Charge control circuit for cordless telephone system

• US 4,992,720 A
• Filed: 01/30/1989
• Issued: 02/12/1991
• Est. Priority Date: 01/29/1988
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hata, Mamoru
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US07/302,892
• Time in Patent Office: 743 Days
• Field of Search: 320/21, 320/20, 320/39, 320/40, 320/23, 320/37, 320/38, 320/31, 320/32, 379/61
• US Class Current: 320/133
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient

Abstract

A charge control circuit is used for a cordless telephone system which includes a base unit having a quick charger and a trickling charger and a handset containing a battery. The charge control circuit comprises a connection detector, a full-charged condition detector, a timer and a controller. The connection detector detects the connection of the handset to the base unit to start the charging operation for the battery. The full-charged condition detector detects the full-charged condition of the battery. The timer has a predetermined period of time and starts it counting operation after the full-charged condition detector detects the full-charged condition of the battery. The controller controls the battery to be quickly charged with the quick charger after the timer counts up the predetermined period of time. On the other hand, the controller controls the battery to be tricklingly charged with the trickling charger until the timer counts up the predetermined period of time, so that the battery is prevented from being over-charged.

Claims

1. In a cordless telephone system including of a base unit and a handset, a charge control circuit with which a battery contained in the handset is electrically charged from a charger contained in the base unit when the handset is set to the base unit, said charge control circuit comprising:

a connection detector for detecting connection between the handset and the base unit;

a fully charged condition detector for detecting a fully charged condition of said battery;

timer means for designating a predetermined period of time in response to an output of said fully charged condition detector; and

control means responsive to the output of said or inhibit said battery from being charged within said predetermined period of time, and to quickly charge said battery after said predetermined period of time has elapsed.

2. A method of controlling charge for a cordless telephone system which includes a base unit having charging means and a handset having a battery to be electrically charged, and in which said battery is electrically charged when said handset is connected to said base unit, said method comprising the following steps of:

detecting the connection of said handset to said base unit;

detecting the fully charged condition of said battery;

determining whether or not a predetermined period of time from the time when said battery is fully charged elapses;

quickly charging said battery after the elapse of the predetermined period of time from the time when said battery is fully charged; and

subjecting said battery to trickling charge or to charge-inhibition within the predetermined period of time from the time when said battery is fully charged.

3. A cordless telephone system comprising a base unit and a handset, said base unit including a battery charger and said handset including a battery, said system further comprising:

means for detecting connection between said base unit and said handset to produce a connection detection signal;

means for detecting a full-charged state of said battery to generate a full-charged detection signal;

means for establishing a predetermined period after the generation of said full-charged detection signal; and

means for controlling the charge of said battery in response to said connection detection signal, wherein, said battery is charged with a first current after said predetermined period elapses and said battery is charged with a second current during said predetermined period said second current being smaller than said first current.

4. A cordless telephone system as claimed in claim 3, said detecting means including:

an A/D converter for converting an output voltage of said battery into digital data; and

a data processor receiving said digital data for detecting a voltage drop of a predetermined value from a maximum voltage of said battery to generate said full-charged detection signal.

5. A charge control circuit for a telephone system including a base unit and a handset, said base unit and handset communicating with each other by a radio frequency in operation, comprising:

a battery disposed in said handset, said battery being electrically charged when said handset is set to said base unit;

quick charge means for quickly charging said battery;

full-charge detector means for detecting a full-charge condition of said battery to produce a full-charge detection signal;

timer means being started in response to said full-charge detection signal for counting a predetermined period of time after said full-charge detection signal is produced; and

connection detector means for generating a detection signal when said handset is set to said base unit;

control means coupled to said timer means and said connection detection means for rendering said quick charge means operative in response to said detection signal until said full-charge detector means detects said full-charge condition and for rendering said quick charge means inoperative during said predetermined period of time.

6. A charge control circuit as claimed in claim 6, wherein said circuit further comprises trickle charge means for trickingly charging said battery, and wherein said control means renders said trickle charge means operative in response to said full-charge detect signal.

7. A charge control circuit as claimed in claim 6, wherein said control means renders said trickle charge means operative during said predetermined period of time.

8. A charge control circuit as claimed in claim 6, wherein said battery comprises a rechargeable Nickel Cadmium battery.

9. A charge control circuit as claimed in claim 6, wherein said predetermined period of time is one hour.

10. In a cordless telephone system including a base unit and a handset, a battery being contained in said handset, a charge control circuit comprising:

quick charge means for quickly charging said battery;

full-charge detector means for detecting a full-charge condition of said battery to produce a full-charge detection signal;

connection detector means for detecting a connection between said base unit and said handset to produce a connection detection signal;

timer means started in response to said full-charge detection signal for generating a timer signal after a predetermined period of time, and

control means responsive to said timer signal and to said connection detection signal for rendering said quick charge means operative until said full-charge detector means detects said full-charge condition.