| 摘要 |
An LED(Light Emitting Diode) driving circuit and a control method thereof are provided to reduce the output voltage of a power supply circuit correspondingly to the voltage drop caused due to a resistance by setting the driving current of an LED without the resistance. An LED driving circuit(1) driving plural LEDs(LED1~LED4) includes a power supply circuit(2) supplying power to each LED, wherein the output voltage of the power supply circuit is variable; plural drive transistors(M1~M4) driving the corresponding LED; a bias voltage setting circuit(4) generating and outputting reference gate voltage(Vgs0) for setting the drain current of each drive transistor as a predetermined constant current value and the minimum drain voltage(Vds0) required to set the drain current of each drive transistor as the constant current value when the reference gate voltage is input to each gate of drive transistors; and a voltage detecting circuit(3) comparing drain voltage(Vdsx) of the drive transistors with the minimum drain voltage and outputting the drain voltage lower than the minimum drain voltage in sequence. The power supply circuit controls output voltage(Vout) to make the drain voltage output from the voltage detecting circuit higher than the minimum drain voltage output from the bias voltage setting circuit.
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