Dear ST,
I’m designing a PFC stage based on Application note AN2994, my design is practically identical, I just have a coil 20uH bigger and very minor changes. Same input-output requirements.
I’m getting overall results close to the specified but the main problem I’m getting is the heavy distortion on the current after zero crossing, specially when input voltage is on the middle range, between 90-200 Vac. You can see in the pics below the current rushing to a peak every half cycle then stabilizing.
You can also see the effect on the Input voltage because of the weak grid of the testing setup . Please ignore it, the current is the same with a strong grid.
All images at full resistive load (400W).
150 vac input Hight distortion after zero crossing
230V input
With 80-90 input volts I get cleaner input current signal with larger current on the PFC coil, so it’s not an effect of the inductor saturating.
I appreciate any insight you can provide me.
