Shared Inverter Control for Multi-Coil Induction Heating Noise
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Solution Overview
Problem
Induction heating apparatuses with multiple working coils face increased circuit design complexity and manufacturing costs due to the use of multiple switching elements, and interference noise occurs when multiple coils are driven simultaneously, causing user discomfort.
Innovation Solution
The induction heating apparatus employs a configuration where switching elements are shared between two working coils, allowing for half-bridge or full-bridge modes based on power requirements, and a controller adjusts frequencies to minimize interference noise by coupling or separating the driving frequencies of the coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple full-bridge inverter circuits are used to drive multiple working coils, then each coil can be driven independently with full power, but the number of switching elements increases, leading to increased circuit design complexity and manufacturing cost
Solution Approach 1:
The patent merges two full-bridge inverter circuits into a single three-phase inverter circuit, where six switching elements share common connection points to drive three working coils. This consolidation reduces the total switching element count from eight (in two independent full-bridge circuits) to six, thereby reducing circuit design complexity and manufacturing cost while maintaining the ability to independently control power delivery to each coil through phase-specific switching patterns
Solution Approach 2:
The three-phase inverter circuit is designed with universal functionality to drive multiple working coils simultaneously or independently. The six switching elements can operate in various configurations (e.g., two coils in parallel, three coils in star connection) to provide full power delivery capability across different operating modes, making the circuit adaptable to multiple power requirements without needing separate dedicated circuits for each coil
2Productivity
If multiple working coils are driven simultaneously at different frequencies, then each coil can operate at its optimal frequency for heating efficiency, but interference noise is generated when the frequency difference falls within the audible range
Solution Approach 1:
The controller dynamically adjusts the driving frequencies of multiple working coils based on their respective heating requirements. By changing frequency parameters in real-time, the system can optimize heating efficiency for each coil while avoiding frequency differences that fall within the audible range (20Hz-20kHz), thereby minimizing interference noise generation
Solution Approach 2:
The controller monitors the operating frequencies of multiple working coils and adjusts them to maintain optimal heating performance while preventing audible interference. When frequency differences approach the audible range, the controller provides feedback to modify frequency settings, ensuring both high productivity and low noise operation
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 approach reduces circuit complexity and manufacturing costs while effectively minimizing interference noise, ensuring efficient and comfortable operation.
Implementation Method 1
an induction magnetic field may be generated around the working coil disposed in the induction heating apparatus. When a magnetic force line of the induced magnetic field generated in this way passes through the bottom of the container having a metal component placed on the working coil, an eddy current may be generated inside the bottom of the container
Implementation Method 2
an eddy current may be generated inside the bottom of the container. When the eddy current generated in this way flows through the container, the container itself may be heated
Data Source
AI summary
An induction heating apparatus may include a first working coil provided in a position corresponding to a first heating region, a second working coil provided in a position corresponding to a second heating region, an inverter circuit configured to supply current for driving at least one of the first working coil or the second working coil and comprising a plurality of switching elements, and a drive circuit configured to supply a switching signal to each of the switching elements. A controller configured to determine a driving mode of the working coil when a heating start command for at least one of the first working coil or the second working coil is input, and to supply a control signal for outputting of the switching signal to the drive circuit based on the determined driving mode.