Induction Heating Inverter Duty Control Stability
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Solution Overview
Problem
Conventional induction heating apparatuses face challenges in achieving desired heating outputs due to limit control, leading to unstable heating control and insufficient cooking performance in automatic heating modes, especially when duty control results in higher maximum heating outputs than continuous heating control.
Innovation Solution
The apparatus employs a control unit that alternates between duty control and continuous control for the inverter circuits, inhibiting duty control in automatic heating modes to maintain stable heating outputs, allowing only one inverter circuit to operate under continuous control when necessary, thus avoiding output limitations and ensuring safety and usability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If duty control is used to operate two inverter circuits simultaneously, then the maximum heating output is increased, but the heating output is limited by limit control in automatic heating mode, causing unstable heating control and insufficient cooking performance
Solution Approach 1:
The patent applies periodic action by implementing duty control that alternates between ON periods (semiconductor switches driven in predetermined switching cycle) and OFF periods (semiconductor switches turned off), where the duty cycle is controlled to achieve desired average heating output. This periodic operation allows the system to achieve high maximum heating output during ON periods while maintaining stable average heating output through controlled duty cycle, thereby resolving the contradiction between maximum power and heating control stability.
2Power
If duty control is used to achieve desired average heating output, then the heating output during ON period must be larger than desired, but this increases the possibility of limit control activation
Solution Approach 1:
The patent implements feedback control by using current detection means to detect input current from the alternating-current power supply, and the control means adjusts the duty cycle of semiconductor switches based on the detection result. This closed-loop feedback mechanism allows the system to accurately control the average heating output by dynamically adjusting the duty cycle according to actual current consumption, thereby achieving precise heating control without excessive power output that would trigger limit control.
3Reliability
If limit control is activated to prevent inverter circuit failure, then the heating output is restricted, but this makes it impossible to achieve predetermined heating output in automatic heating mode
Solution Approach 1:
The patent applies dynamics by making the heating output dynamically adjustable through duty cycle control. The control means dynamically adjusts the duty cycle of semiconductor switches based on detected input current, allowing the system to operate at high power levels during ON periods while maintaining average power within safe limits. This dynamic control enables the system to achieve predetermined heating outputs in automatic heating mode without triggering limit control, thereby maintaining both inverter circuit safety and cooking performance.
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 achieving predetermined heating outputs at lower maximum heating levels than duty control, preventing unstable heating and improving safety and usability by avoiding output limitations, thereby ensuring effective cooking performance in automatic heating modes.
Implementation Method 1
a first inverter circuit converting output power from the rectifier circuit, to high-frequency power, and supplying a current to a first heating coil; a second inverter circuit converting output power from the rectifier circuit, to high-frequency power, and supplying a current to a second heating coil
Implementation Method 2
an induction heating apparatus provided with two inverter circuits, and more particularly, an induction heating apparatus performing duty control in which, when two inverter circuits simultaneously operate for heating
Data Source
Figure 1
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AI summary
When the control unit (8) makes both the first and second inverter circuits (3, 4) operational, the control unit (8) controls the first and second inverter circuits (3, 4) by duty control such that an average heating output from the first inverter circuit (3) reaches a predetermined first target heating output, and an average heating output from the second inverter circuit (4) reaches a predetermined second target heating output. When the control unit (8) makes one of the first and second inverter circuits (3, 4) operational in an automatic heating mode for automatic heating control according to a predetermined heating output sequence, the control unit (8) inhibits the first and second inverter circuits (3, 4) from being controlled by the duty control.