Newsgroups: comp.robotics
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From: browen@aoc.nrao.edu (Bruce Rowen)
Subject: Re: H-Bridge?
Message-ID: <1993Dec17.180704.10629@Mr-Hyde.aoc.nrao.edu>
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Reply-To: browen@aoc.nrao.edu
Organization: National Radio Astronomy Observatory, Socorro NM
References: <1993Dec16.091826.2797@juliet.robots.ox.ac.uk>
Date: Fri, 17 Dec 93 18:07:04 GMT
Lines: 31


>
>
>	A better idea is  using a integrated H-bridge rather than to get one 
>using MOSFETs by yourself. only a PWM signal and a direction singal is needed 
>to drive the H-bridge. Generally, the inputs are TTL and/or CMOS compatible.
> Two numbers come to mind: L6203 by NS and UDN 2954. The specifications 
>of these two chips may not be what you want, but you should be able to find
> what you want  along this line.


Also try the IR8200 series from International Rectifier. The most common 
reason I've seen discrete device  H-bridges blow up is that people fail to 
consider the shoot through current. When you don't take the non-symmetry
between turn on and turn off times into consideration, you get a short lived
condition where a current path exists between the positive and negative rails
of your power supplies. This results in a large current rush through the
bridge power devices which eventually destroys them. Transistors have 
very slow on/off times compared to MOSFETs and this is one reason devices
get hot when your load is well within the devices ratings.


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Bruce Rowen 				National Radio Astronomy Observatory
Scientific Programmer				Array Operations Center
browen@aoc.nrao.edu			  P.O. Box O  Socorro, NM   87801
(505)385-7329					     (505)385-7000
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