Display panel and display device

• US 7,245,277 B2
• Filed: 07/09/2003
• Issued: 07/17/2007
• Est. Priority Date: 07/10/2002
• Status: Active Grant

• Current Assignee: Pioneer Corporation
• Original Assignee: Pioneer Corporation
• Inventors: Ishizuka, Shinichi
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): FATAHI YAR, MAHMOUD
• Application Number:
  US10/615,396
• Publication Number:
  US 20040051684A1
• Time in Patent Office: 1,469 Days
• Field of Search: 345/76, 315/169.3
• US Class Current: 345/78
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

An active type display panel comprises a plurality of pixel sections each having a series circuit constituted by a light emitting element and a drive element for supplying a drive current to the light emitting element, a pair of power supply lines which connect the series circuits of the pixel sections in parallel, and a plurality of measurement lines. Each of the pixel sections includes a switch element between a point connecting the light emitting element and the drive element, and one line of the measurement lines. A display device, in which the display panel is used, detects the voltage across the terminals of the light emitting element and controls the drive element such that the voltage across these terminals is a predetermined voltage.

Claims

1. An active type display panel comprising a plurality of data lines, a plurality of scan lines mutually intersecting said plurality of data lines, a plurality of pixel sections which are formed at respective intersection points of the data lines and the scan lines and each include a series circuit in which a light emitting element and a drive element which supplies a drive current to said light emitting element are connected in series, and a pair of power supply lines which connect the series circuits of said plurality of pixel sections in parallel;

wherein each of said plurality of pixel sections further comprises a switch element of which one end is connected to a point connecting said light emitting element and said drive element, and a pixel controller which activates said drive element in accordance with an input signal on a corresponding data line during a scanning period to supply a drive current of a level corresponding to the input signal to said light emitting element, and

wherein said display panel further comprises for each of the data lines;

a switching portion which supplies a reference current to the light emitting element through said switch element during a first time period of the scanning period and halts the supply of said reference current in a second time period which remains in the scanning period to permit the activation of the drive element;

a holding portion which holds a voltage across the terminals of said light emitting element through said switch element during said first time period;

a comparator which generates, during the second time period, a correction voltage corresponding to the difference between the voltage held in the holding portion and the voltage across the terminals of said light emitting element;

and

an outputting portion which supplies the correction voltage to the corresponding data line during said second time period.

2. A display panel according to claim 1 further comprises a plurality of measurement lines of which the number is equal to the number of said data lines,

wherein said drive element is a first field effect transistor of which the source is connected to one line of the pair of power supply lines,

wherein said pixel controller comprises:

a second field effect transistor, of which the gate is connected to one scan line of said plurality of scan lines, the source is connected to one data line of said plurality of data lines, and the drain is connected to the gate of said first field effect transistor; and

a capacitor connected between one line of the pair of power supply lines, and a line connecting the gate of said first field effect transistor and the drain of said second field effect transistor,

wherein said light emitting element is an organic electroluminescence element of which the anode is connected to the drain of said first field effect transistor and the cathode is connected to the other line of the pair of power supply lines; and

wherein said switch element is a third field effect transistor of which the gate is connected to the one scan line, the source is connected to one measurement line of said plurality of measurement lines to supply a reference current to the light emitting element by said switching portion and to provide the voltage across the terminals of said light emitting element to said holding portion and said comparator, and the drain is connected to a line connecting the drain of said first field effect transistor and the anode of said organic electroluminescence element.

3. A display device comprising:

an active type display panel comprising a plurality of data lines, a plurality of scan lines mutually intersecting said plurality of data lines, and a plurality of pixel sections each including a series circuit in which a light emitting element and a drive element which supplies a drive current to said light emitting element are connected in series, and which is connected between one of said plurality of data lines and one of said plurality of scan lines at an intersection thereof;

a power voltage supply portion which applies a power voltage to said series circuit of each of said pixel sections; and

a display controller which designates one scan line of said plurality of scan lines sequentially with predetermined timing in accordance with an input image signal, supplies a scan pulse to the designated one scan line, and supplies a data signal indicating light emission luminance to at least one data line of said plurality of data lines in a scanning period during which the scan pulse is supplied, the at least one data line corresponding to at least one light emitting element to be emitted light on the designated one scan line,

wherein each of said plurality of pixel sections includes a switch element of which one end is connected to a point connecting said light emitting element and said drive element, and a pixel controller which activates said drive element response to the data signal on a corresponding data line during a scanning period to supply a drive current of a level corresponding to the data signal to said light emitting element,

wherein said display panel further comprises for each of a plurality of data lines;

a switching portion supplies a reference current to the light emitting element through said switch element during a first time period in the scanning period and halts the supply of said reference current in a second time period in the scanning period to permit the activation of the drive element;

a holding portion which holds a voltage across the terminals of said light emitting element through said switch element during said first time period;

a comparator which generates, during the second time period, a correction voltage corresponding to the difference between the voltage held in the holding portion and the voltage across the terminals of said light emitting element; and

an outputting portion which supplies the correction voltage to the corresponding data line during said second time period.

4. A display device according to claim 3, wherein said display panel further comprises a plurality of measurement lines,

wherein said drive element consists of a first field effect transistor of which the source is connected to the positive output terminal of said power voltage supply portion, and

wherein said pixel controller comprises:

a second field effect transistor of which the gate is connected to the scan line for a corresponding column of said plurality of scan lines, the source is connected to the data line for a corresponding row of said plurality of data lines, and the drain is connected to the gate of said first field effect transistor;

a first capacitor connected between the positive output terminal of said power voltage supply portion, and a line connecting the gate of said first field effect transistor and the drain of said second field effect transistor;

an organic electroluminescence element which is provided as said light emitting element and of which the anode is connected to the drain of said first field effect transistor and the cathode is connected to the negative output terminal of said power voltage supply portion; and

a third field effect transistor which is provided as said voltage detector and of which the gate is connected to the scan line for the corresponding column, the source is connected to the measurement line for the corresponding row of said plurality of measurement lines, and the drain is connected to a line connecting the drain of said first field effect transistor and the anode of said organic electroluminescence element,

wherein the voltage across the terminals of said light emitting element is supplied to said data correction portion as an anode voltage of said organic electroluminescence element through the drain and source of said third field effect transistor and the measurement line for the corresponding row,

and wherein each of said pixel sections includes a current generation circuit for generating a reference current of a level corresponding to the data signal; and

wherein said switching portion halts activation of said drive element by said pixel controller by supplying the reference current in the first time period appearing first in the scanning period during which the scan pulse is supplied, to said organic electroluminescence element through the measurement line for the corresponding row and through the source and drain of said third field effect transistor, and for permitting activation of said drive element by said pixel controller by halting the supply of the reference current to said organic electroluminescence element in the second time period which remains in the scanning period.

5. A display device according to claim 4, wherein said display panel further comprises for each of a plurality of data lines another switching portion which supplies a voltage required for halting activation of said drive element by said pixel controller, to the source of said second field effect transistor during the first time period.

6. A display device according to claim 5, where the voltage required for halting the activation of said drive element is a voltage equal to the power voltage.

7. A driving method for an active type display panel comprising a plurality of data lines, a plurality of scan lines mutually intersecting said plurality of data lines, and a plurality of pixel sections each including a series circuit in which a light emitting element and a drive element for supplying a drive current to said light emitting element are connected in series, and which is connected between one of said plurality of data lines and one of said plurality of scan lines at an intersection thereof;

comprising the steps of;

applying a power voltage to said series circuit of each of said pixel sections;

designating one scan line of said plurality of scan lines sequentially with predetermined timing in accordance with an input image signal, supplying a scan pulse to the designated one scan line, and supplying a data signal indicating light emission luminance to at least one data line of said plurality of data lines in a scanning period during which the scan pulse is supplied, the at least one data line corresponding to at least one light emitting element to be emitted light on the designated one scan line;

wherein said driving method further comprises the steps of in each of said pixel sections;

supplying a reference current to the light emitting element through a switch element during a first time period in the scanning period and halting the supply of said reference current in a second time period in the scanning period to permit the activation of the drive element;

holding a voltage across the terminals of said light emitting element through said switch element during said first time period;

generating, during the second time period, a correction voltage corresponding to the difference between the voltage held in the holding step and the voltage across the terminals of said light emitting element; and

supplying the correction voltage to the corresponding data line.

8. An active type display panel comprising a plurality of data lines, a plurality of scan lines mutually intersecting said plurality of data lines, a plurality of pixel sections which are formed at respective intersection points of the data lines and the scan lines and each include a series circuit in which a light emitting element and a drive element which supplies a drive current to said light emitting element are connected in series, a pair of power supply lines which connect the series circuits of said plurality of pixel sections in parallel, and a plurality of measurement lines;

wherein each of said plurality of pixel sections further comprises a switch element of which one end is connected to a point connecting said light emitting and said drive element and of which another end is connected to one measurement line of said plurality of measurement lines.

9. A display panel according to claim 8, wherein the number of said plurality of measurement lines is equal to the number of said data lines,

wherein said drive element is a first field effect transistor of which the source is connected to one line of the pair of power supply lines,

wherein said display panel further comprises:

a second field effect transistor, of which the gate is connected to one scan line of said plurality of scan lines, the source is connected to one data line of said plurality of data lines, and the drain is connected to the gate of said first field effect transistor; and

a capacitor connected between one line of the pair of power supply lines, and a line connecting the gate of said first field effect transistor and the drain of said second field effect transistor,

wherein said light emitting element is an organic electroluminescence element of which the anode is connected to the drain of said first field effect transistor and the cathode is connected to the other line of the pair of power supply lines, and

wherein said switch element is a third field effect transistor of which the gate is connected to the one scan line, the source is connected to the one measurement line and the drain is connected to a line connecting the drain of said first field effect transistor and the anode of said organic electroluminescence element.