An isolated active-clamp flyback power supply with a new resonant operation mode is designed and experimentally tested. A full soft-switching design based on dead-time optimization new approach is implemented. Each topology phase is detailed. An experimental board is presented for high ambient temperature (200 °C) operation. The power supply is dedicated to provide the driver power of wide bandgap power components in a phase-leg configuration. The constraint for galvanic isolation is high and guides the design of the transformer. The power-supply capabilities are 15 V input voltage, 6 V output voltage, 2 W output power, 75% peak efficiency, 11 cm2 footprint, and nominal operation at 200 °C ambient temperature.