http://sound.whsites.net/project89.htm

I made this schematic. Worked.
VR1 adjusts the output voltage


You can adjust the output voltage using a reference voltage (E.g. +5V pin Vref) instead of output voltage(+35V)?

 

I would say no, but I'm looking for a solution.
Because primary current insensitivity increases quasilinially.
Faraday Uout=-d f/dt it should have the same output voltage regardless of the duty cycle.

Actually I want to give up the output capacitors to allow the output voltage to vary in short time.

Actually.....
I want to put on SG3525's reaction pin a signal which I hope find it on the output.

I want to build a voltage source for an H class amplifier.

Maybe it's another stupid idea of mine. But I'm ready to risk and burning components.

 

Yes very good, we know how this chip works, why don't you run mosfets directly from the chip, you dont need transistor buffers, you alter the output voltage by presetting the reference voltage on the opamp and compare it to the output, ideally using an opto-coupler and zener.

 

Yes very good, we know how this chip works, why don't you run mosfets directly from the chip, you dont need transistor buffers, you alter the output voltage by presetting the reference voltage on the opamp and compare it to the output, ideally using an opto-coupler and zener.

75A MOSFETs ganged in pairs will be a fair bit of gate capacitance for the integrated driver transistors.

Most people use a TL431 to drive the opto coupler. The output voltage goes to a voltage divider that puts 2.5V on the TL431 control pin - the whole SMPSU is one big nfb loop, so the comparator in the 431 operates in linear mode.