Interesting designs. Thanks for the info. I will analyse them when I get a few minutes. I'm always interesting in switching supply designs.
I've built a couple of flyback ones in the past, one crudely breadboarded here. This little bugger, powered by a 555 and LM311 and IRF510 (does the job!) managed to kick out 75v @ 300mA quite happily which is to be quite frank, scary, especially as the max Vf on that diode is 40v and the output cap is 50v rated! This could be replaced with a 34063 and a slightly wimpier MOSFET I reckon. Operation is the LM311 compares the output voltage ratio against a dumb zener reference and turns the 555 off with the reset pin if it is on the mark. Similar operation to the 34063 but larger, more expensive and more complicated.
You can see the burn marks on the board at the bottom right when it went overvoltage when there was a bad solder joint and the divider fell off (
)and was discharged with a screwdriver and some croc clips.
I have another design in flight which was a dumb experiment to generate typical electrostatic CRT drive voltages which uses an E42 core with two TIP41C's in a multivibrator configuration with two primaries of opposite phase. That is already kicking out a selection of nice voltages but the efficiency is completely boiled shit. Sucks up 600mA idling and sounds like someone is murdering a dolphin when under load. Did some maths wrong when calculating the reactance of the primaries me thinks and the frequency is way too low. Needs to be >20KHz.
For ref, I built the 34063 into it now on a little daughterboard (stripboard - kill me) that slides into the steaming holes left by the 78L05 and it's working nicely. Total efficiency is around 82% on the final device which is good! 12mW versus 180mW when idling away now. BIG improvement. Means that SLA will last 10-15x as long before I have to charge it (currently monthly).
This is far more fun than the day job