Two step solid state battery charger

• US 4,031,450 A
• Filed: 03/26/1971
• Issued: 06/21/1977
• Est. Priority Date: 03/26/1971
• Status: Expired due to Term

• Current Assignee: Gates Rubber Company (Gates Industrial Corp. Plc)
• Original Assignee: Gates Rubber Company (Gates Industrial Corp. Plc)
• Inventors: Fischer, William A., Hammel, Ronald O., Kuykendall, Charles N.
• Primary Examiner(s): Hickey, Robert J.
• Application Number:
  US05/128,430
• Time in Patent Office: 2,279 Days
• Field of Search: 320/36, 320/14, 320/20, 320/39, 320/40, 320/35, 320/23, 320/DIG. 2
• US Class Current: 320/153
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y10S 320/22 Line impedance, e.g. resistor

Abstract

Electronic circuitry for charging batteries is designed to charge the cells at a relatively high charging rate through a charging path which includes a semiconductor switching means, e.g. a transistor. Control circuitry is provided including a shunting controlled rectifier which is triggered into conduction when the battery has reached its nearly fully charged condition, thus shunting current away from the battery and preferably latching the transistor into non-conduction. A lower rate, trickle maintenance charge is provided by way of a resistor shunt across the switching means. The effect of temperature on the shunt controlled rectifier gating requirements is used in a positive manner to automatically latch the transistor into non-conduction as the cell approaches its fully charged condition while simultaneously preventing overcharging by tapering the battery voltage to a suitable level.

Claims

1. Charging means for delivering current to a battery comprising:

a. a power source connected to first and second charging terminals;

b. a charging path including a semiconductor switching means connected between said first charging terminal and one side of said battery, said switching means having a control terminal;

c. a shunt path between said first and second charging terminals including a resistor in series with a controlled rectifier having a gate electrode, a cathode connected to said second charging terminal, and an anode connected to said resistor and forming a juncture therebetween, said juncture connected to said control terminal of said switching means;

d. a voltage divider connected across said battery, said gate electrode connected to said voltage divider at a pre-selected dividing point;

e. said second charging terminal connected to the other side of said battery;

f. whereupon charging, current is supplied to the battery through the charging path, and when the battery reaches its pre-selected end of the charge voltage, sufficient potential is impressed across the gate-cathode junction to the controlled rectifier to render it conductive and thereby shunt current away from the battery;

g. said controlled rectifier provided with means other than or in addition to self-heating for increasing its temperature during conduction to lower the gate-cathode potential required to render the controlled rectifier conductive, and thereby latching said switching means into non-conduction and reducing the battery voltage to a safe limit to prevent overcharging.

2. The charging means of claim 1 wherein the signal supplied by the power source is rectified to supply direct current.

3. The charging means of claim 1 wherein a current limiting resistor is connected between said first charging terminal and said switching means.

4. The charging means of claim 1 wherein a resistor is connected between the anode of said controlled rectifier and said juncture.

5. The charging means of claim 1 wherein a resistor is connected in parallel across said switching means to provide a trickle charge to the battery after said switching means has been latched into non-conduction.

6. The charging means of claim 1 wherein a diode is connected between said switching means and one side of said battery in said charging path.

7. The charging means of claim 6 wherein a resistor is connected between the voltage divider and one side of said battery.

8. The charging means of claim 1 wherein said controlled rectifier is in thermal conductive relationship with said series connected resistor.

9. The charging means of claim 4 wherein said controlled rectifier exists in thermal conductive relationship with both of said series connected resistors.

10. The charging means of claim 1 wherein the controlled rectifier exists in thermal conductive relationship with the battery to be charged.

11. The charging means of claim 1 wherein said switching means consists of an NPN transistor whose base corresponds to said control terminal.

12. The charging means of claim 1 wherein said switching means is a silicon controlled rectifier.

13. The charging means of claim 1 wherein said controlled rectifier is a silicon controlled rectifier.

14. The charging means of claim 4 wherein the resistor connected between the anode of said controlled rectifier and said juncture is in thermal conductive relationship with said controlled rectifier.

15. In a method of charging a battery of one or more electrochemical cells utilizing circuitry comprising a power source provided with input terminals, a semiconductor switching means connected between the power source and battery, a shunt path connected across said power source and including a resistive element and controlled rectifier having a control terminal, and a voltage divider connected across said battery and having a juncture point connected to said control terminal, the improvement comprising:

substantially freely heating said controlled rectifier below its destruction point, commencing heating only when the battery has attained a nearly fully charged state corresponding to a given end of charge voltage exhibited by the battery, said heating of the controlled rectifier being provided by placing said resistive element in thermal conductive relationship with said controlled rectifier;

reducing the battery voltage below said end of charge voltage; and

thereafter

continuously maintaining the battery voltage level below said end of charge voltage to prevent overcharging the battery while simultaneously tapering charging current to safety bring the battery to its fully charged state.

16. In a method of charging a battery of one or more electrochemical cells utilizing circuitry comprising a power source provided with input terminals, a semiconductor switching means connected between the power source and battery, a shunt path connected across said power source and including first and second resistive elements and a controlled rectifier having a control terminal, said first and second resistive element having a juncture therebetween connected to a control terminal of said semiconductor switching means, said second resistive element being connected within the shunt path and between said controlled rectifier and the first resistive element, and a voltage divider connected across said battery and having a juncture point connected to said control terminal of the controlled rectifier, the improvement comprising:

substantially freely heating said controlled rectifier below its destruction point, commencing heating only when the battery has attained a nearly fully charged state corresponding to a given end of charge voltage exhibited by the battery, said heating of the controlled rectifier effected by placing said second resistive element in thermal conductive relationship with said controlled rectifier;

reducing the battery voltage below said end of charge voltage; and

thereafter

continuously maintaining the battery voltage level below said end of charge voltage to prevent overcharging the battery while simultaneously tapering charging current to safely bring the battery to its fully charged state.

17. In a method of charging a battery of one or more electrochemical cells utilizing circuitry comprising a power source provided with input terminals, a semiconductor switching means connected between the power source and battery, a shunt path connected across said power source and including a resistive element and controlled rectifier having a control terminal, and a voltage divider connected across said battery and having a juncture point connected to said control terminal, the improvement comprising:

substantially freely heating said controlled rectifier below its destruction point, commencing heating only when the battery has attained a nearly fully charged state corresponding to a given end of charge voltage exhibited by the battery, said heating of the controlled rectifier being effected by placing said battery in thermal conductive relationship with said controlled rectifier;

reducing the battery voltage below said end of charge voltage; and

thereafter

continuously maintaining the battery voltage level below said end of charge voltage to prevent overcharging the battery while simultaneously tapering charging current to safely bring the battery to its fully charged state.