OLED Pixel Compensation Circuit with Reverse Bias Sub-circuit

Solution Overview

Problem

The existing pixel compensation circuits in OLED displays face limitations in brightness uniformity due to the drift of threshold voltage, which restricts the available compensation range, leading to incomplete compensation and display abnormalities.

Innovation Solution

A pixel compensation circuit is designed with a reverse bias sub-circuit that maintains the light emitting element in a reverse bias state using a specific bias voltage, independent of the light-on voltage, allowing for a larger compensation range of the threshold voltage by controlling the first control signal across the light emitting element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a conventional pixel compensation circuit is used, then the circuit structure is simple, but the compensation range of threshold voltage is limited and brightness uniformity deteriorates

Engineering Contradiction:

Improvebrightness uniformityVSAvoidcircuit structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The pixel circuit is divided into distinct functional modules: a reverse bias control module that independently manages the reverse bias voltage application to the light emitting element, and a compensation control module that handles threshold voltage compensation. This segmentation allows the reverse bias function to operate independently, expanding the compensation range without overwhelming circuit complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reverse bias voltage is applied to the light emitting element before the compensation operation begins. This preliminary action prepares the OLED in a known state, enabling more effective threshold voltage compensation and extending the usable compensation range by preventing incomplete compensation scenarios.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If the light emitting element is not maintained in reverse bias state, then the circuit operation is simple, but the compensation range is limited and display abnormalities occur

Engineering Contradiction:

Improvecompensation rangeVSAvoidcontrol signal

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

A reverse bias control module acts as an intermediary between the control signal line and the light emitting element. This module receives control signals and conditionally applies reverse bias voltage based on the operational phase, enabling expanded compensation range while managing control signal complexity through modular design.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The reverse bias voltage application is made dynamic rather than static. The control module adjusts whether to apply reverse bias voltage based on the current operational phase (e.g., compensation phase vs. display phase), allowing the circuit to adapt its behavior to maximize compensation range while maintaining simple operation during normal display.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If the compensation range is limited, then the circuit design is simple, but incomplete compensation occurs and display uniformity deteriorates

Engineering Contradiction:

Improvedisplay uniformityVSAvoidreverse bias sub-circuit

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The pixel circuit is divided into distinct functional modules: a reverse bias control module that independently manages the reverse bias voltage application to the light emitting element, and a compensation control module that handles threshold voltage compensation. This segmentation allows the reverse bias function to operate independently, expanding the compensation range without overwhelming circuit complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reverse bias voltage is applied to the light emitting element before the compensation operation begins. This preliminary action prepares the OLED in a known state, enabling more effective threshold voltage compensation and extending the usable compensation range by preventing incomplete compensation scenarios.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11217181B2Pixel compensation circuit, method for driving the same, and display apparatus

Publication Date: 2022.01.04 BOE TECHNOLOGY GROUP CO LTD

AI summary

The present application provides a pixel compensation circuit, a method for driving the same, and a display apparatus. The pixel compensation circuit includes a light emitting element, a current control sub-circuit and a reverse bias sub-circuit. The current control sub-circuit is coupled to a first terminal of the light emitting element and is configured to control current flowing between a first terminal and a second terminal of the light emitting element. The reverse bias sub-circuit is coupled to a first control signal line and a second terminal of the light emitting element respectively. The reverse bias sub-circuit is configured to set the second terminal of the light emitting element to be at a first bias voltage under the control of a signal on the first control signal line, so that the light emitting element is maintained in a reverse bias state.