Patent ID: 7911441

Claim:
A current-controlling apparatus, suitable for controlling the current of an LEDS (LED string), wherein an end of the LEDS is electrically connected to a first voltage level; the current-controlling apparatus comprising: a current-adjusting unit, electrically connected between another end of the LEDS and a second voltage level, used for detecting the current of the LEDS, accordingly producing a feedback signal and controlling the impedance between the LEDS and the second voltage level according to a conductance-controlling signal and a impedance-controlling signal for further controlling the current of the LEDS, wherein the current-adjusting unit comprises: a MOS transistor, wherein a source/drain of the MOS transistor is electrically connected to another end of the LEDS; a variable impedance device, electrically connected between the control unit and the gate of the MOS transistor, used for delivering the conductance-controlling signal to the gate of the MOS transistor and dynamically adjusting the resistance of the variable impedance device according to the impedance-controlling signal, so that the MOS transistor is able to shift the on/off status thereof according to the conductance-controlling signal and the resistance of the variable impedance device, and the impedance of the MOS transistor in on status is further adjusted; and a feedback unit, electrically connected between another source/drain of the MOS transistor and the second voltage level, used for detecting the current of the LEDS and accordingly producing the feedback signal; and a control unit, electrically connected to the current-adjusting unit, used for receiving a reference signal and the feedback signal and comparing the feedback signal with the reference signal to produce a comparison result, performing a current compensation on the comparison result and converting the compensated comparison result into the conductance-controlling signal and the impedance-controlling signal.