OLED Pixel Circuit With Floating Capacitor for Anode Voltage Coupling

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Voltage coupling between the anode electrode of the light emitting diode and the driving circuit in display devices leads to uniformity deterioration, smear in low grayscale, and image quality deterioration, especially at high temperatures, due to insufficient charging of the anode electrode voltage.

Innovation Solution

A pixel design that minimizes voltage coupling by connecting a capacitor between one electrode of the driving transistor and the driving voltage, compensating the anode electrode voltage through a floating capacitor, and using oxide semiconductor thin film transistors to reduce current leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If voltage coupling (parasitic capacitance) exists between the anode electrode and driving circuit, then the anode electrode voltage cannot be charged sufficiently, but this leads to uniformity deterioration and smear in low grayscale

Engineering Contradiction:

ImproveuniformityVSAvoidvoltage coupling

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and removes the parasitic capacitance (voltage coupling) between the anode electrode and driving circuit by introducing a switching transistor that disconnects the anode from the driving circuit during the emission period, eliminating the harmful voltage coupling effect while maintaining necessary charging during programming period

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies preliminary action by fully charging the anode electrode voltage during the programming period before switching to emission period, ensuring sufficient voltage is stored in the light emitting diode before the harmful voltage coupling can affect uniformity and grayscale performance

Inventive Principle:

Principle #10Preliminary action

2Reliability

If voltage coupling exists between circuit elements, then charging of anode electrode is insufficient, but this causes image quality deterioration especially at high temperature

Engineering Contradiction:

Improveimage qualityVSAvoidvoltage coupling

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the connection between anode electrode and driving circuit switchable - connected during programming period for charging, disconnected during emission period to prevent voltage coupling effects, allowing the system to adapt its configuration based on operational phase

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The switching transistor acts as an intermediary that controls the connection between anode electrode and driving circuit, enabling the system to benefit from voltage coupling during charging while blocking it during emission, thus protecting image quality especially at high temperature

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If a capacitor is connected between driving transistor electrode and driving voltage to compensate anode voltage, then voltage coupling is minimized, but device complexity increases

Engineering Contradiction:

Improvevoltage couplingVSAvoidcircuit structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies multi-functionality by making the switching transistor serve multiple purposes: it acts as both a control element for the light emitting diode and as a means to disconnect/connect the anode electrode to the driving circuit, eliminating the need for separate dedicated capacitors and reducing overall circuit complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Prevents luminance distortion and improves image quality by ensuring quick voltage boosting of the anode electrode, reducing the influence of voltage coupling, and minimizing current leakage.

Implementation Method 1

a capacitor connected between one electrode of the driving transistor and the driving voltage and compensating the voltage of the anode electrode by floating the capacitor while boosting the voltage of the anode electrode of the light emitting diode

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

which can minimize or at least reduce current leakage by using an oxide semiconductor thin film transistor

Methodology Applied

Scientific EffectSemiconductor conduction: Conduction (electrical)

Data Source

PatentUS20260018128A1Pixel, Display Device Including the Pixel and Method for Operating the Display Device

Publication Date: 2026.01.15 LG DISPLAY CO LTD

AI summary

Disclosed is a pixel, including: a light emitting diode; a driving transistor connected between a high potential driving voltage line and a first node and having a gate electrode connected to a second node; a switching transistor connected between a data line and the second node and having a gate electrode that receives a first scan signal; an initialization transistor connected between a reference voltage line and the second node and having a gate electrode that receives a second scan signal; a first capacitor connected between the first node and the second node; a second capacitor having one electrode connected to the first node; a third capacitor connected between the first node and the reference voltage line; and a compensation transistor connected between the third capacitor and the reference voltage line and having a gate electrode that receives a fourth scan signal.