UV desinfection controller

Hi guys,

we have an UV controller for desinfection which has a PCB with first stage of PFC using L6561, I attach datasheet. The problem is the filter capacitor (C5 in datasheet page 6) explotes because it gets too high voltage. When we checked with scope we saw PWM output aparently correctly swithing when at pin 5 we gets 2.5V and down for controlling.

Any idea why it gets such high voltage? We found also 10nF capacitor broken but after replacing it we still had the same behavieur. We also checked R1 and R2 which seems to control overvoltage protection.

Page 6 of the datasheet shows three different schematics for use on different supply voltages. And the value and rating of C5 is different in each.

Which schematic matches your board?
At what line voltage are you testing it?
Is that the voltage that the unit was originally intended to operate at?

Thank you for your reply. Finally, we had to disable PFC circuit, which was controlled by microcontroller, in fact, there were 2 micro and a lot of feedbacks by optocouplers.
It is working without PFC now.