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 (HPS) 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 (PFC) stage is a buck DC-to-DC converter operating in discontinuous conduction mode (DCM) to meet with the IEC-1000-3-2 Class C requirements. The inverter stage is a very low cost non-resonant topology, based on a buck-boost inverter controlled by means of a specific current mode control implementation. Besides, a novel and simple circuit, compatible with the presented inverter is proposed to ignite the lamp. Furthermore, this circuit implementation provides a protection against broken lamp.