Magnetic Foil Power Receiving Device for Wireless Charging
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Solution Overview
Problem
Conventional non-contact charging methods for electronic devices, particularly those using Li ion secondary batteries, face inefficiencies due to heat generation caused by eddy currents during electromagnetic induction, leading to prolonged charging times and potential battery damage.
Innovation Solution
A power receiving device with a spiral coil, rectifier, and a magnetic foil positioned between the coil and secondary battery, where the magnetic foil has a saturation flux density and thickness product (Ms·t) of 15 or more, effectively shields magnetic flux and reduces eddy current-induced heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a planar coil is used for non-contact charging, then the device thickness is reduced, but heat generation due to eddy current increases and charging efficiency decreases
Solution Approach 1:
A magnetic foil is introduced as an intermediary component between the planar coil and the secondary battery. This magnetic foil serves as a magnetic shield that guides magnetic flux through itself rather than allowing it to pass through the battery, thereby preventing eddy current generation in the battery while maintaining the thin planar coil structure.
Solution Approach 2:
The harmful function of the magnetic flux passing through the battery is extracted and redirected. By placing the magnetic foil between the coil and battery, the magnetic flux is taken out from the battery path and confined to flow through the magnetic foil, eliminating the harmful eddy current effect while preserving the beneficial charging function.
2Productivity
If magnetic flux is increased to improve power transmission speed, then charging speed increases, but heat generation and battery damage risk increase
Solution Approach 1:
The magnetic flux that would otherwise cause harmful eddy currents in the battery is converted into a beneficial effect by redirecting it through the magnetic foil. The magnetic foil transforms the potentially harmful high magnetic flux into a useful function by confining it to a safe path, enabling fast charging without battery damage.
Solution Approach 2:
The magnetic foil acts as a mediator that allows high magnetic flux to be used for fast charging while protecting the battery from its harmful effects. It provides a dedicated pathway for magnetic flux that separates the charging function from the battery protection requirement.
3Ease of operation
If conventional non-contact charging is used, then contact pressure requirements are eliminated, but charging time becomes excessively long
Solution Approach 1:
The magnetic foil changes the magnetic parameters (flux density distribution) in the charging system. By concentrating and guiding magnetic flux through the foil, the coupling efficiency between primary and secondary coils is improved, enabling faster charging while maintaining the contactless operation advantage.
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 configuration enhances power reception efficiency, reduces charging time, and prevents battery overheating, making it suitable for high-capacity Li ion batteries.
Implementation Method 1
a magnetic foil arranged in at least one of a position between the spiral coil and the secondary battery, and a position between the spiral coil and the rectifier
Implementation Method 2
The non-contact charging method provides a coil to both the power receiving device and the power feeding device and performs charging by electromagnetic induction
Implementation Method 3
heat is produced within the device because of an eddy current generated by the electromagnetic induction
Implementation Method 4
a rectifier rectifying an alternating voltage generated in the power receiving coil
Data Source
AI summary
Disclosed is an electronic apparatus (1) comprising a power receiving device (2) and an electronic apparatus main body (3). The power receiving device (2) comprises a power receiving coil (11) having a spiral coil, a rectifier (12) and a secondary battery (13). The electronic apparatus main body (3) comprises an electronic device (14) and a circuit board (15). A magnetic foil (16) is arranged in at least one position between the spiral coil (11) and the secondary battery (13), the rectifier (12), the electronic device (14) or the circuit board (15). The magnetic foil (16) has a value expressed as the product of the saturation flux density MS and the thickness t, namely Ms·t, of not less than 15.