OLED Data Driver Feedback Loop for Brightness Uniformity

Solution Overview

Problem

Conventional organic light emitting diode (OLED) display devices struggle to achieve desired brightness due to variations in transistor threshold voltages and the inability to measure and control current accurately at each pixel.

Innovation Solution

A data driver with a shift register, latch, current digital-analog converter, and comparator is used to generate sampling signals, store data, convert data current, compare it with pixel current, and control data voltage to equalize the current, ensuring consistent brightness across pixels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional transistors are used in each pixel without current measurement and control, then the device complexity is low, but the brightness uniformity deteriorates due to transistor threshold voltage variations

Engineering Contradiction:

Improvebrightness uniformityVSAvoiddevice complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements a feedback mechanism where the data driver measures the actual current flowing through each pixel's transistor and uses this measurement to adjust the data voltage. The measured current is fed back to the data driver, which then modifies the data voltage to compensate for transistor threshold voltage variations, ensuring uniform brightness across all pixels.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces manual or mechanical current adjustment methods with an automated electrical measurement and control system. The data driver electronically measures pixel current and automatically adjusts data voltage based on the measurement, eliminating the need for manual calibration or mechanical adjustment mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If no current measurement and control method is implemented, then the ease of operation is high, but the brightness control precision deteriorates

Engineering Contradiction:

Improvecurrent measurement precisionVSAvoidease of operation

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent enables the data driver to automatically measure and control pixel current without external intervention. The system self-regulates by measuring the actual current through each pixel and autonomously adjusting the data voltage to achieve the desired brightness, eliminating the need for external calibration or manual adjustment.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent implements a feedback mechanism where the data driver measures the actual current flowing through each pixel's transistor and uses this measurement to adjust the data voltage. The measured current is fed back to the data driver, which then modifies the data voltage to compensate for transistor threshold voltage variations, ensuring uniform brightness across all pixels.

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If transistor threshold voltage variations are not compensated, then the productivity is high, but the image quality deteriorates due to non-uniform brightness

Engineering Contradiction:

Improvebrightness uniformityVSAvoidproductivity

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent implements a feedback mechanism where the data driver measures the actual current flowing through each pixel's transistor and uses this measurement to adjust the data voltage. The measured current is fed back to the data driver, which then modifies the data voltage to compensate for transistor threshold voltage variations, ensuring uniform brightness across all pixels.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8125421B2Data driver and organic light emitting display device including the same

Publication Date: 2012.02.28 SAMSUNG DISPLAY CO LTD

AI summary

A data driver and an organic light emitting display device including the data driver. The data driver including a shift register part to generate sampling signals in sequence, a latch part to store external data in response to the sampling signals, a current digital-analog converter to generate a data current corresponding to the data stored in the latch part, and a comparator producing a current corresponding to the difference between a pixel current and the data current. The comparator compares the pixel current fed back from each pixel with the data current, controls the data voltage by increasing or decreasing the current output, and supplies the controlled data voltage to the pixel. By controlling the data voltage an image is displayed with desired brightness regardless of non-uniformity of transistors in each pixel.