Small signal dynamic characterization of HID lamps

In the literature, several low-signal dynamic models for fluorescent lamps have been presented. These models can be used to analyze the lamp-ballast interaction in high frequency electronic ballasts. However, the small signal characteristics of HID lamps differ from those of fluorescent lamps, so the models described in previous literature cannot be applied to the analysis of HID lamp ballasts. In the present paper the small-signal characteristics of a mercury vapor lamp and a high pressure sodium lamp are obtained and compared to the typical characteristics of fluorescent lamps. The main differences between HID and fluorescent lamp small-signal characteristics are remarked upon. The key points for the stability analysis of the lamp-ballast system are also addressed in this paper. Using the multi-frequency averaging technique the interaction between a high pressure sodium lamp and a resonant inverter is analyzed and verified using a laboratory prototype.