Patent Publication Number: US-2023148678-A1

Title: Electrical System for an Aerosol Generating Device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/EP2021/059564, filed Apr. 13, 2021, published in English, which claims priority to European Application No. 20170908.6 filed Apr. 22, 2020, the disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electrical system. In particular, the electrical system is used within an aerosol generating device. 
     BACKGROUND 
     Aerosol generating devices, such as electronic cigarettes, often include an electrical system with a battery for supplying power to a heating element. Within such systems, a known issue is that the battery may enter a state of deep discharge. For example, when a lithium-ion battery cell enters a state of deep discharge, internal degradations known as copper electrode dissolution may occur within the battery cell and short circuits may be created between cell electrodes. When such a battery is recharged, the cell is liable to overheating and thermal runaway, which can potentially pose a safety hazard. 
     There are many other battery conditions which carry potential safety risks and the operation of batteries displaying such conditions should generally be avoided. 
     An object of the present invention is to improve the safety of electrical systems including a battery within aerosol generating devices. 
     SUMMARY 
     According to an aspect of the invention, there is provided an aerosol generating device comprising an electrical system, the electrical system comprising: a battery; and a control circuitry, wherein the control circuitry is configured to monitor a status of the battery during a discharge operation of the battery and set a flag if a fault in the battery is detected, the flag indicating that the battery is not in an operating condition, wherein the control circuitry is configured to check the flag when the electrical system is connected to an external power supply, wherein the control circuitry is configured to enable charging of the battery based on the flag, wherein the battery and the control circuitry are connectable to the external power supply via a first electrical path and a second electrical path respectively such that power can be independently supplied to the battery and the control circuitry, and wherein the electrical system is configured to supply power to the control circuitry from the external power supply via the second electrical path when the electrical system is connected to the external power supply, such that the flag can be checked without charging the battery. 
     In this way, it is possible to prevent a damaged or otherwise degraded battery from being charged, thereby improving the safety of an electrical system. 
     Existing strategies for responding to battery faults involve monitoring the charging curve of a battery to detect deep discharge or other hazardous battery conditions. However, such strategies will only detect a fault after charging of the cell has commenced. Thus, it is possible that power has already been supplied to a battery that has an internal short circuit or other fault. In the present invention, the control circuitry monitors the battery during discharge operation, for example when powering a heating element during a vaping operation of an aerosol generating device, and sets a flag within the control circuitry if a fault is detected. When the electrical system is subsequently connected to an external power supply with the intention of charging the aerosol generating device, the control circuitry checks the flag and only enables charging of the battery if the flag is present. As a result, charging of the battery is prevented from commencing if there is a fault in the battery, thereby ensuring that a battery in a hazardous condition does not receive any electrical power. 
     Moreover, the configuration of the electrical system is such that the control circuitry can be powered to check the flag without also supplying power to a possibly defective battery. In comparison, within known electrical systems, and in particular for aerosol generating devices, supplying power to the control circuitry also begins the charging process and it would not be possible to check the flag without also supplying power to a potentially hazardous battery. 
     Detecting a fault in the battery may comprise measuring the voltage of the battery with respect to time. A fault may be determined to have occurred when the voltage falls below a threshold voltage. In one example, for a lithium-ion battery, 3.0V may be a typical voltage at which the battery is considered to be discharged, 2.8V may be a typical threshold below which the battery is considered to have a fault, and 2.5V may be a typical voltage at which the battery has internal cell damage which cannot be recovered. However, the skilled person will appreciate that the threshold voltage will vary according to the type of battery and specific cell chemistry. 
     Alternatively, or additionally, detecting a fault in the battery may comprise monitoring the temperature of the battery. If the temperature of the battery exceeds a threshold temperature, the battery may be determined to have a fault. The skilled person will appreciate that the threshold temperature will vary according to the type of battery and the cell chemistry. 
     Preferably, the electrical system further comprises a battery charger circuitry, wherein the control circuitry is configured to send a signal to the battery charger circuitry based on the flag, the signal indicating that charging is enabled, and wherein the battery charger circuitry is configured to charge the battery when the signal indicating that charging is enabled is received from the control circuitry. In this way, the use of a battery charger circuitry ensures that power is efficiently and reliably supplied to the battery, whilst the signal receipt requirement ensures that power is not supplied to a damaged or degraded battery. 
     Preferably, charging the battery comprises supplying power to the battery along the first electrical path. 
     Preferably, the control circuitry is configured to modify the flag upon detecting that the battery has been replaced. In this way, a new battery that is not in a potentially dangerous operating condition is not prevented from being charged. 
     Preferably, the electrical system further comprises a voltage regulator for supplying power to the control circuitry. A voltage regulator has the ability to generate and maintain a constant current or voltage output. 
     In one example, the electrical system may be connectable to the external power supply by a USB connection. In particular, the voltage regulator and the battery charger circuitry may be connectable to the external power supply by the USB connection. 
     Preferably, the electrical system is configured to supply power to the control circuitry from the battery when the electrical system is not connected to the external power supply. 
     Preferably, the electrical system further comprises a heating element, and the control circuitry is configured to switch off power supply from the battery to the heating element when a fault is detected in the battery. In this way, continued operation of a damaged or otherwise degraded battery is avoided. 
     Preferably, the control circuitry is configured to switch off power supply from the battery to the heating element when the electrical system is connected to the external power supply. 
     Preferably, the electrical system further comprises a fuse, wherein the control circuitry is configured to activate the fuse when the fault detected in the battery is deemed to be non-recoverable, and wherein activating the fuse irreversibly disables charging of the battery. 
     Preferably, the control circuitry is further configured to activate the fuse when a threshold amount of time has elapsed since the flag was set and the fault in the battery is detected as still existing. 
     According to another aspect of the invention, there is provided a method of operating an aerosol generating device comprising an electrical system, the method comprising: monitoring, using a control circuitry, the status of a battery in the electrical system during a discharge operation of the battery; in response to detecting a fault in the battery, setting a flag indicating that the battery is not in an operating condition, wherein the battery and the control circuitry are connectable to an external power supply by a first electrical path and a second electrical path respectively such that power can be independently supplied to the control circuitry and the battery; in response to detecting that the electrical system has been connected to the external power supply, supplying power from the external power supply via the second electrical path to check the flag without charging the battery; and enabling charging of the battery based on the flag. 
     Preferably, the method further comprises sending a signal from the control circuitry to a battery charger circuitry indicating that charging is enabled; and in response to receiving the signal indicating that charging is enabled, charging the battery. 
     Preferably, the method further comprises clearing the flag upon detecting that the battery has been replaced. 
     Preferably, the method further comprises: supplying power to the control circuitry from the battery when the electrical system is not connected to the external power supply. 
     Preferably, the method further comprises: providing a heating element in the electrical system; switching off power supply to the heating element when a fault is detected in the battery; and/or switching off power supply from the battery to the heating element when the electrical system is connected to the external supply. 
     Preferably, the method further comprises: activating, using the control circuitry, a fuse in the electrical system when the fault detected in the battery is deemed to be non-recoverable, wherein activating the fuse irreversibly disables charging of the battery. 
     Preferably, the method further comprises: in response to detecting that a threshold amount of time has elapsed since the flag was set and that the fault in the battery still exists, activating, using the control circuitry, the fuse. 
     According to another aspect of the invention there is provided a non-transitory computer-readable memory medium comprising executable instructions which, when executed on a computer or processor in an aerosol generating device comprising an electrical system, cause the computer or processor to undertake steps comprising: monitoring, using a control circuitry, the status of a battery in the electrical system during a discharge operation of the battery; in response to detecting a fault in the battery, setting a flag indicating that the battery is not in an operating condition, wherein the battery and the control circuitry are connectable to an external power supply by a first electrical path and a second electrical path respectively such that power can be independently supplied to the control circuitry and the battery; in response to detecting that the electrical system has been connected to the external power supply, supplying power from the external power supply via the second electrical path to check the flag without charging the battery; and enabling charging of the battery based on the flag. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are now described, by way of example, with reference to the drawings, in which: 
         FIG.  1    is a block diagram of a prior art electrical system for an aerosol generating device; 
         FIG.  2    is a block diagram of an electrical system for an aerosol generating device in an embodiment of the invention; 
         FIG.  3 A  is a block diagram of the electrical system depicted in  FIG.  2   , illustrating a first electrical path for supplying power from an external power supply to a battery and a second electrical path for supplying power from the external power supply to a control circuitry; 
         FIG.  3 B  is a block diagram of the electrical system depicted in  FIG.  2   , illustrating a third electrical path for supplying power from the battery to the control circuitry during a discharge operation of the battery; 
         FIG.  4    is a flowchart showing method steps for operation of an electrical system for an aerosol generating device in an embodiment of the invention; 
         FIG.  5    is a flowchart showing further method steps for operation of the electrical system; and 
         FIG.  6    is a block diagram of an electrical system for an aerosol generating device in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a prior art electrical system  2  for an aerosol generating device. The electrical system  2  comprises a battery  4 , a control circuitry  6 , a battery charging circuitry  8 , a power connector  10 , a heating element  12 , and a switch  14 . 
     In use, when the electrical system  2  is connected via the power connector  10  to an external power supply, the battery charging circuitry  8  delivers electrical power to wake up the control circuitry  6 . However, as the battery  4  and the control circuitry  6  are connected in parallel and powered directly by the battery charging circuitry  8 , the battery  4  also receives electrical power and begins charging. Hence, utilising any function of the control circuitry  6  also results in the battery  4  receiving electrical power. 
       FIG.  2    shows an electrical system  20  for an aerosol generating device in an embodiment of the invention. The electrical system comprises a battery  22 , a control circuitry  24 , a battery charging circuitry  26 , a USB connector  28 , a voltage regulator  30 , a heating element  32  and a switch  34 . 
     The USB connector  28  is connectable to an external power supply. The skilled person will appreciate that the USB connector  28  may be substituted for another suitable form of power connector, such as any AC power plug for connecting to primary alternating current (AC) power supply in a building, or any DC power plug for supplying direct current (DC) power. 
     As illustrated in  FIG.  3 A , electricity may be supplied from the USB connector  28  to the battery  22  along a first electrical path  36 . The first electrical path  36  runs from the USB connector  28  to the battery  22  via the battery charging circuitry  26 . Electricity may also be supplied from the USB connector  28  to the control circuitry  24  along a second electrical path  38 . The second electrical path runs from the USB connector  28  to the control circuitry  24  via the voltage regulator  30 . The first electrical path  36  and the second electrical path  38  are configured as separate, distinct electrical paths. Hence, when the USB connector  28  is connected to the external power supply, electricity may be supplied along the second electrical path  38  to power the control circuitry  24  without also supplying power to the battery  22 . As used herein, the term ‘electrical path’ refers to a component suitable for transmitting electrical power by the conduction of electrons, such as a wire, cable or power line. 
     As illustrated in  FIG.  3 B , a third electrical path  39  connects the battery  22  to the control circuitry  24  via the voltage regulator  30 . The battery  22  may be a lithium-ion battery, a nickel cadmium battery, a nickel-metal hydride battery, a lead-acid battery, or any other type of rechargeable battery. 
     In use, the voltage regulator  30  either receives power from the external power supply (via the USB connector  28 ), or from the battery  22 . The voltage regulator  30  can then supply electricity to the control circuitry  24  to wake up and power the control circuitry  24 . The voltage regulator  30  is configured to power the control circuitry  24  with power from the USB connector  28  when the electrical system  20  is connected to the external power supply (i.e. power is supplied along the second electrical path  38 ), and configured to power the control circuitry  24  with power from the battery  22  otherwise (i.e. power is supplied along the third electrical path  39 ). 
     The voltage regulator  30  has the ability to generate and maintain a constant current or voltage output. It will be appreciated that, in alternative examples, the voltage regulator  30  may instead comprise a switch or other mechanism that allows the supply of electrical current to be controlled and/or regulated and directed along different electrical paths. 
     In this example, the control circuitry  24  is a microcontroller unit (MCU) and is used to control operation of the electrical system  20 . The MCU includes one or more CPUs (processor cores) along with memory and programmable input/output peripherals. In other examples, the control circuitry  24  may comprise a separate microprocessor, memory, and input/output devices. 
     The control circuitry  24  is configured to monitor the status of the battery  22  during a discharge operation of the battery  22  and control one or more aspects of the electrical system based on the status of the battery  22 . The term ‘discharge operation’ of the battery refers to the situation wherein the battery  22  is being used as power source to supply power to an electrical load or electrical component within the electrical system  20 . Monitoring the status of the battery  22  may comprise monitoring one or more properties or characteristics of the battery  22 , such as temperature, voltage or current, in order to detect a fault or abnormality within the battery  22 . 
     For example, a fault may result from the battery  22  entering into a state of deep discharge leading to internal degradations of the battery, e.g. a short circuit. This may be detected by measuring the battery  22  voltage with respect to time, and determining when the voltage falls below a threshold voltage. The threshold voltage will vary according to the type of battery and specific cell chemistry. However, as an example, for a lithium-ion battery, 3.0V may be a typical voltage at which the battery is considered to be discharged, 2.8V may be a typical threshold below which the battery is considered to have a fault, and 2.5V may be a typical voltage at which the battery has internal cell damage which cannot be recovered. This internal damage is often referred to as copper (foil) dissolution. 
     A fault condition may also be determined by monitoring the temperature of the battery  22 . A temperature sensor  27  may be used to measure the temperature of the battery. If the battery is operating abnormally, the temperature is likely to be high. Thus, if the temperature is detected to exceed a threshold temperature, the battery  22  may be determined to have a fault. Again, the threshold temperature will vary according to the type of battery and the cell chemistry. 
     A further example of detecting a fault may comprise detecting a battery capacity loss. Capacity loss (or capacity fading) is a phenomenon observed during rechargeable battery usage where the amount of charge a battery can deliver at the rated voltage decreases with use. For example, when the battery capacity fade exceeds approximately 60%-70%, the battery may be considered to be too aged/damaged, and thus considered to have a fault. 
     In this case, the electrical system  20  is situated within an aerosol generating device, and the discharge operation refers to an aerosol generating operation (or vaping operation) wherein the battery  22  is providing power to the heating element  32 . However, the skilled person will appreciate that the electrical system  20  may be used within alternative devices, and the heating element  32  may be substituted for other electrical components. 
     The control circuitry  24  is configured to set a flag in a data storage portion  25  of the control circuitry  23  when a fault is detected in the operating status of the battery  22 . The data storage portion  25  may comprise volatile or non-volatile memory, or may comprise long-term storage. The flag provides an indication that a fault has been detected and that the battery  22  is not in an operating condition. 
     In this example, the flag is a form of status register set in an EEPROM (electrically erasable programmable read-only memory) of the MCU  24  and records the condition of a calculation performed by the MCU  24 . Typically, a flag is defined as a 1 bit data in EEPROM; however, the number of bits may be increased to indicate the specific type of fault that has been detected. 
     The control circuitry  24  may also be configured to open the switch  34  when a fault is detected in the battery  22 , thereby cutting off the supply of electricity to the heating element  32  and improving the safety of the aerosol generating device. 
     In one example, the electrical system  20  may further comprise a data line connecting the control circuitry  24  to the electrical system  20  which is configured to provide voltage information to the control circuitry  24 . 
     In order to charge the battery  22 , the electrical system  20  of the aerosol generating device may be connected to an external power supply by the USB connector  28 . The voltage regulator  30  receives power from the USB connector  28  and generates a CC (constant current) output which is used to wake up the control circuitry  24  by the supply of electricity along the second electrical path  38 . As the battery  22  is connected to the USB connector  28  by the first electrical path  36 , which is separate to the second electrical path  38 , the control circuitry  24  can be powered without also charging the battery  22 . 
     In response to being powered up by the voltage regulator  30  when connected to an external power supply, the control circuitry  22  is configured to check the flag. If the flag is present, the control circuitry  24  will not enable charging of the battery  22 . If the flag is cleared or not present, the control circuitry  24  will enable charging of the battery  22 . 
     Enabling charging of the battery  22  comprises sending a signal to the battery charging circuitry  26 , wherein the signal indicates that charging of the battery  22  is enabled. The battery charging circuitry  26  is configured to only charge the battery  22  when the charging enabled signal has been received from the control circuitry  24 . Charging of the battery  22  comprises supplying power along the first electrical path  36  to the battery  22 . The battery charging circuitry  26  will not charge the battery  22  if a signal has not been received. Hence, the configuration ensures that the charging process cannot begin if the battery  22  has a detected fault, thereby improving the safety of the aerosol generating device. This method of operation is facilitated by the separate electrical paths  36 ,  38  for the battery  22  and control circuitry  24  respectively which allow the control circuitry  24  to be powered to check the flag without also charging the battery  22 . 
     In this example, the battery charging circuitry  26  is a battery charger IC (integrated circuit). 
     For other general purposes, the control circuitry  24  may be configured to switch off power supply from the battery  22  to the heating element  32  when the electrical system  20  is connected to an external power source through the USB connector  28 . This may be achieved by opening the switch  34 . Moreover, the control circuitry  24  may be configured to clear the flag if the control circuitry  24  detects that the battery  22  has been replaced. 
       FIGS.  4  and  5    illustrate a method of operation for an electrical system  20  of an aerosol generating device in an embodiment of the invention. 
     Referring to  FIG.  4   , the method commences at step  40  when the aerosol generating device enters into a vaping or aerosol generating mode of operation. During the vaping mode of operation, the battery  22  is used as a power source to supply electrical power to the heating element  32 . The battery also supplies electricity along the third electrical path  39  to power the control circuitry  24 . 
     At step  42 , the control circuitry  24  monitors the status of the battery  22 . For example, the control circuitry  24  may monitor the battery  22  voltage over time in order to detect a deep discharge state. If no fault is detected, the monitoring and vaping operation continues. 
     If a fault is detected, the switch  34  is opened and the supply of power from the battery  22  to the heating element  32  is stopped so that the aerosol generating device ends its vaping operation. In addition, at step  46 , the control circuitry  24  sets a flag in the control circuitry  24  which indicates that the battery  22  is not in an operating condition. 
     Referring to  FIG.  5   , the method continues at step  48  when the aerosol generating device is connected to an external power supply by the USB connector  28 , with the intention of charging the battery  22  within the aerosol generating device. 
     Upon being connected to an external power supply, at step  50 , a CC output is generated by the voltage regulator  30  and supplied to the control circuitry  24  along the second electrical path  38 . As the first electrical path  36  and the second electrical path  38  comprises separate conductions paths, the control circuitry  24  can be woken and powered without supplying power to the battery  22 . 
     At step  52 , when the control circuitry  24  has been woken, the control circuitry  24  checks the flag. 
     If the flag is cleared or not present, the method continues at step  54  and charging of the battery  22  is enabled. At step  56 , the control circuitry  24  sends a signal to the battery charging circuitry  26  indicating that charging of the battery  22  is enabled. At step  58 , when the battery charging circuitry  26  receives the signal indicating that charging is enabled, the battery charging circuitry  26  proceeds to charge the battery  22  by supplying the power along the first electrical path  36 . 
     Alternatively, if the flag is not cleared at step  52 , the method continues at step  60  and charging of the battery is not enabled  60 . 
       FIG.  6    shows an electrical system  70  according to another embodiment of the invention. The electrical system  70  comprises corresponding features to those described with reference to  FIGS.  2  to  5   , and is configured to operate substantially in line with the method of  FIGS.  4  and  5    under certain conditions as described below. For ease of reference, however, several of the previously described connections and features have been omitted from  FIG.  6   . 
     Nonetheless, the skilled person will appreciate that the omitted features, such as the heating element  32 , may be used in conjunction with the additional features of this embodiment. 
     The electrical system  70  differs from the previous embodiment in that the electrical system  70  further comprises a fuse  72  for disabling charging of the battery  22 . The fuse  72  is present in addition to the previously described flag that may be set in the control circuitry  24  for disabling charging of the battery  22 . That is, the electrical system  70  utilises both hardware and software means for disabling charging of the battery  22  when a fault is detected in the battery  22 . 
     In particular, the previously described flag mechanism provides a first level of protection for preventing charging of the battery  22  when a fault is detected in the battery  22 , wherein the fault is caused by a battery condition that is deemed as being (potentially) recoverable. The fuse  72  provides a second level of protection for preventing charging of the battery  22  when a fault is detected in the battery  22 , wherein the fault is caused by a battery condition that is deemed as not being recoverable. 
     Example damages to the battery  22  that may be deemed as non-recoverable include internal short circuits. For example, as previously discussed, short circuits may result from the battery  22  entering into a state of deep discharge leading to internal degradations of the battery  22 . This may be detected by measuring the battery  22  voltage with respect to time, and determining when the voltage falls below a threshold voltage. Another indication of permanent, non-recoverable damage is the detection of voltage drops during the charging process. Such voltage drops indicate that the battery  22  has internal short-circuits. 
     On the other hand, an example of damage to the battery  22  that may be deemed as recoverable are capacity losses due to lithium plating. Lithium plating occurs under strenuous or sub-optimal charging conditions. Such losses of capacity may be recovered by preventing operation of the battery  22  for a period of time, e.g. several days, or performing one or more charging cycles and monitoring the capacity evolution over time. However, under some circumstances, capacity losses due to lithium plating may not be recoverable, for example if the internal damages are too severe. 
     In this embodiment of the invention, if a non-recoverable fault condition of the battery  22  is detected, such as the defection of voltage drops during charging or the detection that the battery  22  has entered a state of deep-discharge, the fuse  72  is activated by the control circuitry  24  such that charging of the battery  22  is permanently disabled. 
     Otherwise, if a fault condition of the battery  22  is detected that is not deemed to be non-recoverable, e.g. a capacity loss of the battery  22  is detected wherein the capacity loss is above a threshold amount, the electrical system  70  operates according to the previously described embodiment. That is, a flag is set indicating that the battery  22  is not in an operating condition, thereby preventing charging of the battery  22  whilst the flag is present. 
     However, after a period of time has elapsed, if the fault condition is detected to still exist the damage to the battery  22  may be deemed as being non-recoverable. In this case, the fuse  72  is activated by the control circuitry  24  such that charging of the battery  22  is permanently disabled. For example, the fuse  72  may be activated if, after a threshold amount of time has elapsed, the capacity of the battery  22  remains below a threshold capacity, e.g. less than 50 to 40% of nominal capacity. The control circuitry  24  may comprise a timer configured to monitor the elapsed time or, alternatively or additionally, the control circuitry  24  may estimate the elapsed time by monitoring the voltage evolution of the battery  22 . 
     As will be appreciated by the skilled person, the fuse  72  is a physical component that is configured to break if the current exceeds a predetermined level. For example, the fuse  72  may consist of a strip of wire that is configured to melt above the predetermined level of current. In particular, the fuse  72  may comprise a copper track with a narrower central portion, as illustrated in  FIG.  6   . 
     In the specific implementation of the electrical circuit  70  illustrated in  FIG.  6   , the electrical system  70  comprises an I/O line  74 , a transistor  76  (e.g. an NPN transistor), an enable line  78 , resistors  80 , and positive supply voltages V cc . The I/O line  74  extends from the control circuitry  24  to the transistor  74 . A first positive supply voltage V cc  is connected to the I/O line  74  via a first resistor  80 . The transistor  76  is connected to the fuse  72  and a second positive supply voltage V cc . The fuse  72  is connected to the charging circuitry  26  via the enable line  78 . A third positive supply voltage V cc  is connected to the enable line  78  via a second resistor  80 . 
     When a fault is detected in the battery  22  that is deemed as being non-recoverable, or a threshold amount of time has elapsed since a flag has been set, the control circuitry  24  is configured to send a signal along the I/O line  74  to turn the transistor “ON” such that a maximum current flows through the fuse  72 . In this way, the fuse  72  is blown (i.e. activated) and the enable line  78 , which is connected to the transistor  76  via a portion of the fuse  72 , provides a control signal (e.g. set to high) to the charging circuitry  26  which permanently disables charging of the battery  22 . 
     Of course, the skilled person will appreciate the specific configuration of the electrical system  70  including the fuse  72  illustrated in  FIG.  6    is an exemplary configuration, and various modifications falling within the scope of the claims may be made to the electrical system  70 .