A comparative study on dimming control methods for electronic ballasts

This paper presents a comparative study on the performance characteristics between the variable switching frequency and variable DC link voltage control schemes for the dimming operation of electronic ballasts using a half-bridge series-resonant parallel-loaded inverter. Attributes under investigations include (1) average input current of the inverter; (2) dimming characteristics; (3) variations of the filament power and starting voltage throughout the dimming range; (4) dead time boundaries for ensuring zero-voltage-switching in the inverter. An approximated fundamental-frequency model that includes the characteristics of the nonlinear lamp resistance and filament resistance is used. Theoretical predictions are favorably verified with the experimental measurements in two 36 W Ballast-lamp systems.