CURRENT AND VOLTAGE CONTROLLED BATTERY CHARGER

• US 3,758,839 A
• Filed: 10/04/1971
• Issued: 09/11/1973
• Est. Priority Date: 10/04/1971
• Status: Expired due to Term

• Current Assignee: Lewis A. Medlar
• Original Assignee: Lewis A. Medlar
• Inventors: Medlar, Lewis A.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/186,354
• Time in Patent Office: 708 Days
• Field of Search: 320/39,40,32,33,23
• US Class Current: 320/143
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

Battery charging method and apparatus for performing the method including a controlled rectifier and a trigger circuit in which a current transformer senses charging current, a voltage divider senses battery terminal voltage, and signals developed from both of the current and voltage sensing devices are used to control the operation of the trigger circuit. Current control is maintained during initial portion of the charging cycle with voltage control being substituted to diminish charging current after which a second current control maintains a closely controlled '"'"''"'"''"'"''"'"'trickle'"'"''"'"''"'"''"'"' charge level. The three control modes operate sequentially, all use the same common reference value and all control the same charging circuit valve. A second embodiment of the apparatus uses two controlled rectifiers, fired alternately.

Claims

1. A battery charging apparatus comprising the combination of first and second connector means connectable to the positive and negative terminals of a battery to be charged for conducting charging current to the battery;

a source of AC power including a power transformer having a secondary winding with a center tap and two end terminals;

a full wave rectifier;

circuit means for connecting said source of AC power to said full wave rectifier;

said circuit means including first and second conductors, one end of each conductor being connected to one end terminal of said secondary winding and the other end being connected to said rectifier;

a semiconductor switching device connected to one of said connector means and to said AC source, said switch means having a control electrode and a switchable conductive path connected in series with the battery when the battery is connected to said connectors for controllably providing charging current to said battery;

a current transformer having a magnetically permeable core inductively coupled to said circuit means, said current transformer having a secondary winding for providing a current representative of the magnitude of charging current in said circuit means, said first and second conductors being magnetically coupled to said core to constitute a primary winding, said conductors being coupled to said core in directions to produce a magnetomotive force suitable to provide in said secondary winding a reconstructed AC signal when the currents in said conductors are pulsating and unidirectional and separated in phase by 180*; and

control circuit means connected to said secondary winding, to said first and second connector means and to said control electrode of said switching device for providing control signals to said switching device in response to terminal voltage of, and charging current to, the battery.

2. Apparatus according to claim 1 wherein said control circuit means comprises rectifier circuit means connected to said secondary winding of said current transformer for providing a rectified signal proportional in magnitude to the charging current flowing through said first and second conductors;

a voltage divider connected to said connector means in parallel circuit relationship with the battery being charged; and

semiconductor circuit means connected to said rectifier circuit means and to an intermediate point on said voltage divider for providing a control current related to battery terminal voltage and to charging current; and

gate circuit means responsive to said control current for providing spaced energizing signals to the control electrode of said semiconductor switching device.

3. A battery charging apparatus comprising the combination of first and second connector means connectable to the positive and negative terminals of a battery to be charged for conducting charging current to the battery;

a source of AC power;

a full wave rectifier;

circuit means for connecting said source of AC power to said full wave rectifier, said circuit means connecting said source of AC power to said full wave rectifier carries charging current to the battery and is coupled to said current transformer as a primary winding;

a semiconductor switching device connected to one of said connector means to said AC source, said switch means having a control electrode and a switchable conductive path connected in series with the battery when the battery is connected to said connectors for controllably providing charging current to said battery;

a current transformer inductively coupled to said circuit means, said current transformer having a secondary winding for providing a current proportional in magnitude of charging current in said circuit means; and

control circuit means connected to said secondary winding, to said first and second connector means and to said control electrode of said switching device for providing control signals to said switching device in response to terminal voltage of, and charging current to, the battery, said control circuit means including means connected to said secondary winding for producing a unidirectional signal having a magnitude representative of the magnitude of the charging current, means connected to said connector means for producing a unidirectional signal representative of battery terminal voltage, means for producing a control current having a magnitude representative of the charging current when battery terminal voltage is less than a preselected value; and

timing circuit means responsive to said control current for providing activating signals to said control electrode of said semiconductor switching device;

said timing circuit means comprising a unijunction transistor, a capacitor connected between the emitter electrode and one base electrode, and a resistor connected between said Emitter electrode and said means for producing a control current, said resistor, capacitor and transistor forming a relaxation timing circuit.

4. A battery charging apparatus comprising the combination of a source of AC power, rectifier means for controlling the flow of pulsating unidirectional current;

connector means connectable to a battery to be charged for placing the battery in circuit relationship with said rectifier means;

conductor means for interconnecting said AC source, said connector means and said rectifier means in series circuit relationship;

a current transformer inductively coupled to said conductor means for developing an electrical signal representative of the maginitude of current flowing in said conductor means;

divider circuit means connected to said connector means for developing a signal representative of battery terminal voltage; and

control circuit means connected to said current transformer, to said divider circuit means and to said rectifier means for providing spaced trigger pulses to said rectifier means in response to said electrical signals representative of current and battery terminal voltage to provide limited high charging current to said battery until the terminal voltage thereof reaches a preselected level, to provide an interval of controlled voltage charging current, and to provide a low charging current thereafter.

5. Apparatus according to claim 4 wherein said rectifier means comprises at least one thyristor connected in series circuit relationship with said AC source and said battery;

and said control circuit means comprises a trigger circuit for providing activating pulses to said at least one thyristor.

6. Apparatus according to claim 4 wherein said control circuit means comprises a Zener diode connected to said connector means to provide a reference voltage;

first transistor circuit means connected to said diode and to said divider circuit means for comparing battery terminal voltage with said reference and for developing said signal representative thereof; and

second transistor circuit means connected to said first transistor circuit means and to said current transformer for developing a signal related to charging current;

said first transistor circuit means being effective to inhibit operation of said second transistor circuit means when said battery terminal voltage reaches a preselected level.

7. Apparatus according to claim 6 wherein said rectifier means comprises at least one thyristor connected in series circuit relationship with said AC source and said battery;

and said control circuit means comprises a trigger circuit for providing activating pulses to said at least one thyristor.