Light sensing circuit, touch panel including the same, and method of driving the same

• US 8,451,251 B2
• Filed: 03/09/2010
• Issued: 05/28/2013
• Est. Priority Date: 07/03/2009
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Choi, Deok-Young, Park, Yong-Sung, Kim, Do-Youb, Ahn, Soon-Sung, Choi, In-Ho
• Primary Examiner(s): SHENG, TOM V
• Application Number:
  US12/720,204
• Publication Number:
  US 20110001711A1
• Time in Patent Office: 1,176 Days
• Field of Search: 345/173, 345/175, 345/179, 345/182, 345/204, 345/207, 178/18.09, 178/19.05
• US Class Current: 345/175
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

A light sensing circuit includes a photodiode including a cathode electrode and an anode electrode and for receiving light from the outside and generating a current corresponding to the received light, a driving transistor for amplifying the current generated in the photodiode, a capacitor for storing a first initiation voltage transmitted to the driving transistor, a first switching transistor for compensating for a threshold voltage of the driving transistor corresponding to a current scan signal, and a second switching transistor for transmitting the first initiation voltage corresponding to the current scan signal.

Claims

1. A light sensing circuit for amplifying a current of a photodiode, comprising:

a photodiode comprising a cathode electrode and an anode electrode and for receiving light from the outside and generating a current corresponding to the received light;

a driving transistor for amplifying the current generated in the photodiode;

a capacitor for storing a first initiation voltage transmitted to the driving transistor;

a first switching transistor for compensating for a threshold voltage of the driving transistor corresponding to a current scan signal; and

a second switching transistor for transmitting the first initiation voltage corresponding to the current scan signal by diode connecting the driving transistor.

2. The light sensing circuit of claim 1, wherein the driving transistor is a PMOS transistor having a gate electrode connected to one terminal of the capacitor, a source electrode connected to the second switching transistor, and a drain electrode connected to the first switching transistor.

3. The light sensing circuit of claim 1, wherein the first switching transistor is a PMOS transistor having a source electrode connected to a drain electrode of the driving transistor and a drain electrode connected to a gate electrode of the driving transistor, and for compensating for a threshold voltage of the driving transistor by diode connecting the driving transistor corresponding to the current scan signal.

4. The light sensing circuit of claim 1, further comprising a third switching transistor for transmitting a second initiation voltage which initiates a voltage of the cathode electrode of the photodiode and a voltage at a gate electrode of the driving transistor corresponding to a previous scan signal received before the current scan signal.

5. The light sensing circuit of claim 4, further comprising a fourth switching transistor for transmitting a power source voltage to the driving transistor corresponding to an emission signal.

6. The light sensing circuit of claim 5, wherein the second initiation voltage and the power source voltage are respectively the same as a corresponding initiation voltage and a corresponding power source voltage of a separate pixel driving circuit which drives a plurality of pixels.

7. The light sensing circuit of claim 5, wherein the fourth switching transistor is comprised in a pixel emission driver which transmits an emission signal to a separate pixel driving circuit which drives a plurality of pixels.

8. The light sensing circuit of claim 1, further comprising a third switching transistor for transmitting the current amplified through the driving transistor via an output line corresponding to a light integration signal.

9. The light sensing circuit of claim 8, further comprising a fourth switching transistor for resetting a voltage of the output line to a ground voltage corresponding to a reset signal.

10. The light sensing circuit of claim 1, wherein the second switching transistor is comprised in a pixel scan driver which transmits a scan signal to a separate pixel driving circuit which drives a plurality of pixels.

11. A touch panel comprising a pixel driving circuit for driving a plurality of pixels for displaying images and a light sensing circuit for detecting a touch, wherein the light sensing circuit comprises a photodiode comprising a cathode electrode and an anode electrode and for receiving light from the outside and generating a current corresponding to the received light;

a driving transistor for amplifying the current generated in the photodiode;

a capacitor for storing a first initiation voltage transmitted to the driving transistor;

a first switching transistor for compensating for a threshold voltage of the driving transistor corresponding to a current scan signal; and

a second switching transistor for transmitting the first initiation voltage corresponding to the current scan signal by diode connecting the driving transistor.

12. The touch panel of claim 11, wherein the driving transistor is a PMOS transistor having a gate electrode connected to one terminal of the capacitor, a source electrode connected to the second switching transistor, and a drain electrode connected to the first switching transistor.

13. The touch panel of claim 11, wherein the first switching transistor is a PMOS transistor having a source electrode connected to a drain electrode of the driving transistor and a drain electrode connected to a gate electrode of the driving transistor, and for compensating for a threshold voltage of the driving transistor by diode connecting the driving transistor corresponding to the current scan signal.

14. The touch panel of claim 11, further comprising a third switching transistor for transmitting a second initiation voltage of the pixel driving circuit corresponding to a previous scan signal received before the current scan signal for initiating a voltage of the cathode electrode of the photodiode and a voltage at a gate electrode of the driving transistor.

15. The touch panel of claim 11, further comprising a third switching transistor for transmitting a power source voltage of the pixel driving circuit to the driving transistor corresponding to an emission signal for the pixel driving circuit.

16. The touch panel of claim 11, further comprising a third switching transistor for transmitting the current amplified by the driving transistor through an output line corresponding to a light integration signal.

17. The touch panel of claim 16, further comprising a fourth switching transistor for resetting a voltage of the output line to a ground voltage corresponding to a reset signal.

18. A method of driving a light sensing circuit, the method comprising:

initiating a predetermined voltage at a gate electrode of a driving transistor and at a cathode electrode of a photodiode corresponding to a previous scan signal;

diode connecting the driving transistor and storing a first initiation voltage transmitted to the driving transistor to a capacitor corresponding to a current scan signal;

applying a power source voltage to a source electrode of the driving transistor corresponding to an emission signal and adjusting the first initiation voltage stored in the capacitor corresponding to a current generated in the photodiode; and

amplifying the current generated in the photodiode and outputting the amplified current corresponding to a light integration signal.

19. The method of claim 18, wherein the light sensing circuit compensates for a deviation of a threshold voltage of the driving transistor.