Control of Solid-State Lamps Using a Multiphase Pulse width Modulation Technique and AC side Power Factor Correction

This paper describes a multiphase pulse width modulation (MPWM) technique used for controlling the luminance of a solid-state lamp (SSL). In conventional pulse width modulation (PWM) and pulse code modulation techniques, the average HBLED string current is controlled by simultaneously varying the “ON” time duration of each current regulator circuit, resulting in large current transients and pulsating light output. The proposed MPWM technique operates by uniformly time-shifting the individual ON/OFF control signal pulses, thus avoiding large current transients. When compared to conventional PWM dimming, MPWM dimming reduces the risk of visible flicker and lowers the magnitude of audible noise. The reduced magnitude of output current transients results in lower electromagnetic interference and enables optimization of the size of passive components. In this paper, the operation of the MPWM technique is explained in detail. Finally a flyback converter topology with input side power factor correction topology is proposed and simulation results are presented.