The engineer teaches you to easily solve the eight major faults common in power modules.
Single-chip reset, computer crash, mobile phone blue screen and other common phenomena in life, in fact, and the power supply of the power module is also inextricably linked, for the power supply failure phenomenon, how to locate the problem? Here will be announced for everyone.
At present, there are many types of power modules on the market, and the input voltage, output power, function and topology of different products are different, and can be used for microcontrollers, integrated circuits, digital signal processors, analog circuits, and others. Digital or analog load supply. The reliability of the power module is relatively high, but it may also be faulty. The following is a common fault of the DC-DC using ZLG Zhiyuan Electronics as an example.
First, the output voltage is low
If the input voltage of the circuit is too low, the circuit will be abnormal. For example, in the microcontroller system, the load suddenly increases, which will lower the power supply voltage of the microcontroller and cause a reset. When the power supply is operated for a long time at a low input voltage, the life of the circuit will also have a great influence. What are the reasons why the output voltage is too low?
Low input voltage or insufficient power;
The output line is too long or too thin, causing excessive line loss;
The anti-reverse diode of the input terminal has a large voltage drop;
The input filter inductance is too large.
figure 1
Solution:
1) Increase the voltage or switch to a higher power input power supply;
2) Adjust the wiring, increase the cross-sectional area of ​​the wire or shorten the length of the wire, and reduce the internal resistance;
3) Switch to a diode with a small conduction voltage drop;
4) Reduce the filter inductance value or reduce the internal resistance of the inductor.
Second, the input voltage is too high
If the input voltage is too high, it is very easy to burn the circuit, which brings great harm. What common causes are likely to cause high voltage?
The output is suspended or unloaded;
The output is lightly loaded and lighter than the 10% rated load;
The input voltage is high or the interference voltage.
Solution:
1) Ensure that the output end is not less than 10% of the rated load. If there is no load in the actual circuit operation, connect a dummy load with a rated power of 10% at the output end;
2) Replace a reasonable range of input voltage. When there is interference voltage, consider the TVS tube or the voltage regulator at the input end.
Third, the module is hot
The power module has energy loss during the voltage conversion process. The heat generated by the module causes the module to heat up, reduces the conversion efficiency of the power supply, and affects the normal operation of the power module. However, under what circumstances will the power module heat up more seriously?
Using a linear power module;
Overloaded load;
The load is too small: the load power is less than 10% of the module's power output power, which may cause the module to heat up (the efficiency is too low);
The ambient temperature is too high or the heat is not good.
The heating power module observed by the thermal imager is shown in Figure 2:
figure 2
Solution:
1) Add a heat sink when using a linear power supply;
2) Increase the load of the power module to ensure a rated load of not less than 10%;
3) Reduce the ambient temperature and keep the heat dissipation good.
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