1. Field
The disclosed embodiments relate to batteries for portable electronic devices. More specifically, the disclosed embodiments relate to techniques for reusing inductors of battery chargers to boost voltages during battery discharge.
2. 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 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,
The disclosed embodiments provide a system that manages use of a battery in a portable electronic device. During operation, the system provides 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 discharging of the battery in a low-voltage state, the system uses the charging circuit to directly power the low-voltage subsystem from a battery voltage of the battery and up-convert the battery voltage to power the high-voltage subsystem.
In some embodiments, upon detecting the input voltage from an underpowered power source and the low-voltage state in the battery, the system uses the charging circuit to power the low-voltage subsystem from a target voltage of the battery and power the high-voltage subsystem from the underpowered power source. Moreover, upon detecting a voltage of the low-voltage subsystem below an open-circuit voltage of the battery, the system uses the charging circuit to power the high-voltage subsystem from a sum of currents from the input voltage and the up-converted battery voltage.
In some embodiments, upon detecting the input voltage from an underpowered power source and a high-voltage state in the battery, the system uses the charging circuit to power the low-voltage subsystem and the high-voltage subsystem from a target voltage of the battery that is higher than a voltage requirement of the high-voltage subsystem. Moreover, upon detecting a voltage of the low-voltage subsystem below an open-circuit voltage of the battery, the system uses the charging circuit to power the high-voltage subsystem by summing currents from the input adapter and the up-converted battery voltage.
In some embodiments, upon detecting the input voltage from an underpowered power source and an undervoltage state in the battery, the system powers off the portable electronic device and uses the charging circuit to charge the battery from the input voltage.
In some embodiments, upon detecting the input voltage from the power source and a low-voltage state in the battery, the system uses the charging circuit to:
In some embodiments, upon detecting the input voltage from the power source and a fully charged state in the battery, the system uses the charging circuit to discontinue charging of the battery and power the low-voltage subsystem and the high-voltage subsystem from a target voltage that is higher than the battery voltage of the battery in the fully charged state.
In some embodiments, the charging circuit includes:
In some embodiments, the first, second, and third switching mechanisms include field-effect transistors (FETs).
In some embodiments, the battery voltage in the low-voltage state is lower than a voltage requirement of the high-voltage subsystem.
In the figures, like reference numerals refer to the same figure elements.
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 to one or more subsystems of the portable electronic device. In some instances, the charging circuit may include a reused inductor for up-converting (e.g., boosting) voltages in the portable electronic device. In these instances, the inductor may produce a down-converted voltage when the charging circuit is in a first configuration or set of configurations, and may produce an up-converted voltage when the charging circuit is in a second configuration or set of configurations. The reused inductor may avoid an increase in board space occupied by the charging circuit, thereby allowing unused capacity in the battery to be accessed without reducing the size and/or runtime of the battery.
A standard boost converter could be added between battery 214 and systems 204 to boost the battery voltage of battery 214 to or above a minimum operating voltage (e.g., greater than 3.4V) as battery 214 discharges to a cutoff voltage, such as 3.0V. However, this option may be undesirable because the size of the boost converter (especially its inductor) would contribute significantly to the available board space. Taking away board space for a circuit in a space-constrained portable electronic device typically results in a smaller battery size, which in turn may result in shorter runtimes for the portable electronic device. This may offset any capacity gains from boosting the battery voltage to the voltage required by device subsystems. Discussed here are mechanisms for providing boost functionality in a battery-charging circuit without significantly increasing the board space occupied by the battery-charging circuit.
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
As shown in
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 incorrectly connected power source 302) and may prevent current flowing from the voltage node VX to the power source 302 (shown there as VBUS). The switching converter 330 may couple voltage node VX with a voltage node VLO, which may in turn be coupled to low-voltage subsystems 304. Regulator 338 may selectively couple voltage node VX with a voltage node VHI either directly or by linearly regulating VHI to a voltage less than VX, which may in turn be coupled to high-voltage subsystems 306. Switching mechanism 336 may selectively couple voltage node VHI with voltage node VLO, or in some instances may selectively couple voltage node VHI with battery 322. Regulator 334 may selectively couple voltage node VLO to battery 322 either directly or by linearly regulating the battery voltage to a voltage less than VLO. 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.
As with the charging system of
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
Regulators 338, 342, and 346 couple voltage node VX (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 VX. For example, as shown in
During operation of the charging system, there are three charging power source 302 states to consider: standard charging from power source 302, charging with an underpowered power source 302, and discharging from battery 322. An underpowered power source is any power source (e.g., power source 302) that cannot provide the desired power to the system by reaching the adapter current iBUS or adapter voltage VBUS limits. For example, power source 302 may be underpowered if current iBUS or VBUS limits are designed for AC mains electricity with voltages of 100-240V but power source 302 is plugged into a power source with a lower current or voltage than the iBUS or VBUS limits, such as a Universal Serial Bus (USB) port on a computer system.
Similarly, there are four or more battery voltage states to consider: an undervoltage state, one or more low-voltage state, a high-voltage state, and 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), 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
The combination of adapter states and battery 322 voltage states gives 12 unique states to consider. The following sections describe the detailed operations of the charging systems of
During standard charging with an undervoltage battery 322, the control circuit may use power source 302 to charge battery 322. The control circuit may also use switching converter 330 to convert the input voltage from power source 302 into one or more output voltages for powering the subsystems. In these instances, the input voltage of the power source may be used to provide a charging voltage to the battery and a voltage to each subsystem that meets the required voltage for that subsystem.
For example, in the charging circuit shown in
5
During standard charging with a low-voltage battery, the control circuit may use power source 302 to charge battery 322. The control circuit may also use switching converter 330 to convert the input voltage from power source 302 into one or more output voltages for powering the subsystems, which may include a target voltage of battery 322. In these instances, the input voltage of the power source may be used to provide a charging voltage to the battery and a voltage to each subsystem that meets the required voltage for that subsystem.
For example, the control circuit may configure the charging circuit of
To improve efficiency, FET C 314 could instead be configured to operate as an ideal diode and prevent current from flowing into ground (e.g., a reference voltage). If the servo mechanism (e.g., the control circuit) suddenly becomes adapter-limited, causing a transition to charging with an underpowered power source and a low-voltage battery as discussed in State 6 below, then FET C 314 may no longer be configured as an ideal diode and may instead be switching in a complementary fashion with FET B 312, allowing current to be boosted from battery 322.
During standard charging with a high-voltage battery, the control circuit may use power source 302 to charge battery 322. The control circuit may also use switching converter 330 to convert the input voltage from power source 302 into a target voltage of battery 322, which is also used to power one or more subsystems of the portable electronic device. In these instances, the input voltage of the power source may be used to provide a charging voltage to the battery and a voltage to each subsystem that meets the required voltage for that subsystem.
For example, the control circuit may configure the charging circuit of
As discussed in State 2 (Standard Charging with a Low-Voltage Battery), FET C 314 could instead be configured to operate as an ideal diode to improve efficiency at the expense of being able to react quickly to a transition to charging with an underpowered power source and a high-voltage battery, which is discussed in State 7 below.
During standard charging with a fully charged battery, the control circuit may discontinue charging of battery 322 from power source 302. The control circuit may also use switching converter 330 to convert the input voltage from power source 302 into an output voltage for powering the subsystems of the portable electronic device. The output voltage may be higher than the battery voltage of battery 322 in the fully charged state.
For example, the control circuit may configure the charging circuit of
As discussed in State 2 (Standard Charging with a Low-Voltage Battery), FET C 314 could instead be configured to operate as an ideal diode to improve efficiency at the expense of being able to react quickly to a transition to charging with an underpowered power source and a fully charged battery, which is discussed in State 8 below.
During charging with an underpowered power source 302 and an undervoltage battery 322, the control circuit may power off the portable electronic device and use all of the limited power from power source 302 to charge battery 322. For example, the control circuit may configure the charging circuit of
During charging with an underpowered power source 302 and a low-voltage battery 322, the control circuit may power the low-voltage subsystem from a target voltage of the battery and power the high-voltage subsystem from the underpowered power source 302. If the control circuit detects a voltage of the low-voltage subsystem below an open-circuit voltage of battery 322, the control circuit may power the high-voltage subsystem from a sum of currents from the input voltage and the up-converted battery voltage from switching converter 330.
For example, the control circuit may configure the charging circuit of
If VLO is below the open-circuit voltage of battery 322, then battery 322 will be discharging instead of charging. In this case, charge is boosted from the battery at VLO by inductor 308 and switching FETs B 312 and C 314 to VX. Low-voltage subsystems 304 may be powered by battery 322, and high-voltage subsystems 306 may be powered by the sum of currents from the adapter power and the boosted battery power at VHI
During charging with an underpowered power source 302 and a high-voltage battery 322, the control circuit may power the low-voltage subsystem and the high-voltage subsystem from a target voltage of battery 322 that is higher than a voltage requirement of the high-voltage subsystem. If the control circuit detects a voltage of the low-voltage subsystem below an open-circuit voltage of battery 322, the control circuit may power the power the low-voltage subsystem and the high-voltage subsystem from a sum of currents from the input voltage and the up-converted battery voltage from switching converter 330.
For example, the control circuit may configure the charging circuit of
If VLO is below the open-circuit voltage of battery 322, then battery 322 will be discharging instead of charging. In this case, high-voltage subsystems 306 may be powered by power source 302 via the buck converter, supplemented by current from battery 322.
During charging with an underpowered power source 302 and a fully charged battery 322, the control circuit may discontinue charging of battery 322 from power source 302. The control circuit may also use switching converter 330 to generate an output voltage that powers all subsystems in the portable electronic device. If the output voltage is less than the battery voltage of battery 322, the control circuit may supplement the output voltage with power from battery 322.
For example, the control circuit may configure the charging circuit of
If the buck converter voltage is less than the battery voltage, then FET D 316 conducts as an ideal diode, allowing the battery power to supplement the adapter power, just like State 7 (Charging with an Underpowered Power Source and a High-Voltage Battery).
During discharging with an undervoltage battery 322, there is no useful power in the system, and the portable electronic device is switched off. For example, all FETs 310-320 in the charging circuit of
During discharging with a low-voltage battery, the control circuit may directly power the low-voltage subsystem from a battery voltage of battery 322 and up-convert the battery voltage to power the high-voltage subsystem. For example, the control circuit may configure the charging circuit of
During discharging with a low-voltage battery, the control circuit may directly power all subsystems from the battery voltage of battery 322. For example, the control circuit may configure the charging circuit of
The conditions are identical to State 11, which describes discharging with a high-voltage battery.
Transitions between the states occur as the voltage of battery 322 voltage, power source 302 is plugged in or is unplugged, or a large current transient occurs on one of the system loads. The proposed charger gracefully handles these transitions, with the certain transitions described in detail here.
A typical transition occurs when transitioning between a high-voltage battery 322 and a low-voltage battery 322. In this case, the voltage for high-voltage subsystems 306 VHI will transition from the minimum high-voltage level for high-voltage subsystems 306 (e.g., 3.4V) to VHI
A more challenging transition occurs when a current pulse occurs on the high-voltage systems, with the system in State 2 (Charging with a Low-Voltage Battery). In this case, the power to the high-voltage systems is provided by FET F 320 operating linearly to maintain VHI at VHI
If the current pulse on high-voltage subsystems 306 is so large that the buck servo mechanism becomes limited by the adapter current or adapter voltage, then the power to high-voltage subsystems 306 may be supplemented by up converting the battery voltage described by State 6 (Charging with an Underpowered Power Source and a Low-Voltage Battery).
In other instances, a current pulse on high-voltage subsystems 306, in State 11 (Discharging with a High-Voltage Battery), may cause a transition to State 10 (Discharging with a Low-Voltage Battery) due to the pulse-incurred voltage droop on the VLO rail. Before the pulse, high-voltage subsystems 306 are directly connected to battery 322, and the VX voltage is also equal to the battery voltage due to the operation of FET B 312 as an ideal diode. When the pulse occurs, FET F 320, which is operating linearly to keep VHI above the voltage requirement of high-voltage subsystems 306 (e.g., 3.4V), will transfer charge from VX to VHI as the boost servo mechanism controlling FET C 314 begins switching to keep VX at 3.4V.
In still other instances, disconnection of power source 302 during State 2 (Charging with a Low-Voltage Battery) may result in a transition to State 10 (Discharging with a Low-Voltage Battery). In this case, FETs B 312 and C 314 are originally switching as a buck converter to charge battery 322 connected to VLO via FET D 316 to a voltage between the cutoff voltage of battery 322 (e.g., 3.0V) and the voltage requirement of high-voltage subsystems 306 (e.g., 3.4V). After the unplug event, the current through inductor 308 may need to reverse direction as quickly as possible, as FETs B 312 and C 314 are now switching as a boost converter to control VHI to VHI
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 provided (operation 402). The charging circuit may include a bidirectional converter and a control circuit. The bidirectional converter may include an inductor with an input terminal and a load terminal and three switching mechanisms, which are configured to couple the input terminal to either the power source or a reference voltage; couple the load terminal to the battery, the high-voltage subsystem, and the low-voltage subsystem; and couple the input voltage to the high-voltage subsystem. The switching mechanisms may be provided by FETs and/or other switching components. Alternatively, other types of bidirectional converters, such as Ćuk converters, inverting converters, boost converters, single-ended primary-inductor converters (SEPICs), Zeta converters, and/or buck-boost converters, may be used.
Next, the input voltage from the power source is detected (operation 404). For example, the input voltage may be detected from a power source that is plugged in to a power outlet. The charging circuit may then be operated based on the battery state (operation 406) of the battery in the portable electronic device. If the battery is in an undervoltage state, the charging circuit is used to provide different output voltages for charging the battery and powering the low-voltage and high-voltage subsystems (operation 408). For example, the charging circuit may produce a target voltage for charging the battery that is less than the cutoff voltage of the battery, a down-converted voltage (e.g., a bucked voltage) for powering the low-voltage subsystem at or above the cutoff voltage, and a higher voltage from the power source for powering the high-voltage subsystem at or above the voltage requirement of the high-voltage subsystem.
If the battery is in a low-voltage state, the charging circuit is used to power the low-voltage subsystem from the target voltage of the battery and the high-voltage subsystem from the power source (operation 410). For example, the target voltage may be between the cutoff voltage of the battery (e.g., 3.0V) and the voltage requirement of the high-voltage subsystem, and the high-voltage subsystem may be powered from a voltage that is less than or equal to the maximum voltage limit of the high-voltage subsystem.
If the battery is in a high-voltage state, the charging circuit is used to power all subsystems from the target voltage of the battery (operation 412). For example, the same target voltage may be used to power both the low-voltage and high-voltage subsystems and charge the battery.
Finally, if the battery is in a fully charged state, charging of the battery is discontinued (operation 414), and both subsystems are powered from a target voltage that is higher than the battery voltage of the battery in the fully charged state (operation 416). For example, the charging circuit may be used to convert the input voltage into a target voltage that is 100 mV higher than the battery's fully charged voltage to provide voltage headroom and avoid discharging of the battery during current pulses.
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 provided (operation 502). Next, the input voltage from an underpowered power source is detected (operation 504). For example, the input voltage may be detected from a power source (e.g., a power adapter) that is plugged in to a USB port on a computer system and/or other portable electronic device. Alternatively, the power source may be temporarily underpowered during a current pulse on one or both subsystems.
The charging circuit may then be operated based on the battery state (operation 506) of the battery in the portable electronic device. If the battery is in an undervoltage state, the portable electronic device is powered off (operation 508), and the charging circuit is used to charge the battery from the input voltage (operation 510). The portable electronic device may remain off until the charging circuit transitions into standard charging from a power source and/or the battery transitions into a low-voltage state.
If the battery is in a low-voltage state, the charging circuit is used to power the low-voltage subsystem from the target voltage of the battery and the high-voltage subsystem from the underpowered power source (operation 512). For example, the target voltage may be up-converted (e.g., boosted) by the charging circuit to power the high-voltage subsystems. Moreover, if the voltage of the low-voltage subsystem is below the open-circuit voltage of the battery, the charging circuit may be used to power the high-voltage subsystem from a sum of currents from the input voltage from the underpowered power source and the up-converted battery voltage.
If the battery is in a high-voltage state, the charging circuit is used to power both subsystems from a target voltage of the battery that is higher than the voltage requirement of the high-voltage subsystem (operation 514). For example, the charging circuit may produce the same target voltage to charge the battery and power both subsystems. In addition, if the voltage of the low-voltage subsystem is below the open-circuit voltage of the battery, the charging circuit may be used to power the high-voltage subsystem from a sum of currents from the input voltage from the underpowered power source and the up-converted battery voltage.
If the battery is in a fully charged state, charging of the battery is discontinued (operation 516), and both subsystems are powered from a target voltage that is higher than the battery voltage of the battery in the fully charged state (operation 518). As with charging in the high-voltage state, if the voltage of the low-voltage subsystem is below the open-circuit voltage of the battery, power from the power source may be supplemented by battery power.
As with the flowcharts of
The charging circuit may be operated based on the battery state (operation 606) of the battery in the portable electronic device. If the battery is in an undervoltage state, the portable electronic device is powered off (operation 608), and detection of the power source is awaited (operation 610) because there is no useful power in the portable electronic device.
If the battery is in a low-voltage state, the charging circuit is used to directly power the low-voltage subsystem from the battery voltage and up-convert the battery voltage to power the high-voltage subsystem (operation 612). For example, the low-voltage subsystem may be powered from the battery voltage, which is between the cutoff voltage of the battery and the voltage requirement of the high-voltage subsystem, and the high-voltage subsystem may be powered by up-converting the battery voltage to a voltage that is higher than the voltage requirement.
Finally, if the battery is in a high-voltage state or a fully charged state, both subsystems are powered from the battery voltage (operation 614). For example, the battery voltage may be higher than the voltage requirement of the high-voltage subsystem, thus enabling direct powering of both the high-voltage subsystem and the low-voltage subsystem from the battery voltage without requiring additional up-converting of the battery voltage.
The above-described charging circuit can generally be used in any type of electronic device. For example,
Power supply 706 may include a bidirectional converter such as the converter shown in
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.
This application claims the benefit of U.S. Provisional Application No. 62/016,554, by inventors Thomas C. Greening, Qing Liu and William C. Athas, entitled “Battery Charging with Reused Inductor for Boost,” having serial number, and filing date 24 Jun. 2014 (Attorney Docket No. APL-P22424USP1), which is incorporated herein by reference. The subject matter of this application is related to the subject matter in a co-pending non-provisional application by inventors Jamie Langlinais, Mark Yoshimoto and Lin Chen and filed on the same day as the instant application, entitled “Multi-Phase Battery Charging with Boost Bypass,” having serial number TO BE ASSIGNED, and filing date TO BE ASSIGNED (Attorney Docket No. APL-P22424US2).
Number | Date | Country | |
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62016554 | Jun 2014 | US |