Complete low-cost two-stage electronic ballast for 70-W high-pressure sodium vapor lamp based on current-mode-controlled buck-boost inverter

In this paper, a low-cost electronic ballast for high-pressure sodium vapor lamps is presented. The proposed ballast is a two-stage circuit that requires only one switch and one inductor for each stage. The power-factor-correction stage is a buck dc-to-dc converter operating in discontinuous conduction mode to meet the IEC-61000-3-2 Class C requirements. The inverter stage is a low-cost nonresonant topology, based on a buck-boost inverter controlled by means of a specific current-mode control implementation. In addition, a novel and simple circuit, compatible with the presented inverter, is proposed to ignite the lamp. Furthermore, this circuit implementation provides protection against broken lamps.