Voltage level detector for battery charger control circuit

• US 4,341,988 A
• Filed: 06/25/1980
• Issued: 07/27/1982
• Est. Priority Date: 06/25/1980
• Status: Expired due to Term

• Current Assignee: Emerson Electric Company
• Original Assignee: Emhart Industries, Inc. (Stanley Black & Decker, Inc.)
• Inventors: Small, James E.
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US06/162,826
• Time in Patent Office: 762 Days
• Field of Search: 320/32, 320/39, 320/40, 320/31, 320/37, 320/38
• US Class Current: 320/158
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

A voltage level detector for controlling a battery charger, includes a power supply circuit adapted to be coupled to a battery during charging thereof, a first voltage regulator for providing a supply voltage for the detector, the first voltage regulator being coupled to receive power from the power supply circuit, a second voltage regulator for providing a stable source of reference voltage, the second voltage regulator being coupled to receive power from the detector supply voltage, a voltage comparator having one input thereof coupled to the stable reference voltage source, circuitry for coupling the battery to the other input of the voltage comparator, the circuit for coupling being adapted to coupled a proportion of the battery voltage which proportion equals the stable reference voltage when the battery voltage reaches a predetermined maximum level, and control circuitry responsive to the output of the voltage comparator for controlling the charging of the battery in response to the battery voltage reaching the maximum desired level.

Claims

1. A battery charger, comprising:

power supply circuit means adapted to be coupled to a battery during charging thereof;

first voltage regulation means for providing a supply voltage for said detector, said first voltage regulation means being coupled to receive power from said power supply circuit means and including a first zener diode;

second voltage regulation means for providing a stable source of reference voltage, said second voltage regulation means being coupled to receive power from said detector supply voltage and including a second zener diode having a very stable reverse bias voltage for providing said reference voltage source;

voltage comparator means having one input thereof coupled to said stable reference voltage source;

circuit means for coupling said battery to the other input of said voltage comparator means, said circuit means for coupling being adapted to couple a proportion of the battery voltage which proportion equals said stable reference voltage when said battery voltage reaches a predetermined level;

control circuit means responsive to the output of said voltage comparator means for controlling the charging of said battery in response to said battery voltage reaching said predetermined maximum level, said control circuit means including means for terminating the charging of said battery in response to said battery voltage reaching said predetermined maximum level;

a second voltage comparator means having an input thereof coupled to said stable reference voltage source;

second circuit means for coupling said battery voltage to the other input of said second voltage comparator means, said second circuit means for coupling being adapted to couple a proportion of said battery voltage, which proportion equals said stable reference voltage when said battery voltage reaches a secondary predetermined level which is substantially higher than said predetermined maximum level; and

second control circuit means responsive to the output of said second voltage comparator means for disabling the terminating function of first said control circuit means when said secondary voltage level is reached.

2. The detector of claim 1, wherein said circuit means for coupling includes a voltage divider circuit connected across said battery voltage and having a potentiometer for allowing adjustment of the proportion of said battery voltage coupled to said other voltage comparator means input and thereby allowing adjustment of said predetermined maximum level for said battery voltage.