IGBT ignition coil driver

[Rleo6965]

That sounds like an interesting project. I hope that you start a new thread. I built a capacitor discharge ignition, but it only puts out one spark if I remember correctly. But it was over 9000v! I don't know how much over because my tester only goes to 9000v. I wish I had scoped it to know for sure. What are you using the circuit for?

I'm using my multiple spark cdi for my Mitsubishi Car Lancer w/ carburated engine. I think I have the clue to solve ground noise problem of my project .

 

[Rleo6965]

15us is a long time. What many people don't pay attention to is the inductance of the drive circuitry.

One thing I have learned in the Pulsed Power business is that R and C are your best friends, but L is like your freaking ex wife!

To turn on an IGBT, you are essentially charging the Miller Capacitance of the gate.

You need a high current driver (TC426 or TC427) and you have to make sure the supply to the driver has a very low ESR Capaitor with the stored energy to hit that bastard gate as hard and as fast as you can.

You need to charge that gate as fast as possible. And you also need to turn off that gate just as fast! That is why a lot of IGBT drivers, (unlike MOSFET drivers) swing from +18V to -18V.

Don't bother reading those silly "Threshold Voltage" numbers.....they are talking about the linear range.....which is where you want to stay out of when switching. That's where the heat builds up in the die.....and the smoke comes out if you stay there too long.

Hope this answers your questions.....

After reading your post. I look again the schematic diagram of my multiple spark cdi project. I think , I can now solve the intermittent misfiring due to high current electrical noise in ground and dc supply circuit.
Thanks for the tip.

 

[BitHead]

How about something like this?

Or better - add a .1uF cap in parallel with R4. That'll suck that Miller capacitance out.

 

[(*steve*)]

That circuit doesn't provide a low impedance path to ground to ensure rapid switching off of the IGBT

 

[mmcl055]

Right, I'm getting back into this now. I've fixed a few things up on the scooter leaving the ignition as the one thing which is causing it to run badly. Replacing the points is not really an option because the bike is 60 years old and no one makes them any more. So this circuit just has to work!

I figured I should throw away the ignition side of the circuit because I was approaching it all wrong. I think I may have found a component which'll make things a lot simpler: Bosch BIP373 ignition coil driver. It's designed to drive an ignition coil from CMOS.

Here's the datasheet: http://www.megamanual.com/ms2/bip373_datasheet.pdf

Which means I can greatly simplify my circuit to this (I think):

What do you guys think? Am I mental? (probably)

I'm unsure of my resistor value on RB3.

 

[mmcl055]

Or better yet, this?

 

[BitHead]

I'm not so sure you want to slow down the trigger signal with that cap to ground after your 1K base resistor. Putting it in parallel with the 1K would better - faster turn-on and still provide some noise filtering (assuming pin 9 is a push-pull drive pin).

 

[Rleo6965]

If you want to protect 16F628A in event BIB373 was shorted. Place 1N4148 or equivalent in series with 1k resistor and connect 56k resistor in replace with 1n capacitor. Connect anode of diode to output pin of controller.

 

[mmcl055]

Ahh cool. Thanks for the tips!

I've updated the schematic with your suggestions. I'll give it a whirl this weekend.

 

[Rleo6965]

Diode should be in series w/ 1k resistor not in parallel.

 

[mmcl055]

Silly me! I read series, but for some reason I thought parallel!

I've updated my schematic. Thanks.

 

[Rleo6965]

That diode surely give you peace of mind if transistor and driver becomes shorted.

 

[BitHead]

When I was playing with sparky things and micro-controllers together, one of my lessons learned was 'Do not trust a uC to be able to turn off what it has turned on.' You may want to see if replacing the series diode with a 1uF cap will get it to spark nicely on a rising edge only.

 

[Rleo6965]

Signal turn off will be done by pull down 56K on base of transistor. uC only turn on the transistor.

 

[BitHead]

Yes, it will work just fine. That BIP373 is a bit 'armored' - it can stand a wigged-out/hung-up controller drive pin. ;-)

 

[debe]

Way back in this thread is a picture of the setup & its wiring. The spark plug should be earthed to the ignition coil not the power earth. Set up like that the HV spark is likely to destroy the circuitry.

 

[mmcl055]

Hi guys,

I'm definitely getting closer! The circuit will fire the coil correctly, however the chip resets as soon as the coil fires.

I only have a cheap multimeter but it looks like there's some high voltage being introduced somewhere. Do I need a condenser (or cap) to capture this perhaps?

 

[Rleo6965]

Electrical noise disturbing your +5V supply. Increase your 220 mfd 25V to 1,000 mfd 25V or higher and if your using plastic casing. Temporary wrap it w/ aluminum foil and ground the shield aluminum foil to ground using alligator clip. Just to isolate problem. If this correct the problem. Use metal casing.

Use actual car battery to supply your circuit and use bigger wire gauge for +voltage and ground wire.. This might correct problem.

 

[mmcl055]

Hey Rleo6965,

Thanks for your help so far! Much appreciated. I tried the things you've suggested with no luck.

Any other ideas? I'm still think I'm seeing some spikes in voltage on the multimeter.

 

[Rleo6965]

It's really hard to eliminate noise especially in +12V side of Ignition Coil due to high charging current. All we can do was to minimize noise on +5V side in PIC to avoid reset problem. Try solder 1,000 mfd 16V and 0.1 mfd in parallel with +5V etch or VDD of PIC.

Can you post final circuit diagram and pcb layout top and bottom.