I am am building a oscillator circuit for testing different transformer designs. I need the the freq to be idependent of the dutycycle adjustment. For testing at a certian freq say 50Khz, I would be able to select the best dutycycle for the given transformer design, at 50khz. I was thinking of using a PWM controller IC like the TL494. Instead of using feeback from the PS output I would use a pot with a V.D. Any ideas on how I could achieve my goals?