Research On Dimming Electronic Ballast For Electrodeless Lamps

Electrodeless lamp, due to the excellent features of high efficiency, no flash and long life, is a good promising discharge light source. Since Electrodeless lamps has negative resistance characteristic, it needs to cooperate with ballast for working. Thus, it is significant to analysis and design the electronic ballast.Firstly, the paper analyzes the emitting characteristics of electrodeless lamp, compares with other electric discharge lamp light source, summarizes the trends in electronic ballast. Based on the research of the mathematical modeling and topology of the eletrodeless lamp, makes the deduction of the main parameters’relationship between the amount under the resonant operation status and the analysis of resonant converter working principle and soft-switching working conditions.Natural resonance frequency for induction lamp systems shift due to the resonance parameter changes. The paper studies a new type of digital phase locking method. By locking the half-bridge inverter’s the midpoint voltage and the resonant capacitor voltage phase, the system can accurately track the natural resonant frequency of the resonant circuit. It solves the problem that the lamp does not work due to the natural resonance frequency shift.As phase angle between the half-bridge’s midpoint voltage and the resonant capacitor voltage control variables is the phase-locked control variable, the paper establishes the mathematical model of the DPLL, introduces the the design process of hardware and software in detail. The experiment result verifies it.Analyzing the problem of commonly used electrodeless lamp light modulation methods, the paper presents a combination of the pulse frequency modulation and the improved pulse density modulation composite dimming scheme. Through simulation analysis and verification of the new approach, it has some advantages, such as high precision and wide range of dimmer and so on.The experimental prototype of electrodeless lamp is designed using single chip dsPIC33FJ16GS502 as the main controller. Experimental results demonstrate that the proposed scheme is feasible.