Design and Implementation of Dimmable Electronic Ballast for Fluorescent Lamps Based on Power-Dependent Lamp Model

A simple and easy-to-use electric-circuit model for fluorescent lamps is deduced from experimental tests. The lamp arc is modeled as a power-dependent resistance. By incorporating the lamp model with electronic ballast, design equations for dimmable electronic ballasts using half-bridge resonant inverter are derived, and then the dimming operation characteristics can be predicted analytically. Detailed analysis and design of a dimmable electronic-ballast fluorescent-lamp circuit with frequency control are presented. Accordingly, design guidelines for determining circuit parameters are provided. An electronic ballast with half-bridge series-resonant parallel-loaded inverter is used as an example for illustrating the design procedure. A prototype circuit for a T8-36W fluorescent lamp is built and tested to verify the validity of the proposed model.