Patent ID: 8853969
Filing Date: 2014-10-07
Classification: H05B

Abstract:
1. A light-emitting element drive device for driving a plurality of light-emitting strings, each light-emitting string comprising at least a light-emitting element, each light-emitting string having a first terminal and a second terminal, the light-emitting element drive device comprising: a power supply circuit, providing a driving voltage to the first terminal of each light-emitting string; a plurality of current sources, corresponding to the plurality of light-emitting strings respectively, each current source coupled to the second terminal of the corresponding light-emitting string; a plurality of error amplifiers, corresponding to the plurality of light-emitting strings respectively, the inverted input terminal of the error amplifier coupled to the second terminal of the corresponding light-emitting string, the non-inverted input terminal of the error amplifier receiving a first reference voltage, each error amplifier amplifying and outputting the voltage difference between the voltage of the second terminal and the first reference voltage; a plurality of first diodes, corresponding to the plurality of error amplifiers respectively, the anode of each first diode coupled to the output terminal of the corresponding error amplifier, the cathodes of the first diodes coupled to each other, wherein the first diode corresponding to the error amplifier with larger output voltage is conducting (ON) and the rest of the first diodes are cut-off (OFF), the voltage at the cathodes of the first diodes is a detecting voltage; and a control circuit, controlling the driving voltage of the power supply circuit, and receiving the detecting voltage, wherein the control circuit compares the detecting voltage and a reference value to adjust the driving voltage of the power supply circuit, so as to make the current sources provide equal current to the light-emitting strings.