# US 2014/0191669 A1 · Driving circuit and method for pixel unit, pixel unit and display apparatus

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- Number: US 2014/0191669 A1
- Document ID: US20140191669A1
- Status: Published application
- Kind: A1
- Application number: 13/805,728
- Filed: 2012-11-01
- Published: 2014-07-10
- Earliest claimed: 2011-12-01
- Assignees: Chengdu Boe Optoelectronics Technology Co., Ltd.; Boe Technology Group Co., Ltd.
- Applicants: Chengdu Boe Optoelectronics Technology Co. Ltd.; Boe Technology Group Co., Ltd.
- Inventors: Wen Tan; Xiaojing Qi; Like Hu; Young Yik Ko
- Web page: https://patentgrep.com/patent/US20140191669A1

## CPC

- G09G 3/3225: using an active matrix
- G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element
- G09G 2300/0417: Special arrangements specific to the use of low carrier mobility technology
- G09G 2300/0819: used for counteracting undesired variations, e.g. feedback or autozeroing
- G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor
- 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
- G09G 2320/0233: Improving the luminance or brightness uniformity across the screen
- G09G 2320/045: Compensation of drifts in the characteristics of light emitting or modulating elements
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

The present invention provides a driving circuit and method for a pixel unit, a pixel unit and a display apparatus. The driving circuit for a pixel unit comprises: a driving thin-film transistor, a first switching element, a storage capacitor and a driving control unit; said driving control unit is used to control said storage capacitor to be charged/discharged so as to control said driving thin-film transistor to operate in a saturation region, so that the threshold voltage Vth of said driving thin-film transistor is compensated by utilizing the gate-source voltage of said driving thin-film transistor. The present invention can address the problems of ununiformity and attenuation of the brightness of OLED panel.

## Claims

### Claim 1

A driving circuit for a pixel unit, for driving an OLED, wherein, the driving circuit for the pixel unit comprises: a driving thin-film transistor, a first switching element, a storage capacitor and a driving control unit;
wherein, a first end of said storage capacitor is connected to a gate of said driving thin-film transistor, and a second end of said storage capacitor is connected to a high level output of a driving power supply;
a source of said driving thin-film transistor is connected to a data line via said first switching element;
a drain of said driving thin-film transistor is connected to an anode of said OLED and a low level output of the driving power supply respectively via said driving control unit, a source of said driving thin-film transistor is connected to said high level output of the driving power supply, and a gate of said driving thin-film transistor is connected to the drain of said driving thin-film transistor;
said driving control unit, for controlling said storage capacitor to be charged and/or discharged to control said driving thin-film transistor to operate in a saturation region, so as to compensate a threshold voltage Vth of said driving thin-film transistor by a gate-source voltage of said driving thin-film transistor.

### Claim 2 (depends on 1)

The driving circuit for the pixel unit of claim 1, wherein, said driving thin-film transistor is a p-type thin-film transistor.

### Claim 3 (depends on 2)

The driving circuit for the pixel unit of claim 2, wherein,
said first switching element is a p-type thin-film transistor;
a gate of said first switching element is connected to a scan line for transmitting a control signal, a source of said first switching element is connected to the data line, and a drain of said first switching element is connected to the source of said driving thin-film transistor.

### Claim 4 (depends on 3)

The driving circuit for the pixel unit of claim 3, wherein, said driving control unit comprises: a second switching element, a third switching element, a fourth switching element and a fifth switching element;
said second switching element is connected between the drain of said driving thin-film transistor and said low level output of the driving power supply;
said third switching element is connected between the gate of said driving thin-film transistor and the drain of said driving thin-film transistor;
said fourth switching element is connected between the drain of said driving thin-film transistor and the anode of said OLED; and
said fifth switching element is connected between the source of said driving thin-film transistor and said high level output of the driving power supply.

### Claim 5 (depends on 4)

The driving circuit for the pixel unit of claim 4, wherein, said second switching element, said third switching element, said fourth switching element and said fifth switching element are p-type TFTs;
a gate of said second switching element is connected to a first control line, a source of said second switching element is connected to the drain of said driving thin-film transistor, and a drain of said second switching element is connected to said low level output of the driving power supply;
a gate of said third switching element is connected to said scan line, a source of said third switching element is connected to the gate of said driving thin-film transistor, and a drain of said third switching element is connected to the drain of said driving thin-film transistor;
a gate of said fourth switching element is connected to a second control line, a source of said fourth switching element is connected to the drain of said driving thin-film transistor, and a drain of said fourth switching element is connected to the anode of said OLED; and
a gate of said fifth switching element is connected to said second control line, a source of said fifth switching element is connected to said high level output of the driving power supply, and a drain of said fifth switching element is connected to the source of said driving thin-film transistor.

### Claim 6 (depends on 1)

A method for driving a pixel unit, being applied to the driving circuit for the pixel unit of claim 1, wherein, said method for driving a pixel unit comprising the steps of:
pixel charging: by a driving control unit controlling a storage capacitor to be charged;
pixel discharging: by the driving control unit controlling said storage capacitor to be discharged via the driving thin-film transistor, until a gate-source voltage of said driving thin-film transistor is equal to the threshold voltage Vth of said driving thin-film transistor;
switch buffering: by the driving control unit controlling the gate voltage of the driving thin-film transistor to remain stable;
driving the OLED to emit light and display: by said driving control unit controlling said driving thin-film transistor to operate in a saturation region, and controlling the voltage difference between two ends of said storage capacitor to remain unchanged, so as to compensate the threshold voltage Vth of said driving thin-film transistor by the gate-source voltage of said driving thin-film transistor, and to drive OLED to emit light by said driving thin-film transistor.

### Claim 7 (depends on 6)

The method for driving the pixel unit according to claim 6, wherein,
the step for pixel charging comprises: by a first switch element switching on a connection between the source of said driving thin-film transistor and a data line; by said driving control unit switching on a connection between the drain of said driving thin-film transistor and a cathode of said OLED, switching on a connection between the gate of said driving thin-film transistor and the drain of said driving thin-film transistor, switching off the connection between the source of said driving thin-film transistor and said high level output of the driving power supply, and controlling said storage capacitor to be charged;
the step for pixel discharging comprises: by said driving control unit switching off the connection between the drain of said driving thin-film transistor and the cathode of said OLED, by said driving control unit controlling said storage capacitor to be discharged via said driving thin-film transistor, until a gate-source voltage of said driving thin-film transistor is equal to the threshold voltage Vth of said driving thin-film transistor;
the step for switch buffering comprises: by said first switching element switching off the connection between the source of said driving thin-film transistor and the data line; by said driving control unit switching off the connection between the gate of said driving thin-film transistor and the drain of said driving thin-film transistor;
the step for driving OLED to emit light and display comprises: by the driving control unit switching on a connection between the source of said driving thin-film transistor and said high level output of the driving power supply, switching on a connection between the drain of said driving thin-film transistor and the anode of said OLED, controlling said driving thin-film transistor to operate in the saturation region, and controlling the voltage difference between two ends of said storage capacitor to remain unchanged, so as to compensate the threshold voltage Vth of said driving thin-film transistor by the gate-source voltage of said driving thin-film transistor, and to drive OLED to emit light by said driving thin-film transistor.

### Claim 8 (depends on 1)

A pixel unit comprising an OLED and the driving circuit for the pixel unit of claim 1, wherein, the driving circuit for the pixel unit is connected to an anode of OLED, and a cathode of OLED is connected to the low level output of the driving power supply.

### Claim 9

(canceled)