Dual-Coil Induction Heating Frequency Control for Noise Prevention
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Solution Overview
Problem
Induction heating apparatuses with multiple working coils can generate interference noise due to differences in driving frequencies, leading to user inconvenience and potential misinterpretation of the apparatus being faulty.
Innovation Solution
The induction heating apparatus employs a controller that adjusts the operation mode of the inverter circuit from a full bridge mode to a frequency doubler mode when the difference in driving frequencies between working coils falls within a specific audible frequency range, thereby preventing interference noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the driving frequency of working coils is adjusted to match user-required power values, then the output power value matches the required power value, but interference noise is generated when the frequency difference falls within the audible range
Solution Approach 1:
The controller proactively detects when the frequency difference between working coils falls within the audible range (2kHz-20kHz) and preemptively adjusts at least one driving frequency to move the difference outside this range, preventing interference noise before it occurs while maintaining the required power output
Solution Approach 2:
The controller modifies the driving frequency parameter of at least one working coil when the frequency difference is detected to be within the audible range, changing the frequency parameter to eliminate the harmful noise while preserving the power output relationship
2Object-generated harmful factors
If the driving frequency is randomly adjusted to move the frequency difference out of the audible range, then interference noise is reduced, but the output power value no longer matches the required power value
Solution Approach 1:
The controller continuously monitors both the driving frequencies and the power output of working coils, using feedback loops to make coordinated adjustments that simultaneously maintain frequency differences outside the audible range and preserve the required power output values through dynamic compensation
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 while maintaining the output power values and required power values of the working coils, ensuring reliable operation and user satisfaction.
Implementation Method 1
An induction magnetic field is then generated around the working coil disposed in the induction heating apparatus. 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 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. Accordingly, the eddy current flows in the container, and the container itself is heated.
Data Source
AI summary
An induction heating apparatus may include first/second working coils, first/second inverter circuits, and a controller. When a user changes a required power value of a first working coil or a second working coil to a third required power value, a controller determines a third driving frequency corresponding to the third required power value. The controller calculates a difference value between a driving frequency of the working coil, the required power value of which is not changed, and the third driving frequency, and compares the calculated difference value with a first reference range. When the calculated difference value is included in the first reference range, the controller changes an operation mode of a first inverter circuit from a full bridge mode to a frequency doubler mode, and changes an output power value of the working coil, the required power value of which is changed to the third required power value.