Multi-Coil Wireless Power Transmission for Wearable Devices
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Solution Overview
Problem
Power reception coils in wearable devices like watches face inefficiencies in power transfer due to the need for parallel alignment with power transmission coils, which can be hindered by metal back lids causing eddy currents and non-separable watchbands, limiting flexible placement.
Innovation Solution
A power transmission apparatus comprising a first and second planar power transmission coil, where the second coil has a larger opening diameter and is arranged at an angle relative to the first coil, allowing for efficient power transfer regardless of the relative arrangement between the power reception and transmission coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power reception coil is mounted in parallel with the dial to capture magnetic flux, then power reception efficiency is improved, but the dial becomes invisible during power reception operation
Solution Approach 1:
The patent introduces a third power transmission coil arranged perpendicular to the first two coils, adding a vertical dimension to the magnetic field generation. This allows the power reception coil to be oriented vertically (perpendicular to the dial) rather than horizontally, maintaining dial visibility while still capturing magnetic flux effectively through the vertically oriented third coil.
2Loss of energy
If the metal back lid side is brought close to the power transmission apparatus, then power reception can be performed, but eddy currents occur in the back lid reducing efficiency
Solution Approach 1:
The patent divides the power transmission function into three separate coils (first, second, and third coils) arranged in different orientations. This segmentation allows selective use of coils based on the receiving device's orientation, enabling effective power transmission without requiring the metal back lid to be close to the transmission apparatus, thereby avoiding eddy current losses.
3Strength
If the watchband buckle portion is not fully separable, then the watch structure is more durable, but the watch cannot be placed flat with the back lid side down for power reception
Solution Approach 1:
The patent adds a third power transmission coil oriented perpendicular to the plane of the first two coils. This enables the system to receive power in multiple orientations including vertical placement, allowing watches with non-separable buckles to be charged in positions that maintain both structural integrity and power reception capability.
4Device complexity
If a single power transmission coil is used, then the device structure is simple, but efficient power transfer cannot be achieved across various angles and orientations
Solution Approach 1:
The patent implements a dynamic power transmission system with three coils that can be selectively activated based on the receiving device's orientation. The system adapts its magnetic field configuration by engaging different coil combinations, providing efficient power transfer across various angles and positions while maintaining a relatively simple overall structure.
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
Enables efficient power transfer across various angles and orientations, overcoming alignment and material-induced inefficiencies, ensuring reliable charging of wearable devices.
Implementation Method 1
an electromagnetic field generated by passing a current through a coil on a power transmission apparatus side (i.e., power transmission coil) is used to transfer power to a coil on a power reception apparatus side (i.e., power reception coil)
Implementation Method 2
If the metal-made back lid side is brought close to the power transmission apparatus for power transfer, eddy currents occur in the back lid and power reception cannot be performed efficiently
Data Source
AI summary
A power transmission apparatus includes a first power transmission coil having a planar shape, and a second power transmission coil having a planar shape, arranged outside the first power transmission coil. The second power transmission coil has an opening with a diameter greater than that of an opening of the first power transmission coil in a direction of a line of intersection on which a plane including a coil plane of the first power transmission coil and a plane including a coil plane of the second power transmission coil intersect with each other. The power transmission apparatus transmits power to a power reception coil without contact.