# US 10,319,293 B2 · Circuit and method for driving AMOLED pixel

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- Number: US 10,319,293 B2
- Document ID: US10319293B2
- Status: Granted
- Kind: B2
- Application number: 15/328,510
- Filed: 2017-01-10
- Published: 2018-07-12
- Granted: 2019-06-11
- Earliest claimed: 2016-08-31
- Assignees: Shenzhen China Star Optoelectronics Technology Co., Ltd.
- Applicants: Shenzhen China Star Optoelectronics Technology Co., Ltd.
- Inventors: Limin Wang
- Web page: https://patentgrep.com/patent/US10319293B2

## CPC

- G09G 3/3225: using an active matrix
- H03K 17/302: {in field-effect transistor switches}
- G09G 2300/0809: Several active elements per pixel in active matrix panels
- G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor
- 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
- G09G 2310/0262: The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
- G09G 2310/067: Special waveforms for scanning, where no circuit details of the gate driver are given
- G09G 2320/045: Compensation of drifts in the characteristics of light emitting or modulating elements
- H03K 17/6871: {the output circuit comprising more than one controlled field-effect transistor}
- 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)
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

The present disclosure provides a circuit and a method for driving AMOLED pixels, The circuit includes a first transistor; a second transistor; a gray-scale storage capacitor; and a threshold storage capacitor, one end thereof being connected to the other end of the gray-scale storage capacitor, and the other end thereof being connected to a drain of the second transistor for storing a threshold voltage of the second transistor.

## Claims

### Claim 1

A circuit for driving an AMOLED pixel, comprising:
a first transistor, a source thereof being configured to input a gray-scale voltage, and a gate thereof being configured to input a first control signal;
a second transistor, a gate thereof being connected to a drain of the first transistor, and a source thereof being configured to input a drive voltage so as to drive an OLED;
a gray-scale storage capacitor, one end thereof being connected to the drain of the first transistor for storing the gray-scale voltage; and
a threshold storage capacitor, one end thereof being connected to the other end of the gray-scale storage capacitor, and the other end thereof being connected to a drain of the second transistor for storing a threshold voltage of the second transistor,
wherein the threshold voltage of the second transistor is compensated by superposing voltages on two ends of the threshold storage capacitor and the gray-scale storage capacitor;
wherein the circuit further comprises:
a third transistor, arranged between the gray-scale storage capacitor and the threshold storage capacitor, a source thereof being connected to the gray-scale storage capacitor, a drain thereof being connected to the threshold storage capacitor, and a gate thereof being configured to input a second control signal;
a fourth transistor, arranged between the threshold storage capacitor and the drain of the second transistor, a source thereof being connected to the threshold storage capacitor, a drain thereof being connected to the drain of the second transistor, and a gate thereof being configured to input the second control signal;
a fifth transistor, a source thereof being connected to the source of the fourth transistor, a drain thereof being connected to ground, and a gate thereof being configured to input a fourth control signal;
a sixth transistor, a source thereof being configured to input a reference voltage, a drain thereof being connected to the drain of the first transistor, and a gate thereof being configured to input a third control signal;
a seventh transistor, a source thereof being configured to input the reference voltage, a drain thereof being connected to the source of the third transistor, and a gate thereof being configured to input the third control signal;
an eighth transistor, a source thereof being connected to the source of the third transistor, a drain thereof being connected to ground, and a gate thereof being configured to input the first control signal;
wherein a cathode of the OLED is connected to the source of the second transistor, and an anode thereof is configured to input a drive voltage;
wherein a phase of the first control signal is opposite to that of the second control signal, and a phase of the third control signal is opposite to that of the fourth control signal;
wherein the circuit further comprises a phase inverter,
wherein the first control signal and the third control signal are external input signals; and
wherein the second control signal is obtained after phase inversion of the first control signal performed by the phase inverter, and the fourth control signal is obtained after phase inversion of the third control signal performed by the phase inverter.

### Claim 2 (depends on 1)

The circuit according to claim 1, wherein the first control signal, the second control signal, the third control signal, and the fourth control signal are all external input signals to the pixel circuit.

### Claim 3 (depends on 1)

A method for driving an AMOLED pixel by using the circuit according to claim 1,
comprising:
detecting a threshold voltage of the second transistor in each pixel and storing the threshold voltage in a corresponding threshold storage capacitor;
inputting a gray-scale voltage into the first transistor of each pixel, and storing the gray-scale voltage in a corresponding gray-scale storage capacitor; and
superposing voltages on two ends of the threshold storage capacitor and the gray-scale storage capacitor so as to compensate the threshold voltage of the second transistor.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the step of storing the threshold voltage in a corresponding threshold storage capacitor comprises:
setting the first control signal and the fourth control signal in a low-level state, and setting the second control signal and the third control signal in a high-level state, so that in each pixel, the first transistor, the fifth transistor, and the eighth transistor are turned off, while the second transistor, the third transistor, the fourth transistor, the sixth transistor, and the seventh transistor are turned on.

### Claim 5 (depends on 3)

The method according to claim 3, wherein the step of storing the gray-scale voltage in a corresponding gray-scale storage capacitor comprises:
setting the first control signal and the fourth control signal in a high-level state, and setting the second control signal and the third control signal are set in a low-level state, so that in each pixel, the third transistor, the fourth transistor, the sixth transistor, and the seventh transistor are turned off, while the first transistor, the second transistor, the fifth transistor, and the eighth transistor are turned on.

### Claim 6 (depends on 3)

The method according to claim 3, wherein the step of compensating the threshold voltage of the second transistor comprises:
setting the second control signal and the fourth control signal in a high-level state, and setting the first control signal and the third control signal in a low-level state, so that in each pixel, the first transistor, the sixth transistor, the seventh transistor, and the eighth transistor are turned off, while the second transistor, the third transistor, the fourth transistor, and the fifth transistor are turned on.