Control circuit and method for delivering power to a heating element

Abstract

The present invention is entitled "Control circuit and method for delivering power to a heating element". The present invention relates to a control circuit and a method for delivering power to a heating element. In various embodiments, the control circuit is suitable for controlling the power supplied by a battery to the heating element. The control circuit may include a memory and a circuit, the memory being used to store known data, and the circuit being configured to control the power delivery from the battery to the heating element based on measured parameters, calculated parameters and known data.

Description

Technical Field

[0001] The present invention relates to control circuits and methods for delivering power to heating elements. Background Art

[0002] Many electronic devices use batteries such as lithium-ion batteries to provide the main power supply to the electronic device. In some applications such as electronic cigarettes (also known as steam smoke devices, electronic cigarettes, pen-type steam cigarettes and nicotine vaporizers), the battery powers a heating element, which is used to heat a liquid to form a vapor. Some conventional systems use an open-loop heating method, which can cause the heating element to reach an undesirable and / or dangerous temperature. Alternatively, other conventional systems use a closed-loop heating method, but this method requires additional circuitry, which may increase the cost of the system, increase power loss, generate excessive heat, and / or cause delayed feedback of measured parameters (e.g., voltage, current). It is desirable to provide a stable power supply to the heating element to achieve optimal operation using a minimal circuit. Summary of the invention

[0003] The present invention relates to control circuits and methods for delivering power to heating elements.

[0004] The technical problem solved by the present invention is that conventional systems using open-loop heating methods may cause the heating element to reach undesirable and / or dangerous temperatures. Alternatively, conventional systems using closed-loop heating methods require additional circuitry, which may increase the cost of the system, increase power loss, generate excessive heat, and / or cause delayed feedback of measured parameters (e.g., voltage, current).

[0005] In various embodiments, the control circuit is adapted to control the power supplied by the battery to the heating element. The control circuit may include a memory and a circuit configured to control the power delivery from the battery to the heating element based on the measured parameters, the calculated parameters, and the known data.

[0006] According to one aspect, a control circuit suitable for controlling 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 connected to the memory and the battery and configured to determine the resistance of the battery based on the first profile and the second profile; a logic circuit connected to the fuel gauge circuit and configured to calculate a first power value based on the determined resistance; and a signal generator circuit responsive to the logic circuit and configured to generate a control signal based on the calculated first power value; wherein the control circuit selectively connects the battery to the heating element based on the control signal.

[0007] In one embodiment of the control circuit described above, determining the resistance of the battery includes: measuring an actual voltage of the battery; using a first profile to determine a capacity of the battery based on the measured actual voltage; and using a second profile to determine the resistance of the battery based on the determined capacity.

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

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

[0010] In one embodiment, the control circuit further comprises a timer for measuring an elapsed operating time; wherein: the elapsed operating time is measured from a start time; and when the timer reaches a predetermined elapsed operating time, the logic unit calculates a new first power based on: a second resistance value of the heating element; and a third profile.

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

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

[0013] According to another aspect, a method for controlling power delivery from a battery to a heating element includes: measuring an actual voltage of the battery; determining a capacity of the battery based on the measured actual voltage and first known battery data, wherein the first known battery data includes a relationship between a voltage value and a capacity value; determining a resistance of the battery based on the determined capacity and second known battery data, wherein the second known battery data includes a relationship between a resistance value and a capacity value of the battery; calculating a first power based on the determined resistance of the battery and the resistance of the heating element; calculating a ratio of a predetermined target power to the calculated first power; and electrically connecting the battery to the heating element based on the calculated ratio.

[0014] In one operation of the above method, the resistance of the heating element is one of: an initial resistance value of the heating element when the heating element is new; and a determined aged resistance.

[0015] In one operation, the method further includes: measuring an elapsed operating time; and determining an aged resistance value of the heating element, including: 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 to achieve optimal operation using minimal circuitry. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present technology may be more fully understood with reference to the detailed description when considered in conjunction with the following exemplary drawings.In the following drawings, similar reference numerals are used throughout to refer to similar elements and steps in the various drawings.

[0018] Figure 1 representatively illustrates an electronic system having a battery powered heating element according to an exemplary embodiment of the present technology;

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

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

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

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

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

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

[0025] Figure 6 is a flow chart for controlling power delivery from a battery to a heating element according to an exemplary embodiment of the present technology;

[0026] Figure 7 is an alternative flow chart for controlling power delivery from a battery to a heating element according to an exemplary embodiment of the present technology;

[0027] Figure 8 is a graph showing the relationship between heater power and battery capacity value when the PWM rate is 100%;

[0028] Fig. 9 is a graph showing an exemplary relationship between a PWM rate for supplying constant power to a heater element and a battery capacity value according to an exemplary embodiment of the present technology; and

[0029] Fig.10 According to the embodiment of the present technology, the Fig. 9 A graph showing the relationship between heater power and battery capacity value after adjusting the PWM rate in FIG. DETAILED DESCRIPTION

[0030] The present technology may be described in terms of functional block components and various processing steps. Such functional blocks may be implemented by any number of components configured to perform specified functions and achieve various results. For example, the present technology may 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 multiple functions. In addition, the present technology may be implemented in conjunction with any number of systems, and the systems are merely exemplary applications of the technology. In addition, the present technology may employ any number of conventional techniques to measure voltage, measure current, calculate the capacity of a battery, perform various mathematical calculations, store data, etc.

[0031] Methods and apparatus for power control circuits according to various aspects of the present technology may operate in conjunction with any suitable electronic system and / or device, such as consumer electronics, portable devices, battery-powered heating devices, etc. Figure 1 , the exemplary system 100 may include a heating element 120 that may be powered by a rechargeable battery 105, and a control circuit 110 to control the amount of power supplied to the heating element 120. For example, the system 100 may include an electronic cigarette that includes a vapor cartridge 125 containing a liquid 130. In an exemplary embodiment, the system 100 may also include a sensor 115 to detect when a user applies suction (i.e., puffs) to the electronic cigarette, which activates the heating element 120. The system 100 may also include a light emitting diode (LED) 135 to simulate a "burn" and / or provide a visual response to the suction.

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

[0033] The heating element 120 may include an electric heater, such as an infrared heater element, a photon 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 a doped ceramic, a "conductive" ceramic (such as, for example, molybdenum disilicide), carbon, graphite, a metal, a metal alloy, and a composite material made of a ceramic material, and / or a metallic material. Such composite materials may include doped ceramics or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable 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 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, and iron-containing alloys, as well as superalloys based on nickel, iron, cobalt, stainless steel, and iron-manganese-aluminum based alloys. In the composite material, the resistive material may optionally be embedded in, encapsulated or coated with the insulating material, or vice versa, depending on the kinetics of energy transfer and the desired external physicochemical properties.

[0034] The control circuit 110 controls and / or manages the functionality of the battery 105, the heating element 120, and the LED 135 based on various input signals, such as input signals from the sensor 115. The control circuit 110 may include an integrated circuit including various circuits and / or systems that operate together to provide desired outputs and / or control signals.

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

[0036] According to an exemplary embodiment, and 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 operate together to control or otherwise manage various functions of the system 100, such as controlling power to the heating element 120, battery management (e.g., charging cycle / discharging cycle), etc. The control circuit 110 can be formed as an integrated circuit on a single chip or 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 heating element 120 and the terminals of the battery 105, the switch operating to electrically connect the battery 105 to the heating element 120 and disconnect the battery from the heating element. The switch 200 may include any device suitable for providing a selective connection between two or more devices.

[0038] The switch 200 may include a transistor such as a field effect transistor (FET), which uses an electric field to control the electrical behavior of the device. There are many different implementations of field effect transistors. A field effect transistor may be a desirable implementation because it typically exhibits very high input impedance at low frequencies. The conductivity between the drain terminal and the source terminal is controlled by an electric field in the device, which is generated by a voltage difference between the body of the device and the gate.

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

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

[0041] The memory may also include a third profile 240 that includes known heater element data that provides a relationship between heater element resistance values ​​and time, such as in Figure 5A-5C The data shown in the graph of the third profile 240. The specific data contained in the third profile 240 can be determined by testing the heating element 120 in an environment that simulates the system 100 in which the heating element 120 will be used. Generally speaking, when power is applied to the heater element 120, the heater element has an initial resistance at time 0, and the heater element resistance can increase, decrease, or remain constant over time depending on its material properties. The third profile 240 can be implemented as a lookup table or any other suitable storage device that can be accessed by the logic circuit 215 and / or the fuel gauge circuit 205.

[0042] The memory 210 may be further configured to store a predetermined target power value “Power2”. The predetermined target power value “Power2” may vary depending on 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 rated power and maximum rated current of the heating element 120, and 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, the charging current of the battery, etc.

[0043] Memory 210 may be implemented as random access memory (RAM), read only memory (ROM), or non-volatile memory, such as flash memory. A particular memory implementation may be selected based on the particular 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, monitor and / or measure various battery characteristics, such as voltage, current, battery capacity (which may also be expressed as a state of charge (SOC) or relative state of charge (RSOC), as a percentage), the battery's operating mode (e.g., charging and discharging), state of health (SOH), etc. The fuel gauge circuit 205 may also generate various types of control signals, such as control signals for controlling charging and discharging, in response to received input signals and / or battery characteristics. The fuel gauge circuit 205 may include any number of suitable circuits and / or systems and may be implemented in any suitable manner, such as in the form of a large scale integrated (LSI) circuit.

[0045] According to an exemplary embodiment, the fuel gauge circuit 205 is configured to retrieve relevant data from the first profile 230 and utilize the relevant data to determine the capacity (RSOC) of the battery 105. For example, the fuel gauge circuit 205 may first use conventional voltage sensing methods and techniques to measure the actual voltage of the battery 105. The fuel gauge circuit 205 may then determine the battery capacity based on 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 the second profile 235. For example, a 15% RSOC corresponds to a resistance value 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 can be configured to perform various calculations, extract data from the memory 210, receive relevant data when it is related to the battery 105 and / or the heating element 120, and / or supply various control signals. For example, the logic circuit 215 can be connected to the fuel gauge circuit 205 and / or the memory 210. According to an exemplary embodiment, the logic circuit 215 can be further connected to the signal generator circuit 220 and provide a first control signal to the signal generator circuit. The logic circuit 215 may include any suitable device and / or system and may be implemented by using hardware, logic gates, etc.

[0048] According to an exemplary embodiment, the logic circuit 215 is configured to calculate a maximum power value “Power1”, where the maximum power value is described as Power1=V 2 / (R1+R2) (Equation 1), where V is the measured actual voltage of the battery 105, R1 is the determined resistance value of the battery 105, and R2 is the resistance value of the heating element 120.

[0049] The logic circuit 215 may be configured to retrieve 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 a starting resistance (a resistance value at time 0) or may be a resistance value during operation (a resistance value after time 0). Thus, the logic circuit 215 may select an appropriate resistance value based on the length of time that the heating element 120 has been operating.

[0050] According to various embodiments, the logic circuit 215 can further calculate the battery current I (i.e., I=V / R) based on the determined battery resistance R1 and the measured battery voltage. The logic circuit 215 can then confirm the RSOC value by utilizing a fourth profile (not shown) describing the relationship between the battery current and the RSOC value (e.g., stored in the memory 210).

[0051] The signal generator circuit 220 generates a second control signal to operate the switch 200. According to an exemplary embodiment, the signal generator circuit 220 can 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 can include a conventional circuit. The duty cycle of the PWM signal is the ratio of the predetermined target power "Power2" value to the calculated maximum power "Power1" (i.e., PWM=Power2 / Power1 (Equation 2)). Therefore, when the PWM signal is high, the switch 200 responds by closing (switch on), thereby connecting the battery 105 to the heating element 120. Conversely, when the PWM signal is low, the switch 200 responds by opening (switch off), thereby disconnecting the battery 105 from the heating element 120.

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

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

[0054] Control circuit 110 may then utilize the determined RSOC (from step 600) in conjunction with second profile 235 to determine battery resistance (605). For example, fuel gauge circuit 205 may retrieve from memory 210 a resistance value corresponding to the determined RSOC.

[0055] The control circuit 110 can then calculate the maximum power “Power1” (610) based on the measured actual voltage, the battery resistance value R1, and the heating element resistance value R2. For example, the logic circuit 215 can receive and / or retrieve the measured actual voltage of the battery, the battery resistance value R1, and the heating element resistance value R2 from the fuel gauge circuit and / or the memory 210.

[0056] The control circuit 110 may then calculate a PWM signal (615), where the PWM signal is defined as the predetermined power divided by the maximum power (i.e., Power2 / Power1). For example, the signal generator circuit 220 may receive the calculated maximum power “Power1” from the logic circuit 215 and may retrieve the predetermined target power value “Power2” from the memory 210.

[0057] The control circuit 110 may then operate the switch 200 according to the PWM signal (620). For example, if the PWM signal is 50%, then for a duty cycle of 1, the switch 200 is closed for half the time and open for the other half of the time. Similarly, if the PWM signal is 30%, then for a duty cycle of 1, the switch is closed for 30% of the time and open for 70% of the time.

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

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

[0060] Control circuit 110 may then utilize the determined RSOC (from step 700) in conjunction with second profile 235 to determine battery resistance (705). For example, fuel gauge circuit 205 may retrieve from memory 210 a resistance value corresponding to the determined RSOC.

[0061] The control circuit 110 can then calculate the maximum power “Power1” (710) based on the measured actual voltage, the battery resistance value R1, and the heating element resistance value R2. For example, the logic circuit 215 can receive and / or retrieve the measured actual voltage of the battery, the battery resistance value R1, and the heating element resistance value R2 from the fuel gauge circuit and / or the memory 210.

[0062] Control circuit 110 may then calculate a PWM signal (715), where the PWM signal is defined as a predetermined power divided by a maximum power (i.e., Power2 / Power1). For example, signal generator circuit 220 may receive the calculated maximum power “Power1” from logic circuit 215 and may retrieve a predetermined target power value “Power2” from memory 210.

[0063] The control circuit 110 may then operate the switch 200 according to the PWM signal (720). For example, if the PWM signal is 50%, then for a duty cycle of 1, the switch 200 is closed for half the time and open for the other half of the time. Similarly, if the PWM signal is 30%, then for a duty cycle of 1, 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 of time, such as 100ms, the logic circuit 215 can retrieve a new resistance value R2 corresponding to the elapsed time and calculate a new maximum power. Since the heating element resistance R2 increases over time, the new maximum power value will be less than the value calculated at time 0. The signal generator circuit 220 can then use the new maximum power value to update the PWM ratio, and the signal generator circuit 220 will operate the switch 200 accordingly.

[0065] This operation may be used if the resistance characteristics of the heater element 120 change (increase or decrease) over time, such as Figure 5A and Figure 5B As shown. 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", where the variable "R2" in the above equation 1 is the updated heating element resistance value corresponding to the elapsed time. In contrast, if the heating element 120 exhibits a stable characteristic, such as Figure 5C As shown, the above equation 1 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 the battery 105 to the heating element 120 is not stable across various battery capacity values ​​(e.g., Figure 8 However, embodiments of the present technology adjust the PWM rate during operation (e.g., as Fig. 9 ), and thus, the battery 105 provides a stable power supply to the heating element 120 (e.g., as Fig.10 shown).

[0067] In the above description, the technology has been described in conjunction with specific exemplary embodiments. The specific embodiments shown and described are used to demonstrate the technology and its best mode, and are not intended to limit the scope of the technology in any way. In fact, for the sake of brevity, the conventional manufacturing, connection, preparation and other functional aspects of the method and system may not be described in detail. In addition, the connecting lines shown in multiple figures are intended to represent exemplary functional relationships and / or steps between various elements. There may be multiple alternative or additional functional relationships or physical connections in a practical system.

[0068] The technology has been described in conjunction with specific exemplary embodiments. However, various modifications and changes may be made without departing from the scope of the present technology. The description and drawings are considered in an exemplary and non-restrictive manner, and all such modifications are intended to be included within the scope of the present technology. Therefore, the scope of the technology should be determined by the general embodiments described and their legal equivalents, rather than only by the above-mentioned specific examples. For example, unless otherwise explicitly stated, the steps listed in any method or process embodiment may be performed in any order, and are not limited to the explicit order presented in the specific examples. In addition, the components and / or elements listed in any device embodiment may be assembled in a variety of arrangements or otherwise configured for operation to produce substantially the same results as the present technology, and are therefore not limited to the specific configurations set forth in the specific examples.

[0069] The above has described benefits, other advantages and solutions to problems with respect to specific embodiments. However, any benefit, advantage, solution to problems, or any element that makes any specific benefit, advantage or solution appear or become more obvious should not be construed as a critical, required or essential feature or component.

[0070] The terms "comprises," "comprising," or any variation thereof, are intended to refer to a non-exclusive inclusion, such that a process, method, article, composition, or apparatus that includes a list of elements includes not only those enumerated elements, but may also include other elements not expressly listed or inherent to such process, method, article, composition, or apparatus. Other combinations and / or modifications of the above-described structures, arrangements, applications, proportions, elements, materials, or components used in the implementation of the present technology, except for those not specifically cited, may be varied or otherwise specially adapted to a specific environment, manufacturing specifications, design parameters, or other operating requirements without departing from its general principles.

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

[0072] According to one aspect, a control circuit suitable for controlling 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 connected to the memory and the battery and configured to determine the resistance of the battery based on the first profile and the second profile; a logic circuit connected to the fuel gauge circuit and configured to calculate a first power value based on the determined resistance; and a signal generator circuit responsive to the logic circuit and configured to generate a control signal based on the calculated first power value; wherein the control circuit selectively connects the battery to the heating element based on the control signal.

[0073] In one embodiment, determining the resistance of the battery includes: measuring an actual voltage of the battery; utilizing a first profile to determine a capacity of the battery based on the measured actual voltage; and utilizing a second profile to determine the resistance of the battery based on the determined capacity.

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

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

[0076] In one embodiment, the control circuit further comprises a timer to measure an elapsed operating time, wherein the elapsed operating time is measured from a start time.

[0077] In one embodiment, when the timer reaches a predetermined elapsed operating time, the logic unit calculates a new first power based on: 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, wherein the switch is responsive to the control signal and electrically connects the battery to the heating element.

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

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

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

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

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

[0084] In one operation, the method further includes: measuring an elapsed operating time; and determining an aged resistance value of the heating element, including: utilizing known heating element data and the elapsed operating time value.

[0085] In one operation, the resistance of the heating element is determined as an aged resistance.

[0086] According to yet another aspect, a system for powering a heating element comprises: a battery configured to provide power to the heating element; and a control circuit configured to control power delivery from the battery to the heating element based on 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: a resistance of the heating element; and a 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 an actual voltage of the battery; and determine an actual capacity of the battery based on the measured actual voltage and the first profile.

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

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

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

Claims

1. A control circuit suitable for controlling a heating element powered by a battery, characterized in that include: a memory configured to store known battery data including a first profile and a second profile; a fuel gauge circuit in communication with the memory and the battery and configured to determine a resistance of the battery based on the first profile and the second profile; a logic circuit connected to the fuel gauge circuit and configured to calculate a first power value indicative of a maximum power of the battery based on the determined resistance, the actual voltage of the battery, and a first resistance value of the heating element at a starting time; and a signal generator circuit responsive to the logic circuit and configured to generate a control signal based on the calculated first power value; The control circuit selectively connects the battery to the heating element according to the control signal.

2. The control circuit according to claim 1, characterized in that Determining the resistance of the battery includes: measuring the actual voltage of the battery; determining the capacity of the battery based on the measured actual voltage using the first profile; and The resistance of the battery is determined based on the determined capacity using the second profile.

3. The control circuit according to claim 1, characterized in that: The memory further includes a third profile including a relationship between an elapsed time from the start of heating and a resistance value of the heating element.

4. The control circuit according to claim 3 is further characterized in that: including a timer for measuring elapsed operating time; wherein: The elapsed operating time is measured from the start time; and When the timer reaches a predetermined elapsed operating time, the logic circuit calculates a new first power based on: a second resistance value of the heating element; and The third profile.

5. The control circuit according to claim 1, further characterized in that: A switch is included that is positioned between the battery and the heating element, wherein the switch is responsive to the control signal and electrically connects the battery to the heating element.

6. The control circuit according to claim 1, characterized in that: The first profile includes a relationship between a battery voltage value and a battery capacity value; and The second profile includes a relationship between a battery resistance value and the battery capacity value.

7. The control circuit according to claim 1, characterized in that: The control signal includes a ratio of a predetermined target power to the calculated first power.

8. A method for controlling the delivery of power from a battery to a heating element, characterized in that include: measuring the actual voltage of the battery; determining the capacity of the battery according to the measured actual voltage and the first known battery data; determining a resistance of the battery based on the determined capacity and second known battery data; calculating a first power based on the determined resistance of the battery and the resistance of the heating element; calculating a ratio of a predetermined target power to the calculated first power; as well as The battery is electrically connected to the heating element according to the calculated ratio.

9. The method according to claim 8, characterized in that The resistance of the heating element is an initial resistance value of the heating element when the heating element is new; and The first known battery data includes a relationship between a voltage value and a capacity value; and The second known battery data includes a relationship between a resistance value of the battery and the capacity value.

10. The method according to claim 8, characterized in that Also includes: measuring the elapsed operating time; as well as Determining the aging resistance value of the heating element includes: Using known heating element data and an elapsed operating time value, the resistance of the heating element is the determined aged resistance.

Images