Resonant Circuit Frequency Tracking for Inductive Charging
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Solution Overview
Problem
Existing inductive battery charging systems face challenges in achieving efficient power transfer when the physical relationship between the primary and secondary windings is not precisely predetermined, leading to reduced magnetic coupling and increased power losses, particularly due to shunting by storage cell materials and flux-concentrating magnetic materials.
Innovation Solution
The implementation of a system with transmit and receive resonant circuits operating at matched frequencies, utilizing high-Q resonant circuits with capacitors and coils wound around ferrite or cobalt-based cores, and a control mechanism to maintain the magnetic field at the resonant frequency, ensuring efficient power transfer and communication of charging needs without additional data paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If close and predetermined physical relationship between primary and secondary windings is used, then tight magnetic coupling is achieved, but adaptability to various receiving devices is reduced
Solution Approach 1:
The system dynamically adjusts the drive frequency to track the resonant frequency of the secondary circuit, allowing the primary and secondary circuits to maintain resonant coupling even when physical positioning varies. This dynamic frequency adjustment enables the system to adapt to different receiving devices and positions while maintaining efficient power transfer.
Solution Approach 2:
The patent changes the operating parameter (frequency) from a fixed value to a variable that tracks the resonant frequency. By monitoring the phase relationship between primary current and voltage, the system adjusts the drive frequency to maintain resonance, thereby optimizing coupling efficiency across varying physical configurations and device types.
2Productivity
If resonant frequency tracking is implemented, then power transfer efficiency is improved, but device complexity increases
Solution Approach 1:
The system employs feedback by monitoring the phase relationship between primary current and voltage to detect deviations from resonant operation. Based on this feedback, the drive frequency is automatically adjusted to restore resonance, creating a closed-loop control system that maintains optimal power transfer efficiency without requiring complex external control mechanisms.
Solution Approach 2:
The resonant coupling system is self-regulating through the natural resonant properties of the circuits. When the secondary circuit is loaded or its resonant frequency shifts, the phase relationship changes automatically, and the system responds by adjusting the drive frequency to maintain resonance, effectively self-correcting without external intervention.
3Power
If magnetic field strength is increased to compensate for poor coupling, then power transfer is improved, but energy losses increase
Solution Approach 1:
The system exploits resonant oscillation in both primary and secondary circuits to amplify the magnetic field coupling effect. At resonant frequency, the oscillating magnetic fields between primary and secondary windings reinforce each other, creating strong coupling without requiring excessive drive power. This resonant amplification allows efficient power transfer at lower power levels compared to non-resonant approaches.
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 coupling efficiency, reduces power losses, and allows for effective charging of batteries with improved volumetric efficiency and simplified charge need sensing, maintaining a strong magnetic field across a range of distances and orientations.
Implementation Method 1
transmit circuitry configured to produce alternating current in the transmit coil to generate a magnetic field at about the transmit resonant frequency
Implementation Method 2
transmit resonant circuit that exhibits resonance at a transmit resonant frequency
Data Source
AI summary
Systems and methods for maintaining a drive signal to a resonant circuit at a resonant frequency are provided. A system for maintaining a drive signal to a resonant circuit at a resonant frequency can include: an oscillator configured to provide an output to a phase comparator and a drive circuit, the drive circuit configured to provide a drive signal to a resonant circuit; a phase detector configured to receive a filtered version of the drive signal from the resonant circuit and provide a phase-indicating signal to the phase comparator; and the phase comparator, wherein the phase comparator is configured to provide a signal based on the phase difference between the oscillator output and the phase-indicating signal, wherein the signal from the phase comparator is used to control the frequency of the oscillator such that the phase difference converges to a fixed value.