VBUS POWER SWITCH

• US 20160164342A1
• Filed: 12/07/2015
• Published: 06/09/2016
• Est. Priority Date: 05/26/2010
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Siulinski, James A., Snowdon, Kenneth P.
• Granted Patent: US 10,389,169 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H03K 17/56 by the use, as active elements, of semiconductor devices using diodes H03K17/74

Abstract

This document discusses, among other things, an electronic circuit and method for defaulting to a valid battery supply to power an electronic device. In an example, an electronic circuit can be configured to receive information about the battery supply (e.g., an internal battery), such as the battery supply voltage (V_BAT), and to determine if the battery supply is valid or invalid using the received information (e.g., comparing the V_BAT to a threshold). If V_BAT is valid, the electronic device can default to receiving power from the battery supply. If V_BAT is invalid, the electronic device can receive power from another power supply, such as an external supply.

Claims

1. A USB switch circuit configured to receive a supply voltage, to receive a USB bus voltage, and to provide an internal device voltage for the USB switch circuit, the USB switch circuit comprising:

a comparator configured to determine if the supply voltage is valid,

wherein the USB switch circuit is configured to provide the internal device voltage using only the supply voltage if the supply voltage is valid, and using only the USB bus voltage if the supply voltage is invalid.

2. The USB switch circuit of claim 1, wherein the comparator is configured to compare the supply voltage to a reference.

3. The USB switch circuit of claim 2, wherein the USB switch circuit is configured to receive information from the comparator and to provide the internal device voltage using the supply voltage when the information from the comparator indicates that the supply voltage is above the reference.

4. The USB switch circuit of claim 1, wherein the supply voltage includes voltage from an internal battery of a mobile device, wherein the USB bus voltage includes voltage from an AC-to-DC converter coupled to a USB port of the mobile device.

5. The USB switch circuit of claim 1, including a switched power supply configured to receive the supply voltage and the USB bus voltage and to provide the internal device voltage using one of the supply voltage or the USB bus voltage using information from the comparator.

6. The USB switch circuit of claim 5, wherein the switched power supply includes:

first and second switching transistors configured to provide the internal device voltage using the supply voltage; and

second and third switching transistors configured to provide the internal device voltage using the USB bus voltage.

7. The USB switch circuit of claim 6, wherein a source of the first switching transistor is coupled to a source of the second switching transistor, a gate of the first switching transistor is coupled to a gate of the second switching transistor, a drain of the first switching transistor is configured to receive the supply voltage, and the drain of the second switching transistor is configured to provide the internal device voltage, and

wherein a source of the third switching transistor is coupled to a source of the fourth switching transistor, a gate of the third switching transistor is coupled to a gate of the fourth switching transistor, a drain of the third switching transistor is configured to receive the supply voltage, and the drain of the fourth switching transistor is configured to provide the internal device voltage.

8. The USB switch circuit of claim 6, including:

a break-before-make circuit configured to receive the determination that the supply voltage is valid and to control the first, second, third, and fourth switching transistors to provide the internal device voltage using the received determination.

9. A USB switch circuit configured to receive a supply voltage, to receive a USB bus voltage, and to provide an internal device voltage for the USB switch circuit, the USB switch circuit comprising:

a comparator configured to compare the supply voltage to a reference to determine if the supply voltage is valid; and

a switched power supply configured to receive the supply voltage and the USB bus voltage and to provide the internal device voltage using one of the supply voltage or the USB bus voltage using information from the comparator,

wherein the USB switch circuit is configured to control the switched power supply to provide the internal device voltage using only the supply voltage if the supply voltage is valid, and using only the USB bus voltage if the supply voltage is invalid.

10. The USB switch circuit of claim 9, wherein the switched power supply includes:

first and second switching transistors configured to provide the internal device voltage using the supply voltage; and

second and third switching transistors configured to provide the internal device voltage using the USB bus voltage.

11. The USB switch circuit of claim 10, wherein a source of the first switching transistor is coupled to a source of the second switching transistor, a gate of the first switching transistor is coupled to a gate of the second switching transistor, a drain of the first switching transistor is configured to receive the supply voltage, and the drain of the second switching transistor is configured to provide the internal device voltage, and

wherein a source of the third switching transistor is coupled to a source of the fourth switching transistor, a gate of the third switching transistor is coupled to a gate of the fourth switching transistor, a drain of the third switching transistor is configured to receive the supply voltage, and the drain of the fourth switching transistor is configured to provide the internal device voltage.

12. The USB switch circuit of claim 9, including:

a break-before-make circuit configured to receive the determination that the supply voltage is valid and to control the first, second, third, and fourth switching transistors to provide the internal device voltage using the received determination.

13. The USB switch circuit of claim 9, wherein the USB switch circuit is configured to receive information from the comparator and to provide the internal device voltage using the supply voltage when the information from the comparator indicates that the supply voltage is above the reference, and

wherein the supply voltage includes voltage from an internal battery of a mobile device, wherein the USB bus voltage includes voltage from-an AC-to-DC converter coupled to a USB port of the mobile device.

14. A method, comprising:

receiving a supply voltage at a first input of a USB switch circuit;

receiving a USB bus voltage at a second input of the USB switch circuit;

determining, using a comparator, if the supply voltage is valid; and

providing, using the USB switch circuit, an internal device voltage using only the supply voltage if the supply voltage is valid, and using only the USB bus voltage if the supply voltage is invalid.

15. The method of claim 14, wherein the determining if the supply voltage is valid includes comparing the supply voltage to a reference, and

wherein the providing the internal device voltage using the supply voltage includes when the information from the comparator indicates that the supply voltage is above the reference.

16. The method of claim 14, wherein the receiving the supply voltage includes from an internal battery of a mobile device;

and

wherein the receiving the USB bus voltage includes from an AC-to-DC converter coupled to a USB port of the mobile device.

17. The method of claim 14, wherein the USB switch circuit includes a switched power supply configured to receive the supply voltage and the USB bus voltage and to provide the internal device voltage using one of the supply voltage or the USB bus voltage using information from the comparator.

18. The method of claim 17, wherein the switched power supply includes:

first and second switching transistors configured to provide the internal device voltage using the supply voltage; and

second and third switching transistors configured to provide the internal device voltage using the USB bus voltage.

19. The method of claim 18, wherein a source of the first switching transistor is coupled to a source of the second switching transistor, a gate of the first switching transistor is coupled to a gate of the second switching transistor, a drain of the first switching transistor is configured to receive the supply voltage, and the drain of the second switching transistor is configured to provide the internal device voltage, and

wherein a source of the third switching transistor is coupled to a source of the fourth switching transistor, a gate of the third switching transistor is coupled to a gate of the fourth switching transistor, a drain of the third switching transistor is configured to receive the supply voltage, and the drain of the fourth switching transistor is configured to provide the internal device voltage.

20. The method of claim 18, including:

controlling, using a break-before-make circuit, the first, second, third, and fourth switching transistors to provide the internal device voltage using the received determination.