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From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Transient problem !
Date: Fri, 10 Jan 2003 21:29:59 GMT
NNTP-Posting-Date: Fri, 10 Jan 2003 13:29:59 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Peter Larsson wrote:
> Hi !
> I have this circuit:
> | | 10 ohm (0,1uH series inductance)
> D |
> Gate IRFP150
> The problem is this: I drive this test application with an 12V car battery.
> The gate is driven by a MAX627 mosfet driver(runs at 100kHz) with
> 0.1uF(polyprop) and 680uF (low esr electrolytic) connected on the supply
> line and close to the MAX627 from the same battery.
> There is a high transient over the drain and source at turn off. The
> transient is about 25 volts between drain and source and very narrow.
> If I parallel another 10 ohm resistor the transient increases to 40 volts.
> When the GROUND line is measured, there are also an increase of the
> transient towards the electrolytic cap. This capacitor has been removed and
> the result is ringings over the squrewave but the transient is still there !
> My question is where does this come from?
> IRFP data:
> Source inductance:13 nH
> Drain inductance:5 nH
> How can I find the source of this narrow transient ?
The circuit was all skoogie, i attempted to fix it and it still looks
In any event, you said nothing about bypassing between the supply and
ground lines at the FET, as well as nothing about using a coax for the
gate drive and termination of the drive signal.
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