Method for driving a pixel circuit with feedback compensation, a circuit for driving a light-emitting device, and a display apparatus

Patent metadata

Field	Value
Publication number	US-11295666-B2
Application number	US-201816476976-A
Country	US
Kind code	B2
Filing date	Aug 16, 2018
Priority date	Aug 16, 2018
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

The present application discloses a method for driving a pixel circuit. The method includes initializing a voltage setting in a pixel circuit including at least a driving transistor coupled to a light-emitting device and obtaining a first threshold voltage of the driving transistor. The method further includes inputting a first data voltage to the pixel circuit to generate a first driving current independent of the first threshold voltage, to drive light emission of the light-emitting device in a current cycle. Additionally, the method includes generating a compensation voltage via a feedback sub-circuit based on a change of the first driving current upon a second threshold voltage of the light-emitting device. Furthermore, the method includes inputting a second data voltage combined with the compensation voltage as a negative feedback to generate a second driving current to drive light emission of the light-emitting device in a next cycle.

First claim

What is claimed is:

1. A method for driving a pixel circuit with feedback compensation in consecutive cycles comprising:
initializing a voltage setting in the pixel circuit including at least a driving transistor coupled to a light-emitting device;
obtaining a first threshold voltage of the driving transistor;
inputting a first data voltage from a data voltage terminal to the pixel circuit to generate a first driving current independent of the first threshold voltage, to drive light emission of the light-emitting device in a current cycle;
generating a compensation voltage via a feedback sub-circuit coupled between the data voltage terminal and the light-emitting device based on a change of the first driving current due to a change of a second threshold voltage of the light-emitting device; and
inputting a second data voltage from the data voltage terminal combined with the compensation voltage as a negative feedback to generate a second driving current to drive light emission of the light-emitting device for displaying a pixel image in a next cycle;
wherein each of the current cycle and the next cycle is one of two consecutive durations for the light-emitting device to emit light for producing two consecutive frames of pixel images under a progressive scanning scheme, each duration comprising consecutively a first period, a second period, a third period, and a fourth period;
wherein the initializing the pixel circuit comprises releasing charges in a source electrode of the driving transistor in the first period of the current cycle, the source electrode being coupled to an anode of the light-emitting device;
wherein the obtaining the first threshold voltage of the driving transistor comprises setting a voltage level at a first electrode of a first capacitor in the pixel circuit to a first reference voltage in the second period of the current cycle and storing the first threshold voltage as a voltage difference between the first electrode and a second electrode of the first capacitor, wherein the first electrode of the first capacitor is coupled to a gate electrode of the driving transistor; and
wherein the inputting the first data voltage comprises transferring the first data voltage to the second electrode of the first capacitor in the third period of the current cycle and resetting the voltage level at the first electrode of the first capacitor to a sum of the first data voltage and the first threshold voltage.

2. The method of claim 1 , wherein the resetting the voltage level at the first electrode of the first capacitor comprises making the voltage level at the source electrode of the driving transistor to at least a second threshold voltage in the fourth period of the current cycle and generating the first driving current through the driving transistor.

3. A method for driving a pixel circuit with feedback compensation in consecutive cycles comprising:
initializing a voltage setting in the pixel circuit including at least a driving transistor coupled to a light-emitting device;
obtaining a first threshold voltage of the driving transistor;
inputting a first data voltage from a data voltage terminal to the pixel circuit to generate a first driving current independent of the first threshold voltage, to drive light emission of the light-emitting device in a current cycle;
generating a compensation voltage via a feedback sub-circuit coupled between the data voltage terminal and the light-emitting device based on a change of the first driving current due to a change of a second threshold voltage of the light-emitting device; and
inputting a second data voltage from the data voltage terminal combined with the compensation voltage as a negative feedback to generate a second driving current to drive light emission of the light-emitting device for displaying a pixel image in a next cycle;
wherein each of the current cycle and the next cycle is one of two consecutive durations for the light-emitting device to emit light for producing two consecutive frames of pixel images under a progressive scanning scheme, each duration comprising consecutively a first period, a second period, a third period, and a fourth period;
wherein the generating the compensation voltage comprises:
using a first resistor to obtain a first sampling voltage equal to the first driving current multiplying a resistance of the first resistor in the fourth period of the current cycle;
inputting the first sampling voltage to a first positive input terminal of a first voltage-difference comparator in the feedback sub-circuit; and
coupling the first data voltage to a first negative input terminal of the first voltage-difference comparator to output a first voltage difference between the first sampling voltage and the first data voltage.

4. The method of claim 3 , further comprising inputting the first voltage difference to a second negative input terminal of a second voltage-difference comparator in the feedback sub-circuit;
coupling a second reference voltage to a second positive input terminal of the second voltage-difference comparator; and
outputting a second voltage difference between the second reference voltage and the first voltage difference; wherein the second voltage difference is proportional to the change of the first driving current due to the change of the second threshold voltage of the light-emitting device.

5. The method of claim 4 , further comprising coupling the second voltage difference as the compensation voltage to the data voltage terminal to be added with the second data voltage.

6. The method of claim 5 , wherein the compensation voltage is zero when the second threshold voltage remains substantially unchanged, the compensation voltage is a negative value to compensate an increasing driving current when the second threshold voltage decreases, and the compensation voltage is a positive value to compensate a decreasing driving current when the second threshold voltage increases.

7. A circuit for driving a light emitting device in a series of cycles of displaying frames of pixel images comprising:
a driving transistor having a gate coupled to a first node, a source coupled to a second node connected to an anode of the light emitting device, and a drain connected to a first voltage terminal;
an initialization sub-circuit coupled to a second voltage terminal and the first node and configured to initialize potentials at the first node and the second node under control of a first control signal from a first control terminal;
a data-input and compensation sub-circuit coupled to the second voltage terminal, a data voltage terminal, the first node, and the second node and configured to receive a data voltage and change potentials at the first node and the second node under control of the first control signal and a second control signal from a second control terminal;
a feedback sub-circuit coupled to a cathode of the light emitting device and the data voltage terminal, being configured to receive the data voltage and compensate a threshold voltage difference of the light-emitting device;
wherein the feedback sub-circuit comprises:
a first voltage-difference comparator having a first positive input port coupled to the cathode of the light-emitting device connected to a first constant voltage terminal via a first resistor, a first negative input port and a first output port;
a second voltage-difference comparator having a second negative input port coupled to the first output port, a second positive input port coupled to a second constant voltage terminal via a second resistor, and a second output port being coupled to the second positive input port via a third resistor; and
a third capacitor having one terminal coupled to the data voltage terminal and the other one terminal cou

Assignees

• Hefei Boe Optoelectronics Tech
• Boe Technology Group Co Ltd

Inventors

• Jiang Ran
• Kang Hai
• Wang Donghui
• Yan Chengchen
• Ma Shengfei

Classifications

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G2320/0295

  by monitoring each display pixel · CPC title

• G09G2320/045

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

• G09G2300/0819

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

• G09G2310/08

  Details of timing specific for flat panels, other than clock recovery · CPC title