Patent ID: 8120274
Filing Date: 2012-02-21
Classification: H05B

Abstract:
1. A controlling circuit, comprising: a plurality of first switches, having a first terminal and a second terminal for each of the first switches, wherein the first terminals are respectively coupled to one of a plurality of light emitting diode strings, the first switches are conducted according to a plurality of first switching signals respectively, and the first switching signals are asserted alternately; a comparator, having a first input terminal and a second input terminal, wherein the first input terminal is coupled to the second terminals of the first switches and the second input terminal of the comparator receives a first reference voltage, for comparing the voltage of the first input terminal with the voltage of the second input terminal so as to output a comparison result; and a reference voltage generator, coupled to the comparator and outputting a second reference voltage according to the comparison result; an error amplifier, coupled to the reference voltage generator and receiving the second reference voltage and a dividing voltage so as to output an adjusting signal; a power supply, coupled to the error amplifier and the light emitting diode channels, adjusting a supply voltage according to the adjusting signal and outputting the supply voltage to the light emitting diode channels; a voltage-dividing circuit, coupled to the power supply and the error amplifier and generating the dividing voltage according to the supply voltage; and a voltage-regulating capacitor, coupled to the power supply.