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Thread: IR2153 HO doesn't switch

  1. #1

    IR2153 HO doesn't switch

    I'm building an IR2153 SMPS and I have a problem with the controller. HO doesn't switch, it stays high and blows the transistors. LO switches fine. I measured it both ways just to be sure:
    - with HO referenced to GND I get HO high and no switching
    - with HO referenced to VS (with an isolated scope, no diff probe, single channel) I get nothing
    I also found the bootstrap diode was short circuited after the first power-up and replaced it. The weird thing is that I tested a handful of chips and they're all the same, so either they're fake or I'm doing something wrong.

  2. #2
    Hi, I faced the same problem earlier. But that was my fault. I forgot to connect the VS pin (pin#6) to the center point of the two FET's. The bootstrap diode and capacitor was connected to pin 6, but not to the MOSFET. It was floating, and this problem occurred.
    I don't know about your circuit, I'm just sharing my experience.
    Regards,
    Sukdeb.
    Last edited by sbdada09; 03-27-2020 at 09:55 AM.

  3. #3
    .... Silvio's Avatar
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    Quote Originally Posted by bogdan2011 View Post
    I'm building an IR2153 SMPS and I have a problem with the controller. HO doesn't switch, it stays high and blows the transistors. LO switches fine. I measured it both ways just to be sure:
    - with HO referenced to GND I get HO high and no switching
    - with HO referenced to VS (with an isolated scope, no diff probe, single channel) I get nothing
    I also found the bootstrap diode was short circuited after the first power-up and replaced it. The weird thing is that I tested a handful of chips and they're all the same, so either they're fake or I'm doing something wrong.
    Keep in mind that the IR2153 has two totem poles with there output being the low side at pin 5 which should be referenced to ground and the high side being at pin 7. The high side is referenced at pin 6 which is the VS pin.

    If you want to try it on a bread board before connecting it to the circuit itself this is how you do it.

    1) connect a 1K resistor to the output pin 5 and the other end to ground (pin 4) The supply for this output is connected internally to pin 1 which is the supply pin of the IC

    2) Connect another 1K resistor to pin 7 which is the high side output pin. The supply input for this pin is pin 8 so we put the diode from the supply pin 1 and pin 8. Put it the bootstrap capacitor between pin6 and pin 8.
    The VS pin 6 is referenced to nothing so The other end of the resistor coming from pin 7 should be tied to pin 6 . You must also ground this pin 6 via another 1K resistor otherwise you will see no output from the IC on the high side. (This you do only to test the IC outside the circuit. I am assuming you are to use 12vdc to check out the IC)

    3 Connect the timing resistor and capacitor to pin 2 and pin 3 in the normal way. Put a small bulb in series with the positive supply from the power supply to limit the current in the event you hooked up something wrong.

    Connect the scope probe firstly to pin 5 and ground and after from pin 7 and ground. You should see a nice square wave coming out of both channels. If the high side does not show and signs of oscillation it means that the chip is bad. Most probably the totem pole fets on the high side are shorted.

    Lastly IF you find that the chip is good then search in your smps what you done wrong. Please note that when the IC is in the smps a bootstrap capacitor of no more than 1uf is inserted between pin 6 and pin 8. The VS pin 6 should go between the mosfets. During oscillation the VS pin is grounded via the low side fet when it switches on. This will charge the bootstrap capacitor. The capacitor will discharge when the high side signal is on and hence charges the gate of the high side fet.

    I hope this explanation is clear enough for you.
    Last edited by Silvio; 03-28-2020 at 12:33 AM.

  4. #4
    Thank you Silvio, that worked very well. Only one of the chips was actually bad, the rest are good. So now I'll check the rest of the SMPS.
    This would actually be a nice test circuit to have.

  5. #5
    .... Silvio's Avatar
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    I am glad you managed to check them at least now you know that your chip is working well.

  6. #6
    For some reason the mosfets blow up. So either there's a problem with the turnoff or a problem with the mosfets themselves. I'll probe them to see what's happening.

  7. #7
    diysmps Senior Member
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    you should use bulp lamp 40 watts for testing ... not directly to ac.. that will prevent your mosfet blow up...

  8. #8
    Ok I added a bulb and I managed to see the high side waveform which looks more like a half rectified sine wave. The high side mosfet warms up and the light bulb flickers.

  9. #9
    diysmps Senior Member
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    show me your circuit diagram

  10. #10

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