Gate Drive Transformer Reset at 20kHz+

[Time]

What are some common circuit topologies for handling gate drive transformer reset at 20 kHz (the high end of audio)?

I have commonly seen a combination of zener's and regular diodes but how to spec. the parameters is not completely.

Anyone have some experience in this area?

[T3sl4co1l]

Reset?

What application?

[Time]

Using a gate drive transformer (1:1) to provide an isolated drive signal to a power electronics device, like a power MOSFET.  What are some common techniques for dealing with the reset of the transformer?

[Marco]

You just use a near 50% duty cycle, which is not to say you have to drive the MOSFET at 50% duty cycle ... but you'll need to get tricky to avoid it.

http://www.irf.com/technical-info/appnotes/an-950.pdf

[Time]

Unfortunately I want to be more in the 25% duty cycle range.  I know I have seen some clever circuits involving a zener diode combine with a normal diode in parallel with the primary.  I was just curious as to how this works and if anyone has experience with them.

[David Hess]

Look up how forward converters reset their transformer.  They generally use a separate reset winding but that is not necessary.

[Marco]

No experience, but this paper has a couple versions :

http://eprints.qut.edu.au/63591/1/fetdrvr-t.pdf

Like it notes though, these kind of circuits have limited high time because the gate isn't actively driven and leakage will pull it down. That's why they decided to use a circuit with a separate isolated power supply in the end.

[T3sl4co1l]

Unfortunately I want to be more in the 25% duty cycle range.  I know I have seen some clever circuits involving a zener diode combine with a normal diode in parallel with the primary.  I was just curious as to how this works and if anyone has experience with them.

25% range, for one channel, or is this driving two complementary sides, or what?!

While you can fully abstract this problem by hiding information from us and leaving it in only the most general terms, you are guaranteed to end up with a wasteful, expensive, poorly performing design.  Some circuits are more suitable than others.

You may not even want a transformer at all, but unless you tell us something about it, we can't help.

Tim

[Time]

Ok.  I want to drive a silicon power mosfet with a gate source capacitance of a few nF through a pulse transformer at 20 kHz to create pulses via a high side switching configuration.  No complementary sides, just one device that is creating pulses.  The duty cycle might change but it will always be low, 25% at the most.  I am just brainstorming options at this point and more or less trying to figure out what may be considered the conventional approach.

[Dago]

I'd say just forget about gate drive transformers in an application like this and use an isolated gate driver like ADuM7234: http://www.analog.com/static/imported-files/data_sheets/ADuM7234.pdf or traditional http://www.irf.com/product-info/datasheets/data/ir2110.pdf