Gate Drive Transformer Reset at 20kHz+ - Page 1
Forum section: electronics / beginners

author: Time
author_rank: Frequent Contributor
timestamp: August 13, 2014, 10:34:56 pm
content: 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?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2014, 02:01:39 am
content: Reset?What application?

author: Time
author_rank: Frequent Contributor
timestamp: August 14, 2014, 02:48:40 pm
content: 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?

author: Marco
author_rank: Super Contributor
timestamp: August 14, 2014, 03:17:39 pm
content: 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

author: Time
author_rank: Frequent Contributor
timestamp: August 14, 2014, 03:35:11 pm
content: 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.

author: David Hess
author_rank: Super Contributor
timestamp: August 14, 2014, 04:15:06 pm
content: Look up how forward converters reset their transformer. They generally use a separate reset winding but that is not necessary.

author: Marco
author_rank: Super Contributor
timestamp: August 14, 2014, 05:03:54 pm
content: No experience, but this paper has a couple versions :http://eprints.qut.edu.au/63591/1/fetdrvr-t.pdfLike 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.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2014, 11:16:57 pm
content: Quote from: Time on August 14, 2014, 03:35:11 pm25% 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

author: Time
author_rank: Frequent Contributor
timestamp: August 16, 2014, 06:07:29 am
content: 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.

author: Dago
author_rank: Frequent Contributor
timestamp: August 16, 2014, 06:37:47 am
content: 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.pdfor traditionalhttp://www.irf.com/product-info/datasheets/data/ir2110.pdf