Induction Cooktop Phase-Angle Sensing for Small-Pan Detection
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Solution Overview
Problem
Conventional induction cooktops fail to detect small pans accurately, leading to the cooktop control system not activating the inductors, which prevents heating of these pans.
Innovation Solution
A controller system that selectively activates inductors based on a combination of user input and detection of a pan's presence, utilizing a phase angle between the zero-crossing of an induced current and the leading edge of a voltage square wave to identify small pans and adjust power supply accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If automatic pan detection is implemented using conventional methods, then safety is improved by preventing inductor activation without a pan, but small pans are not detected leading to failure to activate inductors
Solution Approach 1:
The system changes the detection parameter from simple presence/absence detection to phase angle measurement. By measuring the phase angle between the drive signal and the current through the inductor, the system can distinguish between no pan present and small pan present conditions, enabling accurate detection across all pan sizes including small pans that were previously undetectable
Solution Approach 2:
The patent replaces conventional pan detection methods (which rely on measuring impedance changes or power consumption) with a phase angle detection method. This substitution allows the system to detect the magnetic properties of the pan more directly through phase measurement, improving sensitivity to small pans while maintaining safety requirements
2Reliability
If the control system uses a fixed detection threshold, then safety requirements are met, but small pans fall below the threshold and are not detected
Solution Approach 1:
The system implements feedback by continuously monitoring the phase angle and using it to adjust the detection decision. The phase angle measurement provides feedback about the magnetic coupling between the inductor and pan, allowing the system to distinguish between safety-critical no-pan conditions and acceptable small-pan conditions that were previously indistinguishable with fixed thresholds
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
Enables the detection and proper heating of small pans, enhancing the versatility and operational efficiency of the induction cooktop by accurately identifying and responding to the presence of pans of various sizes.
Implementation Method 1
inductors comprising coils of copper wire where an oscillating current (e.g. an alternating current) is circulated producing an oscillating electromagnetic field. The electromagnetic field has the main effect of inducing a parasitic current inside the pan
Implementation Method 2
The parasitic current circulating in the pan produces heat by dissipation
Implementation Method 3
The controller is configured to identify the pan presence in response to a phase angle between a zero-crossing of an induced current in the inductor and a leading edge of a square wave of a voltage across an inverter switch
Data Source
AI summary
An induction cooktop includes a ceramic cooking surface in connection with a housing. A plurality of inductors is disposed in the housing and each of the inductors is in communication with an automatic control system. The automatic control system is configured to check for the presence of a cooking pan on the cooktop in order to prevent the inductors from activating in the absence of the cooking pan. The automatic control system is activated upon receiving an activation command.