Fingerprint Sensing Circuit with Dual-Voltage Array State Control
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Solution Overview
Problem
Existing fingerprint recognition systems face challenges in accurately distinguishing fingerprint ridges and valleys due to variations in capacitance values caused by uneven finger textures, leading to reduced recognition accuracy and sensitivity.
Innovation Solution
A fingerprint recognition circuit with a loop selection unit and signal processing unit that employs two driving voltages and a sequence signal to control the fingerprint recognition units in different working states, enhancing signal processing and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single driving voltage is used for the sensing electrode, then the circuit structure is simple, but the recognition accuracy and sensitivity are reduced due to variations in capacitance values caused by uneven finger textures
Solution Approach 1:
The patent applies dynamics by making the driving voltage adjustable rather than fixed. The loop selection unit dynamically switches between different driving voltages (first driving voltage and second driving voltage) based on the working state, allowing the system to adapt to varying capacitance conditions caused by uneven finger textures, thereby improving recognition accuracy without permanently increasing circuit complexity.
Solution Approach 2:
The patent changes the electrical parameter (driving voltage level) to optimize performance. By using two different driving voltages and selectively applying them through the loop selection unit, the system can adjust the voltage parameter to match different working states, compensating for capacitance variations and enhancing signal quality for more accurate fingerprint recognition.
2Reliability
If the fingerprint recognition units are operated in a uniform state, then the control is simple, but the signal processing quality is reduced due to noise interference and environmental factors
Solution Approach 1:
The patent implements periodic action by alternating between different working states (first working state and second working state) through sequence signals. This periodic switching allows the system to perform multiple operations including signal acquisition, resetting, and noise filtering in a cyclic manner, improving signal processing quality by averaging out random noise while maintaining manageable control through automated sequencing.
Solution Approach 2:
The system uses sequence signals to control the loop selection unit based on the current working state, creating a feedback mechanism. The state of the fingerprint recognition units feeds back to determine which driving voltage should be applied next, allowing the system to automatically adjust and optimize signal processing quality without requiring complex manual control.
3Stability of the object's composition
If the circuit does not have a reset state, then the operation is continuous and simple, but the consistency of voltage levels across the array deteriorates due to parasitic capacitances and environmental factors
Solution Approach 1:
The patent applies preliminary action by incorporating a reset state that prepares the circuit before normal operation. The loop selection unit selectively connects the sensing electrode to the first driving voltage during the reset phase, preemptively clearing parasitic capacitances and establishing consistent voltage levels across all sensing electrodes before signal acquisition begins, ensuring stability without significantly impacting overall operation time.
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
Improves fingerprint recognition accuracy and sensitivity by minimizing the impact of parasitic capacitances and environmental factors, ensuring consistent voltage levels across the array.
Implementation Method 1
when a finger with uneven texture contacts the surface of the fingerprint recognition sensor, finger capacitances of different sizes are formed. The finger capacitance is connected in series to the dielectric layer capacitance.
Data Source
AI summary
The present disclosure provides a method for controlling a fingerprint identification circuit. The method is used for detecting fingerprint recognition units arranged in an array. A fingerprint recognition unit is connected to a fingerprint recognition circuit. The fingerprint recognition circuit includes a loop selection unit and a signal processing unit. The method includes: resetting the fingerprint recognition circuit to enable the loop selection unit to load a first driving voltage to a sensing electrode; and, controlling a state of the loop selection unit through a sequence signal control to enable the fingerprint recognition units arranged in an array to be in different working states.