Question
L4986 startup problems with external VCC supply
I am evaluating a PFC with the EVL4986-350W evaluation board.
To be able to use Boost coils without the extra winding I want to supply the VCC voltage from a buck converter connected to the output voltage. The voltage from the buck is 17V.
I have tried to connect the buck directly to VCC capacitor and wia the diode (D7) to VCC. C9 was disconnected.
Why doesn't the PFC start up?
It start up if I connect the VCC voltage after the AC power but not if the VCC is powered up before or at the same time as the AC-input.