Abstract:
A versatile external battery system has a built-in charger. Using particular plugs containing capacitors, the system can connect to many makes and models of notebook computer. The capacitor configures an oscillator which controls a DC-to-DC converter. In this way, disconnecting the plug turns off the oscillator and eliminates power leakage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. application No. 60/581,003, which application is incorporated herein by reference for all purposes. 
     
    
     BACKGROUND 
       [0002]    Mobile professionals have, in recent years, seen a reduction in the number of cables that must be connected to a notebook computer whilst traveling. An external pointing device or external keyboard may be connected via Bluetooth rather than a cable. A connection to a computer network may be by means of an 802.11b wireless link rather than an Ethernet cable. A connection to the Internet may be by means of a wireless GPRS (general packet radio service) or 1× or EVDO (evolution data only) or Edge (enhanced data rates for global evolution) or UMTS (universal mobile telecommunications system) connection. 
         [0003]    Despite this progress, one cable stubbornly remains as a necessity for use of a notebook computer on the road—the power cable. As provided by the manufacturer, a notebook computer will typically have an internal rechargeable battery and an external charger for drawing upon AC (mains) power to recharge that battery. Optionally, the manufacturer may offer an external charger for drawing upon an automobile 12 volt cigarette lighter power source to recharge the notebook battery. Such a charger also typically can draw upon an Empower connector on an airplane for power to recharge the battery and to operate the computer. But in each of these cases the user is forced to connect a cable from the computer to some fixed power source. 
         [0004]    In recent years another approach has been attempted, namely an external rechargeable universal battery to provide power to a notebook computer. Following this approach, a system comprises a rechargeable battery and a switching power supply that is intended to be able to produce any of a number of particular voltages. Detachable plugs are provided to connect between the system and a particular notebook computer. The plug provides an electrical connection between the system and the computer, as well as providing a mechanical match of pin or conductor configuration to match the computer. In addition, the plug contains a programming resistor. The resistor connects with a control circuit within the system. The value of the resistor determines which of the particular voltages will be produced by the switching power supply. In this way, a particular selection of plug may provide physical and electrical compatibility with a particular make and model of notebook computer. 
         [0005]    At least some embodiments of this approach offer the potential drawback that the control circuit and switching power supply are always on. This leads to power leakage. 
         [0006]    Another potential drawback to this approach is that a resistor may not be the best choice for a way of determining the voltage to be generated. 
         [0007]    Patents that attempt to address some aspects of external power include U.S. Pat. No. 6,624,616 to Frerking et al., U.S. Pat. No. 5,530,296 to Masaki, U.S. Pat. No. 6,441,589 to Frerking et al., and U.S. Pat. No. 6,495,932 to Yoshimizu et al. 
         [0008]    It would be very desirable to have an external power supply system with a power saving mode to eliminate power leakage, 
       SUMMARY OF THE INVENTION 
       [0009]    A versatile external battery system has a built-in charger. Using particular plugs containing capacitors, the system can connect to many makes and models of notebook computer. The capacitor configures an oscillator which controls a DC-to-DC converter. In this way, disconnecting the plug turns off the oscillator and eliminates power leakage. 
     
    
     
       DESCRIPTION OF THE DRAWING 
         [0010]    The invention will be described with respect to a drawing in several figures. Where possible, like elements are designated with like reference designations. 
           [0011]      FIG. 1  shows a prior-art external power supply. 
           [0012]      FIG. 2  shows in functional block diagram form a system according to a first embodiment of the invention. 
           [0013]      FIG. 3  shows in schematic diagram form the system of  FIG. 2 . 
           [0014]      FIG. 4  shows in functional block diagram form a system according to a second embodiment of the invention. 
           [0015]      FIG. 5  shows in schematic diagram form the system of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows a prior-art external power supply  12 . Mains (AC) power is supplied at  10 . This power is rectified at  11  and the resulting DC is passed to a high-frequency switching circuit  13 . The high-frequency output of the circuit  13  is provided to a transformer  14 . The output of the transformer  14  passes to a rectifier  15  and then reaches equipment (omitted for clarity in  FIG. 1 ) by power lines  21 . 
         [0017]    The motivation for employing a high frequency circuit  13  is that it permits a much smaller transformer  14  as compared with the transformer that would be needed if fifty- or sixty-cycle AM power were supplied directly to the transformer  14 . 
         [0018]    A plug  19  is connected to the supply  12 . The plug  19  provides mechanical compatibility for the conductors  21  to match the pin or connector configuration required to mate with the equipment to be powered (omitted for clarity in  FIG. 1 ). The plug  19  also provides a programming resistor  20 . The value of the programming resistor  20  affects a control circuit  17 . The control circuit  17  controls the rectifier  15  and associated circuitry by means of control line  18 . In this way it is desired to cause the rectifier  15  and associated circuitry to produce whatever DC voltage level is required at the equipment to be powered. For each make and model of equipment to be powered, a respective plug  19  is employed to provide both electrical and mechanical compatibility. An example of such a system may be seen in the above-mentioned U.S. Pat. No. 6,495,932 to Yoshimizu et al. 
         [0019]      FIG. 2  shows in functional block diagram form a system  30  according to a first embodiment of the invention. Power is received at connector  31 , for example an input of 20 volts DC from an external AC adaptor. This power passes to charger  32  which is used to charge battery  33 . In a typical embodiment the battery  33  comprises four lithium-ion cells in series. 
         [0020]    Optionally a “gas gauge”  35  is provided. Upon the press of a button, the gas gauge is actuated and it illuminates selected LEDs in a (typical) five-LED array to indicate the extent to which the battery is full (charged) or empty (discharged). Such gas gauge circuits are well known and the particular gas gauge circuit employed is not specific to the invention. 
         [0021]    Also provided is a “protection” circuit  34 . This circuit reads the potential across each of the four lithium-ion cells. If any one cell reads a much smaller potential than expected during charging, then it is inferred that the cell has failed in a low-impedance or “shorted” state. Such a state would risk overheating if charging current were to continue to be applied, and the protection circuit  34  cuts off the charging current. 
         [0022]    Another condition to be protected against is reverse charging of a single cell at a time when the battery is being used to power equipment. When discharge current is flowing through the battery  33 , there is a possibility that one of the cells may discharge sooner than the others. When this happens there is the risk that the remaining three cells would continue to generate a current, thereby continuing to provide power at the equipment. If this were to happen, the current would reverse-charge the discharged cell, likely causing permanent damage to that cell. The protection circuit  34  cuts off current flow in such an event, to protect the discharged cell from damage. 
         [0023]    Such protection circuits are well known and the particular protection circuit employed is not specific to the invention. 
         [0024]    Optional line  36  may permit bypassing the battery  33  and charger  32  in the special case where there is power available at  31  at the same time that it is desired to power the equipment. 
         [0025]    A plug  42  is used to connect the system  30  to a particular make and model of equipment to be powered, omitted for clarity in  FIG. 2 . Typically the equipment to be powered is a notebook computer. The plug  42  has connector pins  41  which connect to the equipment to be powered. These pins are mechanically disposed to provide mechanical compatibility with the equipment to be powered. 
         [0026]    Plug  42  contains a capacitor  43 . This capacitor is connected via line  40  with an oscillator  38 . In a typical embodiment the oscillator  38  is disposed to oscillate at any of at least two predetermined frequencies as a function of the value of the capacitor. The oscillator  38  causes the switching power supply  37  to yield a particular desired output voltage to match the requirements of the external equipment to be powered. 
         [0027]    In a typical embodiment a first frequency is used to generate about sixteen volts for a notebook computer using a three-cell internal lithium-ion battery, and a second frequency is used to generate about nineteen volts for a notebook computer using a four-cell internal lithium-ion battery. The absence of oscillation puts the switching power supply into its power saving mode, thus eliminating power leakage. 
         [0028]    As will be appreciated, if the external capacitor  43 , is not connected, then the oscillator  38  does not oscillate. This puts the circuitry  37  into a power saving mode. 
         [0029]    The consequence is an elimination of power leakage while the system  30  is in this power saving mode. 
         [0030]      FIG. 3  shows in schematic diagram form the system  30  of  FIG. 2 . Charger  32  is seen in component-level detail including charging integrated circuit  57 . Gas gauge  35  comprises voltage regulator  53 , and signal line  54  which is indicative of the voltage at the battery  33 . LEDs  50 , disposed in a bar graph, are selectively illuminated in response to a user input at push button  51 . 
         [0031]    Protection circuit  34  may also be seen. This circuit includes solid-state switches  56  and integrated circuit  55  which connects with each terminal of each of the cells of the battery  33 . 
         [0032]    Switching power supply  37  may also be seen, including integrated circuit  59 . As will be seen in  FIG. 3 , capacitor  43  connects via line  40  to oscillator  38 . This oscillator  38  sends control signals to the switching power supply  37 . 
         [0033]      FIG. 4  shows in functional block diagram form a system according to a second embodiment of the invention. In this embodiment, the plug  72  contains jumper locations  74 . The presence or absence of these jumpers is communicated by lines  77  to the switching power supply  71 , thereby determining the output voltage therefrom. In this way the plug  72  provides mechanical and electrical compatibility with the equipment to be powered (omitted for clarity in  FIG. 4 ). 
         [0034]    In an exemplary embodiment the power supply  71  is disposed to go into power saving mode when plug  72  is disconnected, thereby eliminating power leakage. 
         [0035]    In exemplary embodiments of either of the systems of  FIGS. 2-3  or  FIGS. 4-5 , there are typically two possible output voltages—one output voltage of about 16 volts to serve a notebook computer containing three lithium-ion cells in its internal battery, and another output voltage of about 19 volts to serve a notebook computer containing four lithium-ion cells in its internal battery. 
         [0036]      FIG. 5  shows in schematic diagram form the system of  FIG. 4 . Switching power supply  71  contains integrated circuit  78 . Signal lines  75 ,  76  communicate the presence or absence of jumpers  74 . 
         [0037]    Those skilled in the art will have no difficulty devising-myriad obvious improvements and variants of the invention without undue experimentation, all of which are intended to be encompassed within the claims which follow.