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Generating uni-polar PWM signal using IR2113

Discussion in 'Homework Help' started by Ng Jing Xi, Nov 13, 2013.

  1. alec_t

    alec_t Well-Known Member Most Helpful Member

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    With Hi-in and Lo-in strapped together, won't Q1 and Q2 turn on at the same time and short the supply? (Likewise Q3, Q4). According to the datasheet the IC outputs are in phase with their respective inputs.
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    This thread is very confusing since the power supply is a mess and the 'scope photos are not labelled.
    Post #105 and post #118 shows what might be the gates of the HIGH and LOW devices IN PHASE but the schematic has one of them inverted.
    Post #122 shows the two inputs of the IR2113 connected together and the gates are still in phase but their signals look more normal.

    The IR2113 is made with bootsrapping so that the HIGH device can be an inexpensive N-channel device like the LOW device. Then why isn't it made with one input inverted?
     
    Last edited: Jan 16, 2014
  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I guess having uncommitted inputs adds versatility, e.g. for additional dead-time control; or if, for some strange reason, you wanted to 'cross-wire' an H-bridge so that one IC drives top left and bottom right while the other IC drives top right and bottom left.
     
  4. dave

    Dave New Member

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  5. Ng Jing Xi

    Ng Jing Xi Member

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    I connect my circuit according to the one you edited. The VDC powering up the IGBT is around 14V but this is the output I got.
    I used a differential probe to measure the output waveform. The frequency measured is 50Hz. And the reading is Vrms.

    Given that my VDC is 14V, I should get a 28V peak to peak? Or am I wrong?
     

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  6. Ng Jing Xi

    Ng Jing Xi Member

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    Yeah. The intented H-bridge is that the alternate IGBT are switched on [Top Left, Btm Right] while the [Top Right, Btm Left] turns off.
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Sorry, my circuit is wrong.

    You completely forgot about the saturation voltage loss. I could not find the part number of your IGBT's since it is not on your schematic. A typical IGBT has a saturation voltage loss of 2V at a current of only 5A. Then with a 14V supply the output will be 24V p-p and the IGBTs will be hot.
    Mosfets are excellent when the supply voltage is low. IGBTs are better than Mosfets when the supply voltage is very high.
     

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