I found this basic boost circuit https://www.ladyada.net/library/diyboostcalc.html but in my testing on LTSPice it would take a very long time to charge up a useable cap.. Mind you I'm not sure if I got the PULSE settings right, I used PULSE(0 5 0 1n 1n 15u 31u) for ~31kHz 50% duty cycle.
Then I had a thought, what about a centre taped transformer driven from a pic to generate a ~120VAC output on the secondary and then rectify that back to DC, filter it and use some sort of charge resistor and fet to control the rate of charge of the cap and prevent charging once it reaches a desired level? What you think? pretty convoluted but would probably provide the fastest method of charging a cap with any voltage up to ~120VDC or higher if I wound the transformer for more...
Then I had a thought, what about a centre taped transformer driven from a pic to generate a ~120VAC output on the secondary and then rectify that back to DC, filter it and use some sort of charge resistor and fet to control the rate of charge of the cap and prevent charging once it reaches a desired level? What you think? pretty convoluted but would probably provide the fastest method of charging a cap with any voltage up to ~120VDC or higher if I wound the transformer for more...
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