Transistor Ignition question

[Stewart Prince]

If you just want a simple fet with no current limiting, and you want 5 volt control,
consider the international rectifier logic level hexfets. Their web site has a
pretty neat setup for selecting automotive fets and they're pretty good about
samples.
S. Prince

Branko Badrljica wrote:

> When replacing the bad part it all depends on transistor used.
> It would be verz helpful if he could include schematics of what was near the
> broken part.
> Then, one might be able to guess what was used originally. BTW: Does originnaly
> used transistor have
> some marking on it ?
>
> I have done one or two designs for our magazine and I have to say that modern
> FETs rule here.
> Only drawback is necessity to have 10V voltage levels just to drive them, BUT:
>
> - modern FET can live through overvoltage spikes, if energy amount is
> reasonable, even repetitively.
> So your 600V FET will simply clamp occasional spikes over 600V with no harm
> done, if energy of the spike
> would not meltdown the silicon !
> - they can turn on and off VERY fast- which translates to very high induced
> voltages and
> very reliable spark. IIRC mine was able to switch in some 15 ns!
> -they have inherent antiparallel diode which prevents them from the oposite
> polarity inductive kick of the ignition coil...
> - modern FETs have very low resistance when fully on, so power dissipation is
> minimal.
>
> IGBTs are meant to reach higher current densities than simple FETs, but they are
> much slower
> and can suffer from bipolar illnesses. For simple ignition coils they are
> unneccesary, anyway.
>
> Regards,
>
> Branko.
>
> BTW: I'm thinking about doing whole thing again and writing an article about it.
>
> So, I would like to know, what are generally required properties of these things
> (cylinder numbers,
> internal calculation of advance angle etc.
> Is there any demand for these things nowadays ?
>
> Rich M wrote:
>
> > A good general purpose ignition driver device is Motorola (ON Semiconductor)
> > IGBT device MGP20N40CL.
> > It is internally clamped to 400V max with gate overvoltage protection
> > integrated. It is capable of switching 20Amps at 400V max (internally
> > clamped) collector voltage. It can also be driven at the gate by 5V logic.
> > Package style TO220.
> > Available in UK and probably Europe from Farnell - www.farnell.com - part
> > number 300-5732, price approx. 4.50 UKP
> > Hope this helps
> >
> > Rich
> >
> > >-----Original Message-----
> > >From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> > >Behalf Of Arnaud Westenberg
> > >Sent: Thursday, February 08, 2001 1:39 AM
> > >To: diy_efi at diy-efi.org
> > >Subject: Transistor Ignition question
> > >
> > >
> > >Hi,
> > >
> > >I have some questions about my motorcycle ignition. It's a transistor
> > >ignition from 1980 for four cylinders with pick up sensors and wasted
> > >spark setup (Suzuki gsx1100 '80). Problem is that one of the two
> > >transistors is broken and I don't have a clue what type it is.
> > >
> > >I've tried replacing it with a 'normal' transistor rated at high
> > >voltage, can't remember the voltage exactly but I believe it was around
> > >400V. This worked for a while, although with a less powerfull spark at
> > >low rpm, but like expected it broke again. I guess it couldn't handle
> > >the high levels of voltage and current at the same time?
> > >
> > >I've read an application note about IGBTs and I think that such a
> > >transistor might work in the old ignition system. Reading about the
> > >IGBTs protection/operating area makes me quite confident that such a
> > >transistor wouldn't break in this application. Probably IGBT's are
> > >specifically designed for automotive use?
> > >
> > >I'd like to know if you think a IGBT would work, how to select one and
> > >where (what kind of store) I can order one without having to buy 10,000
> > >of them. (I'm from the Netherlands).
> > >
> > >The only selection criteria I can think of is the basis lead voltage
> > >level at wich the transistor switches, but again I don't know this level
> > >either. I could try to get an indication of this voltage with an
> > >oscilloscope (PC card) provided this voltage isn't influenced by
> > >removing the transistor??
> > >
> > >Could someone please talk me through this because a new ignition module
> > >costs around $400 (USD) so there's quite some budget available to find a
> > >suitable transistor? Guess I don't have to mention that I'm not an EE
> > >:-))
> > >
> > >Thanks for any help.
> > >
> > >Greetings Arnaud
> >
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--
STEWART PRINCE

PROFESSOR, MECHANICAL ENGINEERING

CALIFORNIA STATE UNIVERSITY, NORTHRIDGE


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