Transistor Ignition question

[Branko Badrljica]

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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