Patent Document

This application is a continuation of Ser. No. 09/330,479 filed Jun. 11, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     With the proliferation of cellular phones, there has been pressure to improve the battery power capability to supply these devices. The efficacy of these phones relies on mobility and such mobility requires efficient battery power. From the start the batteries used have been rechargeable, prompting significant development in the structure of rechargeable batteries. Under normal conditions, the charging of such batteries is accomplished by circuitry built into the control microprocessor of the cellular phone. In order to operate, however, the controller requires a minimum voltage level from the batteries. A problem therefore arises when the battery charge is depleted below these minimum levels. 
     It is a purpose of this invention to provide an improved charging system for depleted batteries. 
     One of the prior art solutions to this charging problem is shown schematically in FIG.  1 . In this instance, a start up module is added to the controller circuit to provide a limited initial constant current charge at a low current for example from 100 ma to 180 ma. This charging current is allowed to build the battery voltage to a level which will support the operation of the main controller. The controller will then take over, switching off the start-up charging module and allowing the battery to charge in a more rapid conventional manner. 
     In the start up mode at which the controller  2  is disabled, the start up current must be limited in order avoid excessive power loss. The power loss is caused by the need to dissipate the voltage drop from the charger voltage to the battery voltage. In view of the limited charge current, the start up mode requires an unacceptably long period of time to reach the operative voltage of the controller  2 . 
     It is a purpose of this invention to provide a quicker start up charging mechanism which operates with lower power consumption. 
     SUMMARY OF THE INVENTION 
     In this invention, the start up charging circuitry is replaced by a new and unique low power start up module. The start up module of this invention consists of a pulse generator which is used to cycle the conventional charging circuit. In the start up mode, the controller charging circuit is disabled because of insufficient voltage from the battery. In this invention the charging switch is controlled by the start up module when the battery power is below the threshold of the controller. The start up module generates a pulse chain which cycles the charging switch and thereby turns the standard charging circuit on and off. In this manner a relatively rapid and efficient initial charging of a dead or substantially depleted battery is obtained. A comparator senses the battery voltage, enables the controller charging cycle, and disables the start up charging cycle when the operational threshold voltage for the controller is obtained. 
    
    
     DESCRIPTION OF THE DRAWING 
     The invention is described in more detail below with reference to the attached drawing in which: 
     FIG. 1 is a schematic diagram of a prior art start up charging circuit; 
     FIG. 2 is a schematic diagram of the start up circuit of this invention; 
     FIG. 3 is a chart of the operating steps of this invention; 
     FIG.  4   a  is a graph of battery voltage over an operating cycle; and 
     FIG.  4   b  is a graph of start up capacitor voltage over an operating cycle. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, the prior art charging system consists of external charger  1 , controller  2  and charging switch  3 . A comparator  4 , forming part of the intelligent circuitry of controller  2 , senses the condition of battery pack  5  and provides controller  2  with the data required to operate charging switch  3  and a start up charger  6 . 
     Start up charging module  6  consists of a constant current source connected to the battery pack  5  and enabled by controller  2 . 
     Controller  2  is a microprocessor containing the required hardware and software to manage the operation of a cellular phone in a standard manner. Charger switch  3  is operated by controller  2  in response to the voltage level supplied by battery pack  5  and monitored by comparator  4 . Since the controller  2  requires a certain threshold voltage in order to operate, the charging switch  3  is therefore disabled when battery pack voltage levels are below the threshold. When the supply voltage falls below the threshold, the constant current source is enabled by controller  2  and charging switch  3 , and the comparator  4  is disabled by the signal from the controller  2 . Below the threshold voltage, external charger  1  is not loaded with a sufficiently high current and it will remain in the voltage limited or idle mode. 
     In the prior art system shown in FIG. 1, start up module  6  initially applies a limited charging current to the battery pack  5 . The start up module  6  continues its function until the comparator  4  or controller  2  senses that the output of battery pack  5  has reached the threshold level. It has been found that low level charging currents of 100 ma to 180 ma are effective, but require unacceptable periods of time to charge the battery pack to threshold levels. In addition significant power is used which tends to generate undesirable heat within the current generator of module  6 . 
     According to the system of this invention, in order to accelerate the charging time and to reduce the power loss in the appliance, a start up module  7  is designed as shown in FIG.  2 . Start up module  7  is constructed to generate a pulsating signal suitable for cycling charger switch  8  off and on to restore the voltage of battery pack  10  to a desirable level. 
     Charger switch  8  controls a charger  9  to recharge the battery back  10  in a conventional manner, when connected to an external power supply (not shown). Under normal conditions, controller  11  functions to enable the switch  8  when the voltage of battery  9  is depleted to an undesirable level above the operative threshold of controller  11 . The closing of switch  8  initiates the conventional charging cycle. As was discussed above, a certain threshold battery voltage is required before the controller  11  will function in any manner. The unique start up module  7  of this invention operates to charge the battery pack  10  to the threshold level of controller 
     A comparator  12  senses battery voltage and compares it to the predetermined threshold voltage needed to operate controller  11 . The controller  11  is disabled when the battery voltage falls below the threshold level. 
     The startup charging module  7  consists of a pulse generating circuit  13  which drives an OR gate  14  to cycle the charging switch  8  on and off and thereby apply a pulsed charging current to the battery pack  10  from the charger  9 . In order to power the pulse generating circuit  13  during the process, a capacitor  15  is connected across the charger  9  through a diode  16 . When the charger switch  8  is off, the capacitor  15  is charged by the idle voltage of charger  9 . This provides the operational voltage for the pulse generator  13 . The duty cycle of the pulse generator  13  may be rapid, but it has been found that an off period, sufficient for the capacitor  15  to reach a voltage equivalent of the idle state voltage of the charger  9 , is desirable. Capacitor  15  is selected accordingly. The characteristics of the pulsed signal to the switch  8  will be in part determined by the components selected and the type of cell phone used. 
     In operation, the cellular phone is connected to the charger  9  when charging is warranted. If the comparator  12  senses a battery voltage that is at or above the threshold level for controller  11  to operate, then the charging switch  8  is enabled by the controller  11  according to a stored charging algorithm. The charging operation then occurs in a conventional manner. When the comparator  12  senses that the voltage output of the battery pack  10  has been depleted below the operational threshold of the controller  11 , then the pulse generator  13  will be enabled. The pulsed signal will cycle the charging switch  8  off and on thereby applying a pulsed charging current to the battery, as shown in FIG.  4   a.    
     In this manner the start up charge is obtained up to the threshold value in less time and while wasting less energy than the prior system. Once the threshold voltage is reached, the comparator  12  disables the pulse generator  13  and enables the controller  11  which assumes control of the remaining charging requirement. 
     An example of a charging cycle using the start up charger of this invention is shown in the graph of FIG.  4   a . The voltages indicated are relative to a 6 volt system and for illustration only as they will vary considerably depending on the specifications for the cellular phone and the associated battery pack. A typical voltage profile for the start up capacitor  14  is shown in FIG.  4   b  related to the pulsed actuation of charger  9  shown in FIG.  4   a.    
     The embodiment described above may be varied to accomplish the desired result without deviating from the invention as described in the claims below.

Technology Category: 5