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Push-Pull Converter Help

Discussion in 'General Electronics Discussion' started by zappyton, Jun 26, 2013.

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  1. zappyton

    zappyton

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    May 20, 2013
    Today, 03:32 PM #1
    I'm trying to make a push-pull converter to take mains in (240V) and generate 3500V output to charge a capacitor.

    I've built the attached circuit, and because I kept blowing transistors, I switched it down to 24V instead, only now, instead of the transistors the controller chip (MC34025) keeps blowing. But I think it is a stability problem, because sometimes it will work for a while, sometimes it will go straight away.

    When it goes, it makes a buzzing sound (which, as it is supposed to run at 40kHz, is concerning in itself), and then something blows to short the 24V to ground in the chip.

    There is one thing I didn't fit because I didn't understand it; the datasheet says about slope compensation, but I don't know how to fit it. I think it need a slope compensation of 457V/s, and the datasheet says to make it out of resistors and capacitors, but I don't understand how. Would this cause the problems I've been having?

    Oh, when I've been running it, it's on Vero board, and the 0R050 resistor is currently a 0R47 resistor, to limit the current and the 100M resistor is 2M to try and set the output right, but it is giving out a lot of volts on the output, more than I would be expecting.

    Thanks for reading it; I know it's a long post but I wanted to be clear, but if I'm not please tell me!
     

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