides of the transformer. If the width of the retaining wall on the transformer is 3mm, then the electrical isolation distance of the transformer is 6mm (the width of the retaining walls on both sides is the same). If the transformer has no retaining wall, the isolation distance of the transformer is equal to the thickness of the gummed paper used. In addition, for AC-DC power supply, the primary and secondary windings of the transformer shall be isolated with three layers of gummed paper, while for DC-DC power supply, only two layers of gummed paper can be used for isolation.
Creepage distance: that short straight-line distance measured via air separation between two conductive component or between a conductive component and an object interface;
Clearance: The shortest distance between two conductive components or between a conductive component and an object measured along an insulating surface.
When the clearance does not meet the standard requirements: the PCB can be grooved between two conductive components, and the conductive components can be wrapped with insulating materials if the distance between the conductive components and the shell and accessible parts is not enough.
The conductive components are wrapped with insulating materials to solve the problems of Creepage distance and clearance. This method is generally used to wrap the transformer when the distance between the transformer and the peripheral components on the power board is not enough.
In addition, the voltage difference between the two conductors can be properly reduced without affecting the funct1on of the product.


Creepage Distance and Clearance of Switching Power Supply
(1) Creepage distance: the shortest path between two conductive parts or between a conductive part and a protected interface of equipment measured along an insulating surface.
(2) Electrical clearance: the shortest spatial distance measured between two conductive parts or between a conductive part and an equipment protection interface. That is to say, under the condition of ensuring the stability and safety of electrical performance, the shortest distance of insulation can be achieved through air.
Generally speaking, the required value of creepage distance is larger than the required value of electrical clearance, and both requirements must be met during wiring (that is, the distance between the surface and the space should be considered). Slotting (the width of the slot should be greater than 1mm) can only increase the surface distance, that is, creepage distance, but not the electrical clearance. Therefore, when the electrical clearance is not enough, Slotting can not solve this problem. When slotting, pay attention to whether the position and length of the slot are appropriate to meet the requirements of creepage distance.
(3) Electrical isolation distance of components and PCB: (electrical isolation distance refers to the comprehensive consideration of electrical clearance and creepage distance) for switching power supply of Class I equipment (● Class I equipment: equipment protected against electric shock by basic insulation and protective grounding. (Switching power supplies with grounded enclosures are such equipment); ● Class II equipment: equipment that is protected against electric shock by means other than basic insulation (such as double insulation or reinforced insulation); ● Class III equipment: equipment that does not pose a risk of electric shock), isolation distances on components and PCBs


DC/DC converters' two types: Hard Switching and Soft Switching
According to the switching conditions of the switches, DC/DC converters can be divided into two types: Hard Switching and Soft Switching.
The switching device of the hard switching DC/DC converter turns on or off the circuit under the condition of bearing voltage or flowing current, so a large crossover loss will be generated in the process of turning on or off, that is, the so-called Switching loss. When the working state of the converter is certain, the switching loss is also certain, and the higher the switching frequency is, the greater the switching loss is. At the same time, the oscillation of the distributed inductance and parasitic capacitance of the circuit will be excited in the switching process, which will bring additional loss. Therefore, the switching frequency of the hard-switching DC/DC converter should not be too high. When The switch tube of the soft switching DC/DC converter is switched on or off, either the voltage applied to the switch tube is zero, i.e. Zero-voltage-switching (ZVS), or the current passing through the switch tube is zero, i.e. Zero-current-switching (ZCS). ZCS）。 This soft-switching mode can significantly reduce the switching loss and the oscillation in the switching process so that the switching frequency can be greatly increased. It creates conditions for the miniaturization and modularization of the converter.
Power MOSFET is one of the most widely used switching devices. It has a high switching speed, but it also has a large parasitic capacitance. When it is turned off, its parasitic capacitance is fully charged under the action of external voltage. If this part of charge is not discharged before it is turned on, it will be consumed inside the device, which is the capacitive turn-on loss. In order to reduce or eliminate this loss, the power FET should be turned on at zero voltage (Zvs). Insulated Gate Bipolar Transistor (IGBT) is a kind of compound switching device. The current tail at turn-off will cause large turn-off loss. If the current flowing through IGBT is reduced to zero before turn-off, the switching loss can be significantly reduced. Therefore, zero current switching (ZCS) should be adopted for IGBT. When IGBT is turned off at zero voltage, the turn-off loss can also be reduced, but when MOSFET is turned on at zero current, the capacitive turn-on loss can not be reduced.


Different Non-isolated DC-DC converter
According to the number of active power devices, non-isolated DC/DC converters can be divided into three categories: single-transistor, double-transistor and four-transistor.
There are six types of single-transistor DC/DC converters, namely Buck DC/DC converters. Boost DC/DC converters, Buck Boost DC/DC converters, Cuk DC/DC converter, Zeta DC/DC-converter, and SEPIC DC/DC-converter. Among the six single-transistor DC/DC converters, the Buck and Boost DC/DC converters are basic, and the Buck-Boost, Cuk, Zeta, and SEPIC converters are derived fr0m them. The two-transistor DC/DC converter is a buck-boost DC/DC converter with two transistors connected in series. Full-bridge DC/DC converters are commonly used in four-transistor DC/DC converters.
When the isolated DC/DC converter is used to realize the electrical isolation between the output and the 1nput, it is usually realized by a transformer. Because the transformer has the funct1on of voltage transformation, it is beneficial to expand the output application range of the converter, and it is also convenient to realize multiple outputs of different voltages or multiple outputs of the same voltage.
When the voltage and current ratings of the power switches are the same, the output power of the converter is generally proportional to the number of switches used. Therefore, the more the number of switches, the greater the output power of the DC/DC converter. The output power of a four-tube converter is twice as large as that of a two-tube converter, and the output power of a single-tube converter is only 1/4 of that of a four-tube converter.
The combination of a non-isolated converter and an isolated converter provides features that are not available in a single converter.
According to the transmission of energy, there are two kinds of DC/DC converters: unidirectional transmission and bidirectional transmission. A DC/DC converter having a bidirectional transmission funct1on can transmit power fr0m a power source side to a load side, and can also transmit power fr0m the load side to the power source side.
DC/DC converters can also be classified as self-excited and separately controlled. The converter that realizes self-sustaining periodic switching by means of the positive feedback signal of the converter itself is called self-excited converter, such as Royer converter, which is a typical push-pull self-excited converter. The control signal of the switching device in the separately controlled DC/DC converter is generated by an external special control circuit.


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