Re: MOSFET timing

[Rod.Hower@ametek.com]

Instead of me rambling on about technical MOSFET design techniques,
just go to the International rectifier website and read the application
notes.
Some of the better notes are listed below.

The do's and don'ts of using MOS gated transistors (IGBT's and MOSFET's)
http://www.irf.com/technical-info/appnotes/an-936.pdf

Gate drive characteristics and requirements for MOSFETs
http://www.irf.com/technical-info/appnotes/an-937.pdf

Paralleling HEXFET power MOSFET's
http://www.irf.com/technical-info/appnotes/an-941.pdf

Good luck,

Rod
W8RNH




                                                                                              
                    jcmassey@netspac                                                          
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                    owner-ev@listpro        Subject:     MOSFET timing                        
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                    05/30/01 09:16                                                            
                    PM                                                                        
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Greetings all our controller building gurus.

The three of us here (on the other side of the planet) who in this area are
building EV's, have been discussing MOSFET switching. I can see the benefit
in just using three or four FETs with a pulse current capability equal to
the controller combined maximum, and not worry about having to make sure
that the FETs all turn off together.

Daniel (who had the idea of the fusing individual FETs, but is a good RF +
microwave comms guy) is not convinced that it'd be more (cost) effective to
use a small number of au$200 FETs as opposed to 30 or so $1.50 FETs and
putting more into ensuring timing.

His opinion is that if:

All devices are from the same batch,

Each FET has its own driver, all from one batch, and

The physical layout ensures that the propogation delay in each driver train
is identical (the RF tech. coming out here).

Then the FETs should all switch together. Since we would be building four
controllers (if we build at all) it would be worthwhile to do a PCB to
match propogation delays, etc. I believe it would be far easier to spend
the time it would take to do the layout etc., in doing repairs to earn the
money to buy the larger FETs. However - is Daniel on the right track, & let
him get on with it, or is he missing something about power switching and
wasting his time?

Speaking of wasting peoples' time - thanks for letting me waste yous.

James Massey