Characterization of Acoustic Resonance in a High-Pressure Sodium Lamp

In the last decades, the high-pressure sodium (HPS) lamp has been supplied in high frequency in order to increase the efficacy of the lamp/ballast system. However, at some given frequencies, standing acoustic waves, namely, acoustic resonance (AR), might develop in the burner and might cause lamp luminous fluctuation, extinction, and destruction in the most serious case. As we seek for a control method to detect and avoid the lamp AR, some main characteristics of ARs in a 150-W HPS lamp are presented in this paper. The first one is the characteristic of the lamp AR threshold power, and the second one is the differences between the forward and backward frequency scanning effects during lamp open-loop operation. Third, the lamp AR behavior in closed-loop operation with an LCC half-bridge inverter will be presented, and it leads to a new point of view and a change in the choice of the AR detection method. These characteristics allow us to further understand AR and to better control the lamp.