Switching inverter help

Discussion in 'General Electronics Chat' started by Veracohr, May 17, 2014.

  1. Veracohr

    Thread Starter Well-Known Member

    Jan 3, 2011
    For the project I'm working on, I made a power supply that took +15V from an external supply, inverted it to -15V, followed by +/- 12V linear regulators.

    I used a Texas Instruments tool to design the inverter, but it's not working right. The first attachment is the schematic the software gave me. The second schematic is the one I made the PCB from.

    Instead of -15V out, I get a ramp waveform that goes from about -1V to -3.5V, and has a frequency that rises from about 2kHz to about 5kHz in a few hundred milliseconds, then it's 0V for a few hundred milliseconds, and repeats like that.

    Could the addition of the linear regulator and associated capacitors be screwing things up? The +12V out of the 7812 is fine. I've checked and re-checked and re-re-checked the traces to make sure, and I connected everything correctly.

    Any ideas?