Electronic Ballast For Metal Halide Lamps Research Articles

A Novel Single-Stage High-Power-Factor Electronic Ballast for Metal-Halide Lamps Free of Acoustic Resonance

This paper proposes a novel single-stage high-power-factor electronic ballast for metal-halide lamps. By integrating two buck-boost converters, a full-bridge inverter and a bidirectional buck converter, a single-stage electronic ballast with symmetrical circuit topology is derived. The circuit component count can be effectively reduced and circuit energy-conversion efficiency is improved. With a tactful control scheme, the proposed electronic ballast can output a low-frequency square-wave voltage to drive metal-halide lamps. The problematic phenomena of acoustic resonance can be eliminated. Both the buck-boost converters serve as power-factor correction (PFC) circuits, which are operated at discontinuous conduction mode (DCM) to obtain a unity power factor at the input line. The operation modes, design equations, and design steps for the circuit parameters are proposed. A prototype circuit designed for a 70-W metal-halide lamp was built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results.

Design and implementation of frequency-modulated electronic ballast for metal-halide lamps

A two-stage, frequency-modulated (FM), high-frequency-driven electronic ballast for metal-halide (MH) lamps is proposed. The presented ballast consists of a power-factor-correction (PFC) converter as the first stage, a half-bridge series-resonant parallel-loaded (HB-SRPL) inverter as the second stage, and a frequency-modulation controller. The advantageous features of the high-frequency-operated ballast are its compact size and reduced weight. With constant-frequency control, the switching frequency of the ballast must be carefully designed within a frequency window that is free from acoustic resonance, and the envelope of the lamp current is large owing to the DC-bus voltage ripple that occurs on the PFC output. However, if the switching frequency of the inverter is operated outside of the stable operation window or if the energy of some eigenfrequency is sufficiently higher, then acoustic resonances will exist. An FM-controlled electronic ballast for MH lamps is proposed. The switching frequency of the HB-SRPL inverter, whose centre frequency is intentionally designed at a frequency at which acoustic resonances occur, is periodically modulated by the voltage ripples of the PFC output. The presented ballast offers a lower envelope of lamp current in order to expand the power spectrum of the lamp and to decrease the energy of the eigenfrequency that supplies the lamp. Owing to its FM operation that allows for an adequately modulated index, no acoustic resonance occurs. The ballast offers cost-effectiveness, a simple control circuit without an external modulation signal, and a low crest factor (<1.45). Design guidelines and experimental results are presented for a 70 W MH lamp ballast that utilises the FM control method with universal-line input voltage.

HID 램프를 위한 상태 적응형 점화기 설계 방법

현재까지 HID 램프는 광원이 가진 많은 장점에도 불구하고, 고온 순시 재 점등과 음향 공명 현상으로 인해서 실내 광원으로서의 사용이 제한되어왔다. 하지만 많은 연구를 통해서 램프가 뜨거운 상태에서도 순시 재 점등이 가능한 방법이 제시되어 왔고, 실제로 사용되어지고 있다. 하지만 이러한 방법은 램프 상태와 무관하게 20[㎸] 정도의 전압을 램프에 인가하는 방법으로, 일반적으로 램프 수명이 감소하는 특징을 가지고 있다. 그러므로 순시 재 점등과 수명 문제는 중요한 연구 대상으로 인식되어왔다. 본 논문에서는 램프가 차가운 상태에 필요한 점화 전압과 램프가 뜨거운 상태에서 점등에 필요한 점화 전압을 발생시키는 독립적인 2개의 점화기를 사용함으로써, 램프 상태에 따라 각기 다른 점화 전압을 램프에 인가하는 방법을 제안하고자 한다.