I am not 100% sure where to put this, but here it goes. I am tasked with designing a DCM flyback converter to be used as an energy recovery converter for an RCD turn-off snubber used in a high-side 120V 400A single quadrant buck chopper. Basically, the flyback is operated in DCM so as to emulate a resistor. The converter maintains the voltage on a large bulk capacitor which absorbs the turn off snubbing energy of the main buck transistor that chops 400A, while the output of the flyback is hard-wired to the main DC bus.


QUESTION: My question is the control method. The flyback operates in DCM. Since the converter controls its own input voltage, I found that peak current mode control is unstable (ie a RHP is present in the plant xfer function)-unless an external stabilizing ramp is added. I found that voltage mode DCM is inherently stable (ie simple first order pole-type response if small L is neglected in DCM). My questions are a follows:

1. Do you think it would be better to try and use peak current mode control with a stabilizing ramp?

2. I am thinking it would probably be a better idea to use voltage mode control....what is your opinion?

3. Maybe it would be simpler to run the converter in open loop? After all, I would be using an ordinary resistor with a huge heatsink if I hadn't decided to take the active snubber approach.

Your opinions would be great. Sorry for the lengthy post! Thanks for all the help these forums are awesome.