Induction Cooktop Power Control via Discrete Frequency Selection
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Solution Overview
Problem
Existing power control processes for induction cooking devices face challenges in varying induced power in containers without generating electromagnetic compatibility issues or parasitic noises, particularly in matrix cooking tables where inductors are arranged in a two-dimensional distribution and must be controlled simultaneously.
Innovation Solution
A power control process that selects a frequency from a predefined set and adjusts the cyclic ratio of the periodic control signal to achieve the desired induced power, reducing the risk of resonance and electromagnetic disturbances, and allowing simultaneous operation of multiple inductors without noise or whistling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the frequency of the periodic control signal is varied to control power, then power control is achieved, but electromagnetic compatibility issues occur
Solution Approach 1:
The patent applies parameter changes by switching between discrete frequency values from a predefined set rather than continuous frequency variation. This allows power control while avoiding electromagnetic compatibility issues by selecting frequencies that are known to be safe for the specific application context.
Solution Approach 2:
The continuous frequency range is segmented into discrete predefined frequency values. This segmentation allows the system to select from specific safe frequencies rather than sweeping through the entire frequency spectrum, thereby controlling power while avoiding EMC problems.
2Power
If a wide frequency range is used for power control, then power variation is achieved, but parasitic noises appear
Solution Approach 1:
The system uses discrete frequency values from a predefined set to control power, which limits the frequency range to only those values that have been verified to produce acceptable noise levels. This maintains power variation capability while preventing parasitic noises.
Solution Approach 2:
The patent performs preliminary action by pre-defining a set of safe frequency values before operation. These frequencies are selected in advance to avoid generating parasitic noises, and the system only uses these pre-validated frequencies during operation.
3Power
If the duty cycle is varied at a given frequency to control power, then power control is achieved, but the induced power is lower than maximum
Solution Approach 1:
The system changes the frequency parameter rather than relying solely on duty cycle variation to achieve power control. By switching between discrete frequency values, the system can achieve full power output at each frequency while maintaining energy efficiency, avoiding the energy loss associated with prolonged duty cycle variation.
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 enables efficient power control in induction cooking devices by varying power within a defined range using predefined frequencies and cyclic ratios, ensuring compliance with electromagnetic compatibility standards and reducing the risk of resonance and noise, particularly in matrix cooking configurations.
Implementation Method 1
An alternating current is thus generated by the inverter power supply device and flows through the inductor(s). An induced current is then generated in a container placed above this inductor
Implementation Method 2
the container itself heating up by Joule effect due to its resistance
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
A method for power-controlling at least one inductor (L) covered by a container and supplied with alternating current by an inverter power supply (20) controlled by a periodic control signal comprises the following steps: - selecting a frequency for the periodic control signal from a set of N predefined frequency values, N being equal to or greater than two; and - adjusting the duty cycle of the periodic control signal to the selected frequency to obtain induced power in the container. This method is suitable for use in induction cooktops, particularly those without a predefined cooking zone in the cooktop surface.