SYSTEM AND METHOD FOR WIRELESS POWER TRANSFER USING AUTOMATIC POWER SUPPLY SELECTION

• US 20160077562A1
• Filed: 06/26/2015
• Published: 03/17/2016
• Est. Priority Date: 09/16/2014
• Status: Active Grant

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Inventors: Smith, Nicholaus W.
• Granted Patent: US 9,898,060 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• 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
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources

Abstract

A system and method of wireless power transfer using automatic power supply selection includes an electronic system. The electronic system includes an electronics module, a primary power supply that receives power from a primary external power source, a secondary power supply that receives power from a secondary external power source, and a selection module. When the primary power supply is operative, the selection module selects the primary power supply to supply power to the electronics module and disables the secondary power supply. When the primary power supply is not operative and the secondary power supply is operative, the selection module selects the secondary power supply to supply power to the electronics module. When the secondary power supply is disabled, the secondary power supply disables the secondary external power source.

Claims

1. An electronic system comprising:

an electronics module;

a primary power supply that receives power from a primary external power source and supplies the received power to the electronics module when operative;

a secondary power supply that receives power from a secondary external power source and supplies the received power to the electronics module when operative; and

a selection module having first and second input rails coupled to the primary and secondary power supplies, respectively, and an output rail coupled to the electronics module;

wherein;

when the primary power supply is operative, the selection module selects the primary power supply to supply power to the electronics module and disables the secondary power supply;

when the primary power supply is not operative and the secondary power supply is operative, the selection module selects the secondary power supply to supply power to the electronics module; and

when the secondary power supply is disabled, the secondary power supply disables the secondary external power source.

2. The electronic system of claim 1, further comprising a battery coupled to the electronics module.

3. The electronic system of claim 1, wherein the secondary power supply includes a wireless power receiver and the secondary external power source includes a wireless power transmitter.

4. The electronic system of claim 6, wherein when the secondary power supply is disabled and engaged with the secondary external power source, the wireless power receiver disables the wireless power transmitter.

5. The electronic system of claim 3, wherein the primary power supply is configured to receive power over a wire from the primary external power sources.

6. The electronic system of claim 5, wherein the wire is selected from a group consisting of a universal serial bus cable, an Ethernet cable, a dock connector, an alternating current power cord, and a laptop charging cable.

7. The electronic system of claim 1, wherein the selection module further includes:

a first switch coupled between the first input rail and the output rail; and

a second switch coupled between the second input rail and the output rail;

wherein;

when the primary power supply is operative, the first switch is closed and the second switch is open; and

when the primary power supply is not operative and the secondary power supply is operative, the first switch is open and the second switch is closed.

8. The electronic system of claim 7, wherein the first and second switches are each associated with a body diode oriented to allow current flow towards the output rail.

9. The electronic system of claim 7, wherein the selection module further includes:

a first control module configured to detect when the primary power supply is operative, and when the primary power supply is operative, provide a first control signal to open the second switch and a second control signal to disable the secondary power supply; and

a second control module configured to detect when the second power supply is operative, and when the second power supply is operative, provide a third control signal to open the first switch.

10. The electronic system of claim 7, wherein when the first or second switch is open, reverse leakage current is blocked from flowing from the output rail towards the input rail corresponding to the open switch.

11. A power supply selection circuit comprising:

a first switch coupled between a first input node and an output node, the first input node carrying a first input voltage;

a second switch coupled between a second input node and the output node, the second input node carrying a second input voltage;

a first control subcircuit coupled between the first input node and the second switch, the first control subcircuit being configured to apply a first control voltage to the second switch and an enable/disable voltage, wherein each voltage is based on the first input voltage; and

a second control subcircuit coupled between the second input node and first switch, the second control subcircuit being configured to apply a third control voltage to the first switch based on the second input voltage.

12. The power supply selection circuit of claim 11, wherein:

the first control subcircuit is configured to close the second switch when the first input voltage is at a low level and open the second switch when the first input voltage is at the high level; and

the second control circuit is configured to close the first switch when the second input voltage is at a low level and open the first switch when the second input voltage is at a high level.

13. The power supply selection circuit of claim 12, wherein the first and second switches include first and second field effect transistors (FETs), each FET having a source, gate and drain, wherein:

the source of each FET is coupled to the output node;

the drain of the first FET is coupled to the first input node;

the drain of the second FET is coupled to the second input node;

the gate of the second FET is coupled to a first control node carrying the first control voltage; and

the gate of the first FET is coupled to a second control node carrying the second control voltage.

14. The power supply selection circuit of claim 13, wherein the first and second FETs are p-type FETs.

15. The power supply selection circuit of claim 13, wherein:

the first control subcircuit includes a first resistor coupled between the first input node and the first control node and a second resistor coupled between the first control node and a ground node, the first and second resistors forming a first voltage divider; and

the second control subcircuit includes a third resistor coupled between the second input node and the second control node and a fourth resistor coupled between the second control node and the ground node, the third and fourth resistors forming a second voltage divider;

wherein the first control voltage is a predetermined fraction of the first input voltage; and

wherein the second control voltage is a predetermined fraction of the second input voltage.

16. The power supply selection circuit of claim 15, wherein the predetermined fraction is approximately 9/10 or greater.

17. The power supply selection circuit of claim 15 wherein the first control subcircuit further includes a fifth resistor coupled between the first control node and an enable/disable node, the enable/disable node carrying the enable/disable voltage.

18. The power supply selection circuit of claim 17, wherein the first control subcircuit further includes a first capacitor arranged in parallel with the second resistor, the first capacitor being configured to control transient responses associated with the first control voltage and the enable/disable voltage.

19. A method comprising:

conducting power from a wireless power receiver to a system power supply rail through a closed first switch;

detecting a turn-on of a wired power receiver;

after detecting the turn-on of the wired power receiver;

opening the first switch;

disabling the wireless power receiver, wherein disabling the wireless power receiver includes disabling a wireless power transmitter engaged with the wireless power receiver;

closing a second switch; and

conducting power from the wired power supply to the system power supply rail through the closed second switch.

20. The method of claim 19, further comprising:

detecting a turn-off of the wired power supply;

after detecting the turn-off of the wired power supply;

enabling the wireless power receiver, wherein enabling the wireless power receiver includes enabling the wireless power transmitter;

closing the first switch;

opening the second switch;

conducting power from a wireless power supply to a system power supply rail through the closed first switch.