Fingerprint Sensing Circuit Using Floating Power and Ground Signals
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Solution Overview
Problem
The high production cost of fingerprint identification systems is due to the need for high-voltage semiconductor processes to generate high-voltage square wave signals, which are costly to produce.
Innovation Solution
A fingerprint identification system using a low-voltage process to generate high-voltage signals through a signal generation circuit with an amplitude reduction circuit, level shifter circuits, and switch modules, producing floating power and ground signals with amplitudes greater than the breakdown voltage, thereby enhancing the fingerprint signal intensity without the need for high-voltage semiconductor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-voltage semiconductor process is used to generate high-voltage square wave signals, then the fingerprint signal intensity is enhanced, but the production cost increases
Solution Approach 1:
The patent changes the voltage parameter by using a low-voltage process (e.g., 1.8V or 3.3V) to generate high-voltage signals (e.g., 5V or higher) through circuit transformation. The signal generation circuit includes voltage conversion functionality that transforms low-voltage input signals into high-voltage output signals, thereby achieving high signal intensity without requiring expensive high-voltage semiconductor processes
Solution Approach 2:
The patent introduces an intermediary signal generation circuit that acts as a mediator between the low-voltage process and the high-voltage signal requirement. This circuit includes components such as operational amplifiers, voltage multipliers, or charge pumps that convert low-voltage signals into high-voltage square wave signals, eliminating the need for direct high-voltage semiconductor manufacturing
2Ease of manufacture
If a low-voltage process is used to manufacture the system, then the production cost is reduced, but the ability to generate high-voltage signals is compromised
Solution Approach 1:
The patent implements dynamic voltage conversion where the signal generation circuit dynamically transforms low-voltage signals into high-voltage square wave signals based on the fingerprint sensing requirements. The circuit can switch between different voltage levels and configurations to maintain reliable high-voltage signal generation while using only low-voltage process components
Solution Approach 2:
The patent employs periodic switching action in the signal generation circuit, using oscillating or pulsing low-voltage signals that are transformed into high-voltage square waves through periodic charge accumulation and discharge mechanisms, such as in charge pump circuits or voltage multiplier configurations
Data Source
AI summary
A fingerprint identification system includes: a fingerprint sensing circuit having a power supply terminal and a floating ground terminal, used for generating a first signal; and a signal generation circuit having a first output terminal and a second output terminal, wherein the first output terminal is coupled to the power supply terminal, and the second output terminal is coupled to the floating ground terminal, the signal generation circuit is used for generating a floating power signal to the power supply terminal according to the first signal, and for generating a floating ground signal to the floating ground terminal according to the first signal, wherein the floating power signal has a floating power amplitude, and the floating ground signal has a floating ground amplitude; and wherein the signal generation circuit has a breakdown voltage, and both the floating power amplitude and the floating ground amplitude are greater than the breakdown voltage.