Open-Loop Reactance Matching in Wireless Power Transfer Circuits
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in achieving precise reactance matching, especially at high reactance values, leading to inefficiencies and increased driving voltage, and require complex closed-loop controllers that are sensitive to sensor accuracy.
Innovation Solution
The implementation of an Open Loop Reactance Matching (OLRM) control circuit that uses distributed series capacitances and switched capacitors to maintain transmitter voltage and current in phase without feedback sensing, allowing for adaptive and precise reactance matching across varying loading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive reactance matching circuits are used, then the circuit structure is simple, but the matching precision is poor and driving voltage becomes excessively high at high reactance values
Solution Approach 1:
The patent replaces passive mechanical/reactive circuit elements with active semiconductor switching devices (MOSFETs, IGBTs, or GaN devices) to create an active reactance matching circuit. This substitution enables precise electronic control of reactance compensation through PWM switching, achieving accurate matching without the limitations of passive circuits while maintaining practical driving voltage levels.
Solution Approach 2:
The patent dynamically changes the switching duty cycle and frequency of the semiconductor devices to adaptively adjust the effective reactance compensation. By varying these parameters in response to load conditions, the circuit maintains optimal matching precision across different operating points without requiring complex reconfiguration of passive components.
2Measurement precision
If close loop controllers are used, then the control precision can be improved, but the system becomes sensitive to sensor accuracy and requires complex feedback sensing
Solution Approach 1:
The patent implements a self-service control mechanism where the reactance matching circuit automatically adjusts its switching parameters based on the inherent electrical characteristics of the wireless power transfer system. The control algorithm uses readily available voltage and current measurements to compute the required compensation without requiring additional precision sensors or complex feedback loops, thereby achieving high control precision with minimal system complexity.
3Reliability
If operational frequency is increased to improve coupling, then the coupling between transmitter and receiver coils is improved, but leakage reactance and resistive losses increase
Solution Approach 1:
The patent applies preliminary anti-action by introducing an active reactance matching circuit that pre-compensates for the increased leakage reactance caused by high-frequency operation. The circuit generates counteracting reactive current through controlled switching of semiconductor devices, effectively canceling out the adverse reactance effects before they can cause power loss, thereby maintaining efficient power transfer despite operating at frequencies that would otherwise produce excessive losses.
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 enables efficient wireless power transfer with reduced resistive losses and constant transmitter current, even under varying load conditions, by compensating for reactance and minimizing semiconductor switch stress, thus improving the robustness and accuracy of power transfer.
Implementation Method 1
a transmitter receives electrical energy from a power source and generates a magnetic field
Implementation Method 2
The magnetic field wirelessly transmits power to a receiver device across space
Implementation Method 3
The conductor includes a plurality of distributed capacitances coupled in series with the conductor
Implementation Method 4
power is transferred wirelessly via a transformer effect or magnetic coupling between two coupled coils
Data Source
AI summary
A system includes a power source, a transmitter circuit, a conductor, and a receiver circuit. The transmitter circuit is supplied by the power source and wirelessly supplies the receiver circuit via the conductor. The conductor includes a plurality of distributed capacitances coupled in series with the conductor. The receiver circuit includes a primary coil and a secondary coil. The primary coil has at least two turns and includes a plurality of distributed capacitances. The transmitter circuit includes an Open Loop Reactance Matching (OLRM) control circuit, a first inverter, a second inverter, and a third inverter. The OLRM control circuit controls the first inverter to generate a high frequency AC voltage to be supplied to the conductor. During wireless power transfer, the OLRM control circuit performs reactance matching by controlling the second and third inverters to maintain the transmitter voltage and current in phase without requiring any feedback sensing.