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From: Mike Poulton
Subject: Re: Problems with MOSFET drivers
Date: 16 Nov 2002 11:53:04 GMT
Organization: MTP Technologies
On 16 Nov 2002, firstname.lastname@example.org (Adam Seychell) said:
> 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.
Thanks :-p I would note that there is a significant difference between
danger to oneself and danger to equipment. I'm quite well versed in
high voltage safety precautions, and this project doesn't even warrant
most of those. The 300VDC supply is dangerous, but no more so than any
other 208V line powered device. The output poses no more hazard than
any other medium sized Tesla coil. This does not even compare to a
pulsed YAG laser power supply or neon tube bombarding system. However,
it does provide numerous opportunities to destroy expensive
semiconductors by the dozen.
I would also note that this is far from the first time I've built a
switching power supply containing a mosfet H-bridge. This is the
highest frequency and highest power I have tried to switch, though --
both by an order of magnitude. It is also the first time I have tried
to switch a high voltage load with a full bridge, thus requiring
complete isolation of the gates from the driver circuit.
> 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.
> * buy your semi's in quantity from a distributor since you'll end up
> saving money after smoking more than you anticipated.
I have piles of mosfets, but I didn't anticipate burning the drivers. I
won't be applying more than 24V to the H-bridge until everything else
seems to be working correctly. Hopefully that will save me some fets.
> * get access to >= 60MHz CRO if you hanv't done so already.
I have that.
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