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Miniature Power Supply Application

Serial communication bus transmit data through physical network such as the RS-232, RS-485 and Controller Area Network (CAN) . The applications cover industrial process control, power supply regulation (regulators), as well as point-to-point communications between computers.

These interconnected systems are equipped with their own power supply, and the distance between the systems are often far away. For this reason, we often need to take electrical isolation measures to ensure the physical security of the system, and the need to cut off the ground loop to protect system from high voltage surge impact and reduce signal distortion.

Isolation can protect the system from surge or high voltage and high current damage caused by ground loop, which is most likely to occur when there are a number of ground access in the system . The system is connected by a long cable, and their potential to may not be the same, so current will occur between the two systems. If not isolated, this current will cause noise in the system to reduce the measurement accuracy and even destroy system components.

In industrial environment, the motor start-up and shut down, electrostatic discharge or lightning strikes will generate current through the inductive coupling in the long-distance cables, causing potential rapid change. Such changes can be up to hundreds of kilovolts. If there is no isolation measures taken, the signal or even the system will be damaged. If all the devices connected to bus share the same reference ground, then the system will be free from the impact of this destructive energy, and the isolation between devices can prevent ground loops and the occurrence of surge.

CAN bus typically uses a working voltage of 3V or 5V. In certain areas of industrial control, due to the complexity of the situation, there is high common-mode voltage between each node. Although the CAN bus has a certain anti-interference ability of common interference. However, when the common-mode voltage is higher than the threshold voltage of the receiver, the receiver can not work on, or even chips and equipments will be burned.

In order to achieve complete isolation of systems, all signal lines and power supplies must be isolated. Using isolated DC / DC converter can provide power supply isolation.


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