Wireless IPT Mutual Inductance Measurement Before Charging
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Solution Overview
Problem
Existing wireless inductive power transfer (IPT) systems do not effectively measure mutual inductance before charging, leading to inefficiencies and potential system overloads due to varying coupling strengths between the transmitter and receiver.
Innovation Solution
A system and method for measuring mutual inductance before charging by operating the IPT system such that the secondary AC current is zero, allowing for accurate determination based on secondary AC voltage and primary AC current, without requiring resonant frequencies to match, and using compensation circuits to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mutual inductance is not measured before charging, then the system can start charging immediately, but the system control and protection are insufficient leading to potential overvoltage or overcurrent
Solution Approach 1:
The patent performs mutual inductance measurement before charging starts. The controller measures the mutual inductance value between transmitter and receiver coils prior to initiating power transfer, allowing the system to prepare appropriate control parameters in advance and avoid overvoltage or overcurrent during charging
2Measurement precision
If the secondary AC current is not controlled to zero during measurement, then the measurement can be performed under normal operating conditions, but the mutual inductance measurement precision is insufficient
Solution Approach 1:
The patent changes the operating parameter by controlling the secondary AC current to zero during mutual inductance measurement. The controller adjusts the receiver resonant circuit to maintain zero secondary current condition, which simplifies the measurement formula and improves precision without requiring complex additional hardware
3Measurement precision
If resonant frequencies are required to match for measurement, then the measurement can be performed at resonant conditions, but the device complexity increases due to frequency matching requirements
Solution Approach 1:
The patent changes the measurement approach by not requiring resonant frequency matching. Instead of operating at resonant frequencies, the system measures mutual inductance at arbitrary frequencies by controlling secondary current to zero, which simplifies the measurement process and reduces device complexity while maintaining accuracy
4Productivity
If compensation circuits are not used, then the system structure is simpler, but the charging efficiency is reduced due to varying coupling strengths
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the mutual inductance value and adjusts the transmitter or receiver resonant circuit parameters accordingly. This feedback control maintains optimal coupling conditions and compensates for variations in mutual inductance, improving charging efficiency without requiring complex additional compensation circuits
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 precise mutual inductance measurement before charging, improving system control and protection by adjusting power parameters and reducing the risk of overvoltage or overcurrent, thus enhancing charging efficiency and safety.
Implementation Method 1
a transmitter resonant circuit configured to transmit a primary alternating current (AC) power... a receiver resonant circuit inductively coupled with the transmitter resonant circuit and configured to receive the primary AC power
Implementation Method 2
Mutual inductance indicates the strength of coupling between the transmitter and the receiver. Measuring mutual inductance before charging is desirable for the control and operation of the transfer system
Data Source
AI summary
A wireless inductive power transfer (IPT) system for wirelessly charging electrical equipment is provided. The system includes a transmitter resonant circuit configured to transmit a primary alternating current (AC) power. The system also includes a receiver resonant circuit inductively coupled with the transmitter resonant circuit and configured to receive the primary AC power and output a secondary AC power. The system further includes a mutual inductance measurement circuitry configured to measure a mutual inductance between the transmitter resonant circuit and the receiver resonant circuit before initiating charging of electrical equipment by operating the IPT system such that the secondary AC current is zero at an operating frequency of the IPT system, measuring the secondary AC voltage and the primary AC current, determining the mutual inductance based on the secondary AC voltage and the primary AC current, and outputting the determined mutual inductance.