OLED Pixel Circuit Separating Compensation From Data Writing

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Solution Overview

Problem

Existing organic light-emitting display apparatuses face challenges in maintaining consistent brightness due to variations in the threshold voltage of driving transistors, which affect the current supplied to the display elements.

Innovation Solution

A pixel design that includes specific transistor configurations and capacitors to isolate threshold voltage compensation from data signal writing, ensuring consistent light emission by compensating for threshold voltage variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional pixel design with driving transistor is used, then current is supplied to display element, but brightness consistency deteriorates due to threshold voltage variations

Engineering Contradiction:

Improvebrightness consistencyVSAvoidthreshold voltage variation sensitivity

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The pixel circuit is segmented into multiple functional blocks: initialization transistor (T3), compensation transistor (T4), driving transistor (T1), and emission control transistor (T5). Each transistor handles a specific function separately, allowing independent optimization and compensation for threshold voltage variations without affecting the entire circuit.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The initialization transistor (T3) pre-charges the gate of the driving transistor to a reference voltage before data signal writing. This preliminary action ensures that the driving transistor starts from a known state, compensating for threshold voltage variations before the actual display operation begins.

Inventive Principle:

Principle #10Preliminary action

2Illumination intensity

If threshold voltage compensation is implemented, then brightness consistency is improved, but device complexity increases

Engineering Contradiction:

Improvebrightness consistencyVSAvoidnumber of transistors and wirings

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The compensation transistor (T4) serves multiple functions: it compensates for threshold voltage variations during the compensation period and also acts as a switch for the emission control signal during the emission period. This multi-functionality reduces the total number of transistors needed in the pixel circuit.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The initialization and compensation operations are merged into a unified circuit structure where the initialization transistor (T3) and compensation transistor (T4) work together in sequence. This integration reduces the number of separate components compared to having independent initialization and compensation circuits.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If high-speed display operation is achieved, then productivity is improved, but threshold voltage compensation becomes more difficult

Engineering Contradiction:

Improvedisplay speedVSAvoidcompensation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The pixel circuit operates in distinct periodic phases: initialization period (T3 on), compensation period (T4 on), data writing period, and emission period (T5 on). This periodic operation allows threshold voltage compensation to be completed in a dedicated time window before high-speed display operation begins, ensuring both compensation accuracy and display speed.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The compensation transistor (T4) remains on during the emission period to continuously maintain compensation while the display operates. This continuous action ensures that threshold voltage variations are compensated throughout the entire display operation, not just during a brief compensation phase, enabling high-speed operation without sacrificing compensation effectiveness.

Inventive Principle:

Principle #20Continuity of useful 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 pixel design ensures consistent light emission regardless of threshold voltage fluctuations, improving image quality and reducing the number of transistors and wirings, thereby enhancing display performance at high speeds.

Implementation Method 1

an organic light-emitting diode including an anode connected to the first terminal of the first transistor

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS12369455B2Pixel and display apparatus

Publication Date: 2025.07.22 SAMSUNG DISPLAY CO LTD

AI summary

A pixel that emits light at brightness corresponding to the amount of a driving current regardless of a threshold voltage of a driving transistor, and secure sufficient compensation time by separating an operation of compensating for the threshold voltage of the driving transistor and an operation of writing a data signal, and a display apparatus including the pixel.