Wireless Power Transfer Resonance Control for Stable ZVS
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Solution Overview
Problem
Conventional wireless power transfer systems face challenges in achieving high efficiency, stability, and reliability due to varying coupling coefficients and magnetic parameters, leading to increased heat generation and poor power factor when the distance between coils deviates from a predetermined position, and it is difficult to maintain Zero Voltage Switching (ZVS) operation under various conditions.
Innovation Solution
The system employs a phase information transfer mechanism to determine the driving frequency based on resonance current phase detection from the secondary coil, allowing precise control of the primary coil's driving timing, which minimizes phase delay and enables ZVS operation even with a half-bridge circuit, and sets a high Q value for the secondary-side resonance circuit to maintain a power factor of 1, reducing copper loss and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the distance between coils deviates from a predetermined position, then power transfer efficiency deteriorates and heat generation increases, but maintaining fixed coil positioning reduces adaptability to varying operational conditions
Solution Approach 1:
The patent implements dynamic frequency adjustment and phase control mechanisms that continuously adapt to changing coupling coefficients. The system monitors the actual coupling condition and dynamically modifies driving frequency and phase angle to maintain optimal power transfer efficiency across varying distances and positions, transforming a static system into a dynamically adaptive one.
Solution Approach 2:
The system changes operational parameters (driving frequency, phase angle, Q value) based on detected coupling conditions. By adjusting these parameters in response to varying coil positions and coupling coefficients, the system maintains high efficiency without requiring fixed positioning, thus resolving the contradiction between efficiency and adaptability.
2Reliability
If conventional wireless power transfer systems operate with varying coupling coefficients, then stability and reliability deteriorate, but implementing fixed coupling conditions increases device complexity
Solution Approach 1:
The patent incorporates feedback mechanisms that monitor coupling coefficient variations and operational parameters. Based on this feedback, the system automatically adjusts driving frequency and phase angle to maintain stable and reliable operation. This closed-loop control achieves high reliability through software-based adaptation rather than complex hardware modifications.
Solution Approach 2:
The system performs self-adjustment of operational parameters based on real-time coupling conditions. By autonomously monitoring and adapting its own operation without external intervention or complex control systems, the patent achieves stable and reliable power transfer while minimizing additional device complexity.
3Loss of energy
If the coupling coefficient is small, then power transfer efficiency deteriorates, but increasing the coupling coefficient requires reducing coil distance which limits adaptability
Solution Approach 1:
The patent compensates for small coupling coefficients by dynamically adjusting driving frequency and phase angle. When coils are positioned at larger distances resulting in small k values, the system modifies operational parameters to maintain resonance conditions and maximize power transfer efficiency, eliminating the need to reduce coil distance.
Solution Approach 2:
The system dynamically adapts its operational characteristics based on real-time coupling conditions. By continuously adjusting frequency and phase in response to varying coil distances, the system maintains high efficiency across a wide range of separations, decoupling efficiency from fixed distance requirements.
4Loss of energy
If impedance matching circuits are used to control resonators, then power transfer efficiency improves, but device complexity increases due to additional components
Solution Approach 1:
The patent replaces traditional hardware-based impedance matching circuits with software-based control mechanisms. By using digital signal processing and control algorithms to achieve impedance matching and resonance conditions, the system maintains high power transfer efficiency while eliminating complex additional components, thus reducing device complexity.
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 the power transfer efficiency, reduces heat generation, and ensures stable ZVS operation across varying conditions, even when the coupling coefficient is small, by accurately controlling the phase and frequency, thereby improving the overall performance of the wireless power transfer system.
Implementation Method 1
a primary coil connected to a high-frequency power source and a secondary coil connected to a load are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying the power from the primary coil to the secondary coil in a non-contact manner
Implementation Method 2
after the magnetic field resonance (magnetic resonance) type wireless power transfer (non-contact power feeding) was proposed
Implementation Method 3
by matching the resonance frequencies of the primary-side resonator 219 and the secondary-side resonator 231 to resonate both resonators, highly efficient power transfer is achieved
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
In a wireless power transfer system, a resonance circuit is formed only on the secondary coil side, phase information of a resonance current flowing in the resonance circuit is detected, and, base on this phase information, a driving frequency is determined so that the current phase of a driving current flowing in a primary coil slightly delays from the voltage phase, thereby driving the primary coil. A Q value determined based on a leakage inductance of the secondary coil, a capacitance of a resonance capacitor, and an equivalent load resistance is set to a value greater than or equal to a value determined by Q=2/k2 (k is a coupling coefficient).