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From: swain@liverpool.ac.uk (Mr J.R. Swainston)
Subject: Re: H-Bridge Info???
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Date: Thu, 16 Feb 1995 10:02:45 GMT
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Christopher Kristof (ck3i+@andrew.cmu.edu) wrote:
:     I'm looking for any info on building H-bridge circuits using power
: MOSFETs.  Data Books, regular books, technical reports...   I have The
: Art of Electronics, but it doesn't even address the H bridge concept.  I
: know how they are generally constructed,

[snip]

:  I know that NMOS FETs are always a bit "better" than pmos FETs (or
: visa-versa), so how does one choose a complementary pair?  Also, what
: needs to be done to keep the MOSFETs from getting killed by inductive
: kickback and other such annoying processes?  I've tried the old diode
: between source and drain, but that doesn't seem to be working.

	For protection from inductive effects build a snubber circuit for
each power circuit.  A simple RC can provide protection, but for more 
efficient operation use an active snubber, with energy recovery.

:     I'm looking to build a bi-directional H-bridge that can handle
: 20-30A at 8V.  I've tried before (a few times) and just keep killing
: expensive MOSFETs.  Thanks for any info that's provided.

	Also, be careful of how you drive the MOSFETS, as the gate voltage 
normally has to float in accordance with the D and S voltages.  The INT200
and INT201 devices can provide high and low side drive for this.
	Some new IGBT devices now also have built in protection, and are 
relatively difficult to damage (but not impossible!).


	Further info can be found in:

	POWER Electronics (Devices. Drivers and Applications),
	By B.M.Williams, published by MacMillan Education Ltd in 1989.
	ISBN 0-333-39662-6.

Cheers,

		John.....

--
*   Mr.J.R.Swainston (swain@liverpool.ac.uk),         051-794-4539 ext 4610 *
*   Dept of Electrical/Electronic Engineering,  The University of Liverpool,*
*   PO Box 147, Liverpool L69 3BX. U.K	         (PGP available on request) *
