How to debug power module failure
2022-08-08

Because the module power supply is easy to install and has many structural advantages, the design related to the module power supply often appears in the field of mobile communication and switching equipment. It can be seen that the module power supply is widely used. The DC-DC power module has high reliability, but will not be damaged.

Power module

Several common faults of the DC-DC power supply module reflect that the output voltage of the module drops, the module stops working, the output voltage of the module is too high, the input of the module is short circuited, and the output current of the module is too large.

From the risk level, the risk of output voltage drop and module stop is relatively low, which can facilitate circuit diagnosis. The latter three issues are more risky.

When the input of the module is short circuited, the printing plate will be burned. This serious failure can be prevented by placing a fuse tube at the input end. Generally, the fuse tube shall be placed near the input end of the power module. The purpose of the planning is to reduce the wire inductance of the input line and avoid the overvoltage at the input end caused by the wire inductance when the fuse is blown. When the output voltage of the module is too high, the incineration circuit of the DC-DC power module may be a more dangerous fault. Generally, the maintenance is carried out through the pressure maintenance circuit, and others can also be realized by adding a zener diode at the output end. In the planning, the parameters of the diode shall be reasonably selected to prevent the change of the constant voltage point under different temperatures. Some modules have their own overvoltage maintenance. Generally speaking, modules below 25W have no overvoltage maintenance function, and the internal planning of modules above 25W includes overvoltage maintenance circuit. The overvoltage maintenance point is generally planned to be 135% - 145% of the additional voltage. In the specific planning, find out whether the module has these functions to avoid repeated planning.

If the output current of the DC-DC power module is too large, it is necessary to select a power module with overcurrent maintenance function for planning. The general power module has the overcurrent maintenance function, which can be realized by detecting the current at the primary side or the secondary side of the converter, but it must lose a certain power. When selecting a voltage module, the greater the power, the better. If the drop is too large, the output current is insufficient to realize the module overcurrent due to the transmission voltage drop during the auxiliary short circuit of the subscriber board, which may cause the chip to overheat or even damage.