Analysis and Design of Self-Oscillating Full-Bridge Electronic Ballast for Metal Halide Lamp at 2.65-MHz Operating Frequency

This paper presents the analysis and design of the self-oscillating full-bridge electronic ballast for the metal halide lamp at 2.65-MHz operating frequency. In order to avoid the acoustic-resonance problem of the metal halide lamp and meet the electromagnetic interference limitation by International Electrotechnical Commission (IEC) regulation, the self-oscillating full-bridge electronic ballast is operated at 2.65-MHz radio frequency (RF). However, the effect caused by the gate-to-source capacitor C_gs of the mosfets on the self-oscillating gate-drive network becomes significant to influence the design of the operating frequency at RF. Therefore, the gate-to-source capacitor C_gs of the mosfets is considered to derive the design equation of the magnetizing inductor for the current transformer in the self-oscillating gate-drive network. Finally, based on the prototype circuit of a 35-W self-oscillating full-bridge electronic ballast with constant-lamp-current control and no-lamp-protection scheme at 2.65-MHz operating frequency, the SIMPLIS simulation and experimental results are used to validate the effect from gate-to-source capacitor C_gs, the proposed design equation, and the design criteria.