Comparison between integrated and non-integrated SEPIC half-bridge electronic ballasts for electrodeless fluorescent lamp applications

A comparison between integrated and non-integrated topologies to feed a 100 W electrodeless fluorescent lamp (EFL) at 250 kHz is presented in this paper. The analysis considers efficiency, power factor (PF) and line current total harmonic distortion (THD) of the electronic ballast. A dimming feature is provided to investigate the system behavior when the lamp power decreases. The proposed topologies are composed of a Single-Ended Primary Inductance Converter (SEPIC), used as power factor correction (PFC) stage and a resonant half-bridge inverter, used as lamp power control (PC) stage. The integration is made between the PFC and PC stages. This process is usually employed in order to reduce the number of active switches, as well as to simplify the required driving and control circuitry. For the non-integrated topology two different frequencies were used in the PFC stage, 40 kHz and 250 kHz. The implemented topologies attained very high PF, greater than 0.98 for all ballasts, and low line current total harmonic distortion (maximum 15.56% at rated power), without using electromagnetic interference (EMI) filter. The measured efficiency varied from 85% to 92% at nominal lamp power.