Resonant Capacitance Tuning in Wireless Power Transfer Under Load Variation
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Solution Overview
Problem
Wireless power transfer systems face inefficiencies and high voltage/current stresses due to variations in coupling coefficients and load changes, which affect output voltage regulation.
Innovation Solution
A control method that detects current levels using a sense switch and adjusts the capacitance of variable capacitance networks in both the transmitter and receiver resonant converters to optimize power transfer and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wireless power transfer systems operate with fixed capacitance values in resonant converters, then system simplicity is maintained, but output voltage regulation deteriorates due to coupling coefficient variations and load changes
Solution Approach 1:
The patent applies the dynamics principle by transforming fixed capacitance values into variable capacitance values that can be dynamically adjusted. The system includes a controller that modifies capacitance values in response to coupling coefficient variations and load changes, enabling the resonant converters to adapt their operating parameters in real-time. This dynamic adjustment mechanism resolves the contradiction by allowing the system to maintain simple architecture while achieving reliable output voltage regulation through parameter variability.
Solution Approach 2:
The patent implements parameter changes by modifying capacitance values in the resonant converters based on detected system conditions. The controller monitors coupling coefficient variations and load changes, then adjusts capacitance parameters accordingly to maintain proper resonant frequency and impedance matching. This parameter adaptation enables the system to overcome the limitations of fixed capacitance designs while maintaining overall system simplicity.
2Reliability
If wireless power transfer systems use variable capacitance networks to regulate output voltage, then voltage regulation improves, but device complexity increases
Solution Approach 1:
The patent applies feedback by implementing a control system that continuously monitors output voltage, coupling coefficient, and load conditions, then adjusts capacitance values accordingly. The controller receives feedback signals from voltage sensors and uses this information to modify capacitance parameters in the resonant converters. This feedback mechanism enables automatic voltage regulation without requiring complex manual intervention or overly complicated circuit architecture.
Solution Approach 2:
The patent implements universality by designing a control apparatus that performs multiple functions: it monitors coupling coefficient variations, detects load changes, regulates output voltage, and adjusts capacitance values all through a single integrated controller. This multi-functional approach consolidates what could be multiple separate complex subsystems into one unified control mechanism, achieving reliable voltage regulation while minimizing overall device complexity.
3Device complexity
If fixed capacitance values are used in resonant converters, then device complexity is reduced, but voltage/current stresses increase due to inability to adapt to coupling variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting capacitance values in response to coupling coefficient variations. When coupling conditions change, the controller modifies capacitance parameters to maintain proper resonant frequency and impedance matching, preventing excessive voltage and current stresses that would occur with fixed capacitance values. This adaptive parameter adjustment protects system components from harmful electrical stresses while maintaining simple overall architecture.
Solution Approach 2:
The patent implements beforehand cushioning by proactively adjusting capacitance values in anticipation of coupling variations and load changes. The control system detects early signs of coupling coefficient changes and preemptively modifies capacitance parameters to prevent excessive voltage/current stresses before they occur. This preventive approach protects system components from harmful electrical stresses while avoiding the need for complex protective circuitry.
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 improves the performance of wireless power transfer systems by regulating output voltage and reducing voltage/current stresses, enhancing efficiency and reliability.
Implementation Method 1
The primary side transmitter is magnetically coupled to the secondary side receiver(s) through a magnetic coupling. The magnetic coupling may be implemented as a loosely coupled transformer having a primary side coil formed in the primary side transmitter and a secondary side coil formed in a secondary side receiver.
Implementation Method 2
The transmitter coil, coupled to the power amplifier through a resonant circuit (usually one or more capacitors), forms a transmitter resonant tank with the resonant circuit and generates a magnetic field at the system frequency. Likewise, the receiver coil and the resonant circuit of the power receiver form a receiver resonant tank.
Data Source
AI summary
A method comprises detecting a signal representing a current level at a power switch of a resonant converter with a sense switch coupled to the power switch and formed on a same semiconductor die, wherein the resonant converter comprises a primary side and a secondary side magnetically coupled to the primary side, and adjusting a capacitance of a variable capacitance network of the resonant converter based upon the current level of the power switch.