Wireless Charging Antenna Detuning for Junction Temperature Control
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Solution Overview
Problem
Wireless charging systems experience a substantial increase in junction temperature during transition periods, leading to potential overheating issues in portable devices due to inefficient power management and communication delays in feedback loops.
Innovation Solution
The portable device dynamically changes its antenna resonance frequency to adjust power intake from the magnetic field, allowing for precise power usage during different charge phases, reducing waste heat and enabling efficient power management through a detuning stage that tunes the resonance frequency closer to or farther from the carrier frequency based on charging needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power device increases power output in response to power adjustment information, then the charge current can be increased, but the junction temperature substantially increases during transition periods
Solution Approach 1:
The portable device performs preliminary detuning of its antenna before the power device increases power output. By preemptively adjusting the antenna resonance frequency away from the carrier frequency, the portable device prepares to handle the incoming power increase, reducing the temperature spike that would otherwise occur during the transition period when power adjustment information is processed.
Solution Approach 2:
The system uses feedback through power adjustment information exchanged between the portable device and power device. The portable device monitors its charging state and communicates power requirements back to the power device, enabling coordinated power management where the power device adjusts output based on actual needs, preventing excessive power delivery and associated temperature increases.
2Productivity
If the feedback loop is used to adjust power, then the charge current can be optimized, but the transition time increases due to communication delays
Solution Approach 1:
The portable device performs preliminary detuning before power adjustments are made by the power device. This advance preparation eliminates the need for extended transition periods, as the antenna is already configured to handle the upcoming power change, thereby reducing the time loss associated with feedback loop communication delays.
3Use of energy by moving object
If the antenna resonance frequency is kept close to the carrier frequency, then power transfer efficiency is maximized, but heat generation increases
Solution Approach 1:
The portable device dynamically adjusts its antenna resonance frequency based on charging requirements. During normal charging, the antenna is tuned close to the carrier frequency for efficient power transfer. During transition periods or when power adjustments are anticipated, the antenna is detuned away from resonance, dynamically changing the system state to prevent excessive heat generation while maintaining overall efficiency.
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 reduces the risk of overheating by ensuring only the necessary power is used during charging, minimizing heat generation and allowing for smaller PCB designs, while also reducing the transition time and preventing charger resets due to low input voltage.
Implementation Method 1
a detuning stage to change the resonance frequency of the antenna of the portable device
Implementation Method 2
an antenna to emit a magnetic field with a carrier frequency to power the portable device which comprises an antenna exposed to the magnetic field
Implementation Method 3
a rectifier stage, to rectify an antenna signal
Data Source
AI summary
A system including a power device for wireless charging of a battery of a portable device, and the power device has an antenna to emit a magnetic field with a carrier frequency to power the portable device which includes an antenna exposed to the magnetic field and connected via a matching stage to a rectifier stage, to rectify an antenna signal, and the portable device comprises a charge stage, to sense and limit the rectified antenna signal. The portable device includes a detuning stage to change the resonance frequency of the antenna of the portable device and that the charge stage is configured to limit the input voltage (UI) for the charger IC by steering the detuning stage to detune the resonance frequency of the antenna of the portable device away from the carrier frequency of the magnetic field.