US 4,145,572 AGranted

Power supply control circuit for subscriber carrier telephone system

AssigneeGTE Automatic Electric Laboratories Incorporated

InventorJames A. Stewart

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Abstract

In a carrier subscriber terminal, a voltage regulator converts the line voltage to a relatively uniform operating voltage for driving a power converter that charges a local battery. The control circuit for the converter comprises a programmable unijunction transistor (PUT) Q1 having a gate and anode connected to intermediate points of associated pairs of resistors R1-R2 and R3-R4 that are electrically connected across the line, and having a cathode connected through a first capacitor C1 and associated discharge path to one side of the line. A Zener diode D5 is resistively connected across the line to establish a reference voltage which is connected through a first diode D1 to the PUT anode, through second and third diodes D2 and D3 to the PUT gate, and through only the second diode D2 to a second capacitor C2 of the regulator. During normal operation, the diodes conduct to connect the reference voltage to the PUT gate and anode to bias the PUT off so that the second capacitor C2 is charged to the Zener-reference voltage. A constant high or increasing line voltage which is greater than a first prescribed value and a constant low or decreasing line voltage which is less than a second prescribed value cut off only the first and third diodes D1 and D3, respectively, to enable the PUT to conduct to dump the charge on the second capacitor C2 into the first capacitor C1 which discharges slowly, when the PUT is again nonconducting after C2 is discharged, to hold the converter off for a long time interval.

Claims28

Dependent claims

Apparatus for selectively disabling the carrier subscriber local battery charging circuit which operates from central office current on the pair of wires of a cable pair, comprising:

first means which is a switch means having first, second and third terminals, having a negative resistance conduction characteristic, and selectively being in an open state or a closed state between first and third terminals;
said first means switching from the open to the closed state for passing current between the first and third terminals when the voltage at the second terminal goes more negative than the voltage at the third terminal by a first prescribed amount, and switching from the closed to the open state when the voltage at the second terminal goes positive with respect to the third terminal by a second prescribed amount, which may be equal to the first prescribed amount, and the current therethrough falls below a prescribed minimum current value to bias it off;
second means, electrically connected to said cable pair for, producing a voltage across a pair of output terminals of said second means;
third means, which is a capacitive storage means, electrically connected from the first terminal of said first means to both one terminal of said second means and one wire of said pair for storing a charge voltage from said second means during the closed state of said first means;
fourth means electrically connecting said first means second and third terminals to both the other terminal of said second means and the other wire of said pair, said fourth means providing indications of both increasing and high voltages on said pair to said first means third terminal and indications of both decreasing and low voltage conditions on said pair to said first means second terminal;
said first means being responsive to indications of prescribed voltage conditions such as an increasing or constant high voltage on said cable pair which is greater than a first prescribed value for greater than a first prescribed time interval and a decreasing or constant low voltage on said cable pair which is less than a second prescribed value for greater than the first prescribed time interval, said first means under said prescribed conditions closing to pass a current therethrough from said second means to said third means for causing the latter to store a charge voltage, said first means being opened when the line voltage changes sufficiently to bias it off and the current therethrough falls below the prescribed minimum current value;
and
fifth means responsive to the charge voltage stored by said third means for holding the charging circuit inoperative for at least a second prescribed time interval.

5 more elements

Apparatus responsive to prescribed voltage conditions on the pair of wires of a cable pair such as an increasing or constant high voltage on said cable pair which is greater than a first prescribed value for greater than a first prescribed time interval and a decreasing or constant low voltage on said cable pair which is less than a second prescribed value for greater than the first prescribed time interval, for selectively-automatically rendering a carrier subscriber local battery charging circuit (which is in operation connected through said cable pair to a central office power source) inoperative for at least a second time interval which is greater than the first time interval that one of said prescribed voltage conditions is present on said pair, comprising:

programmable unijunction transistor (PUT) means having cathode, gate and anode;
voltage source means electrically connected across said cable pair and having a pair of output terminals;
capacitive storage means electrically connected from said PUT means cathode to one terminal of said source means and to one wire of said pair;
first means electrically connecting the PUT means gate and anode to the other terminal of said source means and the other wire of said pair so as to provide indications of both increasing and high voltage conditions on said pair to said PUT means anode, and indications of both decreasing and low voltage conditions on said pair to said PUT means gate;
said PUT means being responsive to indications of an increasing or constant high voltage condition on said pair which is greater than the first value for greater than the first time interval and of a decreasing or constant low voltage condition on said pair which is less than the second value for greater than the first time interval, provided by said first means which make the PUT means gate negative with respect to its anode by greater than a prescribed amount for conducting to pass a current therethrough from said source means to said storage means for producing a charge voltage on the latter, said PUT means being nonconducting when the voltage across said pair changes sufficiently to bias it off and the current therethrough falls below a minimum-valley current value;
and
second means responsive to a charge voltage on said storage means for holding said charging circuit inoperative for at least the second time interval following conduction of said PUT means.

4 more elements

Dependencies are inferred from the claim text.