Induction Coil Frequency Control for Lower EMI and Audible Noise
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Solution Overview
Problem
Induction heating apparatuses generate electromagnetic interference (EMI) and audible noise due to periodic changes in the driving frequency of the working coil, which need to be reduced to comply with electromagnetic compatibility standards and improve user experience.
Innovation Solution
An induction heating apparatus with a controller that adjusts the driving frequency of the working coil randomly or linearly within predetermined limits, using a linear interpolation function, to minimize EMI and noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the driving frequency of the working coil is changed periodically to reduce EMI, then the level of electromagnetic interference decreases, but audible noise is generated during driving
Solution Approach 1:
The patent applies periodic frequency modulation by changing the driving frequency at regular intervals to reduce EMI. The controller periodically adjusts the frequency within a predetermined range, which spreads the electromagnetic energy spectrum and reduces interference levels while maintaining heating effectiveness.
Solution Approach 2:
The patent implements dynamic frequency adjustment where the driving frequency is continuously or periodically varied within an optimal range. This dynamic approach allows the system to adapt the frequency to minimize both EMI and audible noise, rather than using a fixed frequency or simple periodic switching.
2Reliability
If the driving frequency is changed regularly to reduce EMI, then electromagnetic compatibility is improved, but user convenience deteriorates due to noise
Solution Approach 1:
The system dynamically adjusts the driving frequency within an optimal range to simultaneously achieve good electromagnetic compatibility and minimize audible noise. The controller monitors and adjusts frequency in real-time to maintain both regulatory compliance and user comfort.
Solution Approach 2:
The patent changes the operating parameters (frequency) within an optimal range to balance EMI reduction and noise minimization. By adjusting the frequency parameter dynamically rather than using fixed periodic changes, the system maintains electromagnetic compatibility while preserving user convenience.
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 proposed method effectively reduces EMI and noise levels, ensuring compliance with electromagnetic compatibility standards and enhancing user satisfaction.
Implementation Method 1
an inverter circuit (204) comprising a plurality of switching elements and being configured to supply current to the working coil
Implementation Method 2
an induction magnetic field is generated around the working coil disposed in the induction heating apparatus. As the magnetic line of force of the generated induction magnetic field passes through the bottom of the container including a metallic ingredient provided on the working coil, eddy current is generated inside the bottom of the container
Implementation Method 3
eddy current is generated inside the bottom of the container. As the generated eddy current flows in the container, the container itself is heated
Implementation Method 4
As the generated eddy current flows in the container, the container itself is heated
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
In one embodiment, a controller of an induction heating apparatus receives a power level input for a heating area, determines a required power value corresponding to the power level, determines a heating frequency corresponding to the required power value, sets a driving frequency of the working coil to an initial frequency determined based on the heating frequency and drives the working coil, and changes the driving frequency from a current driving frequency to a target frequency based on a predetermined frequency change cycle.