resonant inductor l r and a resonant capacitor c r whose values determine the frequency of current in the resonant load circuit a capacitor 116 serves to block d c current from flowing through winding 112 a bidirectional current is generated in resonant load circuit 114 through an alternating sequence of connecting node 118 to bus conductor 110 to receive bus voltage v b and then to ground this is carried out through the alternate switching action of a pair of serially coupled switches s 1 and s 2 which are connected between bus conductor 110 and ground and whose common node comprises node 118 switches s 1 and s 2 which may comprise n channel mosfets for instance are controlled by respective gate or control terminal circuits 120 and 122 gate circuits 120 and 122 respectively employ transformer windings t 1 and t 2 that are poled oppositely to each other as shown by the respective dots in the proximity of the windings each circuit 120 and 122 has a respective back to back coupled pair of zener diodes shunted across its associated transformer winding t 1 or t 2 the upper diode of each pair is typically rated at 7 5 volts and the lower diode of each pair is typically rated at 10 volts the zener diode pairs 121 and 123 limit the voltage excursions.