A comparison of resonant inverter topologies for HPS lamp ballasts

Abstract

The utility of resonant inverter topologies in electronic ballasts for high-pressure sodium (HPS) lamps is examined. The three basic types of resonant inverters, series-loaded, parallel-loaded, and series-parallel-loaded, are compared for their applicability in electronic ballasts. A parallel-loaded resonant (PLR) inverter operating at a constant switching frequency is selected because of the high voltage gains possible. As a result, it is not necessary to use a transformer to provide enough voltage to start the HPS lamp from a low-voltage DC source such as that obtained from rectification of 120 V AC source. A PLR inverter was designed based on this analysis. A computer simulation of this design verified inverter operation when driving an HPS lamp. A laboratory prototype was then constructed and found to operate satisfactorily.<>