Abstract: A DC to DC step-up converter is provided which employs high efficiency switching components such as MOSFET switching components in a main converter and provides a low power auxiliary converter to obtain the start up voltage required for operating the low resistance component of the main converter. A control circuit is provided which utilizes either the start up voltage from the auxiliary converter or a feedback voltage from the main converter output to provide control input to the low resistance switching devices which inputs are operative to maintain the output voltage at a desired level.