Patent ID: 8248000
Filing Date: 2012-08-21
Classification: H05B

Abstract:
1. A light emitting device driver circuit for driving a light emitting device array which includes a plurality of light emitting device strings, the light emitting device driver circuit comprising: a power supply stage for supplying an output voltage to the light emitting device strings, wherein one end of each of the light emitting device strings is coupled to the output voltage in common; a corresponding plurality of transistors coupled to the other ends of the light emitting device strings respectively, wherein each transistor is a field effect transistor or an NPN bipolar junction transistor having a current inflow end, a current outflow end, and a control end; a corresponding plurality of resistors coupled to the current outflow ends of the transistors respectively; a power supply stage controller, coupled to the power supply stage for controlling the power supply stage; a corresponding plurality of operational amplifiers for comparing signals obtained from the current outflow ends with a first reference signal respectively, and generating operational amplifier output signals to control the control ends of the corresponding transistors respectively; a highest voltage selection circuit, receiving the operational amplifier output signals, and outputting a highest one among the operational amplifier output signals; an error amplifier coupled to the highest voltage selection circuit, for comparing the highest signal with a second reference signal and generating an error signal which is inputted to the power supply stage controller to control the power supply stage; and a plurality of over voltage exclusion circuits, coupled to output terminals of the corresponding operational amplifiers respectively, for excluding an operational amplifier output signal which is out of a preset range, and outputting an operational amplifier output signal which is not excluded to the highest voltage selection circuit.