Induction Cooker Inverter Control via Periodic Current Feedback
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Solution Overview
Problem
Conventional induction heating cookers with multiple inverters struggle to accurately control input currents to individual heating coils, leading to variations in input power, which affects cooking performance and user comfort.
Innovation Solution
The induction heating cooker employs a control unit that alternately adjusts the output powers and maintains constant operating frequencies for inverters, using feedback control to manage input currents, even with a single input current detecting circuit, ensuring stable power delivery to multiple heating coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single input current detecting circuit is used to detect the sum of input currents to multiple heating coils, then the device complexity is reduced, but the measurement precision of individual coil currents deteriorates
Solution Approach 1:
The control unit alternately controls the operation of multiple inverters in different operation modes. In each mode, one inverter operates at a time while others are stopped, allowing the single current detecting circuit to measure individual coil currents accurately during each periodic phase, thus resolving the measurement precision issue while maintaining low device complexity
Solution Approach 2:
The system dynamically switches between different operation modes where inverters are alternately activated. This dynamic control allows the single current detecting circuit to sequentially measure currents for different coils by controlling which inverter is active at any given time, transforming a static measurement limitation into a dynamic solution
2Productivity
If multiple inverters operate simultaneously to heat multiple coils, then the productivity is improved, but the control precision of individual input currents deteriorates due to feedback difficulty
Solution Approach 1:
The control unit implements periodic switching between operation modes, alternately activating different inverters. This allows the system to maintain multiple heating coils operational over time while ensuring each inverter receives precise feedback control during its active phase, thus maintaining both productivity and control precision
Solution Approach 2:
The control unit uses the current detected by the input current detecting circuit during each operation mode to provide feedback control for the active inverter. This feedback mechanism ensures precise control of input currents to each heating coil while allowing multiple coils to be heated across different time periods
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 allows for precise control of input currents and powers to each heating coil, reducing power variations and enhancing cooking stability and user comfort, even when multiple inverters operate simultaneously.
Implementation Method 1
a rectifier circuit (2) which rectifies the AC power supply (1)
Implementation Method 2
a smoothing capacitor (3) which smooths an output from the rectifier circuit (2)
Implementation Method 3
a first inverter (11a) which converts an output from the smoothing capacitor (3) into a high-frequency voltage by using a switching element (6a, 6c) to supply a high-frequency power to the first heating coil (4a)
Implementation Method 4
High-frequency magnetic fields are induced by the high-frequency currents in the first and second heating coils (102 and 103)
Implementation Method 5
The applied high-frequency magnetic fields induce an eddy current in the load such as a pot, and the pot is heated by the surface resistance of its own and the eddy current
Data Source
Figure 1
Figure 2(A)~2(D)
Figure 3(A)~3(G)
AI summary
A conventional induction heating cooker which operates two inverters at the same time, with only one input current detecting circuit provided, cannot measure each of input currents to each of the plurality of inverters, and cannot control input powers by feedback control on input currents. In the induction heating cooker which has a plurality of inverters, when the input power varies to the inverter which has less input power supplied, the variation hardly influences the cooking. The induction heating cooker according to the present invention fixes the operating frequency for the inverter which has less input power supplied and performs the feedback control of the input current for the inverter which has bigger input power supplied.