Pulse Width Modulation (SineWave)
SineWave dimmers offer complete silence and energy efficiency and represent the state of the art in dimming systems.
Pulse Width Modulation (PWM) techniques are employed in SineWave dimmers for controlling the amplitude of the incoming power supply. In basic terms, the input supply is sliced at high frequency (40-50 kHz) and the transistors are switched, varying the ratio of on/off time within the sample period. The 'on' period of the 'mark/space ratio' is proportional to the power needed to match the amplitude of a sine wave at that point in the mains cycle.
The output current waveform is smoothed using a passive network to produce an output waveform that accurately represents the waveform profile of the incoming supply. The PWM process adds less than 1% distortion to the mains supply, resulting in a completely silent dimmer with a remarkable facility for dimming almost any load.