Inductive Heating Circuit for Contactless Susceptor Temperature Control
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Solution Overview
Problem
Inductive heating devices for aerosol-forming substrates lack a method to efficiently measure and control the operating temperature of the substrate, as the contactless heating process makes direct temperature measurement impossible.
Innovation Solution
An inductive heating device with a DC power source, power supply electronics including a DC/AC converter with an LC load network, and a microcontroller that determines the temperature of the susceptor by calculating the apparent ohmic resistance from the DC supply voltage and current, allowing for temperature control through AC power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contactless inductive heating is used to heat the aerosol-forming substrate, then the heating efficiency and device reliability are improved, but the ability to measure and control the temperature of the substrate is lost
Solution Approach 1:
The patent introduces an intermediary measurement approach by monitoring the electrical properties (impedance, resistance, or capacitance) of the inductive heating element itself, which changes with temperature. This intermediary measurement allows indirect temperature assessment without direct contact with the heated substrate, thus maintaining both contactless heating and temperature measurement capabilities
Solution Approach 2:
The patent implements feedback control by continuously monitoring the electrical properties of the heating element and using this information to adjust the heating power. The microcontroller processes the measured electrical parameters and modulates the heating element's power consumption to maintain the desired temperature, creating a closed-loop control system that enables precise temperature control without direct contact
2Measurement precision
If a heating blade in direct contact with the aerosol-forming substrate is used, then direct temperature measurement is possible through ohmic resistance monitoring, but the device complexity and potential contamination increase
Solution Approach 1:
The patent replaces the mechanical contact-based heating blade system with a contactless inductive heating system. The electromagnetic field-based heating eliminates the need for physical contact between the heating element and the aerosol-forming substrate, thereby simplifying the device structure while avoiding contamination issues associated with direct contact
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
Enables efficient and precise temperature control of the aerosol-forming substrate, achieving temperatures between 200-400°C in aerosol-delivery systems, with a compact and robust design that minimizes power supply electronics volume.
Implementation Method 1
The alternating magnetic field of the inductor generates eddy currents and hysteresis losses in the susceptor, causing the susceptor to heat the aerosol-forming substrate
Implementation Method 2
The alternating magnetic field of the inductor generates eddy currents and hysteresis losses in the susceptor, causing the susceptor to heat the aerosol-forming substrate
Implementation Method 3
The inductive heating device comprises an inductor arranged in thermal proximity of the aerosol-forming substrate
Implementation Method 4
a DC/AC converter configured to convert the DC supply voltage and the DC current into a high frequency AC power
Data Source
AI summary
An inductive heating device (1) for heating an aerosol-forming substrate (20) comprising a susceptor (21) comprises: a device housing (10), a DC power source (11) for providing a DC supply voltage(VDC) and a DC current (IDC), a power supply electronics (13) comprising a DC/AC converter (132), the DC/AC converter (132) comprising an LC load network (1323) comprising a series connection of a capacitor (C2) and an inductor (L2) having an ohmic resistance (RCoil), a cavity (14) in the device housing (10) for accommodating a portion of the aerosol-forming substrate (20) to inductively couple the inductor (L2) of the LC load network (1323) to the susceptor (21). The power supply electronics (13) further comprises a microcontroller (131) to determine from the DC supply voltage (VDC) and the DC current (IDC) an apparent ohmic resistance (Ra), and from the apparent ohmic resistance (Ra) the temperature (T) of the susceptor (21).