Supercapacitor backup power supply with bi-directional power flow

• US 7,915,866 B2
• Filed: 11/13/2006
• Issued: 03/29/2011
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Psion Inc (Zebra Technologies Corporation)
• Original Assignee: Psion Teklogix (Motorola Solutions, Inc.)
• Inventors: Forsythe, Larry, Baker, Keith
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): Berhanu; Samuel
• Application Number:
  US11/598,531
• Publication Number:
  US 20080111423A1
• Time in Patent Office: 1,597 Days
• Field of Search: 320/166, 320/167, 323/222
• US Class Current: 320/167
• 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: H02J 9/061 for DC powered loads

Abstract

A system for providing backup power supply to a device is provided. The system includes a supercapacitor and a single circuit for charging and discharging of a supercapacitor. The single circuit operates with an inductor to provide for charging and discharging of the supercapacitor.

Claims

1. A system for backup power supply, the system comprising:

a supercapacitor for backing up a potential node; and

a single circuit coupled to the supercapacitor and the potential node, for charging and discharging the supercapacitor, the single circuit including;

an inductor and a first switch, coupled in series between the supercapacitor and the potential node, the inductor operating in a bi-directional mode to charge and discharge the supercapacitor;

a first diode coupled in parallel to the first switch;

a second switch having a first node coupled to the supercapacitor and a second node coupled to a node coupling the inductor and the first switch; and

a second diode coupled in parallel to the second switch,

wherein, when power source is available at the potential node, the single circuit charges the supercapacitor to a desired level by operating the first switch to modulate the power source node such that current flows from the potential to the supercapacitor through the inductor, and when the power source is lost at the potential node, the single circuit modulates the discharge of the supercapacitor by operating the second switch such that current flows from the supercapacitor to the potential node through the inductor, thereby providing backup power to the potential node.

2. The system according to claim 1, wherein at least one of the first switch and the second switch is a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).

3. The system according to claim 1, wherein at least one of the first diode and the second diode is an intrinsic diode of the MOSFET.

4. The system according to claim 1, wherein at least one of the first diode and the second diode is a schottky diode.

5. The system according to claim 1, further comprising:

a controller for operating the first switch and the second switch.

6. The system according to claim 5, wherein the controller operates the first switch and the second switch in conjunction with the inductor to form a buck converter with a synchronous rectifier.

7. The system according to claim 5, wherein the controller operates the first switch and the second switch in conjunction with the inductor to form a boost converter with a synchronous rectifier.

8. The system according to claim 5, wherein the controller and at least one of the first switch and the second switch are formed in an integrated circuit.

9. The system according to claim 1, wherein the single circuit forms a buck converter or boost converter in dependence upon whether the single circuit is in a charging mode or in a back-up mode.

10. The system according to claim 9, further comprising:

a controller for forming the buck converter or the boost converter.

11. The system according to claim 1, wherein the single circuit includes a first feedback path and a second feedback path, one of the first feedback path and the second feedback path being activated in a charging mode, the other being activated in a backup mode.

12. The system according to claim 11, further comprising:

a controller for controlling the operation of the single circuit.

13. The system according to claim 5, wherein the system has a plurality modes including a charging mode for the charging and a backup mode for the discharging, and wherein the controller monitors the voltage of the power supply, the voltage of the supercapacitor, the current of the inductor, or combinations thereof and controls the modes of the single circuit based on one or more than one result of the monitoring.

14. The system according to claim 10, wherein circuitry for the controller is located on an integrated circuit.

15. The system according to claim 14, wherein the integrated circuit has a current sense signal as an input thereto.

16. The system according to claim 5, wherein the controller has a current control mode, a voltage control mode or a combination thereof.

17. The system according to claim 1, wherein the inductor comprises a first node and a second node coupled to the supercapacitor, and wherein the first switch comprises a first node coupled to the potential node and a second node coupled to the first node of the inductor.

18. The system according to claim 1, wherein the inductor comprises a first node and a second node coupled to the potential node, and wherein the first switch comprises a first node coupled to the supercapacitor and a second node coupled to the first node of the inductor.