Power Conversion Device Carrier Frequency Noise Reduction
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Solution Overview
Problem
Existing electric power conversion devices do not effectively reduce noise perceived by humans, as the intensity of noise felt by humans is not considered in current frequency distribution characteristics, despite flat frequency distribution characteristics improving quietness.
Innovation Solution
An electric power conversion device with a carrier frequency setting unit that switches and restricts carrier frequencies within a predetermined range to generate a PMW output signal, reducing noise by controlling carrier frequencies to minimize audibility in the 2.9 kHz to 3.6 kHz range, where human hearing is most sensitive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If carrier frequency is set to achieve flat frequency distribution characteristic, then noise uniformity is improved, but human perceived noise is not reduced because human audibility is not considered
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the carrier frequency based on human audibility characteristics. Specifically, the system varies the carrier frequency within a range (e.g., 2.0-6.0 kHz) while avoiding the 2.9-3.6 kHz range where human hearing is most sensitive, thereby reducing perceived noise while maintaining operational effectiveness
Solution Approach 2:
The patent implements dynamics by making the carrier frequency variable rather than fixed. The control device dynamically switches between multiple carrier frequencies based on operation conditions and human audibility characteristics, transforming a static frequency system into a dynamic one that adapts to reduce perceived noise
2Object-affected harmful factors
If carrier frequency is varied to reduce noise in sensitive ranges, then human perceived noise is reduced, but frequency distribution characteristic becomes non-flat
Solution Approach 1:
The patent accepts the trade-off of non-flat frequency distribution as necessary to achieve the primary goal of reducing human perceived noise. The carrier frequency is deliberately varied within specific ranges to avoid sensitive human hearing frequencies, prioritizing perceived noise reduction over frequency uniformity
3Object-affected harmful factors
If multiple carrier frequencies are switched for noise reduction, then perceived noise is reduced, but device complexity increases
Solution Approach 1:
The patent manages device complexity by implementing a dynamic frequency switching mechanism controlled by a microcomputer-based control device. The system dynamically selects and switches between multiple carrier frequencies based on operation conditions and human audibility characteristics, balancing noise reduction effectiveness with acceptable system complexity
Solution Approach 2:
The patent reduces perceived noise through parameter changes in carrier frequency while managing complexity by establishing predetermined frequency ranges and switching strategies. The control device varies carrier frequency within defined boundaries (e.g., 2.0-6.0 kHz, avoiding 2.9-3.6 kHz), providing structured noise reduction without excessive complexity
Data Source
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AI summary
In order to provide noise reduction that takes into consideration the noise levels felt by people, by using a method for reducing output current noise in a power conversion device, this power conversion device comprises: a carrier frequency setting unit that switches a plurality of carrier frequencies; a carrier frequency limiting unit that limits a prescribed range of carrier frequencies; a carrier frequency generation unit that generates a carrier frequency used in PMW generation, from the carrier frequency setting unit and the carrier frequency limiting unit; a PMW generation unit that generates PMW output signals using the carrier frequency generated by the carrier frequency generation unit; and an AC conversion unit that outputs AC voltage using the PMW output signals. As a result, a power conversion device is provided that is capable of reducing the noise felt by people.