igbt gate drive issue

Discussion in 'The Projects Forum' started by jbest, Jan 9, 2009.

  1. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    Hello i am building an igbt gate drive and i cant seem to get it to work i am using parts that were recommended by some one else as i have no real electronics knowledge to speak of



    I am using a 7406 hex inverter ,acnw3130 opto igbt gate drive and igbt g4bc20f

    I have attached the pdf for both of them. In the ancw3130 pdf circuit number 29 is the exact circuit i have built except pin 6 of the opto isnt connected and i am running a 2 amp 15 volt supply to it

    Any help would be most appreciated thanks james
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    How about the 7406? Anything above 6 volts and it's toast.
     
  3. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    beenthere The 7406 has its own 5v supply

    The system work fine up to the opto
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Can you place a constant input to the optoisolator and verify that the IGBT is in full conduction?
     
  5. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    i bypassed the opto and touched the gate directly to the power supply for the opto and the igbt wouldnt turn on i believe the igbt needs more than the power supply and opto can deliver but i dont know how to read the data sheet correctly to confirm this the igbt
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    If the IGBT gate is more than 10 volts above the source and it's not conducting, it's because the device has failed. The turn on and off rates are dependent on the rate your driver can move charge, but no power is involved with turning the device on and off.

    Gate voltage 0 with respect to the source - no conduction. Gate 10 volts above the source - full conduction. Make sure you have correctly identified the gate, source, and drain pins.
     
  7. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    i am using the right pins 1 gate 2 collector 3 emitter

    so if i am putting 40 volts into the source pin the i would have to trip the gate with 50 volts

    if so i am only putting the 15 volts from the isolated circuit into the igbt and it will never work

    do you know where i can find a schematic of circuit with part numbers i can copy

    i am wanting to chop up a half wave dc just like a pulse converter dose
    i have a 555 square wave circuit up to the 7406 done but the opto isolater and igbt portion is a problem for me and if what i am interpeting from your last post is correct than this is wrong design for me
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    Can you post up the schematic of the circuit? That way we might be able to make more suggestions as to how to overcome the difficulty.
     
  9. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    beenthere i have attached a pdf containing the drawing of the circuit
     
  10. mik3

    Senior Member

    Feb 4, 2008
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    Connect the emitter of the IGBT to ground and connect your load between the collector of the IGBT and the positive of the rectified supply voltage. Also, you need to power the opto with 12 V or more as to be able to turn on the IGBT. What is the part number of the IGBT?
     
  11. nanovate

    Distinguished Member

    May 7, 2007
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    1
    it will work but the voltage must with respect to the emitter. What is your emitter (pin 3) connected to? Try connecting it to pin 5 of the optocoupler.
     
  12. beenthere

    Retired Moderator

    Apr 20, 2004
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    Either that. or place the load between the voltage source and the IGBT so the IGBT switches to ground as in post #10.
     
  13. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    mik the igbt is part number g4bc20f their is a pdf attached to the first post of this thread

    nanovate the pin 3 emitter is hooked to the inductive load will it cause damage to the opto isolater if i hook it directly to pin 5 and the inductive load

    beenthere i tried hooking the circuit to groung as you said prior to this using an scr and it made the power supply hum like it was causing damage thats what made me move on to this
     
    Last edited: Jan 10, 2009
  14. mik3

    Senior Member

    Feb 4, 2008
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    Connect it as I told you in post #10, place the inductor between the collector and the rectified voltage and make sure you have a fast diode across the inductor as to absorb the back EMF when the IGBT switches off. Also, you need to apply more than 10V between the gate and the emitter to turn it on. The maximum gate-emitter voltage is 20V.
     
  15. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    i just tryied as in post 11 and the power is now going thru except it isnt pulsing i remove the trigger wire to the opto and remained on


    mik3 i will try it as you said will be back in a moment
     
  16. mik3

    Senior Member

    Feb 4, 2008
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    Post #11 says the same as me because pin 5 of the opto is essentially connected to ground.
    Also, connect a 10K resistor between the gate and the emitter as when you remove the signal from the gate the IGBT will turn off. If you don't do it the IGBT will turn off slowly and go into the linear region and you it may get destroyed.
     
  17. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    i dont know whats wrong here their appears to be multiple problems :(
    im pretty discoraged ive been messing with this for months on and off

    the igbt is turning it self on with nothing attached to the gate the opto isolater isnt doing anything on constant 15.10 volts

    all i was trying to do is push a high amplitude wave into the inductor to force it to ring creating a force resonance ringing wave ,transient spike , and a steping up and down pattern that matches the half wave dc it just wont happen for me

    :confused:
     
  18. mik3

    Senior Member

    Feb 4, 2008
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    Are you sure you have connected the IGBT with the correct pins?

    Did you connect the 10K resistor between gate and emitter? I suspect you connected it between gate and collector.

    Check if your oscillator works and if the opto outputs a signal without thr IGBT connected to it. Test the IGBT if it turns on/off when you apply 15V with a wire directly.
     
  19. jbest

    Thread Starter Active Member

    Nov 18, 2008
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    0
    i replaced the opto with a new one im not sure how this opto isolater works i put a scope on the output and it is on constant dose this opto need to have the igbt and resistors attached to turn of

    i checked at the input to the opto and has a square wave going to it

    and 13.75 constant out of the opto couple and never turns off
    i would say thats the first problem i have to fix

    the 7406 is feeding directly into the the opto along with a 270 ohm resistor from the 5 vcc i disconected the resistor and measure voltage into the opto and the voltage to opto was.703 just from 7406 with the resistor on the voltage was 1.56 i measured the voltage with resistor hooked to thw vcc was comming out resistor was 4.96
     
    Last edited: Jan 10, 2009
  20. mik3

    Senior Member

    Feb 4, 2008
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    The 270 ohm resistor has to be there because the inverter has an open collector output. But why you don't connect the output of the 555 to the input of the opto via a resistor?
    What value is the resistor going from the output of the opto to the IGBT?
     
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