Can UCC28780 be used for passive clamped flyback converter? I've tried to use this controller in a passive clamped flyback circuit. I'm not connecting the PWMH pin to anywhere. In the space of HS GaN FET, I'm using a superfast diode. Otherwise, the schematic is just the same (except the snubber resistor in parallel with the clamp capacitor; its value is 12k in my schematic) as given in the reference design TIDA-01622. 

I'm more interested in learning the control strategy of the ACF controller in this configuration. What I found is that at Vin=325V, Vout=15V, Iout=3.15A, PWML isn't coming at the first valley of switching node always.Passive clamp flyback with UCC28780.pdf I'm attaching the waveform here. What's the cause of this? I can understand that as ZVS isn't happening now the control strategy of ACF (UCC28780) won't be applied here. Then how does the controller decide when to provide the PWML (or turn on the primary FET) signal?