[Diy_efi] Flyback Diode (was 555 timer...)

[Mike]

At 12:40 PM 7/11/05, you wrote:
>beg my pardons....... i am using a different FET after i cooked a few '640s from a low R injector on my gen-set
>i then went to ecuv2.0 with the surface mount FET rated at 60v 40amps and a 2" sqare heatsink i havnt blown one up yet (touch wood) but it doesnt get hot.
>im not sure if im driving it too hard but it "seems" not to mind

Package can make a difference to parasitic oscillations and the only real way
to check that your FET (MOSFET) is doing the right thing is with a CRO,
you can check gate oscillation, turn on and turn off time and with the aid of
a (small) resistor you can check whether the FET (MOSFET) is fully on, in
other words achieving lowest Rds on for the appropriate specification, those are
the basics, other issues such as logic driven FETs might appear to be a plug in
replacement but are sometimes a substitute for understanding, as I've been on
this list (on and off) for many years, I really try to pursue understanding through-
out all the members and look forward to Adam Wade responding to a simple
thought experiment regarding pressure and flow  ~`:o)

<chuckle>

Regards from


Mike Massen
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
Twin tyres etc

http://niche.iinet.net.au







>//BidSpec
>
>----- Original Message ----- From: "mike turner" <yardcooliediy at charter.net>
>To: <diy_efi at diy-efi.org>
>Sent: Saturday, July 09, 2005 6:11 AM
>Subject: Re: [Diy_efi] Flyback Diode (was 555 timer...)
>
>
>>The integral diode is generally slower than the external diode. This raises its dissipation above that of a faster diode. Also, using an external diode moves that dissipation off the mosfet which might be needed if you have omitted the mosfet heat sink for the bench test. :)
>>
>>Mike Turner
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>>Diy_efi at diy-efi.org
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>
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