Abstract:
A device may include a battery; a first component drawing a first current from the battery, the first current being below a threshold; and a second component drawing a second current from the battery. The second component indicates the entering of a low current mode for a predetermined time. The first component is allowed to draw a third current above the threshold for the predetermined time.

Description:
BACKGROUND  
       [0001]    The operational parameters of handheld devices are often governed by available battery power. While average current demands are often low, peak current demand may be significantly higher. Both average and peak current may factor into the selection of a battery. Because the size and weight of a device may be significantly impacted by the size and weight of its battery, maintaining peak current at or below a certain level may enable such size and weight to be minimized. 
       SUMMARY OF THE INVENTION  
       [0002]    The present invention relates to a device and a method for reducing peak current demands in a mobile device. The device may include a battery; a first component drawing a first current from the battery, the first current being below a threshold; and a second component drawing a second current from the battery. The second component indicates the entering of a low current mode for a predetermined time. The first component is allowed to draw a third current above the threshold for the predetermined time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0003]      FIG. 1  shows a schematic view of an exemplary mobile computing device according to the present invention. 
           [0004]      FIG. 2  shows a graph of current usage against time for an exemplary device according to the present invention. 
           [0005]      FIG. 3  shows an exemplary method according to the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0006]    The exemplary embodiments of the present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments of the present invention describe systems and methods for minimizing the peak current requirements of a mobile computing device that includes more than one current-drawing component. 
         [0007]      FIG. 1  shows a schematic layout of an exemplary mobile computing device  100  according to the present invention. The device  100  may include a battery  110 , a CPU  120 , an RFID radio  130  and a WLAN radio  140 . Those of skill in the art will understand that the device  100  may typically include other components (e.g., a display, a user input means, a USB interface, a speaker, etc.) that are not shown in  FIG. 1 . Further, those of skill in the art will understand that the presence of an RFID radio  130  and a WLAN radio  140  is only exemplary, and that the current requirements to be managed by the exemplary embodiments may be due to various other types of components. 
         [0008]    The battery  110  may be any type of battery capable of storing electric energy for use by the components of the device  100 , including the CPU  120 , the RFID radio  130  and the WLAN radio  140 . The battery  110  may be reusable or disposable. In one exemplary embodiment, the battery  110  is a lithium ion rechargeable battery. The CPU  120  may be any processing unit known in the art and suitable for operating a mobile computing device such as the device  100 . The RFID radio  130  may be coupled with the CPU  120  and an antenna (not shown) to enable RFID communication with other devices, and the WLAN radio  140  may similarly be coupled with the CPU  120  and a further antenna (not shown) to enable WLAN communication with other devices. Each of the RFID radio  130  and the WLAN radio  140  may coordinate communications using any of various communications protocols known in the art. 
         [0009]      FIG. 2  illustrates an exemplary graph showing the power consumption of the CPU  120 , the on-off status of the RFID radio  130  and the WLAN radio  140 , and the voltage of the battery  110  with respect to time. It should be noted that the CPU power consumption and the component on-off status are only exemplary and have been selected to illustrate the problem to be addressed by the exemplary embodiments. Those of skill in the art will understand that battery voltage as shown in  FIG. 2  may depend on factors including the internal impedance of the battery  110 , the temperature of the environment in which the device  100  is being used, and the current demands of the CPU  120 , the RFID radio  130  and the WLAN radio  140  as illustrated. 
         [0010]      FIG. 2  illustrates that when multiple components are demanding high levels of current simultaneously, the voltage of the battery  110  may drop below a critical threshold level. When this happens, the device  100  may shut down due to under voltage. For example, in time interval  210 , the CPU  120 , the RFID radio  130  and the WLAN radio  140  are all drawing high amounts of current. As a result, the voltage of the battery  110  may drop below a threshold level  220 , and the device  100  may shut down. Those of skill in the art will understand that  FIG. 2  is only intended to indicate qualitatively the effect that the current demands of the various components may have on the voltage of the battery  110 , and that no precise quantitative current or voltage measurements are indicated, because these will depend on the individual device and its components. 
         [0011]      FIG. 3  illustrates an exemplary method  300  for reducing the peak current demands of a mobile device such as the device  100  of  FIG. 1 . The method  300  is described herein specifically with reference to the components of the exemplary device  100 ; however, those of skill in the art will understand that the same principles may apply to various other types of battery-powered devices. In step  310 , the operations of the device  100  are initiated. This step may include powering on the CPU  120 , initiating an operating system, powering on the RFID radio  130  and the WLAN radio  140 , etc. Further, device initiation may include instructing the RFID radio  130  that it must maintain the amount of current that it draws below a threshold level unless it is otherwise instructed. The threshold level may be determined as a function of the capacity of the battery  110  and the current needs of the CPU  120  and the WLAN radio  140 ; in one embodiment, the threshold current is selected such that when the CPU  120  and the WLAN radio  140  are drawing their maximum possible current and the RFID radio  130  is drawing the threshold current, the voltage of the battery  110  is maintained above a critical level (e.g., a shutdown threshold, a threshold selected to maximize battery life, etc.). Alternately, based on factors such as impedance or remaining capacity, it may be determined whether the RFID radio  130  may need to be shut down. 
         [0012]    Following step  310 , the device may operate within normal parameters as described above (e.g., with the RFID radio  130  not drawing high current draw below the threshold level) until step  320 . In step  320 , the WLAN radio  140  creates and signals, to the RFID radio  130 , a mutual exclusion (“mutex”) instruction indicating that the WLAN radio  140  will not draw high current for some specified time interval. This further indicates that the RFID radio  130  may draw high current during that time interval. It should be noted that the WLAN radio  140  may communicate directly or indirectly with the RFID radio  130 . For example, the mutex may be a software function executed by the CPU  120 , which may signal permission to draw high current by the RFID radio  130 . 
         [0013]    In step  330 , the RFID radio  130  determines whether it needs to increase the current it is drawing beyond the threshold value (e.g., to increase the range of its communications, to make its signals more distinct from background noise, etc.). If a higher current draw is needed, then in step  340  the RFID radio  130  increases the current that it is drawing from the battery  110 . Because the WLAN radio  140  is drawing lower current during the time interval permitted by the mutex, the increased draw by the RFID radio  130 , even coupled with high current draw by the CPU  120 , does not cause the voltage of the battery  110  to drop to problematic levels. 
         [0014]    In step  350 , the RFID radio  130  determines whether it has completed the operations that require it to draw high current. If the RFID radio  130  still needs to draw high current, it determines in step  360  whether the time interval signaled by the mutex is expiring. If the mutex is not expiring, and thus the RFID radio  130  is able to continue to draw high current, the method returns to step  340 , where high current operations continue. However, if the RFID radio  130  determines in step  350  that it no longer requires high current, or determines in step  360  that the mutex is expiring, then it reduces its current draw back to below its original threshold value in step  370 . Those of skill in the art will understand that the determinations of steps  350  and  360  should be made continuously while the RFID radio  130  is drawing high current; for example, they may be made regularly at set time intervals. 
         [0015]    After the RFID radio  130  reduces its current usage in step  370 , in step  380  it signals the mutex to indicate that it has done so. Subsequently, in step  390  the mutex expires and the operations of the device  100  return to the state in which they existed prior to the initiation of the permission-granting in step  320 . Alternately, if the RFID radio  130  never determines, in step  330  during the duration of the mutex, that it needs to draw a high level of current, then steps  340  to  380  are never performed, and the method simply proceeds directly to step  390 , where the mutex expires. 
         [0016]    As discussed above, the use of an RFID radio  130  and a WLAN radio  140  is only exemplary. In other embodiments, the RFID radio  130  may be replaced by a laser scanner, an imager, a WWAN radio, or any other component that may have its current usage limited in order to insure proper device performance. Similarly, the WLAN radio  140  may be replaced by another component that may periodically enter a low current mode at its discretion in order to enable to RFID radio  130  (or similar component) to use more current. 
         [0017]    By the implementation of the above-described exemplary embodiments, the battery  110  may be maintained at a safe voltage level without implementing a software or hardware solution to monitor the current usage of various components. Rather, once the battery has been selected and the threshold values have been defined, the components of the system  100  may communicate with one another, using a simple process, to insure safe battery levels. 
         [0018]    In an alternative exemplary embodiment, a mobile device may include two radios that both have their current draw limited to below predetermined thresholds when the device is in a default state. These thresholds may be determined based on any of the factors discussed above for previously-described embodiments. In such an embodiment, either of the two radios may have the capability to grant permission to the other radio, via mutex, to draw current above the predetermined threshold for a specified time period. The same principle may be applied to devices with more than two components that have their current draw limited in this manner. 
         [0019]    It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.