Part Number:UC2854A
Hello,
I am using UC2854ADW for 5kW PFC Boost converter (90V-270V Input AC and 400V Output) . I am facing some issue where PFC output voltage doesn't regulate and starts to rise gradually when the converter goes from full load to no load condition. We have DC bus fault protection where it turns OFF the controller IC.
I was going thru some application notes and I found that Imout pin (Pin 5 of UC2854A) has a clamping diode to prevent voltage from going below -0.5V.
When I connect this diode, I do not see any overshoot issue in DC bus voltage. But since every diode has junction capacitance so when I connected some low value ceramic cap (~22pF to 100pF) across it, it is also helping out. But some of the board works fine with 220pF capacitor and gives the same fault below that value.
My question is, will there be any issue if I connect 220pF cap. across Imout and GND. Will it have an effect on peak input current or power factor ? Or should I use clamp diodes, If yes, can you recommend what type of clamp diodes I can use here ?
Any suggestion will be highly appreciated.
thanks & regards,
vivek