HPS lamp control by signal injection of approaching frequency to avoid acoustic resonances: Application to an LCC circuit

The supply of high intensity discharge (HID) lamp at high frequency provides important benefits in ballast optimization. However, in certain frequency range, the lamp is disturbed by the acoustic resonance (AR) which can lead to lamp arc fluctuation, extinction and lamp destruction in the worst case. This paper presents a novel approach of lamp control based on the injection of signals of approaching frequencies to avoid acoustic resonances in high pressure sodium (HPS) lamps operating under high frequency condition. The injected signals are confined within a selective band, so the lamp can be operated by a simple LCC half-bridge inverter based on the PWM modulation. The advantages in this strategy remain in the simplicity of the ballast structure and the independent control of injected signal parameters. Furthermore, additional adjacent frequency signals can still be injected without modifying the ballast structure or the PWM scheme in order to improve the AR avoidance. The simulation and experimental results are also presented in this paper.