Display device and drive current detection method for same

Patent metadata

Field	Value
Publication number	US-2016055791-A1
Application number	US-201414784391-A
Country	US
Kind code	A1
Filing date	Mar 4, 2014
Priority date	Apr 23, 2013
Publication date	Feb 25, 2016
Grant date	—

Abstract

A data line drive circuit provides a voltage according to a detection voltage and to a reference voltage, between the gate and source of a drive transistor in a pixel circuit, and detects a drive current having passed through the drive transistor and outputted external to the pixel circuit. A threshold voltage correction memory stores, for each pixel circuit, data representing a threshold voltage of the drive transistor. A display control circuit controls the reference voltage based on the data stored in the threshold voltage correction memory. By this, even if the threshold voltage of the drive transistor is changed, the drive current can be detected with a high accuracy. The threshold voltage correction memory may store, for each pixel circuit, data representing a difference between the threshold voltage of the drive transistor and the reference voltage.

First claim

1 . An active matrix-type display device comprising:
a display unit including a plurality of scanning lines, a plurality of data lines, and a plurality of pixel circuits provided at respective intersections of the scanning lines and the data lines; a scanning line drive circuit configured to drive the scanning lines; a data line drive circuit configured to drive the data lines; and a display control circuit, wherein each of the pixel circuits includes an electro-optical element and a drive transistor provided in series with the electro-optical element, upon current detection, the data line drive circuit is configured to provide a voltage between a control terminal and a first conduction terminal of the drive transistor, and detect a drive current having passed through the drive transistor and outputted external to the pixel circuit, the voltage being according to a detection voltage and a reference voltage, and the display control circuit is configured to control the reference voltage.

2 . The display device according to claim 1 , further comprising a storage unit configured to store, for each of the pixel circuits, data according to a threshold voltage of the drive transistor, wherein
the display control circuit is configured to control the reference voltage based on the data stored in the storage unit.

3 . The display device according to claim 2 , wherein the display control circuit is configured to determine a statistical value of the threshold voltages of the drive transistors based on the data stored in the storage unit, and control the reference voltage based on the determined statistical value.

4 . The display device according to claim 3 , wherein the storage unit is configured to store, for each of the pixel circuits, data representing a difference between the statistical value of the threshold voltages of the drive transistors and the reference voltage.

5 . The display device according to claim 2 , wherein the display control circuit is configured to update the data stored in the storage unit, based on results of the detection by the data line drive circuit.

6 . The display device according to claim 5 , wherein the display control circuit is configured to perform a correction process on video data, using the data stored in the storage unit, the correction process compensating for the threshold voltage and a gain of the drive transistor.

7 . The display device according to claim 5 , wherein the display control circuit is configured to perform a correction process on video data, using the data stored in the storage unit, the correction process compensating for the threshold voltage of the drive transistor.

8 . The display device according to claim 1 , wherein the display control circuit is configured to measure cumulative lighting time and control the reference voltage based on the measured cumulative lighting time.

9 . The display device according to claim 1 , wherein
the display unit further includes a characteristic detection transistor, and the display control circuit is configured to control the reference voltage based on a characteristic of the characteristic detection transistor.

10 . The display device according to claim 1 , wherein
the display unit further includes reference voltage lines configured to supply the reference voltage to the pixel circuits, and upon current detection, the data line drive circuit is configured to provide the detection voltage to each of the data lines and detect a drive current having flowed through the data line from the pixel circuit.

11 . The display device according to claim 10 , wherein
each of the pixel circuits further includes: a reference voltage application transistor provided between a corresponding reference voltage line and the control terminal of the drive transistor, and having a control terminal connected to a corresponding scanning line; an input/output transistor provided between a corresponding data line and the first conduction terminal of the drive transistor, and having a control terminal connected to the scanning line; and a capacitive element provided between the control terminal and first conduction terminal of the drive transistor.

12 . The display device according to claim 1 , wherein
the display unit further includes a plurality of monitoring lines, and upon current detection, the data line drive circuit is configured to provide a voltage to each of the data lines and detect a drive current having flowed through a corresponding monitoring line from the pixel circuit, the voltage being obtained by adding the reference voltage to the detection voltage.

13 . The display device according to claim 1 , wherein
the display unit further includes a plurality of monitoring lines, and upon current detection, the data line drive circuit is configured to provide the detection voltage to each of the data lines and provide the reference voltage to each of the monitoring lines, and detect a drive current having flowed through the monitoring line from the pixel circuit.

14 . The display device according to claim 12 or 13 , wherein
each of the pixel circuits further includes:
an input transistor provided between a corresponding data line and the control terminal of the drive transistor, and having a control terminal connected to a corresponding scanning line;
an output transistor provided between a corresponding monitoring line and the first conduction terminal of the drive transistor, and having a control terminal connected to the scanning line; and
a capacitive element provided between the control terminal and first conduction terminal of the drive transistor.

15 . The display device according to claim 1 , wherein
the scanning lines are divided into one or more blocks, for each block, the scanning line drive circuit is configured to select all or some of scanning lines in the block collectively during a first period, and select all of the scanning lines in the block in turn during a second period, and for each block, the data line drive circuit is configured to convert drive currents outputted external to corresponding pixel circuits into voltages during the first period, and apply voltages to the data lines during the second period, the voltages being based on voltages according to video data and on the voltages obtained during the first period.

16 . The display device according to claim 1 , wherein the drive transistors are thin film transistors in which a semiconductor layer is formed of an oxide semiconductor.

17 . The display device according to claim 16 , wherein the oxide semiconductor is indium gallium zinc oxide.

18 . The display device according to claim 17 , wherein the indium gallium zinc oxide has crystallinity.

19 . A drive current detection method for an active matrix-type display device having a display unit including a plurality of scanning lines, a plurality of data lines, and a plurality of pixel circuits provided at respective intersections of the scanning lines and the data lines,
when each of the pixel circuits includes an electro-optical element and a drive transistor provided in series with the electro-optical element, the method comprising the steps of: providing a voltage between a control terminal and a first conduction terminal of the drive transistor by driving a corresponding scanning line and a corresponding data line, the voltage being according to a detection voltage and a reference voltage; detecting a drive current having passed through the drive transistor and outputted external to t

Assignees

• Sharp Kk

Inventors

• Kishi Noritaka
• Katsui Hiromitsu
• Noguchi Noboru
• Ohara Masanori
• Yamanaka Shigetsugu
• Ohta Yoshifumi

Classifications

• G09G2320/0285

  using tables for spatial correction of display data · CPC title

• G09G3/30 Primary

  using electroluminescent panels · CPC title

• G09G2330/021

  Power management, e.g. power saving · CPC title

• G09G3/3266

  Details of drivers for scan electrodes · CPC title

• G09G2320/045

  Compensation of drifts in the characteristics of light emitting or modulating elements · CPC title