In some examples, a circuit comprises a first switch adapted to be coupled to a direct current (DC) power source, a second switch coupled to the first switch and adapted to be coupled to the DC power source, and a resistor coupled to the first and second switches. The circuit comprises a transformer having a primary side and a secondary side, the primary side coupled to the first and second switches, the secondary side adapted to be coupled to a load. The circuit comprises a third switch coupled between the resistor and the primary side of the transformer, and a capacitor coupled to the second switch.