PATENT DOCUMENT

Publication Number: US-9831701-B2
Application Number: US-201615048329-A
Country: US
Kind Code: B2

Title: Monitoring a battery in a portable electronic device

Abstract:
The disclosed embodiments provide a system that monitors a battery in a portable electronic device. During operation, the system monitors a state of charge of the battery while the battery is powering the portable electronic device. Next, when the state of charge of the battery reaches a predetermined reserve capacity, the system monitors a voltage of the battery. Then, when the monitored voltage of the battery reaches a predetermined termination voltage, the system puts the portable electronic device into a low power usage state.

Claims:
What is claimed is: 
     
       1. A method for monitoring a battery of an electronic device, the method comprising:
 monitoring a voltage of a battery powering an electronic device; 
 reducing power drawn by the electronic device responsive to satisfaction of a first criteria, the first criteria comprising whether a plurality of transient voltage-dips below a predetermined threshold voltage are detected; and 
 further reducing power drawn by the electronic device responsive to satisfaction of a second criteria, the second criteria comprising whether a number of transient voltage-dips below the predetermined threshold voltage per unit time exceeds a predetermined value, 
 wherein the predetermined threshold voltage is greater than a brownout voltage. 
 
     
     
       2. The method of  claim 1 , further comprising:
 determining that a predetermined termination voltage of the battery has been reached responsive to satisfaction of a third criteria, the third criteria comprising at least one of, whether a steady state voltage below the predetermined termination voltage has been measured, and whether a persistence voltage below the predetermined termination voltage has been measured; and 
 upon such determination, placing the electronic device into at least one of a shutdown state and a hibernation state, 
 wherein the predetermined termination voltage is greater than the brownout voltage. 
 
     
     
       3. The method of  claim 2 , the third criteria further comprising at least one of whether a number of transient voltage-dips below the predetermined termination voltage per unit time exceeds a predetermined value, whether a number of transient voltage-dips below the predetermined termination voltage exceeds a predetermined number, and whether a duration of at least one transient voltage-dip below the predetermined termination voltage exceeds a predetermined duration. 
     
     
       4. The method of  claim 3 , wherein the predetermined termination voltage is equal to the predetermined threshold voltage. 
     
     
       5. The method of  claim 4 , wherein the predetermined termination voltage is user selectable. 
     
     
       6. The method of  claim 1 , wherein reducing power drawn by the electronic device comprises at least one of reducing a brightness of a screen, reducing a volume of a speaker, or shutting down a wireless communication device. 
     
     
       7. The method of  claim 6 , wherein further reducing power drawn by the electronic device comprises at least one of further reducing the brightness of the screen, further reducing the volume of the speaker, and shutting down one or more other resources of the electronic device. 
     
     
       8. A system for monitoring a battery powering an electronic device, the system comprising a voltage monitoring mechanism coupled to the battery, the voltage monitoring mechanism configured to:
 monitor a voltage of a battery powering an electronic device; 
 reduce power drawn by the electronic device responsive to satisfaction of a first criteria, the first criteria comprising whether a plurality of transient voltage-dips below a predetermined threshold voltage are detected; and 
 further reduce power drawn by the electronic device responsive to satisfaction of a second criteria, the second criteria comprising whether a number of transient voltage-dips below the predetermined threshold voltage per unit time exceeds a predetermined value, 
 wherein the predetermined threshold voltage is greater than a brownout voltage. 
 
     
     
       9. The system of  claim 8 , the voltage monitoring mechanism further configured to:
 determine that a predetermined termination voltage of the battery has been reached responsive to satisfaction of a third criteria, the third criteria comprising at least one of, whether a steady state voltage below the predetermined termination voltage has been detected, and whether a persistence voltage below the predetermined termination voltage has been detected; and 
 upon such determination, place the electronic device into one of a shutdown state and a hibernation state, 
 wherein the predetermined termination voltage is greater than the brownout voltage. 
 
     
     
       10. The system of  claim 9 , the third criteria further comprising at least one of whether a number of transient voltage-dips below the predetermined termination voltage per unit time exceeds a predetermined value, whether a number of transient voltage-dips below the predetermined termination voltage exceeds a predetermined number, and whether a duration of at least one transient voltage-dip below the predetermined termination voltage exceeds a predetermined duration. 
     
     
       11. The system of  claim 10 , wherein the predetermined termination voltage is equal to the predetermined threshold voltage. 
     
     
       12. The system of  claim 11 , wherein the predetermined termination voltage is user selectable. 
     
     
       13. The system of  claim 8 , wherein reducing power drawn by the electronic device comprises at least one of reducing a brightness of a screen, reducing a volume of a speaker, or shutting down a wireless communication device. 
     
     
       14. The system of  claim 13 , wherein further reducing power drawn by the electronic device comprises at least one of further reducing the brightness of the screen, further reducing the volume of the speaker, and shutting down one or more other resources of the electronic device. 
     
     
       15. A non-transitory computer-readable storage medium storing instructions that when executed by an electronic device cause the electronic device to:
 monitor a voltage of a battery powering an electronic device; 
 reduce power drawn by the electronic device responsive to satisfaction of a first criteria, the first criteria comprising whether a plurality of transient voltage-dips below a predetermined threshold voltage are detected; and 
 further reduce power drawn by the electronic device responsive to satisfaction of a second criteria, the second criteria comprising whether a number of transient voltage-dips below the predetermined threshold voltage per unit time exceeds a predetermined value, 
 wherein the predetermined threshold voltage is greater than a brownout voltage. 
 
     
     
       16. The non-transitory computer-readable storage medium of  claim 15 , further storing instructions to:
 determine that a predetermined termination voltage of the battery has been reached responsive to satisfaction of a third criteria, the third criteria comprising at least one of, whether a steady state voltage below the predetermined termination voltage has been measured, and whether a persistence voltage below the predetermined termination voltage has been measured; and 
 upon such determination, place the electronic device into one of a shutdown state and a hibernation state, 
 wherein the predetermined termination voltage is greater than the brownout voltage. 
 
     
     
       17. The non-transitory computer-readable storage medium of  claim 16 , the third criteria further comprising at least one of whether a number of transient voltage-dips below the predetermined termination voltage per unit time exceeds a predetermined value, whether a number of transient voltage-dips below the predetermined termination voltage exceeds a predetermined number, and whether a duration of at least one transient voltage-dip below the predetermined termination voltage exceeds a predetermined duration. 
     
     
       18. The non-transitory computer-readable storage medium of  17 , wherein the predetermined termination voltage is equal to the predetermined threshold voltage. 
     
     
       19. The non-transitory computer-readable storage medium of  claim 18 , wherein the predetermined termination voltage is user selectable. 
     
     
       20. The non-transitory computer-readable storage medium of  15 , wherein reducing power drawn by the electronic device comprises at least one of reducing a brightness of a screen, reducing a volume of a speaker, or shutting down a wireless communication device. 
     
     
       21. The non-transitory computer-readable storage medium of  20 , wherein further reducing power drawn by the electronic device comprises at least one of further reducing the brightness of the screen, further reducing the volume of the speaker, and shutting down one or more other resources of the electronic device.

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 13/363,213, entitled “Monitoring a Battery in a Portable Electronic Device,” filed Jan. 31, 2012, which claims to U.S. Provisional Application No. 61/533,717, entitled “Remaining State of Charge Indicator,” filed Sep. 12, 2011, the contents of which applications are entirely incorporated by reference herein. 
    
    
     BACKGROUND 
     Field 
     The present embodiments relate to techniques for monitoring a battery. More specifically, the present embodiments relate to techniques for monitoring a battery in a portable electronic device. 
     Related Art 
     Typically, the state of charge of a battery in a portable electronic device is monitored by a battery gas gauge. The state of charge is then often displayed to the user of the portable electronic device so that, among other things, the user can be made aware of the remaining battery life and can adjust their usage accordingly. The battery state of charge is also used by the portable electronic device to ensure that the device can shut down in an orderly fashion before the battery is no longer capable of powering the device. 
     However, battery gas gauges typically have some level of inaccuracy when monitoring the state of charge of a battery. Therefore, portable electronic devices usually shut down when the battery gas gauge determines that the state of charge of the battery has reached a predetermined reserve capacity. The predetermined reserve capacity is set to be larger than the expected inaccuracies in the battery gas gauge so that there is always enough remaining state of charge in the battery to shut down the device in an orderly fashion. However, as a result of this, there is often still some usable charge left in the battery after the device has shut down. This remaining state of charge is not available to the user of the device and hence, in effect, reduces the total capacity of the battery which is available to the user. 
     Hence, use of battery-powered portable electronic devices may be facilitated by monitoring a battery in a portable electronic device to allow use of the reserve state of charge. 
     SUMMARY 
     The disclosed embodiments provide a system that monitors a battery in a portable electronic device. During operation, the system monitors a state of charge of the battery while the battery is powering the portable electronic device. Next, when the state of charge of the battery reaches a predetermined reserve capacity, the system monitors a voltage of the battery. Then, when the monitored voltage of the battery reaches a predetermined termination voltage, the system puts the portable electronic device into a low power usage state. 
     In some embodiments, monitoring the state of charge of the battery involves using a battery gas gauge to monitor the state of charge of the battery. 
     In some embodiments, when the state of charge of the battery reaches the predetermined reserve capacity, the method additionally comprises displaying a minimal state of charge value to a user of the portable electronic device. 
     In some embodiments, the minimal state of charge value is a 1% state of charge. 
     In some embodiments, when the monitored voltage of the battery has a predetermined number of transient dips equal to or below the predetermined termination voltage, the system reduces the power drawn by the portable electronic device from the battery. 
     In some embodiments, reducing the power drawn by the portable electronic device from the battery includes one or more of: reducing the screen brightness, reducing the speaker volume, and shutting down a radio transceiver. 
     In some embodiments, putting the portable electronic device into a low power usage state includes putting the portable electronic device into a shutdown state. 
     In some embodiments, the predetermined reserve capacity is between a 2% state of charge of the battery and a 4% state of charge of the battery. 
     In some embodiments, the portable computing device includes at least one of: a smartphone, a tablet computer, and a laptop computer. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  shows a portable electronic device monitoring a battery in accordance with an embodiment. 
         FIG. 1B  shows two exemplary battery state of charge graphs overlaid on top of each other to aid in explanation of the operation of an embodiment. 
         FIG. 2  shows a flowchart illustrating the process of monitoring a battery in a portable electronic device in accordance with an embodiment. 
     
    
    
     In the figures, like reference numerals refer to the same figure elements. 
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing code and/or data now known or later developed. 
     The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium. 
     Furthermore, methods and processes described herein can be included in hardware modules or apparatus. These modules or apparatus may include, but are not limited to, an application-specific integrated circuit (ASIC) chip, a field-programmable gate array (FPGA), a dedicated or shared processor that executes a particular software module or a piece of code at a particular time, and/or other programmable-logic devices now known or later developed. When the hardware modules or apparatus are activated, they perform the methods and processes included within them. 
       FIG. 1A  shows a portable electronic device monitoring a battery in accordance with an embodiment. Portable electronic device  100  includes battery  102  which is coupled to battery monitoring unit (BMU)  104  and through current sense resistor  108  to system  106 . BMU  104  communicates with system  106  through communication link  110 , and BMU  104  includes battery gas gauge  112 . 
     Portable electronic device  100  may be any electronic device that is powered by a battery, including but not limited to a smartphone, a tablet computer, a laptop computer, or any other computing device. Battery  102  can be any type of battery capable of powering a portable electronic device, and can be implemented in any technology. In some embodiments, battery  102  includes more than one separate battery and/or battery cell. 
     BMU  104  monitors the voltage of battery  102  and the current flowing out of battery  102  through current sense resistor  108 . BMU  104  can be implemented on a separate processor from system  106  or on the same processor without departing from the invention. Additionally, in some embodiments, BMU  104  and system  106  may share other resources of portable electronic device  100  such as volatile memory (not shown) or non-volatile memory (not shown). Note that system  106  may represent all of the other functional portions of portable electronic device  100  not otherwise depicted in  FIG. 1A . 
     Battery gas gauge  112  monitors the state of charge of battery  102  and can be any process or mechanism implemented in hardware and/or software that can monitor a state of charge of battery  102 . In some embodiments, battery gas gauge  112  uses information including but not limited to information about the voltage of battery  102 , the current drawn from battery  102 , the battery chemistry and cycling history of battery  102 , and performance data based on batteries similar to battery  102 . Additionally, battery gas gauge  112  stores a value representing a predetermined reserve capacity for battery  102 . The predetermined reserve capacity can be a predetermined value entered by a user or manufacturer of portable electronic device  100 , or any other value calculated, entered or otherwise predetermined and used by battery gas gauge  112  as a buffer to account for potential inaccuracies in the monitoring of the state of charge of battery  102  by battery gas gauge  112 . In some embodiments, the predetermined reserve capacity is stored elsewhere in portable electronic device  100 , such as in BMU  104  or in system  106 . 
     During operation, portable electronic device  100  is powered by battery  102 . As power is drawn out of battery  102 , battery gas gauge  112  monitors the state of charge of battery  102 . BMU  104  communicates to system  106  the state of charge monitored by battery gas gauge  112  minus the predetermined reserve capacity. System  106  displays the monitored state of charge of battery  102  minus the predetermined reserve capacity to a user. In some embodiments, this information is displayed as a percentage of the full state of charge of battery  102  or the full state of charge of battery  102  minus the predetermined reserve capacity, or any other suitable format that can communicate the relative state of charge of battery  102  to a user of portable electronic device  100 . 
     As portable electronic device  100  continues drawing power from battery  102 , eventually the state of charge of battery  102  monitored by battery gas gauge  112  will fall until it is equal to or less than the predetermined reserve capacity. When this level is reached, BMU  104  communicates to system  106  through communication link  110  that the state of charge of battery  102  is 1%. Note that BMU  104  could communicate to system  106  a value representing any minimal state of charge of battery  102  without departing from the invention. For example, BMU  104  could communicate to system  106  that the state of charge of battery  102  is the lowest state of charge above 0% that can be displayed to a user of portable electronic device  100 . 
     BMU  104  then monitors the voltage of battery  102  and continues communicating to system  106  through communication line  110  that the state of charge of battery  102  is 1% until the voltage measured from battery  102  by BMU  104  reaches a predetermined termination voltage. Note that BMU  104  may determine that the voltage measured from battery  102  has reached the predetermined termination voltage based on information including but not limited to one or more of the following: the number, duration, or frequency of transient voltage dips that are equal or below the predetermined termination voltage, or a steady-state or persistence voltage measurement equal to or below the predetermined termination voltage. 
     Additionally, in some embodiments, before BMU  104  has determined that the voltage from battery  102  has reached the predetermined termination voltage, when BMU  104  measures one or more transient voltage dips equal to or below the predetermined termination voltage or some other predetermined threshold voltage, BMU  104  signals system  106  through communication link  110  to reduce the power drawn by one or more resources of portable electronic device  100 . For example, after BMU  104  has communicated to system  106  that a predetermined number of transient voltage dips of the voltage from battery  104  are equal to or below the predetermined termination voltage, system  106  may reduce the power drawn from battery  102  through one or more of the following actions: reducing the brightness of a screen, reducing the volume of speakers, or shutting down a wireless communication device such as a radio transceiver. 
     Furthermore, as BMU  104  measures more transient voltage dips equal to below the predetermined termination voltage that exceed other predetermined thresholds in number, frequency, or duration, BMU  104  may signal system  106  through communication link  110  to take additional actions such as further reducing the screen brightness, or speaker volume, or shutting down one or more other resources of portable electronic device  100 . System  106  may also display a message to a user of portable electronic device  100  to indicate the actions that are being taken. 
     Once BMU  104  has determined that the voltage of battery  102  has reached the predetermined termination voltage, BMU  104  communicates a signal to system  106  through communication link  110  that causes portable electronic device  100  to go into a low power usage state. The low power usage state may include but is not limited to a hibernate state, a shutdown state, or any other state that minimizes or stops further power from being drawn from battery  102 . In some embodiments, this signal may include but is not limited to setting a flag that indicates to system  106  that portable electronic device  100  should be shut down. 
     Note that the predetermined termination voltage can be selected by a manufacturer or user of portable electronic device  100 , and may be selected so that the voltage from battery  102  is sufficient to allow portable electronic device  100  to enter a low power usage state that minimizes or stops further power from being drawn from battery  102  in an orderly fashion and without loss of data or other potentially undesirable effects on portable electronic device  100 . For example, the termination voltage may be picked to be high enough above the brownout voltage for portable electronic device  100  so that even under high load operating conditions, portable electronic device  100  can shut down in an orderly fashion before the voltage from battery  102  reaches the brownout voltage. 
       FIG. 1B  shows two exemplary battery state of charge graphs overlaid on top of each other to aid in explanation of the operation of an embodiment. Note that in order to help highlight details of the graphs, the axes of  FIG. 1B  are not drawn to scale. One graph depicts displayed state of charge vs. battery capacity curve  122  and uses the vertical axis displayed state of charge  126  on the left side of  FIG. 1B , while the other graph depicts battery voltage vs. battery capacity curve  124  and uses the vertical axis battery voltage  128  on the right side of  FIG. 1B . 
     As described above, during operation of portable electronic device  100 , as power is drained from battery  102 , the state of charge determined by battery gas gauge  112  minus the predetermined reserve capacity is reported by BMU  104  to system  106  for display to a user. This is depicted by displayed state of charge vs. battery capacity curve  122 . As portable electronic device  100  continues to draw power from battery  102 , the state of charge of battery  102  monitored by battery gas gauge  112  will continue to fall until it is equal to the predetermined reserve capacity. Note that in the embodiments depicted in  FIG. 1B , system  106  does not display a state of charge of battery  102  to the user that is less than a minimal state of charge (e.g., 1% in this embodiment). In other embodiments, the minimal state of charge is displayed until the portable electronic device begins to enter a low power usage state. 
     When battery gas gauge  112  determines that the state of charge of battery  102  has decreased to a level that is equal to the predetermined reserve capacity, BMU  104  continues reporting to system  106  that the state of charge of battery  102  is 1%. BMU  104  then monitors the voltage of battery  102  as depicted in battery voltage vs. battery capacity curve  124 . As portable electronic device  100  continues to drain power from battery  102 , the voltage of battery  102  drops until it reaches termination voltage  134 . When this occurs, BMU  104  communicates to system  106  through communication link  110  a shutdown signal that causes portable electronic device  100  to go into a state that stops further power from being drawn from battery  102 . Note that, for convenience, termination voltage  134  on the right axis battery voltage  128  is depicted as lining up with 0% on the displayed state of charge  126  axis. 
     In this embodiment, the state of charge of battery  102  between when the voltage of battery  102  reaches the termination voltage and when battery gas gauge  112  determines the state of charge of battery  102  to be equal to the predetermined reserve capacity (e.g., 0% on the axis displayed state of charge  126 ) is represented by reserve state of charge  132  and is available for use by portable electronic device  100 . 
       FIG. 2  shows a flowchart illustrating the process of monitoring a battery in a portable electronic device in accordance with an embodiment. First, the state of charge (SOC) of a battery in a portable electronic device is monitored (step  202 ). Then, if the SOC is not less than or equal to the predetermined reserve capacity (step  204 ), the process returns to step  202 . If the SOC is less than or equal to the predetermined reserve capacity (step  204 ), then the process reports that the SOC equals 1% (step  206 ). The battery voltage is monitored (step  208 ), and if it is not less than or equal to the termination voltage (step  210 ), then the process returns to step  208 . If the monitored voltage of the battery is less than or equal to the termination voltage (step  210 ), then the portable electronic device is shut down (step  212 ). 
     The foregoing descriptions of various embodiments have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention.

Metadata:
Filing Date: 20160219
Publication Date: 20171128
Grant Date: 20171128
Priority Date: 20110912
Inventors: VALENTINE VAL
Assignee: APPLE INC
CPC Classifications: [{"code": "G01R31/362", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/3827", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/3682", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3212", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/3606", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y02B60/50", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B60/1282", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/3287", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/027", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02B60/1292", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3212", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/3212", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/3287", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/382", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/3835", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/3827", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/3646", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y02D10/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/027", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R31/3835", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3287", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D10/00", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47829269