Liquid crystal display device and method of driving the same

1. A liquid crystal display device, comprising:

a liquid crystal panel;

a backlight unit supplying light to the liquid crystal panel;

a photo sensor detecting a brightness of an ambient surrounding the liquid crystal panel and generating a sense signal, wherein the sense signal generated by the photo sensor is a current type sense signal;

a signal processor adjusting a luminance of the light supplied by the backlight unit according to the sense signal; and

a sensor controller converting the current type sense signal to a voltage type sense signal,

wherein the sensor controller includes:

first to third thin film transistors each having a gate electrode, a source electrode and a drain electrode;

a variable element connected to the third thin film transistor;

an enable signal input terminal receiving an enable signal, the enable signal having one of high and low level voltages;

a ground terminal receiving a ground signal;

a variable signal input terminal applying a variable signal to the variable element; and

an output terminal outputting an output voltage to the signal processor,

wherein the photo sensor is connected to the ground terminal and the gate electrodes of the second and third thin film transistors.

2. The device according to claim 1 , wherein the photo sensor, the sensor controller and the signal processor are formed in the liquid crystal panel, and wherein the sensor controller, the signal processor and the liquid crystal panel include a polycrystalline silicon element.

3. The device according to claim 1 , wherein the liquid crystal panel includes a first substrate, a second substrate and a liquid crystal layer between the first and second substrates, and the photo sensor, sensor controller and the signal processor are formed on the first substrate.

4. The device according to claim 1 , wherein the variable signal adjusts a magnitude of the voltage type sense signal.

5. The device according to claim 1 , wherein the variable element includes a fourth thin film transistor connected to the third thin film transistor, and the variable signal is applied to a gate electrode of the fourth thin film transistor.

6. The device according to claim 1 , wherein the variable element includes a fourth and fifth thin film transistors connected to the third thin film transistor in series, and the variable signal is applied to gate electrodes of the fourth and fifth thin film transistors.

7. The device according to claim 6 , wherein the fourth and fifth thin film transistors include negative (N) type transistors.

8. The device according to claim 1 ,

wherein the gate electrode and the source electrode of the first thin film transistor are connected to the enable signal input terminal and the drain electrode of the first thin film transistor is connected to the gate electrodes of the second and third thin film transistors to define a node,

wherein the drain electrode of the second thin film transistor is connected to the node and the source electrode of the second thin film transistor is connected to the enable signal input terminal, and

wherein the source electrode of the third thin film transistor is connected to the enable signal input terminal and the drain electrode of the third thin film transistor is connected to the output terminal.

9. The device according to claim 8 , wherein the first to third thin film transistors include positive (P) type transistors.

10. The device according to claim 1 ,

wherein the sensor controller further includes a source terminal receiving a source voltage,

wherein the gate electrode of the first thin film transistor is connected to the enable signal input terminal, the source electrode of the first thin film transistor is connected to the source terminal and the drain electrode of the first thin film transistor is connected to the gate electrodes of the second and third thin film transistors to define a node,

wherein the drain electrode of the second thin film transistor is connected to the node and the source electrode of the second thin film transistor is connected to the enable signal input terminal, and

wherein the source electrode of the third thin film transistor is connected to the enable signal input terminal and the drain electrode of the third thin film transistor is connected to the output terminal.

11. The device according to claim 10 , wherein the first to third thin film transistors include positive (P) type transistors.

12. The device according to claim 1 ,

wherein the sensor controller further includes a source terminal receiving a source voltage and an inverter inverting the enable signal,

wherein the gate electrode of the first thin film transistor is connected to the inverter, the source electrode of the first thin film transistor is connected to the source terminal and the drain electrode of the first thin film transistor is connected to the gate electrodes of the second and third thin film transistors to define a node,

wherein the drain electrode of the second thin film transistor is connected to the node and the source electrode of the second thin film transistor is connected to the enable signal input terminal, and

wherein the source electrode of the third thin film transistor is connected to the enable signal input terminal and the drain electrode of the third thin film transistor is connected to the output terminal.

13. The device according to claim 12 , wherein the first thin film transistor includes a negative (N) type transistor, and the second and third thin film transistors include positive (P) type transistors.

14. A method of driving a liquid crystal display device, comprising:

detecting a brightness of an ambient surrounding a liquid crystal panel by a photo sensor and generating a current type sense signal;

converting the current type sense signal into a voltage type sense signal by using a sense controller,

wherein the sensor controller includes:

first to third thin film transistors each having a gate electrode, a source electrode and a drain electrode;

a variable element connected to the third thin film transistor;

an enable signal input terminal receiving an enable signal, the enable signal having one of high and low level voltages;

a ground terminal receiving a ground signal;

a variable signal input terminal applying a variable signal to the variable element; and

an output terminal outputting an output voltage to the signal processor,

wherein the photo sensor is connected to the ground terminal and the gate electrodes of the second and third thin film transistors; and

adjusting a brightness of a light supplied to the liquid crystal panel according to the voltage type sense signal.

15. The method according to claim 14 , wherein the magnitude of the voltage type sense signal is adjusted by a variable signal.