Battery charger for a portable wireless telephone set having means for tricklingly charging the battery with an increased current during a stand-by period of the telephone set

• US 5,130,634 A
• Filed: 07/05/1990
• Issued: 07/14/1992
• Est. Priority Date: 07/05/1989
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kasai, Yoshihiko
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US07/548,538
• Time in Patent Office: 740 Days
• Field of Search: 320/22, 320/23, 320/24, 320/39
• US Class Current: 320/160
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/342 The other DC source being a battery actively interacting with the first one, i.e. battery to battery charging with circuits for polarity protection H02J7/0034

Abstract

A battery charger for a portable wireless telephone set comprising a rapidly charging circuit for rapidly charging the battery by a first charging current of a high level at a start of the charging operation, a tricklingly charging circuit for tricklingly charging the battery by a second charging current of a considerably low level, and a charge controller for making the tricklingly charging circuit take over the rapidly charging circuit after a charge detecting circuit detects that the battery is rapidly charged to its normal voltage. In order to avoid that the battery is insufficiently charged by the tricklingly charging circuit when the telephone set is left in a power-on condition, the battery charger further comprises another charging circuit for supplying a third charging current which is lower thn the first charging current but higher than the second charging current. When the telephone set is in the power-on condition, the charge controller operates not the tricklingly charging circuit but the other charging circuit after the battery is rapidly charged to its normal voltage, so that the battery can be charged to the normal voltage even if the telephone set is left in the power-on condition.

Claims

1. A battery charger for a portable wireless telephone set including a battery having a normal battery voltage as an electric power source for the telephone set, the portable wireless telephone set having means for generating a power-on signal when the telephone set is powered on, which comprises:

an output port to be connected to said battery for delivering a charging current to said battery;

DC power source for generating a DC power;

first charging means coupled to said DC power source and said output port responsive to a first control signal for generating from said DC power a first DC current with a first level sufficient to rapidly charge said battery, said first DC current being delivered to said output port as said charging current;

second charging means coupled to said DC power source and said output port responsive to a second control signal for generating from said DC power a second DC current with a second level considerably lower than said first DC current to tricklingly charge said battery, said second DC current being delivered to said output port as said charging current;

third charging means coupled to said DC power source and said output port responsive to a third control signal for generating from said DC power a third DC current with a third level lower than said first DC current but relatively higher than said second DC current, said third DC current being delivered to said output port as said charging current;

charge detecting means coupled to said output port for detecting a voltage charged in said battery connected to said output port to produce, as a fourth control signal, a detected signal when said charge voltage reaches said normal battery voltage;

an input terminal to be coupled with said power-on signal generating means and responsive to said power-on signal for producing a fifth control signal; and

charge controlling means coupled to said charge detecting means and said input terminal means for generating said first control signal when said fourth control signal is absent from said charge detecting means, said charge controlling means generating said third control signal in place of said first control signal in response to said fourth control signal when receiving said fifth control signal, said charge controlling means generating said second control signal in place of said first control signal in response to said fourth control signal when said fifth control signal is absent.

2. A battery charger as claimed in claim 1, the battery having a capacity C, wherein said second level of said second DC current is determined to be a value of C/25 to C/15.

3. A battery charger as claimed in claim 2, the battery supplying a stand-by current during a stand-by condition of the telephone set when said telephone set is powered on, wherein said third level of the third DC current is determined to be a sum of the value of the second level and a level of said stand-by current.

4. An apparatus comprising:

first charging means for charging a battery at a first charging current, said battery supplying power to a communication device;

second charging means for charging said battery at a second charging current lower than said first charging current;

third charging means for charging said battery at a third charging current lower than said second charging current;

AC/DC converter means for converting an AC voltage into a DC voltage and supplying said DC voltage to said first, second, and third charging means;

first detecting means for detecting the fully charged condition of said battery to produce a full charge detect signal;

second detecting means for detecting the ON/OFF condition of said communication device to produce an on-state signal when said device is turned on and an off-state signal when said device is turned off; and

control means for making said first charging means operative in the absence of said full charge detect signal, for making said first and second charging means inoperative and said third charging means operative in the presence of said full charge detect signal and of said off-state signal, and for making said first and third charging means inoperative and said second charging means operative in the presence of said full charge detect signal and of said on-state signal;

each of said first, second, and third charging means comprising;

a first resistor whose one end is coupled to said AC/DC converter means;

a PNP transistor whose emitter and collector are connected to the other end of said first resistor and said battery, respectively;

a Zener diode whose anode and cathode are connected to the base of said transistor and said one end of said first resistor, respectively;

a second resistor whose one end is connected to said base; and

and inverter whose output and input terminals are connected to the other end of said second resistor and said control means, respectively.

5. An apparatus as claimed in claim 4, wherein said communication device comprises a portable wireless telephone set.

6. An apparatus as claimed in claim 4, wherein said second detecting means comprises:

first and second resistors connected in series between said battery and ground;

a comparator whose inverting input and output terminals are connected to the junction of said first and second resistors and said control means, respectively;

a diode whose anode and cathode are connected to the inverting and non-inverting input terminals of said comparator, respectively; and

a capacitor connected between said non-inverting input terminal and ground.