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UC3854A: current peaks at zero-cross

Vitaly Baranov
Prodigy 10 points
Other Parts Discussed in Thread: UC3854A

Hello. I am using UC3854A for 2500W PFC. I have encountered a problem of large current peaks on zero-cross. The amplitude of peaks depends on the value of Rmo & Rci - the larger the value, the larger the amplitude of peaks.

Here are the pictures of input current at 220W load.

Rci & Rmo = 4.7k

Rci & Rmo = 1.8k

I could just reduce Rci & Rmo, but in this case the multiplier output is overloaded at peak load and the PFC almost shuts down, even though the values were calculated according to SLUA144.

Please, help.