need help limiting current with IGBT

[oneprint]

hi
i have a ignition coil hooked up to an IGBT. the power supplied it from a car battery through an inverter and recified to 340 vdc.
Can anyone tell me how much current will flow through this circuit. and how i can limit it? i will be using a low duty cycle. Basically how does the
ignition coil limit the current?

And is there a way to limit current while still allowing the full Voltage to flow through the circuit?

thanks in advance

 

[FvM]

There are basically two concurrent methods to drive an ignition coil.

Traditionally, a mechanical contact is operating the coil in flyback mode. In this mode, the coil resistance is limiting the current at low speeds. Recent electronic ignition circuits are still maintaining the low supply voltage and replacing the mechanical switch with a transistor or IGBT. In a modfied variant, the ignition coil has a lower resistance and is driven with controlled on-time rather than fixed duty cycle. This requires an electronic control circuit, that can predict the ignition time by knowing the crank angle at each time, an information that is generally available with modern motor controllers.

Alternatively, the ignition coil can be driven by a high voltage, e.g. powered from a capacitor. In this case, the switch (traditonally a SCR)is closed at ignition time.

In other words, the intended control method, switching a high voltage for a longer time doesn't make sense at all.

 

[atripathi]

You can also have mechanism implemented to turn off the IGBT, when current crosses a predefined threshold.

 

[oneprint]

You can also have mechanism implemented to turn off the IGBT, when current crosses a predefined threshold.

Sorry for the late reply, i have been busy recently.

how can this be done? i will use 330 VDC and high voltage capacitor to discharge into the ignition coil. from the replys i have heard you can limit current through the ignition coil and IGBT by controlling the turn on time. Is that correct?

If this is so does any one have the equations for current and voltage flow through a circuit in given on

i assume then when the circuit is off the IBGT will still have to dissipate the current some how?

i hope some one can help me!!

thanks in advance