Capacitance Circuit Dynamic Gain Control for Fingerprint Detection Signal Clipping
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Solution Overview
Problem
Existing fingerprint detection systems face signal clipping issues due to increased capacitance when multiple drive electrodes are selected, leading to reduced detection accuracy.
Innovation Solution
A detecting device with a first electrode selection circuit that alternates between selecting all and some electrodes, using a capacitance circuit with adjustable capacitance values to control gain, preventing signal clipping and maintaining detection accuracy across different electrode selection periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of simultaneously selected drive electrodes is increased, then the capacitance formed between drive electrodes and detection electrodes increases, but detection signals may be clipped
Solution Approach 1:
The patent applies dynamics by making the capacitance value of the capacitance circuit changeable according to the number of simultaneously selected drive electrodes. The capacitance circuit dynamically adjusts its capacitance value to match the varying total capacitance from multiple drive electrodes, preventing signal clipping while maintaining detection accuracy throughout the detection process.
Solution Approach 2:
The patent implements parameter changes by varying the capacitance value of the capacitance circuit based on the number of selected drive electrodes. This parameter adjustment ensures that the gain remains appropriate regardless of whether one or multiple drive electrodes are selected, thereby preventing signal clipping and maintaining optimal detection performance.
2Reliability
If the gain is designed to match with a state where the number of simultaneously selected drive electrodes is relatively large, then signal clipping is suppressed, but detection signals become small when the number of simultaneously selected drive electrodes is relatively small, reducing detection accuracy
Solution Approach 1:
The patent resolves this contradiction by making the capacitance circuit's capacitance value dynamic rather than fixed. The capacitance value is adjusted in real-time according to the number of simultaneously selected drive electrodes, allowing the system to suppress signal clipping when many electrodes are selected while maintaining high detection accuracy when fewer electrodes are selected.
Solution Approach 2:
The patent changes the capacitance parameter of the capacitance circuit based on the detection conditions. By varying this parameter to match the number of selected drive electrodes, the system achieves both signal clipping suppression and high detection accuracy across different operating states without requiring separate gain designs for different scenarios.
3Measurement precision
If code division multiplexing drive is used to obtain signals from small electrodes, then detection sensitivity is improved, but capacitance variation causes signal clipping
Solution Approach 1:
The patent maintains the benefits of code division multiplexing drive for detecting signals from small electrodes while resolving the signal clipping issue by making the capacitance circuit dynamic. The capacitance value adjusts according to the number of simultaneously selected drive electrodes during code division multiplexing, ensuring both high detection sensitivity and signal stability without clipping.
Solution Approach 2:
The patent applies parameter changes to the capacitance circuit to accommodate the variable capacitance conditions created by code division multiplexing drive. By adjusting the capacitance value to match the number of selected drive electrodes, the system maintains both the detection sensitivity advantage of code division multiplexing and the signal stability needed to prevent clipping.
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 suppresses signal clipping and enhances fingerprint detection accuracy by dynamically adjusting capacitance values based on the number of selected electrodes, ensuring consistent signal quality.
Implementation Method 1
a capacitance circuit capable of changing capacitance for each of the second electrodes, and the capacitance of the capacitance circuit is controlled to have different values between the first period and the second period
Data Source
AI summary
A detecting device includes a plurality of first electrodes extending in a first direction and a plurality of second electrodes extending in a second direction intersecting the first direction, the first electrodes and the second electrodes being disposed facing each other with an insulating layer interposed therebetween, a first electrode selection circuit configured to supply a drive signal to the first electrodes, and a detection circuit configured to detect capacitance generated between the first electrodes and the second electrodes due to the drive signal.