The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: "Peter Larsson"
Subject: Re: Transient problem !
Date: Fri, 10 Jan 2003 23:57:50 +0100
NNTP-Posting-Date: Fri, 10 Jan 2003 22:57:19 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"Robert Baer" skrev i meddelandet
> Peter Larsson wrote:
> > Hi !
> > I have this circuit:
> > 12V_________________
> > |
> > |
> > | | 10 ohm (0,1uH series inductance)
> > D |
> > Gate IRFP150
> > _____________S__|___
> > GND
> > The problem is this: I drive this test application with an 12V car
> > 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
> > When the GROUND line is measured, there are also an increase of the
> > transient towards the electrolytic cap. This capacitor has been removed
> > the result is ringings over the squrewave but the transient is still
> > 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 ?
> > Peter
> 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.
Yes I admit that it seem to bee strange, but the circuit can fast be rebuilt
to a simple boost converter by adding a "coil" ,diode and capacitor.
The problem is that I have a transient in the system and it seem to be
something strange since the transient is still there with this simplified
circuit. Note the problem when I follow the ground line from the battery
source towards the MAX 627 ground I even there have a growing transient (yes
in the ground line!), and this is depending of the load.This line is not
shared with the line that goes to the load.
Using coax, well i use it to the input but there I have wire ("short" 2cm)
attached with clips.
What do you mean with bypassing between the supply and ground lines ?
I have the capacitors mentioned above placed close to the MAX 627 driver.
Termination of the drive signal ??
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup