Pixel circuit, active matrix apparatus and display apparatus

• US 20050269959A1
• Filed: 05/31/2005
• Published: 12/08/2005
• Est. Priority Date: 06/02/2004
• Status: Active Grant

• Current Assignee: Sony Group Corp.
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamashita, Junichi, Yamamoto, Tetsuro, Uchino, Katsuhide
• Granted Patent: US 7,173,590 B2
• Time in Patent Office: Days
• US Class Current: 315/169.300
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4268 Cooling of semiconductor devices H01L23/24; of electric apparatus H05K7/20; of instruments G12B15/00
• CPC Class Codes: G02B 6/4272 with mounting substrates of high thermal conductivity
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0216 Interleaved control phases for different scan lines in the same sub-field, e.g. initialization, addressing and sustaining in plasma displays that are not simultaneous for all scan lines
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• 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 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/30 using electroluminescent panels
• CPC Class Codes: G09G 3/3233 : with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 : with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 : Details of drivers for scan electrodes
• 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
• CPC Class Codes: H01L 2224/16225 : the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2924/15192 : Resurf arrangement of the internal vias
• CPC Class Codes: H01L 2924/15311 : being a ball array, e.g. BGA
• CPC Class Codes: H04B 10/501 : Structural aspects

Abstract

A pixel circuit having a function of compensating for characteristic variation of an electro-optical element and threshold voltage variation of a transistor is formed from a reduced number of component elements. The pixel circuit includes an electro-optical element, a holding capacitor, and five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, and first and second detection transistors. The sampling transistor samples and supplies an input signal from a signal line so as to be held into the holding capacitor. The driving transistor drives the electro-optical element with current in response to the held signal potential. The first and second detection transistors detect a threshold voltage of the drive transistor and supply the detected voltage into the holding capacitor in order to cancel an influence of the threshold voltage in advance.

Claims

1. A pixel circuit disposed at a point at which a scanning line and a signal line intersect with each other, comprising:

an electro-optical element;

a holding capacitor; and

five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, a first detection transistor and a second detection transistor;

wherein,

said holding capacitor being connected between the source and the gate of said drive transistor;

said electro-optical element being connected between the source of said drive transistor and a predetermined cathode potential;

said first detection transistor being connected between the source of said drive transistor and a first ground potential;

said second detection transistor being connected between the gate of said drive transistor and a second ground potential;

said sampling transistor being connected between said gate of said drive transistor and said signal line;

said switching transistor being connected between the drain of said drive transistor and a predetermined power supply potential;

said sampling transistor operating, when selected by said scanning line, to sample an input signal from said signal line and supply the sampled input signal so as to be held into said holding capacitor;

said drive transistor driving said electro-optical element with current in response to the signal potential held by said holding capacitor;

said switching transistor being rendered conducting, when selected by said scanning line, to supply current from said power supply potential to said drive transistor; and

said first and second detection transistors operating, when selected by said scanning line, to detect a threshold voltage of said drive transistor prior to the driving of said electro-optical element with the current and supply the detected potential so as to be held into said holding capacitor in order to cancel an influence of the threshold voltage in advance.

2. The pixel circuit according to claim 1, wherein said first ground potential is set lower than a level calculated by subtracting the threshold voltage of said drive transistor from said second ground potential, and a level calculated by adding the threshold voltage of said electro-optical element to said cathode potential is set higher than a level calculated by subtracting the threshold voltage of said drive transistor from said first ground potential.

3. The pixel circuit according to claim 2, wherein the level of said second ground potential is set to a value in the proximity of the lowest level of the input signal supplied from said signal line.

4. An active matrix apparatus, comprising:

a plurality of scanning lines extending along rows;

a plurality of signal lines extending along columns; and

a plurality of pixels disposed in a matrix at points at which said scanning lines and said signal lines intersect with each other;

wherein,

each of said pixels including a load element, a holding capacitor, and five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, a first detection transistor and a second detection transistor;

said holding capacitor being connected between the source and the gate of said drive transistor;

said load element being connected between the source of said drive transistor and a predetermined cathode potential;

said first detection transistor being connected between the source of said drive transistor and a first ground potential;

said second detection transistor being connected between the gate of said drive transistor and a second ground potential;

said sampling transistor being connected between said gate of said drive transistor and said signal line;

said switching transistor being connected between the drain of said drive transistor and a predetermined power supply potential;

said sampling transistor operating, when selected by said scanning line, to sample an input signal from said signal line and supply the sampled input signal so as to be held into said holding capacitor;

said drive transistor driving said load element with current in response to the signal potential held by said holding capacitor;

said switching transistor being rendered conducting, when selected by said scanning line, to supply current from said power supply potential to said drive transistor; and

said first and second detection transistors operating, when selected by said scanning line, to detect a threshold voltage of said drive transistor prior to the driving of said load element with the current and supply the detected potential so as to be held into said holding capacitor in order to cancel an influence of the threshold voltage in advance.

5. A display apparatus, comprising:

a plurality of scanning lines extending along rows;

a plurality of signal lines extending along columns; and

a plurality of pixels disposed in a matrix at points at which said scanning lines and said signal lines intersect with each other;

wherein,

each of said pixels including an organic electroluminescence element, a holding capacitor, and five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, a first detection transistor and a second detection transistor;

said holding capacitor being connected between the source and the gate of said drive transistor;

said organic electroluminescence element being connected between the source of said drive transistor and a predetermined cathode potential;

said first detection transistor being connected between the source of said drive transistor and a first ground potential;

said second detection transistor being connected between the gate of said drive transistor and a second ground potential;

said sampling transistor being connected between said gate of said drive transistor and said signal line;

said switching transistor being connected between the drain of said drive transistor and a predetermined power supply potential;

said sampling transistor operating, when selected by said scanning line, to sample an input signal from said signal line and supply the sampled input signal so as to be held into said holding capacitor;

said drive transistor driving said organic electroluminescence element with current in response to the signal potential held by said holding capacitor;

said switching transistor being rendered conducting, when selected by said scanning line, to supply current from said power supply potential to said drive transistor; and

said first and second detection transistors operating, when selected by said scanning line, to detect a threshold voltage of said drive transistor prior to the driving of said organic electroluminescence element with the current and supply the detected potential so as to be held into said holding capacitor in order to cancel an influence of the threshold voltage in advance.

6. A pixel circuit disposed at a point at which a scanning line and a signal line intersect with each other, comprising:

an electro-optical element;

a holding capacitor; and

five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, a first detection transistor and a second detection transistor;

wherein,

said drive transistor being connected at the gate thereof to an input node, at the source thereof to an output node and at the drain thereof to a predetermined power supply voltage;

said electro-optical element being connected between said output node and a predetermined cathode potential;

said holding capacitor being connected between said output node and said input node;

said sampling transistor being connected to said input node and said signal line;

said first detection transistor being connected between said output node and a first ground potential;

said second detection transistor being connected between said input node and a second ground potential;

said switching transistor being interposed between said input node and the gate of said drive transistor;

said sampling transistor operating, when selected by said scanning line, to sample an input signal from said signal line and supply the sampled input signal so as to be held into said holding capacitor;

said switching transistor being rendered conducting, when selected by said scanning line, to connect said holding capacitor to the gate of said drive transistor;

said drive transistor driving said electro-optical element with current in response to the signal potential held by said holding capacitor; and

said first and second detection transistors operating, when selected by said scanning line, to detect a threshold voltage of said drive transistor prior to the driving of said electro-optical element with the current and supply the detected potential so as to be held into said holding capacitor in order to cancel an influence of the threshold voltage in advance.

7. The pixel circuit according to claim 6, wherein said first ground potential is set lower than a level calculated by subtracting the threshold voltage of said drive transistor from said second ground potential, and a level calculated by adding the threshold voltage of said electro-optical element to said cathode potential is set higher than a level calculated by subtracting the threshold voltage of said drive transistor from said first ground potential.

8. The pixel circuit according to claim 7, wherein the level of said second ground potential is set to a value in the proximity of the lowest level of the input signal supplied from said signal line.

9. An active matrix apparatus, comprising:

a plurality of scanning lines extending along rows;

a plurality of signal lines extending along columns; and

a plurality of pixels disposed in a matrix at points at which said scanning lines and said signal lines intersect with each other;

wherein,

each of said pixels including a load element, a holding capacitor, and five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, a first detection transistor and a second detection transistor;

said drive transistor being connected at the gate thereof to an input node, at the source thereof to an output node and at the drain thereof to a predetermined power supply voltage;

said load element being connected between said output node and a predetermined cathode potential;

said holding capacitor being connected between said output node and said input node;

said sampling transistor being connected to said input node and said signal line;

said first detection transistor being connected between said output node and a first ground potential;

said second detection transistor being connected between said input node and a second ground potential;

said switching transistor being interposed between said input node and the gate of said drive transistor;

said sampling transistor operating, when selected by said scanning line, to sample an input signal from said signal line and supply the sampled input signal so as to be held into said holding capacitor;

said switching transistor being rendered conducting, when selected by said scanning line, to connect said holding capacitor to the gate of said drive transistor;

said drive transistor driving said load element with current in response to the signal potential held by said holding capacitor; and

said first and second detection transistors operating, when selected by said scanning line, to detect a threshold voltage of said drive transistor prior to the driving of said load element with the current and supply the detected potential so as to be held into said holding capacitor in order to cancel an influence of the threshold voltage in advance.

10. A display apparatus, comprising:

a plurality of scanning lines extending along rows;

a plurality of signal lines extending along columns; and

a plurality of pixels disposed in a matrix at points at which said scanning lines and said signal lines intersect with each other;

wherein,

each of said pixels including an organic electroluminescence element, a holding capacitor, and five N-channel thin film transistors including a sampling transistor, a drive transistor, a switching transistor, a first detection transistor and a second detection transistor;

said drive transistor being connected at the gate thereof to an input node, at the source thereof to an output node and at the drain thereof to a predetermined power supply voltage;

said organic electroluminescence element being connected between said output node and a predetermined cathode potential;

said holding capacitor being connected between said output node and said input node;

said sampling transistor being connected to said input node and said signal line;

said first detection transistor being connected between said output node and a first ground potential;

said second detection transistor being connected between said input node and a second ground potential;

said switching transistor being interposed between said input node and the gate of said drive transistor;

said sampling transistor operating, when selected by said scanning line, to sample an input signal from said signal line and supply the sampled input signal so as to be held into said holding capacitor;

said switching transistor being rendered conducting, when selected by said scanning line, to connect said holding capacitor to the gate of said drive transistor;

said drive transistor driving said organic electroluminescence element with current in response to the signal potential held by said holding capacitor; and

said first and second detection transistors operating, when selected by said scanning line, to detect a threshold voltage of said drive transistor prior to the driving of said organic electroluminescence element with the current and supply the detected potential so as to be held into said holding capacitor in order to cancel an influence of the threshold voltage in advance.