Patent ID: 7245090

Claim:
A LED driver comprising: an energy-transferred element, connected in series with a LED; a switch, coupled in series to the LED and the energy-transferred element for controlling a LED current; a control circuit, generating a control signal in response to a voltage signal of the LED and the LED current; a diode, coupled to the LED and the energy-transferred element for discharging the energy of the energy-transferred element through the LED; a first resistor, connected in series with the LED to sense the LED current and generate a LED current signal coupled to the control circuit; and a second resistor, connected to the control circuit to determine a slope of the adjustment, in which the slope represents the change of a first threshold versus the change of the LED current of the LED; wherein the control signal is used to control the switch and the LED current, wherein the switch is turned off once the LED current is higher than the first threshold, and the first threshold is varied in response to the voltage signal of the LED, and the switch is turned on after a period of a programmable delay time once the LED current is lower than a second threshold.