Patent ID: 7560981
Filing Date: 2009-07-14
Classification: H05B

Abstract:
1. A controlling apparatus for controlling a plurality of LED strings, wherein each of the plurality of LED strings has a first terminal being electrically connected to an operating voltage, the controlling apparatus comprising: a plurality of transistors, each having a control terminal, a first terminal, and a second terminal, the first terminal of each transistor being electrically connected to a second terminal of a corresponding string of the plurality of LED strings, and the second terminals of the plurality of transistors being respectively grounded through a plurality of impedance elements; a transistor controller, electrically connected to the control terminals of the plurality of transistors, for controlling a current passing through the first terminal of each transistor by adjusting an input signal of the control terminal of the transistor according to a voltage at the second terminal of the transistor; and an error calculating circuit, electrically connected to the transistor controller and the second terminals of the plurality of transistors, for calculating a difference between the voltage at the second terminal of each transistor and a corresponding reference voltage; wherein the transistor controller adjusts the input signal of the control terminal of the transistor according to a calculation result generated by the error calculating circuit.