Patent ID: 7579786

Claim:
A method for driving LED's comprising the steps of: receiving a desired intensity value, wherein said desired intensity value represents the desired intensity for said LED's; generating a first switching control signal, wherein said first switching control signal is a pulse width modulated signal whose duty cycle is based on said desired intensity value; switching said LED's on and off based on said first switching control signal, wherein said switching takes place when said desired intensity value is less than a first desired intensity value threshold; generating a desired constant current value based on said desired intensity value, wherein said desired constant current value represents the value of the desired constant current to drive said LED's; determining an actual constant current value, wherein said actual constant current value represents the value of the actual constant current driving said LED's; comparing said actual constant current value with said desired constant current value; and adjusting the output of the primary drive of said LED's so that said actual constant current value is equal to said desired constant current value.