Photosensor and display device including photosensor

• US 7,423,639 B2
• Filed: 01/11/2005
• Issued: 09/09/2008
• Est. Priority Date: 01/12/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Min, Ung-Gyu
• Primary Examiner(s): TRAN, MY CHAU T
• Application Number:
  US11/032,742
• Publication Number:
  US 20050151065A1
• Time in Patent Office: 1,337 Days
• Field of Search: 345/55, 345/87, 345/90, 345/92, 345/104, 345/207
• US Class Current: 345/207
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01L 27/14678 Contact-type imagers

Abstract

A photosensor is provided, which includes: a light receiver receiving an external light and generating a photovoltage corresponding to an amount of the received light; a voltage selector selectively outputting the photovoltage and a reference voltage; a current generator generating a sensor current depending on an output voltage of the voltage selector; and an output unit selectively outputting the sensor current from the current generator.

Claims

1. A photosensor comprising:

a light receiver receiving an external light and generating a photovoltage corresponding to an amount of the received light;

a voltage selector selectively outputting the photovoltage and a reference voltage;

a current generator generating a sensor current depending on an output voltage of the voltage selector; and

an output unit selectively outputting the sensor current from the current generator, wherein the light receiver comprises;

a sensor transistor generating a photocurrent corresponding to the amount of the received light; and

a storage capacitor storing electric charges according to the photocurrent from the sensor transistor and generating the photovoltage.

2. The photosensor of claim 1, wherein the voltage selector comprises a selection transistor applying the reference voltage to the current generator in response to a selection signal.

3. The photosensor of claim 2, wherein the current generator comprises a current generating transistor generating the sensor current.

4. The photosensor of claim 3, wherein the selection transistor has an input terminal supplied with the reference voltage, a control terminal supplied with a selection signal, and an output terminal connected to the current generating transistor.

5. The photosensor of claim 4, wherein the current generating transistor comprises an input terminal supplied with the reference voltage, a control terminal connected to an output terminal of the light receiver and the output terminal of the selection transistor, and an output terminal outputting the sensor current.

6. The photosensor of claim 5, wherein the selection transistor applies the reference voltage to the control terminal of the current generating transistor when the selection transistor turns on, and applies the photovoltage to the control terminal of the current generating transistor when the selection transistor turns off.

7. The photosensor of claim 1, wherein the sensor transistor has a control terminal and an output terminal and the storage capacitor is connected between the control terminal and the output terminal of the sensor transistor.

8. The photosensor of claim 7, wherein the control terminal of the sensor transistor is supplied with an off voltage for turning off the sensor transistor.

9. The photosensor of claim 1, wherein the output unit comprises an output transistor outputting the sensor current in response to a read signal.

10. The photosensor of claim 1, wherein the output unit comprises an output transistor outputting the sensor current in response to a read signal.

11. The photo sensor of claim 10, further comprising a converting unit converting the sensor current into a sensor voltage.

12. The photosensor of claim 11, wherein the converting unit comprises a resistor or a capacitor.

13. A display device comprising:

a photosensor generating a sensor current based on an amount of received light;

a voltage converter converting the sensor current from the photosensor to a control voltage;

a display panel including a plurality of pixels; and

a controller controlling luminance of the display panel based on the control voltage,

wherein the photosensor comprises;

a light receiver outputting a photovoltage corresponding to the amount of the received light;

a voltage selector selectively outputting the photovoltage and a reference voltage;

a current generator generating the sensor current depending on an output of the voltage selector; and

an output unit selectively outputting the sensor current from the current generator,

wherein the light receiver comprises;

a sensor transistor generating a photocurrent corresponding to the amount of the received light; and

a storage capacitor storing electric charges according to the photocurrent from the sensor transistor and generating the photovoltage.

14. The display device of claim 13, wherein the voltage selector comprises a selection transistor applying the reference voltage to the current generator in response to a selection signal.

15. The display device of claim 14, wherein the current generator comprises a current generating transistor generating the sensor current.

16. The display device of claim 13, wherein the output unit comprises an output transistor outputting the sensor current in response to a read signal.

17. The display device of claim 16, wherein the selection transistor applies the reference voltage to the storage capacitor and the control terminal of the current generating transistor when the selection signal is in a first level, and applies the photovoltage to the control terminal of the current generating transistor when the selection signal is in a second level.

18. The display device of claim 17, wherein the output transistor outputs the sensor current when the read signal is in the first level.

19. The display device of claim 18, further comprising a signal controller processing image signals for the pixels and generating the selection signal and the read signal to be provided for the photosensor.

20. The display device of claim 19, wherein the signal controller applies the selection signal to a control terminal of the selection transistor and applies the read signal to a control terminal of the output transistor.

21. The display device of claim 20, wherein the read signal has the first level twice between two successive levels of the selection signal.

22. The display device of claim 21, wherein the photo sensor outputs the sensor current corresponding to the reference voltage when the read signal firstly reaches the first level.

23. The display device of claim 22, wherein the photosensor outputs the sensor current corresponding to the light amount when the read signal secondly reaches the first level.

24. The display device of claim 13, wherein the voltage converter comprises:

a first converter converting the sensor current into a sensor voltage; and

a second converter converting the sensor voltage to the control voltage.

25. The display device of claim 24, wherein the first converter comprises a resistor or a capacitor.

26. The display device of claim 24, wherein the second converter comprises an inverting amplifier.

27. The display device of claim 24, wherein the second converter comprises:

an analog-to-digital converter converting the sensor voltage into digital values; and

a multiplexer selecting the control voltage based on the digital values.

28. The display device of claim 24, wherein the voltage converter further comprises a buffer connected between the first converter and the second converter.

29. The display device of claim 13, wherein the photosensor is incorporated into the display panel.

30. The display device of claim 13, wherein the photosensor is incorporated into a periphery of the display panel.

31. The display device of claim 13, wherein the controller comprises a light source illuminating the display panel.

32. The display device of claim 13, wherein the display device comprises one of a liquid crystal display, an organic light emitting display, and a plasma display panel.

33. The display device of claim 13, wherein each pixel comprises at least one active switching element.