Scan Signal Driver for Stable Blank-Period Pixel Sensing
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Solution Overview
Problem
In organic light-emitting display devices, maintaining a stable gate-on voltage at connection nodes of thin-film transistors during a blank period is challenging, leading to depletion mode operation and impaired pixel sensing and external compensation performance.
Innovation Solution
A scan signal driver with a simplified circuit structure, including a sensing control unit, maintains a stable gate-on voltage by separating the pull-up node with thin-film transistors, using a sensing control circuit and output node control circuit to manage voltage levels during active and blank periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If thin-film transistors are used in scan signal output stages, then device area is reduced and integration is improved, but gate-on voltage cannot be maintained during blank period causing depletion mode operation
Solution Approach 1:
The sensing control circuit pre-charges the sensing control node to gate-on voltage level during the active period before the blank period begins. This preliminary voltage preparation ensures that when the blank period starts, the node already has the required voltage level, allowing the thin-film transistor to remain in enhancement mode and continue operating reliably without voltage collapse.
Solution Approach 2:
The sensing control node acts as an intermediary between the gate-on voltage source and the pull-up node of the scan signal output stage. It mediates the voltage transmission by being pre-charged to gate-on level and then maintaining this level during the blank period, enabling the pull-up transistor to function properly as an active pull-up device rather than entering depletion mode.
2Use of energy by moving object
If gate-on voltage level decreases during blank period, then power consumption is reduced, but scan signal output fails and sensing operation is impaired
Solution Approach 1:
The output node control circuit pre-charges the output node to gate-on voltage level during the active period before the blank period begins. This ensures that when the blank period starts, the output node already has sufficient voltage to maintain the scan signal output stage in enhancement mode, preventing voltage collapse while still allowing reduced power consumption compared to continuous high-voltage operation.
3Device complexity
If thin-film transistors operate in depletion mode, then circuit simplicity is maintained, but external compensation performance deteriorates
Solution Approach 1:
The sensing control circuit pre-charges the sensing control node to gate-on voltage level during the active period, ensuring that during the blank period when sensing occurs, the node maintains sufficient voltage to keep the thin-film transistor in enhancement mode. This preliminary voltage preparation enables both the simplified depletion-mode circuit structure and high-precision sensing operation to coexist.
Solution Approach 2:
The invention changes the voltage parameter of the sensing control node dynamically - maintaining it at gate-on level during the active period for pre-charging, and keeping it at gate-on level during the blank period for accurate sensing. This parameter control ensures the thin-film transistor operates in enhancement mode during sensing, achieving both circuit simplicity and measurement precision.
Data Source
AI summary
A scan signal driver includes: stages to sequentially output scan signals in an active period, and to selectively output sensing signals in a vertical blank period. At least one of the stages includes: a sensing control circuit to supply a gate-on voltage to a sensing control node in response to a holding control signal during the active period, and to output the gate-on voltage of the sensing control node in response to a selectively input line select signal during the vertical blank period; an output node control circuit to supply the gate-on voltage to a pull-up node when the gate-on voltage of the sensing control node is output during the vertical blank period; and an output circuit to output a scan clock signal as a sensing signal to one of scan signal lines when the gate-on voltage is supplied to the pull-up node during the vertical blank period.