I'd like to build a driver circuit that, as simply and economically as possible, takes 120VAC input and drives a variable DC load at a relatively constant .85 to 1.0 Amps peak. The output voltage would have to vary from 20 to 90 volts to deal the load changes and maintain the ~1 amp current flow. Ripple and a little noise is not a problem. Load is resistive (not inductive) and changes very slowly. I'm picturing a basic bridge-capacitor supply feeding a power MOSFET or IGBT circuit that is biased using a shunt (sensing?) resistor. I'm an industrial electrician and haven't done this kinda thing in about 15 years. I was hoping to find some example schematics that might help, but I'm coming up empty handed after about 2 hours of googling. Can anyone help?