John P is right, my brain was in neutral. The diode obviously doesn't return the energy to the capacitor since there's no path to ground for the return current. To do that you'd have to disconnect the input of the inductor from the capacitor and connect the input to ground at the same time you turn-off the MOSFET at the right end, obviously a somewhat complex switching process. Can't offhand think of a simple way to do that.

 

All right. My suggestion of 11-02-2013, 04:19 PM now seems to be getting taken more seriously! But I'm still not sure about the transformer option--can it just be done with an extra winding and a diode?

 

I think the problem is the sheer size of the inductors.

 

okay, I'm glad I'm not crazy . Shorting the inductor with D6 never made any sense to me from the get-go.


John P. I think that your idea is sound, but might be difficult to source a suitably spec'd transformer to do the job. In fact, even finding a suitably spec'd inductor is proving difficult. By reducing the pulse time and hence the resonant frequency of the circuit, I brought my requirement down from 0.12H to 2.5mH, and even then, a 2.5mH inductor rated for 30A is way too big. At first I thought that maybe a much smaller, lower amperage rated inductor might due, because it's only pulsed operation, but it's clear that if the inductor goes anywhere near its saturation current, the inductance drops off sharply.

ronv, it seems you knew that already any further thoughts on the voltage divider/comparator idea we were discussing? I don't mind putting the work into creating the massive LED array in LTSpice (looks like .asc file syntax is fairly simple, so I might be able to write a script to do the bulk of it), but I could use some help in finding the right comparator.

 

Yes, I'd worry about the physical size of an inductor/transformer with those specs. Pretty big, heavy and costly, I'm afraid. But then, will the capacitor be any less troublesome? That's also going to be a hefty item.

 

indeed, the capacitor's size is troublesome as well, but acceptable because I've been planning/designing around that trouble since I started the project