Pixel Circuit Charge Accumulation for Threshold Voltage Stability

Solution Overview

Problem

Conventional image display devices using organic EL elements face challenges in stably applying a voltage greater than the threshold voltage to driver elements due to variations in threshold voltages of TFTs, leading to operation errors if the initial potential is lower than the threshold voltage.

Innovation Solution

An image display device with a pixel circuit comprising a light-emitting element, a driver element, and a capacitor element, where a charge supply line and a drive control unit ensure that a voltage greater than or equal to the threshold voltage is applied to the driver element by accumulating electrical charge in a capacitor element, allowing stable operation over time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If threshold voltage detection is performed by gradually discharging gate charge, then threshold voltage can be detected, but the process requires applying initial potential that may be lower than threshold voltage causing operation errors

Engineering Contradiction:

Improvethreshold voltage detection accuracyVSAvoidoperation stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by first applying a high initial potential to the gate electrode before threshold voltage detection. This preliminary high potential ensures that the gate-drain potential is always greater than the threshold voltage, preventing operation errors while enabling accurate threshold voltage detection through subsequent gradual discharge of gate charge.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If conventional threshold voltage detection method is used, then threshold voltage can be detected, but the method cannot stably apply voltage greater than threshold voltage to driver element for long time

Engineering Contradiction:

Improvethreshold voltage detection capabilityVSAvoidvoltage application duration

Core Design Contradiction:

Measurement precisionVSDuration of action of stationary object

Solution Approach 1:

The patent applies preliminary action by first applying a high initial potential to the gate electrode before threshold voltage detection. This preliminary high potential ensures that the gate-drain potential is always greater than the threshold voltage, preventing operation errors while enabling accurate threshold voltage detection through subsequent gradual discharge of gate charge.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the voltage parameter by applying a high initial potential (greater than threshold voltage) to the gate electrode, then gradually discharging it. This parameter change enables the system to maintain voltage greater than threshold voltage for long periods, solving the duration problem while still allowing accurate threshold voltage detection.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If initial potential is applied to enable threshold voltage detection, then detection can proceed, but the potential may be lower than threshold voltage causing operation errors

Engineering Contradiction:

Improvethreshold voltage detection processVSAvoidoperation correctness

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies preliminary action by first applying a high initial potential to the gate electrode before threshold voltage detection. This preliminary high potential ensures that the gate-drain potential is always greater than the threshold voltage, preventing operation errors while enabling accurate threshold voltage detection through subsequent gradual discharge of gate charge.

Inventive Principle:

Principle #10Preliminary action

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 enables stable application of a voltage greater than or equal to the threshold voltage to the driver element for a long time, effectively preventing operation errors caused by initial potential mismatches.

Implementation Method 1

the capacitor element accumulating electrical charge for adjusting current flowing in the driver element

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the light-emitting element emitting light when a voltage is applied thereto in a forward direction and accumulating electrical charge when a voltage is applied thereto in a reverse direction

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS8692746B2Image display device for reducing the amount of time required to perform plural, consecutive threshold voltage correction operations

Publication Date: 2014.04.08 LG DISPLAY CO LTD

AI summary

According to one embodiment, an image display device includes a display panel including a pixel circuit, the pixel circuit including a light-emitting element, a driver element, and a capacitor element. The image display device further includes a charge supply line for supplying electrical charge to the light-emitting element of the pixel circuit; and a drive control unit which supplies second electrical charge from the charge supply line to the light-emitting element after first electrical charge accumulated in the light-emitting element is supplied to the capacitor element, further supplies the second electrical charge to the capacitor element and accumulates the first charge and the second charge in the capacitor element, and applies a voltage greater than or equal to the threshold voltage to a control terminal of the driver element, within one frame after the light-emitting element emits light until the light-emitting element emits light next.