Scanning Line Driving Circuit Floating State Pulse Control

Solution Overview

Problem

Existing single-channel scanning line driving circuits for liquid crystal displays face challenges in causing scanning lines to be in a floating state, leading to decreased driving capability and contrast due to delayed rise and fall of output pulses, which shortens the on-time of pixel TFTs and reduces the voltage applied to liquid crystals.

Innovation Solution

A scanning line driving circuit is designed with a configuration of transistors of identical conductivity type, where a first transistor has its source connected to a power supply and drain to a scanning line, and a second transistor has its source connected to the scanning line and drain to a clock signal line, allowing both transistors to be in an off-state simultaneously, thereby improving the rise and fall times of output pulses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If switching TFTs are arranged on a scanning line to cause scanning lines to be in a floating state, then the scanning line can be separated, but the driving capability decreases and the rise or fall of output pulse is delayed

Engineering Contradiction:

Improvefloating state capabilityVSAvoidrise and fall time of output pulse

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The invention extracts the switching function from the scanning line path by using a separate switching circuit connected to the gate of the first transistor. This removes the switching TFTs that were previously arranged directly on the scanning line, eliminating their on-resistance from the signal path while preserving the floating state capability through the separate switching mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces an intermediate switching mechanism where a second transistor and control circuit act as mediators to achieve the floating state. Instead of directly switching the scanning line, the control circuit mediates by controlling the gate voltage of the first transistor, thereby achieving line separation without degrading pulse characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If switching TFTs are arranged on a scanning line, then the scanning line can be separated, but the on-resistance increases and contrast decreases

Engineering Contradiction:

Improvefloating state capabilityVSAvoidcontrast degradation

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The invention extracts the switching function from the scanning line path by using a separate switching circuit connected to the gate of the first transistor. This removes the switching TFTs that were previously arranged directly on the scanning line, eliminating their on-resistance from the signal path while preserving the floating state capability through the separate switching mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If a single-channel circuit configuration is used to reduce manufacturing costs, then the number of manufacturing processes decreases, but the capability to cause scanning lines to be in a floating state is not disclosed

Engineering Contradiction:

Improvemanufacturing process reductionVSAvoidfloating state capability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The invention segments the driving circuit into distinct functional blocks: a first transistor for driving the scanning line, a second transistor for controlling the floating state, and a control circuit for coordinating their operation. This segmentation enables the single-channel circuit to achieve floating state capability while maintaining manufacturing simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces an intermediate switching mechanism where a second transistor and control circuit act as mediators to achieve the floating state. Instead of directly switching the scanning line, the control circuit mediates by controlling the gate voltage of the first transistor, thereby achieving line separation without degrading pulse characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8884865B2Scanning line driving circuit, display device, and scanning line driving method

Publication Date: 2014.11.11 NEC LCD TECH CORP

AI summary

A scanning line driving circuit includes a first transistor having a source electrode connected to a power supply and a drain electrode to a scanning line and a second transistor having a source electrode connected to the scanning line and a drain electrode connected to a clock signal line. The conductivity type of the second transistor is identical to that of the first transistor. A bias can be supplied, so that the first and second transistors are caused to be in an off-state simultaneously.