How to solve the interference of switching power supply

With the development of power technology, the control of high-frequency switching power supply has gradually developed from the original analog circuit to the highly integrated control devices such as microprocessors and DSP. These devices are small in size and high in precision, but the electromagnetic interference and radiation in the switching power supply are stronger than other communication equipment working environment, which puts forward higher requirements for the auxiliary power supply.

In the current intelligent switching power supply, there are internal microprocessors or DSP for monitoring and communication. Microprocessor chip requires high power supply, stable amplitude, and no large spike and burr, which may cause electromagnetic interference. Moreover, the AC adaptability of auxiliary power supply is required to be wider than the normal working range of rectifier. When the rectifier is connected to the AC input power, the monitoring part must work normally first, carry out self inspection and various conditions detection to determine whether the rectifier can be started; In case of extremely high or low AC voltage, although the rectifier has stopped working, the monitoring part should still work normally to maintain normal monitoring and communication.

Some power supply products have been reset for no reason during operation. When designing the auxiliary power supply of high-power switching power supply, we analyzed it and found that its auxiliary power supply has many problems under different AC input voltage and load conditions: narrow AC adaptive range, low load capacity, unstable and extremely asymmetric working waveform, magnetic bias, extremely serious electromagnetic interference, etc.

The working principle of the general switching power rectifier auxiliary power supply is: the input AC is converted into high-voltage DC through rectification, and then into low-voltage high-frequency square wave through the conversion circuit, and then becomes the stable low-voltage DC required by the system through the rectification and filtering circuit. Generally, the voltage is stabilized by a three terminal voltage regulator, and the voltage feedback signal of the high-frequency conversion drive pulse control loop is provided by a DC output.