Patent ID: 8354998

Claim:
An information input panel using light emitted diode matrix, comprising: a light emitted diode matrix, comprising a plurality of light emitted diodes, wherein each light emitted diode comprises a first terminal and a second terminal; and a plurality of control circuits, wherein a first control terminal of each control circuit is coupled to the first terminal of the corresponding light emitted diode, and a second control terminal of each control circuit is coupled to the second terminal of the corresponding light emitted diode, wherein, in a detecting period, the control circuit detects the reverse photoelectric current of the corresponding coupled light emitted diode to determine whether the corresponding coupled light emitted diode is lighted up, wherein the first terminal of each light emitted diode is cathode, and the second terminal of each light emitted diode is anode, and in the detecting period, the second control terminal of the control circuits provides a common voltage and the first control terminal of the control circuit provides a power supply voltage for a preset period, and then the control circuit sets the first control terminal to a high impedance state, and each control circuit comprises: a comparator, comprising a first input terminal, a second input terminal and an output terminal, wherein the first input terminal thereof receives a preset voltage, a second input terminal thereof is coupled to the first control terminal of the control circuit, in the detecting period, a voltage of a comparing signal outputted from the output terminal of the comparator is changed from a first saturation voltage to a second saturation voltage when a voltage of the first control terminal of the control circuit is smaller than the preset voltage; a counting circuit, coupled to the output terminal of the comparator, wherein from the beginning of the detecting period, a counting value is accumulated for each preset time, wherein when the voltage of the comparing signal is changed from the first saturation voltage to the second saturation voltage, the accumulating is stopped and the accumulated counting value is outputted; and a judging circuit, coupled to the counting circuit for receiving the counting value, wherein the light emitted diode is lighted up when the counting value is smaller than a preset value.