Battery charger device and method

• US 5,321,347 A
• Filed: 12/18/1992
• Issued: 06/14/1994
• Est. Priority Date: 04/09/1992
• Status: Expired due to Fees

• Current Assignee: Chih-Chien Chien
• Original Assignee: Chih-Chien Chien
• Inventors: Chien, Chih-Chien
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US07/993,296
• Time in Patent Office: 543 Days
• Field of Search: 320/21, 320/39, 320/20
• US Class Current: 320/139
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y10S 320/11 Prioritized supply of power or power supply compensation

Abstract

A battery charger device is provided with a control switch which connects electrically a rechargeable battery load to a power supply which supplies charging current for charging the battery load. A pulse generator generates a series of pulses that control the control switch to connect and disconnect intermittently the power supply and the battery load. A maximum battery terminal voltage of the battery load is stored in a voltage memory means, and a fractional voltage is derived from the maximum battery terminal voltage. The fractional voltage is compared with a current battery terminal voltage from the battery load. A control signal is generated so as to prevent the control switch from receiving the pulses from the pulse generator, thereby disconnecting the power supply from the battery load so as to terminate charging of the battery load when the current battery terminal voltage is less than the fractional voltage.

Claims

1. A battery charger device for charging a rechargeable battery load, comprising:

a power supply means for supplying charging current to charge said battery load;

a control switch means for connecting electrically said power supply means and said battery load; and

a charging control unit including;

a pulse generator means for generating a series of pulses which control said control switch means to connect and disconnect intermittently said power supply means and said battery load for storing a reference battery terminal voltage of said battery load therein, said reference battery terminal voltage being a maximum battery terminal voltage measured within an operating period of said battery charger device;

a voltage divider means receiving said reference battery terminal voltage from said voltage memory means and deriving a fractional voltage from said reference battery terminal voltage; and

a comparator means for comparing said fractional voltage with a current battery terminal voltage from said battery load when said control switch means disconnects said power supply means and said battery load, said comparator means generating a control signal which prevents said control switch means from receiving said pulses form said pulse generator means, thereby disconnecting said power supply means from said battery load so as to terminate charging of said battery load when said current battery terminal voltage is less than said fractional voltage.

2. The battery charger device as claimed in claim 1, wherein said charging control unit further comprises a no-load detector means for detecting if said battery load has been connected to said battery charger device, said no-load detector means disabling said voltage memory means if said battery load is not connected to said battery charging device.

3. The battery charger device as claimed in claim 1, wherein said charging control unit further comprises an AND logic gate which receives said pulses from said pulse generator means and said control signal from said comparator means, said AND logic gate providing said pulses to said control switch means when said control signal is not present.

4. The battery charger device as claimed in claim 1, wherein said voltage memory unit comprises:

an oscillator circuit which generates a series of pulses;

a counter means which receives said pulses from said oscillator circuit and which generates an analog voltage output that corresponds to the number of said pulses received thereby; and

a second comparator means which compares said analog voltage output from said counter means with said current battery terminal voltage from said battery load, said second comparator means disabling said oscillator circuit if said analog voltage output is less than said current battery terminal voltage.

5. The battery charger device as claimed in claim 1, wherein said charging control unit further comprises a reset control means which is connected to said pulse generator means and which generates a reset signal to said voltage memory means each time said pulse generator means generates one of said pulses.

6. A battery charger device for charging a rechargeable battery load, comprising:

a power supply means for supplying charging current to charge said battery load;

a voltage-controlled current providing device which connects electrically said power supply means and said battery load; and

a charging control unit including;

a pulse generator means for generating a series of pulses which control said current providing device to connect and disconnect intermittently said power supply means and said battery load;

a voltage memory means connected to said battery load for storing a reference battery terminal voltage of said battery load therein, said reference battery terminal voltage being a maximum battery terminal voltage measured within an operating period of said battery charger device;

first and second voltage divider means which receive said reference battery terminal voltage from said voltage memory means and which respectively derive higher and lower fractional voltages from said reference battery terminal voltage;

first and second comparator means for comparing a respective one of said higher and lower fractional voltage with a current battery terminal voltage form said battery load when said control switch means disconnects said power supply means and said battery load;

a current control unit which generates an increasing analog voltage signal if said current battery terminal voltage is greater than said higher fractional voltage and a decreasing analog voltage signal if said current battery terminal voltage is less than said lower fractional voltage, said current providing device receiving said analog voltage signal from said current control unit and controlling the amount of said charging current supplied to said battery load so as to correspond with said analog voltage signal; and

a switch control unit which generates a control signal for preventing said current providing device from receiving said pulses form said pulse generator means when said analog voltage signal from said current control unit is less than a preset cut-off voltage, thereby disconnecting said power supply means from said battery load.

7. A method for charging a rechargeable battery load, comprising the steps of:

providing a control switch means for connecting electrically said battery load to a power supply means which supplies charging current for charging said battery load;

providing a pulse generator means which generates a series of pulses that control said control switch means to connect and disconnect intermittently said power supply means and said battery load;

storing a reference battery terminal voltage of said battery load in a voltage memory means, said reference battery terminal voltage being a maximum terminal voltage measured within an operating period of the method of charging;

deriving a fractional voltage form said reference battery terminal voltage;

comparing said fractional voltage with a current terminal voltage form said battery load when said control switch means disconnects said power supply and said battery load; and

generating a control signal which prevents said control switch means from receiving said pulses from said pulse generator means, thereby disconnecting said power supply means form said battery load so as to terminate charging of said battery load when said current battery terminal voltage is less than said fractional voltage.