RF Rectifier Power Transfer Optimization
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Solution Overview
Problem
The varying impedance of RF rectifiers in wireless devices makes it difficult to maximize power transfer efficiency from radio-frequency (RF) energy to voltage regulators, as it is affected by operating conditions and impedance mismatches.
Innovation Solution
A wireless device with multiple RF rectifiers and a voltage regulator, where a controller optimizes power transfer by comparing the output voltage of loaded RF rectifiers to an open circuit output voltage from a reference RF rectifier, adjusting the input impedance of the voltage regulator to maintain an optimal voltage ratio for efficient power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the input impedance of the voltage regulator is fixed, then the device complexity is reduced, but the power transfer efficiency deteriorates due to impedance mismatch with the varying RF rectifier output
Solution Approach 1:
The voltage regulator dynamically adjusts its input impedance based on the RF rectifier's varying output impedance to maintain optimal power transfer. The controller modifies the regulator's operation mode (buck/boost) and impedance characteristics in response to changing operating conditions, transforming a static system into an adaptive one that tracks the rectifier's impedance variations.
Solution Approach 2:
The system implements feedback control by monitoring the RF rectifier's output voltage and current, comparing the actual power transfer against optimal values, and adjusting the voltage regulator's input impedance accordingly. This closed-loop control ensures maximum power extraction from the rectifier despite impedance variations.
2Loss of energy
If the voltage regulator adjusts its input impedance to match the RF rectifier output, then the power transfer efficiency is improved, but the device complexity increases
Solution Approach 1:
The voltage regulator is designed with multi-functionality, serving both as a power conversion device (buck/boost regulation) and as an impedance matching device. By integrating impedance adjustment capabilities within the existing voltage regulator architecture, the patent avoids adding separate impedance matching circuitry, thereby limiting the increase in device complexity.
Solution Approach 2:
The system changes the operating parameters of the voltage regulator (switching frequency, duty cycle, converter mode) to dynamically adjust its input impedance. These parameter modifications allow the regulator to adapt to the RF rectifier's varying output impedance without requiring additional hardware components.
3Power
If multiple RF rectifiers operate simultaneously, then the total power output increases, but the impedance variation and difficulty of maximizing power transfer increases
Solution Approach 1:
The patent combines multiple RF rectifiers into a unified power harvesting system with a single voltage regulator that serves all rectifiers. The controller merges the output of multiple rectifiers and applies centralized impedance matching and power management, simplifying the overall control architecture compared to individually managing each rectifier.
Solution Approach 2:
The system segments the power management function by separating the RF-to-DC conversion (performed by individual rectifiers) from the impedance matching and voltage regulation (performed by the centralized voltage regulator). This segmentation allows each rectifier to operate independently while benefiting from centralized optimization.
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 approach enhances power transfer efficiency by maintaining an optimal voltage ratio between loaded and open circuit output voltages, improving the overall energy harvesting and utilization in wireless devices.
Implementation Method 1
RF rectifier operation may be determined, in part, by operating conditions. For example, as RF signal strength increases or decreases, the power produced by the RF rectifiers may also increase or decrease.
Implementation Method 2
The output power produced by the RF rectifier may be provided to a voltage regulator for regulation.
Data Source
AI summary
This disclosure provides a method and apparatus for optimizing power transfer from radio-frequency (RF) rectifiers to a voltage regulator. A first RF rectifier may be configured to generate a first voltage and a second RF rectifier may be configured to generate a second voltage, where the second voltage is an open circuit output voltage. The voltage regulator may regulate the first voltage to provide power. A controller may be configured to optimize power transfer from the first RF receiver to the voltage regulator based on the first voltage and the second voltage.