Digital highvoltage distributor

[libbresse]

igbt ignition circuit

I want to build a distributor to my ignitionsystem in my dragrace snowmobile.

Would like to have input on the sketch I have done if it is good enough or if I should build it different.


circuit:
**broken link removed**

coil driver:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRGSL14C40LPBF-ND

 

[FvM]

digital distributor

It's not actually clear, what your asking for. The principle of individual driven ignition coils is pretty clear and widely used in recent cars, I think. The sketched circuit details are rather dubious, involving wrong IGBT polarity, inappropriate supply voltage, not operational gate drive. Basically, present IGBT ignition solutions imply a 12V primary supply voltage and common emitter IGBT configuration, see a principal schematic from a fairchildsemi automotive application booklet.

 

[snafflekid]

www.tope pixbox.se

I know the IGBT spec says 430V but it takes much higher voltage to generate a spark--aprox. 10,000V. You generate that high voltage by a step-up transformer, as shown in the schematic by FvM. Leakage inductance can cause some voltage flyback on the primary side so the IGBT needs to withstand some high voltage spikes, hence 430V spec.

Maybe you can retrofit an aftermarket pointless ignition system?

 

[libbresse]

programmable digital ignition circuit scheme

FvM: Wow that was hard words on my nice circuit I have changed the circuit by your scheme.
what do you think now then ?

snafflekid: The coil is driven with 530 voltage MSD ignition system, the only thing that my circut does is point the spark to the right cylinder, MSD does the timing when the spark should come.

**broken link removed**

 

[FvM]

pointless ignition schematic

I couldn't see, if the circuit has been intended as real design or a principle schematic only. So I just wanted to point to some details, that seemed incorrect to me.

I was referring to a usual standard circuit instead, that is using a 12V supply and operates the ignition coil in flyback mode. This is equivalent to a traditional mechanical ignition timers operation. On contact opening, a flyback voltage of several 100 V is present at the switch, without a high voltage supply.

There are also circuits, that operate the ignition coil in forward mode from a high voltage supply. They are supposed to give a stronger ignition spark. I'm not aware of their usage in recent cars, I know that they had a high time in the 70th and 80th. I understand that the MSD system is of this type.

However, the gate drive isn't operational in the new cicrcuit to my opinion. The gate voltage has to be referenced to the IGBT emitter and keep an alowed +/-15 range to avoid IGBT damage. You circuit immediately destroys the optocoupler and the IGBT. Furthermore, an IGBT gate should be controlled by a low impedance driver for suitable switching performance.

 

[libbresse]

pointless ignition retrofit

FvM: Ok so do you think that i can solve gate to emitter reference with 2 zener diods ? And also what type of element do you think that I should use instead of the optocouplers ?

 

[FvM]

+igbt +ignition +coil

i can solve gate to emitter reference with 2 zener diods ?

I haven't been talkink about zenerdiodes, but feeding a correct voltage to the gate. Zenerdiodes are used as an additional protection. The IRGSL14C40LPBF has internal protection diodes, as the datasheet reveals.

I have no particular suggestion for a gate driver, you can use dedicated driver IC, drivers assembled from individual transistors, also optical isolated IGBT drivers are available. I don't want to start a design, just point to some problems.

P.S.: I see, that the IRGSL14C40LPBF has a rather low input capacitance of about 0.5 nF. So the gate drive hastn't to supply high currents. But at least some kind of push-pull driver should be provided.

 

[libbresse]

+igbt +ignition +coil +circuit

FVM: Now I have read lots and lots and hope that i have found a good gate driver:

fan3111e
https://www.fairchildsemi.com/ds/FA/FAN3111C.pdf

Comments, good bad :?:

 

[FvM]

distributor/circuit

Very good!

 

[libbresse]

ignition igbt schematics

FvM: Thank you alot for your help

Now I'm thinking about how to take care of the signal from the hall-sensor, thinking of some comparator that reads the voltage and send a digital signal to the microprocessor. do anyone have any other idea :?: