Re: Mariss' power supply circuit

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:

> Les,
>
> I appreciate you taking the time to understand the circuit. The
> PWM modulation is actually a linear function of the over-voltage
> seen by the supply. The amplitude of the 120 Hz sawtooth (R2,C1)
> is set to about 2V peak-to-peak, this being the "regulation"
> range of the circuit. The "trough" of the full-wave rectified
> reference clamps the negative excursion of the sawtooth to the
> difference voltage.
>
> Mariss

Hi Mariss:

I was studying the circuit, and I must be missing something.
Looking at the waveforms, the signal labeled "Voltage on R1".
This looks like it would be the voltage across R1, not the
voltage from either end of R1 to ground, correct? The voltage
on the bottom of R1, with respect to ground, should be inverted,
with the "pointy" parts at the power supply output voltage, and
the "rounded" parts down near ground (at ground when operating
normally, 2V higher when clamping). The circuit would still work
as described, but the C1 voltage would be pulled down at the peak
of the transformer voltage, not the valley. What am I missing?

John Kasunich