Smart Card Bi-Directional Voltage Converter With Stepwise Capacitor Boosting
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Solution Overview
Problem
Existing smart card technologies face challenges in performing effective fingerprint authentication without relying on charge-pumps, which can occupy significant area and reduce efficiency in voltage conversion.
Innovation Solution
A bi-directional voltage converter is introduced in the smart card, utilizing a switching circuit and start-up transistors with specific channel width ratios, and a storage capacitor to boost driving voltages step-wisely, eliminating the need for a charge-pump and enhancing efficiency and area reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a charge-pump is used for voltage boosting in smart card, then voltage conversion can be achieved, but the occupied area increases and efficiency decreases
Solution Approach 1:
The patent changes the operating parameters of the voltage conversion circuit by using transistors with at least two different selectable on-resistance values. This allows the circuit to optimize its performance by selecting appropriate resistance values for different operating conditions, achieving efficient voltage boosting without requiring a large charge-pump circuit. The parameter change enables the same circuit to adapt to different voltage conversion needs while maintaining compact size.
Solution Approach 2:
The voltage conversion circuit is designed to perform multiple functions: it can operate as a charge-pump when needed, but also functions as a general voltage regulator and converter. The circuit includes a pump capacitor and switching transistors that can be configured for different operating modes, allowing the same compact circuit to replace what would traditionally require separate dedicated charge-pump and voltage regulation circuits, thereby reducing overall occupied area while maintaining efficiency.
2Power
If a charge-pump circuit is implemented, then voltage boosting is possible, but device complexity increases
Solution Approach 1:
The patent merges the voltage boosting function with the existing voltage regulation circuitry. The pump capacitor and switching transistors are integrated into the same circuit block that performs voltage regulation, eliminating the need for a separate charge-pump circuit. This merging reduces device complexity while maintaining the voltage boosting capability, as the same components serve dual purposes: voltage conversion and voltage regulation.
Solution Approach 2:
The circuit employs dynamically controllable transistors with selectable on-resistance values that can be adjusted based on operating conditions. This dynamic adjustment allows the circuit to optimize its behavior for different voltage conversion ratios and load conditions, simplifying the overall control logic compared to a fixed charge-pump design. The dynamic parameter adjustment enables the circuit to adapt to varying requirements without adding complex control mechanisms.
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 bi-directional voltage converter effectively performs fingerprint authentication with reduced area occupation and high efficiency by boosting driving voltages without a charge-pump, improving the overall performance of smart card operations.
Implementation Method 1
The bi-directional voltage converter stores the second driving voltage applied to the output node in a storage capacitor coupled between a first node and a second node, in a boosting operation, and provides the voltage stored in the storage capacitor to the input node
Data Source
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AI summary
A bi-directional voltage (400) converter of a smart card (50) includes switching elements (MP0, MN0, MP1, MN1) connected between an input node (NI) and an output node (NO) and start-up transistors (MP2, MP3) whose channel width over channel length ratio is smaller than a channel width over channel length ration of the switching elements (MP0, MN0, MP1, MN1). The bi-directional voltage converter stores a driving voltage applied to the output node (NO) in a storage capacitor (CF) during a boosting operation and provides the voltage stored in the storage capacitor (CF) to an input node (NI). The bi-directional voltage converter (400) may boost another driving voltage at the input node (NI) step-wisely and may perform bi-directional voltage converting with reduced occupied area and high efficiency.