Want change Darlington to IGBT in circuit

Discussion in 'General Electronics Chat' started by wind77, Aug 5, 2016.

  1. wind77

    Thread Starter New Member

    Jul 21, 2016
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    Hello all!
    I am wanting to use IGBT in place of Darlington NPN(Q1) in my circuit. In the schematik I show below outline in dotted line red is darlington NPN I want to replace(bub941zt). I want to use IGBT of this: Isl9v3040d3s.
    Can you help me to change this circuit to use IGBT for "Q1"? I know IGBT is voltage driven and darlington is current driven. Ca 100_0246.JPG n I still use BC337 npn transister to drive IGBT or is there other way?

    Lisa
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Depending on how fast you need to switch the IGBT on/off you can just swap the Darlington for the IGBT and leave the rest as is.

    Edit: No, can't leave 'as is'. The gate voltage needs to be <10V.
     
    Last edited: Aug 6, 2016
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    That 100 ohm resistor in the Q2 collector seems awfully low. What is the peak current through the Q1 collector?

    ak
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Agreed on the 100Ω. If the IGBT is switched slowly you could use a higher value (say 1k or more). If it's switched very rapidly you could consider using Q2 as a level-shifter to drive a push-pull stage for charging/discharging the IGBT gate.
    However, I've just noticed the 14V supply voltage is greater than the maximum rated gate voltage (10V), so you'd also need to drop the voltage applied to the gate.
     
    Last edited: Aug 6, 2016
  5. wind77

    Thread Starter New Member

    Jul 21, 2016
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    Thank you all for helping me with this. I concerned with the gate mostly as I have not used IGBT before. I think peak current thru Q2 collector is .140mA to drive darlington. I will not drive this IGBT more than 400hz. Do I need consider level shifter if I lower gate voltage to about 9v and should I have gate voltage near max of 10v for maximum drive?

    Lisa.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    Most power MOSFETs can stand about 15V on the gate - but that's about the breakpoint where it starts to reduce the life expectancy. The ABS-MAX ratings are typically around 18 - 20V ish.

    You can of course shunt the gate with a Zener - the drive circuit is a transistor with a pull up resistor, so nothing will be harmed.

    The 100R resistor could be increased to at least 1k so a lower rated Zener can be used.

    Somehow this looks like an ignition coil driver - a high voltage power MOSFET in grounded gate configuration works well; tie the gate to Vcc and switch the source with a low voltage, low RDSon high current MOSFET.

    Low RDSon high voltage MOSFETS are rare - an IGBT may be the answer for the common gate section. A MOSFET can lose a lot of its advantages when the battery sags under cranking current.
     
  7. Alec_t

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    Sep 17, 2013
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    A level-shifter is needed if your driving signal source is a 5V MCU. According to the datasheet for that IGBT the Absolute Maximum gate voltage is 10V, so I wouldn't risk driving it above 9V.
     
  8. wind77

    Thread Starter New Member

    Jul 21, 2016
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    I take more time and redesign schematik using IGBT now. From I understand this should drive IGBT(Q4) more better. I list components I use in bottom left of my schematik.

    Lisa DSCF0001.JPG
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Q4 gate has no pull-up.
    If it were me I'd try something like this :-
    IGBT-driver.JPG
     
  10. shortbus

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    Sep 30, 2009
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  11. wind77

    Thread Starter New Member

    Jul 21, 2016
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    I had crossed my mind on this but was not sure. I look and find this. I am away and can not schematik draw at moment. But this part: MC33152 work may?

    Lisa
     
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