/diy/ - Do It Yourself

So I'm testing a variable duty-cycle buck converter, and I've hit the snag that I though I would. Namely, the feedback voltage is smaller than the voltage set by the potentiometer, so the differential amplifier is feeding the comparator a voltage within the bounds of the triangle wave, but the resultant duty cycle isn't enough to get the output voltage up to the desired level. Since the output voltage doesn't change, the feedback voltage doesn't change, so the duty cycle doesn't change, and this sag / undesirable stead-state would happen to some extent regardless of what load I put on.

Pic related, but it's kinda awful. Oscillator voltages, feedback voltages, and potentiometer voltages are all set to vary between 2V and 3V, which I assumed would give me plenty of room compared to larger ranges. If the output voltage is higher than what I set it to be then the comparator should shut off completely, and if it's 340V too low then the comparator should turn on 100% of the time. Some funky low value resistors are there just for ensuring the transistors turn on quick enough.