My 700W design used 500V IRF462 devices in half bridge running from a 340V
rail - not a massive design margin there. I used transformer drive direct to
the devices, with the transformer primary driven from a TC4426 IC running
from +15V rail (via a capacitor of course!). The drive transformer turns
ratio was 1:1+1 so the FETs received 15V drive peak-peak. I did wonder,
initially, about the need for negative gate clamps, but there was no reason
to do so at all for any reasons associated with MOSFET itself. Switch
Mode PSUs need DC restoration after a drive transformer because they don't
use a 1:1 duty cycle, but that is not the case here; duty cycle is exactly
50%.
That 700W Tx copied the Decca idea of having a small damped inductor in
series with the two FETs to absorb with the switching transient. I blew
many devices during the development phase, but all explosions were
accounted for and the design is very robust now.
Andy G4JNT/G8IMR
-----Original Message-----
From: Alan Melia <[email protected]>
To: [email protected] <[email protected]>
Date: 2005/09/28 13:54
Subject: LF: Re: RE: Re: Advice will be gratefully received
Negative drive swing clamps.....I think I am right in that.... check in the
Decca circuit (LF Exp Hdbk) that is transformer driven.
My guess is the 100V devices will just stand the 24 volt supply
Cheers de Alan
----- Original Message -----
From: "OSBORN, Chris" <[email protected]>
To: <[email protected]>
Sent: 28 September 2005 12:01
Subject: LF: RE: Re: Advice will be gratefully received
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