Light Sensing Pixel Compensation Circuit for Display Devices
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Solution Overview
Problem
Mobile device screen modules using processes like LTPS, IGZO, and LTPO face non-uniform transistor characteristics, affecting the accuracy of fingerprint recognition and ambient light adjustment functions.
Innovation Solution
A light sensing pixel comprising a transistor, compensation circuit, output circuit, capacitor, and light sensing circuit, where the compensation circuit forms a diode-connected structure with the transistor to detect threshold voltage, and the capacitor generates voltage variations in response to light, compensating for transistor variations and providing stable light sensing results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional processes (LTPS, IGZO, LTPO) are used for screen modules, then manufacturing is feasible and device functionality is achieved, but transistor characteristics become non-uniform across different regions
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before the light sensing operation. The compensation circuit pre-detects and stores the threshold voltage value of the first transistor in a capacitor, so that when light sensing is performed, the stored threshold voltage is already available for compensation calculations, eliminating the need for real-time adjustment during operation.
Solution Approach 2:
The patent implements feedback through the compensation circuit that detects the threshold voltage of the first transistor and uses this information to adjust the light sensing output. The diode-connected transistor structure provides a feedback path that allows the system to sense and compensate for transistor parameter variations, ensuring accurate light sensing despite manufacturing non-uniformities.
2Device complexity
If transistor threshold voltage variations are not compensated, then device complexity is reduced, but light sensing accuracy and fingerprint recognition precision deteriorate
Solution Approach 1:
The patent merges the light sensing function and threshold voltage compensation function into a single integrated pixel structure. The first transistor serves dual purposes: as the light sensing transistor and as part of the compensation circuit (through its diode-connected configuration). This integration allows compensation without adding separate complex circuitry for each function.
Solution Approach 2:
The capacitor acts as an intermediary element that stores the threshold voltage information. By using the capacitor to hold the detected threshold voltage, the system mediates between the compensation circuit and the light sensing operation, allowing the threshold voltage to be transferred and used for compensation without requiring direct continuous interaction between the compensation and sensing circuits.
3Reliability
If compensation circuits are added to detect threshold voltage, then light sensing stability is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by implementing compensation at the individual pixel level rather than requiring global compensation circuits. Each pixel contains its own first transistor and capacitor for threshold voltage storage, allowing localized compensation that addresses transistor variations specific to each region of the display without requiring complex global compensation mechanisms.
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
The solution effectively compensates for transistor characteristic variations, ensuring highly reliable and stable light sensing results, improving the accuracy of fingerprint recognition and ambient light detection in mobile devices.
Implementation Method 1
the light sensing circuit is electrically coupled to the second terminal of the capacitor, wherein in response to the light sensing circuit is illuminated by light, the first terminal of the capacitor and the second terminal of the capacitor generate voltage variations simultaneously
Data Source
AI summary
A light sensing pixel including a first transistor, a compensation circuit, an output circuit, a capacitor and a light sensing circuit is provided. The control terminal of the first transistor is coupled with a first node. The first terminal of the first transistor is configured to receive a first operation voltage or a second operation voltage lower than the first operation voltage. The compensation circuit is configured to detect a threshold voltage of the first transistor, and is configured to form a diode-connected structure with the first transistor. The output circuit is coupled between the second terminal of the first transistor and a sensing line. The capacitor is coupled between the first node and the light sensing circuit. In response to the light sensing circuit is illuminated by light, the first terminal of the capacitor and the second terminal of the capacitor generate voltage variations simultaneously.