Resonant Capacitor Switching in Wireless Power Transfer to Limit Surge Current
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Solution Overview
Problem
Existing wireless power transfer systems face inefficiencies due to stress on devices during capacitor switching, particularly from large surge currents when capacitors are switched in, leading to potential damage and transient power loss.
Innovation Solution
Implementing a control circuit to manage capacitor switching based on event-based and drive-based methods, where switching is controlled by detecting specific voltage or current conditions to minimize surge currents, ensuring capacitors are switched in when conditions are favorable, and gradually turning on switches to avoid stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If capacitors are switched in during wireless power transfer, then power transfer capability is improved, but large surge currents cause stress on devices and transient power loss
Solution Approach 1:
The control circuit detects voltage across the first capacitor or current through the transmitter coil before switching, and only enables the switch when predetermined conditions are met (voltage near zero or current at minimum). This preliminary detection and conditional enabling prevents large surge currents from occurring when the capacitor is switched in, thereby improving reliability while maintaining power transfer capability
Solution Approach 2:
The control circuit continuously monitors the voltage across the first capacitor or current through the transmitter coil and uses this feedback information to determine the optimal timing for switching the capacitor. By basing the switching decision on real-time system state feedback, the control circuit ensures that switching occurs at favorable moments, minimizing surge currents and stress on devices
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 reduces stress on devices, enhances wireless power transfer efficiency, and maintains system stability by minimizing surge currents and transient power loss during capacitor switching.
Implementation Method 1
A wireless power transfer system typically includes a primary side transmitter and a secondary side receiver. The primary side transmitter is magnetically coupled to the secondary side receiver through magnetic coupling. The magnetic coupling may be implemented as a loosely coupled transformer having a primary side coil formed in the primary side transmitter and a secondary side coil formed in the secondary side receiver.
Implementation Method 2
Method and Apparatus for Wireless Power Transfer with Resonant Capacitor Switching
Data Source
AI summary
An apparatus for wireless power transfer includes a resonant circuit comprising: a transmitter coil; a first capacitor connected with the transmitter coil in series; and a second capacitor connected in series with a first switch. The second capacitor and the first switch are connected in parallel with the first capacitor. A control circuit is connected to the resonant circuit, and is configured to: detect whether an event of a voltage across the first capacitor or a current of the transmitter coil occurs; and when detecting that the event occurs, control to turn on the first switch in response to a signaling of turning on the first switch. A method for controlling switching-in of the second capacitor is also provided.