Variable Switching Frequency DC-to-DC Converter for Wireless EV Charging
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Solution Overview
Problem
Wireless charging systems for electric vehicles face efficiency and power transfer issues due to misalignment and manufacturing tolerances between primary and secondary pads, leading to degraded resonance and reduced output power and efficiency.
Innovation Solution
A wireless charging method using a variable switching frequency, where the DC-to-DC converter tunes its frequency within a predetermined range based on initial resonance, maintaining duty at maximum value to optimize output voltage and prevent switch damage, and includes a position calibration signal to compensate for misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a fixed resonance frequency is used between primary and secondary pads, then the system operates efficiently under ideal alignment conditions, but output power and efficiency decrease when misalignment or manufacturing tolerances occur
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The DC-to-DC converter continuously adjusts the switching frequency within a predetermined range centered on the initial resonance frequency to track and maintain optimal resonance conditions despite misalignment or manufacturing variations, thereby resolving the contradiction between maintaining power output and ensuring resonance stability.
Solution Approach 2:
The patent changes the parameter of switching frequency dynamically. By varying the switching frequency based on feedback from output voltage sensing and resonance detection, the system adapts to changing coupling conditions caused by misalignment or manufacturing tolerances, maintaining both output power and resonance stability simultaneously.
2Power
If the switching frequency is increased to improve output voltage, then power transfer efficiency improves, but switch damage risk increases due to reduced zero voltage switching region
Solution Approach 1:
The patent uses dynamic frequency adjustment within a controlled range rather than a fixed high frequency. The system dynamically selects the optimal frequency that maintains sufficient output voltage while ensuring the switching operation remains within the zero voltage switching region, thus preventing switch damage while achieving power transfer efficiency.
Solution Approach 2:
The patent employs a composite control strategy combining frequency modulation with duty cycle control. By using both switching frequency variation and duty cycle adjustment, the system achieves the desired output voltage through a combination of methods, allowing operation at lower frequencies that maintain switch safety while still achieving high output voltage through coordinated 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
The method enhances output voltage and efficiency even with misalignment, broadens the zero voltage switching region, and prevents switch damage in the DC-to-DC converter, improving power transfer in wireless charging systems.
Implementation Method 1
a primary pad and a secondary pad can be modeled as a transformer in an equivalent circuit
Implementation Method 2
producing a resonance between a primary pad located outside of the vehicle and a secondary pad installed in the vehicle based on an initial switching frequency
Data Source
AI summary
A wireless charging method performed by a wireless power receiving apparatus for a vehicle includes: producing a resonance between a primary pad located outside of the vehicle and a secondary pad installed in the vehicle based on an initial switching frequency; and tuning a switching frequency of a direct current (DC) to DC (DC-to-DC) converter within a range determined based on the initial switching frequency, according to an output voltage outputted based on a resonance of the secondary pad which is caused by the primary pad.