An aerosol generating device, and a method for controlling resistance of heating element

Abstract

A method (300) for controlling resistance of a heating element (108) of an aerosol generating device (100) includes providing, by a Pulse Width Modulation (PWM) control unit (206), a Pulse Width Modulation (PWM) signal to the heating element (108) for each activation of the aerosol generating device (100). Further, the method (300) includes performing, by a heater control circuit coupled to the PWM control unit (206), one of: determining a change in resistance of the heating element (108) during an off-duty cycle of the PWM signal, and heating the heating element (108) during an on-duty cycle of the PWM signal.

Description

AN AEROSOL GENERATING DEVICE, AND A METHOD FOR CONTROLLING RESISTANCE OF HEATING ELEMENTTECHNICAL FIELD

[0001] The present disclosure relates to the field of aerosol generating devices. More particularly, the present disclosure relates to an efficient and reliable aerosol generating device, and method to control resistance of a heating element.BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced as prior art.

[0003] Aerosol-generating devices have various cartridge assemblies, with different heater properties. The performance of the aerosol generating devices and additional features such as power control, temperature control, dry inhalation prevention, E-liquid (also referred as “aerosol generating substrate, aerosol generating liquid”) level depletion detection, better flavor expression delivery, low inhalation mode, high inhalation mode, and more depend on a heater (heating element) properties and the way heating is controlled during the heating time.

[0004] In the existing aerosol generating devices, the heater properties play a crucial role. Some of the critical properties include material type and change in resistance concerning operating temperature of the heater. For example, a Nichrome heater typically offers better flavour expression and avoids off-taste. The Nichrome heater supports quick target temperature because of high thermal inertia and helps with fast temperature control. The Nichrome has high resistivity for the given geometry in comparison to other heaters such as stainless-steel heaters.

[0005] Controlling the temperature of the Nichrome heater is the biggest challenge due to its low temperature coefficient of resistance (TCR) value, which means that there is a minimal change in resistance over a wide range of the heater's operating temperature. This makes it very difficult, and sometimes impossible, to regulate the heater temperature. Most cartridges with the Nichrome heater or low TCR heaters do not have any temperature control. Absence of the temperature control makes it tricky to deliver critical features in the aerosol generating device, such as an aerosol generating substrate (E-liquid) depletion detection, better flavor expression, and quick delivery.

[0006] A patent document WO2019232086A1 titled, “Vaporizer device with cartridge” describes a vaporizer device including a vaporizer body and a cartridge. The vaporizer body includes an integrated board assembly configured to fit within a storage region of a support structure. The cartridge includes various seals, internal structural components, and / or absorbent padding to prevent leakage of vaporizable material and to enhance air flow. A wireless transceiver is adhered to a portion of the cartridge to transmit, receive, and / or store data. The vaporizer device includes a controller and a heater control circuitry to control a temperature of a heater. The vaporizer device includes one pressure sensor for measuring the pressure in an air flow path and another pressure sensor for measuring atmospheric pressure.

[0007] Another patent document CN219500426U titled, “Heating body, atomizing assembly and electronic atomizing device” a heating element, an atomization assembly and an electronic atomization device, wherein the heating element comprises a compact substrate and a heating film. The dense matrix includes a first surface and a second surface opposite the first surface. The compact substrate is provided with a plurality of micropores. The micropores are through holes and are used for guiding the aerosol-generating substrate to the first surface; the heating film is formed on the first surface. The ratio of the thickness of the compact matrix to the pore diameter of the micropores is 20: 1-3 : 1. Through the arrangement, the porosity of the heating element can be accurately controlled, and the consistency of products is improved; and the heating body can realize sufficient liquid supply and prevent liquid leakage during operation. The referred document focuses on improving ceramic base materials by having uniform porosity. It is related to the construction of the ceramic heater assembly. The referred document addresses the cartridge's wicking and leakage issues and the consistency of delivery. It is related to the Heater and wick assembly manufacturing. However, the referred document does not describe about identifying slight change in the heating materials so that the resistance can be measured and controlled.

[0008] Thus, the above referred documents are insufficient in providing solution for accurately measuring very low changes in resistance without changing the aerosol generating device's operating performance.

[0009] There is therefore a need in the art to develop an efficient and reliable aerosol generating device, and method to control resistance of a heating element.OBJECTS OF THE PRESENT DISCLOSURE

[0010] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as listed herein below.

[0011] It is an object of the present disclosure to provide an efficient and reliable aerosol generating device and method for controlling resistance of a heating element.

[0012] It is an object of the present disclosure to increase performance of the aerosolgenerating device without changing the existing operating sequence, adding any additional time delay, or compromising device performance.

[0013] It is another object of the present disclosure to provide an aerosol generating device that can eliminate need for an additional sensing element to measure change in resistance of a heating element, thereby reducing complexity in the aerosol generating device.

[0014] It is yet another object of the present disclosure to provide an aerosol generating device that can be cost-effective.SUMMARY

[0015] Aspects of the present disclosure relate generally to the field of aerosol generating devices. In particular, the present disclosure pertains to an efficient and reliable aerosol generating device and method to control resistance of a heating element.

[0016] According to an aspect of the present disclosure, the disclosed method for controlling resistance of a heating element of an aerosol generating device. The method includes providing, by a Pulse Width Modulation (PWM) control unit, a Pulse Width Modulation (PWM) signal to the heating element for each activation of the aerosol generating device. Further, the method includes performing, by a heater control circuit coupled to the PWM control unit, one of: determining a change in resistance of the heating element during an off- duty cycle of the PWM signal, and heating the heating element during an on-duty cycle of the PWM signal.

[0017] In one or more embodiments, in response to determining the change in resistance of the heating element during the off-duty cycle of the PWM signal, the method may include determining, by the heater control circuit, a voltage corresponding to the change in resistance of the heating element. Further, the method may include amplifying, by an amplifier coupled to the heater control circuit, the determined voltage. Furthermore, the method may include receiving, by the PWM control unit operatively coupled to the amplifier, the amplified voltage and determining resistance of the heating element corresponding to the amplified voltage. Moreover, the method may include controlling, by the PWM control unit, powerdelivered to the heating element, based on the determined resistance so as to achieve a target resistance.

[0018] In one or more embodiments, while determining resistance of the heating element, the method may further include determining, by the PWM control unit, an offset value as difference of the determined resistance and the target resistance, wherein the target resistance corresponds to a desired temperature of the heating element. The method may also include adjusting, by the PWM control unit, a duty cycle of the PWM signal, based on the determined offset value to reach the target resistance, to control power delivered to the heating element.

[0019] In one or more embodiments, the step of determining, by the heater control circuit, the change in resistance may be performed during the off-duty cycle of the PWM signal to prevent interference from a heating current flowing through the heating element.

[0020] In one or more embodiments, the step of adjusting, by the PWM control unit, the duty cycle of the PWM signal, may include delivering, by a power source coupled to the heating element, the power to the heating element during the on-duty cycle of the PWM signal.

[0021] In one or more embodiments, the step of determining, by the heater control circuit, the change in resistance may be performed in a measurement time ranging from 0.5 milliseconds to 2 milliseconds.

[0022] In one or more embodiments, an amplitude of the determined voltage may be controlled by adjusting a gain of the amplifier in a range of 1 to 2000.

[0023] In one or more embodiments, a frequency of the PWM signal may be adjusted within a range of 1Hz to 10 KHz.

[0024] In one or more embodiments, the heating element may be made of a material having a temperature coefficient of Resistance (TCR) in range of 0.0001 to 0.1 ohm / deg C.

[0025] In one or more embodiments, the step of adjusting, by the PWM control unit, the duty cycle of the PWM signal may be performed by implementing a Proportional-Integral- Derivative (PID) controller, to adjust the power delivered to the heating element in a realtime, based on the determined offset value.

[0026] In one or more embodiments, the step of adjusting, by the PWM control unit, the duty cycle of the PWM signal, may include reducing, by the PWM control unit, the duty cycle to lower the power delivered to the heating element, when the determined resistance exceeds a pre-defined resistance value. Further, the method may include increasing, by the PWM control unit, the duty cycle to increase the power delivered to the heating element, when the determined resistance is lower that the pre-defined resistance value.

[0027] In one or more embodiments, the method may include the step of switching, using two or more switches, between a heating mode and a measurement mode. During the measurement mode, the method may include determining, by the heater control circuit, the change in resistance of the heating element using a low current path, and turning off the heating current. Further, during the heating mode, the method may include powering the heating element by passing the current through the heating element using a high current path.

[0028] In one or more embodiments, the high current path may connect the heating element to the power source, when switching a main control unit of the aerosol generating device to the heating mode. The low current path may connect the heating element for determining the change in resistance, when the main control unit is switched to the measurement mode.

[0029] In another aspect, the present disclosure pertains to an aerosol generating device to control resistance of a heating element. The aerosol generating device includes a cartridge, and a main body coupled to the cartridge. The main body includes a main control unit configured to control resistance of the heating element. The main control unit includes a Pulse Width Modulation (PWM) control unit to provide a Pulse Width Modulation (PWM) signal to the heating element for each activation of the aerosol generating device. Further, the main control unit includes a heater control circuit coupled to the PWM control unit, to perform one of: determine a change in resistance of the heating element during an off-duty cycle of the PWM signal, and heat the heating element during an on-duty cycle of the PWM signal.

[0030] In one or more embodiments, to determine the change in resistance of the heating element during the off-duty cycle of the PWM signal, the heater control circuit may be configured to determine a voltage corresponding to the change in resistance of the heating element, and the determined voltage is amplified by an amplifier coupled to the heater control circuit.

[0031] In one or more embodiments, the PWM control unit may be further configured to receive the amplified voltage and determine resistance of the heating element corresponding to the amplified voltage. Further, the PWM control unit may be configured to control power delivered to the heating element, based on the determined resistance so as to achieve a target resistance.

[0032] In one or more embodiments, to determine, by the PWM control unit, the change in resistance of the heating element, the PWM control unit may be configured to determine an offset value as difference of the determined resistance and the target resistance. The target resistance may correspond to a desired temperature for the heating element. Further, thePWM control unit may be configured to adjust a duty cycle of the PWM signal, based on the determined offset value to reach the target resistance, to control the power delivered to the heating element.

[0033] In one or more embodiments, the heater control circuit may include at least six resistance elements arranged in a configuration. At least one of the at least six resistance elements may be the heating element.

[0034] In one or more embodiments, the aerosol generating device may include a power source coupled to the heater control circuit. The power source may supply an excitation voltage to the heating element included in the heater control circuit.

[0035] In one or more embodiments, the power source may be configured to deliver power to the heating element during the on-duty cycle of the PWM signal, based on the PWM signal generated by the PWM control unit.

[0036] In one or more embodiments, the heater control circuit may determine the change in resistance during the off-duty cycle of the PWM signal in a measurement time ranging from 0.5 milliseconds to 2 milliseconds to prevent interference from a heating current flowing through the heating element.

[0037] In one or more embodiments, the amplitude of the determined voltage may be controlled by adjusting a gain of the amplifier in a range of 1 to 2000.

[0038] In one or more embodiments, the frequency of the PWM signal may be adjusted within a range of 1 Hz to 10 KHz.

[0039] In one or more embodiments, the main control unit may include two or more switches connected with the heater control circuit to facilitate switching between a heating mode and a measurement mode.

[0040] In one or more embodiments, during the measurement mode, the heating current may be turned-off, and the heater control circuit may determine the change in resistance of the heating element using a low current path. Further, during the heating mode, the heater control circuit may power the heating element by passing the current through the heater control circuit using a high current path.

[0041] In one or more embodiments, wherein the high current path may connect the heating element to the power source, when the main control unit is switched to the heating mode. Further, the low current path may connect the heating element for determining change in resistance of the heating element, when the main control unit is switched to the measurement mode.

[0042] In one or more embodiments, the two or more switches may include one or more of: relays, or electronic switches including any of: Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), or solid-state relays.

[0043] In one or more embodiments, the heating element may be made of a material having a low temperature coefficient of resistance (TCR). The material for the heating element may be selected from a group consisting of: Nichrome, Nickel, Tungsten and Platinum.

[0044] In one or more embodiments, the TCR of the material used for the heating element may be in a range of 0.0001 to 0.1 ohm / deg C.

[0045] In one or more embodiments, the cartridge may include a storage portion to store an aerosol generating substrate.

[0046] In one or more embodiments, the heating element may be fluidically coupled to the storage portion of the cartridge. The heating element, on receiving power from the power source during the on-duty cycle of the PWM signals, may heat-up the aerosol generating substrate to generate an aerosol to be inhaled by a user.BRIEF DESCRIPTION OF DRAWINGS

[0047] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.

[0048] FIG. 1 illustrates an exemplary architecture / block diagram representing the proposed aerosol generating device to control resistance of a heating element, in accordance with embodiments of the present disclosure.

[0049] FIG. 2 illustrates an exemplary diagram of a main control circuit for an aerosol generating device of FIG. 1, in accordance with embodiments of the present disclosure.

[0050] FIG. 3 illustrates an exemplary flowchart representing a method for controlling resistance of a heating element of an aerosol generating device of FIG. 1 using a PWM signal, in accordance with embodiment of the present disclosure.DETAILED DESCRIPTION

[0051] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limitthe anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the disclosure.

[0052] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.

[0053] If the specification states that a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0054] As used in the description herein and throughout the description that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0055] The use of “including”, “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Further, the use of terms “first”, “second”, and “third”, and the like, herein does not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

[0056] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the description herein.

[0057] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skilled in the art. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural andfunctional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).

[0058] The present disclosure relates to the field of aerosol generating devices. More particularly, the present disclosure relates to a simple and improved aerosol generating device and method to control resistance of a heating element.

[0059] In the existing aerosol generating devices, the heater (heating element) properties play a crucial role. Some of the critical properties include material type and change in resistance concerning the heater operating resistance. A Nichrome heater typically offers better flavor expression and avoids off-taste. Controlling the resistance of the Nichrome heater is the biggest challenge due to its low temperature coefficient of resistance (TCR) value, which means that there is a minimal change in resistance over a wide range of the heater's operating temperature. This makes it very difficult, and sometimes impossible, to regulate the heater resistance. Most cartridges with the Nichrome heater or low TCR heaters do not have any resistance control.

[0060] To address the aforesaid issues, the proposed aerosol generating device has a main control unit comprising a heater control circuit, aiming to cater to the situations where the change in resistance of the heater is too low to be detected, and where a fast and precise resistance control is required. The proposed aerosol generating device integrates a heater control circuit, a heating element, a pulse width modulation control unit, and an amplifier to enhance control and ability to fine-tune the temperature to specific requirements.

[0061] As illustrated, in an embodiment, referring to FIGs. 1 & 2, the proposed aerosol generating device 100 (also referred as device 100 herein) includes a cartridge 102, and a main body 106 coupled to the cartridge 102. The main body 106 includes a main control unit 200 configured to control resistance of a heating element 108. The main control unit 200 includes a Pulse Width Modulation (PWM) control unit 206 configured to provide a Pulse Width Modulation (PWM) signal to the heating element 108 for each activation of the aerosol generating device 100. A frequency of the PWM signal can be adjusted within a range of 1Hz to 10 KHz. In an embodiment, a user can activate the aerosol generating device 100, for example, via a button or a using a sensor, such as a pressure sensor or an airflow sensor, and the like, without any limitations.

[0062] The main control unit 200 includes a heater control circuit 202 coupled to the PWM control unit 206, to perform one of: determine a change in resistance of the heating element 108 during an off-duty cycle of the PWM signal, and heat the heating element 108 during anon-duty cycle of the PWM signal. To determine the change in resistance of the heating element 108 during the off-duty cycle of the PWM signal, the heater control circuit 202 can be configured to determine a voltage corresponding to the change in resistance of the heating element 108, and the determined voltage is amplified by an amplifier 204 coupled to the heater control circuit 202. An amplitude of the determined voltage can be controlled by adjusting a gain of the amplifier 204 in a range of 1 to 2000. Further, the heater control circuit 202 can determine the change in resistance during the off-duty cycle of the PWM signal in a measurement time ranging from 0.5 milliseconds to 2milliseconds to prevent interference from a heating current flowing through the heating element 108. In an embodiment, the heater control circuit 202 can include at least six resistance elements arranged in a configuration, at least one of the at least six resistance elements is the heating element 108. In an embodiment, the main control unit 200 may be a printed circuit board comprising components such as the heater control circuit 202, the amplifier 204, PWM control unit 206, two or more switches 208, and the like.

[0063] The PWM control unit 206 can be further configured to receive the amplified voltage and determine resistance of the heating element 108 corresponding to the amplified voltage. Furthermore, the PWM control unit 206 can be configured to control power delivered to the heating element 108, based on the determined resistance so as to achieve a target resistance. In addition, to determine, by the PWM control unit 206, the change in resistance of the heating element 108, the PWM control unit 206 can be configured to determine an offset value as difference of the determined resistance and the target resistance. The target resistance can correspond to a desired temperature for the heating element 108. In an embodiment, the desired temperature may be a target temperature of the heating element 108 which causes an aerosol generating substrate to form an aerosol. Further, the PWM control unit 206 can be configured to adjust a duty cycle of the PWM signal, based on the determined offset value to reach the target resistance, to control the power delivered to the heating element 108.

[0064] In an embodiment, the aerosol generating device 100 can include a power source 112 coupled to the heater control circuit 202. The power source 112 can supply an excitation voltage to the heating element 108 which is included in the heater control circuit 202. The power source 112 can be configured to deliver power to the heating element 108 during the on-duty cycle of the PWM signal, based on the PWM signal generated by the PWM control unit 206. In an exemplary embodiment, the power source 112 can be a battery, including, without limitations, a rechargeable lithium-ion battery, a lithium polymer battery, Nickel-metal Hydride (NiMH) battery, super capacitor, hybrid capacitor and the like. The battery provides the electric current required to heat-up the heating element 108 and aerosolize an aerosol generating substrate stored in a storage portion of the cartridge 102. The storage portion can be fluidically connected to the heating element 108. The heating element 108 can be connected to the power source 112 during the heating mode, which heating element 108 on receiving power from the power source 112 during the on-duty cycle of the PWM signals, heats-up the aerosol generating substrate to generate the aerosol to be inhaled by a user.

[0065] In an embodiment, referring to FIG. 2, the main control unit 200 can include the two or more switches 208-1, 208-2 (also collectively referred as “switches 208” hereinafter) connected with the heater control circuit 202 to facilitate switching between a heating mode and a measurement mode. During the measurement mode, the heating current can be turned- off, and the heater control circuit 202 can determine the change in resistance of the heating element 108 using a low current path LP. The low current path LP can connect the heating element 108 (via switch 208-2) for determining change in resistance of the heating element 108, when the main control unit 200 is switched to the measurement mode. Further, during the heating mode, the heater control circuit 202 can power the heating element 108 by passing the current through the heater control circuit 202 using a high current path HP. The high current path HP can connect the heating element 108 (via switch 208-1) to the power source 112, when the main control unit 200 is switched to the heating mode. In an embodiment, the switches 208 can be selected from a group consisting of, but not limited to: relays, or electronic switches such as metal-oxide-semiconductor field-effect transistors (MOSFETs), solid-state relays. In a preferred embodiment, the switches 208 can be MOSFETs.

[0066] In an embodiment, the switches 208 handle the current paths when integrating the heater control circuit 202 for both the measurement mode and the heating mode of the aerosol generating device 100. During the heating mode, to deliver significant power to the heating element 108, a high-current switch 208-1 can be incorporated to handle elevated currents with overheating or degradation. On the other hand, during the measurement mode, to determine the change in resistance, a low-current switch 208-2 can be configured in the low current path LP as the current must be kept low in the low current path LP to prevent affecting the measuring of actual resistance or change in resistance of the heating element 108. In an embodiment, the change in resistance of the heating element 108 occurring for a previous heating cycle of the aerosol generating device, can be determined.

[0067] In an embodiment, the aerosol generating device 100 can include a mouthpiece 104 coupled to the cartridge 102. The mouthpiece 104 can be configured to provide a direct pathway for the aerosol being generated by heating the aerosol generating substrate, to be inhaled by the user. In general, the design of the mouthpiece 104 can vary depending on the style and design of the aerosol generating device 100, the design of the mouthpiece 104 can include, but not limited to: a narrow and tube-like structure, a wider structure, a flat structure, and the like.

[0068] In some embodiments, the cartridge 102 can be a refillable tank in the aerosol generating device 100, while in some embodiments, the cartridge 102 can be a disposable cartridge. The cartridge 102 holds the aerosol generating substrate, which can include, but are not limited to: a mixture of propylene glycol (PG), a vegetable glycerin (VG), flavorings, and active compounds.

[0069] In an embodiment, the heating element 108 can be made of a material with a low temperature coefficient (TCR). The material for the heating element 108 can be selected from but not limited to a group consisting of: Nichrome, Nickel, Tungsten, Platinum, and the like. More preferably, the heating element 108 can be made of Nichrome. The temperature coefficient of Resistance (TCR) of the material used for the heating element 108 can be in a range of 0.0001 to 0.1 ohm / deg C.

[0070] In an embodiment, the amplifier 204 can be selected from but not limited to Operational Amplifier (Op-Amp) such as instrumentation amplifier configuration, differential amplifier configuration, and Low-noise Op-Amp, Programmable Gain Amplifier (PGA), Instrumentation Amplifier with Digital Calibration, Op-Amp with Built-in Analog-to-Digital Converter (ADC), and the like.

[0071] In an embodiment, the PWM control unit 206 can be implemented as one or more microprocessors, microcomputers, microcontrollers, edge or fog microcontrollers, digital signal processors, central processing units, logic circuitries, and / or any devices that process data, based on operational instructions. Among other capabilities, the processor can be configured to fetch and execute computer-readable instructions stored in a memory of the PWM control unit 206. The memory can be configured to store one or more computer- readable instructions or routines in a non-transitory computer readable storage medium, which can be fetched and executed to adjust the duty cycle of the PWM signal. The memory can comprise any non-transitory storage device including, for example, volatile memory such as Random Access Memory (RAM), or non-volatile memory such as Erasable Programmable Read-Only Memory (EPROM), flash memory, and the like.

[0072] In an embodiment, by integrating pulse width modulation (PWM) control unit 206, the heater control circuit 202, the amplifier 204 and temperature coefficient of resistance (TCR) of the heating element 108 precise control and measurement of the resistance of the heating element 108 can be achieved. The PWM control unit 206 is used to control the power delivered to the heating element 108. By adjusting the duty cycle of the PWM signal, the effective power and thus the heating rate can be finely controlled. The heater control circuit 202 is used for precise resistance measurement of the heating element 108, which changes with temperature. Further, the TCR parameter describes how the resistance of the heating element 108 changes with temperature. This characteristic is used to correlate resistance measurements with temperature changes.

[0073] In an embodiment, the cartridge 102 can include the heating element 108 and a wick 118 that draws the aerosol generating substrate from the storage portion of the cartridge 102 to the heating element 108. The heating element 108 heats up when powered, thereby aerosolizing the aerosol generating substrate.

[0074] In an embodiment, the cartridge 102 can include a plurality of pogo pins 110 configured to interface with contact pins of the main control unit 200 to establish electrical connection.

[0075] In an embodiment, the main body 106 can include a display unit 116 configured at an outer surface of the main body 106. The display unit 116 can be configured to display status of the device 100 and current resistance and / or temperature of the heating element 108. The display unit 116 can be selected from but not limited to Liquid Crystal Display (LCD), Light Emitting Diode (LED) Display, Organic Light Emitting Diode (OLED) Display, Electroluminescent (EL) Display, Touchscreen Display, and the like.

[0076] In an embodiment, the main body 106 can include a plurality of Light Emitting Diodes (LEDs) 114 configured to indicate the charging mode, heating mode and alarm events in the aerosol generating device 100.

[0077] Referring to FIG. 3, and according to another aspect, a method 300 for controlling resistance of a heating element 108 of an aerosol generating device 100 is disclosed. At block 302, the method 300 includes the step of providing, by a Pulse Width Modulation (PWM) control unit 206, a Pulse Width Modulation (PWM) signal to the heating element 108 for each activation of the aerosol generating device 100. A frequency of the PWM signal can be adjusted within a range of 1Hz to 10 KHz.

[0078] At block 304, the method 300 includes the step of performing, by a heater control circuit 202 coupled to the PWM control unit 206, one of: determining a change in resistanceof the heating element 108 during an off-duty cycle of the PWM signal, and heating the heating element 108 during an on-duty cycle of the PWM signal.

[0079] In an embodiment, in response to determining the change in resistance of the heating element 108 during the off-duty cycle of the PWM signal, the method 300 can include determining, by the heater control circuit, a voltage corresponding to the change in resistance of the heating element 108. Further, the method 300 can include amplifying, by an amplifier 204 coupled to the heater control circuit, the determined voltage. An amplitude of the determined voltage can be controlled by adjusting a gain of the amplifier 204 in a range of 1 to 2000.

[0080] Furthermore, the method 300 can include receiving, by the PWM control unit 206 operatively coupled to the amplifier 204, the amplified voltage and determining resistance of the heating element 108 corresponding to the amplified voltage. Moreover, the method 300 can include controlling, by the PWM control unit 206, power delivered to the heating element 108, based on the determined resistance so as to achieve a target resistance.

[0081] In an embodiment, the method 300 can further include determining, by the PWM control unit 206, an offset value as difference of the determined resistance and the target resistance, where the target resistance can correspond to a desired temperature of the heating element 108. The method 300 can also include adjusting, by the PWM control unit 206, a duty cycle of the PWM signal, based on the determined offset value to reach the target resistance, to control power delivered to the heating element 108. The step of adjusting, by the PWM control unit 206, the duty cycle of the PWM signal, can further include the step of delivering, by a power source 112 coupled to the heating element 108, the power to the heating element 108 during the on-duty cycle of the PWM signal.

[0082] In an embodiment, the step of determining, by the heater control circuit 202, the change in resistance can be performed during the off-duty cycle of the PWM signal to prevent interference from a heating current flowing through the heating element 108. The change in resistance can be performed in a measurement time ranging from 0.5 milliseconds to 2 milliseconds.

[0083] In an embodiment, the step of adjusting, by the PWM control unit 206, the duty cycle of the PWM signal can be performed by implementing a Proportional-Integral-Derivative (PID) controller, to adjust the power delivered to the heating element 108 in a real-time, based on the determined offset value.

[0084] In an embodiment, measuring the change in resistance using the heater control circuit 202 can be performed during the off-duty cycle of the PWM signal to avoid additionaltemperature sensor for measuring the temperature in the heating element 108. Same heating element 108 is used for heating the liquid as well as measure its operating temperature in terms of resistance.

[0085] In an embodiment, the step of adjusting 308, by the PWM control unit 206, the duty cycle of the PWM signal, can include the step of delivering, by a power source 112 coupled to the heating element 108, the power to the heating element 108 during an on-duty cycle of the PWM signal.

[0086] In an embodiment, the step of adjusting, by the PWM control unit 206, the duty cycle of the PWM signal, can include reducing, by the PWM control unit 206, the duty cycle to lower the power delivered to the heating element 108, when the determined resistance exceeds a pre-defined resistance value. Further, the method 300 can include increasing, by the PWM control unit 206, the duty cycle to increase the power delivered to the heating element 108, when the determined resistance is lower that the pre-defined resistance value. For instance, the pre-defined resistance value for the heating element 108 can be set at 0.5 ohms, and say the determined resistance can come out to be 0.4 ohms. In this scenario, the PWM control unit 206 can increase the duty cycle of the PWM signal to increase the power delivered to the heating element 108. For another instance, the pre-defined resistance value for the heating element 108 can be set at 0.3 ohms, and the determined resistance is same as 0.4 ohms. In this scenario, the PWM control unit 206 can decrease the duty cycle of the PWM signal to decrease the power delivered to the heating element 108.

[0087] In an embodiment, the heater control circuit 202 can include at least six resistors, where the heating element 108 acts as any one of the at least six resistors.

[0088] In an embodiment, the method 300 can further include switching between a heating mode and a measurement mode, using two or more switches 208, wherein during the measurement mode, the heating current can be turned-off, and the heater control current can determine the change in resistance of the heating element 108 using a low current path LP. Further, during the heating mode, the heater control circuit 202 can be used to power the heating element 108 by passing the heating current through it using a high current path HP.

[0089] In an embodiment, the high current path HP can connect the heating element 108 to the power source 112 when switching a main control unit 200 of the aerosol generating device 100 to the heating mode. The lower current path can connect the heating element 108 to determine the change in resistance of the heating element 108, when switching the main control unit 200 to the measurement mode

[0090] As can be appreciated, the proposed aerosol generating device 100 and method 300 to control resistance of a heating element 108 caters situations where change in resistance of the heating element 108 is too low, and where a fast and precise temperature control is required, without need of an additional sensing element, thereby reducing complexity in designing the aerosol generating device 100.

[0091] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.ADVANTAGES OF THE INVENTION

[0092] The present invention provides an efficient and reliable aerosol generating device and method for controlling resistance of a heating element.

[0093] The present invention provides an increase performance of the aerosolgenerating device without changing the existing operating sequence, adding any additional time delay, or compromising device performance.

[0094] The present invention provides an aerosol generating device that can eliminate need for an additional sensing element to measure resistance of a heating element, thereby reducing complexity in the aerosol generating device.

[0095] The present invention provides an aerosol generating device that can be cost- effective.

Claims

We Claim:

1. A method (300) for controlling resistance of a heating element (108) of an aerosol generating device (100), the method (300) comprising: providing (302), by a Pulse Width Modulation (PWM) control unit (206), a Pulse Width Modulation (PWM) signal to the heating element (108) for each activation of the aerosol generating device (100); and performing (304), by a heater control circuit (202) coupled to the PWM control unit (206), one of: determining a change in resistance of the heating element (108) during an off-duty cycle of the PWM signal; and heating the heating element (108) during an on-duty cycle of the PWM signal.

2. The method (300) as claimed in claim 1, wherein in response to determining the change in resistance of the heating element (108) during the off-duty cycle of the PWM signal, the method (300) comprising: determining, by the heater control circuit (202), a voltage corresponding to the change in resistance of the heating element (108); amplifying, by an amplifier (204) coupled to the heater control circuit (202), the determined voltage; receiving, by the PWM control unit (206) operatively coupled to the amplifier (204), the amplified voltage and determining resistance of the heating element (108) corresponding to the amplified voltage; and controlling, by the PWM control unit (206), power delivered to the heating element (108) based on the determined resistance so as to achieve a target resistance.

3. The method (300) as claimed in claim 2, determining, by the PWM control unit (206), resistance of the heating element (108) further comprising: determining, by the PWM control unit (206), an offset value as difference of the determined resistance and the target resistance, wherein the target resistance corresponds to a desired temperature of the heating element (108); and adjusting, by the PWM control unit (206), a duty cycle of the PWM signal, based on the determined offset value to reach the target resistance, to control power delivered to the heating element (108).

4. The method (300) as claimed in claim 1, wherein the step of determining, by the heater control circuit (202), the change in resistance is performed during the off-duty cycle of the PWM signal to prevent interference from a heating current flowing through the heating element (108).

5. The method (300) as claimed in claim 3, wherein the step of adjusting, by the PWM control unit (206), the duty cycle of the PWM signal, comprises delivering, by a power source (112) coupled to the heating element (108), the power to the heating element (108) during the on-duty cycle of the PWM signal.

6. The method (300) as claimed in claim 4, wherein the step of determining, by the heater control circuit (202), the change in resistance is performed in a measurement time ranging from 0.5 milliseconds to 2 milliseconds.

7. The method (300) as claimed in claim 2, wherein an amplitude of the determined voltage is controlled by adjusting a gain of the amplifier (204) in a range of 1 to 2000.

8. The method (300) as claimed in claim 1, wherein a frequency of the PWM signal is adjusted within a range of 1Hz to 10 KHz.

9. The method (300) as claimed in claim 1, wherein a temperature coefficient of Resistance (TCR) of a material used for the heating element (108) is in range of 0.0001 to 0.1 ohm / deg C.

10. The method (300) as claimed in claim 3, wherein the step of adjusting, by the PWM control unit (206), the duty cycle of the PWM signal is performed by implementing a Proportional-Integral-Derivative (PID) controller, to adjust the power delivered to the heating element (108) in a real-time, based on the determined offset value.

11. The method (300) as claimed in claim 3, wherein the step of adjusting , by the PWM control unit (206), the duty cycle of the PWM signal, comprises: reducing, by the PWM control unit (206), the duty cycle to lower the power delivered to the heating element (108), when the determined resistance exceeds a predefined resistance value, or increasing, by the PWM control unit (206), the duty cycle to increase the power delivered to the heating element (108), when the determined resistance is lower that the pre-defined resistance value.

12. The method (300) as claimed in claim 1, further comprising the step of switching, using two or more switches (208), between a heating mode and a measurement mode,wherein, during the measurement mode, determining, by the heater control circuit (202), the change in resistance of the heating element (108) using a low current path (LP), and turning off the heating current, and wherein, during the heating mode, powering the heating element (108) by passing the current through the heating element (108) using a high current path (HP).

13. The method (300) as claimed in claim 12, wherein the high current path (HP) connects the heating element (108) to the power source (112) when switching a main control unit (200) of the aerosol generating device (100) to the heating mode, and wherein the low current path (LP) connects the heating element (108) for determining the change in resistance, when the main control unit (200) is switched to the measurement mode.

14. An aerosol generating device (100) to control resistance of a heating element (108), wherein the aerosol generating device (100) comprising: a cartridge (102); and a main body (106) coupled to the cartridge (102), wherein the main body (106) comprises a main control unit (200) configured to control resistance of the heating element (108), wherein the main control unit (200) comprises: a Pulse Width Modulation (PWM) control unit (206) to provide a Pulse Width Modulation (PWM) signal to the heating element (108) for each activation of the aerosol generating device (100); and a heater control circuit (202) coupled to the PWM control unit (206), to perform one of: determine a change in resistance of the heating element (108) during an off-duty cycle of the PWM signal; and heat the heating element (108) during an on-duty cycle of the PWM signal.

15. The aerosol generating device (100) as claimed in claim 14, wherein to determine the change in resistance of the heating element (108) during the off-duty cycle of the PWM signal, the heater control circuit (202) is configured to determine a voltage corresponding to the change in resistance of the heating element (108), and the determined voltage is amplified by an amplifier (204) coupled to the heater control circuit (202).

16. The aerosol generating device (100) as claimed in claim 15, wherein the PWM control unit (206) is further configured to:receive the amplified voltage and determine resistance of the heating element (108) corresponding to the amplified voltage; and control power delivered to the heating element (108) based on the determined resistance so as to achieve a target resistance.

17. The aerosol generating device (100) as claimed in claim 16, wherein to determine, by the PWM control unit (206), resistance of the heating element (108), the PWM control unit (206) is further configured to: determine an offset value as difference of the determined resistance and the target resistance, wherein the target resistance corresponds to a desired temperature for the heating element (108); and adjust a duty cycle of the PWM signal, based on the determined offset value to reach the target resistance, to control the power delivered to the heating element (108).

18. The aerosol generating device (100) as claimed in claim 14, wherein the heater control circuit (202) comprises at least six resistance elements arranged in a configuration, wherein at least one of the at least six resistance elements is the heating element (108).

19. The aerosol generating device (100) as claimed in claim 14, wherein the aerosol generating device (100) comprises a power source (112) coupled to the heater control circuit (202), wherein the power source (112) supplies an excitation voltage to the heating element (108) included in the heater control circuit (202).

20. The aerosol generating device (100) as claimed in claim 19, wherein the power source (112) is configured to deliver power to the heating element (108) during the on-duty cycle of the PWM signal, based on the PWM signal generated by the PWM control unit (206).

21. The aerosol generating device (100) as claimed in claim 14, wherein the heater control circuit (202) determines the change in resistance during the off-duty cycle of the PWM signal in a measurement time ranging from 0.5 milliseconds to 2 milliseconds to prevent interference from a heating current flowing through the heating element (108).

22. The aerosol generating device (100) as claimed in claim 15, wherein an amplitude of the determined voltage is controlled by adjusting a gain of the amplifier (204) in a range of 1 to 2000.

23. The aerosol generating device (100) as claimed in claim 14, wherein a frequency of the PWM signal is adjusted within a range of 1Hz to 10 KHz.

24. The aerosol generating device (100) as claimed in claim 14, wherein the main control unit (200) comprises two or more switches (208) connected with the heater control circuit (202) to facilitate switching between a heating mode and a measurement mode.

25. The aerosol generating device (100) as claimed in claim 24, wherein during the measurement mode, the heating current is turned-off, and the heater control circuit (202) determines the change in resistance of the heating element (108) using a low current path (LP), and wherein during the heating mode, the heater control circuit (202) powers the heating element (108) by passing the current through the heater control circuit (202) using a high current path (HP).

26. The aerosol generating device (100) as claimed in claim 24, wherein the high current path (HP) connects the heating element (108) to the power source (112), when the main control unit (200) is switched to the heating mode, and wherein the low current path (LP) connects the heating element (108) for determining change in resistance of the heating element (108), when the main control unit (200) is switched to the measurement mode.

27. The aerosol generating device (100) as claimed in claim 24, wherein the two or more switches (208) comprise one or more of: relays, or electronic switches including any of: Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), or solid-state relays.

28. The aerosol generating device (100) as claimed in claim 14, wherein the heating element (108) is made of material with a low temperature coefficient of resistance (TCR), wherein the material for the heating element (108) is selected from a group consisting of: Nichrome, Nickel, Tungsten and Platinum.

29. The aerosol generating device (100) as claimed in claim 28, wherein the TCR of the material used for the heating element (108) is in a range of 0.0001 to 0. 1 ohm / deg C.

30. The aerosol generating device (100) as claimed in claim 14, wherein the cartridge (102) comprises a storage portion to store an aerosol generating substrate.

31. The aerosol generating device (100) as claimed in claims 19 and 30, wherein the heating element (108) is fluidically coupled to the storage portion of the cartridge (102), which heating element (108) on receiving power from the power source (112) during the on-duty cycle of the PWM signals, heats-up the aerosol generating substrate to generate an aerosol to be inhaled by a user.

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