Sub-Pixel Threshold Sensing for PAM/PWM Luminance Compensation

Solution Overview

Problem

Existing display devices face challenges in efficiently compensating for luminance differences between sub-pixels due to threshold voltage variations in pulse amplitude modulation (PAM) and pulse width modulation (PWM) circuits, leading to complex sensing structures and prolonged sensing periods.

Innovation Solution

A display device and method that simultaneously senses and compensates for the threshold voltages of both PAM and PWM circuits using a single sensing transistor, reducing the sensing period and simplifying the structure by incorporating a sensing unit that calculates threshold voltage variances and applies data voltages based on prediction information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If separate sensing transistors are used for PAM and PWM circuits, then threshold voltage sensing accuracy is improved, but device complexity and number of transistors increases

Engineering Contradiction:

Improvethreshold voltage sensing accuracyVSAvoidnumber of sensing transistors

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the sensing functions for both PAM and PWM circuits into a single sensing transistor. The sensing transistor is configured to sense the threshold voltage of the PAM circuit during a first sensing period and the threshold voltage of the PWM circuit during a second sensing period, thereby eliminating the need for separate sensing transistors and reducing device complexity while maintaining sensing accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent implements periodic sensing actions by dividing the sensing process into distinct time periods. The sensing transistor operates in a first sensing period to measure the PAM circuit threshold voltage and in a second sensing period to measure the PWM circuit threshold voltage. This temporal separation allows accurate sensing of both circuits using a single transistor without signal interference.

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If sequential sensing of PAM and PWM threshold voltages is performed, then sensing accuracy is maintained, but sensing period length increases

Engineering Contradiction:

Improvethreshold voltage sensing accuracyVSAvoidsensing period length

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent implements periodic sensing actions by dividing the sensing process into distinct time periods. The sensing transistor operates in a first sensing period to measure the PAM circuit threshold voltage and in a second sensing period to measure the PWM circuit threshold voltage. This temporal separation allows accurate sensing of both circuits using a single transistor without signal interference.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent maintains continuous useful action by seamlessly transitioning between sensing operations. After sensing the PAM circuit threshold voltage in the first sensing period, the system immediately proceeds to sense the PWM circuit threshold voltage in the second sensing period without idle intervals. This continuous operation minimizes the total sensing period while ensuring accurate measurement of both circuits.

Inventive Principle:

Principle #20Continuity of useful action

3Manufacturing precision

If multiple sensing transistors are used, then threshold voltage compensation accuracy is improved, but the number of wiring lines and transistors increases

Engineering Contradiction:

Improveluminance uniformityVSAvoidnumber of wiring lines

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the sensing functions for both PAM and PWM circuits into a single sensing transistor. The sensing transistor is configured to sense the threshold voltage of the PAM circuit during a first sensing period and the threshold voltage of the PWM circuit during a second sensing period, thereby eliminating the need for separate sensing transistors and reducing device complexity while maintaining sensing accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12542098B2Display device and luminance difference compensating method of the same

Publication Date: 2026.02.03 LG DISPLAY CO LTD

AI summary

According to an aspect of the present disclosure, a luminance difference compensating method of a display device includes measuring a sensing voltage variance at a node between a first driving transistor and a second driving transistor of a sub pixel; calculating a first threshold voltage variance of the first driving transistor from the sensing voltage variance; calculating a second threshold voltage variance of the second driving transistor from the first threshold voltage variance and a prediction information; compensating for a first data voltage based on the first threshold voltage variance; and compensating for a second data voltage based on the second threshold voltage variance, and the prediction information is a difference value of the first threshold voltage variance and the second threshold voltage variance according to a stress bias and a time.