OLED Pixel Circuit Timing for Flicker-Free Low-Frequency Modes

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Solution Overview

Problem

Existing pixel circuits in OLED displays experience screen flicker and instability in low frequency modes due to inconsistent brightness waveforms and potential differences in electrode potentials, particularly in Always On Display (AOD) applications, which affect power consumption and display quality.

Innovation Solution

A pixel circuit design with a drive sub-circuit, writing sub-circuit, and reset sub-circuit, where the frequency of the first scan signal line matches the data refresh frequency, and the second scan signal line operates at a higher frequency to stabilize anode terminal charging, ensuring consistent brightness and reducing flicker, while using Low Temperature Polycrystalline Oxide (LTPO) technology to minimize leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the pixel circuit operates in low frequency display mode to reduce power consumption, then power efficiency is improved, but screen flicker and brightness instability occur

Engineering Contradiction:

Improvepower consumptionVSAvoidbrightness stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The pixel circuit is divided into multiple functional sub-circuits: drive sub-circuit for current control, writing sub-circuit for data voltage application, and reset sub-circuit for anode terminal initialization. This segmentation allows each sub-circuit to operate independently with optimized timing, enabling stable brightness at low refresh rates by coordinating their operations to maintain consistent electrode potentials throughout the display period

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic frequency operation where the first scan signal line operates at data refresh frequency while the second scan signal line operates at a higher frequency. This dynamic timing adjustment allows the reset sub-circuit to frequently stabilize the anode terminal potential even during low frequency display mode, eliminating flicker while maintaining low power consumption

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If the first scan signal line frequency is reduced to match data refresh frequency for low frequency mode, then power consumption decreases, but brightness waveform consistency deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidbrightness waveform consistency

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent employs dynamic frequency differentiation where the first scan signal line operates at data refresh frequency (lower frequency for power saving) while the second scan signal line operates at a higher frequency. This allows the reset sub-circuit to maintain frequent anode terminal stabilization independent of the data refresh rate, ensuring brightness waveform consistency even during low frequency display mode

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The reset sub-circuit performs preliminary action by frequently resetting the anode terminal potential before data writing occurs. This preliminary stabilization ensures that the electrode potential is consistent and ready for accurate data voltage application, maintaining brightness waveform consistency regardless of the lower data refresh frequency

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the second scan signal line operates at higher frequency to stabilize anode terminal charging, then brightness stability improves, but device complexity increases

Engineering Contradiction:

Improvebrightness stabilityVSAvoidsignal line frequency control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second scan signal line serves multiple functions: it controls the reset sub-circuit for anode terminal stabilization and also serves as a timing reference for coordinating the writing sub-circuit operations. This multi-functionality reduces the need for additional separate control lines, managing device complexity while achieving brightness stability through frequent anode terminal charging

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250209986A1Pixel circuit and drive method therefor, and display apparatus

Publication Date: 2025.06.26 BOE TECHNOLOGY GROUP CO LTD

AI summary

Disclosed are a pixel circuit and a drive method therefor, and a display apparatus. The pixel circuit includes a drive sub-circuit, a writing sub-circuit, a first reset sub-circuit, and a light emitting element, wherein the drive sub-circuit is configured to provide a drive current between a first electrode and a second electrode of the drive sub-circuit in response to a control signal of a first node; the writing sub-circuit is configured to write a data voltage signal to the first electrode of the drive sub-circuit in response to a control signal of a first scan signal line; the first reset sub-circuit is configured to reset an anode terminal of the light emitting element in response to a control signal of a second scan signal line.