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PFC and pulsed loads


Advanced Member level 5
Jun 13, 2021
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What if your load is 200W average, but its 10ms ON...10ms OFF...repeatedly. It can never pass PFC, even if perfect PFC stage at front end.
How is this dealt with by the electrical regulations? eg, EN61000-3-2
Thanks, the attached shows Mains input current and voltage to a PFC/2 Transistor forward converter (2TFC is in burst mode).
Mains is 60Hz. The PFC has Cout = 100uF.
Its BCM Boost PFC.

The load is ON at 400W for 8.33ms, then OFF for the next ON for one mains half cycle, then OFF for the next, and so on...
It easily passes Class A and Class D Mains Harmonics according to the LTspice FFT function.

This shows that pulsed loads dont really significantly affect Mains Harmonics for PFC stages.

As can be seen the Mains input current does have an overall DC (average) level of 283mA though.


  • Mains harmonic levels.jpg
    Mains harmonic levels.jpg
    169 KB · Views: 22
  • Waveforms 8p33m.jpg
    Waveforms 8p33m.jpg
    117.3 KB · Views: 23
Have you verified that whatever PFC test you are actually "on the hook"
for, calls out a non-steady-state load? Or are you applying a nonstandard
"test case" and using standard limits to criticize?
Thanks, since our load is only ever pulsating, we assume the standards bodies will enforce that we have it pulsing during the EN61000-3-2 test.

One other worrying point, is the level of DC in the input current.....but its impossible to find out which EN standard covers the allowable level of DC current in the input current to an offline SMPS?
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