Pulse group suppression in switching power supplies
Switching mode power supply can be used individually as a piece of electronic equipment, but more often switching mode power supply is used as a component with each piece of electronic equipment. Therefore, switching power supply has its own special characteristics, switching power supply electromagnetic compatibility performance is related to the normal use of each piece of electronic equipment. Because of this, the electromagnetic compatibility of an electronic device is good or bad, the first thing to look at the switching power supply electromagnetic compatibility performance is good or bad.
① Pulse group suppression of switching power supply
In the case of switching power supply, leaving aside the input filter of the switching power supply, the switching power supply line itself has no effect on the pulse group interference.
The 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 all set up for suppressing low-frequency differential-mode interference, in which the electrolytic capacitors for the ripple suppression of the switching power supply itself is not enough, not to mention the harmonic component of pulse group interference that reaches more than 60MHz. Interference suppression effect, so in the oscilloscope to observe the switching power supply input and output pulse group waveforms, do not see a significant interference attenuation effect.
Considering that the pulse group interference is a common-mode nature of the interference.
In the case of switching power supplies, the use of input filters is a switching power supply to suppress the pulse group interference ** an important measure.
Secondly, the design of high-frequency transformer in the switching power supply line, especially the use of shielding measures, has a certain inhibition effect on the pulse group interference.
Again, the switching power supply primary circuit and the secondary circuit between the cross-connect capacitance, can be from the primary circuit into the secondary circuit of the common-mode interference return to the primary circuit to provide a path to the pulse group interference.
It also has a certain suppression effect on the pulse group interference.
Finally, adding a common-mode filter circuit (common-mode inductor and common-mode capacitor) to the output of the switching power supply can also play a role in suppressing pulse group interference.
