Asymmetrical group-pulse-width-modulated technique for eliminating striation in the dimmable fluorescent lamps

An asymmetrical group-pulse-width-modulated (AGPWM) control strategy is proposed for eliminating the striation in a dimmable fluorescent lamp. The approach is executed by alternately modulating the pulse-width of a group-driving signal with a suitable period to reduce the odd harmonic amplitudes of the lamp current and increase the even ones. The striation in the lamp disappears due to all amplitudes of the distributed harmonics in the lamp current spectrum are close to each other. Therefore, the lighting efficiency increases and the total harmonic distortion is reduced. In this paper, a half-bridge series-resonant inverter (HB-SRI) is used for realizing the ballast operation with the proposed controller. A modeling work and a control strategy for system analysis and performance evaluation are clearly conducted. The examined prototype with simulation and experiment is presented for assessing the theoretical predictions. Experiment shows that no striation occurs during wide-range dimmer of 1%-100%