Patent ID: 8643292

Claim:
A digital dimming device for controlling a plurality of light emitting device channels, comprising: a driving signal generation circuit generating a driving signal; a plurality of driver circuits which control currents in the plurality of light emitting device channels according to the driving signal, respectively; and a phase shift circuit receiving a PWM (pulse width modulation) input signal having a duty ratio, and shifting the phase of the PWM input signal to generate multiple PWM output signals with about the same duty ratio as the PWM input signal, but with respectively shifted phases, wherein the phase shift circuit comprises: a pulse width recording circuit recording a pulse width of the PWM input signal; a cycle period recording circuit recording a cycle period of the PWM input signal; a divider circuit dividing the cycle period by the number of the light emitting device channels to obtain a quotient; and a dimming control signal generator generating the multiple PWM output signals according to the recorded cycle period and the quotient, wherein each of the cycle periods of the multiple PWM output signals starts at a different timing which differs from one another by the quotient, wherein the multiple PWM output signals respectively enable or disable corresponding driver circuits, and the duty ratio of each PWM output signal determines an average current of a corresponding one of light emitting device channels.