Induction Cooker Control Unit Suppressing Inrush Currents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional induction cookers experience large inrush currents and produce buzzing or rattling noises due to alternating power demands between inverter circuits, causing cookware vibrations and noise.
Innovation Solution
The induction cooker employs a control unit to alternately drive oscillation circuits, maintaining low-power heating on switched-off heating coils during transitions, thereby controlling power variations and reducing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the first inverter circuit is driven at high power (4 kW) during half cycle to achieve average output of 2 kW, then the required power output is improved, but large inrush current occurs when switching from off state causing cookware vibration and noise
Solution Approach 1:
The patent applies preliminary action by maintaining low-power heating on the switched-off heating coil before it needs to be turned off. This preparatory low-power state prevents large inrush currents when the coil is subsequently turned off and restarted, thereby eliminating cookware vibration and noise while still achieving the required average power output through alternating operation of multiple heating coils
Solution Approach 2:
The patent implements continuity of useful action by ensuring that when one heating coil is switched off, another heating coil remains active at low power. This continuous heating action prevents complete cessation of heating, maintaining thermal stability and preventing the large power transitions that cause inrush currents and cookware vibration, while still achieving the desired average power level
2Power
If the second inverter circuit is driven at high power (2 kW) during half cycle to achieve average output of 1 kW, then the required power output is improved, but large inrush current occurs when switching from off state causing cookware vibration and noise
Solution Approach 1:
The patent applies preliminary action by maintaining low-power heating on the switched-off heating coil before it needs to be turned off. This preparatory low-power state prevents large inrush currents when the coil is subsequently turned off and restarted, thereby eliminating cookware vibration and noise while still achieving the required average power output through alternating operation of multiple heating coils
Solution Approach 2:
The patent implements continuity of useful action by ensuring that when one heating coil is switched off, another heating coil remains active at low power. This continuous heating action prevents complete cessation of heating, maintaining thermal stability and preventing the large power transitions that cause inrush currents and cookware vibration, while still achieving the desired average power level
3Adaptability or versatility
If oscillation circuits are driven alternately in each half cycle, then power distribution between multiple heating coils is improved, but input power varies significantly between 4 kW and 2 kW causing instability
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the power level of the switched-off heating coil from high power to low power before switching. This parameter change smooths the transition between alternating heating coils, reducing input power variation from 4 kW to 2 kW to a much smaller range, thereby maintaining power distribution versatility while improving input power stability
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 effectively suppresses inrush currents and noise, providing a quieter cooking experience by maintaining low-power heating during transitions between oscillation circuit operations.
Implementation Method 1
a rectifier circuit (2) which rectifies power supplied from an AC power supply (1)
Implementation Method 2
a smoothing capacitor (3) which smooths a rectified output from the rectifier circuit (2) to produce DC power supply
Implementation Method 3
a first inverter (11a) which has the DC power supply converted to AC by a first switching element (6a, 6c) to supply high-frequency power to a first heating coil (4a)
Implementation Method 4
first and second oscillation circuits (7a, 7b) which supply a driving signal to the first and second switching elements (6a, 6c; 6b, 6d)
Implementation Method 5
supply high-frequency power to a first heating coil (4a)
Implementation Method 6
an induction cooker according to the present invention
Data Source
Figure 1
Figure 2(A)~2(E)
Figure 3
AI summary
An induction cooker comprises: first and second inverters (11a, 11b) each of which is connected in parallel to the smoothing capacitor and has a DC power supply converted to AC by first and second switching elements to supply high-frequency power to first and second heating coils (4a, 4b); first and second oscillation circuits (7a, 7b) which supply a driving signal to the respective first and second switching elements; and a control unit (10) which controls driving of the first and second oscillation circuits. The control unit (10) controls the first and second oscillation circuits by alternately driving the first and second oscillation circuits and causes a switched-off side heating coil of the first and second heating coils to maintain low-power heating without causing the switched-off side heating coil of the first and second heating coils to stop heating each time the control unit switches the first and second oscillation circuits to drive.