Hello. I have a design for a high-power converter using the 256404 which is going through the motions of starting up, but doesn't output any significant voltage and keeps rebooting every 1 second. It is intended to output 30V at 1.2kW.
Input is 400V-DC from my PFC stage, although I have bypassed that at the moment with a bench supply.
I have also provided VCC from bench supply and have put a fixed 1.2V on the BLK input.
This plot below shows the HO switching voltage (measured at the FET pin) in yellow.
The red trace shows the voltage at the output of the transformer (input of resonance capacitors - TP-B1 on my schematic)
I don't know whether this is a normal waveform to expect, or whether something isn't right. I'm hoping somebody can point me in the right direction and if I can make more measurements to help diagnose.
Any pointers as to what to look for would be appreciated.