Hey OT:

I did a google group topic word search for "low pass filter" without the quotes and good here. brings back memories.

Well I have a 1,300 watt SMPS from a Panasonic microwave oven. Cost was 44 USD as a replacement board there was no dud costs and it is a new board not a rebuilt. Even though it has a flyback transformer, they used a doubler to get to the 4kv that the magnatron needs.

I took the gate of the IGBT out of the circuit and using a 555 timer with independent timing controls and a 4 Amp IGBT driver I applied that signal to the gate of the IGBT.
The optimized signal produced by the 555 was 33khz with a 25% duty cycle, which gave me a 2,750 vdc output with a 2ma load.
Any other frequency or duty cycle, produce less than 2,750 vdc.
Rated at 1,300 watts. And I was only using half wave rectifier as I took out the doubler circuit and used 8 pieces of 560uf 400wvdc capcitors in series on the output.

Now I am fiddling with charge pumps and with enough high voltage disc ceramic capacitors and a full bridge switch running at 100khz I am looking to take a 12.6 vdc battery and pump it up to 1.5 kvdc for a strip line tube amp for 2 meters, using 3cx400u7 tube.

73 OT
de n8zu