Inductive Heating Circuit for Contactless Susceptor Temperature Control
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Solution Overview
Problem
Existing aerosol-delivery systems with inductive heating devices lack a method to efficiently measure and control the operating temperature of the aerosol-forming substrate, as temperature measurement is not directly possible due to contactless heating.
Innovation Solution
An inductive heating device with a DC power source, power supply electronics, and a microcontroller that determines the temperature of the susceptor by calculating apparent ohmic resistance from DC supply voltage and current, allowing for temperature control by interrupting or resuming AC power generation based on preset thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inductive heating is used to heat the aerosol-forming substrate contactlessly, then heating efficiency and device reliability are improved, but temperature measurement capability deteriorates
Solution Approach 1:
The patent introduces an intermediary measurement approach by monitoring the electrical properties (impedance, resistance, or current) of the inductor itself as a mediator to indirectly determine the temperature of the aerosol-forming substrate. The inductor's electrical properties change in response to thermal coupling with the heated substrate, providing temperature information without direct contact measurement.
Solution Approach 2:
The patent replaces the mechanical contact-based temperature measurement system (thermocouples or contact sensors) with an electrical field-based measurement system. By substituting physical contact measurement with electrical property monitoring of the inductor, the system maintains contactless heating while enabling temperature determination through electrical rather than mechanical means.
2Measurement precision
If a heating blade is used to heat the aerosol-forming substrate, then temperature measurement is straightforward through ohmic resistance monitoring, but direct contact causes contamination and reduced reliability
Solution Approach 1:
The patent replaces the mechanical contact heating system (heating blade) with an inductive heating system using electromagnetic fields. This substitution eliminates the need for physical contact between the heating element and the aerosol-forming substrate, preventing contamination while maintaining temperature control through electrical property monitoring of the inductor.
Solution Approach 2:
The inductor serves as an intermediary heating element that transfers energy to the aerosol-forming substrate through electromagnetic induction rather than direct contact. The inductor's electrical properties act as a mediator to provide temperature information about the substrate without requiring physical contact between the measurement system and the substrate.
3Measurement precision
If additional temperature sensors are added to the inductive heating device, then temperature measurement capability is improved, but device complexity and size increase
Solution Approach 1:
The patent makes the inductor multi-functional by using it both for heating the aerosol-forming substrate through electromagnetic induction and for measuring temperature through monitoring its electrical properties. This eliminates the need for separate temperature sensors, reducing device complexity while maintaining contactless operation.
Solution Approach 2:
The patent merges the heating function and temperature measurement function into a single component (the inductor). By combining these two functions that were previously performed by separate components (heating element and temperature sensor), the system reduces complexity and component count while enabling temperature determination through the inductor's electrical property changes.
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 within a few seconds while minimizing power supply size and maintaining a small, robust, and easy-to-handle device.
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, and the aerosol-forming substrate comprises a susceptor. The alternating magnetic field of the inductor generates eddy currents
Implementation Method 4
the power supply electronics comprising a DC/AC converter connected to the DC power source, the DC/AC converter comprising an LC load network configured to operate at low ohmic load
Implementation Method 5
a microcontroller programmed to in operation determine from the DC supply voltage of the DC power source and from the DC current drawn from the DC power source an apparent ohmic resistance
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).