Fingerprint Sensor Transistor Circuit for High-Resolution Displays
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Solution Overview
Problem
Existing display devices face challenges in maintaining the sensitivity of fingerprint sensors while achieving high-resolution displays due to parasitic capacitance affecting touch signals from overlapping touch and data lines.
Innovation Solution
The display device incorporates a fingerprint sensor with multiple light receiving elements and sensor transistors configured to operate in alternating sensing frames, using silicon-based and oxide-based semiconductors to manage touch signals effectively, and includes a read-out line system to integrate fingerprint sensing with high-resolution display functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light receiving elements are used to maintain fingerprint sensor sensitivity, then the sensitivity is improved, but the device complexity increases
Solution Approach 1:
The fingerprint sensor is divided into multiple light receiving elements (first and second light receiving elements) that can operate independently. Each light receiving element has its own dedicated sensor transistor (fourth transistor for first light receiving element, fifth transistor for second light receiving element), allowing parallel processing of fingerprint data without requiring a single complex sensor circuit.
Solution Approach 2:
The patent implements dynamic switching between different light receiving elements using control signals. The fourth and fifth sensor transistors are selectively activated based on sensing frame requirements, enabling the system to switch between capturing fingerprint data from different light receiving elements. This dynamic operation allows the sensor to adapt to different sensing conditions while maintaining high sensitivity.
2Object-affected harmful factors
If alternating sensing frames are used to manage touch signals, then parasitic capacitance interference is reduced, but the sensing time increases
Solution Approach 1:
The patent implements periodic sensing frames that alternate between different light receiving elements. The first light receiving element is used during odd sensing frames while the second light receiving element is used during even sensing frames. This periodic switching pattern allows the system to complete sensing operations within each frame while minimizing interference from parasitic capacitance through the alternating sequence.
Solution Approach 2:
The reset transistor is activated during the reset period of each sensing frame to discharge the sensor node to a reference voltage before the light receiving element captures fingerprint data. This preliminary reset action ensures that any residual charge from previous operations is cleared, preventing interference from parasitic capacitance before the actual sensing begins.
3Measurement precision
If multiple sensor transistors are used to control sensing current, then the measurement precision is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent employs different transistor types with specialized characteristics for different functions. The first sensor transistor uses oxide-based semiconductor for high-impedance sensing current control, while the second sensor transistor uses silicon-based semiconductor for low-impedance reset operations. This local specialization allows each transistor to be optimized for its specific function, improving overall precision while managing manufacturing complexity through targeted material selection.
Solution Approach 2:
The patent combines oxide-based semiconductor and silicon-based semiconductor transistors within the same sensor circuit. The oxide-based semiconductor transistor provides high input impedance for accurate sensing current measurement, while the silicon-based semiconductor transistor provides low output impedance for efficient reset operations. This composite approach leverages the complementary properties of different semiconductor materials to achieve high precision while managing the trade-off with manufacturing complexity.
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 configuration maintains the sensitivity of fingerprint sensors in high-resolution display products by minimizing interference from parasitic capacitance, ensuring accurate touch signal detection.
Implementation Method 1
first and second light receiving elements receiving light
Data Source
AI summary
Provided are a fingerprint sensor and a display device including the same. A fingerprint sensor includes a read-out line extending in a first direction, first and second light receiving elements receiving light, a first sensor transistor configured to control a sensing current based on a voltage of a sensor node, a second sensor transistor configured to discharge the sensor node to a first initialization voltage in response to a reset signal, a third sensor transistor electrically connecting a first electrode of the first sensor transistor to the read-out line in response to a gate signal, a fourth sensor transistor electrically connecting the sensor node to the first light receiving element in response to a first control signal, and a fifth sensor transistor 10 electrically connecting the sensor node to the second light receiving element in response to a second control signal.