A Single-Stage Electronic Ballast for High-Intensity-Discharge Lamps with Input Current Shaping

摘要

High-intensity-discharge (HID) lamps have many advantages, such as high luminous efficacy, good color rendering, and long lifetime. And they are suitable for outdoor and indoor lighting applications. Commercial HID lamp ballasts consist of a boost converter for power factor correction, a buck converter for adjusting lamp power/current, and a full-bridge inverter for supplying the lamp with low-frequency square-wave sources. However, large numbers of power switches and components are required, and limited circuit efficiency is obtained in the traditional HID lamp ballast due to three-stage power conversions. In response to these concerns, this paper presents a single-stage electronic ballast for HID lamps that offers the function of input utility-line current shaping. The presented ballast integrates a modified bridgeless power-factor-correction (PFC) converter with a high-frequency combined with low-frequency square-wave-driven full-bridge-type inverter into a single-stage power conversion, thus achieving PFC and supplying the HID lamp with low-frequency square-wave sources. The features of the proposed ballast are high power factor, low total-harmonic-distortion (THD) of input utility-line current, cost-effectiveness and freedom from acoustic resonance. This paper presents the operational principles, design equations and experimental results of the proposed ballast for one 70 W metal-halide-type HID lamp operating with input utility-line voltage of 110 V-rms and utility-line frequency of 60 Hz.