Research On Electronic Ballast For High Power Metal Halide Lamp Based On DSP Control

As the third-generation green lighting illuminating source, the metal halide lamp has been widely applied in Green Lights Program because of its advantages such as high efficiency, energy saving, better color temperature and long life,etc. However, since the negative resistance characteristics of the metal halide lamp, the progress of the metal halide lamp must accompanied with the operation of suitable ballast. The inductance ballasts and the electronic ballasts are the commonly used ballast, but the inductance ballast has not been able to satisfy the requirement of green lighting due to its disadvantages of large volume, low efficiency and low power factor, etc. Thus, the electronic ballast with high efficiency, high reliability and high power factor has been studied widely and become a hot spot.Traditional electronic ballast for high-power metal halide lamp is controlled by analog chips. With the development of digital signal processing technique, the application of MCU, DSP, and FPGA makes digitalization and intelligent control of electronic ballast possible. The research of digital control has a significant meaning for the development of electronic ballast.The electronic ballasts of digital control for6kw power metal halide lamp which was used in the field of film and television lighting was taken as a subject investigated in this paper, the TI’s TMS320LF2407A was used as the control chip. Firstly, this paper introduces the development of analog electronic ballasts and digital electronic ballasts and it states the advantages and technical characteristics of digital controlled electronic ballasts. Secondly, it introduces the working principle while explains the merits and drawbacks of the metal halide lamp. Thirdly, this paper analyzes the working characteristics of the metal halide lamp from the beginning of working to steady conditions. Meanwhile, according to the characters of the negative resistance, this paper supplies some suggestions about subdivision control. Finally, it discusses the acoustic resonance phenomenon of the metal halide lamp at high frequency and proposes some related solutions.A review of the commonly used topology for electronic ballast is proposed in this paper. In accordance with the practical application, a three-stage configuration for the power-stage circuit is applied here. The front-end is the Boost APFC. The principle of digital control and the vital performance of feed-forward are discussed. The second-stage is a constant power control circuit, which is earried out by the Buck configuration. The control scheme of the second stage is the average current control based on the continuous current mode (CCM). This control project consists of a double loop. The digital realization of the peak current control is proposed. The design of the digital compensation net work is also discussed. A PID compensator has been designed on the basis of small-signal-modulation approach. The simulation is carried out by Matlab. The visibility and effectiveness of the control scheme has been verified. The design of the digital compensator according to the root locus approach is provided. In the last chapter, the software program is proposed in addition to the flow diagram. The verification is carried out by a6kw prototype. The performances are beyond the requirements according to the analysis.