System and method for dynamic USB power source

• US 20060095641A1
• Filed: 11/01/2004
• Published: 05/04/2006
• Est. Priority Date: 11/01/2004
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Bohl, Robert, Pandit, Amol, Byrne, Dan
• Granted Patent: US 7,310,697 B2
• Time in Patent Office: Days
• US Class Current: 710/313
• CPC Class Codes: G06F 1/266 Arrangements to supply power to external peripherals either directly from the computer or under computer control, e.g. supply of power through the communication port, computer controlled power-strips

Abstract

The dynamic VBUS power source provides a system and method for dynamically powering USB devices. Briefly described, one embodiment is a method comprising determining when the USB device is a master device or a slave device, powering the USB device over a USB connector using a power unit when the USB device is the slave device, and powering a second USB device over the USB connector using the USB device when the USB device is the master device.

Claims

1. A system that powers a universal serial bus (USB) device, comprising:

a power unit;

a first switch coupled between the power unit and a first USB device;

a second switch coupled between a second USB device and the first USB device; and

a switch control unit configured to close the first switch and open the second switch when the first USB device is a slave device configured to receive power via a USB connection, such that the first USB device is powered by the power unit.

2. The system of claim 1, wherein the switch control unit is further configured to open the first switch and close the second switch when the first USB device is a master device configured to provide power via the USB connection, such that the first USB device provides power to the second USB device.

3. The system of claim 1, further comprising a VBUS connector coupled to the switch control unit, the first USB device and the second USB device, and wherein the switch control unit is further configured to detect a signal on the VBUS connector to determine that the first USB device is a master device.

4. The system of claim 1, further comprising a USB identifier (ID) connector coupled to the switch control unit, the first USB device and the second USB device, and wherein the switch control unit is further configured to detect a signal on the USB ID connector to determine that the first USB device is a master device.

5. The system of claim 1, further comprising:

a USB identifier (ID) connector coupled to the switch control unit, the first USB device and the second USB device;

a NOT logical gate residing in the switch control unit and having an input coupled to the USB ID connector such that a logical low signal on the USB ID connector is converted to a logical high signal on an output of the NOT logical gate;

a VBUS connector coupled to the switch control unit, the first USB device and the second USB device; and

an AND logical gate residing in the switch control unit and having a first input coupled to the VBUS connector and a second input coupled to the output of the NOT logical gate, such that when a logical high signal is present on both the VBUS connector and the output of the NOT logical gate the first switch is closed and the second switch is opened.

6. The system of claim 5, further configured such that when the logical low signal is present on one of the VBUS connector or the output of the NOT logical gate, the first switch is opened and the second switch is closed.

7. The system of claim 5, wherein the second switch is coupled to the USB ID connector such that when the logical high signal is present on the USB ID connector the second switch is closed, and such that when the logical low signal is present on the USB ID connector the second switch is opened.

8. The system of claim 1, wherein the power unit further comprises:

a wall adapter configured to receive alternating current (AC) power from an electric distribution system and is configured to convert the received AC power into direct current (DC) power; and

a converter coupled to the wall adapter and configured to convert the received DC power into power suitable for a USB connector.

9. The system of claim 1, further comprising a VBUS connector coupled between the power unit, the first USB device and the second USB device.

10. A method for powering a universal serial bus (USB) device, comprising:

determining when the USB device is a master device or a slave device;

powering the USB device over a USB connector using a power unit when the USB device is a slave device; and

powering a second USB device over the USB connector using the USB device when the USB device is the master device.

11. The method of claim 10, further comprising:

closing a first switch when the USB device is the slave device such that the USB device is powered from the power unit coupled to the first switch; and

opening a second switch when the USB device is the slave device such that the second USB device is isolated from the USB device.

12. The method of claim 10, further comprising:

opening a first switch when the USB device is the master device such that the power unit coupled to the first switch is isolated from the USB connector; and

closing a second switch when the USB device is the master device such that the second USB device is powered by the USB device.

13. The method of claim 10, further comprising:

detecting a logical low on a USB identifier (ID) connector; and

detecting a logical high on a VBUS connector, such that the USB device is powered over the USB ID connector using the power unit.

14. The method of claim 13, further comprising:

inverting the logical low on the USB ID connector to a second logical high;

outputting a third logical high when the USB ID is inverted to the second logical high and when the logical high on the VBUS connector is detected; and

closing a first switch when the third logical high is output such that the USB device is powered from the power unit coupled to the first switch.

15. The method of claim 14, further comprising opening a second switch when the logical low on the USB ID connector is detected such that the second USB device is isolated from the power unit.

16. The method of claim 10, further comprising detecting a logical high on a USB identifier (ID) connector such that the second USB device is powered by the USB device.

17. The method of claim 10, further comprising detecting a logical low on a VBUS connector such that the second USB device is powered by the USB device.

18. The method of claim 10, further comprising:

receiving alternating current (AC) power from an electric distribution system; and

converting the received AC power into direct current (DC) power suitable for the USB connector.

19. A system for powering a universal serial bus (USB) device, comprising:

means for determining when the USB device is a master device or a slave device;

means for receiving alternating current (AC) power from an electric distribution system and converting the received AC power into direct current (DC) power suitable for a USB connector;

means for powering the USB device over the USB connector using the means for receiving and converting power when the USB device is the slave device; and

means for powering a second USB device over the USB connector using the USB device when the USB device is the master device.

20. The system of claim 19, further comprising:

means for closing a first switch when the USB device is the slave device such that the USB device is powered using the means for receiving and converting power, the means for receiving and converting power coupled to the first switch; and

means for opening a second switch when the USB device is the slave device such that the second USB device is isolated from a power unit.

21. The system of claim 19, further comprising:

means for opening a first switch when the USB device is the master device such that the means for receiving and converting power coupled to the first switch is isolated from the USB connector; and

means for closing a second switch when the USB device is the master device such that the second USB device is powered by the USB device.

22. The system of claim 19, further comprising:

means for detecting a logical low on a USB identifier (ID) connector; and

means for detecting a logical high on a VBUS connector, such that the USB device is powered over the USB connector using the means for receiving and converting power.

23. The system of claim 22, further comprising:

means for inverting the logical low on the USB ID connector to a second logical high;

means for outputting a third logical high when the USB ID is inverted to the second logical high and when the logical high on the VBUS connector is detected; and

means for closing a first switch when the third logical high is output such that the USB device is powered from the means for receiving and converting power coupled to the first switch.

24. The system of claim 23, further comprising means for opening a second switch when the logical low on the USB ID connector is detected such that the second USB device is isolated from the means for receiving and converting power.

25. A program for powering a universal serial bus (USB) device stored on computer-readable medium, the program comprising logic configured to perform:

determining when the USB device is a master device or a slave device;

closing a first switch when the USB device is the slave device such that the USB device is powered from a power unit coupled to the first switch; and

opening a second switch when the USB device is the slave device such that a second USB device is isolated from the USB device.

26. The program of claim 25, further comprising logic configured to perform:

opening the first switch when the USB device is the master device such that the power unit coupled to the first switch is isolated from a USB connector; and

closing the second switch when the USB device is the master device such that the second USB device is powered by the USB device.