Creation of a Negative Rail from One Positive Output
Hello all. I have since prototyped a circuit that allowed me to create a negative rail from one single, positive output. The transformer was designed to produce only one positive output. By rectifying the negative portion of the output switching waveform and filtering, then zener regulating, a low current (10 mA max) negative rail can be produced that is stable over load. This allows the addition of op amps now that have dual rail supplies, etc....
I am looking for any feedback or thoughts on this approach. One thing I did notice is that without the 22 ohm resistor, the supply will not start up. Is this due to initial current spikes into the filter capacitor cause the controller to shut down? If so why wouldn't this occur on the positive output as well?
The rectified unregulated voltage on the filter capacitor is around -22 VDC. Ripple is within 10 mV under load (10 mA).
|circuit schematic with addition within red lines||110.79 KB|