Fingerprint Detection Circuit With Inverse-Phase Amplifier Drive
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Solution Overview
Problem
Capacitive fingerprint identification systems face challenges with small output signals due to low capacitance between metal electrodes and fingers, leading to increased difficulty in identification, and existing solutions that raise voltage amplitudes to address this issue violate conventional voltage requirements for portable devices, increasing circuit complexity and power consumption.
Innovation Solution
A fingerprint detecting circuit with an amplifier that receives two signals with inverse phases, enhancing the output signal strength while meeting conventional voltage requirements for portable devices, by forming capacitances between the amplifier's input and output terminals and using a conductive layer to couple with the finger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage amplitude of the driving signal is raised to increase the output signal strength, then the output signal strength is improved, but the circuit complexity and power consumption increase
Solution Approach 1:
The patent changes the phase parameter of the driving signal by introducing an inverted phase signal (180 degrees out of phase) to the non-inverting input terminal of the amplifier. This parameter change enables signal enhancement without requiring high voltage amplitudes, thus avoiding increased circuit complexity and power consumption while still achieving sufficient output signal strength for fingerprint detection
2Reliability
If the voltage amplitude of the driving signal is raised to increase the output signal strength, then the output signal strength is improved, but the power consumption increases
Solution Approach 1:
The patent utilizes phase parameter change instead of voltage amplitude increase. By applying an inverted phase signal to the non-inverting input terminal, the circuit achieves signal enhancement through constructive interference without the need for high voltage amplitudes, thereby maintaining low power consumption suitable for portable electronic devices
3Reliability
If a high voltage driving signal is used to enhance the output signal, then the output signal strength is improved, but the adaptability to conventional voltage requirements is reduced
Solution Approach 1:
The patent changes from voltage amplitude modulation to phase parameter modulation. By using an inverted phase signal (180 degrees out of phase) at conventional voltage levels (3V or 5V), the circuit achieves signal enhancement while maintaining full compatibility with conventional voltage requirements for portable electronic devices, eliminating the need for special high voltage power supplies
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 enhances the output signal strength, reduces power consumption and production costs, and simplifies the circuit complexity, ensuring compatibility with conventional voltage requirements for portable electronic devices.
Implementation Method 1
the capacitive fingerprint identification system utilizes a metal electrode to couple a touch from a user, and the fingerprint detecting circuit therein may transform a capacitance between the metal electrode and the finger into a voltage signal
Implementation Method 2
a first phase of the first signal is inverse to a second phase of the second signal
Data Source
AI summary
The present invention provides a fingerprint detecting circuit applied in a fingerprint identification system, wherein the fingerprint identification system transmits a first signal to finger. The fingerprint detecting circuit includes a conductive layer to couple a touch from the finger; and an amplifier including a first input terminal coupled to the conductive layer; a second input terminal to receive a second signal; and an output terminal, wherein a first capacitance is between the output terminal and the first input terminal; wherein a phase of the first signal is inverse to a phase of the second signal. The present invention utilizes the two signals with the inverse phases to drive the fingerprint detecting circuit, so as to enhance strength of the output signal and lower hardness of fingerprint detecting. Power consumption and production cost are reduced, and the requirement of conventional voltage for the portable electronic device is satisfied.