Analysis of Common Faults of DC-DC Power Modules

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Analysis of Common Faults of DC-DC Power Modules [Copy link]

Although the reliability of power modules is relatively high, they may also fail. In DC-DC modules, the following types of failures may occur:
1. The output voltage of the module decreases during use;
2. The module stops working;
3. The output voltage of the module is too high;
4. The input of the module is short-circuited;
5. The output current of the module is too large.
The first two types of failures generally do not bring great danger, and can be detected and alarmed by the fault diagnosis circuit.
The third failure mode is more dangerous. It can burn the application circuit. Generally, overvoltage protection is achieved through an overvoltage protection circuit. In addition, it can also be achieved by adding a voltage regulator diode at the output end. When designing, the parameters of the diode should be reasonably selected to prevent the change of the voltage regulation point due to different temperatures. Some modules have their own overvoltage protection. Generally speaking, modules below 25W have no overvoltage protection function, and modules above 25W are designed with overvoltage protection circuits. The overvoltage protection point is generally designed to be 135%--145% of the rated voltage. When designing in detail, it is necessary to confirm whether the module has these functions to avoid repeated design.
The fourth type will cause input overcurrent, which will burn the printed circuit board in severe cases. Generally, it can be protected by selecting a suitable fuse at the input end. When wiring, the fuse is usually placed near the input end of the power module. The purpose of this design is to reduce the lead inductance of the input line to avoid overvoltage at the input end caused by the lead inductance when the fuse blows.
The fifth fault can be solved by selecting a power module with overcurrent protection. Generally, power modules have overcurrent protection function. This module can achieve this by detecting the primary or secondary current of the converter, but it will lose a certain efficiency. When selecting a voltage module, the larger the power rating, the better. If the derating is too large, when the user board is short-circuited, due to the existence of transmission voltage drop, the output current is not enough to achieve module overcurrent, which may cause chip overheating or even damage.