Automatic system battery reconnect circuit responsive to insertion of new battery replacement

• US 5,206,538 A
• Filed: 04/03/1991
• Issued: 04/27/1993
• Est. Priority Date: 04/03/1991
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Orta, Conrad
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): Krishnan, Aditya
• Application Number:
  US07/680,177
• Time in Patent Office: 755 Days
• Field of Search: 361/66, 361/87, 361/64
• US Class Current: 307/66
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

A battery reconnect scheme is provided to permit battery replacement in a power reserve system without requiring the manual switching of the battery terminals into and out of the circuitry. A battery reconnect circuit is provided to perform the functions normally performed manually during the replacement of a discharged battery with a fresh battery. These functions also include checking the operability of circuitry to be powered by the newly inserted battery.

Claims

1. A power system for energizing a load network, comprising:

power circuitry for connecting a source of primary power to the load network;

backup circuitry including a reserve input for accepting a reserve voltage source and coupling it to the load network upon failure of the primary power source; and

including disconnect circuitry for disconnecting the reserve voltage source from the load network when it becomes discharged below a threshold voltage;

circuitry for enabling connection of the reserve input to the load network in response to replacement of the reserve voltage source with a substitute reserve voltage source, and including;

a first semiconductor switch for enabling coupling of the reserve input to the load network,

a second semiconductor switch responsive to the operativeness of the primary power source for disabling the first semiconductor switch and responsive to the failure of primary power to allow a voltage of the reserve input to bias the first semiconductor switch into conduction, and timing circuitry operative for disabling the first semiconductor switch after an interval of conduction connecting the reserve input to the load network.

2. A power system for energizing a load network, as claimed in claim 1, comprising:

the timing circuitry including a capacitor connected to be charged through a resistor,

a third semiconductor switch connected to discharge the capacitor in response to accumulated voltage of the capacitor, and removal of the reserve voltage source from the reserve input, and

a breakdown diode connected to PROTECT the third semiconductor switch from an overvoltage.

3. A power system for energizing a load network, as claimed in claim 1, comprising:

the circuit for enabling connection having a very high input impedance to limit current drain of the reserve voltage source connected to the reserve input.

4. A power system for energizing a load network, comprising:

a DC/DC power converter energized by a primary voltage source, and connected to supply energy to the load network;

a reserve input for accepting a reserve battery voltage source;

a battery charger connected to be energized by the DC/DC power converter and connected to supply charging current to the reserve input;

a primary power monitor for monitoring the voltage of the primary voltage source;

a battery condition monitor to monitor the voltage of the battery voltage source connected to the reserve input;

a first power switch for connecting the reserve input to the load network in response to the primary power monitor detecting a falling of the voltage level of the primary voltage source below a first threshold value;

a second power switch for disconnecting the reserve input from the load network in response to the voltage of the battery voltage source falling below a second threshold value;

a battery reconnect circuit for connecting the reserve input to the load network in response to replacing the battery voltage source with a replacement battery voltage source, including;

an FET switch coupling the reserve input to the load network;

bias circuitry for enabling conduction in the FET switch in response to the replacing of the battery voltage source with a replacement battery voltage source having;

a transistor switch responsive to the primary power monitor operative for enabling the FET switch by allowing a bias voltage supplied by the replacement battery voltage source to appear across a gate-source junction of the FET switch;

a timing circuit including a timing capacitor and connected to charge in response to the replacement battery voltage source and bias the FET switch non-conducting after a time interval, and

a second FET switch for discharging the timing capacitor when a battery voltage source is removed from the reserve input.

5. A power system for energizing a load network, as claimed in claim 4, comprising:

a light emitting diode in the primary power monitor; and

the transistor switch being a photo transistor responsive to the light emitting diode.

6. A power system for energizing a load network, as claimed in claim 4, comprising:

the battery reconnect circuit including a high impedance input including high valued resistors connected to a lead connected to the reserve input.

7. A power system for energizing a load network, comprising:

a DC/DC power converter for connecting a source of primary power to the load network;

backup circuitry including a reserve input for accepting a reserve voltage source and coupling it to the load network upon failure of the primary power source; and

including disconnect circuitry for disconnecting the reserve voltage source from the load network when it becomes discharged below a threshold voltage;

circuitry for enabling connection of the reserve input to the load network in response to replacement of the reserve voltage source with a substitute reserve voltage source, and including;

a high input impedance connected to limit a current drain of the reserve voltage source connected to the reserve input,

a first FET switch for enabling coupling of the reserve input to the load network,

a second FET switch responsive to the operativeness of the primary power source for disabling the first FET switch and responsive to the failure of primary power to allow a voltage of the reserve input to bias the first FET switch into conduction, and

timing circuitry operative for disabling the first FET switch after an interval of conduction connecting the reserve input to the load network, including;

a capacitor connected to be charged by the reserve voltage source through at least a resistor,

a third FET switch connected to discharge the capacitor and responsive to removal of the reserve voltage source from the reserve input, and

a breakdown diode connected to protect the third FET switch from an overvoltage.

8. A power system for energizing a load network, comprising:

a DC/DC power converter energized by a primary voltage source, and connected to supply energy to the load network;

a reserve input for accepting a reserve battery voltage source;

a battery charger connected to be energized by the DC/DC power converter and connected to supply charging current to the reserve input;

a primary power monitor for monitoring the voltage of the primary voltage source and including at least a light emitting diode connected to be responsive to current flow from the primary voltage source;

a battery condition monitor to monitor the voltage of the battery voltage source connected to the reserve input;

A first power switch for connecting the reserve input to the load network in response to the primary power monitor detecting a falling of the voltage level of the primary voltage source below a first threshold value;

a second power switch for disconnecting the reserve input from the load network in response to the voltage of the battery voltage source falling below a second threshold value;

a battery reconnect circuit for connecting the reserve input to the load network in response to replacing the battery voltage source with a replacement battery voltage source, including;

a first FET switch coupling the reserve input to the load network,

bias circuitry for enabling conduction in the first FET switch in response to the replacing of the battery voltage source with a replacement battery voltage source, having;

a photo-transistor switch responsive to the absence of light emissions of the light emitting diode of primary power monitor operative for enabling the FET switch by allowing a bias voltage supplied by the replacement battery voltage source to appear across a gate-source junction of the FET switch;

a timing circuit including a timing capacitor and a resistive impedance and connected to charge in response to the replacement battery voltage source and bias the FET switch non-conducting after a time interval, and

a second FET switch for discharging the timing capacitor when a battery voltage source is removed from the reserve input;

a breakdown diode connected to protect the second FET switch from an overvoltage and having its low resistance current path oriented to allow current from the reserve voltage source to charge the timing capacitor;

the resistive impedance connected to provide a high impedance to the reserve input and operative for limiting current drain of the reserve voltage source connected to the reserve input when the reserve input is disconnected from the load network.