Shift Register Control Voltage Generator for LCD Threshold Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal display (LCD) devices face issues with threshold voltage instability in shift registers, leading to abnormal output and increased leakage current due to stress on switching elements and manufacturing errors.
Innovation Solution
A display device with a shift register that includes a control-voltage generator to adjust the control voltage based on current levels, using a clock source and switching elements to stabilize threshold voltage and reduce leakage current, employing a current detector, integrator, and analog-digital converter to select an appropriate control voltage for switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the shift register operates for extended periods, then the switching elements experience increased stress and threshold voltage shifts, but the system continues to function without intervention
Solution Approach 1:
The control voltage is applied to the sub-gate electrode before the switching element experiences significant threshold voltage shifts due to stress. This preliminary action prevents the threshold voltage from drifting away from its optimal value, ensuring stable operation throughout the extended operating period without requiring real-time correction
Solution Approach 2:
The system uses a feedback mechanism where the control voltage generator adjusts the control voltage applied to the sub-gate electrode based on the detected threshold voltage shifts of the switching elements. This closed-loop control continuously compensates for stress-induced threshold voltage changes, maintaining reliability over extended operation
2Reliability
If manufacturing processes have errors, then the threshold voltage of switching elements becomes abnormally high or low, but the shift register should still output normal signals
Solution Approach 1:
The system changes the operating parameters of the switching elements by applying a control voltage to the sub-gate electrode. This control voltage adjusts the effective threshold voltage of the switching elements, compensating for abnormal threshold voltages caused by manufacturing errors and enabling normal signal output despite process variations
3Reliability
If the threshold voltage of switching elements shifts, then leakage current increases and abnormal output occurs, but the system should maintain normal operation
Solution Approach 1:
By applying a control voltage to the sub-gate electrode, the system changes the electrical parameters of the switching element, specifically adjusting its threshold voltage to compensate for stress-induced shifts. This parameter adjustment reduces leakage current and prevents abnormal output, maintaining normal operation throughout the driving period
Data Source
AI summary
There is provided a display device including a display panel including a gate line operated by a gate signal, a clock source configured to apply a clock signal, a shift register including a stage, the stage including at least one switching element and being configured to generate the gate signal based on the clock signal applied from the clock source, and a control-voltage generator configured to generate a control voltage based on a current generated from at least one of the shift register and the clock source and to apply the control voltage to the at least one switching element.