Abstract:
A fault monitoring and management system integrates a fault controller with the power load functions within the power management device of a battery operated system. Multiple input load lines allow the fault controller to diagnose and disable defective or faulty power load functions that draw current from the system supply or battery. In addition, the fault monitor allows the system to stay operational if the fault is non-catastrophic to the critical functions.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention concerns a fault monitoring and power contingency management system for portable battery-operated devices having multiple operational elements. A faulty circuit or subassembly is detected based on current loading conditions. The fault is isolated by decoupling one or more predetermined elements from the power supply, including the source of the fault. Decoupling the offending circuit or subassembly prevents damage and can enable continued operation of other functional elements in the device.  
       BACKGROUND  
       [0002]     Certain portable battery-operated devices such as cellular telephones, personal digital assistants, cameras and media players, have multiple integrated functions. In addition to the functions that are directly involved in the nominal purpose of the unit, such as voice communications by a cellular telephone or recording image data by a digital camera, other functions of the device are supportive of the main function. Examples are battery chargers, status indication displays, audio annunciators, and the like. Still other functions are convenient combinations of diverse functions in one device. An example of a convenient combination is a cellular telephone capable of recording image data. The communications function of the device is useful to send the image data to another device for viewing or storage.  
         [0003]     All of the functional elements and subassemblies comprise electrical loads on the power supply, typically comprising a battery. In different states of operation, particular loads might be active and sinking current or quiescent and drawing little or no current. Among these loads are devices and subassemblies such as application processors, battery chargers, camera modules, video processors, RF modems, network interface modules (e.g., Bluetooth), MP3 audio players and amplifiers, associated memories, input/output displays and switch interfaces, etc.  
         [0004]     All of these functions are coupled directly or indirectly to the power supply, typically comprising one or more Lithium-Ion batteries. The different functional elements may require voltage regulation. Some functional elements require DC/DC converters and switched mode power supplies (SMPS) to boost the DC voltage level. Three or four different SMPS units may be provided in new cellular designs for driving diverse functions. As many as 27 different voltage outputs may be provided in 2.5 G and 3 G cellular devices. The current load on the battery regularly exceeds one amp in a Time Division Multiple Access (TDMA) system when actively operating in an RF communication mode. The various other supply voltages, many of which are regulated, service audio and RF digital transceiver functions and also accessory switch control, LED drivers, vibrator drivers, ringer drivers, and more. Any one or more of these functions can draw current in the range of 0.01 to 1 Amp.  
         [0005]     Such units also typically include battery charging circuits. In that case, the battery becomes a current sink. Nevertheless, other functions remain subject to activation. The supply of regulated voltages and such current as demanded by the respective functions continues.  
         [0006]     All told, the power supply of a multifunction portable device such as a cellular telephone might service 20 to 30 functions in which one or more of the functional subassemblies is active, and several may be active at once. In a worst case, the power supply (e.g., one 4.2V Lithium Ion battery cell) may need to provide as much as 2 to 3 Amps.  
         [0007]     Some of the functions are served by switching elements, amplifiers and the like, provided on board one or a limited number of integrated circuits. These circuits typically include a digital processor and memory for operation as a controller. Some of the other functions are served as peripheral circuits under switched control of the processor.  
         [0008]     With such a configuration involving a number of current loads, there is a possibility that from time to time some particular load may fail, or an operational state may be assumed wherein an inordinate current load is presented by one or more of the devices. However, the particular current level that should be considered inordinate for a given load or subset of loads may differ between different operational states of the device. It would be advantageous to provide a power management arrangement that is programmed or contains sufficient conditional logic that it can appropriately identify problems that may arise in various operational scenarios, and can act to ameliorate problems, perhaps by making power distribution changes under its control, or decoupling one or more selected loads (possibly including a defective load), or automatically triggering a change to a different operational state of the device.  
         [0009]     A power supply management scheme could prevent loss of communications or keep the battery from discharging more quickly than necessary or otherwise allocate the available power supply capacity to high priority uses. The available power would then provide service to certain priority functions and to retract support for other functions that may be malfunctioning or are considered low priority under the circumstances. With the increasing number of additional functions being served in the latest multifunction portable devices, the possibility and complication of these problems present challenges.  
         [0010]     Simple switching schemes for limiting damage in the event of component failure along a current supply path are known. These schemes include thermal threshold shutdown devices, current fold-back limiting, rectifiers, fuses and so forth. Current limiting circuits contained in voltage regulators can be arranged to switch the regulator current output off, or into a low-current-output condition, when current drawn by a load exceeds some instantaneous or time-integrated threshold. Such circuits also can be made to emit a signal or to activate an indicator in the event of such a fault. However, reliance on internal current limiters in voltage regulators is not an optimal solution in a device having multiple loads and varying operational states. For example, a current fault threshold for a current limiting regulator is generally set at the very highest level of current that might be drawn in any operational state, and shuts down the output when the level is exceeded. Such a regulator provides protection against self damage, but It would be advantageous to have a more adaptive way to react to conditions, perhaps monitoring current loading conditions for a group of loads and using different current fault thresholds for respective loads in different operational states. What is needed is a sophisticated way to detect and to respond appropriately to current loading conditions involving a plurality of loads and operational conditions. By sensitivity to varying conditions, loads and regulators can be protected and the device also can appropriately allocate available power to loads that are considered priority loads in the particular operational state of the device at the time.  
         [0011]     Even if an offending load is readily identifiable, it would also be advantageous to react with due consideration for the nature of the load and not necessarily simply to disable the offending load while continuing to serve other loads. Loads may be related, and there may be no point in providing current to a load that depends on operation of some other load once the other load has been turned off. For example, it is not useful to disable a transceiver function in a cellular telephone, even in adverse low battery or high current draw circumstances, while continuing to serve the audio or digital data processing functions that collect or process information fed to or from the transceiver. Loads may have priorities, and it may be desirable to attempt to maintain ongoing operations at the expense of less important features. For example, it may be desirable to maintain communications over audio playback or image capture capabilities, even if it is the communications circuits that appear to be faulty or marginal.  
         [0012]     In order for a portable device to be capable of power management, the power distribution arrangements need to be configured to permit separate monitoring and separate control of loads, and potentially also to distinguish between internal and external loads. Such configurations and the control of the configuration to appropriately allocate power in a multifunction device, are novel aspects of the present invention. A power distribution control is integrated with due regard to the complexity of a cellular telephone or similar device, so as to react appropriately to a current fault, to discriminate among more and less critical functions, and where possible to allow the cellular device to continue functioning. The invention mitigates the impact of a failure of non-critical functions on the critical functions of the device, and provides for appropriate allocation of power supply capacity. Furthermore, the invention comprises a diagnostic tool that is useful for troubleshooting, repair, and signaling or indicating the state of operational conditions to the user.  
       SUMMARY OF THE INVENTION  
       [0013]     A novel power allocation and power fault controller is provided, especially for a multifunction portable device such as a cellular telephone and camera combination, or an MP3 player with data communications capability, etc. This power controller is arranged to monitor and distinguish among multiple functional load elements that are coupled to one or more power sources of the device. The power controller manages the portable device by sensing power availability and load conditions, potentially providing one or more fault indications, and allocating available power in a manner that ameliorates the adverse consequences of failure of particular load elements, reserving power for selected functions at the expense of others. The portable device is configured to provide distinct power distribution paths to multiple loads that otherwise might be arranged in parallel. The paths comprise current sense feedback to the power controller and switching or power limitation controls responsive to the power controller and/or to a supervisory system processor. The power controller and the system processor discriminate among the loads by function, power draw requirements and the like, versus the operational status of the portable device. In this way, loads can be monitored and isolated where necessary. Available power is allocated. Operations and use of power are varied to deal effectively with situations that arise.  
         [0014]     The power management control function can be one of various functions of a main processor of the portable device. In an exemplary embodiment, however, the power fault detection and power control also rely in part on a dedicated power fault controller. The power controller receives load sensing signals such as threshold over-current indications, from a plurality of power load functional elements or subsets of two or more elements. The input signals to the power controller enable assessment of conditions and information needed to determine a course of action when a fault occurs. The controller provides a centralized manager that can evaluate the fault indicators. The controller can shut down the offending function (typically by decoupling from the supply but also potentially by limiting the current feed), and generates an interrupt and status report to the system processor. The system processor and/or the power fault controller determine a course of action.  
         [0015]     Exemplary responsive actions may include recycling the offending function to attempt to reset the fault condition, changing the availability of services to eliminate a power fault condition or to redistribute available power, or sending an error message to the user or to a remote service technician. Non-critical functions can be disabled to deal with a load failure or to deal with particular power conditions. The reallocation of power supply capacity is tailored to reserve if possible the critical operations of the portable device (such as the ability of a cellular phone to place calls), and decisions about what operations shall or shall not be regarded as critical is made according to the programming of the fault controller and/or the device control processor, based on the system inputs and the sensed status of the various loads.  
         [0016]     These and other aspects of the invention will be apparent to those skilled in the art in view of the following discussion and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The foregoing will in part be obvious and in part be pointed out more fully hereinafter in connection with a written description of preferred embodiments of the present invention illustrated in the accompanying drawings in which:  
         [0018]      FIG. 1  is a schematic block diagram of the fault controller according to the invention.  
         [0019]      FIG. 2  is a schematic diagram illustrating further aspects of the invention as discussed below.  
         [0020]      FIG. 3  is a block diagram illustrating an alternative embodiment that is similar to  FIG. 2  but has voltage regulators with current-sense and/or current-limiting circuits included therein. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]      FIG. 1  illustrates an exemplary battery operated system  10  implementing a fault controller  12  according to an aspect of the invention. The system is exemplified in a cellular telephone as shown by the illustration of RF and audio CODEC functions, but can also be embodied in other devices that have a plurality of loads. The loads are selectively activated, e.g., being switchably coupled to the power supply or alternatively being directly coupled to the power supply but switchable between more or less active versus quiescent states of operation. Subsets comprising one or more of the loads may be drawing current in a given operational scenario, whereas others of the loads may be inactive or decoupled from the power supply.  
         [0022]     The apparatus comprises a power fault controller  12  that can comprise a processor or a series of gates, arranged to assess operational status and to report to a system controller  22 . The power fault controller  12  can be coupled to a temperature monitor  15   a  for developing a fault indication signal, and a thermal shutdown element  15   b  via suitable signal lines  71   a ,  17   b , respectively. In addition to such a thermal protection arrangement, the fault controller is coupled to a variety of elements  16   a - 16   e , that sink or source current in different operational states.  
         [0023]     The power managed device includes a program for operating the system controller  22  and input/output devices including manually operable switch inputs  16   a  and indicators such as LEDs coupled to drivers  16   b  are more or less directly coupled to the controller  22 . Switching between operational states is partly a matter of a user&#39;s operation of a keyboard (KBD) and/or accessory switches  16   a , and also is determined as a programmed matter by the system controller  22  in conjunction with inputs from the user and from signals received, e.g., from RF/Codec element  16   e.    
         [0024]     Some of the load devices are involved in primary functions of the device, such as communications in a cellular telephone embodiment requiring user operated switch selections, local display of information under control of the system controller  22 , and remote signaling over the RF/Codec element. These functions can be accorded a higher priority than other functions, particularly in a low battery condition as determined by the battery charger element  16   c  and reported to the fault controller  12 . The fault controller  12 , either independently or in conjunction with signaling between the fault controller  12  and the system controller  22 , determines the operational state and determine whether one or more loads will be decoupled so as to conserve battery power, to reduce the rate of discharge or otherwise to control power consumption.  
         [0025]     Throughout the drawings, the same or functionally comparable elements have been identified where possible using the same reference numbers.  FIG. 2  shows a number of loads that have separate or shared regulators that are controlled by the fault controller for regulating the current from the basic power supply, namely a battery, to the respective loads. In connection with the example of a cellular telephone wherein the communication functions receive priority, the respective load functions  24  could be data storage and retrieval functions, clock and alarm functions, camera functions such as display, record picture, flash, audio record or playback, etc.  
         [0026]     It is possible in a given state of operations that one or more of the functions advantageously can be disabled in favor of another function, either by programmed decision or by user selection among alternatives offered by a programmed process associated with the controller  22 .  
         [0027]     Battery operated system  10  in  FIG. 1  comprises a power management device  14  having at least one fault status detector  15   a - 15   b  and a plurality of power loads  16   a - 16   e . Examples that may be implemented as fault status detector  15  include an on-chip temperature monitor  15   a  and a thermal shutdown circuit  15   b . Examples that may be implemented as power loads  16   a - e  include supply regulators, battery chargers, accessory switch control, one or more switched mode power supplies (SMPS), LED drivers, etc. Additional load functions that might advantageously be of limited priority can be, e.g., vibrator drivers, ringer drivers, camera modules, video processors, Bluetooth modules, MP3 audio players, etc.  
         [0028]     A control and/or status signaling line  17   a - 17   b  electrically couples fault controller  12  to fault status detector  15   a - 15   b , by which a fault status signal is sent from fault status detector  15  to fault controller  12 . A plurality of input load lines  18   a - 18   e  electrically couple fault controller  12  to each of plurality of power load functions  16   a - 16   e . Fault controller  12  accepts inputs from power load functions  16 ( a - e ) by means of input load line  18 ( a - e ).  
         [0029]     When a fault occurs, monitoring circuits associated with power load functions  16 ( a - e ) send an indication to fault controller  12  through input load lines  18 ( a - e ). Fault controller  12  may also monitor each fault status detector  15  by polling for status. The monitoring circuits can comprise over-current and/or under-voltage threshold detectors (not shown) or similar devices for generating a signal under predetermined conditions related to current, voltage, temperature, elapsed time or other parameters.  
         [0030]     For example, on-chip temperature monitor  15 ( a ) transmits a temperature signal via fault status line  17   a  to fault controller  12 , by which fault controller  12  can monitor the on-chip temperature as an early warning indicator. Generally, a rise in temperature on the device at a point adjacent to a power sourcing element is an indication of increased average current draw.  
         [0031]     Thermal shutdown circuit  15   b  transmits a thermal shutdown signal via fault status line  17   b  to fault controller  12 , by which fault controller  12  can be alerted of a potentially damaging short or other failure within system  10 . Fault controller  12  can be comprised of a controller or a set of gates that are arranged to react to the severity of a fault by evaluating the fault indicators from plural load elements. The fault controller  12  also can react to other factors, including which function appears to be the source of the error, which functions are presently active, and whether the offending and active functions are critical or non-critical functions in view of the operative state of the battery operated system  10 .  
         [0032]     The fault controller can signal the system controller  22 , which can be programmed to warn the user and/or to decline to initiate non-critical functions in predetermined operational states wherein a critical function may be adversely affected. In one aspect, the fault controller  12  can react to the severity of the fault, for example reacting to a potential short circuit current fault by decoupling an active load. The fault controller  12  can also be arranged to revise operations by suspending a function temporarily while another function proceeds. The fault controller  12  can determine a course of action either independently or together with signaling between the fault controller  12  and the system controller  22  as well as a user. User input can be prompted on the display drivers or by audio signaling and received over the accessory switch and/or KBD inputs.  
         [0033]     Referring to  FIG. 2 , voltage regulators  16   e  for the various load functions can be more or less proximal to a battery power source or to the SMPS DC/DC inverter  16   d . The current draw of loads can be determined by voltage threshold detection using current sense resistors R 1 -R 3  or, although not shown in  FIG. 2 , using current replica repeaters built into the regulators themselves. The potential actions may include (without limitation) shutting down an offending load function  24 , shutting down a regulator providing current to a function or controlling the regulator to decrease the current available, generating an interrupt or setting an appropriate status indication in a status register to provide information to controller  22  (which controller can be programmed to reconfigure permitted operations and/or power supply allocation.  
         [0034]     According to one aspect, the fault controller can contain a nonvolatile status register containing plural bits (3 bits being shown to represent eight different values), or that power to the status register be maintained at least in the event of a dire condition such as high temperature cutoff (e.g., above 155 degrees F.) associated with one of the respective load functions  24 . This allows for some diagnosis of the offending fault if the system recovers and the system supply has not been lost or discharged by the fault. Furthermore, the severity of the fault can also be gauged with the assistance of on-chip temperature monitor  15   a  if necessary (i.e. the chip is rapidly heating due to a fault somewhere in the system).  
         [0035]     According to the foregoing description, it is an aspect of the invention that a portable device is made fault tolerant, particularly in the event of a high current draw by a particular load device. Although a single regulator might readily be provided with a switched output to snub high current conditions, the point of the invention is to provide a way to preprogram a considered response to a fault condition, including considerations for dealing most appropriately with the fault condition in view of operational status and the nature of the fault.  
         [0036]     An alternative embodiment of the invention is shown in  FIG. 3 . This embodiment resembles  FIG. 2  but as shown, the voltage regulators  16   e  are provided with internal current limit circuits. According to one aspect, the fault sensor and controller  12  as described above is arranged to receive current indication signals from the voltage regulators, for example a state signal from respective voltage regulators having at least two and potentially more different signal levels, from which the state of the particular regulator  16   e  can be surmised. The fault sensor has outputs coupled back to control the regulators  16   e , as shown by the broken line in  FIG. 3 . This control preferably includes an ability to disable the output of the voltage regulator. According to one embodiment, the fault sensor also can be arranged to dictate one or more current threshold levels to the regulators  16   e , e.g., with respect to instantaneous or average current draw. In that case, one way to disable the regulator  16   e  may be to set a very low current output threshold during an operational state wherein the respective load  24  would draw current if available. In this way, the fault sensor and controller can obtain control input information and generate control output signals that enable a relatively sophisticate set of operational states and current thresholds.  
         [0037]     While considerable emphasis has been placed on the preferred embodiments of the invention illustrated and described herein, it will be appreciated that other embodiments can be made and that many changes can be made in the preferred embodiment without departing from the principles of the invention. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.