OLED Pixel Circuit Compensation for Display Uniformity

Solution Overview

Problem

OLED display panels face brightness non-uniformity and chromaticity issues due to differences in light emitting diode efficiencies, primarily caused by variations in the voltage at which the diodes start to emit light, leading to inconsistent display performance.

Innovation Solution

A pixel circuit comprising a storage capacitor, light emitting diode, data writing circuit, compensation circuit, driving transistor, and light emitting control circuit, where the compensation circuit writes a compensation voltage (sum of lighting voltage and power supply voltage) into a node, and the light emitting control circuit drives the diode under a light emitting control signal, isolating the diode's luminance from the lighting voltage, thus eliminating its influence on display uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional OLED display panels are used, then the display can achieve self-luminescence and high contrast, but brightness non-uniformity and chromaticity issues occur due to variations in light emitting diode efficiencies and voltage thresholds

Engineering Contradiction:

Improvedisplay uniformityVSAvoidpixel circuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The compensation circuit performs preliminary action by pre-calculating and storing compensation values in the storage capacitor before the actual light emission occurs. This compensation voltage is prepared in advance based on the lighting voltage level, so that when the light emitting diode is driven, the compensation is already in place to correct for voltage threshold variations, ensuring uniform brightness without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The storage capacitor acts as an intermediary element between the compensation circuit and the light emitting diode. It stores the compensation voltage and provides it to the driving transistor, effectively mediating the correction process. This intermediary approach allows the compensation to be decoupled from the actual light emission timing, enabling more flexible and reliable display uniformity control.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the light emitting diode is driven directly without compensation, then the circuit structure remains simple, but the lighting voltage directly affects luminance causing non-uniform display

Engineering Contradiction:

Improvepixel circuit structureVSAvoidbrightness consistency

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The compensation circuit performs preliminary action by pre-calculating and storing compensation values in the storage capacitor before the actual light emission occurs. This compensation voltage is prepared in advance based on the lighting voltage level, so that when the light emitting diode is driven, the compensation is already in place to correct for voltage threshold variations, ensuring uniform brightness without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The storage capacitor acts as an intermediary element between the compensation circuit and the light emitting diode. It stores the compensation voltage and provides it to the driving transistor, effectively mediating the correction process. This intermediary approach allows the compensation to be decoupled from the actual light emission timing, enabling more flexible and reliable display uniformity control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enhances display uniformity by ensuring that the light emitting diode's luminance is only associated with the data voltage, not the lighting voltage, thereby improving the display's brightness and color consistency.

Implementation Method 1

a light emitting diode, a data writing circuit, a compensation circuit, a driving transistor and a light emitting control circuit; a first electrode of the light emitting diode is electrically coupled to a third node, and a second electrode of the light emitting diode is electrically coupled to a second power supply terminal

Methodology Applied

Scientific EffectLight emitting diode: Light Emitting Diode

Data Source

PatentUS11501713B2Pixel circuit, driving method thereof and display device

Publication Date: 2022.11.15 BEIJING BOE TECH DEV CO LTD

AI summary

The disclosure provides a pixel circuit and a driving method thereof, a display device. The pixel circuit includes: a storage capacitor having a first terminal coupled to a first node and a second terminal coupled to a second node; a light emitting diode having a first electrode coupled to a third node and a second electrode coupled to a second power supply terminal; a data writing circuit configured to write a data voltage into the second node; a compensation circuit configured to write a voltage of the third node, as a compensation voltage, into the first node; a driving transistor having a control terminal coupled to the first node, a first electrode coupled to a first power supply terminal and a second electrode coupled to the light emitting control circuit; a light emitting control circuit configured to control the light emitting diode to emit light.