Abstract:
A peripheral device and a method for operating a peripheral device is disclosed. The peripheral device includes one or more connection mechanisms for coupling to a computing device, a power supply, and a controller. The controller is configured to enable the peripheral device to communicate with the computing device. When the peripheral device is coupled to the computing device, the controller is configured to determine the amount of power remaining in the power supply of the peripheral device, and based at least in part on the amount of power remaining in the power supply of the peripheral device, enable the peripheral device to charge a power supply of the computing device, and enable the peripheral device to receive power from the power supply of the computing device.

Description:
RELATED APPLICATIONS 
     This application is a Continuation of patent application Ser. No. 12/116,128, filed May 6, 2008, entitled POWER SHARING BETWEEN PORTABLE COMPUTER SYSTEM AND PERIPHERAL DEVICES, issued as U.S. Pat. No. 8,046,604 on Oct. 25, 2011, which is a Continuation of patent application Ser. No. 11/644,225, filed Dec. 22, 2006, issued as U.S. Pat. No. 7,370,219, which is a Continuation of patent application Ser. No. 10/967,997, filed Oct. 18, 2004, issued as U.S. Pat. No. 7,536,572, which is a Continuation of patent application Ser. No. 09/991,402, filed Nov. 20, 2001, issued as U.S. Pat. No. 6,820,206, all of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of computer systems. More specifically, embodiments of the present invention relate to a method and apparatus for supplying power to a portable computer system and to a peripheral device. 
     2. Related Art 
     As the components required to build a computer system have reduced in size, new categories of computer systems have emerged. One of the new categories of portable computer systems is the “palmtop” computer system. A palmtop portable computer system is a computer that is small enough to be held in the hand of a user and can be “palm-sized.” Most palmtop computer systems are used to implement various Personal Information Management (PIM) applications such as an address book, a daily organizer and electronic notepads, to name a few. 
     Because of the limited size of palmtop portable computer systems, battery power is typically limited to one or two AAA or smaller batteries. This limits the operations that can be performed by the palmtop portable computer system. 
     The latest generations of palmtop portable computer systems are enhanced with the capability of coupling to a variety of peripheral devices. This gives their user access to a large amount of additional features. However, peripheral devices often use quite a lot of power. Therefore, many peripheral devices often include their own power source such as, for example, rechargeable batteries. 
     The use of a portable computer system and a peripheral device that is connected to the portable computer system can be limited by either the batteries in the peripheral device running out of charge or the batteries in the portable computer system running out of charge. In many instances the batteries in the peripheral device run out before the batteries in the portable computer system. The user must then discontinue usage of the peripheral device, even when there is significant charge left in the batteries of the portable computer system. Also, the batteries in the portable computer system can run out before the batteries in the peripheral device. The user must then discontinue usage of the portable computer system, even when there is significant charge left in the batteries of the peripheral device. 
     What is needed is a method and apparatus for controlling operating time of a portable computer system and a peripheral device. Also, a method and apparatus is needed that maximizes operating time of the portable computer system and the peripheral device. 
     SUMMARY OF THE INVENTION 
     The method and apparatus of the present invention allows for controlling operating time of a portable computer system and a peripheral device. Also, the method and apparatus of the present invention allows for maximization of operating time of the portable computer system and the peripheral device. 
     A portable computing system is disclosed that includes a rechargeable power supply. The portable computing system also includes a connection mechanism for coupling to a peripheral device having a rechargeable power supply. The portable computing system also includes a charging control module coupled to the rechargeable power supply and coupled to the connection mechanism that includes logic for determining the operating time for the portable computer system and for the peripheral device. The charging control module is operable for charging either the rechargeable power supply of the peripheral device or the rechargeable power supply of said portable computer system so as to control the operating time for the portable computer system and the peripheral device. 
     A peripheral device is disclosed that includes a rechargeable power supply. The portable computing system also includes a connection mechanism for coupling to the connection mechanism of the portable computer system. A boost circuit that is coupled to the rechargeable power supply and that is coupled to the connection mechanism, increases the voltage from the rechargeable power supply of the peripheral device to a voltage sufficient to charge the rechargeable power supply of the portable computer system. A boost charging circuit that is also coupled to the rechargeable power supply and coupled to the connection mechanism increases voltage received from the portable computer system to a voltage sufficient to charge the rechargeable power supply of the peripheral device. In the present embodiment the peripheral device also includes a controller that is operable upon receiving instructions from the portable computer system to cause the boost circuit to send power to the portable computer system. 
     A method for controlling the operating time of a portable computer system and a peripheral device that is coupled to the portable computer system is disclosed. Charge within the rechargeable power supply of the portable computer system and charge within the rechargeable power supply of the peripheral device is determined. The determined charge for the portable computing system and for the peripheral device is then used to determine operating time for the portable computing device and operating time for the peripheral device. Operating time is an indication of the amount of time that the device will continue to operate given its remaining battery charge. 
     In one embodiment, a pop-up menu is displayed on the display screen of the personal computing system that allows the user to select a desired option (e.g., maximizing operating time of the portable computer, maximizing operating time of the peripheral device, or maximizing the life of the entire system). In the present embodiment, this pop-up menu is displayed when power is determined to be low in either the portable computing system or in the peripheral device. 
     When operating time of the portable computer system is to be maximized, power is sent from the peripheral device to the portable computer system to extend the operating time of the portable computer System. Similarly, when operating time of the peripheral device is to be maximized, power is sent from the rechargeable power supply of the portable computer system to the peripheral device to extend the operating time of the peripheral device. 
     When operating time of the entire system is to be maximized, power is moved such that the operating time for the portable computer system is equal to the operating time of the peripheral device. Thereby the operating time for the portable computing system and the peripheral device together are maximized. 
     Accordingly, the method and apparatus of the present invention allows for controlling operating time of a portable computer system and a peripheral device. Also, the method and apparatus of the present invention allows for maximization of operating time of the portable computer system and the peripheral device. Moreover, a user can maximize operating time of one component, either the operating time of the portable computer system or the peripheral device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a system illustration of a portable computing system connected to other computer systems and the Internet via a cradle device. 
         FIG. 2A  is a perspective illustration of the top face of an exemplary portable computer system. 
         FIG. 2B  is a perspective illustration of one embodiment of a bottom side of the portable computer system of  FIG. 2A . 
         FIG. 3  is a block diagram of exemplary circuitry of a portable computing system in accordance with one embodiment of the present invention. 
         FIG. 4  is a perspective view of the cradle device for connecting the portable computing system to other systems via a communication interface. 
         FIG. 5  is a perspective view of a system that includes a portable computer system and a peripheral device in accordance with one embodiment of the present invention. 
         FIG. 6  is a block diagram of exemplary circuitry of a system that includes a portable computer system and a peripheral device in accordance with one embodiment of the present invention. 
         FIG. 7  is a block diagram of exemplary circuitry of a system that includes a portable computer system and a peripheral device that includes a power-adapter charging circuit for charging the peripheral device using an external power source that does not couple to the serial connector of the peripheral device in accordance with one embodiment of the present invention. 
         FIG. 8  is a flow chart that illustrates a method for controlling the operating time of a portable computer system and a peripheral device in accordance with one embodiment of the present invention. 
     
    
    
     The drawings referred to in this description should not be understood as being drawn to scale except if specifically noted. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     Although the method and apparatus for power sharing between a portable computing device and a peripheral device of the present invention may be implemented with a variety of different electronic systems such as a pager, a mobile phone, a calculator, a personal digital assistant (PDA), etc., one exemplary embodiment includes the use of a portable computing system and a peripheral device. It should be understood that the descriptions corresponding to  FIGS. 1-4  provide some general information about an exemplary portable computing system. 
       FIG. 1  illustrates a system  50  that may be used in conjunction with an exemplary portable computing device  100 . Specifically, system  50  comprises a host computer system  66  which can either be a desktop unit as shown, or, alternatively, can be a laptop system  58 . Optionally, one or more host computer systems can be used within system  50 . Host computer systems  56  and  58  are shown connected to a communication bus  54 , which in one embodiment can be a serial communication bus, but could be of any of a number of well known communication standards and protocols, e.g., a parallel bus, Ethernet, Local Area Network (LAN), and the Optionally, bus  54  can provide communication with the Internet  52  using a number of well known protocols. 
     Bus  54  is also coupled to a cradle  60  for receiving and initiating communication with portable computing device  100 . Cradle  60  provides an electrical and mechanical communication interface between bus  54  (and anything coupled to bus  54 ) and the portable computer system  100  for two-way communications. Computer system  100  also contains a wireless infrared communication mechanism  64  for sending and receiving information from other devices. 
       FIG. 2A  is a perspective illustration of the top face  100   a  of an exemplary portable computer system  100  which is a handheld or “palmtop” computer system that is small enough to fit into a user&#39;s hand. The top face  100   a  contains a display screen  105  surrounded by a top cover  110 . A removable stylus  80  is also shown. The display screen  105  is a touch screen able to register contact between the screen and the tip of the stylus  80 . Additionally, the stylus  80  can be fabricated of any material to make contact with the screen  105 . The top face  100   a  also contains one or more dedicated and/or programmable buttons  75  for selecting information and causing the computer system  100  to implement functions. The on/off button  95  is also shown. 
       FIG. 2A  also illustrates a handwriting recognition pad or “digitizer” containing two regions  106   a  and  106   b . For example, region  106   a  is for the drawing of alpha characters therein for automatic recognition while region  106   b  is for the drawing of numeric characters therein for automatic recognition. The stylus  80  is used for stroking a character within one of the regions  106   a  and  106   b . The stroke information is then fed to an internal processor for automatic character recognition. Once characters are recognized, they are typically displayed on the screen  105  for verification and/or modification. 
       FIG. 2B  is a perspective illustration of one embodiment of a bottom side  100   b  of portable computer system  100 . An optional extendible antenna  85  is shown and also a battery storage compartment door  90  is shown. A communication interface  108  is also shown. In one embodiment of the present invention, the communication interface  108  is a serial communication port, but could also alternatively be of any of a number of well known communication standards and protocols, e.g., parallel, small computer system interface (SCSI), Ethernet, FireWire (IEEE 1394), Universal Serial Bus (USB), etc. 
       FIG. 3  is a block diagram of exemplary circuitry of portable computing system  100  in accordance with one embodiment of the present invention. The portable computer system  100  includes an address/data bus  99  for communicating information, and a central processor  101  coupled with the bus  99  for processing information and instructions. It is appreciated that central processor unit  101  may be a microprocessor or any other type of processor. The computer system  100  also includes data storage features such as a volatile memory  102  (e.g., random access memory, static RAM, dynamic RAM, etc.) coupled with the bus  99  for storing information and instructions for the central processor  101  and a non-volatile memory  103  (e.g., read only memory, programmable ROM, flash memory, EPROM, EEPROM, etc.) coupled with the bus  99  for storing static information and instructions for the processor  101 . Computer system  100  may also include an optional data storage device  104  (e.g., thin profile removable memory) coupled with the bus  99  for storing information and instructions. It should be understood that device  104  may be removable. Furthermore, device  104  may also be a secure digital (SD) card reader or equivalent removable memory reader. 
     Also included in portable computer system  100  of  FIG. 3  is an alphanumeric input device  106  which in one implementation is a handwriting recognition pad (“digitizer”) and may include integrated push buttons in one embodiment. Device  106  can communicate information (spatial data and pressure data) and command selections to the central processor  101 . The digitizer  106  records both the (x, y) coordinate value of the current location of the stylus  80  and also simultaneously records the pressure that the stylus  80  exerts on the face of the digitizer pad  106 . The coordinate values (spatial information) and pressure data are then output on separate channels for sampling by the processor  101 . In one implementation, there are roughly 256 different discrete levels of pressure that can be detected by the digitizer  106 . Since the digitizer&#39;s channels are sampled serially by the processor  101 , the stroke spatial data are sampled “pseudo” simultaneously with the associated pressure data. The sampled data is then stored in a memory by the processor  101  for later analysis. 
     System  100  of  FIG. 3  also includes an optional cursor control or directing device  107  coupled to the bus  99  for communicating user input information and command selections to the central processor  101 . In one implementation, device  107  is a touch screen device (also a digitizer) incorporated with display screen  105 . Device  107  is capable of registering a position on the screen  105  where the stylus  80  makes contact. The digitizer of  106  or  107  may be implemented using well known devices, for instance, using the ADS-7846 device by Burr-Brown that provides separate channels for spatial stroke information and pressure information. 
     Computer system  100  also contains a display device  105  coupled to the bus  99  for displaying information to the computer user. The display device  105  utilized with the computer system  100  may be a liquid crystal device (LCD), cathode ray tube (CRT), field emission device (FED, also called flat panel CRT), plasma or other display technology suitable for creating graphic images and/or alphanumeric characters recognizable to the user. In one embodiment, the display device  105  is a flat panel multi-mode display capable of both monochrome and color display modes. 
     Also included in computer system  100  of  FIG. 3  is a signal communication interface device  108  coupled to bus  99  that may be a serial port (or USB port) for enabling system  100  to communicate with the cradle  60  and with other devices and systems. As mentioned above, in one embodiment, the communication interface  108  is a serial communication port, but could also alternatively be of any of a number of well known communication standards and protocols, e.g., parallel, SCSI, Ethernet, FireWire (IEEE 1394), USB, etc. In addition to device  108 , wireless communication links can be established between the device  100  and a host computer system (or another portable computer system) using a Bluetooth wireless device  112 , an infrared (IR) device  64 , or a Global System for Messaging (GSM) radio device  114 . System  100  may also include a wireless modem device  114  and/or a wireless radio, e.g., a GSM wireless radio with supporting chip set. The wireless modem device  114  is coupled to communicate with the central processor  101  but may not be directly coupled to port  108 . 
     In one implementation, the Mobitex wireless communication system may be used to provide two way communications between computer system  100  and other networked computers and/or the Internet (e.g., via a proxy server). In other embodiments, transmission control protocol (TCP) can be used or Short Message Service (SMS) can be used. System  100  of  FIG. 3  may also contain batteries (not shown) for providing electrical power. 
       FIG. 4  is a perspective illustration of one embodiment of a cradle  60  for receiving portable computer system  100 . The cradle  60  contains a mechanical and electrical interface  260  for interfacing with communication interface  108  (as shown in  FIG. 2B ) of computer system  100  when computer system  100  is slid into the cradle  60  in an upright position. Once inserted, button  270  can be pressed to initiate two-way communication between portable computer system  100  and other computer systems (e.g.,  56  and  58 ) coupled to communication bus  54 . 
     Referring now to  FIG. 5 , a system  500  is shown that includes portable computer system  100  to which peripheral device  560  is attached. Peripheral device  560  can be any type of peripheral device that provides additional functionality to portable computer system  100 . For example, peripheral device  560  can include a position determination system (e.g., a Global Positioning System (GPS) device), a remote battery pack, a cellular telephone, a pager, a radio, etc. 
     Continuing with  FIG. 5 . In the present embodiment a serial connector on portable computer system  100  (e.g., serial connector  108  shown in  FIG. 2B ) and a corresponding serial connector receptacle located on peripheral device  660  (not shown) are used to electrically couple portable computer system  100  to peripheral device  560 . 
     In one embodiment, peripheral device  560  includes a connector receptacle  541  that receives a corresponding connector for charging peripheral device  560 . In one embodiment, connector receptacle  541  is a barrel-style connector receptacle that receives a barrel connector for charging peripheral device  560 . The charging device that is used to charge peripheral device  560  (not shown) can be a car adapter, a plug-in charger that plugs into a conventional wall outlet, etc. 
     It is appreciated that peripheral device  560  is removable and that peripheral device  560  can be easily attached and detached from portable computer system  100 . When peripheral device  560  is disconnected from portable computer system  100 , peripheral device  560  could also be charged by use of a charger that couples to the serial connector receptacle of peripheral device  560 . 
       FIG. 6  shows a diagram that illustrates some of the circuitry of system  500 . Portable computer system  100  includes power-in point  581  that receives power for charging rechargeable power supply  554  using charging circuit  520 . In one embodiment, power-in point  581  is a dedicated pin of a serial connector. However, other connection mechanisms could also be used. In the present embodiment, charging circuit  520  includes circuitry for charging rechargeable power supply  554 . 
     In the present embodiment, rechargeable power supply  554  is a rechargeable lithium-ion battery. However, any of a number of other types of rechargeable power sources could be used such as, for example, other types of rechargeable batteries. In the present embodiment, rechargeable power supply  554  operates at 3.5 Volts (from 3.1 Volts to 3.7 Volts) and charging circuit  520  is operable upon receiving power having 5 or more Volts to recharge rechargeable power supply  554 . 
     Portable computer system  100  includes power supply circuit  522  that is electrically coupled to rechargeable power supply  554  and to power-out point  582 . Power supply circuit  522  includes circuitry for controlling the flow of power to power-out point  582  in response to input from charging control module  523 . Power-out point  582  outputs power for charging peripheral device  560 . In one embodiment, power-out point  582  is a dedicated pin of a serial connector. However, other connection mechanisms could also be used. 
     Continuing with  FIG. 6 , charging control module  523  is electrically coupled to both charging circuit  520  and power supply circuit  522 . Charging control module  523  controls charging functions. In the present embodiment charging control module  523  is implemented as programming that is stored in non-volatile memory  103  (e.g., a program within the palm operating system). However, the functions of charging control module  523  could also be implemented in hardware. 
     Peripheral device  560  of  FIG. 6  includes power-in point  586  that receives power for charging rechargeable power supply  564  using boost charging circuit  562 . In one embodiment, power-in point  586  is a dedicated receptacle of a serial connector receptacle that electrically couples to pin  582  of portable computing device  100 . However, other connection mechanisms could also be used. 
     In the present embodiment, rechargeable power supply  564  is a rechargeable lithium-ion battery. However, any of a number of other types of rechargeable power sources could be used such as, for example, other types of rechargeable batteries. 
     Continuing with  FIG. 6 , boost charging circuit  562  includes circuitry for boosting voltage and charging rechargeable power supply  564 . In the present embodiment, rechargeable power supply  564  operates at 3.5 Volts and boost charging circuit  562  is operable upon receiving power having a Voltage of less than 5 Volts (e.g., 3.5 Volts received from portable computing device  100 ) to increase the Voltage to 5 or more Volts for recharging rechargeable power supply  564 . 
     Boost circuit  561  is electrically coupled to rechargeable power supply  564  and to power-out point  584 . In one embodiment, boost circuit  561  includes charging circuitry for boosting voltage in response to input received from controller  563 . In the present embodiment, boost circuit  561  increases the voltage from rechargeable power supply  564  to a voltage sufficient to charge rechargeable power supply  554  of portable computing device  100 . In the present embodiment, rechargeable power supply  564  operates at 3.5 Volts and boost circuit  561  increases the Voltage to 5 or more Volts. 
     Power-out point  584  outputs power for charging portable computer system  100 . In one embodiment, power-out point  584  is a dedicated receptacle of a serial connector receptacle that electrically couples to pin  581  of portable computer system  100 . However, other connection mechanisms could also be used. 
     Continuing with  FIG. 6 , controller  563  is electrically coupled to boost circuit  561  and boost charger circuit  562 . Controller  563  controls the operations of peripheral device  560  including charging functions. In the present embodiment controller  563  is an Application Specific Integrated Circuit (ASIC) device. However, alternatively, controller  563  can be implemented in other types of hardware or software. 
     Controller  563  is electrically coupled with charging control module  523  for receiving instructions and communicating information to charging control module  523 . In the present embodiment, communication between controller  563  and charging control module  523  is via a serial connection mechanism. In one embodiment, the serial connection mechanism includes one or more pin  583  that mates with one or more corresponding pin receptacle  585  on peripheral device  560 . 
     In the present embodiment, charging control module  523  includes logic for determining the operating time for portable computer system  100  and for determining the operating time for peripheral device  560 . Charging control module  523  is operable for charging either rechargeable power supply  564  of peripheral device  560  or charging rechargeable power supply  554  of portable computer system  100  so as to control the operating time for portable computer system  100  and peripheral device  560 . 
       FIG. 7  shows an embodiment in which peripheral device  560   a  includes a separate power-adapter charging circuit  570  that does not require connection to the serial connection receptacle (that mates with portable computing system  100 ) for charging rechargeable power supply  564  of peripheral device  560 . In the embodiment shown in  FIG. 5 , power-adapter charging circuit  570  includes connection mechanism  541  that is coupled to power-adapter  573  for providing power to peripheral device  560 . 
     Continuing with  FIG. 7 , peripheral device  560   a  includes switch  571  that couples power-out point  584  to either boost circuit  561  or to power-adapter charging circuit  570 . Similarly, switch  572  is operable to either couple boost charging circuit  562  to power-adapter charging circuit  570  or to or to power-in point  586 . 
     In the present embodiment, switches  571 - 572  are operable upon receiving input from controller  563  to either electrically couple power-adapter charging circuit  570  to rechargeable power supply  564  or to electrically couple points  584  and  586  to rechargeable power supply  564 . This allows for charging rechargeable power supply  564  using power supplied through power-adapter charging circuit  570  (e.g., an automotive charger, a plug-in wall outlet charger, etc.) or using power supplied through input/output points  584  and  586 . 
       FIG. 8  shows a method  800  for controlling the operating time of a portable computer system and a peripheral device that is coupled to the portable computer system. As shown by step  801 , the charge within a rechargeable power supply of the portable computer system is determined. In the embodiment shown in  FIGS. 6-7 , charger control module  523  is operable to determine the charge remaining in rechargeable power supply  554 . 
     The charge within the rechargeable power supply of the peripheral device is determined as shown by step  802 . In one embodiment, charging control module  523  of  FIGS. 6-7  sends instructions to controller  563 . In response, controller  563  determines the charge of rechargeable power supply  564 . Controller  563  then communicates the charge of rechargeable power supply  564  to charger control module  523 . 
     Operating time for the portable computing system is determined as shown by step  803 . In the present embodiment, the amount of charge within the rechargeable power supply of the portable computing system that was determined in step  801  is used for determining operating time for the portable computer system. In the embodiment shown in  FIGS. 6-7 , charger control module  523  is operable to determine the operating time for portable computing system  100 . In one embodiment, operating time is an indication of the amount of time that portable computer system  100  will continue to operate using an estimated power consumption level. The estimated power consumption level can be a fixed value that is stored in the personal computer system. Alternatively, the estimated power consumption level can be determined by analysis of recent power consumption by portable computer system  100 . 
     Operating time for the peripheral device is determined as shown by step  804 . In the present embodiment, the amount of charge within the rechargeable power supply of the peripheral device that was determined in step  802  is used for determining operating time for the peripheral device. In one embodiment, operating time is an indication of the amount of time that the peripheral device will continue to operate using an estimated power consumption level. The estimated power consumption level can be a fixed value that is stored in either the portable computer system or the peripheral device. Alternatively, the estimated power consumption level can be determined by analysis of recent power consumption by the peripheral device. 
     In the embodiment shown in  FIGS. 6-7 , charger control module  523  is operable to determine the operating time for peripheral device  560 . Alternatively, controller  563  is operable to determine operating time and communicate the determined operating time to portable computing device  100 . 
     In one embodiment, controller  563  is operable to both determine charge within rechargeable power supply  564  of peripheral device  560  (step  802 ) and to determine operating time for peripheral device  560  (step  804 ). In this embodiment, charging control module  523  sends instructions to controller  563  that cause controller  563  to determine charge (step  802 ) and to determine operating time (step  804 ). Controller  563  then sends a response to control module  523  that indicates the charge of peripheral device  560 . 
     Either the rechargeable power supply of the peripheral device or the rechargeable power supply of the portable computer system is charged to provide the desired operating time as shown by step  805 . In the embodiment shown in  FIGS. 6-7 , when portable computer system  100  is to be charged, charging control module  523  sends instructions to controller  563  instructing controller  563  to cause boost circuit  561  to send power to portable computer system  100 . Boost circuit  561  then boosts the voltage to a voltage level sufficient for charging rechargeable power supply  554  (e.g., a voltage of 5 or more Volts) and power is sent via power-out point  584  to power-in point  581 . The power is then coupled from power-in point  581  to charging circuit  520  that is operable to charge rechargeable power supply  554 . 
     In the embodiment shown in  FIGS. 6-7 , when peripheral device  560  is to be charged, charging control module  523  provides input to power supply circuit  522  that causes power supply circuit  522  to couple power to power-out point  582 . The received power is coupled through power-in point  586  to boost charging circuit  562 . Boost charging circuit  562  then boosts the voltage to a voltage level sufficient for charging rechargeable power supply  564  (e.g., a voltage of 5 or more Volts) and recharges rechargeable power supply  564 . 
     In one embodiment, user input is used to determine whether the operating time of the portable computer system or the operating time of the peripheral device is to be extended. In the present embodiment, a user can choose between maximizing the operating time of the portable computer, maximizing the operating time of the peripheral device, or maximizing the life of the entire system (maximizing the operating time of the portable computer system and the peripheral device). 
     In the embodiment shown in  FIGS. 2-4 , the digitizer of devices  106  or  107  is used to receive user input. In one embodiment, a pop-up menu is displayed on display screen  105  that allows the user to select a desired option (e.g., maximizing operating time of the portable computer, maximizing operating time of the peripheral device, or maximizing the operating time of the entire system). 
     In one embodiment, when the charge is determined to be low within either the rechargeable power supply of the portable computing system  100  or the rechargeable power supply of the peripheral device  560 , a pop-up menu is displayed that indicates that power is low. The user is then prompted to choose between maximizing operating time of the portable computer system, maximizing operating time of the peripheral device, or maximizing the operating time of the entire system. 
     When operating time of the portable computer system is to be maximized, power is sent from the peripheral device to the portable computer system to extend the operating time of the portable computer system. Similarly, when operating time of the peripheral device is to be maximized, power is sent from the rechargeable power supply of the portable computer system to the peripheral device to extend the operating time of the peripheral device. 
     When operating time of the entire system is to be maximized (operating time of both the portable computer system and the peripheral device are to be maximized), power is moved such that the operating time for the portable computer system is equal to the operating time of the peripheral device. In the present embodiment, the rechargeable power supply of the portable computer system is charged when the determined operating time for the peripheral device is greater than the determined operating time for the portable computer system. Similarly, the rechargeable power supply of the peripheral device is charged when the determined operating time for the portable computer system is greater than the determined operating time for the peripheral device. 
     The preferred embodiment of the present invention, a method and apparatus for controlling the operating time of a portable computer system and a peripheral device, is thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.