I have the circuit below, which generates 1.5kV from a transformer. The primary is driven by a MCU oscillator, mosfet driver and a pair of n-channel mosfets. It works very well as it is:
But now I need to make it stabilized: output voltage must be constant with a varying load.
The best approach, in my opinion, would be to take advantage of the LM350 adjustable regulator I use to feed Vcc to the circuit: if I could get a sample of the output voltage, using a simple voltage divider, and use it as a negative feedback to the LM350, I could make it react to any change in load. The primary voltage would change compensating changes in load, making a closed loop that would create constant voltage at the output.
The problem is: I have no idea on how to do it. I know how to adjust LM350 output using a potentiometer, but can't figure a way to use my divider voltage as a negative feedback. An additional detail to note is that the feedback voltage is negative in relation to ground (which may help, since the feedback is negative, or it may make things more complicated). And more than that: is this approach good? Is there a better way to do it?
Another concern is to prevent the regulator from going over a given voltage (18V for example) if the load is excessively high. From this point on, the load voltage would not be stabilized anymore, to protect the circuit.