Patent ID: 8796947

Claim:
A light source driving device, comprising: a light source unit, comprising a first end and a second end; a driving unit, configured to receive an input signal, and convert the input signal to a driving signal for output according to an enable signal and a feed-back signal; a voltage converting unit, coupled to the driving unit and the first end of the light source unit, the voltage converting unit configured to receive the driving signal, convert the driving signal to a driving voltage, and output the driving voltage to the first end of the light source unit; a detecting unit, coupled to the second end of the light source unit, the detecting unit configured to detect an output current of the light source unit for generating a detecting voltage; and a feed-back control unit, coupled to the detecting unit and the driving unit, the feed-back control unit configured to receive the detecting voltage and a pulse width modulation signal for generating the feed-back signal according to the detecting voltage and the pulse width modulation signal, wherein the feed-back control unit comprises: a first resistor, comprising a first end for receiving the pulse width modulation signal; a second resistor, comprising a first end coupled to the detecting unit, and a second end coupled to a second end of the first resistor; a first operational amplifier, comprising a first input end coupled to the second end of the second resistor, and an output end for outputting the feed-back signal; a third resistor, comprising a first end coupled to a second input end of the first operational amplifier, and a second end coupled to a ground terminal; and a fourth resistor, comprising a first end coupled to the first end of the third resistor, and a second end coupled to the output end of the first operational amplifier.