Control circuit and method for delivering power to a heating element

Abstract

To provide a control circuit and a method for delivering power to heating elements.SOLUTION: In various embodiments, a control circuit is adapted to control the power supplied to a heating element by a battery. The control circuit can include a memory for storing known data and a circuit configured to control the delivery of the power from the battery to the heating element according to measured parameters, calculated parameters, and the known data.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control circuit and method for delivering power to a heating element.

Background Art

[0002] Many electronic devices use a battery, such as a lithium-ion battery, to provide a primary power source to the electronic device. In some applications, such as electronic cigarettes (also called vaping devices, e-cigarettes, vape pens, and nicotine evaporators), the battery supplies power to a heating element that is used to heat a liquid to form a vapor. Some conventional systems use an open-loop heating method where the heating element can potentially reach undesirable and / or dangerous temperatures as a result. Alternatively, other conventional systems use a closed-loop heating method, but this method requires additional circuitry, thereby increasing the cost of the system, increasing power loss, generating excessive heat, and / or delaying the feedback of measured parameters (e.g., voltage, current). For optimal operation, it is desirable to provide a stable power supply to the heating element using minimal circuitry.

Summary of the Invention

[0003] The present invention relates to a control circuit and method for delivering power to a heating element. <​​​​​In various embodiments, the control circuit is adapted to control the power supplied to the heating element by the battery. The control circuit may include a memory for storing known data and a circuit configured to control the delivery of power from the battery to the heating element according to measured parameters, calculated parameters, and known data.

[0006] According to one embodiment, a control circuit adapted to control a heating element powered by a battery includes a memory configured to store known battery data including a first profile and a second profile; a fuel gauge circuit communicating with the memory and the battery, configured to determine the resistance of the battery according to the first and second profiles; a logic circuit connected to the fuel gauge circuit, configured to calculate a first power value based on the determined resistance; and a signal generator circuit responding to the logic circuit, configured to generate a control signal according to the calculated first power value, wherein the control circuit selectively connects the battery to the heating element according to the control signal.

[0007] In one embodiment of the above control circuit, determining the resistance of a battery includes measuring the actual voltage of the battery, determining the battery capacity according to the measured actual voltage using a first profile, and determining the resistance of the battery according to the determined capacity using a second profile.

[0008] In one embodiment of the above control circuit, the logic unit further calculates a first power value based on a first resistance value of the heating element at the start time.

[0009] In one embodiment of the control circuit described above, the memory further includes a third profile that includes a relationship between the resistance of the heating element and time.

[0010] In one embodiment, the control circuit further includes a timer for measuring elapsed operating time, which is measured from the start time, and when the timer reaches a predetermined elapsed operating time, the logic unit calculates a new first power according to a second resistance value of the heating element and a third profile.

[0011] In one embodiment of the control circuit described above, the first profile includes the relationship between the battery voltage value and the battery capacity value, and the second profile includes the relationship between the battery resistance value and the battery capacity value.

[0012] In one embodiment of the control circuit described above, the control signal includes the ratio of a predetermined target power to a calculated first power.

[0013] In another embodiment, a method for controlling the delivery of power from a battery to a heating element includes measuring the actual voltage of a battery; determining the capacity of the battery according to the measured actual voltage and first known battery data, the first known battery data including a relationship between voltage and capacity values; determining the resistance of the battery according to the determined capacity and second known battery data, the second known battery data including a relationship between battery resistance and capacity values; calculating a first power according to the determined resistance of the battery and the resistance of the heating element; calculating a ratio between a predetermined target power and the calculated first power; and electrically connecting the battery to the heating element according to the calculated ratio.

[0014] In one operation of the above method, the resistance of the heating element is one of the initial resistance value of the heating element when it is new and the determined resistance after degradation over time.

[0015] In one operation, the above method further includes measuring the elapsed operating time and determining the resistance value of the heating element that has deteriorated over time, utilizing known heating element data and the elapsed operating time value.

[0016] The technical effect achieved by the present invention is to provide a stable power supply to the heating element using a minimum amount of circuitry for optimal operation.

Brief Description of the Drawings

[0017] A more complete understanding of the present technology can be derived by referring to the detailed description when considered in connection with the following exemplary figures. In the following figures, like reference numerals refer to like elements and steps throughout the drawings.

[0018] [Figure 1] Typically shown is an electronic system having a heating element powered by a battery according to an exemplary embodiment of the present technology.

[0019] [Figure 2] It is a block diagram of an electronic system according to an exemplary embodiment of the present technology.

[0020] [Figure 3] It is a graph showing the relationship between the battery voltage value and the battery capacity value according to an exemplary embodiment of the present technology.

[0021] [Figure 4] It is a graph showing the relationship between the battery resistance value and the battery capacity value according to an exemplary embodiment of the present technology.

[0022] [Figure 5A] It is a graph showing a first relationship between the heater element resistance value and time according to the present technology.

[0023] [Figure 5B] It is a graph showing a second relationship between the heater element resistance value and time according to the present technology.

[0024] [Figure 5C] It is a graph showing a third relationship between the heater element resistance value and time according to the present technology.

[0025] [Figure 6] A flowchart for controlling the delivery of power from a battery to a heating element according to an exemplary embodiment of the present technology.

[0026] [Figure 7] An alternative flowchart for controlling the delivery of power from a battery to a heating element according to an exemplary embodiment of the present technology.

[0027] [Figure 8] A graph showing the relationship between heater power and battery capacity value when the PWM ratio is 100%.

[0028] [Figure 9] A graph showing an exemplary relationship between the PWM ratio used to supply a constant power to a heater element and the battery capacity value according to an exemplary embodiment of the present technology.

[0029] [Figure 10] A graph showing the relationship between heater power and battery capacity value after adjusting the PWM ratio according to the PWM ratio shown in FIG. 9 according to an embodiment of the present technology.

MODE FOR CARRYING OUT THE INVENTION

[0030] The present technology can be described with respect to functional block components and various processing steps. Such functional blocks can be realized by any number of components configured to perform specific functions and achieve various results. For example, the present technology can employ various heating elements, signal generators, voltage sensors, current sensors, Coulomb counters, logic gates, memory devices, semiconductor devices such as transistors and capacitors, etc. that can perform various functions. In addition, the present technology can be implemented with any number of systems, and the systems described are merely exemplary applications for this technology. Furthermore, the present technology can employ any number of prior arts for measuring voltage, measuring current, calculating the capacity of a battery, performing various mathematical calculations, storing data, etc.

[0031] Methods and apparatus for power supply control circuits according to various aspects of this technology can operate with any suitable electronic systems and / or devices such as home appliances, portable devices, and battery-powered heating devices. Referring to Figure 1, an exemplary system 100 includes a heating element 120 powered by a rechargeable battery 105 and a control circuit 110 for controlling the amount of power supplied to the heating element 120. For example, system 100 may include an e-cigarette containing a vapor cartridge 125 containing a liquid 130. In an exemplary embodiment, system 100 may further include a sensor 115 for detecting when a user applies inhalation force (i.e., puffing) to the e-cigarette, which activates the heating element 120. System 100 may further include a light-emitting diode (LED) 135 to simulate "combustion" and / or to provide a visual response to inhalation force.

[0032] Battery 105 supplies power to the heating element 120 and / or other components within the system 100, such as the LED 135 and the control circuit 110. Battery 105 may include a lithium-ion battery. Alternatively, battery 105 may include a nickel metal hydride battery, a nickel-cadmium battery, or a lithium-based battery such as a lithium cobalt, lithium iron phosphate, lithium titanate, or lithium polymer battery.

[0033] The heating element 120 may include an electric heater, such as an infrared heater element, a photonic source, or an induction heater element. The heating element 120 may be implemented as a heating wire or filament. The heating element 120 may include a resistive material, such as doped ceramics, electrically "conductive" ceramics (e.g., molybdenum disilide), carbon, graphite, metals, metal alloys, and composite materials made from ceramic and / or metallic materials. Such composite materials may include doped or undoped ceramics. A suitable example of a doped ceramic is doped silicon carbide. Suitable examples of metals include titanium, zirconium, tantalum, and metals from the platinum group. Examples of suitable metal alloys include stainless steel, nickel-containing alloys, cobalt-containing alloys, chromium-containing alloys, aluminum-titanium-zirconium-containing alloys, hafnium-containing alloys, niobium-containing alloys, molybdenum-containing alloys, tantalum-containing alloys, tungsten-containing alloys, tin-containing alloys, gallium-containing alloys, manganese-containing alloys, gold-containing alloys, iron-containing alloys, and superalloys based on nickel, iron, cobalt, stainless steel, Timetal®, and iron-manganese-aluminum alloys. In composite materials, the electrical resistance material may optionally be embedded in an insulating material, or encapsulated or coated with an insulating material, depending on the dynamics of energy transfer and desired external physicochemical properties.

[0034] The control circuit 110 controls and / or manages the functions of the battery 105, heating element 120, and LED 135 according to various input signals, such as input signals from the sensor 115. The control circuit 110 may include an integrated circuit that includes various circuits and / or systems that work together to provide desired output and / or control signals.

[0035] According to an exemplary embodiment, the control circuit 110 is connected to the battery 105 and can measure various battery characteristics such as voltage, current, and temperature.

[0036] According to an exemplary embodiment, referring to Figure 2, the control circuit 110 includes a fuel gauge circuit 205, a logic circuit 215, a memory 210, a signal generator circuit 220, and a timer 225, which work together to control, or otherwise manage, various functions of the system 100, such as controlling power to the heating element 120 and battery management (e.g., charge / discharge cycles). The control circuit 110 may be formed as an integrated circuit on a single chip or may be integrated across multiple chips.

[0037] According to an exemplary embodiment, the control circuit 110 selectively connects the battery 105 to the heating element 120. For example, the control circuit 110 may include a switch 200 positioned between the terminals of the battery 105 and the heating element 120, which operates to electrically connect and disconnect the battery 105 to the heating element 120. The switch 200 may include any device suitable for providing a selective connection between two or more devices.

[0038] Switch 200 may include transistors such as field-effect transistors (FETs) that use an electric field to control the electrical behavior of a device. Many different implementations of field-effect transistors exist. Field-effect transistors can be a desirable implementation because they generally exhibit very high input impedance at low frequencies. Conductivity between the drain and source terminals is controlled by an electric field within the device, which is generated by a voltage difference between the body and gate of the device.

[0039] Memory 210 stores various battery data. In an exemplary embodiment, memory 210 may include a first profile 230 containing known data that provides a relationship between battery voltage values ​​and capacity values, such as the data shown in the graph in Figure 3. Generally, battery voltage is higher at higher RSOC values ​​and lower at lower RSOC values. The specific data included in the first profile 230 may be determined by testing the battery 105 in an environment that simulates the system 100 in which the battery 105 is used. The first profile 230 may be implemented as a lookup table accessible by the logic circuit 215 and / or the fuel gauge circuit 205 or as any other suitable storage device.

[0040] In an exemplary embodiment, the memory 210 further includes a second profile 230 containing known data that provides a relationship between battery resistance and capacity values, such as the data shown in the graph of Figure 4. The specific data included in the second profile 235 may be determined by testing the battery 105 in an environment that simulates the system 100 in which the battery 105 is used. The second profile 230 may be implemented as a lookup table accessible by the logic circuit 215 and / or the fuel gauge circuit 205 or as any other suitable storage device.

[0041] The memory may further include a third profile 240 containing known heater element data that provides a relationship between heater element resistance and time, such as the data shown in the graphs of Figures 5A to 5C. The specific data included in the third profile 240 can be determined by testing the heater element 120 in an environment that simulates the system 100 in which the heater element 120 is used. Generally, when power is applied to the heater element 120, the heater element 120 has an initial resistance at time 0, and the heater element resistance may increase, decrease, or remain constant over time according to its material properties. The third profile 240 may be implemented as a lookup table accessible by the logic circuit 215 and / or the fuel gauge circuit 205 or as any other suitable storage device.

[0042] The memory 210 may be further configured to store a predetermined target power value "Power2". The predetermined target power value "Power2" may vary according to the specifications of a particular system implementation. For example, the predetermined target power value "Power2" may be based on various heating element specifications, such as the maximum power rating and maximum current rating of the heating element 120, as well as various battery specifications, such as the type of battery (e.g., lithium-ion, NiCd, NiMH, etc.), the reference voltage of the battery, the nominal voltage of the battery, and the charging current of the battery.

[0043] Memory 210 can be implemented as non-volatile memory, such as random access memory (RAM), read-only memory (ROM), or flash memory. A specific memory implementation may be selected according to a specific implementation of system 100, as one type of memory may be more suitable for a particular implementation of system 100.

[0044] The fuel gauge circuit 205 may be configured to receive various inputs and monitor and / or measure various battery characteristics, such as voltage, current, battery capacity (which may also be expressed as state of charge (SOC) or relative charge (RSOC) as a percentage), battery operating mode (e.g., charge and discharge), and state of health (SOH). The fuel gauge circuit 205 may also generate various types of control signals in response to the received input signals and / or battery characteristics, such as control signals for controlling charge and discharge. The fuel gauge circuit 205 may include any number of suitable circuits and / or systems and may be implemented in any suitable way, such as in the form of a large-scale integrated circuit (LSI).

[0045] According to an exemplary embodiment, the fuel gauge circuit 205 is configured to acquire relevant data from a first profile 230 and to use that relevant data to determine the capacity (RSOC) of the battery 105. For example, the fuel gauge circuit 205 may first measure the actual voltage of the battery 105 using conventional voltage sensing methods and techniques. Then, the fuel gauge circuit 205 may determine the battery capacity according to the measured actual voltage and the first profile 230. For example, a measured actual voltage of 3.6V corresponds to an RSOC of 15%.

[0046] The fuel gauge circuit 205 may also be configured to determine the resistance of the battery 105. For example, the fuel gauge circuit 205 may determine the resistance using the previously determined battery capacity (RSOC) and a second profile 235. For example, an RSOC of 15% corresponds to a resistance of 150 ohms. The fuel gauge circuit 205 may be configured to transmit the determined resistance value to the logic circuit 215.

[0047] The logic circuit 215 may be configured to perform various calculations, extract data from memory 210, receive relevant data when related to battery 105 and / or heating element 120, and / or supply various control signals. For example, the logic circuit 215 may be connected to fuel gauge circuit 205 and / or memory 210. According to an exemplary embodiment, the logic circuit 215 may be further connected to signal generator circuit 220 and provide a first control signal to signal generator circuit 220. The logic circuit 215 may include any suitable device and / or system, which may be implemented using hardware, logic gates, etc.

[0048] According to an exemplary embodiment, the logic circuit 215 is configured to calculate a maximum power value "Power1", which is described as Power1 = V2 / (R1+R2)(Equation 1), where V is the measured actual voltage of the battery 105, R1 is the determined resistance of the battery 105, and R2 is the resistance of the heating element 120.

[0049] The logic circuit 215 may be configured to obtain the resistance value R2 of the heating element 120 from the third profile 240. For example, the resistance value R2 of the heating element 120 may be the starting resistance (resistance value at time 0) or the operating resistance (resistance value after time 0). Thus, the logic circuit 215 may select an appropriate resistance value based on the length of time the heating element 120 is operating.

[0050] According to various embodiments, the logic circuit 215 may further calculate the battery current I according to the determined battery resistance R1 and the measured battery voltage (i.e., I = V / R). The logic circuit 215 may then verify the RSOC value by utilizing a fourth profile (not shown) stored in memory 210, for example, which describes the relationship between the battery current and the RSOC value.

[0051] The signal generator circuit 220 generates a second control signal for operating the switch 200. According to an exemplary embodiment, the signal generator circuit 220 may be implemented as a pulse width modulation circuit that generates a PWM signal having a square wave and a variable duty cycle. The pulse width modulation circuit may include a conventional circuit. The duty cycle of the PWM signal is the ratio of a predetermined target power value "Power2" to a calculated maximum power "Power1" (i.e., PWM = Power2 / Power1 (Equation 2)). Therefore, when the PWM signal is high, the switch 200 responds by closing (the switch is on), thereby connecting the battery 105 to the heating element 120. In contrast, when the PWM signal is low, the switch 200 responds by opening (the switch is off), thereby disconnecting the battery 105 from the heating element 120.

[0052] According to various embodiments, the control circuit 110 may further include a timer circuit 225 for tracking and measuring time intervals (periods). For example, the timer circuit 225 may start measuring when the switch 200 is first closed (t=0) and send a timer signal to the logic circuit 215 when the timer circuit 225 reaches a predetermined timer value, such as every 100ms. When the logic circuit 215 receives the timer signal, the logic circuit 215 recalculates the maximum power value "Power1" according to a new heating element resistance value corresponding to that particular timer value. The logic circuit 215 may obtain a new heating resistance value from a third profile 240.

[0053] In an exemplary operation, referring to Figures 1, 3, 4, and 6, the control circuit 110 may first measure the actual voltage of the battery 105. Then, the control circuit 110 may use the measured actual voltage in conjunction with the first profile 230 to determine the RSOC of the battery 105 (600). For example, the fuel gauge circuit 205 may obtain the RSOC value corresponding to the measured actual voltage from the memory 210.

[0054] Next, the control circuit 110 can determine the battery resistance using the RSOC determined (from step 600) in conjunction with the second profile 235 (605). For example, the fuel gauge circuit 205 can obtain the resistance value corresponding to the determined RSOC from the memory 210.

[0055] Next, the control circuit 110 can calculate the maximum power "Power1" according to the measured actual voltage, battery resistance R1, and heating element resistance R2 (610). For example, the logic circuit 215 can receive and / or acquire the measured actual voltage of the battery, battery resistance R1, and heating element resistance R2 from the fuel gauge circuit and / or memory 210.

[0056] Next, the control circuit 110 can calculate a PWM signal (615), which is defined as a predetermined power divided by the maximum power (i.e., Power2 / Power1). For example, the signal generator circuit 220 can receive the calculated maximum power "Power1" from the logic circuit 215 and obtain a predetermined target power value "Power2" from the memory 210.

[0057] Next, the control circuit 110 can operate the switch 200 according to the PWM signal (620). For example, if the PWM signal is 50%, then for one duty cycle, the switch 200 is closed for half the time and open for the other half. Similarly, if the PWM signal is 30%, then for one duty cycle, the switch is closed for 30% of the time and open for 70% of the time.

[0058] This operation can be used when the resistance characteristics of the heater element 120 remain constant over time, as shown in Figure 5C.

[0059] In an alternative operation, referring to Figures 1, 3, 4, 5A, 5B, and 7, the control circuit 110 may first measure the actual voltage of the battery 105. Then, the control circuit 110 may use the measured actual voltage in conjunction with the first profile 230 to determine the RSOC of the battery 105 (700). For example, the fuel gauge circuit 205 may obtain the RSOC value corresponding to the measured actual voltage from the memory 210.

[0060] Next, the control circuit 110 can determine the battery resistance using the RSOC determined (from step 700) in conjunction with the second profile 235 (705). For example, the fuel gauge circuit 205 can obtain the resistance value corresponding to the determined RSOC from the memory 210.

[0061] Next, the control circuit 110 can calculate the maximum power "Power1" according to the measured actual voltage, battery resistance R1, and heating element resistance R2 (710). For example, the logic circuit 215 can receive and / or acquire the measured actual voltage of the battery, battery resistance R1, and heating element resistance R2 from the fuel gauge circuit and / or memory 210.

[0062] Next, the control circuit 110 can calculate a PWM signal (715), which is defined as a predetermined power divided by the maximum power (i.e., Power2 / Power1). For example, the signal generator circuit 220 can receive the calculated maximum power "Power1" from the logic circuit 215 and obtain a predetermined target power value "Power2" from the memory 210.

[0063] Next, the control circuit 110 can operate the switch 200 according to the PWM signal (720). For example, if the PWM signal is 50%, then for one duty cycle, the switch 200 is closed for half the time and open for the other half. Similarly, if the PWM signal is 30%, then for one duty cycle, the switch is closed for 30% of the time and open for 70% of the time.

[0064] According to this embodiment, the control circuit 110 can periodically adjust the heating element resistance value R2 used to calculate the maximum power "Power1" (725). For example, after a predetermined period such as 100ms, the logic circuit 215 can obtain a new resistance value R2 corresponding to the elapsed time and calculate a new maximum power. Since the heating element resistance R2 increases with time, the new maximum power value will be smaller than the value calculated at time 0. The signal generator circuit 220 can then update the PWM ratio using the new maximum power value, and accordingly, the signal generator circuit 220 operates the switch 200.

[0065] This operation can be used when the resistance characteristics of the heating element 120 change over time (increase or decrease), as shown in Figures 5A and 5B. Therefore, the heating element resistance value R2 can be adjusted periodically. For example, when the timer 225 reaches a predetermined elapsed time, the logic unit 215 recalculates the maximum power "Power1", and the variable "R2" in Equation 1 above is the updated heating element resistance value corresponding to the elapsed time. In contrast, when the heating element 120 exhibits stable characteristics, as shown in Figure 5C, Equation 1 above is calculated using the initial heating element resistance value; in other words, the variable "R2" is the initial heating element resistance value at time 0.

[0066] In conventional systems, the power supplied from battery 105 to heating element 120 is not stable across various battery capacity values ​​(for example, as shown in Figure 8). However, embodiments of this technology adjust the PWM ratio during operation (for example, as shown in Figure 9), and therefore battery 105 provides a stable power supply to heating element 120 (for example, as shown in Figure 10).

[0067] In the preceding description, the technology has been described with reference to specific exemplary embodiments. The specific implementations illustrated and described are illustrative of the technology and its best form and are not intended in any way to limit the scope of the technology. In fact, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of methods and systems may not be described in detail. Furthermore, connection lines shown in various figures are intended to represent exemplary functional relationships and / or processes between various elements. In practical systems, many alternative or additional functional relationships or physical connections may exist.

[0068] This technology has been described with reference to specific exemplary embodiments. However, various modifications and changes can be made without departing from the scope of this technology. The description and drawings should be considered illustrative, not restrictive, and all such modifications are intended to be within the scope of this technology. Accordingly, the scope of the technology should be determined not merely by the specific embodiments described above, but by the general embodiments described and their legal equivalents. For example, the steps described in any embodiment of a method or process may be performed in any order unless otherwise explicitly stated, and are not limited to the explicit order presented in a particular embodiment. Furthermore, the components and / or elements described in any embodiment of a device may be assembled in various permutations or configured to operate in other ways to produce substantially the same results as in this technology, and are therefore not limited to the specific configurations described in a particular embodiment.

[0069] The benefits, advantages, and solutions to problems relating to specific embodiments have been described above. However, any benefit, advantage, solution to a problem, or any element that could produce or make more prominent any particular benefit, advantage, or solution should not be construed as an important, necessary, or essential feature or component.

[0070] The terms “comprises,” “comprising,” or any variation thereof are intended to refer to non-exclusive inclusion, so that a process, method, article, composition, or apparatus containing a list of elements does not include only the elements listed, but may also include other elements not expressly enumerated in such process, method, article, composition, or apparatus, and which are not inherent to them. In addition to those not specifically described, other combinations and / or modifications of the above-mentioned structures, arrangements, uses, proportions, elements, materials, or components used in the implementation of the Art may be modified or otherwise specifically adapted to a particular environment, manufacturing specification, design parameter, or other operating requirement without departing from the same general principles.

[0071] The Art has been described above with reference to exemplary embodiments. However, changes and modifications to the exemplary embodiments may be made without departing from the scope of the Art. These and other changes or modifications are intended to be within the scope of the Art as expressed in the following claims.

[0072] According to one embodiment, a control circuit adapted to control a heating element powered by a battery includes a memory configured to store known battery data including a first profile and a second profile; a fuel gauge circuit communicating with the memory and the battery, configured to determine the resistance of the battery according to the first and second profiles; a logic circuit connected to the fuel gauge circuit, configured to calculate a first power value based on the determined resistance; and a signal generator circuit responding to the logic circuit, configured to generate a control signal according to the calculated first power value, wherein the control circuit selectively connects the battery to the heating element according to the control signal.

[0073] In one embodiment, determining the resistance of a battery includes measuring the actual voltage of the battery, determining the battery capacity according to the measured actual voltage using a first profile, and determining the resistance of the battery according to the determined capacity using a second profile.

[0074] In one embodiment, the logic unit further calculates a first power based on a first resistance value of the heating element at the start time.

[0075] In one embodiment, the memory further includes a third profile that includes a relationship between the resistance of the heating element and time.

[0076] In one embodiment, the control circuit further includes a timer for measuring the elapsed operating time, which is measured from the start time.

[0077] In one embodiment, when the timer reaches a predetermined elapsed operating time, the logic unit calculates a new first power according to the second resistance value of the heating element and the third profile.

[0078] In one embodiment, the control circuit further includes a switch positioned between the battery and the heating element, the switch responding to a control signal to electrically connect the battery to the heating element.

[0079] In one embodiment, the first profile includes the relationship between the battery voltage value and the battery capacity value, and the second profile includes the relationship between the battery resistance value and the battery capacity value.

[0080] In one embodiment, the control signal includes a ratio of a predetermined target power to a calculated first power.

[0081] In another embodiment, a method for controlling the delivery of power from a battery to a heating element includes measuring the actual voltage of a battery; determining the capacity of the battery according to the measured actual voltage and first known battery data; determining the resistance of the battery according to the determined capacity and second known battery data; calculating a first power according to the determined resistance of the battery and the resistance of the heating element; calculating a ratio between a predetermined target power and the calculated first power; and electrically connecting the battery to the heating element according to the calculated ratio.

[0082] In one operation, the resistance of the heating element is the initial resistance value of the heating element when it is new.

[0083] In one operation, the first known battery data includes the relationship between voltage and capacity, and the second known battery data includes the relationship between battery resistance and capacity.

[0084] One operation further includes measuring the elapsed operating time and determining the resistance value of the heating element that has deteriorated over time, utilizing known heating element data and the elapsed operating time value.

[0085] In one operation, the resistance of the heating element is the determined resistance after degradation over time.

[0086] In yet another embodiment, a system for powering a heating element includes a battery configured to supply power to the heating element and a control circuit configured to control the delivery of power from the battery to the heating element according to a control signal, wherein the control signal is based on a calculated first power and a predetermined target power, and the calculated first power is based on the resistance of the heating element and the resistance of the battery.

[0087] In one embodiment, the control circuit includes a memory configured to store a first profile including a relationship between a battery voltage value and a battery capacity value, and a second profile including a relationship between a battery resistance value and a battery capacity value.

[0088] In one embodiment, the control circuit is further configured to measure the actual voltage of the battery and determine the actual capacity of the battery according to the measured actual voltage and a first profile.

[0089] In one embodiment, the control circuit is further configured to determine the battery's resistance according to the measured actual capacity of the battery and a second profile.

[0090] In one embodiment, the memory is further configured to store a third profile including a relationship between the resistance of the heating element and time.

[0091] In one embodiment, the control signal is the ratio of a predetermined target power to a calculated first power.

Claims

1. A control circuit that controls the amount of power supplied to the heating element, A rechargeable battery that supplies power to the heating element and the control circuit, A battery-powered heating device including, The aforementioned control circuit is A switch that operates to electrically connect and disconnect the rechargeable battery to the heating element, A signal generator circuit that generates a first signal for operating the switch, It includes a logic circuit connected to the signal generator circuit and providing a second signal to the signal generator circuit, The aforementioned logic circuit is A battery-powered heating device configured to provide the signal generator circuit with a second signal based on a first resistance value of the heating element at the start time when power is applied to the heating element, and a resistance value of the heating element selected based on a profile representing the relationship between time and the resistance value of the heating element.

2. A battery-powered heating device according to claim 1, The control circuit further includes a fuel gauge circuit that measures the voltage of the rechargeable battery and determines the capacity of the rechargeable battery from the measured voltage of the rechargeable battery and the relationship between the voltage and capacity value of the rechargeable battery, The logic circuit is configured to control the first signal by providing the second signal to the signal generator circuit based on the determined capacity of the rechargeable battery.

3. A battery-powered heating device according to claim 1 or 2, The control circuit further includes a flash memory containing the profile, and is a battery-powered heating device.

4. A battery-powered heating device according to any one of claims 1 to 3, It also includes a timer for measuring time intervals, The timer is a battery-powered heating device that measures the elapsed time from the start time.

5. A battery-powered heating device according to any one of claims 1 to 4, The logic circuit, after a predetermined time has elapsed from the start time, acquires a second resistance value of the heating element and provides the second signal based on the second resistance value to the signal generator circuit, thereby providing a battery-powered heating device.

Images