Sensor Scan Driver Transmission Gates for Stable Photodiode Signals
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Solution Overview
Problem
The existing sensor scan drivers for flat panel displays with built-in touch screens suffer from unstable signal supply to photodiodes due to leakage current, leading to increased power consumption and erroneous operations, which affects the optical characteristics and manufacturing costs of the displays.
Innovation Solution
A sensor scan driver is designed with a transmission gate unit that stabilizes the voltage range of sensor scan signals, including a shift register unit for generating signals, a transmission gate unit for voltage range adjustment, and a buffer unit for stable signal supply to photodiodes, using a first and second transmission gate with specific polarity control electrodes and voltage settings to minimize leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a common level shifter is employed to shift voltage levels of sensor scan signals, then the voltage range can be changed, but leakage current is generated during transitory phases when transistors are simultaneously turned on, causing increased power consumption and unstable output signals
Solution Approach 1:
The patent introduces a transmission gate unit as an intermediary component between the shift register and the photodiodes. This transmission gate unit includes transmission gates with control signals that prevent simultaneous turn-on of transistors, thereby eliminating the direct harmful interaction that causes leakage current while still achieving the required voltage level shifting function
Solution Approach 2:
The patent converts the potential harm of transistor switching by using complementary control signals (inverted phases) to ensure that when one transistor is on, the other is off. This approach transforms the switching mechanism from a source of leakage current into a controlled signal transmission mechanism that improves overall system reliability
2Shape
If photodiodes are formed in non-pixel regions between pixels to create a built-in touch screen, then the optical characteristics and thickness can be improved, but leakage current in the sensor scan driver causes erroneous operations and unstable signal supply
Solution Approach 1:
The transmission gate unit serves as an intermediary that isolates the shift register from the photodiodes while maintaining signal transmission. By introducing this intermediate stage with controlled transistor switching, the patent prevents leakage current from affecting the photodiodes, thereby maintaining operational stability in the integrated structure
3Adaptability or versatility
If transistors are used in the level shifter to change voltage levels, then the voltage range can be adjusted, but during transitory phases the transistors are simultaneously turned on creating a path between power sources that generates leakage current
Solution Approach 1:
The patent employs dynamic control of transistor switching through complementary control signals. The transmission gates are controlled by inverted clock signals that ensure transistors are never simultaneously on, dynamically adjusting the voltage levels while preventing the creation of direct power source paths that would cause leakage current
Solution Approach 2:
The patent changes the control parameter timing by using inverted phase control signals for complementary transistors. This parameter change in the control signal timing ensures that voltage level adjustment is achieved while preventing the simultaneous conduction state that causes energy loss through leakage current
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures stable driving signals are supplied to photodiodes, improving the optical sensitivity and overall performance of the built-in touch screen, reducing power consumption, and enhancing the display's optical characteristics while minimizing manufacturing costs.
Implementation Method 1
a transmission gate unit adapted to change a voltage range of sensor scan signals supplied from a shift register to output a voltage range
Implementation Method 2
photo sensors realized by photodiodes are formed in non-pixel regions between the pixels of the display panel so that a change in optical current generated by a touch event from the user is sensed
Data Source
AI summary
A sensor scan driver may include a shift register unit for driving photodiodes, a transmission gate unit for changing a voltage range of sensor scan signals generated by the shift register unit, and a buffer unit for supplying the sensor scan signals supplied from the transmission gate unit to the photodiodes, wherein the transmission gate unit includes first and second transmission gates, each including an electrode adapted to receive an output signal of the shift register unit, another electrode adapted to receive the inverted output signal of the shift register unit, an input terminal coupled to first and second power sources, respectively, and an output terminal coupled to an output terminal of the transmission gate unit.