The simplest electronic ballast for HID lamps

The resonant forward-flyback (RFF) inverter is presented, analyzed theoretically and tested experimentally. It is shown that the inverter can be designed to operate under zero voltage switching (ZVS) conditions and that it acts as a current source, features that are highly compatible with HID lamp ballasting. The design guidelines and the detailed analytical expressions developed in this study were verified by computer simulation and hardware implementation. The experimental results of the study demonstrate that the arc of small 35 W and 70 W metal halide discharge lamps can be stabilized by the proposed RFF ballast when operated in the 300 kHz to 400 kHz switching frequency range and applying about 20% FM modulation. Considering the fact that the proposed ballast includes only one switching device, one magnetic component and one resonant capacitor, the RFF inverter is most likely the simplest ballast topology possible.