Induction Cooktop Control for Continuous Power Updates
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Solution Overview
Problem
Existing induction cooktops face challenges in continuously updating power characteristics during cooking due to external factors like cookware temperature and position, leading to power fluctuations and interruptions in power delivery, as frequent frequency scans are required to adjust for these changes.
Innovation Solution
The induction cooktop employs a control unit with power detectors and switching current generators that continuously sense and adjust power delivery by operating induction heaters at different switching frequencies in distinct control intervals, allowing for continuous updating of power characteristics without disrupting power supply, using a quasi resonant converter configuration for efficient and accurate power control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frequent frequency scans are performed to update power characteristics, then power characteristics can be continuously updated to adapt to changing conditions, but power delivery is disrupted and interruptions occur
Solution Approach 1:
The control period is divided into multiple control intervals, where in each interval only one induction heater is energized. This segmentation allows the system to update power characteristics for each heater independently without disrupting the overall power delivery to all heaters simultaneously.
Solution Approach 2:
The system performs preliminary determination of power characteristics at the start of cooking, then uses these characteristics to control the induction heaters during subsequent control intervals. When updates are needed, the system can refresh characteristics without interrupting ongoing cooking operations.
2Measurement precision
If a new frequency scan is carried out to update power characteristics, then power characteristics can be refreshed to reflect current conditions, but power delivery is impaired and flicker emissions increase
Solution Approach 1:
The system performs power characteristic updates periodically at the end of control periods rather than continuously interrupting operation. This periodic refresh approach maintains measurement precision while minimizing the impact on power delivery and reducing flicker emissions during cooking operations.
3Power
If individual induction heaters are controlled at different switching frequencies, then user power demands can be met, but audible noise is generated due to frequency intermodulation
Solution Approach 1:
The system dynamically adjusts switching frequencies based on the specific cooking vessel and power requirements. By optimizing the switching frequency parameter for each heater based on actual load conditions, the system meets user power demands while minimizing frequency intermodulation and associated audible noise.
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 enables frequent and continuous updating of power characteristics without affecting power delivery, reducing audible noise and maintaining consistent power, thus improving the efficiency and quality of the cooking process.
Implementation Method 1
an induction cooktop may comprise at least one pair of high frequency current generators, sharing common mains line, rectifier and DC link and configured to energize respective induction heaters (also referred to as 'pancake coils')
Implementation Method 2
a converter (5), configured to couple to a supply line (7) through a coupling interface (8) to receive an AC supply voltage VAC and to independently energize the induction heaters (3, 4)
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An induction cooktop includes: a first induction heater (3) and a second induction heater (4); a control unit (15); a first switching current generator (17) and a second switching current generator (18), operable by the control unit (15) in subsequent control periods (I0) to energize the first induction heater (3) and the second induction heater (4), respectively. The control unit (15) configured to: operate both the first switching current generator (17) and the second switching current generator (18) with a first switching frequency (fSW1) in a first control interval (I1) of each control period (I0); operate only the first switching current generator (17) with at least two respective different switching frequencies (fSW2, fSW3) in a second control interval (I2) and in a third control interval (I3) of each control period (I0), while the second switching current generator (18) is inactive; operate only the second switching current generator (18) with at least two respective different switching frequencies (fSW4, fSW5) in a fourth control interval (I4) and in a fifth control interval (I5) of each control period (I0), while the first switching current generator (17) is inactive.