Patent ID: 7961158

Claim:
A constant-current driving circuit, for driving a first LED string, comprising: a first current source having a terminal coupled to a terminal of the first LED string, wherein a coupling node of the first current source and the first LED string has a first voltage; a reference voltage generating circuit, for generating a reference voltage and comparing the first voltage with a first predetermined voltage to generate a first comparing signal and thereby dynamically adjust the reference voltage; and an output signal generating circuit, for outputting an output signal to another terminal of the first LED string, wherein the output signal generating circuit receives an input signal and decides whether or not to output the input signal according to a comparison result between the reference voltage and a second voltage, wherein the second voltage is a dividing voltage of a first impedance and a second impedance connected in series; an end of the first impedance receives the output signal; an end of the second impedance is coupled to another end of the first impedance for generating the second voltage and another end of the second impedance is coupled to another end of the first current source.