High efficiency, low stress electronic dimming ballasts for multiple fluorescent lamps

A high efficiency and low stress electronic dimming ballast with the proposed circuit operation scheme, namely lead-lag tank operation (LLTO) scheme, is introduced in this paper. The ballast is configured with a voltage-fed half-bridge series-resonant parallel-loaded inverter acting as a lamp driving stage. The lamp driving stage is loaded with resonant tanks which are designed and operated to be capacitive and inductive to achieve both zero-voltage switching as well as zero-current switching, and 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 as current stress imposed on the switches can be reduced. With the plasma model of fluorescent lamps, 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.