/diy/ - Do It Yourself

I'm making a High Voltage PSU and I need some kind of power control to make the high voltage output adjustable. (See pic related)
I was thinking about 555 PWM control with a MOSFET adding some big chunky caps to smooth the power going into the driver's MOSFET and finally to the transformer. The PWM would vary the amount of power going in quite efficiently, but I'm afraid the signal from the PWM interferes with the switching of the driver's MOSFET. The driver will be running at 15 to 30kHz, so I thought I should make the PWM run at a higher frequency, maybe 50 to 100kHz. ¿Would there be a problem with this setup?
I also thought about an LM317 and a TIP3055 BJT to act as some kind of heavy duty variable resistor, but I think this would be less efficient than the previous solution.

The high voltage output doesn't needs to be too clean, I'm not going to use it for precision stuff, just burning things up and making random experiments.