Induction Cooktop Vessel Detection Using Zero-Cross Phase Analysis
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Solution Overview
Problem
Induction heating electric ranges face challenges in determining whether a vessel is magnetic or non-magnetic, leading to inefficient heating and noise issues when a non-magnetic vessel is used.
Innovation Solution
A cooking apparatus with a coil, driver, and controller that gradually increases the duty cycle of a switch to reduce noise and determine the vessel material by analyzing the phase difference between the zero cross point of the current and the turn-on operation of the switch, using multiple operating frequencies to differentiate between heatable and non-heatable vessels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the duty cycle of the switch is increased rapidly to provide high heating power, then the heating efficiency is improved, but noise is generated around the coil
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation (PWM) to control the switch duty cycle. The controller periodically switches the power supply to the coil with varying duty cycles, allowing efficient power transfer while controlling noise through regulated switching patterns rather than continuous high-power delivery.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the duty cycle of the switch based on real-time conditions. The controller modifies the duty cycle ratio of the switch's on-time versus total period, enabling the system to adapt power delivery to minimize noise while maintaining heating efficiency through dynamic control rather than static operation.
2Speed
If the current applied to the coil is increased to improve heating performance, then the heating speed is improved, but noise around the coil increases
Solution Approach 1:
The patent uses periodic action through PWM control to deliver current in controlled pulses rather than continuous high current. This allows the system to achieve fast heating through high peak currents during the on-period while keeping the average current and associated noise levels controlled through the duty cycle ratio.
Solution Approach 2:
The patent applies dynamics by dynamically adjusting the current waveform through switch duty cycle control. The controller modulates the current in real-time, enabling rapid heating when needed while reducing current and noise during other periods, creating a dynamic balance between heating speed and noise generation.
3Loss of time
If the switch operates at high duty cycle from the start to provide immediate heating, then the response time is improved, but vessel material identification accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by performing vessel material detection before initiating full-power heating. The controller first applies a detection signal at a predetermined frequency to identify the vessel material, then uses this information to optimize the subsequent heating process, ensuring both accurate identification and efficient heating response.
Solution Approach 2:
The patent implements segmentation by dividing the operation into distinct phases: a detection phase where the switch operates at a predetermined frequency for material identification, followed by a heating phase where the duty cycle is optimized based on detection results. This segmentation allows both accurate measurement and efficient heating without interference.
4Device complexity
If the duty cycle is kept constant to simplify control, then the device complexity is reduced, but the ability to reduce noise and improve heating efficiency is worsened
Solution Approach 1:
The patent applies feedback by using the detected vessel material information to adjust the switch duty cycle control strategy. The controller receives feedback from the detection phase about vessel properties and uses this to optimize the heating phase parameters, creating a closed-loop system that reduces noise and improves efficiency without requiring complex manual intervention.
Solution Approach 2:
The patent implements self-service through automatic duty cycle adjustment based on detected vessel characteristics. The system automatically adapts its control parameters according to the identified vessel material, eliminating the need for manual setup or complex user input while achieving optimized noise reduction and heating performance through self-adjustment.
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
Effectively identifies vessel material and reduces noise by gradually increasing the current applied to the coil, ensuring efficient heating and minimizing misidentification of vessel types.
Implementation Method 1
a coil configured to place a vessel thereon and generate a magnetic field when a current is applied thereto
Implementation Method 2
compare a phase of a voltage input to the first switch to a phase of the detected current, and determine a material of the vessel
Data Source
AI summary
A cooking apparatus includes a coil configured to generate a magnetic field, a driver including a first switch and a second switch and configured to change a direction of the current, a current detector configured to detect the current of the coil, a controller configured to increase a duty cycle of the first switch during a reference time when an operation start signal is transmitted thereto, control operations of the first switch and the second switch on the basis of an operating frequency when the reference time elapses, check zero cross points of currents detected while the first switch and the second switch are operated, compare a time point of the checked zero cross point to a starting time point of an turn-on operation of the first switch to determine a material of the vessel, and block the applied current when the vessel is determined to be a non-heatable vessel.