Pixel Reading Device for OLED Fingerprint Sensing Common Mode Compensation
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Solution Overview
Problem
Existing OLED display panels with embedded fingerprint sensing pixel arrays face challenges in reading the output voltage due to the negative pressure range of the sensing voltage, which complicates the compensation and reading of the common mode component.
Innovation Solution
A pixel reading device and method utilizing a first capacitor, a second capacitor, a voltage generating circuit, and an analog front-end (AFE) circuit to receive and compensate the sensing voltage, pulling up the compensation voltage from an initial level to a compensation level during the level reading period to offset the common mode component, allowing the AFE circuit to operate within a positive voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensing voltage is read directly from the fingerprint sensing pixel, then the reading process is simple, but the AFE circuit cannot operate properly due to negative voltage range
Solution Approach 1:
The patent introduces a capacitor as an intermediary element between the fingerprint sensing pixel and the AFE circuit. The capacitor couples the sensing voltage while blocking the DC component, enabling the AFE circuit to operate with AC-coupled signals and eliminating the negative voltage issue without complicating the reading process
2Device complexity
If the common mode component is not compensated, then the circuit operation is simple, but the sensing accuracy deteriorates due to saturation and distortion
Solution Approach 1:
The patent applies preliminary action by compensating for the common mode component before the AFE circuit processes the sensing signal. The compensation is performed in advance during the sensing period, preventing saturation and distortion before they occur, thereby maintaining both circuit simplicity and sensing accuracy
3Device complexity
If the compensation voltage is not pulled up during level reading, then the circuit operation is simple, but the common mode component cannot be compensated effectively
Solution Approach 1:
The patent implements periodic action by pulling up the compensation voltage only during the level reading period, while maintaining it at initial level during the sensing period. This time-dependent periodic adjustment enables effective common mode compensation during reading without continuously complicating the circuit operation
Data Source
AI summary
A pixel reading device, which includes a first capacitor, a second capacitor, a voltage generating circuit, and an analog front-end (AFE) circuit, is provided. A first terminal of the first capacitor is coupled to a fingerprint sensing pixel to receive a sensing voltage. A first terminal of the second capacitor is coupled to a second terminal of the first capacitor. The voltage generating circuit provide a compensation voltage to a second terminal of the second capacitor. During a sensing period of the fingerprint sensing pixel, the compensation voltage is at an initial level. During a level reading period of the fingerprint sensing pixel, the compensation voltage is pulled up from the initial level to a compensation level to compensate a common mode component of the sensing voltage. An input terminal of the AFE circuit is coupled to the second terminal of the first capacitor.