Abstract:
An apparatus and method for disabling a charging counter circuitry within a battery charger is disclosed. The apparatus includes circuitry connected to a pin associated with the charging counter circuitry of the battery charger, said circuitry receiving a signal from a device connected to the battery charger. The circuitry disables the charging counter circuitry responsive to a signal from the device at a first level and enables the charging counter circuitry responsive to the signal from the device at a second level.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to battery chargers, and more particularly, to a system and method for more accurately tracking the period of time a battery charger is actually charging an associated battery. 
     BACKGROUND OF THE INVENTION 
     Battery chargers are devices that enable the charging of many portable hand-held electronic devices, such as cell phones, PDAs, laptop computers, portable e-mail receivers, pagers, etc. When a portable electronic device is placed within the battery charger, the charger will replenish the battery pack associated with the portable electronic device. However, if the portable electronic device placed within the battery charger is in a use mode while within the charger, the charge current being provided by the battery charger, rather than recharging the battery associated with the portable electronic device, instead powers the operations of the portable electronic device. 
     Many battery chargers additionally include a functionality for monitoring a charge TIME pin  106  for a battery connected to the battery charger. Upon connection of the battery to the battery charger, a charge counter begins counting the length of time the battery is connected. When a preset period of time expires and no indication has been received that a connected battery is fully charged, a fault indication of some type may be provided. The problem with this configuration is that if the charge current from the battery charger is being used to power a use mode of the portable electronic device rather than to charge a battery, the counter is still counting time as if the charge current is being used to charge the battery. Thus, a false fault signal may be generated by the battery charger. Traditionally, individuals have disabled the time out function within the battery charger in order to solve this issue. However, this causes the battery charger to lose its time out protection feature for situations when the time out counter would actually detect a fault condition. Thus, some system and method for enabling an accumulation of actual charging time without falsely registering use time of a connected battery is desired. 
     SUMMARY OF THE INVENTION 
     The present invention disclosed and claimed herein, in one aspect thereof, comprises an apparatus and method for disabling charging counter circuitry within a battery charger. Circuitry is connected to a pin associated with the charging counter circuitry of the battery charger and the circuitry receives a signal from a device connected to the battery charger. The circuitry, responsive to a signal from the device at a first level, disables the charging counter circuitry. Responsive to a signal from the device at a second level, the circuitry will enable the charging counter circuitry of the battery charger. 
    
    
     
       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 description taken in conjunction with the accompanying Drawings in which: 
         FIG. 1  is a schematic diagram of a battery charger including circuitry for disabling a charging counter of the battery charger during a use mode; 
         FIG. 2  is a timing diagram illustrating the operation of a counter within the battery charger responsive to a use mode signal of an associated electronic device; 
         FIG. 3  is a flow diagram describing the operation a battery charger responsive to a talking mode signal from a cellular telephone; 
         FIG. 4  is a block diagram illustrating a battery charger connected to a device with associated battery that may have its charge counter enabled and disabled; and 
         FIG. 5  is a flow diagram illustrating the operation of the circuit of  FIG. 4  responsive to a use mode signal from the device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIG. 1 , there is illustrated a battery charger  102  configured to charge a battery of an associated portable electronic device. The electronic portable device may comprise a cell phone, PDA, laptop computer, portable email receiver, pager, etc. The battery charger  102  includes charge counter circuitry to determine how long a battery of a connected electronic device has been charging. The charge counter circuitry may be implemented as discrete circuits, in one or more integrated circuits, in software executed on a microprocessor or as a combination of software or hardware. The battery charger  102  may have its internal charge counter circuitry disabled responsive to a use mode input applied to an NMOS transistor  104  connected to the TIME pin  106  of the battery charger  102 . 
     The TIME pin  106  is connected to internal charge counter circuitry within the battery charger  102  that includes an oscillator, internal clock and counter that may be used for counting the period of time that a battery charger  102  is providing a charging current to a connected battery. Connected in parallel between the TIME pin  106  and ground, are a capacitor  108  and the NMOS transistor  104 . The capacitor  108  is connected between node  110  and ground and the drain/source path of the NMOS transistor  104  is connected between node  110  and ground. The gate of the NMOS transistor  104  is connected to receive the use mode signal from an attached electronic device. In one embodiment of the present disclosure, the use mode signal comprises a talking mode signal provided from a cellular telephone associated with the battery charger  102 . The talking mode signal provides an indication that the cellular telephone is in use, and thus any charging current provided by the battery charger  102  is provided to the operation of the connected cellular telephone rather than to charging the battery of the cellular telephone. 
     When the use/talking mode signal goes high, the NMOS transistor  104  is turned on, and the TIME pin  106  is shorted directly to ground. This causes no clock signal to be generated from the TIME pin  106  by the charge counter circuitry while the TIME pin  106  is shorted to ground. The TIME pin  106  provides sourcing and sinking current to charge and discharge the external capacitor  108  to generate saw-tooth waveform when not shorted. When a user completes using/talking on the associated cellular telephone/electronic device, the talking/use mode is completed and the talking/use mode signal goes low. When this occurs, the NMOS transistor  104  is turned off, and the TIME pin  106  is no longer shorted to ground. This enables the charge counter circuitry within the battery charger  102  to continue to count the time period the associated battery is being charged. Thus, by shorting the TIME pin  106  to ground using the transistor  104  responsive to a talking/use mode signal from an associated electronic device, a counter within the battery charger  102  will only count the time that an associated battery is actually being charged. 
     Referring now to  FIG. 2 , the correspondence between the use mode signal provided from an associated electronic device and a clock signal provided from the TIME pin  106  are illustrated. As can be seen between time t 0  and time t 1 , the use mode signal is low indicating that a user is not using the associated electronic device, and the charge current is actually charging the battery. In this case, the clock signal from the TIME pin  106  between time t 0  and t 1  is active. At time t 1 , the use mode signal goes high indicating that a user is using the associated electronic device, and the charge current is no longer charging the associated battery. When this occurs between time t 1  and time t 2 , the TIME pin  106  is connected to ground, and the clock signal provided from the TIME pin  106  is discontinued. When the use mode signal returns to low at time t 2 , indicating that the user is no longer using the associated electronic device, the clock signal is again provided at the TIME pin  106 . This process continues until time t 3  when the use mode signal goes high again, turning off the clock signal at TIME pin  106 . 
     Referring now back to  FIG. 1 , the remainder of the pins of the battery charger  102  are connected to provide the various functionalities appropriate to the battery charger  102 . A voltage source  112  is connected between the voltage in node  114  and ground. A resistor  116  is connected between node  114  and the STATUS pin  117  of the battery charger  102 . The STATUS pin  117  will remain low during the time period that a battery connected to the battery charger  102  is charging. Once the battery has been completely charged, the STATUS pin  117  goes high to provide an indication of this to the user. A resistor  118  is connected between node  114  and the FAULT pin  120  of the battery charger  102 . The FAULT pin  120  provides an indication of various fault occurrences within the battery charger  102 . For example, if a connected battery to the battery charger  102  has been charging for a predetermined period of time and the battery has not yet been completely charged, an indication of this may be provided via the FAULT pin  120 . The input voltage is provided to the battery charger  102  via VIN pins  122  and  124 . The battery charger  102  is connected to ground via pin VSS. 
     TOEN pin  130  is the time out enable pin used to completely disable the charge counter circuitry. Previous to the solution described by the disclosure herein, this is the manner in which the problem of the charging counter counting not directly counting the time associated with charging of the battery was solved. The counter was disabled using the TOEN pin  130 . However, as described herein above, this solution prevented use of the charging counter rather than providing a means for more accurately counting the charging time. The ENABLE pin  132  provides the ability to enable and disable the battery charger. The V2P8 pin  134  provides a DC voltage from the battery charger  102  and is connected to a first node  136 . A capacitor  138  resides between node  136  and ground. Additionally, a series combination of resistors  140  and  142  are connected between node  136  and ground. The TEMP pin  144  of the battery charger  102  is connected to a node  146  between resistors  140  and  142 . The TEMP pin  144  is used for measuring the temperature of the battery connected to the battery charger  102 . The IREF pin  148  is connected through resistor  150  to ground. The IREF pin  148  enables the programming of the charge current for a battery connected to the battery charger  102 . The IMIN pin  152  is connected to ground through a resistor  154 . The IMIN pin  152  enables the programming of the minimum current that indicates that a connected battery to the battery charger  102  has been completely charged. The VSEN pin  156  is connected to a node  158  to which the battery is connected for charging. Node  158  is connected to node  160  through a resistor  162 . VBAT pins  166  and  164  are connected to node  160 . Node  158  is also connected through a resistor  168  and a capacitor  170  to ground. 
     One use of the above described circuit is with a cellular telephone battery charger  102 . Referring now also to  FIG. 3 , there is illustrated a flow diagram describing the operation of the battery charger and associated circuit of  FIG. 1  for a charger connected to a cellular telephone. The process begins at step  302 . An initial determination is made at inquiry step  304  to determine whether the talking mode is on from the connected cellular telephone. If the talking mode is on, the transistor is turned on at step  306 , and the counter measuring the charging time within the battery charger  102  is turned off at step  308 . Control passes back to inquiry step  304  to determine if the talking mode is still on or off. If inquiry step  304  determines that the talking mode is off, the transistor is turned off at step  310  and the timer counter within the battery charger measuring the charging time resumes operation at step  312 . 
     Referring now to  FIG. 4 , there is illustrated a configuration according to the present disclosure wherein a charger  102  is connected to a first electronic device  402 , having an associated battery  404 . The charger  102  is connected to some sort of DC voltage input source  406 . A counter circuit  408  located within the battery charger  102  is connected to the NMOS transistor  104  and capacitor  108  as described in  FIG. 1 . The NMOS transistor may alternatively be any type of transistor capable of operating in the described manner. The gate of transistor  104  is connected to the device  402  to receive the use mode signal which will turn on and off the transistor  104  and enable and disable the counter  408  within the battery charger  102 . 
     Referring now to  FIG. 5 , there is illustrated the operation of the circuit in  FIG. 4 . Inquiry step  502  monitors for the receipt of a use mode signal from device  402  at the gate of NMOS transistor  104 . When the use mode signal is detected, the transistor  104  is turned on at step  504  and the counter circuit stops operation at step  506 . Control returns to inquiry step  502 . When inquiry step  502  detects a non-use mode signal from the device  402  at the gate of transistor  104 , the transistor is turned off at step  508  and the timer counter starts or resumes at step  510 . 
     Using the above described circuitry and method, a charging time for a battery connected to a battery charger may be more accurately tracked by a charging counter within the battery charger, and the possibility of a false fault signal being generated because of failure of the battery to charge within a predetermined time period is minimized. 
     Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.