This time we will focus on the chassis switching power supply.

The application field of chassis power supply is very wide, and different application environments will also have special effects on products.

Therefore, there will be some problems in use, such as abnormal start-up output, large output ripple noise, isolation and withstand voltage problems or howling problems, etc.

For these possible power supply application problems, how to troubleshoot and Solve the corresponding fault. This article will mainly analyze several common power supply startup failures for the chassis switching power supply.

No output when the product is powered on

In daily use, due to the complex application environment, component damage, etc., it may cause the power supply to have no output after power-on, which will make the post-stage circuit unable to work normally.

So what are the reasons usually caused?

● There is a lightning strike, surge or voltage spike at the input end

Troubleshooting plan: You can check whether the input front-end fuse, rectifier bridge, plug-in resistor and other components of the product are damaged, and use the differential test to analyze the power-on waveform.

It is recommended to use it in an environment that meets the EMS conditions of the technical manual. If it needs to be used in a harsher environment, an EMC filter and anti-surge device should be added to the front end of the product.

● The input voltage far exceeds the maximum specification value of the product

Troubleshooting plan: Check whether the fuses, plug-in resistors, large capacitors and other devices at the input end of the product are in good condition, and test the input voltage waveform to judge.

It is recommended to adjust the input voltage, use a power supply with a suitable voltage as the input, or replace it with a product with a higher input.

● There are sundries such as water droplets or tin dross adhering to the product, resulting in an internal short circuit

Troubleshooting plan: Check whether the ambient humidity is within the specifications, and then disassemble the product to check whether there is debris on the surface of the patch and whether the bottom surface is clean.

It is recommended to ensure that the test (use) environment is clean, the temperature and humidity are within the specification range, and the product is painted with conformal paint if necessary.

● The input line is broken or the connection line port is not in good contact

Troubleshooting plan: Test whether the input voltage is normal from the input terminal on the bottom of the product.

It is recommended to replace the intact cable, and the cable port is snapped tightly to avoid poor contact.

Long start-up delay

In product applications, the normal connection has a startup delay.

The main reasons may be:

● Low bus voltage leads to low starting current and slow internal charging of the product

Troubleshooting plan: Use a multimeter to detect the input bus voltage to confirm whether the input voltage is within the rated range of the product, and compare it with the input voltage range marked on the product label to check whether it is within the specification range.

It is recommended to use our products with a wider input voltage range if it is used beyond the specifications.

Start with no output/output abnormal (hiccup/jump)

Everything is ready, but it is found that there is no output or hiccups and jumps when it is officially started. It may be caused by external environmental interference or damage to external components.

The main reasons are as follows:

● The output load

The output load is too heavy or the short-circuit/capacitive load exceeds the specification value, resulting in overcurrent at startup.

Troubleshooting plan: disconnect the load no-load test, confirm whether the output is normal, confirm whether there is a capacitive load exceeding the specification at the back end of the power supply, and check whether the back end of the power supply is connected to a load (such as a motor) that requires high power at the moment of a startup.

It is recommended to reduce the load, use it within the load range specified in the technical manual, or replace the product with a higher power, and recommend the product with stronger capacitive load capacity;

it is recommended that the customer change the driving method of the back-end load, and do not use the direct drive of the power supply product.

● Large external interference at the moment of a startup

when the power supply product and high-power equipment are in the same system, the high-power device may pull down the voltage of the power supply line at the moment of a startup, affecting the power supply startup.

And at the same time, the working process may continue to interfere with the power supply line, thereby affecting the power supply.

Troubleshooting plan: Disconnect the large equipment and test the power module separately.

It is recommended to isolate the power supply product from the power supply network of large equipment as much as possible to avoid starting at the same time.

● The ambient temperature is too low

The capacitance of the electrolytic capacitor will become smaller, and the ESR will be too large, resulting in a poor startup.

Troubleshooting plan: Confirm that the ambient temperature is within the working temperature range of the product, and confirm that the power supply load is properly derated under low-temperature conditions.

It is recommended to derate according to the derating curve in the case of low temperature, and it is recommended to choose a power supply product with higher output power to meet the low-temperature demand.

● TVS tube specification

The output external protection TVS tube specification (far) is smaller than the output voltage of the product, the output external TVS tube is reversely connected, and the capacitor is damaged.

Troubleshooting plan: After removing the TVS, test the output voltage of the power supply product. TVS specification selection is generally 1.2 times the output voltage, and generally can be omitted without special requirements.

There are many kinds of power module failure problems. This article briefly explains the above common problems of chassis power startup failure. For more questions, welcome to mail us