driving mosfet/igbt

Discussion in 'The Projects Forum' started by damjanmi, Apr 23, 2009.

  1. damjanmi

    Thread Starter New Member

    Apr 23, 2009
    4
    0
    Hi,

    I'm making project where I want to control flash duration with help of MOSFET or IGBT (I will be switching xenon flash bulb in and out of the circuit). I have never used MOSFET or IGBT and I do not know how to drive them. I wan't to drive them with microcontroller (avr) and driver ICL7667. Must I drive MOSFET with some frequency or can I drive them as normal transistors? I read that I must apply around 12V to the gate of MOSFET/IGBT if I wan't MOSFET/IGBT to be fully on?

    Is it enough to connect output pin of avr to pin 2 of driver, pin 7 of driver to gate of MOSFET, pin 3 of driver to GND, pin 7 of driver to VCC?


    Damjan
     
  2. -SK-

    Member

    Apr 14, 2009
    25
    0
    If your load, and the fets you use are small enough, you might be able to drive them directly from the microcontroller. Otherwise, yes it will work fine using that driver IC, except you might want to connect pin 6 to Vcc instead of pin 7 :D. Use the circuit recommended in the datasheet.
     
  3. damjanmi

    Thread Starter New Member

    Apr 23, 2009
    4
    0
    I meant pin 6 to Vcc. There must be something wrong. I connected driver to IGPT as in datasheet, when I open IGBT (driver is connected to 12V) and fire flash the light from flash is not as bright as if I connect xenon flash bulb directly to Gnd. And driver was destroyed - it was very hot. Where could be the problem?

    Can I drive IGBT without using a driver (maybe with transistor)? Any schematics?


    Damjan
     
    Last edited: Apr 24, 2009
  4. damjanmi

    Thread Starter New Member

    Apr 23, 2009
    4
    0
    I made a quick sketch of my circuit. Does anyone have any pointers regarding my problem?
     
  5. -SK-

    Member

    Apr 14, 2009
    25
    0
    The light is not as bright because there is some voltage drop across the IGBT, reducing the voltage dropped across the load.
    If your driver is blowing up, you are probably exceeding its power dissipation limit. The datasheet gives 200-400mW as the max power. Look in the datasheet under 'power dissipation' on page 4 and you can make a rough estimate of how much power you are putting through the driver. Try putting a buffer between your driver and the IGBT gate, or using a switching device such as a mosfet that requires lower voltage or current to turn on.
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Where is the bootstrap capacitor of the driver IC?

    If you have a logic level MOS (turns fully on when Vgs=5V) then you can drive it directly with a microcontroller. However, this is not a good idea because it won't switch on/off very fast, spend a significant time in the linear region and get hot. Thus it is better to use a driver IC or a BJT to drive it.

    It is not necessary to use PWM to drive it, you can use a continuous signal if you want.
     
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