DC power supply and battery charge system

• US 6,597,075 B1
• Filed: 07/10/2001
• Issued: 07/22/2003
• Est. Priority Date: 09/29/2000
• Status: Expired due to Fees

• Current Assignee: Sprint Communications Company LP (Deutsche Telekom AG)
• Original Assignee: Sprint Communications Company LP (Deutsche Telekom AG)
• Inventors: Goodrich, Earl II
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/902,524
• Time in Patent Office: 742 Days
• Field of Search: 320/150, 320/152, 320/153, 370/546, 379/110.01, 307/66, 307/64, 713/340, 713/300
• US Class Current: 307/66
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop

Abstract

A power supply for providing full time electrical power to a customer premises telecommunications hub. The supply includes an AC to DC power converter for converting power from the AC power grid to a DC voltage selected to maintain a backup battery at float voltage. The converter includes a first rectifier section for generating an unregulated DC voltage. This voltage is switched through the primary of an isolation transformer by a pulse width modulated voltage controller. The output of the transformer is connected to a second rectifier circuit and filter to produce a regulated DC output voltage. The regulated voltage is connected to a voltage correction circuit through a divider including a temperature compensator so that the feedback to the voltage controller causes the regulated output voltage to follow the battery float voltage at all temperatures. The unregulated DC voltage is coupled to the voltage controller current limiting input to protect the power supply at high input voltages.

Claims

1. A power supply comprising:

a first AC power converter having an input for connection to an AC power grid and at least one rectifier for producing a first DC voltage at its output;

an isolation transformer having a primary winding connected to said first DC voltage and having a secondary winding;

a second AC power converter having an input connected to the secondary winding and at least one rectifier for providing a second DC voltage at an output;

a voltage controller having a voltage control input,

a battery connected to the output of said second AC power converter,

a temperature sensing device located near the battery, and

a low power voltage comparator having an input connected to the output of said second AC power converter through a voltage divider including the temperature sensing device and having an output coupled to the voltage controller voltage control input,

said battery and the output of said second AC power converter connected to a DC power bus in a backplane in a customer premises telecommunications hub.

2. A power supply according to claim 1 wherein:

said voltage controller further comprises a current switching output connected to the isolation transformer primary winding, and a current limiting input for receiving a signal to limit current through said primary winding to safe levels.

3. A power supply according to claim 2 further comprising:

a current sensing circuit connected to said voltage controller current limiting input, including a resistor connected to said first DC voltage.

4. A power supply according to claim 3 wherein:

said current sensing circuit further comprises means for sensing current through said isolation transformer primary winding.

5. A power supply for a customer premises telecommunications hub comprising:

an AC to DC power converter having an input for receiving AC power from a commercial power grid and an output connected to a DC power bus of the telecommunications hub and including a voltage controller having a voltage control input;

a sealed lead acid battery connected to the DC power bus;

a temperature sensing device located near the battery; and

a low power voltage comparator having an input connected to the DC power bus through a voltage divider including the temperature sensing device and having an output coupled to the voltage controller voltage control input.

6. A power supply according to claim 5 wherein:

the voltage on said DC power bus is controlled at the float voltage of said battery.

7. A power supply according to claim 5 wherein:

the voltage on said DC power bus changes with temperature at the rate of about minus three millivolts per cell per degree centigrade.

8. A power supply according to claim 5 wherein:

said voltage comparator and said voltage divider have an overall accuracy of less than about one percent.

9. A power supply for a customer premises telecommunications hub comprising:

an AC to DC power converter having an input for receiving AC power from a commercial power grid and an output connected to a DC power bus of the telecommunications hub and including a voltage controller having a voltage control input;

a battery connected to the DC power bus;

a temperature sensing device located near the battery;

a low power voltage comparator having an input connected to the DC power bus through a voltage divider including the temperature sensing device and having an output coupled to the voltage controller voltage control input; and

a low voltage shutdown circuit having an input connected to said DC power bus and an output for providing a signal indicating that the battery voltage has dropped below a preselected level.

10. A power supply according to claim 9 wherein:

said preselected level is a level below which permanent damage to said battery is likely to occur.

11. A power supply comprising:

a first AC power converter having an input for connection to an AC power grid and at least one rectifier for producing a first DC voltage at its output;

an isolation transformer having a primary winding connected to said first DC voltage and having a secondary winding;

a pulse width modulated voltage controller connected to the isolation transformer primary winding having a current limiting input to limit current through said primary winding to safe levels;

a current sensing circuit connected to said voltage controller current limiting input, including a resistor connected to said first DC voltage;

a second AC power converter having an input connected to the secondary winding and at least one rectifier for providing a second DC voltage at an output;

a battery connected to the output of said second AC power converter;

a temperature sensing device located near the battery, and

a low power voltage comparator having an input connected to the output of said second AC power converter through a voltage divider including the temperature sensing device and having an output coupled to a voltage control input of said voltage controller,

said battery and the output of said second AC power converter connected to a DC power bus in a backplane in a customer premises telecommunications hub.

12. A power supply according to claim 11 wherein;

said current sensing circuit further comprises means for sensing current through said isolation transformer primary winding.

13. A power supply according to claim 11 wherein;

said battery is a sealed lead acid battery.

14. A power supply according to claim 13 wherein:

said second DC voltage is controlled at the float voltage of said battery.

15. A power supply according to claim 13 wherein:

said second DC voltage changes with temperature at the rate of about minus three millivolts per cell per degree centigrade.

16. A power supply according to claim 11 wherein;

said voltage comparator and said voltage divider have an overall accuracy of less than about one percent.

17. A power supply according to claim 11 further comprising;

a low voltage shutdown circuit having an input connected to said battery and an output for providing a signal indicating that the battery voltage has dropped below a preselected level.

18. A power supply according to claim 17 wherein:

the output of said low voltage shutdown circuit is connected to said backplane, whereby circuitry comprising said customer premises telecommunications hub connected to said backplane may be shut down to prevent over discharge of said battery.

19. A power supply according to claim 17 wherein:

said preselected level is a level below which permanent damage to said battery is likely to occur.

20. A power supply according to claim 11 wherein;

said first AC power converter input is adapted for connection to an AC power grid having a voltage of from about 90 to about 275 volts and a frequency of from about 40 to about 440 Hertz.