LDO and Buck Converter Power Supply for Display Sensing Noise

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Solution Overview

Problem

Organic light emitting display devices face degradation of circuit elements over time, leading to characteristic value changes that can decrease sensing accuracy due to noise generated during pixel characteristic value sensing.

Innovation Solution

A display device incorporating a low drop-out (LDO) regulator and a buck converter, where the LDO regulator provides a second power voltage during a sensing period and the buck converter provides a first power voltage during a display period, both connected through switches controlled by a timing controller to minimize noise and maintain accurate voltage levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single power source is used for both sensing and display periods, then device complexity is reduced, but noise in the sensing process increases due to power supply fluctuations

Engineering Contradiction:

Improvesensing accuracyVSAvoidpower supply configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The power supply system is segmented into two independent sources: a first power source connected to the buck converter for display period power supply, and a second power source connected to the LDO regulator for sensing period power supply. This segmentation isolates the sensing circuit from noise generated during display operations, thereby improving sensing accuracy without requiring complex switching mechanisms.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A power line acts as an intermediary connecting both power sources to the pixel circuit. The timing controller selectively activates appropriate power sources through switching elements (first and second switches) based on the operational period, mediating between the two power sources and the load to ensure noise-free sensing while maintaining display functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the LDO regulator is used during display period, then power supply stability is improved, but power consumption increases due to higher current requirements

Engineering Contradiction:

Improvepower supply stabilityVSAvoidpower consumption

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The power supply configuration is made dynamic by selectively switching between the buck converter and LDO regulator based on the operational period. During the display period, the buck converter provides power with lower consumption, while during the sensing period, the LDO regulator provides stable power. The timing controller dynamically selects the appropriate source, optimizing the trade-off between stability and power consumption for each phase.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system employs periodic action by alternating between different power sources according to the frame period. The buck converter operates during display periods when high current is needed, while the LDO regulator operates during sensing periods when stability is critical. This periodic switching allows the system to achieve both low power consumption and high stability at different times in the cycle.

Inventive Principle:

Principle #19Periodic action

3Loss of energy

If switching elements are always on, then device complexity is reduced, but power loss increases due to continuous current flow

Engineering Contradiction:

Improvepower lossVSAvoidswitching control mechanism

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The timing controller performs preliminary action by pre-determining which power source and switching elements should be active based on the current operational period. Before each sensing or display phase begins, the controller has already configured the appropriate power source connection, ensuring that switching elements are activated only when needed and minimizing unnecessary current flow and power loss throughout the frame period.

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 configuration stabilizes the power supply to pixels, reducing noise and enhancing the accuracy of characteristic value sensing and compensation, thereby improving the overall performance and longevity of the display device.

Implementation Method 1

a low drop-out ('LDO') regulator which provides a second power voltage to a power line during a first period of one frame

Methodology Applied

Scientific EffectLow drop-out regulation:

Implementation Method 2

a buck converter which provides a first power voltage to the power line during a third period of the one frame

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11488534B2Display device and driving method of the same

Publication Date: 2022.11.01 SAMSUNG DISPLAY CO LTD

AI summary

A display device includes: a low drop-out (“LDO”) regulator which provides a second power voltage to a power line during a first period of one frame; a buck converter which provides a first power voltage to the power line during a third period of the one frame; and a pixel connected to the LDO regulator and the buck converter through the power line. A voltage level of the second power voltage is equal to a voltage level of the first power voltage.