Scan Driver Circuit Stages for Bidirectional Display Driving

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Solution Overview

Problem

Existing scan drivers for organic light emitting display devices face challenges in efficiently driving multiple scan lines simultaneously and sequentially, particularly in managing clock signals and voltages to ensure proper pixel circuit operation.

Innovation Solution

A scan driver with cascaded circuit stages that include specific transistors and capacitors to manage clock signals and voltages, allowing for simultaneous and sequential driving of scan lines, with features like holding parts, output control parts, and simultaneous driving parts to manage signal levels and directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a scan driver sequentially outputs scan signals to multiple scan lines, then the pixel circuits can be driven in order, but the driving speed and refresh rate are limited by the sequential nature

Engineering Contradiction:

Improvescan signal output speedVSAvoidclock signal management complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The scan driver is divided into multiple circuit stages, each corresponding to a scan line. Each circuit stage includes independent transistors and capacitors that can be controlled separately, allowing the driver to switch between sequential and simultaneous driving modes by activating different stages with appropriate clock signals.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The scan driver employs dynamic control mechanisms where the clock signals (first clock signal and second clock signal) can be adjusted in phase and amplitude to switch between sequential driving mode (for normal operation) and simultaneous driving mode (for fast refresh). The holding part with capacitors maintains signal levels dynamically during mode transitions.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If the scan driver uses multiple clock signals to enable simultaneous and sequential driving, then driving flexibility is improved, but the circuit complexity and power consumption increase

Engineering Contradiction:

Improvedriving mode flexibilityVSAvoidcircuit structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Each circuit stage is designed with universal components that can serve multiple functions. The same transistors and capacitors are used for both sequential and simultaneous driving operations. By controlling the phase relationship between the first and second clock signals, a single circuit structure can achieve different driving modes without requiring separate dedicated circuits for each mode.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The driving mode is controlled by changing the phase difference between the first clock signal and the second clock signal. When the phase difference is 180 degrees, simultaneous driving is achieved. When the phase difference is 0 degrees or other values, sequential driving occurs. This parameter-based control allows flexible mode switching without complex circuit reconfiguration.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the scan driver maintains signal levels using holding parts with capacitors, then signal stability is improved during mode switching, but the device area and power consumption increase

Engineering Contradiction:

Improvesignal level stabilityVSAvoidcircuit area

Core Design Contradiction:

Stability of the object's compositionVSArea of stationary object

Solution Approach 1:

The holding part with capacitors is prepared in advance during the sequential driving period. The capacitors charge to appropriate voltage levels before mode switching occurs. When simultaneous driving is initiated, these pre-charged capacitors immediately maintain the signal levels, preventing instability during the transition. This preliminary preparation eliminates the need for larger stabilization circuits.

Inventive Principle:

Principle #10Preliminary action

4Adaptability or versatility

If the scan driver supports bidirectional driving (forward and reverse directions), then display refresh flexibility is improved, but the control complexity and signal management difficulty increase

Engineering Contradiction:

Improvescan direction controlVSAvoidsignal control ease

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The scan driver can invert the scan direction by changing the phase relationship between clock signals. For reverse direction scanning, the second clock signal is advanced in phase relative to the first clock signal, effectively reversing the activation sequence of the circuit stages. This inversion technique allows bidirectional control without requiring separate dedicated circuits for forward and reverse directions.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11114036B2Scan driver and display device for driving a plurality of scan lines

Publication Date: 2021.09.07 SAMSUNG DISPLAY CO LTD

AI summary

A scan driver includes a plurality of circuit stages, each circuit stage including a first input part configured to transfer a carry signal to a first node in response to a first clock signal, a second input part configured to transfer the first clock signal to a second node in response to a signal of the first node, a first output part configured to transfer a third clock signal to an output terminal in response to a signal of the second node, a holding part configured to maintain a signal of a third node response to a second clock signal, and a second output part configured to transfer a signal of the third node to the output terminal in response to the second clock signal.