Multi-Coil Induction Heating Control for Audible Noise Avoidance
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Solution Overview
Problem
Induction heating apparatuses with multiple working coils often generate interference noise due to frequency differences between the coils, which can be inconvenient and lead to user concerns about the apparatus being malfunctioning, and adjusting frequencies randomly to mitigate noise results in mismatched output power values with user-set requirements.
Innovation Solution
The induction heating apparatus includes a controller that adjusts the operation mode or power control mode of the inverter circuits to prevent interference noise by changing the driving frequency of one working coil to a value that ensures the frequency difference with another coil is outside the audible range, using methods such as changing the inverter circuit mode from full bridge to half bridge or adjusting the power control mode to asymmetric pulse width modulation or phase shift, while maintaining the required output power values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the driving frequency of working coils is adjusted to be different to match user-set power values, then the output power value matches the required power value, but interference noise is generated in the audible frequency band
Solution Approach 1:
The patent changes the driving frequency parameter of the working coils to resolve the contradiction. When the calculated frequency difference falls within the audible range (20Hz-20kHz), the controller adjusts at least one working coil's frequency to move the difference outside this range, thereby eliminating audible interference noise while preserving the required power output levels
Solution Approach 2:
The controller continuously monitors the driving frequencies of multiple working coils, calculates their frequency difference, and determines whether this difference falls within the audible frequency band. Based on this feedback, the controller dynamically adjusts the frequency of at least one working coil to prevent audible interference noise while maintaining the required power output
2Object-generated harmful factors
If the driving frequency of working coils is randomly adjusted to reduce interference noise, then the interference noise is reduced, but the output power value does not match the required power value
Solution Approach 1:
The patent implements dynamic frequency adjustment where the controller continuously monitors both the driving frequencies and power output of working coils. When audible interference is detected, the controller dynamically adjusts the frequency of at least one working coil while simultaneously monitoring power output to ensure it remains within the required range, creating a dynamic balance between noise reduction and power maintenance
3Adaptability or versatility
If multiple working coils operate simultaneously at different frequencies, then each heating zone can be controlled independently, but interference noise is generated due to frequency differences in the audible band
Solution Approach 1:
The patent applies local quality by allowing each working coil to operate at its own optimized frequency for independent heating zone control, while simultaneously implementing a global coordination mechanism. The controller monitors the frequency differences between coils and locally adjusts individual coil frequencies when the difference falls within the audible range, thereby maintaining both independent control capability and noise reduction
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 solution effectively prevents interference noise between working coils while ensuring the output power values match user-set requirements, allowing for efficient and reliable operation across various container types with different properties.
Implementation Method 1
When high-frequency current is supplied to the working coil, an induction magnetic field is generated around the working coil disposed in the induction heating apparatus
Implementation Method 2
When a magnetic line of force of the induction magnetic field passes through a bottom of the metallic container over the working coil, eddy current is generated inside the bottom of the container
Implementation Method 3
Accordingly, the eddy current flows in the container, and the container itself is heated
Data Source
AI summary
An induction heating apparatus is configured to determine a third driving frequency corresponding to a third required power value when the required power value of the first working coil or the second working coil is changed to the third required power value, to calculate a difference value between the driving frequency of the working coil (the required power value of which is not changed) and the third driving frequency, to change an operation mode or a power control mode of the first inverter circuit or the second inverter circuit when the difference value is included in a predetermined first reference range, and to change an output power value of the working coil (the required power value of which is changed) to the third required power value.