Abstract:
A handheld mobile communication device includes a rechargeable first battery for powering the device. A charger includes a second battery. The charger is configured to be detachably coupled to and supported by the device. The device and the charger can be carried together as a single unit as the charger charges the first battery with power from the second battery.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation of U.S. application Ser. No. 10/443,286, filed May 22, 2003, which is a continuation of U.S. application Ser. No. 10/007,848, filed Nov. 5, 2001 (now U.S. Pat. No. 6,583,601), which claims priority of U.S. Provisional Application No. 60/246,142, filed Nov. 6, 2000, all three applications hereby incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to battery chargers, especially for mobile communication devices.  
       BACKGROUND  
       [0003]     Many electronic devices, such as mobile communication devices, are powered by rechargeable batteries. Typically, rechargeable batteries include Lithium-ion (LiIon) and Nickel Cadmium (NiCad) cells. Instead of powering down the device and replacing the rechargeable battery, these electronic devices are typically plugged into a battery charger when the rechargeable battery is in a low charge state. Battery chargers typically include a cord that plugs into an electrical wall outlet and the electronic device.  
       SUMMARY  
       [0004]     A handheld mobile communication device includes a rechargeable first battery for powering the device. A charger includes a second battery. The charger is configured to be detachably coupled to and supported by the device. The device and the charger can be carried together as a single unit as the charger charges the first battery with power from the second battery.  
         [0005]     Preferably, the charger monitors the first battery&#39;s voltage and change from a first charging mode to a second charging mode when the first battery&#39;s voltage exceeds a threshold. The charger discontinues charging the first battery when the second battery&#39;s voltage drops below a threshold. The charger sends a signal to the device indicative of the first battery&#39;s voltage being low. The device notifies a user that the first battery&#39;s voltage is low voltage. The device notifies a user that the charger has ceased charging the first battery when the charger has ceased charging the first battery. The charger charges the first battery with the power from the second battery at a voltage that is different than the second battery&#39;s voltage.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a block diagram of a portable charger circuit;  
         [0007]      FIG. 2  is an orthogonal view of the front of a portable charger;  
         [0008]      FIG. 3  is an orthogonal view of the back of the portable charger;  
         [0009]      FIG. 4A  is an orthogonal view of the back of the portable charger with a battery door cover removed;  
         [0010]      FIG. 4B  is an orthogonal view similar to  FIG. 4A  with a battery installed; and  
         [0011]      FIG. 5  is an orthogonal view of the portable charger connected to a portable electronic device. 
     
    
     DESCRIPTION  
       [0012]     Referring now to the drawing figures,  FIG. 1  is a block diagram of a portable charger circuit  10 . The charger circuit  10  includes a low-voltage battery  11  and first and second battery contacts  12  and  13 , which provide power to the charger circuit  10 . A reverse battery protection module  14 , an analog switch  16 , a switching regulator  18 , and a control and monitor module  20  operate together to transform the charge in the low voltage battery  11  into a charger output  24 . A charger interface connector  22  communicates with a mobile device  23  having a rechargeable battery  25 . The battery  11  inserted between the battery contacts  12  and  13  charges the rechargeable battery  25  (such as a LiIon cell battery) in the mobile device  23  through the charger interface connector  22 .  
         [0013]     The battery contacts  12  and  13  are coupled in parallel with the reverse battery protection module  14 . In addition, one of the battery contacts  12  is also coupled to the switching regulator  18 , and the other battery contact  13  is coupled both to the switching regulator  18  and the charger interface  22  through the analog switch  16 . The analog switch  16  receives a control signal  15  from the reverse battery protection module  14  that can open the analog switch  16  in order to decouple the battery  11  from the charger circuit  10 . The switching regulator  18  generates the charger output  24 , which is fed back to the reverse battery protection module  14 , and which is also coupled to the charger interface connector  22 . The control and monitor module  20  communicates with the switching regulator  18  and the charger interface connector  22  through control signals  26  and  28 . The charger interface connector  22  preferably communicates to the mobile device  23  through a serial connection, such as a 16-pin miniature connector.  
         [0014]     Preferably, one of the battery contacts  12  is a positive terminal and the other battery contact  13  is a negative terminal. When a battery  11  is inserted between the battery contacts  12  and  13 , the reverse battery protection module  14  detects whether the battery  11  is inserted correctly by checking the polarity of the battery  11 . If the battery polarity is reversed, then the control signal  15  from the reverse battery protection module  14  opens the analog switch  16 , thereby decoupling the negative terminal  13  from the switching regulator  18  and charger interface connector  22 . The reverse battery protection module  14  thus protects the circuit  10  from reverse polarity that could occur if a battery  11  was inserted incorrectly. By maintaining the analog switch  16  in the off (open) position, the reverse battery protection module  14  prevents any charge from the battery  11  from leaking to the switching regulator  18 , or to other components in the circuit  10 .  
         [0015]     The reverse battery protection module  14  also monitors the charge line to turn the analog switch  16  on in the presence of an operational rechargeable battery.  
         [0016]     If the battery  11  is installed correctly between the contacts  12  and  13 , then the switching regulator  18  is preferably powered from a low-voltage value battery  11  and provides power to the charger output  24 , which is used to charge the rechargeable battery  25  in the mobile device  23 . The switching regulator  18  preferably operates in one of two different modes depending on the voltage of the rechargeable battery  25  in the mobile device  23 . When the rechargeable battery voltage is low, then the switching regulator  18  preferably operates in a current limiting mode. In this mode, the switching regulator  18  generates a constant current output  24  through the charger interface connector  22  to the mobile device  23 . The rechargeable battery  25  is charged from this constant current output  24  until the rechargeable battery  25  reaches a threshold voltage, which depends on the LiIon battery voltage. Once the threshold voltage is reached, then the switching regulator  18  preferably switches to a constant voltage mode. In the constant voltage mode, the switching regulator  18  preferably generates a constant voltage output  24  to charge the rechargeable battery  25 . As the rechargeable battery  25  voltage rises to its final charge value, that is, the rechargeable battery is fully charged, the feedback signal  28  from the mobile device  23  is used to regulate the output of the switching regulator  18  in order to keep the voltage constant at the rechargeable battery  25  terminals.  
         [0017]     The differing modes for charging the rechargeable battery  25  are provided in order to achieve efficient recharging. When the charger circuit  10  is in the current limiting mode, the switching regulator  18  preferably generates a full duty cycle charger output  24 . Thus, when the voltage of the rechargeable battery  25  is below the threshold level, the rechargeable battery  25  is charged on a full duty cycle. Once the threshold voltage is reached, however, the voltage of the battery  11  is no longer sufficient to charge the rechargeable battery  25 , and the switching regulator  18  switches to a constant voltage mode to increase the voltage of the charger output  24 . The control and monitor module  20  monitors the feedback signal  28  to determine the voltage of the rechargeable battery  25 . As the rechargeable battery voltage exceeds the threshold voltage, the control and monitor module  20  controls the output voltage of the charger output  24 . As the rechargeable battery voltage increases, the control and monitor module  20  increases the voltage of the charger output  24  in order to continue to charge the rechargeable battery  25 .  
         [0018]     The control and monitor module  20  monitors signals  26  and  28  from the switching regulator  18  and the mobile device to control the operation of the circuit  110  For example, the control and monitor module  20  may monitor the voltages of the charger battery  11  and the rechargeable battery  25 , and control signals from the mobile device  25 . The control and monitor module  20  monitors the charger battery  11  to determine when the voltage of the battery is below 1.0 V. When the voltage is below 1.0 V, the control and monitor module  20  sends a signal to the switching regulator  18  to shut it down in order to prevent damage to the switching regulator  18 . The control and monitor module  20  may also send a signal to the mobile device  25  to report the low voltage to a user of the device so that the user can replace the charger battery  11 . As described above, the control and monitor module  20  may also monitor the rechargeable battery voltage to determine when to switch modes on the switching regulator  18 , and to turn off the switching regulator  18  when the rechargeable battery  25  reaches a desired voltage level.  
         [0019]     The voltage of the rechargeable battery  25  is monitored by the control and monitor module  20  through the charger interface connector  22  as an analog feedback signal  28 . The control and monitor module  20  monitors the feedback signal  28  to determine when to send a control signal  26  to the switching regulator  18  to change modes from current limiting to constant voltage. This signal is preferably sent to the switching regulator  18  when the feedback signal  28  is around the threshold value. The control and monitor module  20  then monitors the feedback signal  28  to ramp up the charger output  24  as the rechargeable battery  25  is charged to the final desired voltage level (fully charged). The switching regulator  18  thus produces an output signal  24  at a voltage that is higher than the voltage of the rechargeable battery  25 . The charging continues until the rechargeable battery  25  is fully charged (around 4.1 V), or the charger battery voltage drops to 1.0 V. If the charger battery voltage drops to 1.0 V, then the control and monitor module  20  may send a signal to the mobile device  23 , which can notify a user that the charger battery  11  is in a low voltage state, and charging has stopped. The control and monitor module  20  thus monitors the charge in both batteries to determine how to charge the rechargeable battery  25  from the charger battery  11 .  
         [0020]     For example, when a user determines that the rechargeable battery  25  in the mobile device  23  is in a low charge state, then the user connects the charging circuit  10  to the mobile device  25 . The control and monitor module  20  detects the presence of the mobile device  25  and also detects the presence of the charger battery  11  in the charger circuit  10 . The control and monitor module  20  then directs the switching regulator  18  to begin generating the charger output  24 . Assuming the rechargeable battery  25  is in a charge state with a voltage below the final fully charged state, the control and monitor module  20  directs the switching regulator  18  to charge in current limiting mode. The control and monitor module  20  then monitors both batteries  11  and  25  for changes in their respective terminal voltages. When the rechargeable battery  25  is charged to a state where its voltage equals the final fully charged state, then the control and monitor module  20  switches the switching regulator  18  to the constant voltage mode. The control and monitor module  20  provides the voltage level of the rechargeable battery  25  to the switching regulator  18  so that the charger output  24  is regulated to keep the voltage constant at the rechargeable battery  25  terminals. The control and monitor module  20  then sends a shutdown signal to the switching regulator  18  when the voltage of the charger battery  11  is below 1.0 V, or the rechargeable battery  25  is fully charged. In an alternative embodiment, other control signals  28  from the mobile device  23  may also shut down the charging operation. For example, a temperature monitor on the mobile device  23  may generate a shutdown signal if the rechargeable battery  25  overheats during charging.  
         [0021]      FIG. 2  is an orthogonal view of the front of a portable battery charger  30 . The battery charger  30  includes a generally rectangular housing  32 . The housing includes a front wall  34 , a back wall  36  and side walls  38 . The back and side walls  36  and  38  extend past an edge  40  of the front wall  34  to form a well  42 . The well  42  receives and mates with the mobile device  70  ( FIG. 5 ). Side wall guides  44  guide the edges of the mobile device  70  into the well  30 . An edge surface guide  46  of the back wall  36  guides the back of the mobile device  70  into the well  42 . The guides  44  and  46  direct a pin connector on the mobile device  70  to mate with a connector  50  on the battery charger  30 . The connector  50  may, for example, be the charger interface connector  22  described above with reference to  FIG. 1 . In this example, the connector  50  is a male pin connector, but other connectors on the battery charger  30  could instead include a female pin connector configured to mate with a male pin connector on the mobile device.  
         [0022]     Prongs  54  engage the sides of the mobile device  23  so that the portable charger  30  is supported on the device through the prongs  54  instead of being supported through the pin connector  50 . The prongs  54  preferably snap into notches in the side of the mobile device  70  such that an interference fit is achieved between the prongs  54  and the notches that can support the weight of the portable charger  26 . The portable charger  30  can preferably be removed from the mobile device  70  by sliding the portable charger  30  away from the mobile device  70 . The prongs  54  flex away from the sides of the mobile device  70  when the charger  30  is slid away from the mobile device  70 .  
         [0023]      FIG. 3  is an orthogonal view of the back of the portable battery charger  30 . A battery cover  58  is slidably received on the back  36  of the portable charger  30 . The battery cover  58  slides into place and is retained by an interference fit between the battery cover  58  and the back  36 .  FIG. 4A  is an orthogonal view of the back of the portable charger  30  with the battery cover  58  removed. A battery compartment  60  includes battery guides  62 , a positive contact  64 , and a negative contact spring  66 . The positive contact  64  and the negative contact spring  66  may, for example, be the battery contacts  12  and  13  described above with reference to  FIG. 1 . These components  62 ,  64 , and  66  guide a battery so that the battery may be properly seated in the battery compartment  60 .  FIG. 4B  is an orthogonal view of the back of the portable charger  30  with the battery door cover  50  removed, and a battery  68  inserted in the battery compartment  60 .  
         [0024]      FIG. 5  is an orthogonal view of the portable charger  30  connected to a portable electronic device  70 . When attached to the mobile device  70 , the portable charger  30  preferably extends from the base of the mobile device  70 . A user can then carry both the portable charger  30  and the mobile device  70  so that the user may use the mobile device  70  as the portable charger  30  is charging the LiIon battery in the mobile device  70 .  
         [0025]     The embodiment described above is an example of structures or methods having elements corresponding to the elements recited in the claims. This written description may enable those skilled in the art to make and use embodiments having alternative elements that likewise correspond to the elements of the invention recited in the claims. The intended scope of the invention thus includes other structures or methods that do not differ from the literal language of the claims, and further includes other structures or methods with insubstantial differences from the literal language of the claims.