Active Rectifier Control for Wireless Power Impedance Matching
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Solution Overview
Problem
Existing wireless power systems face inefficiencies in converting oscillating energy to DC power for high-voltage batteries, particularly in systems that require dual modes of operation for charging and heating, due to challenges in impedance matching and reactive current management.
Innovation Solution
The implementation of an active rectifier with capacitive snubbers and a controller that adjusts power transmission based on feedback from battery management systems, allowing for efficient impedance matching and reduced switching losses, enabling both charging and heating modes with improved power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an active rectifier is used to convert oscillating energy to DC power, then power delivery efficiency is improved, but device complexity increases due to additional components and control mechanisms
Solution Approach 1:
The patent implements an active rectifier with controllable switching elements (MOSFETs or IGBTs) that dynamically adjust their switching states based on the oscillating input signal phase. This dynamic operation enables synchronous rectification where the switching elements are turned on and off at optimal moments to minimize conduction losses and improve power delivery efficiency, while the control circuit manages the complexity through phase-synchronized control signals
Solution Approach 2:
The patent changes the operational parameters of the rectifier by using controllable switching elements instead of fixed diodes, allowing the rectification process to adapt to varying input conditions. The switching elements can modify their electrical characteristics (on-resistance, switching timing) based on the oscillating signal parameters, enabling optimized power conversion across different operating conditions while maintaining manageable complexity through parameter control
2Loss of energy
If capacitive snubbers are added to reduce switching losses, then energy loss decreases, but device complexity and component count increase
Solution Approach 1:
The patent introduces capacitive snubbers as intermediary components connected in parallel with the switching elements. These snubbers act as energy buffer elements that absorb voltage spikes and reduce switching stress during the transition periods. By providing this intermediary energy storage mechanism, the snubbers enable softer switching transitions that reduce switching losses without requiring fundamental changes to the main rectifier topology, thus limiting the increase in overall system complexity
Solution Approach 2:
The capacitive snubbers are pre-configured to provide cushioning protection to the switching elements before harsh voltage transients occur. The capacitors are charged during normal operation and automatically discharge to counteract voltage spikes during switching events, providing beforehand protection that reduces switching losses. This preventive approach allows the use of less robust (and simpler) switching elements while still achieving low switching losses
3Loss of energy
If impedance matching is optimized for high-voltage battery charging, then power transfer efficiency improves, but adaptability to different operating modes (charging and heating) decreases
Solution Approach 1:
The patent implements dynamic impedance matching through the active rectifier control system that adjusts its input impedance characteristics based on the desired operating mode. By controlling the switching timing and duty cycle of the rectifier elements, the system can dynamically present different impedance profiles to the wireless power transmitter, enabling optimization for battery charging mode while maintaining capability for resistive heating mode through control parameter adjustment
Solution Approach 2:
The active rectifier circuit is designed with universal functionality to support both battery charging and resistive heating modes. The same rectifier hardware and control system can operate in different modes by adjusting control parameters: in charging mode, the rectifier provides synchronized rectification optimized for battery voltage/current requirements, while in heating mode, the same circuit can operate with different switching patterns to deliver power to resistive loads, thus achieving multi-functionality without sacrificing efficiency in either mode
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 solution enhances power delivery efficiency to high-voltage batteries by compensating for reactive impedance shifts, increasing output power, and reducing switching losses, thereby achieving high efficiency in both charging and heating operations.
Implementation Method 1
a first capacitive snubber coupled in parallel to at least one of: (i) the first diode or (ii) the first transistor; a second capacitive snubber coupled in parallel to at least one of: (i) the second diode or (ii) the second transistor
Implementation Method 2
Wireless power receivers of such systems generally include a rectifier to convert oscillating energy to DC for delivery to a load (e.g., a battery) coupled to the receiver
Data Source
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AI summary
Disclosed herein are methods and systems for controlling an active rectifier of a wireless power receiver. The exemplary methods can include determining a reference value of a current into the rectifier, the reference value being based on a load requirement; determining a required value change in a present input current into the rectifier based on the reference value; transmitting, to a wireless power transmitter, a signal representative of the required value change in the present input current; determining a new value of the present input current after transmitting the signal; and, when the new value is within a predetermined range of the required value change, driving at least one transistor in the rectifier with a PWM signal based on the new value.