Supercapacitor backup power supply with bi-directional power flow

• US 8,593,113 B2
• Filed: 03/25/2011
• Issued: 11/26/2013
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Psion Inc (Zebra Technologies Corporation)
• Original Assignee: Psion Inc (Zebra Technologies Corporation)
• Inventors: Baker, Keith, Forsythe, Larry
• Primary Examiner(s): Berhanu, Samuel
• Application Number:
  US13/072,552
• Publication Number:
  US 20110215644A1
• Time in Patent Office: 977 Days
• Field of Search: 320/166, 320/167, 323/222
• US Class Current: 320/166
• 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 backup power supply circuit comprising;

a supercapacitor for backing up a potential node;

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

a first switch connected in a first parallel circuit with a first diode, the first parallel circuit coupled between the inductor and the potential node; and

a second switch connected in a second parallel circuit with a second diode, the second parallel circuit coupled between the inductor and a second terminal of the supercapacitor, the first switch being used to modulate flow of current from a power source to the supercapacitor via the inductor when the power source is available at the potential node, and the second switch being used to modulate flow of current from the supercapacitor to the potential node via the inductor when the power source is lost at the potential node.

2. The system according to claim 1, wherein the first diode is coupled in parallel to the first switch such that the first diode is reverse biased when the power source is available at the potential node and forward biased when the power source is lost at the potential node.

3. The system according to claim 1, wherein the first diode is coupled in parallel to the first switch such that the first diode is forward biased when the power source is available at the potential node and reverse biased when the power source is lost at the potential node.

4. The system according to claim 1, wherein the first diode is an intrinsic diode of the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).

5. The system according to claim 1, wherein the first diode is a schottky diode.

6. The system according to claim 1, wherein the second diode is coupled in parallel to the second switch such that the second diode is reverse biased when the power source is available at the potential node and forward biased when the power source is lost at the potential node.

7. The system according to claim 1, wherein the second diode is an intrinsic diode of the MOSFET.

8. The system according to claim 1, wherein the second diode is a schottky diode.

9. The system according to claim 1, wherein at least one of the first switch and the second switch is a MOSFET.

10. The system according to claim 1, the backup power supply circuit further comprising a controller for operating the first switch and the second switch.

11. The system according to claim 10, wherein the controller comprises a charging mode for charging the supercapacitor using the first switch, and a backup mode for discharging the supercapacitor using the second switch.

12. The system according to claim 10, wherein the controller comprises a current monitor for monitoring the inductor current.

13. The system according to claim 10, wherein the controller comprises a voltage monitor for monitoring the voltage level at the potential node.

14. The system according to claim 10, wherein the controller operates the first switch and the second switch to form a buck converter with a synchronous rectifier.

15. The system according to claim 10, wherein the controller operates the first switch and the second switch to form a boost converter with a synchronous rectifier.