Rectifier Topology for Near Field Power Harvesting
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Solution Overview
Problem
Existing power harvesting systems for near field communications devices, such as RFID and NFC enabled devices, face inefficiencies and increased interaction time due to mismatched impedance between rectifiers and power management modules, particularly when high RF power is available, which is detrimental for auxiliary functions like biometric authentication.
Innovation Solution
A rectifier topology with a shunt rectifying element and matching networks is introduced to improve impedance matching and reduce output voltage while maintaining efficiency, allowing for the use of high RF input power to power auxiliary circuits like biometric sensors and data processors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional rectifier topology is used for power harvesting, then the rectifier can convert RF voltage to DC electrical energy, but the output impedance and voltage are mismatched with power management modules, reducing power transfer efficiency
Solution Approach 1:
The patent introduces an intermediary circuit between the rectifier and power management module that includes a transformer and switching elements. This intermediary circuit acts as an impedance transformation stage, matching the high output impedance of the rectifier to the low input impedance of the power management module, thereby improving power transfer efficiency without significantly increasing overall system complexity
Solution Approach 2:
The patent employs parameter changes by using a transformer with adjustable turns ratio and switching elements that can dynamically change the output voltage and impedance characteristics of the rectifier circuit. This allows the system to adapt to different load conditions and maintain optimal power transfer efficiency across varying operating conditions
2Power
If high RF input power is available, then more power can be harvested for auxiliary functions, but the output voltage becomes excessively high and mismatched with auxiliary circuit requirements
Solution Approach 1:
The patent implements a dynamic voltage regulation mechanism using switching elements (MOSFETs or BJTs) that can rapidly switch between different circuit configurations. This dynamic switching allows the system to maintain optimal voltage levels for auxiliary circuits even when input RF power varies, preventing excessive output voltage while maximizing power utilization
Solution Approach 2:
The patent segments the power harvesting system into distinct functional stages: rectification stage, impedance transformation stage, and voltage regulation stage. This segmentation allows each stage to be optimized independently - the rectifier maximizes power conversion, the transformer provides impedance matching, and the switching circuitry regulates output voltage - thereby solving the voltage matching problem while maintaining high power harvest
3Reliability
If biometric authentication and data processing are performed, then security and functionality are improved, but power consumption increases significantly
Solution Approach 1:
The patent implements energy self-service by harvesting power from the RF signals already present in the communication channel. The power management module and auxiliary circuits (including biometric sensors and processors) are powered entirely or partially by the harvested RF energy, eliminating the need for external power sources or batteries and enabling secure authentication operations with minimal additional power burden
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
This solution reduces the output impedance and voltage of the rectifier, enhancing the efficiency of power harvesting and reducing the interaction time of near field communications devices, particularly when significant RF power is available, thereby improving the overall performance of systems with auxiliary processing requirements.
Implementation Method 1
an inductive coupler for coupling inductively with a radio frequency, RF, H-field to provide an alternating RF voltage
Implementation Method 2
a rectifier for converting the alternating RF voltage into DC electrical energy
Data Source
AI summary
An apparatus comprising: an inductive coupler for coupling inductively with a radio frequency, RF, H-field to provide an alternating RF voltage; a near field, RF, communicator connected to the inductive coupler for performing near field RF communication; an auxiliary circuit connected to the inductive coupler by a rectifier for obtaining DC electrical energy from the alternating RF voltage wherein the auxiliary circuit is arranged to communicate data with the near field RF communicator; wherein the rectifier comprises: a first rectifier input and a second rectifier input for receiving the alternating RF voltage, a first rectifier output and a second rectifier output for providing the DC electrical energy to the auxiliary circuit; a rectifying element connected between the first rectifier input and the second rectifier input wherein the first rectifier output is coupled to an output of the rectifying element and to the first rectifier input by a first inductor.