Shift Register Node Charging for Post-Power-Off TFT Threshold Sensing
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Solution Overview
Problem
Display devices, particularly OLEDs, face degradation issues affecting display quality due to transistor characteristics and organic light-emitting device degradation, which existing technologies fail to effectively address by sensing the threshold voltage of driving transistors after the device is powered off.
Innovation Solution
A method and display device that perform sensing for compensation by charging and discharging nodes in shift registers connected to gate lines during a black frame, allowing for the sensing of subpixels connected to these lines, thereby reducing tact time and improving image quality by determining the threshold voltage of driving TFTs after the device is powered off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensing is performed during normal operation, then display quality degradation can be compensated, but sensing time increases and affects productivity
Solution Approach 1:
The patent performs sensing operations during a black frame period before normal display operation begins. By charging nodes M and Q in advance during the black frame, and completing threshold voltage sensing before the display panel starts normal operation, the system achieves compensation for display quality degradation without extending the actual sensing time into the productive display period. This preliminary action during non-display time resolves the contradiction between maintaining display quality and preserving productivity.
2Speed
If multiple shift registers are charged simultaneously, then sensing speed improves, but device complexity increases
Solution Approach 1:
The patent divides the gate driver into multiple independent shift registers (first shift register A and second shift register B), each connected to different gate lines (jth and Kth). This segmentation allows parallel charging of nodes M in different shift registers during the black frame, thereby improving sensing speed. The independence of each shift register module simplifies the control logic compared to a single complex shift register, as each can be controlled separately through dedicated control signals (LSP A signal and LSP B signal).
Solution Approach 2:
The patent merges the sensing operations of multiple gate lines by performing threshold voltage sensing for subpixels connected to different gate lines (jth and Kth) during the same black frame period. By combining multiple sensing operations into a single time window and using parallel node charging, the system achieves high-speed sensing without proportionally increasing device complexity, as the control signals are generated through integrated control logic.
3Loss of time
If sensing is performed after power off, then sensing time is reduced, but measurement precision may be affected
Solution Approach 1:
The patent performs threshold voltage sensing during a black frame period, which occurs before the display device is fully powered off. By completing the sensing operation during this intermediate state and before normal operation begins, the system achieves fast sensing without waiting for complete power shutdown. The preliminary charging of nodes and completion of sensing measurements during the black frame ensures both time efficiency and measurement accuracy, as the device is still in a stable operational state rather than a fully powered-off state.
Data Source
AI summary
A display device and a compensation method of the display device are discussed. A sensing method for compensation, which is performed after a display device is powered off, includes displaying 1 black frame, charging a node M of a shift register A connected to a jth gate line of a display panel, charging a node M of a shift register B connected to a Kth gate line of the display panel, and sensing subpixels connected to the jth gate line and then sensing subpixels connected to the Kth gate line.