Patent ID: 7982412

Claim:
A LED circuit comprises: 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 capacitor connected to the first node and a ground potential; a power MOS connected to the first node and a ground potential, wherein the gate of the power MOS receives a switching signal such that the capacitor is charged when the switching signal turns on the power MOS turn on the LEDs and the capacitor is discharged when the switching signal turns off the power MOS to turn off the LEDs; and a switching circuit to generate the switching signal comprising: a control module to receive a dimming signal having an active period and an inactive period to generate a control signal according to the dimming signal; an error amplifier to generate an error signal according to the dimming signal from the control module; and a pulse width modulator to compare the error signal and a reference signal to generate a compare result, the control signal controls the pulse width modulator to turn on when the dimming signal is in the active period and to turn off when the dimming signal is in the inactive period, wherein the switching signal turns on the power MOS during the active period according to the compare result and turns off the power MOS during the inactive period.