How to locate and troubleshoot power module failures (on)

Power modules have been widely used in industrial communications, medical, power and other fields due to their modular design and high reliability. During the application process, some faults may be encountered, which may cause the system to fail to start, and then burn the circuit. So how to quickly locate and solve these faults?

Power modules function to power microcontrollers, integrated circuits, digital signal processors, analog circuits, and other digital or analog loads. Although the reliability of the power module is relatively high, it may also be faulty during the use process. The main causes of the fault are divided into two categories: parameter abnormality and abnormal use. The following will analyze the more common power module parameter abnormal fault problems and provide corresponding solutions. Some of these failures you may have encountered.

First, the input voltage is too high

The input parameter for the power module is abnormal - the input voltage is too high. This is extremely light, which causes the system to fail to work properly and burns the circuit. So what is the cause of the input voltage being too high?

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.

For this type of problem, you can adjust the load at the output or adjust the input voltage range as follows:

Ensure that the output 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;

Replace a reasonable range of input voltage. When there is interference voltage, consider the TVS tube or regulator tube at the input end.

Second, the output voltage is too low

Abnormal output parameter for power module - output voltage is too low. This may cause the overall system to not work properly. For example, in a microcontroller system, the load suddenly increases, which will lower the power supply voltage of the microcontroller and cause a reset. And the power supply will work for a long time at low input voltage, the life of the circuit will also be greatly damaged. Therefore, the problem of low output voltage can not be ignored, so the output voltage is too low is usually caused by those reasons?

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.

For this type of problem, it can be improved by adjusting the power supply or replacing the corresponding peripheral circuit, as shown below:

Increase the voltage or switch to a higher power input power supply;

Adjust the wiring, increase the cross-sectional area of ​​the wire or shorten the length of the wire, and reduce the internal resistance;

Switch to a diode with a small conduction voltage drop;

Reduce the filter inductance value or reduce the internal resistance of the inductor.

Third, the output noise is too large

Abnormal output parameter for power module - output ripple noise is too large. As we all know, noise is a key indicator to measure the advantages and disadvantages of power modules. In the application circuit, the design layout of the module will also affect the output noise. What is the cause of excessive output ripple noise?

The power module is too close to the main circuit noise sensitive component;

The decoupling capacitor is not connected to the power input of the main circuit noise sensitive component;

Differential frequency interference between power modules of single output in a multi-channel system;

The ground wire treatment is unreasonable.

The ZDS2024 oscilloscope tests power modules with large noise interference problems, as shown:

For this type of problem, it can be improved by isolating the module from the noise device or using a decoupling capacitor in the main circuit, as follows:

Keep the power module as far as possible from the main circuit noise sensitive component or module and the main circuit noise sensitive component;

A 0.1μF decoupling capacitor is connected to the power input of the main circuit noise sensitive component (such as A/D, D/A or MCU);

Eliminate difference frequency interference by using a multi-output power module instead of multiple single output modules;

Use a remote grounding point to reduce the ground loop area.

Fourth, the power supply pressure is not good

Abnormal performance parameters for the power supply module - the power module has a low withstand voltage. Usually, the isolated power module has a withstand voltage of several thousand volts, but it may not be able to reach this indicator during application or testing. Which factors will greatly reduce its withstand voltage?

The withstand voltage tester has a boot overshoot;

The isolation voltage value of the selected module is not enough;

Reflow soldering and hot air guns are used many times during maintenance.

The method of testing the isolation voltage of the power module with a voltage tester is as follows:

For this type of problem, there are two improvements through specification testing and specification use, as follows:

The voltage is gradually increased during the withstand voltage test;

Select a power module with a high withstand voltage;

When soldering the power module, select the appropriate temperature to avoid repeated soldering and damage the power module.

Fifth, select high-quality isolated power modules to reduce the design risk of the circuit

ZLG Zhiyuan Electronics independently develops and produces isolated power modules with wide input voltage range, isolated 1000VDC, 1500VDC, 3000VDC series, various package types, compatible with international standard SIP, DIP and other packages. At the same time, ZLG Zhiyuan Electronics can provide users with professional power supply peripheral application circuit design experience reference based on rich power supply design and application experience to improve product reliability.

ZLG Zhiyuan electronic power module is widely used in power supply and industrial power because it has high efficiency, wide input voltage range, small size, high reliability, good impact resistance, good isolation and wide temperature range. Automation, communications, medical, transportation, building automation, instrumentation and automotive electronics.