Induction Heating Circuit for E-Cigarettes With Class-D Resonance
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Solution Overview
Problem
Conventional electromagnetic induction heating apparatuses for electronic cigarettes, particularly those using class-E power amplifiers, face challenges with high drain-to-source peak voltage requirements, leading to increased costs and difficulties in implementation, as well as low power utilization factors, making them inefficient for applications with limited voltage and current sources.
Innovation Solution
The proposed solution involves an electromagnetic induction heating apparatus with a current mode class-D power amplifier using a pair of transistor switches and an LC resonant network, which includes choke inductors and a driving unit that estimates temperature changes by calculating resistance value changes, allowing for adaptive control of the heating temperature and improved power utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If class-E power amplifier is used for electromagnetic induction heating, then heating rapidity is improved, but power utilization factor deteriorates and manufacturing difficulty increases
Solution Approach 1:
The patent changes the operating parameters of the power amplifier from class-E to class-D, which fundamentally alters the switching characteristics and voltage-current timing relationship. This parameter change improves power utilization factor while maintaining heating rapidity through optimized resonant circuit design
2Speed
If class-E power amplifier is used for electromagnetic induction heating, then heating rapidity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent simplifies the device by changing from class-E to class-D power amplifier architecture, which requires fewer high-voltage components and simpler switching circuitry. This parameter change reduces manufacturing difficulty while maintaining fast heating performance through resonant coupling optimization
3Power
If high drain-to-source peak voltage is used in power amplifier, then heating power is improved, but cost and implementation difficulty increase
Solution Approach 1:
The patent employs periodic switching action in class-D power amplifier with resonant oscillation, which delivers high instantaneous power through controlled voltage pulses rather than sustained high voltage. This periodic action reduces component voltage ratings and implementation difficulty while maintaining effective heating power through resonant energy transfer
4Weight of moving object
If limited voltage and current sources are used in electronic cigarette, then portability is improved, but heating efficiency deteriorates
Solution Approach 1:
The patent changes the power amplifier class from E to D, which improves power utilization factor and makes the system more compatible with limited battery capacity. This parameter change enables efficient heating with portable power sources by optimizing the voltage-current timing relationship in the resonant circuit
Solution Approach 2:
The patent incorporates temperature sensing and control circuitry that monitors heating efficiency and adjusts power amplifier operation accordingly. This feedback mechanism ensures optimal power utilization from limited battery sources while maintaining effective heating 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 configuration reduces manufacturing complexity, lowers the peak voltage and current requirements, and significantly enhances the power utilization factor, making it more suitable for electronic cigarettes by achieving a power utilization factor approximately 3.24 times higher than class-E power amplifiers, thus improving usability with limited power sources.
Implementation Method 1
an AC magnetic field is generated in an LC-type resonant network including an inductor to raise the temperature of the metal heat-generating body
Implementation Method 2
electromagnetic inductive heating method using heat generation characteristics corresponding to power loss by generating eddy currents
Implementation Method 3
heating the aerosol-forming article to a temperature at which volatile components can be released by directly contacting the aerosol-forming article with the metal heat-generating body
Data Source
AI summary
An electromagnetic induction heating apparatus for heating an aerosol-forming article of an electronic cigarette includes: a power supply unit configured to supply DC power; a power amplifier including a switch unit composed of a pair of transistor switches having a differential structure and operating by receiving the DC power from the power supply unit, and a LC resonant network composed of a resonant inductor connected to an output terminal of the switch unit and electromagnetically inductively coupled with an inductor component of a heat-generating body for heating the aerosol-forming article of the electronic cigarette and a resonant capacitor connected in parallel to the resonant inductor; and a driving unit configured to adjust an operation of the power amplifier to adjust a temperature of the heat-generating body.