Redundant charging and discharging MOSFET driving in battery backup system

• US 9,214,833 B1
• Filed: 09/14/2012
• Issued: 12/15/2015
• Est. Priority Date: 01/24/2012
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Kim, Sangsun, Dailey, William, Kaneshiro, Craig, Nay, Shane R., O'Sullivan, Cornelius
• Primary Examiner(s): Whitmore, Stacy
• Application Number:
  US13/617,669
• Time in Patent Office: 1,187 Days
• Field of Search: 307/23, 307/43, 307 63- 66, 320/118, 320/127, 320135-138, 700/286, 700/297
• US Class Current: 1/1
• 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, second, third, and fourth 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, the third and fourth MOSFET switches are configured such that when the charging current falls below a threshold value, the third and fourth MOSFET switches are switched on such that the third and fourth MOSFET switches operate in a switching region provide discharging current from the battery; and

a single gate driver configured to drive all of the first, second, third, and fourth MOSFET switches together.

2. The uninterruptible power supply unit of claim 1, further comprising a feedback device arranged in series with the first, second, third, and fourth 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, wherein 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.

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

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

8. The uninterruptible power supply unit of claim 1, wherein the first and third MOSFET switches are configured to operate together as a bidirectional switch.

9. The uninterruptible power supply unit of claim 1, wherein the second and fourth MOSFET switches are configured to operate together as a bidirectional switch.

10. The uninterruptible power supply unit of claim 1, wherein the first and second MOSFET switches are configured closer to the battery than a signal ground and the third and fourth MOSFET switches are configured closer to the signal ground than the battery.

11. The uninterruptible power supply unit of claim 1, further comprising a protection circuit configured to switch all of the first, second, third, and fourth 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.

12. The uninterruptible power supply unit of claim 1, further comprising a protection circuit configured to switch all of the first, second, third, and fourth 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.

13. 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, second, third, and fourth MOSFET switches each 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, the third and fourth MOSFET switches are configured such that when the charging current falls below a threshold value, the third and fourth MOSFET switches are switched on such that the third and fourth MOSFET switches operate in a switching region provide discharging current from the battery; and

a single gate driver driving all of the first, second, third, and fourth MOSFET switches together.

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

15. The system of claim 13, wherein the third and fourth MOSFET switches are configured such that when the charging current falls below a threshold value, the third and fourth MOSFET switches are switched on, where that the third and fourth MOSFET switches operate in a switching region, and the third and fourth MOSFET switches provide discharging current from the battery.

16. The system of claim 13, wherein the first and second MOSFET switches are configured closer to the battery than a signal ground and the third and fourth MOSFET switches are configured closer to the signal ground than the battery.

17. The system of claim 13, wherein the uninterruptible power supply unit further comprises a protection circuit configured to switch all of the first, second, third, and fourth 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.

18. The system of claim 13, wherein the uninterruptible power supply unit further comprises a protection circuit configured to switch all of the first, second, third, and fourth MOSFET switches to an off condition and disconnect the uninterruptible power supply unit from the load when the uninterruptible power supply unit is operating outside of a predetermined normal operating range while the battery is discharging.

19. An uninterruptible power supply unit comprising:

a battery;

a first MOSFET switch and a second MOSFET switch connected in series with and being proximate to the battery, the first MOSFET switch and the second MOSFET switch being configured to charge the battery when the first MOSFET switch and the second MOSFET switch are operating in a linear region; and

a single gate driver for controlling current through the first MOSFET switch and the second MOSFET switch; and

a third MOSFET switch connected in series to the first and second MOSFET switches, the third MOSFET switch being proximate to a signal ground, the third MOSFET switch being configured to provide discharging current when the third MOSFET is in the fully on condition of the switching mode.

20. The uninterruptible power supply unit of claim 19, further comprising a fourth MOSFET switch in series with the first, second and third MOSFET switches, the fourth MOSFET switch being configured to charge the battery when the third MOSFET switch and the fourth MOSFET switch are operating in a linear region.

21. An uninterruptible power supply unit comprising:

a battery;

a first MOSFET switch connected in series with and being proximate to the battery, the first MOSFET switch being configured to charge the battery when the first MOSFET switch is operating in a linear region;

a second MOSFET switch connected in series to the first MOSFET switch, the second MOSFET switch being configured to provide discharging current when the second MOSFET is in a fully on condition of a switching mode; and

a third MOSFET switch connected in series to the first and second MOSFET switches, the third MOSFET switch being configured to provide discharging current when the third MOSFET is in the fully on condition of the switching mode, wherein the second MOSFET switch and third MOSFET switch are closer to the signal ground than the battery.

22. The uninterruptible power supply unit of claim 21, further comprising a fourth MOSFET switch in series with the first, second and third MOSFET switches, the fourth MOSFET switch being configured to provide discharging current when the third MOSFET is in the fully on condition of the switching mode.