Induction Cooker Coil Control for Interference Noise Reduction
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Solution Overview
Problem
Conventional induction heating cookers require precise placement of containers on the cooking plate to ensure effective cooking, and when containers are placed off-center, interference noise occurs due to differences in operating frequencies and occupation areas of heating coils, affecting the output currents and cooking efficiency.
Innovation Solution
A control method that adjusts the duty ratios of pulse width modulation signals applied to heating coils to ensure equal operating frequencies and target output currents, regardless of the container's position and power level, and implements time division control for coils with different power levels to prevent interference noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple heating coils are operated simultaneously with different power levels, then different power levels can be applied to different containers, but interference noise is generated due to frequency differences
Solution Approach 1:
The patent implements time-division control where heating coils are activated in periodic intervals rather than simultaneously. The control unit divides the operation into multiple time periods, activating each heating coil sequentially with equal frequency. This periodic activation eliminates frequency differences between coils while maintaining the ability to apply different power levels through duty cycle control, thus resolving the interference noise issue.
Solution Approach 2:
The patent merges the operation of multiple heating coils by synchronizing their operating frequencies. Instead of allowing each coil to operate at independent frequencies, the control unit unifies their frequency to be equal, combining their operational characteristics. This frequency unification eliminates the interference caused by frequency differences while still allowing power level variations through pulse width modulation.
2Manufacturing precision
If duty ratios are adjusted to match occupation areas of heating coils, then output currents can be converged to target range, but interference noise is generated due to different operating frequencies
Solution Approach 1:
The patent applies periodic action by controlling each heating coil to operate at the same frequency through time-division multiplexing. The control unit generates pulse width modulation signals with equal frequencies for all heating coils, activating them in sequential time periods. This approach maintains precise output current control through duty ratio adjustment while eliminating frequency-based interference noise.
3Device complexity
If a single high-frequency power supply is used for multiple heating coils, then device complexity is reduced, but power levels cannot be independently controlled for each coil
Solution Approach 1:
The patent segments the control of the single high-frequency power supply by dividing it into multiple independent control channels. The control unit separately adjusts the duty ratios of pulse width modulation signals for each heating coil, enabling independent power level control. This segmentation allows one power supply to function as multiple independent power sources, maintaining low device complexity while achieving versatile power control.
Solution Approach 2:
The patent introduces dynamic control through pulse width modulation, where the duty ratios of the single power supply's output signals are dynamically adjusted for each heating coil. This dynamic adjustment enables flexible power level control for each coil while using a single static power supply unit, resolving the contradiction between simplicity and adaptability.
4Ease of operation
If containers are placed off-center on the cooking plate, then user convenience is improved, but interference noise occurs due to unequal occupation areas of heating coils
Solution Approach 1:
The patent uses periodic action with equal frequency operation for all heating coils to eliminate interference noise that would otherwise result from off-center container placement. By controlling each coil to operate at the same frequency through time-division control, the system maintains frequency synchronization even when containers occupy unequal areas of different coils, thus allowing flexible placement without noise issues.
Solution Approach 2:
The patent changes the operating parameter of frequency to be equal across all heating coils, regardless of their occupation areas. The control unit adjusts duty ratios to compensate for area differences while maintaining equal frequencies, thereby eliminating interference noise. This parameter standardization allows users to place containers flexibly without causing frequency-based interference.
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 method ensures effective cooking regardless of container position, reduces interference noise, and improves heating efficiency by maintaining output currents within the target range, even when containers occupy multiple coils or have different power levels.
Implementation Method 1
supplies high-frequency current to heating coils to generate a strong high-frequency magnetic field and generates eddy current on containers magnetically connected to the heating coils through the magnetic field
Implementation Method 2
generates eddy current on containers magnetically connected to the heating coils through the magnetic field
Implementation Method 3
cook foods using Joule's heat due to the eddy current
Data Source
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AI summary
Disclosed herein is a control method of an induction heating cooker including detecting at least one heating coil occupied by a first container from among a plurality of heating coils, switching a plurality of inverter units so that a power level input by a user is applied to the detected at least one heating coil, determining, if the at least one heating coil occupied by the first container includes plural heating coils, whether or not output currents within a target output current range corresponding to the power level are present from among the output currents of the respective heating coils sensed by sensing units, and equally adjusting duty ratios of pulse width modulation signals applied to the inverter units of the respective heating coils until at least one of the output currents reaches the target output current range, if no output current within the target output current range is present.