A start-up method for a self-powered gate drive circuit driving a power transistor gate. The method comprises charging, with a single-supply voltage, a first supply capacitor of a first gate drive circuit; switching on a first power transistor by applying a current supplied by a discharge of the first supply capacitor of the first gate drive circuit to the gate of the first power transistor; charging a second supply capacitor of the first gate drive circuit using an output signal from the first power transistor; and re-charging the first supply capacitor by applying a current supplied by a discharge of the second supply capacitor to the first capacitor.