Pulse Group Suppression for Switching Power Supplies
Switching power supply can be used as a standalone electronic device, but more often than not, it is used as a component in conjunction with each electronic device. Therefore, switch mode power supplies have their own characteristics, and the electromagnetic compatibility performance of switch mode power supplies is related to the normal use of every electronic device. Therefore, the electromagnetic compatibility performance of an electronic device depends first on the electromagnetic compatibility performance of the switching power supply.
① The problem of pulse group suppression in switching power supply
As for switch mode power supplies, aside from the input filter of the switch mode power supply, the switch
The suppression effect of the power line itself on pulse group interference is very low. The main reason is that the essence of pulse group interference is high-frequency common mode interference, and the filtering capacitors in the switching power supply line are designed to suppress low-frequency differential mode interference. The electrolytic capacitors in the switching power supply have insufficient ripple suppression effect on the switching power supply itself, let alone suppression effect on pulse group interference with harmonic components above 60MHz. Therefore, when observing the pulse group waveforms at the input and output terminals of the switching power supply with an oscilloscope, there is no obvious interference attenuation effect.
Considering that pulse group interference is a common mode interference.
For switch mode power supplies, using input filters is an important measure to suppress the pulse group interference received by the switch mode power supply.
Secondly, the quality of the high-frequency transformer design in the switching power supply circuit, especially the adoption of shielding measures, has a certain inhibitory effect on pulse group interference.
Furthermore, the cross capacitor between the primary and secondary circuits of the switching power supply can provide a pathway for common mode interference entering the secondary circuit from the primary circuit to return to the primary circuit
It also has a certain inhibitory effect on pulse group interference.
Finally, adding a common mode filtering circuit (common mode inductor and common mode capacitor) at the output of the switching power supply can also play a certain role in suppressing pulse group interference.
