Wireless Power Transmission Circuit Harmonic Filtering
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Solution Overview
Problem
Existing wireless power transmission circuit designs, such as those by the Wireless Power Consortium, often fail to provide sufficient RF signal filtering, leading to electromagnetic interference (EMI) issues, particularly in the automotive market where stricter EMC standards apply.
Innovation Solution
Incorporating two tuned filter circuits with an inductor and a capacitor in series, tuned to the fifth harmonic of the fundamental switching frequency, between the transmitter coil and inverter, along with additional capacitors and inductors to reduce emissions within specific frequency ranges, and employing a software control loop to maintain a 50% duty cycle and adjust frequency for optimal power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If standard wireless power transmission circuit designs are used, then power transmission functionality is achieved, but electromagnetic interference emissions exceed acceptable thresholds
Solution Approach 1:
The patent introduces tuned filter circuits as intermediary components between the inverter and transmitter coil. These filters act as mediators that selectively pass the fundamental frequency while blocking harmonic frequencies, thereby reducing electromagnetic interference emissions without affecting the power transmission functionality
Solution Approach 2:
The patent modifies the electrical parameters of the circuit by adding tuned filter circuits with specific inductance and capacitance values. The filters are tuned to specific frequencies (fifth harmonic of the fundamental switching frequency) to change the frequency response characteristics and reduce emissions at problematic frequency ranges
2Object-affected harmful factors
If additional filtering components are added to reduce emissions, then electromagnetic compliance is improved, but circuit complexity increases
Solution Approach 1:
The patent divides the filtering function into separate tuned filter circuits, each targeting specific frequency ranges. By segmenting the filtering task into multiple specialized circuits rather than one complex filter, the design achieves effective emission reduction while maintaining modularity and ease of implementation
Solution Approach 2:
The patent converts the harmful harmonic frequencies generated by the inverter into beneficial filtered signals. The tuned filter circuits are designed to pass the fundamental frequency while blocking harmonics, effectively transforming the problematic frequency spectrum into a compliant emission profile
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
The solution effectively reduces peak and average electromagnetic interference emissions below acceptable thresholds, ensuring compliance with automotive EMC standards and allowing for cost and space savings by eliminating the need for a DC-DC converter.
Implementation Method 1
a transmitter coil configured to receive the alternating current and generate a magnetic field for inducing a current in a receiver coil
Implementation Method 2
two tuned filter circuits between the transmitter coil and the inverter, the tuned filter circuits including an inductor and a first capacitor in series
Data Source
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AI summary
A transmission circuit and method for wireless transmission of power, the circuit including a source of electrical energy, an inverter connected to the source of direct current electrical energy and configured to receive a control signal operable to alternately open and close switches of the inverter to produce an alternating current, a transmitter coil configured to receive the alternating current and generate a magnetic field for inducing a current in a receiver coil, and two tuned filter circuits between the transmitter coil and the inverter, the tuned filter circuits including an inductor and a first capacitor in series, and a second capacitor in parallel with the inductor and the first capacitor.