High-efficiency low-stress electronic dimming ballast for multiple fluorescent lamps

An electronic dimming ballast with a lead-lag tank operation (LLTO) having the properties of high efficiency and low stress is introduced in this paper. The ballast is configured with a voltage-fed half-bridge series-resonant parallel-loaded inverter (SRPLI) acting as a lamp driver. It is loaded with resonant tanks which are designed and operated to be capacitive and inductive to theoretically achieve both zero-voltage switching (ZVS) and zero current switching (ZCS) and to eliminate the reactive current circulating through the switches, resulting in low switching and conduction losses. Moreover, the merit of a successive lamp ignition can be attained with the proposed operation scheme so that current stress imposed on the switches can be reduced. With the plasma model of fluorescent lamps, the analysis, operating principle, and dimming control strategy of the electronic ballast are described in detail. On the other hand, the limitations of the proposed scheme are pointed out. Computer simulation results and experimental measurements are used to verify the theoretical prediction and analytical discussion.