Power switching unit of a portable telephone capable of monitoring and controlling a battery supply voltage thereof

Abstract

A power switching unit of a portable telephone which stores data such as telephone numbers and operates with a battery. The unit includes a battery for supplying power to a radio unit and a control unit which contains a data storage function and controls operation of the radio unit, a first voltage monitor for monitoring a supply voltage of the battery to output a first voltage drop signal when the supply voltage falls below a first predetermined value, and a communication disconnection device for stopping power supply to the radio unit upon reception of the first voltage drop signal. The power switching unit further includes a voltage adjustment device for adjusting voltage supplied to the control unit from the battery to a predetermined operating voltage of the control unit for supplying it to the control unit.

What is claimed is:  
     
         1 . A power switching unit of a portable telephone comprising a radio unit and a control unit which contains a data storage function and controls operation of the radio unit, said power switching unit comprising: 
 a battery for supplying power to the control unit and the radio unit;    first voltage monitor means for monitoring a supply voltage of said battery to output a first voltage drop signal when said supply voltage falls below a first predetermined value; and    communication disconnection means for stopping power supply to said radio unit upon reception of said first voltage drop signal.    
     
     
         2 . The power switching unit of the portable telephone as claimed in  claim 1  further including a display, wherein said control unit causes said display to display a communication disable message when said first voltage drop signal is received.  
     
     
         3 . The power switching unit of the portable telephone as claimed in  claim 1  further including: 
 second voltage monitor means for monitoring the supply voltage of said battery to output a second voltage drop signal when said supply voltage falls below a second predetermined value lower than said first predetermined value;  
 control disconnection instruction means for outputting a control disconnection signal upon reception of said second voltage drop signal; and  
 control disconnection means for stopping power supply to said control unit upon reception of said control disconnection signal.  
 
     
     
         4 . The power switching unit of the portable telephone as claimed in  claim 1  further including voltage adjustment means for adjusting voltage supplied to the control unit from said battery to a predetermined operating voltage of said control unit for supplying it to said control unit.  
     
     
         5 . The power switching unit of the portable telephone as claimed in  claim 3  further including a display, wherein said control disconnection instruction means is adapted to output said control disconnection signal in a predetermined time after reception of said second voltage drop signal and said control unit causes said display to display a prompting message for said predetermined time for requesting the user to charge said battery.  
     
     
         6 . The power switching unit of the portable telephone as claimed in  claim 4  further including: 
 third voltage monitor means for monitoring voltage supplied to said voltage adjustment means to output a power shutoff signal when said voltage falls below a lower limit of input voltage at which said voltage adjustment means can work; and  
 power shutoff means for stopping power supply to said control unit and said radio unit upon reception of said power shutoff signal.  
 
     
     
         7 . The power switching unit of the portable telephone as claimed in  claim 4  further including fourth voltage monitor means for monitoring output voltage from said voltage adjustment means to output a reset signal when said output voltage falls below a third predetermined value, wherein said control unit is adapted to be reset upon reception of said reset signal.  
     
     
         8 . The power switching unit of the portable telephone as claimed in  claim 7  wherein said first predetermined value is a lower limit of voltage at which said radio unit can work and said third predetermined value is a lower limit of voltage at which said control unit can work, said third predetermined value being less than said first predetermined value.  
     
     
         9 . A power switching unit of a portable telephone comprising a radio unit and a control unit which contains a data storage function and controls operation of the radio unit, said power switching unit comprising: 
 a first battery for supplying power to the control unit;    a second battery normally for supplying power to the radio unit;    first voltage monitor means for always monitoring a supply voltage of said first battery to output a first voltage drop signal when said supply voltage of said first battery falls below a first predetermined value;    power supply instruction means for outputting a power supply instruction signal upon reception of said first voltage drop signal;    power supply means for supplying power to said control unit from said second battery upon reception of said power supply instruction signal;    second voltage monitor means for always monitoring a supply voltage of said second battery to output a second voltage drop signal when said supply voltage of said second battery falls below a second predetermined value;    power disconnection instruction means for outputting a power disconnection signal upon reception of said second voltage drop signal; and    power disconnection means for stopping power supply to said radio unit from said second battery upon reception of said power disconnection signal.