Passive Wireless Charging Adapter for Mismatched Coil Sizes
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Solution Overview
Problem
Existing wireless charging technologies face inefficiencies and foreign-object heating issues when charging small-form-factor devices due to mismatched coil sizes and distances, particularly with wearable technology, which are not compatible with existing wireless chargers designed for larger devices.
Innovation Solution
A passive adapter with two coils of differing sizes, connected by a capacitor and separated by a core material, forms a resonant circuit to improve magnetic coupling and power transfer efficiency, allowing charging of small-form-factor devices using existing wireless chargers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small receiving coil is used in wearable devices to match the small form factor, then the device size is reduced, but the power transfer efficiency deteriorates due to poor coupling with the fixed-size transmitter coil
Solution Approach 1:
The passive adapter acts as an intermediary device between the transmitter coil and the receiver coil. It includes a first coil that couples to the transmitter coil and a second coil that couples to the receiver coil, with the two coils separated by a core material that prevents direct mutual coupling. This intermediary structure enables efficient power transfer between mismatched coil sizes without requiring direct coupling between the transmitter and receiver coils.
2Loss of energy
If a large transmitter coil is used to improve power transfer efficiency, then the coupling is improved, but foreign-object heating of metal housings increases
Solution Approach 1:
The passive adapter segments the magnetic coupling path into two separate stages. The first coil couples to the transmitter coil and the second coil couples to the receiver coil, with the core material physically separating the two coils to prevent direct mutual coupling. This segmentation allows the system to achieve good coupling at each stage while limiting the overall magnetic field exposure that causes foreign-object heating.
3Volume of moving object
If the coils are separated by a large distance to accommodate small-form-factor devices, then the device form factor is improved, but the power transfer efficiency deteriorates
Solution Approach 1:
The passive adapter with its core material acts as a magnetic intermediary that extends the effective coupling range. The core material provides a magnetic path that bridges the gap between the first and second coils, enabling efficient power transfer even when the adapter is positioned at distances greater than 4 cm from the transmitter coil, thereby accommodating small-form-factor 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
The passive adapter enhances magnetic coupling and power-transfer efficiency, reducing foreign-object heating and enabling high-efficiency wireless charging according to Qi standards, even at distances greater than 4 cm, for small-form-factor devices.
Implementation Method 1
The first coil is wound to have a first size and is configured to generate an electric current based on exposure of the first coil to a first magnetic field
Implementation Method 2
The capacitor is electrically connected to the first coil. The capacitor is configured to store energy based on the electric current generated by the first coil
Implementation Method 3
The second coil is electrically connected to the capacitor and the first coil. The second coil is wound to have a second size that is different than the first size of the first coil. In addition, the second coil is configured to generate a second magnetic field based on the stored energy from the capacitor
Implementation Method 4
separated by a core material that prevents mutual coupling between the coils
Data Source
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AI summary
This document describes a passive adapter (102) for wireless charging of an electronic device and associated methods and systems. The described passive adapter includes two coils (104, 106) connected by a capacitor (108) and separated by a core material that prevents mutual coupling between the coils. These two coils may have differing sizes, such that one coil can size-match to a transmitter coil (306) of an existing wireless charger (302) and the second coil can size-match to a smaller (or larger) receiver coil (310) in a wireless-power receiver (304) to charge a battery (718) of the wireless-power receiver. In aspects, these two coils may be separated by a distance that enables the passive adapter to act as a passive repeater by bridging a space between the transmitter coil and the receiver coil.