Abstract:
A power monitoring device for use in an electronic device that operates in a low power mode from a removable battery module. The power monitoring device comprises a module that attaches to the electronic device in place of the battery module. The module has first battery contacts for interfacing with second battery contacts disposed in the electronic device. Attachment of the module causes the electronic device to operate in the low power mode. The power monitoring devices also comprises power supply circuitry for providing a supply voltage substantially similar to a voltage level provided by the removable battery module, and power measurement circuitry for measuring a power level supplied by the power supply circuitry.

Description:
TECHNICAL FIELD OF THE INVENTION 
   The present invention is directed to apparatuses and methods for testing the power consumption of a wireless mobile station and, in particular, to a battery replacement module for testing the power consumption of a mobile phone. 
   BACKGROUND OF THE INVENTION 
   The manufacturers of wireless mobile stations, especially cellular telephones, continually try to improve the reliability and performance of wireless products in order to create new markets and to expand existing markets. One very important performance characteristic of wireless mobile stations is power consumption. The users of wireless mobile stations value mobility and therefore place great importance on a long battery life. For example, cell phone users prefer to spend as little time as possible charging their cell phones and prefer cell phones that can operate for long durations before recharging. The same is true for users of laptop computers operating over a wireless network. 
   A wireless mobile station that has high power (i.e., high current) consumption can operate on battery power only for relatively short durations and must be recharged frequently. To extend battery life, manufacturers have worked both on improving battery capacity and on reducing the power consumption of wireless mobile stations. However, accurately determining the average time between recharges for a wireless mobile station is a complicated task due to fluctuations in power consumption caused by environmental conditions and the functions being performed by the mobile station. 
   Thus, accurate determination of power consumption (i.e., current drain) involves extensive testing of wireless mobile stations under varying conditions and while performing different types of tasks. These test are used to determine, among other things: 
   1) maximum battery life; 
   2) average battery life; 
   3) sleep mode power characteristics (e.g., wake-up time upon receiving a page); 
   4) standby mode, talk time; and 
   5) current drain during specific operations (e.g., sending e-mails, answering a call, and the like). 
   However, simply connecting a wireless mobile station to an external power cord and measuring the current drain in the power cord is an inaccurate method for determining true power consumption. This is because many wireless mobile stations operate differently (and therefore have a different current drain) when attached to an external power supply. When the wireless mobile station detects power from an external supply, the mobile station usually operates in a “high power” mode that provides better signal reception and transmission at the expense of higher power consumption. 
   However, when the external power source is removed and the mobile station operates only from its own battery, the mobile station may operate in a low power mode that saves power in a number of ways. For instance, a cell phone that is not in use may operate in a slotted mode of operation in which the cell phone cycles power one and off to some of its internal components. For instance, the cell phone may apply power to its receiver for one quarter of a second and may remove power to its receiver for three quarters of a second (25% duty cycle). The cell phone can only detect incoming calls during the time when power is applied to the receiver, but power consumption is reduced 75% in the receiver. 
   As a result, measuring current drain from an external power source does not provide an accurate assessment of power consumption because the cell phone does not operate in a low power mode. To compensate for this, some manufacturers have implemented intrusive means of measuring current consumption, such as altering the circuitry of the wireless mobile station to include test leads that can be connected to a suitable measuring device. However, such intrusive methods are not preferred because the required circuit alterations are of a delicate nature and are not robust. This makes field-testing a mobile station difficult. Also, such alterations would only be made on a small sample of wireless mobile stations, not all such devices. Thus, it is not useful for testing any mobile station at random. 
   Therefore, there is a need for improved apparatuses and methods for testing the power consumption (i.e., current drain) of a wireless mobile station. In particular, there is a need for a non-intrusive apparatus for performing power consumption tests in a wireless mobile station. 
   SUMMARY OF THE INVENTION 
   The present invention is a power monitor module that provides more accurate and convenient testing of a mobile station during its normal operating mode of operation and in particular, during its low power (or power saving) mode of operation. The power monitor module “spoofs” the appearance of a battery module of a wireless mobile station, thereby causing the mobile station to operate as if the mobile station is operating only from battery power. 
   To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a power monitoring device for use in an electronic device capable of operating in a low power mode from a removable battery module. According to an advantageous embodiment of the present invention, the power monitoring device comprises: 1) a module capable of being attached to the electronic device in place of the battery module, the module having first battery contacts thereon capable of interfacing with second battery contacts disposed in the electronic device, wherein attachment of the module enables the electronic device to operate in the low power mode; 2) power supply circuitry capable of providing to the first battery contacts a supply voltage substantially similar to a voltage level provided by the removable battery module; and 3) power measurement circuitry capable of measuring a power level supplied by the power supply circuitry to the electronic device. 
   According to one embodiment of the present invention, the power measurement circuitry comprises a load resistor through which a power supply current of the electronic device flows. 
   According to another embodiment of the present invention, the power measurement circuitry further comprises a sampling circuit for sampling a voltage across the load resistor caused by the power supply current of the electronic device. 
   According to still another embodiment of the present invention, the power measurement circuitry further comprises a microcontroller for reading the sampled voltage from the sampling circuit. 
   According to yet another embodiment of the present invention, the microcontroller calculates at least one power parameter from a plurality of sampled voltages read from the sampling circuit. 
   According to a further embodiment of the present invention, the microcontroller transfers the sampled voltage or at least one power parameter to an external testing device. 
   According to a still further embodiment of the present invention, the microcontroller stores the sampled voltage or at least one power parameter in a random access memory coupled to the microcontroller. 
   According to a yet further embodiment of the present invention, the microcontroller displays the sampled voltage or at least one power parameter on a display devices associated with the power monitoring device. 
   The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. 
   Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects, and in which: 
       FIG. 1  is a rear view of a conventional wireless mobile station with the battery module removed; 
       FIG. 2  is a first perspective view of a power monitor module suitable for replacing the battery module of the conventional wireless mobile station in  FIG. 1  according to one embodiment of the present invention; 
       FIG. 3  is a second perspective view of the power monitor module in  FIG. 2  according to one embodiment of the present invention; and 
       FIG. 4  illustrates the testing circuitry in the power monitor module depicted in  FIGS. 3 and 4  according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 through 4 , discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged wireless mobile station. 
     FIG. 1  is a perspective view of the back of conventional wireless mobile station  100  with the battery module (not shown) removed from battery compartment  110 . In the illustrated embodiment, wireless mobile station  100  is a cellular phone. However, this should not be construed to limit the operation of the present invention. In general, the present invention may be implemented in any type of portable device, including a laptop computer, an electronic organizer, or the like. 
   Visible within battery compartment  110  are negative battery contact  111  and positive battery contact  112 . During normal operation, when a battery module is installed, contacts on the battery module touch against negative battery contact  111  and positive battery contact  112  to supply power to wireless mobile station  100 . However, if an external power supply, such as a battery recharger, is plugged into mobile station  100 , mobile station  100  will detect power from its external jack (not shown) and draws current from the external power supply instead of the battery module. At the same time, mobile station  100  typically switches to a high power mode that draws a greater amount of current than when mobile station  100  operates solely from its battery module. 
     FIG. 2  is a first perspective view of power monitor module  200 , which is suitable for replacing the battery module of conventional wireless mobile station  100  according to one embodiment of the present invention. The surface of power monitor module  200  shown in  FIG. 2  is the inner surface that faces into battery compartment  110  of mobile station  100 . Negative battery contact  211  and positive battery contact  212  are disposed on the inner surface of power monitor module  200 . 
   When power monitor module  200  is inserted into compartment  110  of mobile station  100 , negative battery contact  211  contacts negative battery contact  111  and positive battery contact  212  contacts positive battery contact  112 . In this way, power may be supplied to mobile station  100  through power monitor module  200 . Moreover, if no other external power is supplied, mobile station  100  will detect power only from inserted power monitor module  200 , which appears to mobile station  100  to be nothing more than a battery module. 
   Mobile station  100  can operate in a power saving mode to conserve battery power if a number of conditions are true. These conditions include: 1) the absence of an external power supply connected to mobile station  100 ; 2) mobile station  100  is not operating in slotted mode; 3) a battery supply is present; and 4) other conditions may be applicable. However, assuming conditions 1) and 2) are true, as well as any other necessary conditions, the presence of power monitor module  200  enables mobile station  100  to operate in a power saving mode to conserve battery power. 
     FIG. 3  is a second perspective view of power monitor  200  according to one embodiment of the present invention. The surface of power monitor module  200  shown in  FIG. 3  is the outer surface that faces out of battery compartment  110  of mobile station  100 . Power monitor module  200  receives external power via power cord  310 . Power monitor module  200  may transmit and receive data and commands via communication line  320 , which may be, for example, an RX-232 cable connected to external test equipment or a personal computer (PC). Optionally, power monitor module  200  may include display  330  for displaying measured power (i.e., current) values recorded by power monitor module  200 . 
     FIG. 4  illustrates the testing circuitry in power monitor module  200  according to one embodiment of the present invention. Power monitor module  200  comprises voltage regulator  410 , voltage regulator  420 , microcontroller  430 , load resistor  440 , analog-to-digital converter (ADC)  450 , random access memory (RAM)  460 , and read-only memory (ROM)  470 . Microcontroller  430 , ADC  450 , RAM  460 , and ROM  470  are coupled by, and communicate across, communication bus  480 . Optionally, power monitor module  200  may also comprise charger  485  and battery  490 . 
   According to one embodiment of the present invention, external power may be supplied to voltage regulator  410  via power cord  310 . Voltage regulator  410  converts the external power to the voltage level normally produced by a battery module inserted into mobile station  100 . For example, the output of voltage regulator  410  may be +3.6 volts. The battery-level output is coupled to positive contact  212  via load resistor  440 . Negative battery contact  212  is coupled to the negative reference (i.e., ground) of the external power supply. 
   Load resistor  200  is a very small (e.g., 0.1 ohms) and very precise (e.g., +/−0.1%) load that is used to measure the current flowing from voltage regulator  410  into mobile station  100  via positive battery contact  212 . The load current into mobile station  100  creates a voltage across load resistor  200  that is continually sampled by ADC  450 . Microcontroller  430  reads the voltage values sampled by ADC  450  and uses the sample values to determine the power consumption of mobile station  100  under various conditions and during the execution of different tasks. 
   Microcontroller  430  executes a control program stored in ROM  470  and uses RAM  460  as a scratchpad to store intermediate calculations and, if necessary, to store sampled voltages and/or final calculations. According to an exemplary embodiment of the present invention, RAM  460  may be a non-volatile memory, such as a flash RAM. If microcontroller  430  is coupled to an external test control device (e.g., a PC) via communication line  320 , microcontroller  430  may transfer the sampled voltage values directly to the external test control device. Alternatively, microcontroller  430  may calculate important parameters, such as the average value, or the peak value, over a selected time period, and transfer only the important parameters to the external test control device. If microcontroller  430  is not coupled to an external test control device, microcontroller  430  may instead transfer the sampled voltage values or the important parameters to display  330  for subsequent display to a user of mobile station  100 . 
   Optional charger  485  and battery  490  may be implemented in order to field test the power consumption of mobile station  100 . Charger  485  charges battery  490  during time periods when power cord  310  connects power monitor module  200  to an external supply. When power cord  310  is disconnected, battery  490  provides temporary internal power to voltage regulator  410  and voltage regulator  420 . This enables power monitor module  200  to continue to operate as described above, except without external power. Thus, the user of mobile station  100  is free to move around while testing the power consumption of mobile station  100 . Power sample values and important parameters may then be displayed on display  330  or may be stored in RAM  460  for later retrieval via communication line  320 . 
   Advantageously, the external power for power monitor module  200  may be supplied via power cord  301  from an actual battery that is compatible with mobile station  100 . Such a configuration permits power monitor module  200  to accurately characterize the external battery as well as mobile station  100  under a realistic load (i.e., mobile station  100 ). Power monitor module  200  would monitor power consumption on mobile station  100  and voltage on the external battery. 
   Although the present invention has been described in detail, those skilled in the art should understand that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.