Pixel Circuit Voltage Current Programming for OLED Tone

Solution Overview

Problem

Existing pixel circuits for current-driven light emitting elements face challenges in accurately and efficiently setting light emission tone, with voltage programming being fast but inaccurate, and current programming being slow.

Innovation Solution

An electrooptical device with a pixel circuit matrix using a combination of voltage and current programming, where a current programming circuit adjusts light emission based on current values, and a data signal generating circuit produces both current and voltage signals to control a holding capacitor, enabling accurate and rapid tone setting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If voltage programming method is used, then programming speed is improved, but light emission tone setting accuracy deteriorates

Engineering Contradiction:

Improveprogramming speedVSAvoidlight emission tone setting accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The programming process is divided into two distinct phases: a voltage programming phase for rapid initial charging of the holding capacitor, and a current programming phase for precise final adjustment. This segmentation allows each phase to optimize for its specific function - speed for voltage programming, accuracy for current programming - thereby resolving the contradiction between programming speed and tone setting accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The voltage programming is performed as a preliminary action before current programming. The holding capacitor is first rapidly charged to a preliminary voltage level corresponding to the desired light emission tone, then fine-tuned using current programming. This preliminary voltage programming establishes a good starting point that reduces the time required for subsequent current programming while maintaining high accuracy.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If current programming method is used, then light emission tone setting accuracy is improved, but programming time increases

Engineering Contradiction:

Improvelight emission tone setting accuracyVSAvoidprogramming time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The programming process is divided into two distinct phases: a voltage programming phase for rapid initial charging of the holding capacitor, and a current programming phase for precise final adjustment. This segmentation allows each phase to optimize for its specific function - speed for voltage programming, accuracy for current programming - thereby resolving the contradiction between programming speed and tone setting accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The voltage programming is performed as a preliminary action before current programming. The holding capacitor is first rapidly charged to a preliminary voltage level corresponding to the desired light emission tone, then fine-tuned using current programming. This preliminary voltage programming establishes a good starting point that reduces the time required for subsequent current programming while maintaining high accuracy.

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

This approach allows for accurate and rapid setting of light emission tone by combining voltage and current programming, improving upon the limitations of conventional methods.

Implementation Method 1

a holding capacitor, connected to a control electrode of the drive transistor, for setting a value of the current that is to flow through the drive transistor by maintaining a charge in accordance with the current value of the current signal

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

Electrooptical devices that use organic EL (electroluminescent) elements have been developed in recent years. Because an organic EL element is a self-emitting element

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7969389B2Pixel circuit for a current-driven light emitting element

Publication Date: 2011.06.28 INTELLECTUAL KEYSTONE TECHNOLOGY LLC

AI summary

Pixel circuit 210 includes a current programming circuit 240 and voltage programming transistors 251 and 252. In order to set the tone of the light emission from the organic EL element 220, the first and second voltage programming transistors 251 and 252 are set to the OFF and ON state, respectively, and voltage programming is carried out using a voltage signal Vout. Next, the states of the first and second voltage programming transistors 251 and 252 are switched, and current programming is carried out using a current signal Iout.