PATENT DOCUMENT

Publication Number: US-11152808-B2
Application Number: US-201816059127-A
Country: US
Kind Code: B2

Title: Multi-phase battery charging with boost bypass

Abstract:
The disclosed embodiments provide a system that manages use of a battery in a portable electronic device. During operation, the system operates a charging circuit for converting an input voltage from a power source into a set of output voltages for charging the battery and powering a low-voltage subsystem and a high-voltage subsystem in the portable electronic device. Upon detecting the input voltage from the power source and a low-voltage state in the battery during operation of the charging circuit, the system uses a first inductor group in the charging circuit to down-convert the input voltage to a target voltage of the battery that is lower than a voltage requirement of the high-voltage subsystem. The system also uses a second inductor group in the charging circuit to up-convert the target voltage to power the high-voltage subsystem.

Claims:
What is claimed is: 
     
       1. A method for managing use of a battery in a portable electronic device, comprising:
 operating a charging circuit, the charging circuit comprising a plurality of inductors, of the portable electronic device during discharge of the battery to simultaneously power a low-voltage subsystem and a high-voltage subsystem in the portable electronic device; wherein: 
 during discharge of the battery in a low-voltage state, operating the charging circuit comprises:
 powering the high-voltage subsystem by the plurality of inductors to up-convert a battery voltage; and 
 powering the low-voltage subsystem along a first bypass path through the charging circuit that bypasses the plurality of inductors; 
 
 during discharge of the battery in a state above the low-voltage state, operating the charging circuit comprises:
 powering the high-voltage subsystem from the battery voltage along a second bypass path through the charging circuit that bypasses the plurality of inductors; and 
 powering the low-voltage subsystem along the first bypass path. 
 
 
     
     
       2. The method of  claim 1 , further comprising:
 upon detecting coupling of an external load to the portable electronic device, using a first inductor group of the plurality of inductors to up-convert the battery voltage to power the external load. 
 
     
     
       3. A charging system for a portable electronic device, comprising:
 a switching converter comprising a plurality of inductors; and 
 a control circuit configured to use the switching converter to convert a battery voltage into a set of output voltages to simultaneously power a low-voltage subsystem and a high-voltage subsystem in the portable electronic device, wherein the control circuit is further configured to:
 during discharge of a battery in a low-voltage state, power the low-voltage subsystem from the battery voltage along a first bypass path through the charging system that bypasses the plurality of inductors and power the high-voltage subsystem by up-converting the battery voltage using the plurality of inductors; and 
 during discharge of the battery in a state above the low-voltage state, power the low-voltage subsystem from the battery voltage along the first bypass path and power the high-voltage subsystem from the battery voltage along a second bypass path that bypasses the plurality of inductors. 
 
 
     
     
       4. The charging system of  claim 3 , wherein upon detecting coupling of an external load to the portable electronic device, the control circuit is further configured to:
 use a first inductor group of the plurality of inductors to up-convert the battery voltage to power the external load. 
 
     
     
       5. A portable electronic device, comprising:
 a first set of components in a high-voltage subsystem; 
 a second set of components in a low-voltage subsystem; 
 a battery having a battery voltage; 
 a switching converter comprising a plurality of inductors; and 
 a control circuit configured to use the switching converter to convert the battery voltage into a set of output voltages to simultaneously power the low-voltage subsystem and the high-voltage subsystem, wherein the control circuit is further configured to:
 during discharge of the battery in a low-voltage state, power the low-voltage subsystem from the battery voltage along a first bypass path through the switching converter that bypasses the plurality of inductors and power the high-voltage subsystem by up-converting the battery voltage using the plurality of inductors; and 
 during discharge of the battery voltage in a state above the low-voltage state, power the low-voltage subsystem from the battery voltage along the first bypass path and power the high-voltage subsystem from the battery voltage along a second bypass path through the switching converter that bypasses the plurality of inductors. 
 
 
     
     
       6. The portable electronic device of  claim 5 , wherein upon detecting coupling of an external load to the portable electronic device, the control circuit is further configured to:
 use a first inductor group of the plurality of inductors to up-convert the battery voltage to power the external load.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/749,470, by inventors Jamie Langlinais, Mark A. Yoshimoto and Lin Chen, entitled “Multi-Phase Battery Charging with Boost Bypass, filed Jun. 24, 2015, which claims the benefit of U.S. Provisional Application No. 62/044,478, by inventors Jamie Langlinais, Mark A. Yoshimoto and Lin Chen, entitled “Multi-Phase Battery Charging with Boost Bypass,” filed Sep. 2, 2014, both of which are incorporated herein by reference. 
     The subject matter of this application is related to the subject matter in a non-provisional application by inventors Thomas C. Greening, Qing Liu and William C. Athas, entitled “Battery Charging with Reused Inductor for Boost,” having Ser. No. 14/749,466, filed Jun. 24, 2015. 
    
    
     BACKGROUND 
     Field 
     The disclosed embodiments relate to batteries for portable electronic devices. More specifically, the disclosed embodiments relate to techniques for performing multi-phase charging of batteries with boost bypass. 
     Related Art 
     A portable electronic device is typically configured to shut down when its battery reaches a predetermined minimum voltage, which may be higher than the lowest operating voltage of the battery. For example, although a lithium-ion battery may be considered empty when the battery voltage reaches 3.0V, certain components of the computing device (e.g., the radio and speaker subsystems of a mobile phone or tablet computer) may require a minimum voltage of 3.4V to operate, and the device may be configured to shut down at 3.4V to avoid browning out these components. As a result, the battery may contain unused capacity between 3.0V and 3.4V. 
     The amount of unused capacity may depend on the load current, temperature and age of the battery. For light loads on warm, fresh batteries, the unused capacity is typically just a few percent of the overall capacity. For colder or older batteries, however, the unused capacity may increase dramatically. For example,  FIG. 1  shows an example of batteries discharged at a given load (0.5 C load, which is the current required to discharge a battery in two hours) at two different temperatures. As shown there, discharging the battery at 25° C. may result in a few percentage of the overall capacity occurring under a cutoff voltage (shown in  FIG. 1  as 3.4V), but discharging the battery at 0° C. may result in as much as 30% of the overall capacity occurring under the cutoff voltage. Accordingly, it may be desirable to have a system that is able to take advantage of this unused capacity. 
     SUMMARY 
     The disclosed embodiments provide a system that manages use of a battery in a portable electronic device. During operation, the system operates a charging circuit for converting an input voltage from a power source into a set of output voltages for charging the battery and powering a low-voltage subsystem and a high-voltage subsystem in the portable electronic device. Upon detecting the input voltage from the power source and a low-voltage state in the battery during operation of the charging circuit, the system uses a first inductor group in the charging circuit to down-convert the input voltage to a target voltage of the battery that is lower than a voltage requirement of the high-voltage subsystem. The system also uses a second inductor group in the charging circuit to up-convert the target voltage to power the high-voltage subsystem. 
     In some embodiments, upon detecting the input voltage from the power source and a high-voltage state in the battery, the system uses the first and second inductor groups to:
         (i) down-convert the input voltage to a target voltage of the battery; and   (ii) charge the battery and power the low-voltage subsystem and the high-voltage subsystem from an input current of the power source.       

     In some embodiments, upon detecting the input voltage from the power source and a voltage state in the battery between the low-voltage state and a high-voltage state, the system uses the first inductor group to down-convert the input voltage to the target voltage of the battery. Next, the system powers the high-voltage subsystem from at least one of the up-converted target voltage from the second inductor group and the target voltage from the first and second inductor groups. 
     In some embodiments, upon detecting discharging of the battery in the low-voltage state, the system uses the second inductor group to up-convert a battery voltage of the battery to power the high-voltage subsystem, and uses the charging circuit to directly power the low-voltage subsystem from the battery voltage. 
     In some embodiments, upon detecting coupling of an external load to the portable electronic device, the system uses the first inductor group to up-convert the battery voltage to power the external load. 
     In some embodiments, during discharge of the battery between the low-voltage state and a high-voltage state, the system powers the high-voltage subsystem from at least one of the up-converted battery voltage from the second inductor group and the battery voltage along a bypass path to the high-voltage subsystem in the charging circuit. 
     In some embodiments, each of the first and second inductor groups includes one or more inductors. 
     In some embodiments, upon detecting a change between a voltage requirement of the high-voltage subsystem and a battery voltage of the battery beyond a threshold, the system switches a membership of an inductor between the first and second inductor groups to facilitate operation of the charging circuit. 
     In some embodiments, the operation of the charging circuit includes down-converting the input voltage, up-converting a target voltage of the battery, and/or up-converting a battery voltage of the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a plot of voltage versus used capacity for a battery in accordance with the disclosed embodiments. 
         FIG. 2  shows a standard battery-charging circuit in accordance with the disclosed embodiments. 
         FIG. 3A  shows a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 3B  shows a charging system for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 3C  shows a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4A  shows a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4B  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4C  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4D  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4E  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4F  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4G  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4H  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4I  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4J  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4K  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4L  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4M  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4N  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 4O  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 5  shows a charging system for a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 6  shows a flowchart illustrating the process of managing use of a battery in a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 7  shows a flowchart illustrating the process of managing use of a battery in a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 8  shows a flowchart illustrating the process of managing use of a battery in a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 9  shows a portable electronic device in accordance with the disclosed embodiments. 
     
    
    
     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. 
     The disclosed embodiments provide a method and system for managing use of a battery in a portable electronic device. More specifically, the disclosed embodiments provide a charging circuit that may provide an up-converted voltage and/or down-converted voltage to one or more subsystems of the portable electronic device. In some instances, the charging circuit may include two or more inductor groups, each of which contains one or more inductors. In these instances, each inductor group may be used to produce a separate up-converted or down-converted voltage for use in charging the battery, powering one or more subsystems of the portable electronic device, and/or powering an external load. As a result, the charging circuit may have fewer power losses than a charging circuit that uses a single-phase converter and a linear regulator to supply power to subsystems with different voltage requirements. The use of two or more inductors may also avoid an increase in space occupied by a single, larger inductor, thereby allowing unused capacity in the battery to be accessed without exceeding a height limitation of the portable electronic device. 
       FIG. 2  shows a typical charger circuit for a system that is disabled when the system voltage drops below a minimum operating voltage, such as 3.4V. As shown there, the charger circuit may connect an intermittent power source  202  (e.g., a power adapter), a battery  214 , and one or more systems  204  powered by battery  214 . In some instances, the system may comprise a connector (not shown) between the intermittent power source and the charger circuit, which may allow the power source  202  to be connected to or disconnected from the charger circuit. Field-effect transistor (FET) A  206  protects against reverse voltage and prevents current from flowing from the battery to the connector (e.g., when a power adapter providing power source  202  is not connected to the system). FET B  208  and FET C  210  are alternately switching FETs that, with an inductor  216 , form a buck converter that produces a bucked voltage at the output of the inductor V MAIN . If the battery voltage is less than the minimum operating voltage (e.g., 3.4V), V MAIN  may be controlled using the buck converter to the minimum operating voltage, and FET D  212  is controlled linearly to lower the voltage at V BAT  to a target voltage for charging battery  214 . FET D  212  is also configured to stop charging when battery  214  is full. When the battery  214  is discharging to power the one or more systems  204 , FETs B  208  and C  210  stop switching, and FET D  212  is fully turned on to connect battery  214  to the one or more systems  204 . 
       FIG. 3A  shows a variation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. For example,  FIG. 3A  may be used to supply power to components of a laptop computer, tablet computer, mobile phone, digital camera, and/or other battery-powered electronic device. In these variations, the portable electronic device may include one or more high-voltage subsystems  306  and one or more low-voltage subsystems  304 , which may be powered by a battery  322 . The one or more low-voltage subsystems  304  may require a first voltage that is less than a second voltage required by the one or more high-voltage subsystems  306  during operation of the portable electronic device. For example, in some variations the low-voltage subsystems  304  may require a first voltage at or below the cutoff voltage of battery  322  (e.g., 3.0 V), while the high-voltage subsystems  306  may require a second voltage above the cutoff voltage of the battery (e.g., 3.4 V). In other variations, the first voltage required by the one or more low-voltage subsystems  304  may be above the cutoff voltage of battery  322 . The charging circuit may provide boost functionality, which may supply power to one or more high-voltage subsystems  306 , for example, when the voltage of the battery  322  is below the second voltage. On the other hand, low-voltage subsystems  304  may require significantly less voltage than high-voltage subsystems  306  and/or the cutoff voltage of battery  322 , and in some instances may be powered directly by battery  322 . 
     For example, the majority of components in a portable electronic device, including the central processing unit (CPU), graphics-processing unit (GPU), and/or integrated circuit rails, may require voltages much less than an exemplary 3.0V cutoff voltage for battery  322 . On the other hand, the radio and speaker subsystems of the portable electronic device may require an exemplary minimum voltage of 3.4V to operate. As a result, subsystems in the portable electronic device may be divided into two or more groups, such as low-voltage subsystems  304  that can be powered from 3.0V, and high-voltage subsystems  306  that require a minimum of 3.4V. 
     As shown in  FIG. 3A , the charging circuit with boost functionality includes an inductor  308  and six FETs  310 - 320 , and may be connected to a power source  302 . FET A  310  may be turned on when an identified power source  302  is available and when disabled provides reverse voltage protection from a power source incorrectly designed or connected backwards. FET A  310  is turned off when power source  302  is not available (e.g., an external power adapter is not connected) to prevent the portable electronic device from transmitting power to either an unavailable power source  302  or to a connector where a power source may be connected. FETs B  312  and C  314  couple the input terminal of inductor  308  to a voltage node V X  and a reference voltage such as ground, respectively. FETs B  312  and C  314  may be switched to selectively couple the input of inductor  308  to V X  or the reference voltage. FET D  316  may couple battery  322  to a voltage node V Lo  (which may be connected to the one or more low-voltage subsystems  304  and a load terminal of inductor  308 ). FETE  318  may couple the V LO  to a voltage node V HI  (which may be connected to the one or more high-voltage subsystems  306 ), or in other variations may couple V HI  directly to battery  322 . FET F  320  couples the V X  to the V HI , which may be used to couple input voltage from power source  302  and/or boosted battery voltage from inductor  308  to high-voltage subsystems  306 . 
       FIG. 3B  shows a charging system for a portable electronic device in accordance with the disclosed embodiments. The charging system of  FIG. 3B  may convert an input voltage from power source  302  and/or a battery voltage from battery  322  into a set of output voltages for charging battery  322  and/or powering one or more low-voltage subsystems  304  and one or more high-voltage subsystems  306 . 
     As shown in  FIG. 3B , the charging system includes a switching converter  330 . Switching converter  330  may include one or more inductors and a set of switching mechanisms such as FETs, diodes, and/or other electronic switching components. For example, switching converter  330  may be provided by the converter shown in  FIG. 3A , which includes inductor  308  with an input terminal and a load terminal and two switching mechanisms (e.g., as provided by FETs  312 - 314 ), which are configured to couple the input terminal to either a voltage node V X  (which may be connected to an output of power source  302 ) or a reference voltage (e.g., ground), such as discussed above. The charging system may include switching mechanisms  332  and  336  and regulators  334  and  338 , which collectively may be used to couple the output of switching converter  330  to either battery  322 , high-voltage subsystems  306 , and/or low-voltage subsystems  304  and couple power source  302  to high-voltage subsystems  306 . Each switching mechanism may selectively couple different voltage nodes, and may include a switch, a FET (such as FETs  310  and  318  of  FIG. 3A ), a diode, or the like. Each regulator may selectively be controlled to control a voltage at one or more voltage nodes or act as a switch, and may include a FET (such as FETs  316  and  320  of  FIG. 3A ), a variable resistor, or the like. 
     For example, switching mechanism  332  may provide reverse voltage protection from an improperly functioning power source  302  (e.g., a power source with a faulty design or an incorrectly connected power source  302 ) and may prevent current flowing from the voltage node V X  to the power source  302  (shown there as V BUS ). The switching converter  330  may couple voltage node V X  with a voltage node V LO , which may in turn be coupled to low-voltage subsystems  304 . Regulator  338  may selectively couple V X  with a voltage node V HI  either directly or by linearly regulating V HI  to a voltage less than V X , which may in turn be coupled to high-voltage subsystems  306 . Switching mechanism  336  may selectively couple V HI  with V LO , or in some instances may selectively couple V HI  with battery  322 . Regulator  334  may selectively couple V LO  to battery  322  either directly or by linearly regulating the battery voltage to a voltage less than V LO . The switching mechanisms may be used to control power to the high-voltage subsystems  306  and the low voltage subsystems  304 , as will be described in more detail below. 
       FIG. 3C  shows a charging circuit for a portable electronic device in accordance with the disclosed embodiments. The charging circuit may convert an input voltage from power source  302  and/or a battery voltage from battery  322  into a set of output voltages (e.g., V LO , V HI1 , V HI2 , V HI3 ) for charging battery  322  and/or powering a number of subsystems  350 - 356  of the portable electronic device with different voltage requirements (while shown there as having four subsystems, the charging circuit may power any number of subsystems having different voltage requirements, such as two, three, four, or five or more subsystems). For example, the charging system may power one or more subsystems with a first voltage requirement (which in some variations is at or below the cutoff voltage of battery  322  (e.g., 3.0V)), one or more subsystems with a second voltage requirement that is higher than the first voltage requirement (which may be slightly higher than the cutoff voltage of battery  322  (e.g., 3.2V)), one or more subsystems with a third voltage requirement that is higher than the second voltage requirement (e.g., 3.4V), and one or more subsystems with the highest voltage requirement in the portable electronic device (e.g., a fourth voltage requirement that is higher than the third voltage requirement, such as 3.6V). 
     As with the charging system of  FIG. 3B , the charging system of  FIG. 3C  includes a switching converter  330 , which may be provided by one or more inductors and a set of switching mechanisms such as FETs, diodes, and/or other electronic switching components. Specifically, switching converter  330  may be any type of bidirectional converter, such as a buck converter, a boost converter, an inverting converter, a buck-boost converter, a Ćuk converter, a single-ended primary-inductor converter (SEPIC), and/or a Zeta converter. 
     Additional switching mechanisms  336 ,  340 , and  344  and regulators  334 ,  338 ,  342 , and  346  may be used to couple the output of switching converter  330  to battery  322  and subsystems  350 - 356 , power subsystems  350 - 356  from power source  302  and/or battery  322 , and generate output voltages that meet the voltage requirements of subsystems  350 - 356 . 
     Switching mechanisms  336 ,  340 , and  344  and regulator  334  couple the output of switching converter  330  to battery  322  and subsystems  350 - 356 . As shown in  FIG. 3C , regulator  334  may selectively couple battery  322  to voltage node V LO  (which may be connected to a load terminal of switching converter  330  and subsystems  350 ). Switching mechanism  336  may selectively couple voltage node V LO  to voltage node V HI1 , which in turn may be connected to subsystems  352 . Switching mechanism  340  may selectively couple voltage node V HI1  to voltage node V HI2 , which in turn may be connected to subsystems  354 . Switching mechanism  344  may selectively couple voltage node V HI2  to voltage node V HI3 , which in turn may be connected to subsystems  356 . In other variations, each of switching mechanisms  336 ,  340 , and  344  may directly connect battery  322  to subsystems  352 ,  354 , and  356  respectively. 
     Regulators  338 ,  342 , and  346  couple voltage node V X  (which in turn may provide the input voltage from power source  302  and/or boosted battery voltage from switching converter  330 ) to subsystems  352 - 356 , respectively, either directly or by linearly regulating to a voltage less than V X . For example, as shown in  FIG. 3C , regulator  338  may selectively couple voltage node V X  with voltage node V HI1  and subsystem  352  either directly or by linearly regulating to a voltage V HI1  less than V X . Regulator  342  may selectively couple voltage node V X  with voltage node V HI2  and subsystem  354  either directly or by linearly regulating to a voltage V HI2  less than V X . Regulator  346  may selectively couple voltage node V X  with voltage node V HI3  and subsystem  356  either directly or by linearly regulating to a voltage V HI3  less than V X . 
     During operation of the charging system, the system may be powered by power source  302  and/or battery  322 . Similarly, battery  322  may be in a number of voltage states, including an undervoltage state, one or more low-voltage states, a high-voltage state, and/or a fully charged state. Battery  322  is considered undervoltage if the battery voltage of battery  322  is less than or equal to a designated cutoff voltage (e.g. a minimum operating voltage) of the battery (e.g., 3.0V), and battery  322  has no useful remaining charge. A low-voltage battery  322  may have a battery voltage that can be used directly by low-voltage subsystems  304  but not high-voltage subsystems  306  (e.g., between 3.0V and 3.4V). A high-voltage battery  322  may have a voltage that can be used directly by all subsystems (e.g., greater than 3.4V-3.6V), but is not yet fully charged. A fully charged battery  322  may be at the maximum voltage of battery  322  and thus cannot be charged any further. In instances where the device has three or more subsystems having different voltage requirements, such as shown in  FIG. 3C , the battery may have multiple low-voltage states (e.g., a first low-voltage state where the battery voltage is high enough to power subsystems  350  but not subsystems  352 - 356 , a second low-voltage state where the battery is high enough to power subsystems  350  and  352  but not subsystems  354  and  356 , and a third low-voltage state where the battery is high enough to power subsystems  352 - 354  but not subsystems  356 ). 
       FIG. 4A  shows a charging circuit for a portable electronic device in accordance with the disclosed embodiments. As with the charging circuit of  FIG. 3A , the charging circuit of  FIG. 4A  may be used to supply power to components of a portable electronic device. The portable electronic device may include one or more high-voltage subsystems  406  and one or more low-voltage subsystems  404 , both of which may be powered by a battery  434 . Low-voltage subsystems  404  may require a first voltage that is less than a second voltage required by high-voltage subsystems  406  during operation of the portable electronic device. For example, in some variations low-voltage subsystems  404  may require a first voltage at or below the cutoff voltage of battery  434  (e.g., 3.0 V), while high-voltage subsystems  406  may require a second voltage above the cutoff voltage of the battery (e.g., 3.4 V). In other variations, the first voltage required by the one or more low-voltage subsystems  404  may be above the cutoff voltage of battery  434 . 
     The charging circuit may provide boost functionality, which may supply power to one or more high-voltage subsystems  406 , for example, when the voltage of the battery  434  is below the second voltage. On the other hand, low-voltage subsystems  404  may require significantly less voltage than high-voltage subsystems  406  and/or the cutoff voltage of battery  434 , and in some instances may be powered directly by battery  434 . 
     Unlike the charging circuit of  FIG. 3A , the charging circuit of  FIG. 4A  may provide both boost and buck functionality at the same time. As shown in  FIG. 4A , the charging circuit with both boost and buck functionality includes two inductors  408 - 410  and eight FETs  418 - 432 . The operation of FETs  418 - 426  may be controlled by a first control circuit  412 , the operation of FET  428  may be controlled by a second control circuit  414 , and the operation of FETs  430 - 432  may be controlled by a third control circuit  416 . Control circuit  412  may use FETs  420 - 426  and inductors  408 - 410  to buck and/or boost voltages in the charging circuit. Control circuit  414  may use FET  428  to connect or disconnect battery  434  to the charging circuit, thus enabling or disabling the charging or discharging of battery  434  through the charging circuit. Control circuit  416  may use FETs  430 - 432 , along with FET  424  controlled by control circuit  412 , to direct current to high-voltage subsystems  406  through a boost path that performs up-converting of a battery voltage and/or target voltage V BAT  through inductor  410  and FETs  426  and  432  or a bypass path that supplies the battery or target voltage directly to high-voltage subsystems  406 . The charging circuit may also be connected to a power source  402  such as a power adapter, which supplies an input voltage for charging battery  434  and/or powering low-voltage subsystems  404  and high-voltage subsystems  406 . 
     FET  418  may be turned on when power source  402  is available and disabled to provide reverse voltage protection from an incorrectly designed and/or connected power source. FET  418  may also be disabled when power source  402  is not available (e.g., an external power adapter is not connected) to prevent the portable electronic device from transmitting power to an unavailable power source  402  and/or to a connector where a power source may be connected. FETs  420  and  422  couple the input terminal of inductor  408  to the input voltage and a reference voltage such as ground, respectively. FETs  424  and  426  couple the input terminal of inductor  410  to the input voltage and the reference voltage, respectively. FET  428  may couple battery  434  to the load terminals of inductors  408 - 410  and low-voltage subsystems  404 . FET  430  may couple the load terminal of inductor  410  to high-voltage subsystems  406  along a bypass path from battery  434  to high-voltage subsystems  406 , while FET  432  may couple the input terminal of inductor  410  along a boost path from battery  434  to high-voltage subsystems  406 . 
     The inclusion of two inductors  408 - 410  in the charging circuit may allow the charging circuit to provide a multiple-phase switching converter that can independently buck the input voltage from power source  402  (if power source  402  is available) into a target voltage of battery  434  and boost the target voltage into an output voltage V HI  for powering high-voltage subsystems  406 . If power source  402  is not available and battery  434  is discharging, the control circuit may use the multiple-phase switching converter to boost the battery voltage of battery  434  into one or more output voltages for powering high-voltage subsystems  406  and/or an external load. Inductors  408 - 410  may also occupy less height than a single, larger inductor that may be used to produce the same current. The operation of the charging circuit is described in further detail below with respect to  FIGS. 4B-4F . 
     Because the charging circuit does not linearly operate FETs  418 - 432 , the charging circuit may have significantly lower power losses than the charging circuit of  FIG. 3A . For example, the linear operation of FET F  320  in the charging circuit of  FIG. 3A  may incur a power dissipation of the output current multiplied by the difference between V X  and V HI . The proportional increase of the power dissipation with V X  and the resultant thermal dissipation from linear operation of FET F  320  may prevent charging at higher voltages and/or currents until battery  322  has reached a battery voltage that is sufficient to directly power high-voltage subsystems  306 . In turn, the charging circuit of  FIG. 3A  may not be suitable for use with portable electronic devices that use higher input voltages, large loads on the high-voltage subsystem rail, and/or larger batteries. Whereas, the power loss associated with boosting the battery voltage of battery  434  into an output voltage for powering high-voltage subsystems  406  may primarily include the conduction losses and/or switching losses of inductor  410 , FETs  424 - 426  and  432 , and/or other components along a boost path from battery  434  to high-voltage subsystems  406 . As a result, the charging circuit of  FIG. 4A  may provide faster charging and/or lower power and thermal dissipation than the charging circuit of  FIG. 3A . 
       FIG. 4B  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. More specifically,  FIG. 4B  shows the operation of the charging circuit of  FIG. 4A  during charging of battery  434  in a low-voltage state. In the low-voltage state, battery  434  may have a battery voltage that can be used directly by low-voltage subsystems  304  but not high-voltage subsystems  306  (e.g., between 3.0V and 3.4V). 
     To charge battery  434 , an input voltage and input current may be supplied from power source  402 , and FETs  418  and  428  may be enabled to couple power source  402  and battery  434 , respectively, to the charging circuit. The input current may be supplied to battery  434  along a buck path  436  that includes FETs  418 - 420  and  428  and inductor  408 . Control circuit  412  may use FETs  420 - 422  and inductor  408  to down-convert the input voltage into a target voltage V BAT  of battery  434  that is lower than the voltage requirement of high-voltage subsystems  406 . The same target voltage may be used to power low-voltage subsystems  404 . For example, control circuit  412  may switch FETs  420 - 422  on and off in complementary fashions as part of a servomechanism feedback loop that controls both V BAT  and V LO  to the target voltage of battery  434 . Control circuit  414  may turn FET  428  on to enable charging of battery  434  from the input current and target voltage. 
     To power high-voltage subsystems  406 , the input current may be supplied to high-voltage subsystems  406  along a boost path  438  that includes inductor  410  and FET  432 . To cause current to flow in the “reverse” direction along boost path  438 , control circuit  416  may turn FET  430  off and FET  432  on. In addition, control circuit  412  may use FETs  426  and  432  and inductor  410  to up-convert the target voltage of battery  434  to V HI , which is used to power high-voltage subsystems  406 . For example, control circuit  412  may turn FET  424  off to direct current flow in the reverse direction across inductor  410  to high-voltage subsystems  406 . Control circuit  412  may additionally switch FETs  426  and  432  on and off in complementary fashions as part of another servomechanism feedback loop that controls the input terminal of inductor  410  and V HI  to at or above the voltage requirement of high-voltage subsystems  406  (e.g., 3.4V or higher). 
       FIG. 4C  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. More specifically,  FIG. 4C  shows the operation of the charging circuit of  FIG. 4A  during charging of battery  434  in a high-voltage state. In the high-voltage state, battery  322  may have a voltage that can be used directly by all subsystems (e.g., greater than 3.4V-3.6V), but is not yet fully charged. 
     As with  FIG. 4B , an input voltage and input current may be supplied from power source  402 , and FETs  418  and  428  may be enabled. FET  428  may subsequently be configured to stop charging once battery  434  reaches a fully charged state to discontinue charging of battery  434 . The input current may be supplied to battery  434  along buck path  436 , which includes FETs  418 - 420  and  428  and inductor  408 . Control circuit  412  may use FETs  420 - 422  and inductor  408  to down-convert the input voltage into a target voltage of battery  434  V BAT , which is at or above the voltage requirement of high-voltage subsystems  406 . For example, control circuit  412  may alternately switch FETs  420 - 422  on and off as part of a servomechanism feedback loop that produces the target voltage at the load terminal of inductor  408 . As a result, both low-voltage subsystems  404  and high-voltage subsystems  406  may be powered directly by the target voltage of battery  434 . 
     Control circuit  412  may also provide additional input current along a second buck path  440  that includes inductor  410  and FETs  424  and  430 . In other words, control circuit  412  may also use FETs  424 - 426  and inductor  410  to down-convert the input voltage into the target voltage of battery  434 . For example, control circuit  412  may alternately switch FETs  424 - 426  on and off as part of a servomechanism feedback loop that produces the target voltage at the load terminal of inductor  410 . The target voltage and input current from both paths  436  and  440  may then be used to charge battery  434  and power low-voltage subsystems  404  and high-voltage subsystems  406 . 
     To prevent current from flowing in the reverse direction across inductor  410 , control circuit  416  may turn FET  432  off. Control circuit  416  may turn FET  430  on to direct the input current to high-voltage subsystems  406  from the load terminals of inductors  408 - 410 . 
     During charging of battery  434  that is between the low-voltage state and high-voltage state (e.g., 3.4V to 3.6V), the charging circuit may alternate between using paths  438  and  440  to power high-voltage subsystems  406 . In other words, the charging circuit may power high-voltage subsystems  406  from the up-converted target voltage from inductor  410 , FET  426 , and/or path  438 , or the charging circuit may power high-voltage subsystems  406  directly from the target voltage of battery  434  along path  440 , which bypasses boosting of the target voltage. Such switching between boost and bypass modes may facilitate efficient operation of the charging circuit by allowing the charging circuit to respond to current and/or load transients. For example, a current transient on high-voltage subsystems  406  may cause momentary periods in which powering high-voltage subsystems  406  along path  440  is more efficient than boosting the target voltage through path  438 . As a result, the charging circuit may include functionality to detect current transients on high-voltage subsystems  406  and select the most efficient path  438 - 440  for powering high-voltage subsystems  406  in response to the current transients. 
       FIG. 4D  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. In particular,  FIG. 4D  shows the operation of the charging circuit of  FIG. 4A  during discharging of battery  434  in a low-voltage state. In the low-voltage state, battery  434  may have a battery voltage that can be used directly by low-voltage subsystems  304  but not high-voltage subsystems  306  (e.g., between 3.0V and 3.4V). 
     Because battery  434  is discharging, an input voltage from power source  402  is not available. In turn, control circuit  412  may disable FETs  418 - 422  to prevent current from battery  434  from flowing to an unavailable and/or improperly connected power source  402 . The battery voltage of battery  434  may be used to directly power low-voltage subsystems  404  along a path  442  that includes FET  428 , which is enabled to allow discharging of battery  434 . FET  428  may subsequently be configured to stop charging once the cutoff voltage of battery  434  is reached to discontinue discharging of the battery. More specifically, once the battery has discharged to the cutoff voltage, all FETs  418 - 432  may be switched off until power source  402  is detected. 
     During discharge of battery  434  in the low-voltage state, the battery voltage of battery  434  may not be sufficient to directly power high-voltage subsystems  406 . Instead, the battery voltage may be boosted along a boost path  444  that includes inductor  410  and FET  432 . To cause current to flow in the “reverse” direction along boost path  444 , control circuit  416  may turn FET  430  off and FET  432  on. In addition, control circuit  412  may use FETs  426  and  432  and inductor  410  to up-convert the battery voltage to V HI , which is used to power high-voltage subsystems  406 . For example, control circuit  412  may turn FET  424  off to direct current flowing in the reverse direction across inductor  410  to high-voltage subsystems  406 . Control circuit  412  may alternately switch FETs  426  and  432  on and off as part of a servomechanism feedback loop that controls the input terminal of inductor  410  and V HI  to at or above the voltage requirement of high-voltage subsystems  406  (e.g., 3.4V or higher). 
       FIG. 4E  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. In particular,  FIG. 4E  shows the operation of the charging circuit of  FIG. 4A  during discharging of battery  434  in a low-voltage state with an external load  448  connected to the charging circuit in lieu of power source  402 . For example, external load  448  may be a peripheral device that uses the same connector (e.g., a Universal Serial Bus (USB) connector) as power source  402  to receive power from battery  434 . 
     As with the operation of the charging circuit in  FIG. 4D , FET  428  is enabled, low-voltage subsystems  404  are powered directly from battery  434  along path  442 , and high-voltage subsystems  406  are powered from an up-converted battery voltage using inductor  410 , FET  426 , and path  444 . To provide power to external load  448 , control circuit  412  may use inductor  408  and FETs  420 - 422  to up-convert the battery voltage to at or above the voltage requirement of external load  448 . For example, control circuit  412  may use inductor  408  and FETs  420 - 422  to reverse boost the battery voltage to 5V, which is higher than the 3.4V-3.6V required by high-voltage subsystems  406 . To generate an output voltage for powering external load  448 , control circuit  412  may switch FETs  420 - 422  on and off in complementary fashions as part of a servomechanism feedback loop that boosts the battery voltage in the reverse direction to produce 5V at the input terminal of inductor  408 . External load  448  may then be powered by current flowing along a path  446  that includes inductor  408  and FETs  418 - 420 . 
       FIG. 4F  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. In particular,  FIG. 4F  shows the operation of the charging circuit of  FIG. 4A  during discharging of battery  434  in a high-voltage state. In the high-voltage state, battery  434  may have a voltage that can be used directly by all subsystems (e.g., greater than 3.4V-3.6V). 
     Like  FIGS. 4D-4E , battery  434  has a battery voltage that can be used to directly power low-voltage subsystems  404  along path  442 . Moreover, because the battery voltage is higher than the voltage-requirement of high-voltage subsystems  406 , the battery voltage may be used to directly power high-voltage subsystems  406  along a bypass path  448  to high-voltage subsystems  406 . To allow current from battery  434  to flow along path  448 , control circuit  416  may turn FET  430  on and FET  432  off, and control circuit  412  may turn FETs  420 - 426  off. The battery voltage is thus neither up-converted nor down-converted to power low-voltage subsystems  404  and high-voltage subsystems  406 . 
     During discharging of battery  434  that is between the low-voltage state and high-voltage state (e.g., 3.4V to 3.6V), the charging circuit may alternate between using paths  444  and  448  to power high-voltage subsystems  406 . In other words, the charging circuit may power high-voltage subsystems  406  from the up-converted battery voltage from inductor  410 , FET  426 , and/or path  444 , or the charging circuit may power high-voltage subsystems  406  directly from the battery voltage of battery  434  along path  448 , which bypasses up-converting of the battery voltage. Such switching between boost and bypass modes may facilitate efficient operation of the charging circuit by allowing the charging circuit to respond to current and/or load transients. For example, a current transient on high-voltage subsystems  406  may cause momentary periods in which powering high-voltage subsystems  406  along path  448  is more efficient than boosting the target voltage through path  444 . As a result, the charging circuit may include functionality to detect current transients on high-voltage subsystems  406  and select the most efficient path for powering high-voltage subsystems  406  in response to the current transients. 
     If an external load (e.g., external load  448  of  FIG. 4E ) is coupled to the charging circuit, paths  442  and  448  may continue to be used to supply the battery voltage directly to both low-voltage subsystems  404  and high-voltage subsystems  406 . Path  446  may then be used by the charging circuit to up-convert the battery voltage into an output voltage that is at or above the voltage requirement of the external load. For example, control circuit  412  may use inductor  408  and FETs  420 - 422  to reverse boost the battery voltage to 5V, which is higher than the 3.4V-3.6V required by high-voltage subsystems  406 . To generate the 5V output voltage for powering external load  448 , control circuit  412  may switch FETs  420 - 422  on and off in complementary fashions as part of a servomechanism feedback loop that boosts the battery voltage in the reverse direction. Current from battery  434  may also flow along path  446  to power the external load. 
     In the charging circuit of  FIGS. 4A-4F , the high-voltage subsystem rail may be regulated twice: once during bucking from the input voltage into a target voltage of battery  434 , then a second time during boosting from battery  434  to high-voltage subsystems  406 . As a result, the efficiency of the high-voltage subsystem rail may be reduced by the boost stage efficiency multiplied by the buck stage efficiency. 
     To improve the efficiency of the high-voltage subsystem rail, the high-voltage subsystem rail may be regulated directly from the input voltage instead of from the low-voltage subsystem rail. To accomplish this type of regulation, a single power FET may be added to the charging circuit of  FIGS. 4A-4F . In particular,  FIG. 4G  shows the operation of the charging circuit of  FIG. 4A  during low-current charging of battery  434  and the added FET  450 . During operation of the charging circuit, FETs  432  and  450  are switched off, and FETs  428 - 430  are enabled in bypass mode to allow charging of battery  434  and powering of high-voltage subsystems  406  from down-conversion of the input voltage along a low-voltage subsystem rail  452  and a high-voltage subsystem rail  454 , respectively. 
     FET  450  may allow both phases of the switching converter to operate independently as two separate bucks. Inductor  410  may be used in the first phase to generate the voltage for high-voltage subsystems  406  along high-voltage subsystem rail  454 , and inductor  408  may be used in the second phase to supply power to low-voltage subsystems  404  along low-voltage subsystem rail  452 . As described above, the same mechanism may be accomplished by operating one or more FETs (e.g., FET  430 ) in a linear-regulation mode, which is very inefficient and renders high-voltage inputs unusable due to power dissipation with large downstream loads. The operation of the charging circuit of  FIG. 4G  provides a significantly more efficient step-down regulation architecture, with the difference in power losses between the two methods expressed as I 2 R for linear regulation and less than 15% of the input power for step-down regulation. 
     Inductor  410  may be used to supply power to high-voltage subsystem rail  454  from the input voltage whenever battery charge currents are low enough that two phases are not required. Such low battery charge currents may be found during, for example, the coupling of an underpowered power source  420  to the charging circuit. Because the underpowered power source  420  cannot supply a full charge current to battery  434 , control circuit  412  may use inductor  410  to supply high-voltage subsystem rail  454  by down-converting the input voltage from power source  402 . In a second example, low battery charge currents may occur during the end of a charge cycle, when the charging circuit only needs to supply current to low-voltage subsystems  404  and high-voltage subsystems  406 . In a third example, low battery charge currents may coincide with constant-voltage charging of battery  434 . Once the charge current falls to approximately 50% of the full charge current, control circuit  412  may down-convert the input voltage to supply high-voltage subsystem rail  454 . Selection of the operating mode of the charging circuit may be done via hardware and/or software and can depend on the state-of-charge of battery  434 , system thermal measurements, and/or other system-level information. 
       FIGS. 4H-4J  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. In particular,  4 H shows the operation of the charging circuit of  FIG. 4G  during high-current charging of battery  434 . Control circuit  412  may operate in a first phase that uses inductor  410  and FETs  424 - 426  to down-convert the input voltage to supply high-voltage subsystem rail  454 . Control circuit  412  may also operate in a second phase that uses inductor  408  and FETs  420 - 422  to down-convert the input voltage to supply low-voltage subsystem rail  452  and charge battery  434  at the target voltage of battery  434 . 
     In the charging circuit of  FIG. 4H , FET  432  may be switched off, and FET  430  may be operated as a linear regulator to supply high-voltage subsystem rail  454  from the input voltage. Alternatively, FET  430  may be used as a bypass switch to improve power losses if the voltage requirements of high-voltage subsystem rail  454  are compatible with the input voltage from power source  402 . 
       FIG. 4I  shows the operation of the charging circuit of  FIG. 4G  during discharge of a low-voltage battery  434 , and  FIG. 4J  shows the operation of the charging circuit of  FIG. 4G  during discharge of a high-voltage battery  434 . Using the charging circuit to discharge battery  434  in  FIGS. 4I-4J  is similar to the operation of the charging circuit during discharge of battery  434  in  FIGS. 4D-4F . In  FIG. 4I , inductor  410  is used to boost the battery voltage from battery  434  to supply high-voltage subsystem rail  454 . During discharge of a high-voltage battery  434  in  FIG. 4J , the voltage of high-voltage subsystem rail  454  may be linearly regulated from FET  430 , which may increase power losses. 
     To further reduce power losses over the charging circuit of  FIGS. 4G-4J , inductor  410  may be converted into a four-switch buck-boost.  FIGS. 4K-4O  shows the operation of a charging circuit for a portable electronic device in accordance with the disclosed embodiments. The charging circuit of  FIGS. 4K-4O  includes one more FET  456  than the charging circuit of  FIGS. 4G-4J . FET  456  may allow inductor  410  to be converted into a four-switch buck-boost, which enables efficient powering of high-voltage subsystem rail  454  for all charging, discharging, high-battery-voltage, and low-battery-voltage cases. 
     More specifically,  FIG. 4K  shows the operation of the charging circuit during discharge of a high-voltage battery  434 . In  FIG. 4K , FETs  418 - 426  and  430  are off, FET  432  is operated in bypass mode, and FETs  450  and  456  are operated in buck mode to down-convert the battery voltage from battery  434  before supplying high-voltage subsystem rail  454 . 
       FIG. 4L  shows the operation of the charging circuit during low-current charging of a low-voltage battery  434 . In  FIG. 4L , FETs  432 ,  450  and  456  are off, FETs  424 - 426  and inductor  410  are used to down-convert the input voltage to supply high-voltage subsystem rail  454 , and FETs  428 - 430  and inductor  408  are used to down-convert the input voltage to supply low-voltage subsystem rail  452  and charge battery  434  at the target voltage of battery  434 . FETs  428 - 430  are operated in bypass mode to enable charging of battery  434  and powering of high-voltage subsystems  406  from down-conversion of the input voltage along high-voltage subsystem rail  454 . 
       FIG. 4M  shows the operation of the charging circuit during discharge of a low-voltage battery  434 . In  FIG. 4M , FETs  418 - 424 ,  430 , and  456  are off. Low-voltage subsystem rail  452  is supplied directly from the battery voltage of battery  434 . FET  450  is operated in bypass mode to allow inductor  410  and FETs  426  and  432  to up-convert the battery voltage from battery  434  into a voltage requirement of high-voltage subsystems  406 . 
       FIG. 4N  shows the operation of the charging circuit during high-current charging of a high-voltage battery  434 . In  FIG. 4N , high-voltage subsystem rail  454  may be supplied linearly by FET  430  when charging at high currents. FETs  432  and  456  are switched off, and FET  450  is operated in bypass mode to allow the input voltage to be down-converted into a target voltage of battery  434  that is used to charge battery  434  and supply low-voltage subsystem rail  452 . 
       FIG. 4O  shows the operation of the charging circuit during low-current charging of a high-voltage battery  434 . In  FIG. 4O , FETs  432 ,  450  and  456  are off. FETs  428 - 430  are operated in bypass mode to allow charging of battery  434  and powering of high-voltage subsystems  406 . The input voltage is down-converted into the target voltage of battery  434  by inductor  408  and FETs  420 - 422 , and the target voltage is used to charge battery  434  and supply low-voltage subsystem rail  452 . The input voltage is also down-converted to supply high-voltage subsystem rail  454 . 
       FIG. 5  shows a charging system for a portable electronic device in accordance with the disclosed embodiments. The charging system of  FIG. 5  may convert an input voltage from a power source  502  and/or a battery voltage from a battery  522  into a set of output voltages for charging battery  522  and/or powering one or more low-voltage subsystems  504  and one or more high-voltage subsystems  506 . 
     As shown in  FIG. 5 , the charging system includes a switching converter  508 . Switching converter  508  may include one or more inductors and a set of switching mechanisms such as FETs, diodes, and/or other electronic switching components. For example, switching converter  508  may be provided by the multi-phase switching converter shown in  FIG. 4A , which includes two inductors (e.g., inductors  408 - 410 ), each with an input terminal and a load terminal. Inductor  408  may be associated with two switching mechanisms (e.g., as provided by FETs  420 - 422 ), which are configured to couple the input terminal of inductor  408  to the input voltage or a reference voltage (e.g., ground). Inductor  410  may also be associated with a number of switching mechanisms (e.g., as provided by FETs  424 - 426  and  430 - 432 ), which are configured to couple the input terminal of inductor  410  to the input voltage, the reference voltage, and high-voltage subsystems  406  and the load terminal of inductor  410  to high-voltage subsystems  406 , respectively. 
     The charging system may also include switching mechanisms  510 - 516 , which collectively may be used to couple power source  502 , battery  522 , high-voltage subsystems  506 , and/or low-voltage subsystems  504  to one another and/or switching converter  508 . Each switching mechanism may selectively couple different voltage nodes and may include a switch, a FET (e.g., FETs  418 - 432  of  FIG. 4A ), a diode, and/or another switching mechanism. For example, switching mechanism  510  may provide reverse voltage protection from an improperly functioning power source  502  (e.g., a power source with a faulty design or an incorrectly connected power source  502 ) and may prevent current flowing from the voltage node V X  to power source  502  (shown there as V BUS ). Switching mechanism  516  may couple high-voltage subsystems  506  to a boost path, which is used by switching converter  508  to up-convert the battery voltage and/or target voltage of battery  522  V BAT  to power high-voltage subsystems  506 . Switching mechanism  514  may couple high-voltage subsystems  506  to a bypass path, which is used by the charging system to power high-voltage subsystems  506  directly from the battery voltage and/or target voltage. Switching mechanism  512  may selectively couple voltage node V LO  to battery  522  to enable or disable charging or discharging of battery  522 . 
     Inductors in switching converter  508  may additionally be grouped into two or more inductor groups. In other words, switching converter  508  may include a first inductor group that is used to down-convert the input voltage into the target voltage of battery  522  and/or up-convert the battery voltage of battery  522  to power an external load that can take the place of power source  502 . Switching converter  508  may also include a second inductor group that is used to up-convert the target voltage and/or battery voltage to power high-voltage subsystems  506 . 
     If an inductor group includes two or more inductors, the membership of an inductor in the inductor group may be switched to another inductor group to facilitate operation of the charging system. For example, one of two inductors in the first inductor group may be switched to the second inductor group with one inductor to enhance the operation of the second inductor group. In addition, the switch may be triggered if the difference between the voltage requirement of high-voltage subsystems  506  and the battery or target voltage of battery  522  changes beyond a threshold. For example, an inductor may be switched from the first inductor group to the second inductor group during discharge of battery  522  after the battery voltage falls to more than 0.4V below the voltage requirement of high-voltage subsystems  506  to facilitate up-converting of the battery voltage to the voltage requirement. Conversely, an inductor may be switched from the second inductor group to the first inductor group during charging of battery  522  after the battery voltage increases to near or above the voltage requirement of high-voltage subsystems  506  to facilitate efficient charging of battery  522 . 
       FIG. 6  shows a flowchart illustrating the process of managing use of a battery in a portable electronic device in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 6  should not be construed as limiting the scope of the embodiments. 
     Initially, a charging circuit for converting an input voltage from a power source into a set of output voltages for charging a battery and powering a low-voltage subsystem and a high-voltage subsystem in a portable electronic device is operated (operation  602 ). The charging circuit may include a first inductor group and a second inductor group. Each inductor group may include one or more inductors that can be configured to boost or buck the input voltage and/or a target voltage of the battery. During operation of the charging circuit, the first inductor group is used to down-convert the input voltage to a target voltage of the battery upon detecting the input voltage and a battery voltage that is below a fully charged state (operation  604 ) of the battery. In other words, the first inductor group may be used to charge the battery at a target voltage of the battery, which is lower than the input voltage. 
     Additional operation of the charging circuit may be based on a voltage state of the battery (operation  606 ). If the battery is in a low-voltage state, the second inductor group is used to up-convert the target voltage to power the high-voltage subsystem (operation  608 ). For example, the target voltage may be up-converted (e.g., boosted) because the low-voltage state of the battery precludes direct powering of the high-power subsystem from the target voltage used to charge the battery. 
     If the battery is in a high-voltage state, both inductor groups are used to down-convert the input voltage to the target voltage (operation  612 ) and charge the battery and power both subsystems from the input current of the power source (operation  614 ). In the high-voltage state, the target voltage is at or above the voltage requirement of the high-voltage subsystems. As a result, the use of both inductor groups to supply input current from the power source and down-convert the input voltage to the target voltage may facilitate efficient charging of the battery and allow both subsystems to be powered from the same target voltage. 
     If the battery is between the low-voltage state and the high-voltage state, the high-voltage subsystem is powered from the up-converted target voltage from the second inductor group and/or the target voltage from both inductor groups (operation  610 ). In other words, the high-voltage subsystem may be powered by the same operation of the charging circuit as either the low-voltage state (e.g., up-converted target voltage) or the high-voltage state (e.g., target voltage), depending on current transients and/or other factors associated with the high-voltage subsystem and/or charging circuit. 
       FIG. 7  shows a flowchart illustrating the process of managing use of a battery in a portable electronic device in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 7  should not be construed as limiting the scope of the embodiments. 
     Initially, a charging circuit for converting a battery voltage from the battery into a set of output voltages for powering a low-voltage subsystem and a high-voltage subsystem in a portable electronic device is operated (operation  702 ). The charging circuit may include a first inductor group and a second inductor group. During operation of the charging circuit, the charging circuit is used to directly power the low-voltage subsystem from the battery voltage during discharge of the battery (operation  704 ). The low-voltage subsystem may thus have a voltage requirement that is at or below the cutoff voltage of the battery. In addition, discharging of the battery may be discontinued once the battery reaches the cutoff voltage. 
     Additional operation of the charging circuit may be based on a voltage state of the battery (operation  706 ). If the battery is in a low-voltage state, the second inductor group is used to up-convert the battery voltage to power the high-voltage subsystem (operation  708 ). For example, the battery voltage may be up-converted (e.g., boosted) because the low-voltage state of the battery precludes direct powering of the high-power subsystem from the battery voltage of the discharging battery. 
     If the battery is in a high-voltage state, the high-voltage subsystem is powered from the battery voltage along a bypass path to the high-voltage subsystem (operation  712 ). In the high-voltage state, the target voltage is at or above the voltage requirement of the high-voltage subsystem. As a result, the bypass path may bypass the second inductor group and allow the high-voltage subsystem to be powered directly from the battery voltage. 
     If the battery is in between the low-voltage state and the high-voltage state, the high-voltage subsystem is powered from the up-converted battery voltage and/or the battery voltage along the bypass path (operation  710 ). The high-voltage subsystem may thus be powered by the same operation of the charging circuit as either the low-voltage state (e.g., up-converted battery voltage) or the high-voltage state (e.g., target voltage and bypass path), depending on current transients and/or other factors associated with the high-voltage subsystem and/or charging circuit. 
     The coupling of an external load to the portable electronic device may also be detected (operation  714 ). If no external load is detected, the charging circuit may continue to be operated based on the voltage state of the battery. If an external load is detected, the first inductor group is used to up-convert the battery voltage to power the external load (operation  716 ). For example, the first inductor group is used to generate an output voltage that is higher than the battery voltage and meets the voltage requirement of the external load. 
       FIG. 8  shows a flowchart illustrating the process of managing use of a battery in a portable electronic device in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 8  should not be construed as limiting the scope of the embodiments. 
     Initially, a charging circuit for converting an input voltage from a power source and/or a battery voltage from a battery into a set of output voltages for charging the battery and powering a low-voltage subsystem and a high-voltage subsystem in the portable electronic device is operated (operation  802 ). The charging circuit may include two inductor groups, each of which includes one or more inductors. The operation of the charging circuit may include down-converting the input voltage, up-converting a target voltage of the battery, and/or up-converting a battery voltage of the battery. 
     Next, a membership of an inductor is switched between the inductor groups to facilitate operation of the charging circuit upon detecting a change between a voltage requirement of the high-voltage subsystem and a battery voltage of the battery beyond a threshold (operation  804 ). For example, the inductor may be switched between a first inductor group and a second inductor group to facilitate efficient charging of battery and/or boosting of the battery voltage to the voltage requirement of the high-voltage subsystem. 
     The above-described charging circuit can generally be used in any type of electronic device. For example,  FIG. 9  illustrates a portable electronic device  900  which includes a processor  902 , a memory  904  and a display  908 , which are all powered by a power supply  906 . Portable electronic device  900  may correspond to a laptop computer, tablet computer, mobile phone, portable media player, digital camera, and/or other type of battery-powered electronic device. Power supply  906  may include a switching converter such as the converter shown in  FIG. 4A , a boost converter, an inverting converter, a Ćuk converter, a SEPIC, a Zeta converter, and/or a buck-boost converter. The switching converter may include a first inductor group and a second inductor group. Power supply  906  may also include a control circuit that uses the switching converter to convert an input voltage from a power source and/or a battery voltage from a battery in portable electronic device  900  into a set of output voltages for charging the battery and powering two or more subsystems in portable electronic device  900 , including a low-voltage subsystem and a high-voltage subsystem. For example, the control circuit may use the first and second inductor groups to independently buck and/or boost the input voltage and/or battery voltage into a set of output voltages for charging the battery and powering the low-voltage subsystem and the high-voltage subsystem. 
     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: 20180809
Publication Date: 20211019
Grant Date: 20211019
Priority Date: 20140902
Inventors: LANGLINAIS, Jamie
YOSHIMOTO, MARK A.
CHEN, LIN
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/263", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/007186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007182", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007184", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/263", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/158", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007184", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/263", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M3/158", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/158", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007182", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00714", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007182", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00714", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/007182", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/158", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/158", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0078", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/263", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2007/0067", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/007184", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/0068", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 53514423