Induction Inverter Control for Low-Power Heating Stability
Solution Overview
Problem
Induction heating apparatuses face challenges in accurately matching actual power values to user-set requirements at low power levels, leading to noise generation and potential overheating of switching elements due to on/off control methods.
Innovation Solution
The apparatus employs a controller to switch between full bridge and half bridge operation modes of the inverter circuit based on the required power value, adjusting the duty ratio of switching signals to maintain a stable power output and reduce noise by using a target frequency that is less than the resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If on/off control method is used to reduce power consumption at low power levels, then power saving is improved, but noise is generated and switching elements overheat
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation (PWM) to periodically switch the working coil on and off at a high frequency. This converts the harmful low-frequency on/off control into high-frequency periodic switching, which eliminates audible noise while maintaining efficient power control at low power levels
Solution Approach 2:
The patent uses dynamic control of the duty ratio in PWM signaling to continuously adjust the average power delivered to the working coil. This dynamic adjustment allows precise power control without the noise and overheating issues associated with simple on/off cycling, as the switching occurs at optimized high frequencies
2Use of energy by moving object
If driving frequency is increased to reduce power consumption, then power saving is improved, but switching elements overheat and are burned out
Solution Approach 1:
The patent changes the driving frequency parameter to operate above the resonance frequency of the working coil. This parameter change optimizes the impedance matching and power transfer efficiency, reducing the power losses that cause overheating in switching elements while maintaining low power consumption
3Power
If driving frequency is decreased to increase power output, then power output is improved, but switching elements overheat due to excessive frequency
Solution Approach 1:
The patent employs dynamic PWM control to adjust the duty ratio based on the required power level. This allows the system to deliver high power output when needed while maintaining controlled switching frequencies that prevent overheating, as the duty ratio can be optimized for each operating condition
4Device complexity
If simple on/off control is used to simplify the control system, then device complexity is reduced, but power matching precision deteriorates
Solution Approach 1:
The patent incorporates feedback control by monitoring the actual power delivered to the working coil and adjusting the PWM duty ratio accordingly. This feedback mechanism enables precise power matching to user requirements while maintaining relatively simple control circuitry, as the automated feedback loop handles the complexity of precise control
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 accurate power matching and reduces noise, preventing overheating and ensuring efficient heat delivery even at low power settings.
Implementation Method 1
an induction magnetic field is generated around the working coil disposed in the induction heating apparatus. When a magnetic field line of the generated induction magnetic field passes through a bottom of a metallic container placed over the working coil, eddy current is generated inside the bottom of the container. As the generated eddy current flows through the container, the container itself is heated.
Implementation Method 2
eddy current is generated inside the bottom of the container. As the generated eddy current flows through the container, the container itself is heated.
Implementation Method 3
As the generated eddy current flows through the container, the container itself is heated.
Data Source
AI summary
The present disclosure relates to an induction heating apparatus and a method of controlling the same. A controller of the induction heating apparatus according to the present disclosure may set an operation mode of an inverter circuit to a half bridge mode when a required power value of a working coil is set to a value less than a reference power value such that a driving frequency of the working coil decreases while an actual power value of the working coil is kept the same as the required power value. Additionally, the controller of the induction heating apparatus may adjust a duty ratio of a switching signal input to a switching element included in the inverter circuit, thereby adjusting the actual power value of the working coil.