Thanks for the reply. I also found an article by searching google for Circuit Voltage Booster. I knew about dc-dc converters, but I haven't had any luck working with them. The step-ups I've seen generated a lot of HF noise, couldn't supply a lot of current, got less efficient and greater ripple as more current was drawn, and required inductors & booster ICs. I ruled them out for this project because of the problems I had.