Optical detection apparatus, liquid crystal display device using the same and driving method thereof

1. An optical detection apparatus for controlling the backlight of a liquid crystal display device comprising:

an optical/electric converter transducing light incident on the optical/electric converter into a current flowing to a ground potential;

a current mirror supplying a mirror output voltage to a current mirror output node in response to an enable signal, the mirror output voltage having a magnitude proportional to the intensity of light incident on the optical/electric converter; and

a switch connecting a driving node of the current mirror to the ground potential through the optical/electric converter in response to the enable signal,

wherein the optical/electric converter includes a gate to receive a bias voltage, a drain connected to the switch, and an N-MOS transistor having a source connected to the ground potential.

2. The optical detection apparatus according to claim 1 , wherein the current mirror varies the mirror output voltage in proportion to a light intensity incident on the optical/electric converter.

3. The optical detection apparatus according to claim 1 , wherein the switch includes an N-MOS transistor having a gate to receive the enable signal, a drain connected to the driving node of the current mirror and a source connected to the optical/electric converter.

4. The optical detection apparatus according to claim 3 , wherein the N-MOS transistor switches the driving node of the current mirror to the ground potential in response to a high level voltage of the enable signal applied to the gate of the N-MOS transistor.

5. The optical detection apparatus according to claim 1 , further including:

a reset portion connecting the current mirror output node to the ground potential in response to an inverted enable signal.

6. The optical detection apparatus according to claim 5 , wherein the reset portion includes a gate connected to an input node receiving the inverted enable signal, a drain connected to the mirror output node, and N-MOS transistor having a source connected to the ground.

7. The optical detection apparatus according to claim 5 , further including:

a load generating unit receiving a bias voltage and converting a mirrored current of the current mirror into the current mirror output voltage.

8. The optical detection apparatus according to claim 7 , wherein the load generating unit includes two loader N-MOS transistors series-connected between the current mirror output node and the ground potential, wherein a gate of one of the loader N-MOS transistors is connected to a bias node to receive a bias voltage.

9. A liquid crystal display device, comprising:

an optical detector outputting a detector voltage in proportion to the intensity of light in response to an enable signal;

a driving controller outputting a driving control signal according to the detector voltage and a burst dimming signal;

a lamp driver converting a supply voltage into a lamp driving current having a magnitude varying in accordance with the driving control signal,

wherein optical detector includes:

an optical/electric converter transducing light incident on the optical/electric converter into a current flowing to a ground potential;

a current mirror supplying a mirror output voltage to a current mirror output node in response to an enable signal, the mirror output voltage having a magnitude proportional to the intensity of light incident on the optical/electric converter; and

a switch connecting a driving node of the current mirror to the ground potential through the optical/electric converter in response to the enable signal,

wherein the optical/electric converter includes a gate receiving a bias voltage, a drain connected to the switch, and an N-MOS transistor having a source connected to the ground potential.

10. The liquid crystal display device according to claim 9 , wherein the current mirror varies the mirror output voltage in proportion to a light intensity incident on the optical/electric converter.

11. The liquid crystal display device according to claim 9 , wherein the switch includes a gate receiving the enable signal, a drain connected to the driving node of the current minor and an N-MOS transistor having a source connected to the optical/electric converter.

12. The liquid crystal display device according to claim 11 , wherein the N-MOS transistor switches the driving node of the current mirror to the ground potential in response to a high-level voltage of the enable signal.

13. The liquid crystal display device according to claim 9 , further includes:

a reset portion connecting the mirror output node to the ground potential in response to an inverted enable signal.

14. The liquid crystal display device according to claim 13 , wherein the reset portion includes a gate connected to an input node to receive the inverted enable signal, a drain connected to the minor output node, and an N-MOS transistor having a source connected to the ground.

15. The liquid crystal display device according to claim 9 , further including:

a load generating unit receiving a bias voltage and converting a mirrored current of the current mirror into the current minor output voltage.

16. The liquid crystal display device according to claim 15 , wherein the load generating unit includes two loader N-MOS transistors series-connected between the current mirror output node and the ground potential, wherein a gate of one of the loader N-MOS transistors is connected to a bias node to receive the bias voltage.

17. The liquid crystal display device according to claim 9 , wherein the driving controller is to output a lamp driving control signal that indicates the lamp driving current needs to be decreased to the lamp driver if a voltage output from the optical detector is increased or to output the lamp driving control signal which indicates the lamp driving current needs to be increased to the lamp driver if a voltage output from the optical detector is decreased.

18. A method of driving a liquid crystal display device comprises:

providing an optical detector including:

an optical/electric converter transducing light incident on the optical/electric converter into a current flowing to a ground potential;

a current mirror supplying a mirror output voltage to a current mirror output node in response to an enable signal, the mirror output voltage having a magnitude proportional to the intensity of light incident on the optical/electric converter; and

a switch connecting a driving node of the current mirror to the ground potential through the optical/electric converter in response to the enable signal;

generating a voltage in proportion to light incident on a liquid crystal display panel of the liquid crystal display device in response to an enable signal using the optical detector;

generating a lamp driving control signal to control the amount of light emitted by the lamps correlated with a magnitude of the voltage; and

controlling the magnitude of a lamp driving current supplied to the lamps in accordance with the lamp driving control signal when the lamps are energized to emit light,

wherein the optical/electric converter includes a gate receiving a bias voltage, a drain connected to the switch, and an N-MOS transistor having a source connected to the ground potential.

19. The method of driving the liquid crystal display device according to claim 18 , wherein generating a lamp driving control signal to controlling the amount of light emitted by the lamps correlated with a magnitude of the voltage includes generating a lamp driving control signal which increases as the voltage decreases and decreases as the voltage increases.