Power Conversion Device Random Carrier Frequency Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion devices using PWM signals face challenges in reducing electromagnetic noise due to the increase in average frequency components when multiple carrier frequencies are switched, leading to difficulties in achieving a flat frequency spectrum distribution and potentially causing mechanical resonance.
Innovation Solution
A power conversion device that includes a carrier generating unit, a setting unit, and a PWM signal generating unit, where the carrier frequency is randomly changed based on a pseudo-random number to minimize the average frequency component, allowing for a wider dispersion of harmonic components and reducing electromagnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If multiple carrier frequencies are switched to reduce electromagnetic noise, then the frequency spectrum distribution becomes flatter, but the average frequency component increases causing mechanical resonance
Solution Approach 1:
The patent changes the parameter of carrier frequency from a fixed value to a randomly selected value from multiple predefined frequencies. By using a random number generator to select carrier frequencies dynamically, the system achieves a flatter frequency spectrum distribution while avoiding the deterministic average frequency component that causes mechanical resonance. This parameter change transforms the frequency selection from a regular pattern to a stochastic process.
2Object-generated harmful factors
If the carrier frequency is changed frequently to distribute harmonic components, then the frequency spectrum becomes flatter, but the average frequency component increases making it difficult to avoid mechanical resonance
Solution Approach 1:
The patent introduces dynamic behavior to the carrier frequency selection process. Instead of using a static or regularly switching frequency, the system dynamically selects carrier frequencies based on random numbers generated at each switching event. This dynamic random selection distributes harmonic components across a wider frequency range while preventing the formation of a dominant average frequency component that would trigger mechanical resonance.
3Object-generated harmful factors
If overlapping high-frequency voltages are switched to reduce electromagnetic noise, then noise is reduced, but the average frequency component increases
Solution Approach 1:
The patent applies parameter changes to both the carrier frequency and the overlapping high-frequency voltage parameters. By randomly selecting from multiple predefined frequencies for both the carrier signal and the overlapping high-frequency voltages, the system achieves better frequency spectrum flatness while maintaining noise reduction. This coordinated random parameter selection prevents the average frequency component from dominating the frequency spectrum.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A setting unit of a power conversion device according to an embodiment sets a continuation time to be random and sets one carrier frequency among a plurality of mutually-different carrier frequencies as a set carrier frequency. Accordingly, a carrier generating unit generates a carrier of the particular set carrier frequency during a certain continuation time. Then, a PWM signal generating unit generates a PWM signal based on the carrier generated by the carrier generating unit, and a power conversion unit executes a power conversion based on the generated PWM signal and supplies converted power to a load.