Display device and drive method for same

Patent metadata

Field	Value
Publication number	US-9430968-B2
Application number	US-201414787793-A
Country	US
Kind code	B2
Filing date	Jun 20, 2014
Priority date	Jun 27, 2013
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

There is realized a display device capable of compensating for a deterioration of a circuit element while suppressing an increase of a circuit scale. One horizontal scanning period for a monitor row is composed of: a detection preparation period where preparation for detecting TFT characteristics and OLED characteristics is performed in the monitor row; a TFT characteristic detection period where current measurement for detecting the TFT characteristics is performed; an OLED characteristic detection period where current measurement for detecting the OLED characteristics is performed; and a light emission preparation period where preparation for allowing an organic EL element to emit light is performed in the monitor row. Data lines are used not only as signal lines that transfer a signal for allowing an organic EL element in each pixel circuit to emit light at desired brightness, but also as characteristic detecting signal lines.

First claim

The invention claimed is:

1. An active matrix-type display device comprising:
a display unit including: a pixel matrix of n rows and m columns (n and m are integers of 2 or more), which is composed of n×m pieces of pixel circuits each including an electro-optical element in which brightness is controlled by a current and including a drive transistor for controlling a current to be supplied to the electro-optical element; scanning lines provided to correspond to respective rows of the pixel matrix; monitor control lines provided to correspond to the respective rows of the pixel matrix; and data lines provided to correspond to respective columns of the pixel matrix;
a pixel circuit drive unit configured to drive the scanning lines, the monitor control lines and the data lines so that characteristic detection processing for detecting characteristics of characteristic detection-target circuit elements including at least either of the electro-optical element and the drive transistor is performed in a frame period, and that each electro-optical element emits light in response to target brightness;
a correction data storage unit configured to store characteristic data, which are obtained based on results of the characteristic detection processing, as correction data for correcting video signals; and
a video signal correction unit configured to correct the video signals based on the correction data stored in the correction data storage unit, and to generate data signals to be supplied to the n×m pieces of pixel circuits,
wherein each of the pixel circuits includes:
the electro-optical element;
an input transistor, in which a control terminal is connected to one of the scanning lines, a first conductive terminal is connected to one of the data lines, and a second conductive terminal is connected to the control terminal of the drive transistor;
a monitor control transistor, in which a control terminal is connected to one of the monitor control lines, a first conductive terminal is connected to the second conductive terminal of the drive transistor and to the anode of the electro-optical element, and a second conductive terminal is connected to one of the data lines;
the drive transistor in which a first conductive terminal is given a drive power supply potential; and
a first capacitor in which one end is connected to a control terminal of the drive transistor in order to hold a potential of the control terminal of the drive transistor,
wherein, when a row in which the characteristic detection processing is performed in the frame period is defined as a monitor row, and each of rows other than the monitor row is defined as a non-monitor row, the frame period includes a characteristic detection processing period composed of: a detection preparation period where a preparation for detecting characteristics of the characteristic detection-target circuit elements is performed in the monitor row; a current measurement period where the characteristics of the characteristic detection-target circuit elements are detected by measuring currents flowing through the data lines; and a light emission preparation period where a preparation for allowing the electro-optical element to emit light is performed in the monitor row,

the pixel circuit drive unit drives the scanning lines so that the input transistor becomes an ON state during the detection preparation period and the light emission preparation period, and that the input transistor becomes an OFF state during the current measurement period,
the pixel circuit drive unit drives the monitor control lines so that the monitor control transistor becomes an OFF state during the detection preparation period and the light emission preparation period, and that the monitor control transistor becomes an ON state during the current measurement period,
the pixel circuit drive unit gives the data lines a first predetermined potential during the detection preparation period, the first predetermined potential being determined based on the characteristics of the electro-optical element and the characteristics of the drive transistor,
the pixel circuit drive unit gives the data lines a second predetermined potential during the current measurement period, the second predetermined potential serving for allowing a current in accordance with the characteristics of each of the characteristic detection-target circuit elements to flow through each of the data lines, and
the pixel circuit drive unit gives the data lines a potential in accordance with a target brightness of the electro-optical element during the light emission preparation period.

2. The display device according to claim 1 ,
wherein the pixel circuit drive unit includes output and current-monitor circuits having a function to apply the data signals to the data lines, and a function to measure the currents flowing through the data lines,
each of the output and current-monitor circuits includes:
an operational amplifier, in which a non-inverting input terminal is given one of the data signals, and an inverting input terminal is connected to one of the data lines;
a second capacitor, in which one end is connected to one of the data lines, and other end is connected to an output terminal of the operational amplifier; and
a switch, in which one end is connected to one of the data lines, and other end is connected to the output terminal of the operational amplifier, and

each of the output and current-monitor circuits measure currents flowing through the data lines by allowing the switch to be turned to OFF state after giving the data lines the second predetermined potential by allowing the switch to be turned to ON state, in the current measurement period.

3. The display device according to claim 2 ,
wherein one output and current-monitor circuit is provided for a plurality of the data lines, and
the plurality of data lines are electrically connected sequentially to the output and current-monitor circuits every predetermined period.

4. The display device according to claim 1 , wherein the characteristic detection processing period is provided in a vertical scanning period.

5. The display device according to claim 4 , wherein, when any electro-optical element is defined as a focus-target electro-optical element, in a case where the focus-target electro-optical element is included in the monitor row, the pixel circuit drive unit gives the data lines a potential of a data signal during the light emission preparation period, the potential being equivalent to a gradation voltage larger than a gradation voltage in a case where the focus-target electro-optical element is included in the non-monitor row.

6. The display device according to claim 1 , wherein the characteristic detection processing period is provided in a vertical retrace line period.

7. The display device according to claim 6 , wherein, when any electro-optical element is defined as a focus-target electro-optical element, in a case where the focus-target electro-optical element is included in the monitor row, the pixel circuit drive unit gives the data lines a potential of a data signal in an event of performing writing of the data signals to pixel circuits included in the monitor row in a vertical scanning period, the potential being equivalent to a gradation voltage larger than a gradation voltage in a case where the focus-target electro-optical element is included in the non-monitor row.

8. The display device according to claim 1 , wherein the characteristic detection processing is performed for only one row of the pixel matrix for one frame period.

9. The display device according to claim 1 , wherein there are: a frame in which detection of the characteristics of only the drive transistor as the

Assignees

• Sharp Kk

Inventors

• Kishi Noritaka
• Noguchi Noboru
• Ohara Masanori

Classifications

• G09G2330/021

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

• G09G2320/041

  Temperature compensation · CPC title

• G09G2320/045

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

• G09G2320/029

  by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel · CPC title

• G09G2300/0819

  used for counteracting undesired variations, e.g. feedback or autozeroing · CPC title