Capacitively Balanced Inductive Charging Coil for Noise Reduction
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Solution Overview
Problem
Conventional inductive charging coils generate unbalanced capacitance, leading to unwanted common mode noise that interferes with touch sensors and other functionalities in portable electronic devices, making them inoperable during charging.
Innovation Solution
The coils are designed with balanced capacitive effects by orienting the windings such that the surface area of each half is approximately equal, reducing noise through specific winding configurations that equalize capacitance, such as having the wire cross itself at the edge of the coil halves or forming windings in a planar layer with equal lengths on either side of the center point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coil windings are used, then inductive charging functionality is achieved, but unbalanced capacitance causes common mode noise that interferes with touch sensors
Solution Approach 1:
The patent applies asymmetry by intentionally creating symmetric balance in the coil winding configuration. The coil is designed with equal number of turns and equal wire length on each side of the center point, which balances the capacitance to ground on both sides. This symmetric arrangement counteracts the unbalanced capacitance that would otherwise generate common mode noise, thereby resolving the contradiction between maintaining touch sensor reliability and eliminating noise.
Solution Approach 2:
The patent changes the geometric parameters of the coil winding to achieve balanced capacitance. Specifically, the wire is routed to ensure equal length and equal number of turns on each side of the center point, which directly adjusts the capacitance parameters to be equal on both sides. This parameter adjustment eliminates the capacitance imbalance that causes common mode noise while preserving inductive charging functionality.
2Use of energy by moving object
If inductive charging is implemented, then wireless power transfer is achieved, but capacitive losses increase and noise is generated
Solution Approach 1:
The patent changes the geometric parameters of the coil to minimize capacitive losses. By configuring the winding to have equal length and equal turns on each side of the center point, the capacitance to ground is balanced and minimized. This parameter optimization reduces reactive power losses and improves the efficiency of wireless power transfer while maintaining the required power transfer capability.
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 design significantly reduces unwanted noise and capacitive losses, ensuring the operational integrity of touch sensors and other features in portable electronic devices during inductive charging.
Implementation Method 1
Inductive charging is a method by which a magnetic field transfers electricity from an external charger to a mobile device such as a phone or laptop computer eliminating wired connection. Induction chargers typically use an induction coil to create an alternating electromagnetic field
Implementation Method 2
The windings i.e., turns of the coil are oriented such that the surface area of wire on each half of the coil is approximately equal in order that the capacitive effects produced by the coils are balanced and noise is thus substantially reduced
Data Source
AI summary
An inductor coil includes a wire which is wound in alternating layers such that the surface area of the wire in each winding viewed from above or below the coil is substantially equal in each half of the coil defined by a line bisecting the center point in each layer. The layers are also wound in a serpentine fashion to balance the capacitance between layers. The substantially equal surface area of wire in each half of a coil layer and in adjacent coil layers results in a balanced capacitance of the coil which, in turn, results in reduced common mode noise.