Dual-Power Fingerprint Sensing Circuit With Voltage Isolation
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Solution Overview
Problem
Circuits connected to a sensor chip are easily damaged due to increased supply voltage in fingerprint recognition systems, leading to potential breakdowns.
Innovation Solution
A dual-power system with a first and second power system, each providing high and low voltage signals, and detection and transmission circuits to manage voltage differences and prevent damage by isolating the dual-power system from other circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplitude of the radio-frequency signal is increased to detect fingerprints through thicker encapsulation, then the detection capability is improved, but the user experiences discomfort on the finger
Solution Approach 1:
The patent divides the power system into two separate ground voltage systems (first ground voltage GND and second ground voltage NGND) that operate independently. This segmentation allows the sensor chip to have elevated ground potential for improved detection while the ring remains at lower potential for user comfort, resolving the contradiction between detection capability and user comfort.
2Measurement precision
If the second ground voltage NGND is increased to improve fingerprint detection, then the detection sensitivity is improved, but the voltage potential increases causing breakdown of connected circuits
Solution Approach 1:
The patent introduces a potential isolation circuit as an intermediary between the dual-power system and external circuits. This isolation circuit acts as a mediator that allows the sensor chip to operate at elevated ground voltage NGND for improved detection sensitivity while preventing this high voltage from propagating to connected circuits, thus maintaining circuit reliability.
Solution Approach 2:
The patent changes the electrical parameter (ground voltage) of the sensor chip by introducing a second ground voltage NGND that is elevated relative to GND. This parameter change improves detection sensitivity while the isolation circuit ensures that this parameter change does not affect the stability of connected circuits.
3Measurement precision
If the sensor chip operates at elevated voltage for improved detection, then the detection performance is improved, but connected circuits are easily damaged
Solution Approach 1:
The potential isolation circuit serves as a protective intermediary that decouples the elevated voltage operation of the sensor chip from the connected circuits. This intermediary structure allows the sensor chip to maintain elevated ground voltage NGND for improved detection performance while blocking the harmful high voltage from reaching connected circuits, preventing damage.
Data Source
AI summary
Sending, receiving and transmitting apparatuses of a dual-power system and a fingerprint recognition system are provided. The dual-power system includes a first power system for providing a first high voltage signal and a first low voltage signal and a second power system for providing a second high voltage signal and a second low voltage signal, and a voltage difference between the first high voltage signal and the first low voltage signal is equal to that between the second high voltage signal and the second low voltage signal. The sending apparatus includes a first detection circuit for outputting a detection signal indicating whether voltages of the first and second low voltage signals are equal; and a first transmission circuit for transmitting an output signal of the dual-power system or provide a first voltage to an output terminal of the sending apparatus, based on the detection signal.