Light sensor, display apparatus including the same, and control method thereof
There are provided a light sensor, a display apparatus including the same, and a control method thereof. The display apparatus includes: a display panel which includes a display area through which an image is displayed and a non-display area. A light receiving transistor which is formed in the non-display area and receives outside light. A charging part which includes a first terminal is connected to a drain electrode of the light receiving part and a second terminal is connected to a direct current voltage terminal. A signal amplifying part which includes a first terminal and a second terminal which is connected to a source of reference voltage and receives a reference voltage. A charging switching part is connected between the first input terminal and the first terminal of the charging part. A controller is provided which controls the charging switching part according to a predetermined first cycle to charge or discharge the charging part.
1. A light sensor for use in a display apparatus, the light sensor comprising:
a light receiving transistor which receives outside light;
a charging part which comprises a first terminal connected to a drain electrode of the light receiving transistor and a second terminal connected to a direct current terminal;
a signal amplifying part which comprises a first input terminal and a second input terminal which is connected to a reference voltage supplying part;
a charging switching part which is connected between the first input terminal and the first terminal of the charging part; and
a controller which controls the charging switching part according to a predetermined first cycle to charge or discharge the charging part.
2. The light sensor according to claim 1 , further comprising a reset switching part which comprises a first terminal connected to the first input terminal and a second terminal connected to an output terminal of the signal amplifying part,
wherein the controller controls the reset switching part according to a predetermined second cycle.
3. The light sensor according to claim 2 , further comprising an output switching part which is connected to the output terminal,
wherein the controller controls the output switching part in synchronization with turn-on of the reset switching part, and a turn-on time during which the output switching part is turned on is longer than a turn-on time during which the reset switching part is turned on.
4. The light sensor according to claim 3 , wherein the charging switching part is turned on after the reset switching part is turned off within the second cycle.
5. The light sensor according to claim 4 , wherein a turn-on time during which the charging switching part and the output switching part are simultaneously turned on is shorter than a discharging time during which the charging switching part is turned off.
6. The light sensor according to claim 2 , wherein the first cycle is the same as the second cycle.
7. The light sensor according to claim 2 , wherein the first cycle is shorter than the second cycle.
8. The light sensor according to claim 1 , wherein a voltage between a gate electrode and a source electrode of the light receiving transistor is maintained constantly.
9. The light sensor according to claim 1 , wherein the direct current terminal comprises a ground terminal.
10. The light sensor according to claim 1 , further comprising a charging voltage supplying part which supplies a charging voltage of a predetermined level to the charging part.
11. The light sensor according to claim 10 , wherein if the level of the charging voltage is higher than that of the reference voltage, the direct current terminal comprises a direct current voltage source which outputs a voltage corresponding to the level of the reference voltage.
12. The light sensor according to claim 10 , wherein the charging voltage supplying part comprises a charging voltage source which outputs the charging voltage; and
an auxiliary charging switching part which comprises a first terminal connected to the charging voltage source and a second terminal connected between the charging part and the charging switching part.
13. The light sensor according to claim 12 , wherein the auxiliary charging switching part is turned on after the charging switching part turned off within the first cycle.
14. The light sensor according to claim 1 , further comprising a signal converting part which is connected to the output terminal of the signal amplifying part and converts an output signal outputted from the signal amplifying part into a digital signal.
15. A display apparatus comprising:
a display panel which comprises a display area through which an image is displayed and a non-display area through which the image is not displayed;
a light receiving transistor which is formed in the non-display area and receives outside light;
a charging part which comprises a first terminal connected to a drain electrode of the light receiving part and a second terminal connected to a direct current terminal;
a signal amplifying part which comprises a first terminal and a second terminal which is connected to a reference voltage supplying part and receives a reference voltage;
a charging switching part which is connected between the first input terminal and the first terminal of the charging part; and
a controller which controls the charging switching part according to a predetermined first cycle to charge or discharge the charging part.
16. The display apparatus according to claim 15 , wherein the charging switching part is formed on the display panel.
17. The display apparatus according to claim 15 , wherein the display panel comprises a first substrate, a second substrate which faces the first substrate, and a light blocking layer which is formed on at least one of the first substrate and the second substrate and blocks the outside light,
the display apparatus further comprising: a dummy switching part which is formed on a branch between the first input terminal and the charging switching part; a dummy transistor which is formed below the light blocking layer and comprises a drain electrode connected to the dummy switching part; and a dummy charging part which comprises a first terminal connected to the drain electrode of the dummy transistor and a second terminal connected to a direct current terminal.
18. The display apparatus according to claim 17 , further comprising an operation part which is provided at a node connected to the charging switching part, the dummy switching part and the first input terminal, and operates a difference between current outputted from the first input terminal and current inputted to the dummy switching part.
19. A control method of a display apparatus which comprises a display panel, comprising:
providing a light receiving transistor in which a voltage between a gate electrode and a source electrode is constant and a charging part which comprises a first terminal connected to a drain electrode of the light receiving transistor and a second terminal connected to a direct current terminal;
supplying a predetermined charging voltage to charge the charging part;
stopping the charging voltage supplying for a predetermined time so that electric charges in the charging part are discharged to the light receiving transistor;
reading an output value corresponding to electric charges charged in the charging part while charging the charging part; and
controlling the brightness of the display panel on the basis of the read output value.