Wireless Power Transmitter Frequency Dithering for EMI Reduction
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Solution Overview
Problem
Current wireless power transmitters face challenges in reducing electromagnetic interference (EMI) and compliance with emission standards, particularly as future specifications may require operation at frequencies above 150 kHz, where existing solutions lead to power losses and heating issues.
Innovation Solution
Implementing a multi-frequency operation in wireless power transmitters, where the operating frequency alternates between a fundamental frequency and adjacent lower and upper frequencies, spreading energy content across multiple frequencies to reduce undesired radiation and maintain power balance, using a frequency dithering technique to ensure compliance with emission standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If wireless power transmitters operate at frequencies above 150 kHz to meet future specifications, then power transfer capability is improved, but electromagnetic interference and radiation increase
Solution Approach 1:
The patent segments the power transmission across multiple frequency components instead of using a single frequency. The transmitter spreads the power spectrum across a fundamental frequency and multiple harmonics, with each frequency component carrying a portion of the total power. This segmentation reduces the energy concentration at any single frequency, thereby reducing EMI and radiation while maintaining overall power transfer capability at effective frequencies above 150 kHz.
Solution Approach 2:
The patent changes the frequency parameter from a single fixed value to a distributed multi-frequency spectrum. By introducing frequency dithering that modulates the operating frequency around a fundamental value and its harmonics, the system transforms the electromagnetic radiation profile. This parameter change ensures that while the center of gravity of the power spectrum can be above 150 kHz, the actual radiated energy at any specific frequency is reduced, complying with emission standards.
2Device complexity
If single-frequency operation is used to simplify transmitter design, then device complexity is reduced, but electromagnetic radiation and EMI increase
Solution Approach 1:
The patent implements periodic frequency modulation known as frequency dithering, where the operating frequency is continuously modulated to sweep across the fundamental frequency and its harmonics. This periodic action creates a time-varying frequency spectrum that, when averaged, distributes power across multiple frequency components. The periodic nature of this modulation can be implemented using standard modulators and does not require fundamental hardware redesign, thus maintaining relative design simplicity while reducing radiation through frequency spreading.
3Object-generated harmful factors
If multi-frequency operation is implemented to reduce EMI, then electromagnetic interference is reduced, but power balance and efficiency may be affected
Solution Approach 1:
The patent employs feedback mechanisms to monitor and adjust the frequency dithering parameters in real-time. By continuously measuring the actual power transfer efficiency and the distribution of power across frequency components, the system can dynamically adjust the modulation depth and frequency sweep range to optimize both EMI reduction and power balance. This feedback control ensures that power losses are minimized while maintaining the multi-frequency operation benefits.
Solution Approach 2:
The system dynamically changes operating parameters including the fundamental frequency, modulation index, and harmonic content based on load conditions and coupling efficiency. By adapting these parameters in real-time, the transmitter optimizes the distribution of power across frequency components to maintain efficient power transfer. The parameter changes allow the system to shift the power spectrum distribution to match optimal coupling conditions, thereby minimizing energy losses while preserving EMI reduction benefits.
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 effectively reduces undesired emitted radiation, maintains power balance, and ensures compliance with stringent emission standards, even at higher frequencies, without requiring significant hardware redesign.
Implementation Method 1
wireless power transfer techniques are widely used to transfer power from one system to another... using inductive charging
Data Source
AI summary
A method comprises generating a wireless power transmission signal in one or more transmit coils of a wireless power transmitter and, in a multi-frequency operation of the wireless power transmitter, controlling an operating frequency of the wireless power transmission signal to repeatedly switch between a fundamental frequency and one of a lower frequency and an upper frequency in an alternating manner. The lower frequency is offset from the fundamental frequency by a first offset. The upper frequency is offset from the fundamental frequency by a second offset. The second offset is different from the first offset. The first offset associated with the lower frequency and the second offset associated with the upper frequency are to ensure a transmit power in the multi-frequency operation is substantially the same as a transmit power at the fundamental frequency.