Patent ID: 7759881

Claim:
A light emitting diode (LED) lighting system comprising: a controller to control current in an LED, wherein the controller includes components to respond to a dimming level input to control an active value of the LED current, wherein: for a first set of dimming levels, the active value varies between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, the LED current is duty cycle modulated; a dimming level strategy module coupled to the controller and having an input to receive a dimmer signal indicating a dimming level, wherein the dimming level strategy module is configured to generate a target active value of the LED current and generate a duty cycle control signal having a duty cycle control value indicating a duty cycle of the LED current, wherein (i) for the first set of dimming levels, the duty cycle control value indicates an LED current duty cycle of approximately 1.0 and (ii) for the second set of dimming levels, the duty cycle control value causes a duty cycle of the LED current to vary in response to varying dimming levels indicated by the dimmer signal; and a duty cycle modulator coupled to the dimming level strategy module to convert the duty cycle control value into a duty cycle modulated enable signal, wherein a duty cycle of the enable signal is approximately 1.0 for the first set of dimming levels and the duty cycle of the enable signal causes a duty cycle of the LED current to vary in response to dimming levels in the second set of dimming levels; wherein the controller includes components to control the active value of the LED current so that an average active value of the LED current is approximately equal to the target active value.