Redundant charging and discharging MOSFET driving in battery backup system

• US 9,843,221 B1
• Filed: 11/05/2015
• Issued: 12/12/2017
• Est. Priority Date: 01/24/2012
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Kim, Sangsun, Dailey, William Leslie, Kaneshiro, Craig, Nay, Shane R., O'Sullivan, Cornelius
• Primary Examiner(s): Whitmore, Stacy
• Application Number:
  US14/933,421
• Time in Patent Office: 768 Days
• Field of Search: 307 23, 307 43, 307 63- 66, 307127, 307135-138, 307118, 700286, 700297, 320127, 320135-138, 320118
• CPC Class Codes: H02J 1/001 Hot plugging or unplugging of load or power modules to or from power distribution networks
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: H02J 7/0045 concerning the insertion or the connection of the batteries
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 9/00 Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems

Abstract

Aspects of the disclosure relate generally to uninterruptible power supply units for systems requiring back up power. Each unit may include UPS circuitry for controlling charging and allowing discharging of a battery. The UPS circuitry may includes a controller and a plurality of metal-oxide semiconductor field effect transistors (“MOSFET”) switches. The MOSFETs may include charging and discharging MOSFETs arranged in series with the battery all driven by a single gate driver, such as a controller. In this regard, the controller may limit the charging current though all of the MOSFETs and charge the battery. The MOSFETs may be arranged such that if the charging MOSFET fails, the redundant charging MOSFET may continue to limit the charging current to the battery. Similarly, a redundant discharging MOSFET may be arranged in series with a discharging MOSFET in order to continue to provide discharging current if the discharging MOSFET fails.

Claims

1. An uninterruptible power supply unit comprising:

a battery;

first and second MOSFET switches each connected in series with the battery, the first MOSFET and second MOSFET switches being configured to charge the battery when the first and second MOSFET switches are operating in a linear region, and the second MOSFET switch and the first MOSFET switch are arranged such that when the first MOSFET switch fails, the second MOSFET switch continues to operates in the linear region to charge the battery; and

a single gate driver configured to drive the first and second MOSFET switches together.

2. The uninterruptible power supply unit of claim 1, further comprising a feedback device arranged in series with the first and second MOSFET switches, the feedback device being configured to provide feedback information to the gate driver, wherein the gate driver is further configured to control current through the first and second MOSFET switches based on the feedback information.

3. The uninterruptible power supply unit of claim 2, wherein the feedback device includes a shunt resistor.

4. The uninterruptible power supply unit of claim 2, wherein the gate driver is configured to adjust a gate-to-source voltage of the first MOSFET switch and the second MOSFET switch based on the feedback information.

5. The uninterruptible power supply unit of claim 1, further comprising a diode configured to isolate the first MOSFET switch when the first MOSFET switch fails.

6. The uninterruptible power supply unit of claim 1, wherein the gate driver comprises an amplifier.

7. The uninterruptible power supply unit of claim 1, further comprising a third MOSFET switch arranged in series with the battery such that when charging current falls below a threshold value, the third MOSFET switch is switched on and operates in a switching region to provide discharging current from the battery to a load.

8. The uninterruptible power supply unit of claim 7, wherein the first and third MOSFET switches are configured to operate together as a bidirectional switch.

9. The uninterruptible power supply unit of claim 7, further comprising a signal ground, wherein the first and second MOSFET switches are configured closer to the battery than the signal ground and the third MOSFET switches are configured closer to the signal ground than the battery.

10. The uninterruptible power supply unit of claim 1, further comprising a protection circuit configured to switch the first and second MOSFET switches to an off condition and disconnect the uninterruptible power supply unit from an external power source when the uninterruptible power supply unit is operating outside of a predetermined normal operating range while the battery is charging.

11. The uninterruptible power supply unit of claim 1, further comprising a protection circuit configured to switch both the first and second MOSFET switches to an off condition and disconnect the uninterruptible power supply unit from an external load when the uninterruptible power supply unit is operating outside of a predetermined normal operating range while the battery is discharging.

12. A system comprising:

a load configured to receive power from a power supply;

an uninterruptible power supply unit in electrical communication with the load, the uninterruptible power supply unit comprising;

a battery;

first and second MOSFET switches connected in series with the battery, the first MOSFET and second MOSFET switches charging the battery when the first and second MOSFET switches are operating in a linear region, and the second MOSFET switch and the first MOSFET switch are arranged such that when the first MOSFET switch fails, the second MOSFET switch continues to operates in the linear region to charge the battery; and

a single gate driver driving the first and second MOSFET switches together.

13. The system of claim 12, wherein the uninterruptible power supply unit further includes a feedback device arranged in series with the first and second MOSFET switches, the feedback device being configured to provide feedback information to the gate driver, wherein the gate driver is further configured to control current through the first and second MOSFET switches based on the feedback information.

14. The system of claim 13, wherein the feedback device includes a shunt resistor.

15. The system of claim 13, wherein the gate driver is configured to adjust a gate-to-source voltage of the first MOSFET switch and the second MOSFET switch based on the feedback information.

16. The system of claim 12, wherein the uninterruptible power supply unit further includes a diode configured to isolate the first MOSFET switch when the first MOSFET switch fails.

17. The system of claim 12, wherein the uninterruptible power supply unit further includes a third MOSFET switch arranged in series with the battery such that when charging current falls below a threshold value, the third MOSFET switch is switched on and operates in a switching region to provide discharging current from the battery to a load.

18. The system of claim 17, wherein the first and third MOSFET switches are configured to operate together as a bidirectional switch.

19. The system of claim 17, wherein the uninterruptible power supply unit further includes a signal ground, wherein the first and second MOSFET switches are configured closer to the battery than the signal ground and the third MOSFET switches are configured closer to the signal ground than the battery.

20. The system of claim 12, wherein the uninterruptible power supply unit further includes a protection circuit configured to switch both the first and second MOSFET switches to an off condition and disconnect the uninterruptible power supply unit from an external load when the uninterruptible power supply unit is operating outside of a predetermined normal operating range while the battery is discharging.