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From: email@example.com (Eric Y. Chang)
Subject: Re: Problems with MOSFET drivers
Date: Sun, 17 Nov 2002 00:48:39 +0000 (UTC)
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Date: Sun, 17 Nov 2002 00:48:39 +0000 (UTC)
X-Newsreader: TIN [version 1.2 PL2]
Adam Seychell (firstname.lastname@example.org) wrote:
: I'm impressed in your dedication and willingness to attempt such a
: dangerous and high power project with the amount of understanding you
: have as it appears in your posts. My hat is off to you.
World needs more courageous people. But, even more, the world needs
people who can think through a problem.
: My suggestions
: * Study all the MOSFET technical litrature at www.irf.com. And get a
: good understanding of power switches and how to drive them correctly.
: There are many app notes on MOSFET drivers, also visit sites Telcom
: and TI.
It is very likely that app notes will not address this situation.
: * buy your semi's in quantity from a distributor since you'll end up
: saving money after smoking more than you anticipated.
This is not the way to save money. This is a way to save $2 each by
buying in lots of 10000. Note this will still cost as much as a small
: * get access to >= 60MHz CRO if you hanv't done so already.
And look for what? Gloat rights on owning a fast oscilloscope.
First, one should ask why 9A drivers are being destroyed. Yes, the
data sheets say that they are bulletproof, but obviously they are
not. When a device rated for 9A violently explodes, the cause is
usually overcurrent. The overcurrent can be stopped by a "fuse."
A standard fuse is probably not fast enough, but it might be.
But, a few of these expensive parts should pay for a better fuse.
There are lots of examples in design notes that open plenty fast.
Of course, speed in itself is not as important as I2t rating of
the device. I would have sprung for a fuse as soon as I popped
a single expensive MOSFET driver.
If you still cannot figure out what is wrong after blowing several
devices (oh, don't buy 10000 just to get the quantity discount),
make your own (totem pole is good enough) and give it a shot. You
might even wish to perform a simulation if a SPICE type program is
BTW, I have never seen this problem, but I have no experience with
high Q resonant tesla coil drivers. I saw a www page that said that
they were very difficult to design, much more so than the standard
Try to find a good model.
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