Wireless Power Transfer Control Using Phase-Angle Frequency Tuning
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in handling significant voltage differences between input and output, particularly in high-power charging scenarios, which complicates the design and operation of DC/DC converters and results in high currents that are difficult to manage, especially on the secondary side.
Innovation Solution
The system rearranges the DC/DC converter to the primary stage, allowing for a variable switching frequency DC/AC inverter and a controller to adjust the phase angle between input current and voltage, reducing phase shift and thereby minimizing resistive losses and using a high-voltage low-voltage transformer in the secondary stage to adapt voltages, thus reducing exposure to high currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC/DC converter is used in the secondary stage to handle significant voltage differences, then the system can achieve high-power charging, but the converter becomes difficult to design, implement and operate due to high currents
Solution Approach 1:
The system divides the voltage conversion function into two separate stages: a first DC/DC converter in the primary circuit handling initial voltage adjustment, and a second DC/DC converter in the secondary circuit handling final voltage matching. This segmentation allows each converter to operate at lower, more manageable current levels, reducing design and operational complexity while maintaining high-power charging capability
Solution Approach 2:
The patent introduces an intermediate voltage conversion stage in the primary circuit that acts as a mediator between the high-voltage input and the secondary circuit. This intermediary converter reduces the voltage burden on the secondary DC/DC converter, making it easier to design and operate while still enabling high-power transfer to the battery
2Power
If high currents are used for high-power charging with significant voltage differences, then the charging power increases, but the high currents become difficult to manage especially on the secondary side
Solution Approach 1:
The dual DC/DC converter architecture segments the current management task across two stages. The first converter in the primary circuit handles initial current regulation at higher voltage, while the second converter in the secondary circuit manages final current delivery at lower voltage. This segmentation makes current management easier by distributing the burden across two manageable stages rather than requiring one high-current converter
Solution Approach 2:
The system dynamically adjusts operating parameters (voltage and current levels) at different stages of the power transfer process. By changing the voltage-current parameter combination between the primary and secondary circuits, the system achieves high-power transfer while keeping current levels manageable at each stage, improving ease of operation
3Productivity
If the switching frequency of the DC/AC inverter is increased to improve power transfer, then the power transfer efficiency improves, but the phase angle between input current and voltage increases causing higher resistive losses
Solution Approach 1:
The controller implements feedback control by continuously monitoring the phase angle between input current and voltage, and adjusting the switching frequency of the DC/AC inverter to maintain the phase angle within a predetermined range. This feedback mechanism ensures high power transfer rates while minimizing resistive losses by dynamically optimizing the operating frequency
Solution Approach 2:
The system dynamically adjusts the switching frequency of the DC/AC inverter based on real-time operating conditions and phase angle measurements. This dynamic adjustment allows the system to maintain optimal performance across varying load conditions, achieving high productivity while minimizing energy losses through adaptive frequency control
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 configuration enhances the efficiency and reliability of the wireless power transfer by reducing resistive losses and allowing the use of lighter-duty converters, effectively managing high-power charges with significant voltage step-downs while minimizing exposure to high currents.
Implementation Method 1
The primary coil 114 is configured to transfer power to the secondary coil 121. The secondary coil 121 is coupled to the primary coil 114, e.g. via a magnetic coupling.
Implementation Method 2
The DC/AC inverter 112 is configured to power a resonant tank 113. For example, the resonant tank 113 may comprise an LC resonant circuit.
Data Source
AI summary
A method of controlling a wireless power transfer system comprising a primary stage and a secondary stage is provided. The primary stage comprises a DC/DC converter configured to generate a DC output, a DC/AC inverter configured to receive the DC output and to generate an AC output according to a variable switching frequency, and a primary coil configured to transfer power to the secondary stage in response to the DC/AC inverter generating the AC output. The switching frequency of the DC/AC inverter is adjusted to cause a phase angle between an input current and an input voltage of the primary coil to be less than or equal to a predetermined threshold. The DC output of the DC/DC converter is controlled to cause a desired amount of power to be transferred from the primary coil at the adjusted switching frequency.