Reduction of line-current total harmonic distortion (THD) of a Valley Fill electronic ballast

This paper presents a modified Valley-Fill (VF) ballast circuit to combine with a current fed resonant inverter as the power circuit for a high power factor VF electronic ballast. The original VF circuit permit input current conduction from 30° to 150°, and then from 210° to 330°. Due to this discontinuity, high total harmonic distortion (THD) results into the input current waveform. The modified VF circuit allows the conduction angle of the line current to be further extended to 0° ≤ ωt ≤ 168.86° and 180° ≤ ωt ≤ 333o. The proposed VF circuit also reduces the current spike when compared with the conventional VF ballast.