Abstract:
A portable electronic device has at least one battery pack with each pack having its own capacity gauge. A reserve power option system monitors power level information received from the capacity gauge to determine if the portable electronic device should be transitioned into a power-saving, low-current mode.

Description:
BACKGROUND 
     The present specification generally relates to a portable electronic device, and particularly to a power system for the device. 
     A wireless phone is often placed in a standby mode when the phone is not in use. The phone receives calls or monitors status information. However, if the phone is left in the standby mode, it can continue to drain battery power until it loses virtually all of its power. This can render the battery pack, and hence the phone, unusable. 
     A battery capacity gauge determines the amount of remaining usable battery power. This is analogous to an automobile “gas gauge” . This gauge is connected to the battery pack. It can measure the current flowing in and out of the battery, the output voltage, and the temperature. The gauge can digitally integrate both charge and discharge current and voltage to calculate a state of charge of the battery pack. The data output from the gauge is displayed by a group of LEDs or uploaded to a host computer via an electronic data link. The data transmitted to the host computer may include data such as: remaining charge, total measured capacity, output voltage, real-time current, temperature, and error codes. 
     SUMMARY 
     A reserve power option system described herein recognizes that a portable electronic device can lose its battery power in a standby mode. Thereafter, the device is unusable during emergency or other situations. The current system allows the user to set a specified reserve battery power level. The user can enter different units for the power level, e.g. directly, or in terms of talk time minutes. 
     The portable electronic device has at least one battery pack, with each pack having its own capacity gauge. The reserve power option system monitors power level information received from the capacity gauge to determine if the portable device should be transitioned into a power-saving, low-current mode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects will be described in reference to the accompanying drawings wherein: 
     FIG. 1 is a block diagram of a portable electronic device; 
     FIG. 2 illustrates a battery power dissipation profile; 
     FIG. 3 is a flow diagram of a reserve power option system; 
     FIGS. 4A and 4B show a front perspective view and a rear view of a cellular telephone system using the reserve power option system; 
     FIG. 5 shows a portable communication device including the reserve power option system; and 
     FIG. 6 shows a paging device including the reserve power option system. 
    
    
     DETAILED DESCRIPTION 
     A detailed description of a reserve power option system is herein provided with respect to the figures. 
     FIG. 1 is a block diagram of a portable electronic device  100 . The portable device  100  includes device electronics  102 , at least one battery pack  108  and a switch  112 . The reserve power option system  104 , along with a device controller  106 , is included in the device electronics  102 . 
     The battery pack  108  supplies power to the portable device electronics  102  through a power switch  112  which is controlled by the device controller  106 . The device controller  106  turns the power switch  112  on or off depending on a signal  114  generated by the reserve power option system  104 . The electronics also include a cellular transceiver  120 , and a user interface  122 . 
     A processor  116  in the reserve power option system  104  monitors a battery capacity gauge  110  to determine if the battery power has reached a user-specified level. If the battery power has reached the user-specified level, the processor  116  transitions the portable device  100  from a standby mode to a low-current mode to reserve the remaining power for emergency or other use. The system  104  also generates a command to the device controller  106  to produce signal  114  to turn the power switch  112  off. 
     The user enters some value related to the particular power level, or some percentage of a total power, via user interface  122 . The portable device  100  is transitioned into the low-current mode upon reaching that level. An alternative embodiment allows the user to enter a desired reserve talk time in terms of minutes. In this embodiment, the processor  116  computes an equivalent power level to transition the device into the low-current mode. 
     An exemplary battery power dissipation profile is illustrated in FIG. 2 for three different types of batteries  200 ,  202 ,  204 . The figure shows curves of battery power dissipation versus time. The battery capacity gauge  110  indicates the power level when this power level reaches P 1  , for a battery type represented by a power dissipation profile  200 , the reserve power option system  104  provides a warning to the user. After this warning, (Δ) the power level reaches P 0  . At that time, the reserve power option system  104  transitions the portable device  100  into the low-current mode without any further warning. The portable device  100 , however, still has T 0  talk time minutes left for emergency or other use. 
     Different battery types  202 ,  204  have different power curves and hence different power levels for the same T 0  and Δ. The power curve appropriate to the installed battery is used. 
     FIG. 3 is a flow diagram of the routine that is executed by the reserve power option system  104 . The system  104  initially monitors input from the user to enter the reserve talk time minutes mode at step  300 . Once the user sets the reserve talk time minutes mode, the system  104  checks the “gas gauge” level indicated by the battery capacity gauge  110 , at step  302 . If the “gas gauge” indicates a level corresponding to a user specified talk time minutes (T 0 ) plus some delta time (step  304 ), the system  104  provides warning to the user through a video display, an audio tone, a discrete indicator, or some combination of the three. This indicates that the portable device  100  will be transitioned shortly into a low-current mode (step  306 ). 
     The reserve power option system  104  then monitors the “gas gaugel” level for T 0  at step  308 . If the level falls below T 0 , the system  104  checks to see if the user override is present, at step  310 . The user override indication is asserted when the user has decided to override the reserve power option. The entry can be made through a push-button or a keypad on the user interface  122 . If the user override indication is not present, the device  100  is placed into a low-current mode at step  312 . 
     FIG. 4A shows an exploded front perspective view of a cellular telephone system  400  using the reserve power option system  104 . The cellular telephone system  400  also includes a key pad  402  and various other buttons  404  and indicators  406 . The telephone system  400  also includes a speaker  406 , a microphone  408 , an antenna  410 , and other communication electronics  412  contained within a telephone housing  414 . A display unit  416  is used in conjunction with the keypad  402  to facilitate user inputs, such as reserve talk time minutes desired. 
     A rear view of the cellular telephone system  400  is shown in FIG.  4 B. In one embodiment, the battery pack  416  is placed within a small housing  418 . The housing  418  and the battery pack  416  is covered with a cover  420 . 
     FIG. 5 shows a portable communication device  500  including the reserve power option system  502 . The communication device  500  also includes communication electronics similar to those in the cellular telephone system  400 . 
     FIG. 6 shows a paging device  600  including the reserve power option system  602 . The paging device  600  also includes communication electronics similar to those in the cellular telephone system  400 . 
     Although only a few embodiments have been described in detail above, those of ordinary skill in the art certainly understand that modifications are possible. For example, the reserve power option system may automatically provide a preset reserve talk time for emergency or other use when the user does not input a reserve talk time. The user may override the preset talk time later. Also, a power switch, illustrated in FIG. 1, can be implemented by a firmware process using existing mechanisms in the device electronics. All such modifications are intended to be encompassed within the following claims, in which: