Wireless Charging Thermal Management via Dynamic Current Limits

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Solution Overview

Problem

Existing wireless charging systems face thermal limitations that extend charging time and may terminate charging prematurely due to heat generation in coils and control circuits, reducing the convenience and efficiency of battery charging.

Innovation Solution

Implementing a multi-tiered thermal management system that adjusts charging current based on the state of charge of the battery cells, using distinct temperature thresholds to optimize charging efficiency by allowing higher currents at lower states of charge and reducing power to manage heat at higher states of charge, thereby reducing overall charging time and power dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If wireless charging is implemented with high charging current, then charging speed is improved, but thermal limitations cause charging time to extend or charging to terminate prematurely

Engineering Contradiction:

Improvecharging speedVSAvoidcharging time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent applies dynamics by making the charging current adjustable rather than fixed. The system dynamically modifies the charging current based on real-time temperature feedback from the battery and charging coil, allowing the current to increase when temperatures are low and decrease when temperatures rise, thus optimizing both charging speed and thermal management throughout the charging process

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of charging current based on temperature conditions. By monitoring temperature and adjusting the charging current parameter accordingly, the system allows higher currents when thermal conditions permit (increasing charging speed) and reduces current when temperature limits are approached (preventing thermal termination), thereby resolving the contradiction between charging speed and charging time

Inventive Principle:

Principle #35Parameter changes

2Productivity

If high charging current is used to reduce charging time, then productivity is improved, but heat generation increases causing thermal limitations

Engineering Contradiction:

Improvecharging efficiencyVSAvoidheat generation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent implements feedback control by continuously monitoring the temperature of the battery and charging coil, then using this temperature information to adjust the charging current. The temperature sensor provides real-time feedback to the control circuit, which modifies the charging current to maintain optimal thermal conditions while maximizing charging efficiency, thus resolving the contradiction between productivity and heat generation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent converts the harmful effect of heat generation into a useful control parameter. By monitoring temperature (which would normally be a limiting factor) and using it to dynamically adjust charging current, the system transforms thermal constraints into an opportunity to optimize charging efficiency - allowing higher currents when thermal conditions are favorable and adjusting when they are not, thereby improving overall productivity while managing heat generation

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach enables faster charging while maintaining battery reliability by dynamically adjusting power delivery to manage temperature, reducing charge time and heat generation, and maintaining pass elements in constant current mode to minimize power dissipation.

Implementation Method 1

wireless charging systems... induction-charging systems

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

heat generation in coils and control circuits

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9356461B2Methods and systems for rapid wireless charging where the low state of charge (SOC) temperature dependent charging current and low SOC temperature limit are higher than the high SOC temperature dependent charging current and high SOC temperature limit

Publication Date: 2016.05.31 GOOGLE TECHNOLOGY HOLDINGS LLC

AI summary

A system and method for wireless charging are provided. A control circuit charges one or more cells in a secondary wireless charging circuit that receives power wirelessly from a primary. The control circuit determines the state of charge and temperature of the cells. The control circuit then calculates a current limit as a function of a combination of the state of charge, input voltage to the control circuit for the wireless controller, FET power dissipation and the temperature and adjusts a wireless power control device in the secondary such that its current limit is set to the state of charge current limit. Different temperature limits can be used for different states of charge such that the cells can be charged at higher temperatures at low states of charge than at higher states of charge.