MOSFET for electronic ignition?

P

Paul Burridge

Guest
Hi all,

Would a power Mosfet be an appropriate choice for driving the primary
side of a EHT ignition coil? If so, any recommendations as to type
number would be appreciated. If not, what other device would be better
suited?

thanks,

p.
--

"What is now proved was once only imagin'd." - William Blake, 1793.
 
"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:5eibq0dqdgdcelfmssnloifr98u8o7353g@4ax.com...
Hi all,

Would a power Mosfet be an appropriate choice for driving the primary
side of a EHT ignition coil? If so, any recommendations as to type
number would be appreciated. If not, what other device would be better
suited?

thanks,

p.
Click to expand...

The IRGB14C40L IGBT is designed for electronic ignition circuits. This is a
very strange IGBT since it uses logic level gate drive. It also expects a
1k resistor in series with the gate. The collector-emitter breakdown
voltage is self clamped to about 400V, so ignition circuits built with this
device can be very simple.

http://www.irf.com/product-info/datasheets/data/irgs14c40l.pdf
 
Paul Burridge <pb@notthisbit.osiris1.co.uk> wrote in message news:<5eibq0dqdgdcelfmssnloifr98u8o7353g@4ax.com>...
Hi all,

Would a power Mosfet be an appropriate choice for driving the primary
side of a EHT ignition coil? If so, any recommendations as to type
number would be appreciated. If not, what other device would be better
suited?

thanks,

p.
Click to expand...
IGBT's here's a few:
http://www.onsemi.com/site/apps/summary/0,4460,,00.html?id=604

logic level so I'd think you can drive them directly with an mcu,
build-in ~400V clamp so you won't kill the coil in case the spark
plug wire is removed etc.

-Lasse
 
Get the real thing: an IGBT made SPECIFICALLY for driving
an ignition coil. For example:
http://www.fairchildsemi.com/ds/HG/HGTP14N40F3VL.pdf
My hobby is building electronic ignitions for antique vehicles.
I used the fairchild IGBT in a couple of circuits.
I've used a couple other devices from other manufacturers.
If I have the time I'll look for the part numbers.
In the meantime just search for
"ignition coil igbt" or some such.

I tried mosfets and igbt's that don't have clamping, and they
sometimes work and sometimes don't. The automotive igbt's
are your best bet.
 
By the way, what is EHT? My applications have all been simple
transistor-switched inductive ignitions. If you are using capacitive
discharge the clamping aspect might not be as important, and an
ordinary power mosfet (no clamping), with the proper voltage rating,
might work.

Old fashioned ignitions that have a set number of degrees of dwell (as
opposed to modern ignitions, which have dwell control and
low-resistance coils) will heat up a garden-variety mosfet, like the
IRF 740. If the kickback doesn't kill it. You would have to find a
high voltage mosfet with a low Rds and also be stuck with having to
make a clamping circuit using discrete components to protect the
mosfet.
 
On 25 Nov 2004 14:16:43 -0800, kellrobinson@yahoo.com (kell) wrote:

Get the real thing: an IGBT made SPECIFICALLY for driving
an ignition coil. For example:
http://www.fairchildsemi.com/ds/HG/HGTP14N40F3VL.pdf
My hobby is building electronic ignitions for antique vehicles.
I used the fairchild IGBT in a couple of circuits.
I've used a couple other devices from other manufacturers.
If I have the time I'll look for the part numbers.
In the meantime just search for
"ignition coil igbt" or some such.

I tried mosfets and igbt's that don't have clamping, and they
sometimes work and sometimes don't. The automotive igbt's
are your best bet.
Click to expand...
Okay, thanks all! Will look into them.

--

"What is now proved was once only imagin'd." - William Blake, 1793.
 
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