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Interference Problems of High-frequency Switching Power Transformers and Analysis of Solutions
Feb 23, 2018

Interference Problems of High-frequency Switching Power Transformers and Analysis of Solutions

What are the interference problems and solutions to high-frequency switching power transformers? In the current switching power supply transformers, organic microprocessors or DSPs are used for internal monitoring and communication. Microprocessor chips have high requirements for power supply, require stable amplitude, and can't have large spikes to avoid electromagnetic interference. Moreover, the AC adaptability of the auxiliary power supply is required to be wider than the normal working range of the rectifier. When the rectifier is connected to the AC input power, it must be the normal operation of the monitoring part to conduct self-test and various conditions to determine whether the rectifier can be turned on; in case of extremely high or low AC voltage, the rectifier has stopped working, However, the monitoring part still has to work properly and maintain normal monitoring and communications.

Some power supply products have appeared in the process of no-failure reset and other phenomena. When the auxiliary power supply for high-power switching power supply is designed, it is analyzed, and it is found that the auxiliary power supply exists in different AC input voltages and different load conditions. Problem: The scope of AC adaptation is narrow, load capacity is low, work waveform is unstable and extremely asymmetrical, bias magnetism occurs, and electromagnetic interference is extremely serious.

So how to solve the switching power supply interference problem?

The simple input filter circuit is formed by a filter capacitor connected between two power lines. As long as the capacitor is properly selected, it can suppress the high-frequency interference. The choice of this capacitor mainly considers the withstand voltage value as long as it satisfies the voltage rating of the power line and can withstand the expected voltage surge.


The effective method of suppressing radiation noise is shielding. The electric field can be shielded with a material with good conductivity, and the magnetic field can be shielded with a material with high permeability. In order to prevent the leakage of the magnetic field of the transformer, the primary and secondary coupling of the transformer is good, and the closed magnetic ring can be used to form a magnetic shield. The shell of the entire switching power supply also needs to have good shielding characteristics, and the seams must meet the EMC requirements for shielding. Through the above measures, it is ensured that the switching power supply is neither disturbed by the external electromagnetic environment nor interferes with external electronic equipment.

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