Display Driver Circuit Segmentation for Threshold and Mobility Compensation

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Solution Overview

Problem

Conventional pixel circuits for organic EL displays face issues with inefficient data voltage utilization, inaccurate threshold value correction, increased circuit scale, reduced aperture ratio, and difficulty in inspecting electric current flow, leading to challenges in maintaining desired luminance and high-definition display performance.

Innovation Solution

A display device with pixel circuits that include a control terminal connected to the data line through a switching element, allowing for precise voltage adjustments based on threshold voltage corrections, and utilizing a scanning signal output circuit to control the write-target pixel circuit for efficient data voltage application, thereby reducing the need for complex capacitance and increasing the aperture ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a voltage program scheme is used to compensate TFT variations, then circuit design becomes easier and parasitic capacity influence is reduced, but the ability to compensate mobility variations is limited

Engineering Contradiction:

Improvecircuit design easeVSAvoidcompensation capability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The compensation function is segmented into two independent circuits: a first compensation circuit that compensates for threshold voltage variations using voltage signals, and a second compensation circuit that compensates for mobility variations using current signals. This segmentation allows each circuit to specialize in one type of compensation, achieving both ease of design and comprehensive compensation capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent merges the voltage program scheme and electric current program scheme into a single pixel circuit by combining a first compensation circuit (voltage-based) and a second compensation circuit (current-based). This fusion allows the circuit to compensate for both threshold voltage and mobility variations simultaneously, resolving the limitation of using only one compensation scheme.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If an electric current program scheme is used to compensate TFT variations, then mobility variations can be compensated, but circuit scale increases and parasitic capacity influence increases

Engineering Contradiction:

Improvecompensation capabilityVSAvoidcircuit scale

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary current signal generation mechanism in the second compensation circuit that converts voltage signals to current signals through a controlled process. This intermediary mechanism enables mobility compensation without requiring direct complex current signal input, thereby controlling circuit scale and parasitic capacity effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If conventional pixel circuits are used with coupling capacitance, then threshold value correction can be performed, but data voltage utilization becomes inefficient and circuit scale increases

Engineering Contradiction:

Improvethreshold value correction accuracyVSAvoidcircuit scale

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the threshold voltage detection function from the conventional coupling capacitance-based circuit and implements it through a dedicated first compensation circuit that uses voltage signals. This extraction eliminates the need for large coupling capacitance while maintaining accurate threshold voltage correction, thereby reducing circuit scale and improving data voltage utilization efficiency.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the fundamental parameter used for threshold voltage correction from capacitance-based voltage division to direct voltage signal-based correction. By using voltage signals in the first compensation circuit, the system achieves accurate threshold voltage correction without relying on large coupling capacitance, thus improving data voltage utilization and reducing circuit scale.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8847939B2Method of driving and a driver for a display device including an electric current driving element

Publication Date: 2014.09.30 SHARP KK

AI summary

An electric current driving display device includes pixel circuits, a scanning signal output circuit and a display signal output circuit. The pixel circuits include intersecting scanning lines and data lines. Each pixel circuit includes an electro-optical element and a drive element having a control terminal connected to the data line through a switching element. The scanning signal output circuit selects a write-target pixel circuit using the scanning line, and controls the selected pixel circuit outputs, to the data line, a voltage which depends on a threshold voltage of the drive element. The display signal output circuit applies, to the data line, a voltage obtained by adding or subtracting a correction voltage corresponding to the threshold voltage to or from a data voltage corresponding to display data, based on the voltage outputted to the data line.