I have designed this chopper circuit. I used a bootstrap circuit using an avr PWM to boost the voltage for driving an NPN mosfet on the high side.
I have on order the IRS2186 mosfet driver i will actually use.
The question I have is how do I keep the Q1 mosfet gate low while the rest of the board powers up. If the Q1 mosfet gate has built up some capacitance and is high initially the load will get a high voltage current spike when initially powered up or at least until the 2n7000 gate goes high and shuts off Q1.
I have a TLP597 ssr N.C. relay i planed to tie to Q1's gate and use the AVR to turn on the circuit when voltages have stabilized. What alternative solutions are available to accomplish this?
I also have on order the TL783 adjustable regulator that has an input voltage maximum of 125VDC to handel up to a 100VDC input. I plan to use this chopper with my own universal stepper motor driver. I have some slo-syn 20 amp steppers 1100oz/lb
There is only 1 sense resistor, I put two spots since I have both through hole and surface mount versions.
I also wanted to mention I used a 10K resistor and a 10uf capacitor to slow the voltage swing down since the comparator was switching faster than the mosfet could switch. Perhaps it would be better to use the AVR comparator and do a specific blank time, not sure about that.