Induction Cooktop Inverter Switch Current Peak Control
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Solution Overview
Problem
Existing induction cooking appliances face challenges in determining the minimum continuous power that can be induced in a container, leading to uneven heating and high noise levels due to the division of power supply over time, which is not user-friendly and generates operational noise.
Innovation Solution
A method and device that measure the current flowing in the switch and freewheel diode, varying the switching frequency to select a maximum frequency allowing current peaks within safe limits, thereby reducing the minimum continuous power induced in the container.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the minimum continuous power is determined by the conventional method (switching frequency at which freewheel diode current is substantially zero), then the switch is protected from excessive current peaks, but the minimum continuous power is too high (400 W), causing power supply to be divided over time which results in uneven heating and high noise levels
Solution Approach 1:
The patent changes the parameter used to determine minimum continuous power from 'freewheel diode current being substantially zero' to 'switch current peak being below a maximum admissible threshold'. This parameter change allows the system to operate at lower powers (250 W) without causing excessive current peaks in the switch, thereby enabling continuous power supply and uniform heating while maintaining switch protection.
2Reliability
If the minimum continuous power is determined by the conventional method, then the switch is protected from excessive current peaks, but the noise level during operation is high due to power supply division over time
Solution Approach 1:
By changing the determination criterion from freewheel diode current threshold to switch current peak threshold, the system can maintain continuous power supply at lower levels (250 W), eliminating the need to divide power supply over time. This continuous operation significantly reduces the noise generated by the inverter power supply device.
3Power
If the switching frequency is increased to reduce minimum continuous power, then the minimum continuous power decreases, but the current peak in the switch increases
Solution Approach 1:
The patent implements a feedback mechanism where the switching frequency is adjusted based on the measured switch current peak. The control method varies the switching frequency within a frequency range and selects the maximum frequency when the current peak reaches but does not exceed the maximum admissible threshold. This feedback control allows the system to operate at the optimal switching frequency that achieves minimum continuous power (250 W) while keeping the current peak within safe limits.
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 lowers the minimum continuous power, allowing continuous power supply at lower setpoint values, reducing noise and providing more consistent heating, with the minimum continuous power being lower than conventional methods, typically around 250 W compared to 400 W.
Implementation Method 1
induction means integrated into a resonant circuit powered by an inverter power supply device
Implementation Method 2
minimum continuous power induced in a container
Data Source
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AI summary
The method involves measuring current (i) circulating in a switch e.g. insulated gate bipolar transistor type switch, and a free wheel diode. A switching frequency is varied in a range of predetermined frequencies. The maximum switching frequency is selected when the value of the current measured at the beginning of switching period of the switch is equal to a predetermined maximum threshold value, where the predetermined maximum threshold value is strictly positive and higher than or equal to 10 A. An independent claim is also included for a device for determining continuous minimum power induced in a container associated with an induction unit, comprising a measurement unit.