Class-E Wireless Charger Impedance Tuning for Stable Output
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Solution Overview
Problem
Class-E power amplifiers in wireless charging systems experience significant changes in output efficiency and power when the load device changes in location or size, leading to potential damage and accelerated battery aging, as existing solutions do not effectively maintain efficiency and stability across varying load conditions.
Innovation Solution
A wireless charger with a class-E power amplifier and a tunable impedance circuit, including a switching transistor and tunable capacitance circuit, is equipped with a control unit that adjusts capacitance and impedance values to match target equivalent load impedances, ensuring efficient and stable output by setting a target efficiency and output power, thereby maintaining optimal performance across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a class-E power amplifier is used in wireless charging, then the structure is simple and implementation is easy, but the output efficiency and output power change significantly when the load device changes in location and size
Solution Approach 1:
The patent applies dynamics by making the impedance matching network adjustable and adaptive. The control unit dynamically adjusts the impedance parameters based on real-time detection of load conditions, transforming a static circuit into a dynamic system that can adapt to varying load positions and sizes, thereby maintaining stable output efficiency
Solution Approach 2:
The patent changes the impedance parameters of the matching network to optimize performance under different load conditions. By adjusting the impedance values in response to detected load changes, the system maintains efficient power transfer across varying operational scenarios
2Adaptability or versatility
If the output power changes within a comparatively great range to adapt to different load conditions, then the adaptability improves, but damage is caused to the load device such as accelerated battery aging
Solution Approach 1:
The patent implements feedback by using the control unit to detect load conditions and adjust the impedance matching network accordingly. This closed-loop control ensures that the output power remains within safe ranges, preventing harmful effects on the battery while adapting to different load requirements
Solution Approach 2:
The impedance matching network serves as an intermediary between the power amplifier and the load device. It mediates the power transfer by transforming impedance to match the load characteristics, thereby protecting the battery from excessive power fluctuations while maintaining adaptability
Data Source
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AI summary
Embodiments of this application provide a wireless charger and a control method. The wireless charger includes a class-E power amplifier and a tunable impedance circuit that is connected to an output end of the class-E power amplifier. The class-E power amplifier includes a switching transistor and a tunable capacitance circuit that is parallelly connected to the switching transistor. The wireless charger further includes a control unit, configured to obtain a constraint condition of the class-E power amplifier; determine N1 target equivalent load impedances of the class-E power amplifier based on the constraint condition; and adjust a capacitance value of the tunable capacitance circuit in the class-E power amplifier, and adjust an impedance value of the tunable impedance circuit, to enable an equivalent load impedance of the class-E power amplifier to match one of the N1 target equivalent load impedances. Because the equivalent load impedance of the class-E power amplifier matches the target equivalent load impedance, the wireless charger provided in the embodiments of this application can implement efficient and stable output of the class-E power amplifier.