Program start fluorescent ballast with clamped-Q resonant filament heating circuit

In this paper, a program-start fluorescent ballast is proposed. The proposed program start ballast has a resonant filament heating circuit with clamped Q. The proposed resonant filament heating circuit gives the ballast strong filament preheat capability, desensitizes the preheat voltage variation within a reasonable range of preheat frequency and cuts the filament heating back in full bright. Moreover, the proposed circuit makes the filament heating voltage insensitive to component value changes. The proposed low cost program-start fluorescent ballast improves the system efficacy and effectively solves the large pin current problem. Mathematical analysis of the filament drive tank with clamped Q is described in detail. Simulation and experimental results for two and one T5 28W lamp loads are presented to validate the analysis. Simulation and experimental results are in excellent agreement.