Causes of noise in inverter power supply

Many people think that the noise of inverter power supply is due to equipment failure, and blind inspection and replacement cause a lot of waste. Our inspection should also be correct, find the problem, and then solve it to prevent it from happening again.

1. Due to external interference, after carrying some load, the filtering parameters change and the filtering effect is significantly reduced.

2. When the two arms at one end of the output block resistance asymmetry, the level of common mode noise is inconsistent, and the difference between the two becomes different noise.

3. Part of the load includes the load of the switching power supply, which can transmit the noise of the ad switch to its input end, that is, the output end of the SPWM power inverter.

4. The reason why the input end noise is coupled to the output line is that the input and output lines are laid in parallel and the interval is small. In particular, the large capacity boost type input current is large and the noise coupling is serious.

5. The transmitted filter adopts the method of single arm series inductance, and the inductance of single arm series is input, so that the resistance of the two arm tissues is uneven, and some rectifying loads alleviate the impact current when connected.

6. When the grounding wires of the common mode filter circuit at the input and output ends are connected to the same point, the ground circulation is formed. The common mode noise at the input end is connected to the output end through the grounding wire of the common mode filter circuit at the output end, and the first level EMI filter has no effect.