On Wed, 15 Jan 2003, Roman Black wrote:

*>> They are not faster than an equivalent sized (in amps of junction size)
*>> standard silicon rectifier, rather slower.
*>
*>Is this right? How can you use them in a PWM
*>hbridge if they are slower than standard rectifiers?
*>In that use the diode may be on for 3x the time that
*>the FET is on, surely this requires a fast and low
*>Vf diode?

When this is the case the clever designers turn on the fet's gate during
this time. It is not hard to do.

*>> TO220s that run 150W for any length of time tend to fail in my experience.
*>
*>Many are specced at 65W up. 150W sounds very excessive
*>for a TO-220 pack. :o)

Most MOSFETs in TO220 for 50V and 50A or so are specced to 150W. This is
the upper limit of anything that comes in a TO220 case afaik and it is not
so good to try it. Unless you have very exotic cooling arrangements
(circulating oil bath or expanding compressed air or freon 'heat pipes'
come to mind here).

Peter

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body