Backup power supply

• US 7,157,810 B2
• Filed: 01/12/2004
• Issued: 01/02/2007
• Est. Priority Date: 06/06/2001
• Status: Expired due to Fees

• Current Assignee: Hitachi Information & Telecommunication Engineering, Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Computer Peripherals Company Limited (Hitachi, Ltd.), Hitachi, Ltd., Hitachi Maxell Limited (Maxell, Ltd.)
• Inventors: Kanouda, Akihiko, Isogai, Masato, Onda, Kenichi, Saga, Ryouhei, Masuyama, Satoru, Tokunaga, Norikazu
• Primary Examiner(s): Deberadinis; Robert L.
• Application Number:
  US10/754,692
• Publication Number:
  US 20040145926A1
• Time in Patent Office: 1,086 Days
• Field of Search: 307/66
• US Class Current: 307/66
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

The present invention reduces the capacity of the AC-DC converter for the peak load and realizes low price and reduction in the volume of the power unit. The apparatus built-in backup power supply has the peak cut function for sharing a part of the load current at the time of peak load from the secondary battery. The two-way DC-DC converter 5 and the secondary battery 4 are installed on the DC output side of the AC-DC converter 3 and a current larger than a predetermined peak cut level is discharged from the secondary battery 4 at the time of peak load. Further, when the load is less than the predetermined cut level, the secondary battery 4 is charged from the AC-DC converter 3 via the two-way DC-DC converter 5. Furthermore, a most suitable peak cut level according to the SOC of the secondary battery and load pattern is automatically set and dynamically changed.

Claims

1. A backup power supply built in a power supply circuit for converting an alternating current received from a commercial AC power supply to a direct current and a load operated by said current generated by said power supply circuit, comprising:

at least one AC-DC converter connected to said commercial alternating current, a load connected to a DC output side of said AC-DC converter, at least one two-way DC-DC converter with one side thereof connected to said DC output side, and a secondary battery connected to another side of said two-way DC-DC converter, wherein;

when a load current is a predetermined peak cut current or larger, said backup power supply supplies a differential current between said load current and said predetermined peak cut current to said load from said secondary battery via said two-way DC-DC converter and performs a peak cut operation and when said load current is smaller than said predetermined peak cut current, said backup power supply supplies said load current from said AC-DC converter and charges said secondary battery via said two-way DC-DC converter.

2. A backup power supply according to claim 1,

wherein said charging current for charging said secondary battery has an upper limit of a predetermined current and said backup power supply takes in only a current equivalent to a differential current between said predetermined peak cut current and said load current from said two-way DC-DC converter and charges said secondary battery.

4. A backup power supply according to claim 1, wherein

when said load current is smaller than said predetermined peak cut current, said backup power supply supplies said load current from said AC-DC converter, charges said secondary battery using said two-way DC-DC converter by a charging current having an upper limit of a predetermined current, takes in only a current equivalent to a differential current between said predetermined peak cut current and said load current from said two-way DC-DC converter.

5. A backup power supply according to claims 3 or 1, wherein

said backup power supply has detection means for detecting said charging and discharging currents of said secondary battery, means for detecting a voltage of said secondary battery, and a circuit for calculating a residual capacity of said secondary battery and changes said predetermined peak cut current according to said residual capacity of said secondary battery.

6. A backup power supply according to claim 5, wherein

when said residual capacity of said secondary battery is reduced lower than a predetermined capacity, said peak cut operation is stopped.

7. A backup power supply according to claim 5, wherein

when said residual capacity of said secondary battery is reduced lower than said predetermined capacity at a time of service interruption or at a time of occurrence of a fault of said AC-DC converter, a discharge operation is performed.

8. A backup power supply according to any one of claims 3 to 1, wherein

from said residual capacity of said secondary battery and said load current, said backup power supply has a function for calculating and displaying a service interruption holding time at said point of time.

9. A backup power supply according to any one of claims 3 to 1, wherein

from said residual capacity of said secondary battery and said load current, said backup power supply calculates said residual capacity of said secondary battery necessary to ensure a predetermined service interruption holding time at said point of time and performs said peak cut operation within a range having said calculated residual capacity.

10. A backup power supply according to any one of claims 3 to 1, wherein a voltage at a connection point of said AC-DC converter and said two-way DC-DC converter is higher than a voltage of said secondary battery, and when said two-way DC-DC converter is discharged from a side of said secondary battery, said converter is operated as a booster chopper circuit, and when said secondary battery is charged, said converter is operated as a voltage reduction chopper circuit.

11. A backup power supply according to any one of claims 3 to 1, wherein

said backup power supply has n storage means for dividing a preset time period into n parts by a sampling time sufficiently shorter than said period and corresponding to said divisions, means for detecting said load current, and means for calculating a mean value of load currents from said detected load current and a last value stored in corresponding storage means, overwriting in said corresponding means, and changing said predetermined peak cut current from said calculated new mean value of load currents.

12. A backup power supply according to claim 11, wherein

said preset time period is 24 hours.

13. A backup power supply according to claim 11, wherein

said preset time period is one week.

3. A backup power supply built in a power supply circuit for converting an alternating current received from a commercial AC power supply to a direct current and a load operated by said current generated by said power supply circuit, comprising:

at least one AC-DC converter connected to said commercial alternating current, a load connected to a DC output side of said AC-DC converter, at least one two-way DC-DC converter with one side thereof connected to said DC output side, and a secondary battery connected to another side of said two-way DC-DC converter, wherein;

when a load current is a predetermined peak cut current or larger, said backup power supply supplies a differential current between said load current and said predetermined peak cut current to said load from said secondary battery via said two-way DC-DC converter.

14. A backup power supply comprising an AC-DC converter connected to a commercial alternating current, a load connected to a DC output side of said AC-DC converter, a DC-DC converter with one side thereof connected to said DC output side, and a secondary battery connected to one side of said DC-DC converter, wherein

said DC-DC converter has means for alternately switching a short-circuit mode for short-circuiting said secondary battery and an inductance by a switching element and a booster mode for ejecting energy stored in said inductance in said short-circuit mode to said load, means for detecting an inductance current in said booster mode, and mean for averaging said inductance current in said booster mode, and only when a result obtained by subtracting a predetermined peak cut current level from said load current is positive, sets said value as a peak cut current command value, compares said value with said averaged current, and controls a ratio of said short-circuit mode to said booster mode.

15. A backup power supply built in a power supply circuit for converting an alternating current received from a commercial AC power supply to a direct current and a load operated by said current generated by said power supply circuit, comprising:

at least one AC-DC converter connected to said commercial alternating current, a load connected to a DC output side of said AC-DC converter, at least one two-way DC-DC converter with one side thereof connected to said DC output side, a secondary battery connected to another side of said two-way DC-DC converter, a service interruption fault detection circuit portion connected to said commercial alternating current, a two-way operation mode change-over circuit portion, a drive signal change-over means for changing over a drive signal of said two-way DC-DC converter by receiving a signal which is output by said two-way operation mode change-over circuit, a discharge control circuit portion for outputting a discharge control signal to said two-way DC-DC converter through a drive signal change-over means, and a SOC calculation portion for calculating a residual capacity of said secondary battery, wherein

an output of said SOC calculation portion is received by said charge control circuit portion.