Patent ID: 8004201

Claim:
A LED circuit comprising: an inductor connected to a voltage supply and a first node; a group of LEDs connected to the first node and a ground potential; a power MOS connected to the first node and the ground potential; a switching circuit comprising: an error amplifier generating an error output according to a dimming voltage having an active period and an inactive period; a pulse width modulator (PWM) to generate a switching signal according to the error output to control the gate of the power MOS to charge or discharge the group of LEDs; a RC circuit comprising: at least one first capacitor each comprising a switch; at least one second capacitors, wherein the first and the second capacitors are connected in parallel; and a resistive means connected in series between the first and the second capacitors and the error output; and a control means to generate a control signal according to the dimming signal, wherein the control signal turns on the switches to activate the first capacitor when the dimming signal is in the active period to make the RC circuit perform charging and turns off the switches to deactivate the first capacitor when the dimming signal is in the inactive period to make the RC circuit perform discharging.