Patent attributes
An LED controller for a multiple LED channel system using PWM method for LED dimming function incorporates a digital dimming control circuit to generate the PWM signals for driving the LED channels to spread out or cancel out the power supply transients generated by the LED transient current during PWM modulation for dimming operation. The digital dimming control circuit implements an audible noise reduction method whereby the active period of the PWM signals for some of the LED channels are shifted within the switching cycle to align at least some of the rising signal edges with some of the falling signal edges so as to cancel out the voltage transients on the LED power rails generated at the signal transitions. Furthermore, the rising and falling signal edges that are not lined up are spread out through the PWM switching cycle so that the power supply transients are spread out.
