Working Coil Frequency Coordination for Quieter Induction Heating
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Solution Overview
Problem
Induction heating devices with multiple working coils experience interference noise due to differences in driving frequencies that fall within the human hearing range, affecting normal operation and user comfort.
Innovation Solution
A method of controlling the induction heating device by determining target frequencies for each working coil, adjusting driving frequencies based on reference values, and employing linear or duty control methods to minimize frequency differences and reduce interference noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple working coils are driven at different driving frequencies to meet user-set power requirements, then the output power of each heating area can be independently controlled, but interference noise occurs when the frequency difference falls within the human hearing range
Solution Approach 1:
The patent applies dynamics by making the driving frequency of working coils adjustable rather than fixed. The controller dynamically changes the driving frequency based on operational conditions, allowing the system to adapt between maintaining frequency differences for independent power control and reducing frequency differences to eliminate interference noise within the human hearing range (20Hz-20kHz).
Solution Approach 2:
The patent changes the frequency parameter of the working coils to resolve the contradiction. By adjusting the driving frequency values and their differences, the system can either maintain sufficient frequency separation for independent power control or reduce the frequency difference below the human hearing range to eliminate interference noise, thus addressing both requirements through parameter optimization.
2Productivity
If the driving frequency difference between working coils is maintained within a larger range, then independent power control is improved, but interference noise within the hearing range increases
Solution Approach 1:
The system dynamically adjusts the driving frequency difference based on real-time operational conditions. When interference noise is detected or predicted to occur, the controller modifies the frequency difference to move it outside the human hearing range, while maintaining the ability to provide independent power control through other means such as duty cycle adjustment.
Solution Approach 2:
The patent employs feedback mechanisms where the controller monitors the operational state of multiple working coils and adjusts driving frequencies accordingly. By detecting conditions that would produce interference noise and responding by adjusting frequency parameters, the system maintains heating efficiency while eliminating harmful noise through continuous feedback-based optimization.
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 solution effectively reduces interference noise while ensuring the output power of working coils meets user-set requirements, enhancing the operational performance and user experience of induction heating devices.
Implementation Method 1
a predetermined magnitude of high-frequency voltage is applied to the working coils and thus, magnetic fields are induced around the working coils
Implementation Method 2
The magnetic field lines of the induced magnetic field pass through the metal bottom of the vessel on the working coils and eddy currents are produced inside the vessel bottom
Implementation Method 3
The flow of the eddy currents heats the vessel
Data Source
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AI summary
According to an embodiment, a method of controlling an induction heating device comprises determining a first target frequency of a first working coil corresponding to a driving command for the first working coil, determining a second target frequency of a second working coil corresponding to a driving command for the second working coil, determining a final driving frequency of the first working coil and a final driving frequency of the second working coil based on the first target frequency and the second target frequency, determining output control methods of the first working coil and the second working coil based on the first target frequency, the second target frequency, the final driving frequency of the first working coil, and the final driving frequency of the second working coil, and driving the first working coil and the second working coil at the final driving frequencies according to the output control methods.