# US 10,477,894 B2 · Inductive heating device for heating an aerosol-forming substrate

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- Number: US 10,477,894 B2
- Document ID: US10477894B2
- Status: Granted
- Kind: B2
- Application number: 15/121,548
- Filed: 2015-05-21
- Published: 2017-06-22
- Granted: 2019-11-19
- Earliest claimed: 2014-05-21
- Assignees: Philip Morris Products S.A.
- Applicants: Philip Morris Products S.A.
- Inventors: Oleg Mironov
- Web page: https://patentgrep.com/patent/US10477894B2

## CPC

- H05B 6/06: Control, e.g. of temperature, of power
- A24F 40/46: Shape or structure of electric heating means
- A24F 40/465: specially adapted for induction heating
- A24F 40/53: Monitoring, e.g. fault detection
- H03F 3/2176: {Class E amplifiers}
- H05B 1/0244: {Heating of fluids (H05B1/0247 takes precedence)}
- H05B 6/04: Sources of current
- H05B 6/105: {using a susceptor}
- H05B 6/108: {for heating a fluid}
- H05B 6/36: Coil arrangements
- A24F 40/20: Devices using solid inhalable precursors
- H05B 2203/021: Heaters specially adapted for heating liquids
- H05B 2206/02: Induction heating
- H05B 2206/023: using the curie point of the material in which heating current is being generated to control the heating temperature
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- A24F: SMOKERS' REQUISITES; MATCH BOXES; SIMULATED SMOKING DEVICES (inhaling appliances for medical purposes, shaped like cigars, cigarettes or pipes A61M15/06)
- H03F: AMPLIFIERS

## Abstract

An inductive heating device (1) comprises: a device housing (10), a DC power source (11), a power supply electronics (13) comprising a DC/AC inverter (132) including a Class-E power amplifier with a transistor switch (1320), a transistor switch driver circuit (1322), and an LC load network (1323) configured to operate at low ohmic load (1324), the LC load network (1323) comprising a shunt capacitor (C1) and a series connection of a capacitor (C2) and an inductor (L2), and a cavity (14) arranged in the device housing (10), the cavity (14) having an internal surface shaped to accommodate at least a portion of the aerosol-forming substrate (20), wherein the cavity (14) is arranged such that the inductor (L2) is inductively coupled to the susceptor (21) of the aerosol-forming substrate (20) during operation.

## Claims

### Claim 1

Inductive heating device for heating an aerosol-forming substrate comprising a susceptor, the inductive heating device comprising:
a device housing,
a DC power source having a DC supply voltage,
a power supply electronics configured to operate at high frequency in the range of 1 MHz to 30 MHz, the power supply electronics comprising a DC/AC inverter connected to the DC power source, the DC/AC inverter including a power amplifier including a transistor switch, a transistor switch driver circuit, and an LC load network configured to operate at low ohmic load, wherein the LC load network comprises a shunt capacitor and a series connection of a capacitor and an inductor having an ohmic resistance, and
a cavity arranged in the device housing, the cavity having an internal surface shaped to be capable of accommodating at least a portion of the aerosol-forming substrate, the cavity and the inductor of the LC load network being arranged relative to one another such that upon accommodation of the portion of the aerosol-forming substrate in the cavity the inductor of the LC load network is inductively coupled to the susceptor of the aerosol-forming substrate during operation.

### Claim 2 (depends on 1)

Inductive heating device according to claim 1, wherein device is configured for heating an aerosol-forming substrate of a smoking article.

### Claim 3 (depends on 2)

Inductive heating device according to claim 2, wherein the device is configured for heating a tobacco-laden solid aerosol-forming substrate of a smoking article.

### Claim 4 (depends on 3)

Inductive heating device according to claim 3, wherein the power supply electronics further comprises a microcontroller which is programmed to interrupt generation of AC power by the DC/AC inverter as the temperature of the susceptor of the aerosol-forming substrate has exceeded a Curie temperature of the susceptor during operation, and which is programmed to resume generation of AC power as the temperature of the susceptor has cooled down below this Curie temperature again.

### Claim 5 (depends on 1)

Inductive heating device according to claim 1, wherein the DC supply voltage of the DC power source is in the range of about 2.5 Volts to about 4.5 Volts, and wherein the DC supply amperage of the DC power source is in the range of about 2.5 Amperes to about 5 Amperes.

### Claim 6 (depends on 1)

Inductive heating device according to claim 1, wherein the inductor of the LC load network comprises a helically wound cylindrical inductor coil having an oblong shape and defining an inner volume in the range of about 0.15 cm3 to about 1.10 cm3, and wherein the helically wound cylindrical inductor coil is positioned on the internal surface of the cavity or is embedded in the device housing to surround the cavity.

### Claim 7 (depends on 1)

Inductive heating device according to claim 1, wherein the device housing has a substantially cylindrical shape with the cavity being arranged at the proximal end of the device housing and with the DC power source being arranged at the distal end of the device housing, and wherein the power supply electronics is arranged between the DC power source and the cavity.

### Claim 8 (depends on 1)

Inductive heating device according to claim 1, wherein the DC power source comprises a rechargeable DC battery.

### Claim 9 (depends on 1)

Inductive heating device according to claim 1, wherein the power supply electronics further comprises a microcontroller which is programmed to interrupt generation of AC power by the DC/AC inverter as the temperature of the susceptor of the aerosol-forming substrate has exceeded a Curie temperature of the susceptor during operation, and which is programmed to resume generation of AC power as the temperature of the susceptor has cooled down below this Curie temperature again.

### Claim 10 (depends on 1)

Inductive heating device according to claim 1, wherein the power amplifier has an output impedance and wherein the power supply electronics further comprises a matching network for matching the output impedance of the power amplifier to the low ohmic load.

### Claim 11 (depends on 1)

Inductive heating system comprising an inductive heating device according to claim 1 and an aerosol-forming substrate comprising a susceptor, wherein at least a portion of the aerosol-forming substrate is accommodated in the cavity of the inductive heating device such that the inductor of the LC load network of the DC/AC inverter of the inductive heating device is inductively coupled to the susceptor of the aerosol-forming substrate during operation.

### Claim 12 (depends on 11)

Inductive heating system according to claim 11, wherein the aerosol-forming substrate is an aerosol-forming substrate of a smoking article.

### Claim 13 (depends on 12)

Inductive heating system according to claim 12, wherein the aerosol-forming substrate of the smoking article is a tobacco-laden solid aerosol-forming substrate.

### Claim 14 (depends on 1)

Kit comprising an inductive heating device according to claim 1 and an aerosol-forming substrate comprising a susceptor, the inductive heating device and the aerosol-forming substrate being configured such that in operation at least a portion of the aerosol-forming substrate is accommodated in the cavity of the inductive heating device such that the inductor of the LC load network of the DC/AC inverter of the inductive heating device is inductively coupled to the susceptor of the aerosol-forming substrate.

### Claim 15 (depends on 14)

Kit according to claim 14, wherein the aerosol-forming substrate is an aerosol-forming substrate of a smoking article.

### Claim 16 (depends on 15)

Kit according to claim 15, wherein the aerosol-forming substrate of the smoking article is a tobacco-laden solid aerosol-forming substrate.

### Claim 17 (depends on 1)

Inductive heating device according claim 1, wherein the transistor switch comprises a single transistor which is the only transistor in the power amplifier.

### Claim 18 (depends on 17)

Inductive heating device according to claim 17, wherein the power amplifier is configured such that a rise of a voltage of the transistor is delayed until after a current through the transistor has reduced to zero, and that the voltage of the transistor is about zero before the current through the transistor begins to rise.

### Claim 19 (depends on 18)

Inductive heating device according claim 18, wherein the power amplifier is further configured such that a slope of the voltage of the transistor is zero at turn-on time.