PATENT DOCUMENT

Publication Number: US-8332667-B2
Application Number: US-76916110-A
Country: US
Kind Code: B2

Title: Battery disconnection for secure assembly of computer systems

Abstract:
The disclosed embodiments provide a system that configures a battery for a computer system. During operation, the system disconnects the battery by simulating a fault condition using a safety circuit of the battery. The fault condition may be simulated to facilitate safe assembly of a computer system containing the battery. After assembly is complete, the system enables use of the battery in the computer system by applying external power to the computer system, which resets the safety circuit and reconnects the battery.

Claims:
1. A method for configuring a battery for a computer system, comprising:
 disconnecting the battery by simulating a fault condition using a safety circuit of the battery; 
 inserting the battery into the computer system; and 
 enabling use of the battery in the computer system by applying external power to the computer system, wherein the external power resets the safety circuit and reconnects the battery. 
 
     
     
       2. The method of  claim 1 , wherein simulating the fault condition in the safety circuit involves:
 sending a command to a gas-gauge circuit of the battery, wherein the gas-gauge circuit generates an output signal corresponding to the fault condition in response to the command. 
 
     
     
       3. The method of  claim 2 , wherein the command is sent to the gas-gauge circuit using a serial interface with the gas-gauge circuit. 
     
     
       4. The method of  claim 2 , wherein disconnecting the battery involves:
 disconnecting one or more field-effect transistors (FETs) in the safety circuit using the output signal, 
 wherein the disconnected FETs cause a voltage monitor coupled to the FETs to disconnect the battery by opening a set of switches. 
 
     
     
       5. The method of  claim 4 , wherein the external power resets the safety circuit by reconnecting the FETs and closing the switches. 
     
     
       6. The method of  claim 1 , wherein the fault condition corresponds to an undervoltage or an overvoltage. 
     
     
       7. The method of  claim 1 , wherein the battery is disconnected to facilitate safe assembly of the computer system. 
     
     
       8. A method for configuring a computer system, comprising:
 disconnecting a battery for the computer system by simulating a fault condition using a safety circuit of the battery; 
 inserting the battery into an enclosure for the computer system; and 
 inserting a set of components into the enclosure while the battery is disconnected to facilitate safe assembly of the computer system, 
 wherein use of the battery is enabled after assembly of the computer system is complete by applying external power to the computer system. 
 
     
     
       9. The method of  claim 8 , wherein simulating the fault condition in the safety circuit involves:
 sending a command to a gas-gauge circuit of the battery, wherein the gas-gauge circuit generates an output signal corresponding to the fault condition in response to the command. 
 
     
     
       10. The method of  claim 9 , wherein the command is sent to the gas-gauge circuit using a serial interface with the gas-gauge circuit. 
     
     
       11. The method of  claim 9 , wherein disconnecting the battery involves:
 disconnecting one or more field-effect transistors (FETs) in the safety circuit using the output signal, 
 wherein the disconnected FETs cause a voltage monitor coupled to the FETs to disconnect the battery by opening a set of switches. 
 
     
     
       12. The method of  claim 8 , wherein the fault condition corresponds to an undervoltage or an overvoltage. 
     
     
       13. The method of  claim 8 , wherein the external power resets the safety circuit and reconnects the battery. 
     
     
       14. A system for configuring a battery, comprising:
 a safety circuit configured to disconnect the battery upon detecting a fault condition; and 
 a gas-gauge circuit configured to facilitate safe assembly of a computer system containing the battery by simulating the fault condition in the safety circuit, 
 wherein use of the battery is enabled after assembly is complete by applying external power to the computer system. 
 
     
     
       15. The system of  claim 14 , wherein simulating the fault condition in the safety circuit involves:
 sending a command to the gas-gauge circuit, wherein the gas-gauge circuit generates an output signal corresponding to the fault condition in response to the command. 
 
     
     
       16. The system of  claim 15 , wherein the command is sent to the gas-gauge circuit using a serial interface with the gas-gauge circuit. 
     
     
       17. The system of  claim 15 , wherein disconnecting the battery involves:
 disconnecting one or more field-effect transistors (FETs) in the safety circuit using the output signal, 
 wherein the disconnected FETs cause a voltage monitor coupled to the FETs to disconnect the battery by opening a set of switches. 
 
     
     
       18. The system of  claim 14 , wherein the external power resets the safety circuit and reconnects the battery. 
     
     
       19. A computer system, comprising:
 a set of components powered by a battery; 
 a safety circuit configured to disconnect the battery upon detecting a fault condition; and 
 a gas-gauge circuit configured to facilitate safe insertion of the components into the computer system by simulating the fault condition in the safety circuit, 
 wherein use of the battery is enabled after assembly of the computer system is complete by applying external power to the computer system. 
 
     
     
       20. The computer system of  claim 19 , wherein simulating the fault condition in the safety circuit involves:
 sending a command to the gas-gauge circuit, wherein the gas-gauge circuit generates an output signal corresponding to the fault condition in response to the command. 
 
     
     
       21. The computer system of  claim 20 , wherein the command is sent to the gas-gauge circuit using a serial interface with the gas-gauge circuit. 
     
     
       22. The computer system of  claim 20 , wherein disconnecting the battery involves:
 disconnecting one or more field-effect transistors (FETs) in the safety circuit using the output signal, 
 wherein the disconnected FETs cause a voltage monitor coupled to the FETs to disconnect the battery by opening a set of switches. 
 
     
     
       23. The computer system of  claim 19 , wherein the external power resets the safety circuit and reconnects the battery.

Description:
RELATED APPLICATION 
     This application hereby claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 61/292,732 filed 6 Jan. 2010, entitled “Battery Disconnection for Secure Assembly of Computer Systems,” by inventors Paul Thompson, Mark Yoshimoto, Alex Crumlin, Val Valentine and Aaron Barber. 
    
    
     BACKGROUND 
     1. Field 
     The present embodiments relate to batteries for computer systems. More specifically, the present embodiments relate to a technique for disconnecting batteries for secure assembly of computer systems. 
     2. Related Art 
     Rechargeable batteries are presently used to provide power to a wide variety of portable electronic devices, including laptop computers, cell phones, PDAs, digital music players and cordless power tools. Because rechargeable battery cells typically contain volatile chemicals and electrodes which are prone to shorting, the battery cells are typically enclosed in a protective case to form a battery pack, which is then incorporated into the portable electronic device. 
     Using this type of battery pack normally leads to “double packaging” because the enclosure for the portable electronic device also provides physical protection for the battery cells. Hence, a significant amount of space and weight can be saved by eliminating the protective case surrounding the battery cells, and relying on the enclosure of the electronic device to protect the battery cells from mechanical damage. 
     However, this changes the assembly process, because instead of incorporating a protected battery pack into the system at the end of the assembly process, it makes more sense to place the unprotected and relatively fragile battery pack into the system enclosure first, before assembling the motherboard and other components on top of and around the battery cells. 
     In this case, it is undesirable for the battery pack to be providing power to the system as the motherboard and other components are being assembled, because doing so can potentially cause short circuits which could damage system components. Hence, a mechanism is needed for disconnecting the battery pack from the rest of the system until the system assembly is completed. 
     SUMMARY 
     Some embodiments provide a system that configures a battery for a computer system. During operation, the system disconnects the battery by simulating a fault condition using the safety circuit of the battery. The fault condition may be simulated to facilitate safe assembly of a computer system containing the battery. After assembly is complete, the system enables use of the battery in the computer system by applying external power to the computer system, which resets the safety circuit and reconnects the battery. Note that this system facilitates long-term storage of a portable computing device, for example prior to sale. In this case, the battery is reconnected automatically when the user connects the portable computing device to a charger for the first time. 
     In some embodiments, simulating the fault condition in the safety circuit involves sending a command to a gas-gauge circuit of the battery. In response to the command, the gas-gauge circuit generates an output signal corresponding to the fault condition. 
     In some embodiments, the command is sent to the gas-gauge circuit using a serial interface with the gas-gauge circuit. 
     In some embodiments, disconnecting the battery involves disconnecting one or more field-effect transistors (FETs) in the safety circuit using the output signal. This causes a voltage monitor coupled to the FETs to disconnect the battery by opening a set of switches. 
     In some embodiments, the external power resets the safety circuit by reconnecting the FETs and closing the switches. 
     In some embodiments, the fault condition corresponds to an undervoltage or an overvoltage. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows an example of placement of a battery in a computer system in accordance with an embodiment. 
         FIG. 2  shows an example of a system for configuring a battery in accordance with an embodiment. 
         FIG. 3  shows an example of circuitry for disconnecting and reconnecting a battery in accordance with an embodiment. 
         FIG. 4  shows a flowchart illustrating an example of a process for assembling a computer system in accordance with an embodiment. 
         FIG. 5  shows a flowchart illustrating an example of a process for configuring a battery in accordance with an embodiment. 
     
    
    
     In the figures, like reference numerals refer to the same figure elements. 
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing code and/or data now known or later developed. 
     The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium. 
     Furthermore, methods and processes described herein can be included in hardware modules or apparatus. These modules or apparatus may include, but are not limited to, an application-specific integrated circuit (ASIC) chip, a field-programmable gate array (FPGA), a dedicated or shared processor that executes a particular software module or a piece of code at a particular time, and/or other programmable-logic devices now known or later developed. When the hardware modules or apparatus are activated, they perform the methods and processes included within them. 
       FIG. 1  shows the placement of a battery  100  in a computer system  102  in accordance with an embodiment. Computer system  102  may correspond to a laptop computer, personal digital assistant (PDA), portable media player, mobile phone, digital camera, and/or other portable electronic device. Battery  100  may correspond to a lithium-polymer battery and/or other type of power source for computer system  102 . For example, battery  100  may correspond to a lithium-polymer battery that includes one or more cells packaged in flexible pouches. The cells may then be connected in series and/or in parallel and used to power computer system  102 . 
     In one or more embodiments, battery  100  is designed to accommodate the space constraints of computer system  102 . For example, battery  100  may include cells of different sizes and thicknesses that are placed side-by-side, top-to-bottom, and/or stacked within computer system  102  to fill up the free space within computer system  102 . The use of space within computer system  102  may additionally be optimized by omitting a separate enclosure for battery  100 . For example, battery  100  may include non-removable pouches of lithium-polymer cells encased directly within the enclosure for computer system  102 . As a result, the cells of battery  100  may be larger than the cells of a comparable removable battery which, in turn, may provide increased battery capacity and weight savings over the removable battery. 
     On the other hand, the elimination of a separate enclosure for battery  100  may complicate the assembly of computer system  102 . First, battery  100  may be physically vulnerable until battery  100  is encased within the enclosure for computer system  102 . For example, mishandling and/or physical contact with other components may damage the pouches, terminals, and/or cells of battery  100 . To reduce the risk of physical damage to battery  100 , battery  100  may be placed into the enclosure for computer system  102  near the beginning of the assembly process. 
     In turn, the early installation of battery  100  may cause electrical damage to other components in later stages of the assembly process. In particular, the assembly of computer system  102  may proceed by stacking components on top of a fully charged battery  100 , which may cause current to flow from battery  100  to various electrical contacts within the enclosure. For example, the stacking of a motherboard on top of battery  100  may bring the terminals of battery  100  into contact with a set of spring fingers between battery  100  and the motherboard, thus producing a return path to battery  100 . As a result, subsequent installation of components in computer system  102  may involve plugging the components into a live circuit, which may cause failures and/or other errors in the components. 
     Moreover, the use of mechanical guards to safeguard against such component failures may introduce new failures and/or impair performance in computer system  102 . For example, the placing of a physical shim between battery  100  and electrical contacts during assembly may prevent the flow of current from battery  100  but may also damage battery  102  and/or other components. Similarly, the addition of electrical components to disconnect battery  100  during assembly may interfere with the electrical performance and/or design of computer system  102 . For example, battery  100  may be disconnected during assembly by modifying the circuitry on the motherboard and/or adding a physical switch to the enclosure of computer system  100 . However, the addition of electrical components along the return path to battery  100  may decrease the electrical efficiency of computer system  102 , while the use of physically exposed switches may interfere with the design goals of computer system  102 . 
     In one or more embodiments, battery  100  is disconnected during the assembly of computer system  102  using existing safety mechanisms associated with the monitoring of battery  100 . More specifically, a resettable fault condition may be simulated using a safety circuit of battery  100  to disconnect battery  100 . After assembly is complete, the application of external power to computer system  102  may reset the safety circuit and reconnect battery  100 . As discussed in further detail below, the disconnection and reconnection of battery  100  using the safety circuit may facilitate the safe assembly of computer system  102  with little to no power loss, and may also ensure the normal use of battery  100  in powering computer system  102  after assembly is complete. 
       FIG. 2  shows a system for configuring battery  100  in accordance with an embodiment. In particular,  FIG. 2  shows a system for disconnecting and reconnecting battery  100  to facilitate safe assembly of a computer system (e.g., computer system  102  of  FIG. 1 ) containing battery  100 . As shown in  FIG. 2 , the system includes a safety circuit  202 , a gas-gauge circuit  204 , and a set of switches  206 - 208 , and could contain a serial interface  210 . Each of these components is described below in further detail. 
     Gas-gauge circuit  204  may include functionality to monitor a number of attributes associated with battery  100 . For example, gas-gauge circuit  204  may obtain current, voltage, and/or temperature measurements from one or more sensors in battery  100 . Gas-gauge circuit  204  may then use the measurements to determine the state-of-charge, impedance, capacity, charging voltage, and/or remaining charge of battery  100 . 
     In one or more embodiments, battery  100  is disconnected by sending a command to gas-gauge circuit  204  using serial interface  210 . In response to the command, gas-gauge circuit  204  may generate an output signal corresponding to a fault condition in battery  100 . For example, the output signal may represent an overvoltage or undervoltage in battery  100 . Upon detecting the simulated fault condition, safety circuit  202  may disconnect battery  100  from a load by opening switches  206 - 208 . 
     As mentioned previously, battery  100  may be disconnected to facilitate the safe assembly of the computer system. In particular, battery  100  may be embedded in the enclosure of the computer system and lack a separate enclosure. For example, battery  100  may correspond to a non-removable lithium-polymer battery that provides increased capacity, weight savings, and space savings to the computer system over a comparable battery with a separate battery enclosure. Because battery  100  is non-removable, battery  100  may be placed into the computer system&#39;s enclosure before the motherboard, hard disk drive (HDD), memory, optical drive, and/or other components in the computer system are installed. 
     To prevent issues associated with the installation of components while the computer is in a powered state, battery  100  may be disconnected during the assembly of the computer system. After assembly is complete, the application of external power to the computer system may reconnect battery  100  and enable the use of battery  100  in powering the computer system. Reconnection of battery  100  by applying external power is discussed in further detail below with respect to  FIGS. 3 and 5 . 
     In other words, events associated with normal monitoring and use of battery  100  may be used to disconnect and reconnect battery  100 . In particular, battery  100  may be disconnected by leveraging existing safety mechanisms provided by safety circuit  202  (see  FIG. 2 ), while an event associated with initial use of the computer system (e.g., plugging the computer into a power outlet) may reconnect battery  100  for use in the computer system. The system of  FIG. 2  may thus prevent issues associated with the live assembly of the computer system with little to no power loss and/or overhead to the end user of the computer system. 
       FIG. 3  shows circuitry for disconnecting and reconnecting a battery (e.g., battery  100  of  FIG. 1 ) in accordance with an embodiment. More specifically,  FIG. 3  shows the structure of a safety circuit (e.g., safety circuit  202  of  FIG. 2 ) for the battery. As shown in  FIG. 3 , four lines  302 ,  304 ,  306  and  308  connect the safety circuit to other electrical components. Line  302  may connect to the positive terminal of the battery, line  304  may connect to the negative terminal of the battery, line  306  may connect to the positive terminal of a load (e.g., computer system) powered by the battery, and line  308  may correspond to the negative terminal of the load. 
     Turning on FET  312  for some period of time (for example, for two seconds) creates a voltage divider with path  311  V DD  to simulate an undervoltage condition, as detected by a voltage monitor  310  in the safety circuit. Because the simulated undervoltage represents a fault condition in the battery, voltage monitor  310  responds to the simulated undervoltage by opening switches  314  and  316  and disconnecting the battery along the path from the negative terminal of the battery to the negative load terminal. 
     Once the battery is disconnected because of the temporary undervoltage condition, voltage monitor  310  will maintain FETs  314  and  316  in an off state indefinitely until a charging power supply is connected to the battery pack terminals. 
     To reconnect the battery, external power is applied to lines  306  and  308  causing voltage monitor  310  to turn FETs  314  and  316  on and to connect the negative terminal of the battery to the negative terminal of the load. In turn, the simulated undervoltage may be removed by keeping FET  312  off. 
     Consequently, the use of existing safety mechanisms to disconnect the battery may minimize power loss, while the presence of a latch in the safety circuit may ensure that the battery remains disconnected until the battery is ready for use (e.g., powering a computer system). Moreover, the resettable state of the safety circuit may ensure that normal use and monitoring of the battery may proceed after the battery is reconnected. 
       FIG. 4  shows a flowchart illustrating the process of assembling a computer system in accordance with an embodiment. 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. 4  should not be construed as limiting the scope of the embodiments. 
     First, a battery for the computer system is disconnected by simulating a fault condition to a safety circuit in the battery (operation  402 ). The battery may correspond to a non-removable battery and lack a separate battery enclosure. As a result, the battery may be inserted into the enclosure of the computer system (operation  404 ) before other components in the computer system. The assembly may then proceed by inserting the components into the enclosure while the battery is disconnected (operation  406 ) to facilitate safe assembly of the computer system. 
     The battery may be kept in a disconnected state after assembly is complete (operation  408 ) until external power is applied (operation  410 ). Once external power is applied, the use of the battery in the computer system is enabled (operation  412 ). For example, the battery may continue to be disconnected as the computer system is shipped to minimize self-discharge and/or damage to the battery. Moreover, the subsequent application of external power may indicate that a user is preparing to use the computer system and trigger the reconnection of the battery. The battery may thus be kept in a disconnected state to maintain the battery&#39;s integrity and charge until the battery is ready for use. 
       FIG. 5  shows a flowchart illustrating the process of configuring a battery in accordance with an embodiment. 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. 5  should not be construed as limiting the scope of the embodiments. 
     In particular, the battery&#39;s state may be configured (operation  502 ) by disconnecting the battery or reconnecting the battery. As discussed above, the battery may be disconnected to facilitate safe assembly of a computer system containing the battery. If the battery is to be disconnected, a command is sent to a gas-gauge circuit of the battery (operation  504 ). The command may be sent through a serial interface with the gas-gauge circuit. In response to the command, the gas-gauge circuit may generate an output signal corresponding to a fault condition (operation  506 ) in the battery, such as an overvoltage or an undervoltage. For example, the gas-gauge circuit may transition from a low output signal to a high output signal for two seconds in response to the command. 
     The output signal may disconnect one or more FETs (operation  508 ) in a safety circuit of the battery. The disconnected FET(s) may simulate the fault condition in a voltage monitor and cause the voltage monitor to disconnect the battery by opening a set of switches (operation  510 ). For example, the switches may disconnect the path from the negative terminal of the battery to the negative load terminal of a load connected to the battery. The FETs may additionally power off the gas-gauge circuit (operation  512 ) to complete the disconnection of the battery and the disabling of the safety circuit. 
     After assembly is complete, the battery may be reconnected to enable use of the battery in the computer system. If the battery is to be reconnected from the disconnection described in operations  504 - 512 , external power is applied to the battery (operation  514 ). The external power may reconnect the FET(s) (operation  516 ) and cause the voltage monitor to close the switches (operation  518 ), thus completing the return path to the battery. 
     The reconnected FET(s) may additionally power on the gas-gauge circuit (operation  520 ). For example, a reconnected FET may allow the external power to reach the gas-gauge circuit. The gas-gauge circuit may then complete the resetting of the safety circuit by generating an output signal for normal operation of the battery (operation  522 ). As a result, the application of external power may reconnect the battery and reset the safety circuit for subsequent use and monitoring of the battery. 
     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: 20100428
Publication Date: 20121211
Grant Date: 20121211
Priority Date: 20100106
Inventors: THOMPSON PAUL M.
YOSHIMOTO MARK A.
CRUMLIN ALEX J.
VALENTINE VAL
BARBER AARON J.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/28", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/28", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 44225411