Apparatus for a resonance circuit
Disclosed is a method and apparatus for use with an RLC resonance circuit for inductive heating of a susceptor of an aerosol generating device. The apparatus is arranged to determine a resonant frequency of the RLC resonance circuit; and determine, based on the determined resonant frequency, a first frequency for the RLC resonance circuit for causing the susceptor to be inductively heated, the first frequency being above or below the determined resonant frequency. The apparatus may be arranged to control a drive frequency of the RLC resonance circuit to be at the determined first frequency in order to heat the susceptor. Also disclosed is an aerosol generating device including the apparatus.
1 . An aerosol generating device comprising:
an RLC resonance circuit for inductive heating of a susceptor received in the aerosol generating device in use; and
a controller being arranged to, in use:
determine a resonant frequency of the RLC resonance circuit;
determine, based on the determined resonant frequency, a first frequency for the RLC resonance circuit for causing the susceptor to be inductively heated, the first frequency being above or below the determined resonant frequency; and
control a drive frequency of the RLC resonance circuit to be at the determined first frequency in order to heat the susceptor.
2 . The aerosol generating device according to claim 1 , wherein the first frequency is for causing the susceptor to be inductively heated to a first degree at a given supply voltage, the first degree being less than a second degree, the second degree being that to which the susceptor is caused to be inductively heated, at the given supply voltage, when the RLC circuit is driven at the resonant frequency.
3 . The aerosol generating device according to claim 1 , wherein the controller is arranged to:
control the drive frequency to be held at the first frequency for a first period of time.
4 . The aerosol generating device according to claim 1 , wherein the controller is arranged to: control the drive frequency to be at one of a plurality of first frequencies each different from one another.
5 . The aerosol generating device according to claim 4 , wherein the controller is arranged to: control the drive frequency through the plurality of first frequencies in accordance with a sequence.
6 . The aerosol generating device according claim 5 , wherein the controller is arranged to:
select the sequence from one of a plurality of predefined sequences.
7 . The aerosol generating device according to claim 5 , wherein the controller is arranged to:
control the drive frequency such that each of the first frequencies in the sequence is closer to the resonant frequency than the previous first frequency in the sequence, or
control the drive frequency such that each of the first frequencies in the sequence is further from the resonant frequency than the previous first frequency in the sequence.
8 . The aerosol generating device according to claim 4 , wherein the controller is arranged to:
control the drive frequency to be held at one or more of the plurality of first frequencies for a respective one or more time periods.
9 . The aerosol generating device according to claim 1 , wherein the controller is arranged to:
measure an electrical property of the RLC circuit as a function of the drive frequency; and
determine the resonant frequency of the RLC circuit based on the measurement.
10 . The aerosol generating device according to claim 9 , wherein the controller is arranged to:
determine the first frequency based on the measured electrical property of the RLC circuit as a function of the drive frequency at which the RLC circuit is driven.
11 . The aerosol generating device according to claim 9 , wherein the electrical property is a voltage measured across an inductor of the RLC circuit, the inductor being for energy transfer to the susceptor.
12 . The aerosol generating device according to claim 9 , wherein the measurement of the electrical property is a passive measurement.
13 . The aerosol generating device according to claim 12 , wherein the electrical property is indicative of a current induced in a sense coil, the sense coil being for energy transfer from an inductor of the RLC circuit, the inductor being for energy transfer to the susceptor.
14 . The aerosol generating device according to claim 12 , wherein the electrical property is indicative of a current induced in a pick-up coil, the pick-up coil being for energy transfer from a supply voltage element, the supply voltage element being for supplying voltage to a driving element, the driving element being for driving the RLC circuit.
15 . The aerosol generating device according to claim 1 , wherein the controller is arranged to:
determine the resonant frequency of the RLC circuit or the first frequency on start-up of the aerosol generating device and/or substantially on installation of a new or
replacement susceptor into the aerosol generating device and/or on installation of a new or replacement inductor into the aerosol generating device.
16 . The aerosol generating device according to claim 1 , wherein the controller is arranged to:
determine a characteristic indicative of a bandwidth of a peak of a response of the RLC circuit, the peak corresponding to the resonant frequency; and
determine the first frequency based on the determined characteristic.
17 . The aerosol generating device according to claim 1 , wherein the controller comprises:
a driving element arranged to drive the RLC resonance circuit at one or more of a plurality of frequencies;
wherein the controller is arranged to control the driving element to drive the RLC resonant circuit at the determined first frequency.
18 . The aerosol generating device according to claim 17 , wherein the driving element comprises a H-Bridge driver.
19 . The aerosol generating device according to claim 1 , comprising:
a said susceptor arranged to heat an aerosol generating material thereby to generate an aerosol in use, the susceptor being arranged for inductive heating by the RLC resonance circuit.
20 . The aerosol generating device according to claim 19 , wherein the susceptor comprises one or more of nickel and steel.
21 . The aerosol generating device according to claim 20 , wherein the susceptor comprises a body having a nickel coating.
22 . The aerosol generating device according to claim 21 , wherein the nickel coating is electroplated on to the body.
23 . The aerosol generating device according to claim 20 , wherein the nickel coating has a thickness less than 5 μm, or substantially in the range 2 μm to 3 μm.
24 . The aerosol generating device according to any one of claim 20 , wherein the susceptor is or comprises a sheet of mild steel.
25 . The aerosol generating device according to claim 24 , wherein the sheet of mild steel has a thickness in the range of 10 μm to 50 μm, or has a thickness of 25 μm.
26 . A method of operating an aerosol generating device comprising an RLC resonance circuit for inductive heating of a susceptor received in the aerosol generating device in use, the method comprising:
determining a resonant frequency of the RLC circuit;
determining a first frequency for the RLC resonance circuit for causing the susceptor to be inductively heated, the first frequency being above or below the determined resonant frequency; and
controlling a drive frequency of the RLC resonance circuit to be at the determined first frequency in order to heat the susceptor.
27 . A non-transitory computer-readable storage medium storing a computer program which, when executed on a processing system, causes the processing system to perform the method of claim 26 .