Gate Driver Circuit All-Selecting Drive Voltage Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing liquid crystal display devices face reliability issues during all-selecting drive due to voltage exceeding the withstand voltage of thin film transistors, leading to potential dielectric breakdown and reduced display quality.
Innovation Solution
The implementation of a scanning signal line drive circuit with independent first and second-potential power supply wirings and stage constituent circuits that include output control nodes and turn-off switching elements, allowing for controlled potential changes without increasing circuit elements, thereby preventing excessive voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all-selecting drive is performed to discharge residual electric charges from pixel capacitances, then display quality is improved by preventing afterimages and flicker, but voltage exceeds the withstand voltage of thin film transistors causing dielectric breakdown and reliability degradation
Solution Approach 1:
A new potential supply wiring (first-potential power supply wiring) is introduced as an intermediary element specifically for the scanning signal line drive circuit. This separate wiring supplies a controlled potential that prevents excessive voltage application to thin film transistors during all-selecting drive, while still enabling the discharge of residual electric charges from pixel capacitances. The intermediary wiring acts as a buffer between the power supply and the scanning signal lines, ensuring voltage remains within safe limits.
Solution Approach 2:
The power supply system is segmented into two independent parts: a first-potential power supply wiring dedicated to the scanning signal line drive circuit, and a second-potential power supply wiring for other circuits. This segmentation allows independent control of potential levels, enabling the scanning signal lines to operate at a potential that prevents dielectric breakdown while still achieving the all-selecting drive function for discharging pixel capacitances.
2Reliability
If independent first-potential power supply wiring is provided for scanning signal line drive circuit, then voltage reliability is maintained during all-selecting drive, but device complexity increases due to additional power supply wiring
Solution Approach 1:
The first-potential power supply wiring, while independent, is designed to serve multiple functions: it supplies potential during normal scanning operations and provides controlled potential during all-selecting drive to prevent dielectric breakdown. This multi-functionality reduces the need for additional specialized circuits, thereby limiting the increase in device complexity despite the addition of independent wiring.
3Reliability
If stage constituent circuits include output control nodes and turn-off switching elements, then excessive voltage is prevented without increasing circuit elements, but circuit design complexity increases
Solution Approach 1:
The stage constituent circuits incorporate output control nodes and turn-off switching elements that dynamically adjust the potential applied to scanning signal lines based on operational requirements. During all-selecting drive, these elements actively control the potential to prevent excessive voltage, while during normal operation they enable standard scanning functions. This dynamic control achieves reliability improvement without requiring additional static circuit elements.
Data Source
AI summary
The purpose of the present invention is to achieve a display device capable of performing an all-selecting drive for gate bus lines without increasing the number of circuit elements more than heretofore and without lowering withstand voltage reliability. In a stage constituent circuit, which constitutes a shift register in a gate driver, an all-selecting signal (ALL-ON) for simultaneously turning all of gate bus lines to a selected state is given, as a low-potential power supply, to a source terminal of a thin film transistor (Tr4) for setting, at a low level, a QB node provided for setting a scanning signal (OUT) at the low level and to a source terminal of a thin film transistor (Tr3) for setting, at the low level, a Q node provided for setting the scanning signal (OUT) at a high level. A wiring (ALL-ON wiring) for supplying a low-potential power supply to the gate driver and a wiring (VSS wiring) for supplying the low-potential power supply to a circuit other than the gate driver are power supply wirings independent of each other.