INDUCTIVE CLAMPING CIRCUIT

• US 20160149505A1
• Filed: 11/24/2014
• Published: 05/26/2016
• Est. Priority Date: 11/24/2014
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Dickey, John A.
• Granted Patent: US 9,590,520 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 5/293 using semiconductor devices only

Abstract

A power control circuit includes a solid state power controller operable to connect an AC power source to a load. The solid state power controller includes a first switching device and a second switching device arranged serially. Each of the switching devices includes a diode, a controller controllably coupled to each of the first switching device and the second switching device, such that the controller is capable of controlling an on/off state of the first switching device and the second switching device. The controller further includes a non-transitory memory storing instructions for causing the controller to perform the steps of: switching off a first switching device having a diode aligned with a current polarity of an AC current flow prior to a first zero crossing, delaying a switching off of a second switching device until after the first zero crossing, and switching the second switching device off after the delay and before a second zero crossing.

Claims

1. A method for switching off an inductive load comprising:

switching off a first switching device having a diode aligned with a current polarity of an AC current flow prior to a first zero crossing;

delaying a switching off of a second switching device until after said first zero crossing; and

switching the second switching device off after said delay and before a second zero crossing.

2. The method of claim 1, wherein each of said first switching device and said second switching device is a MOSFET.

3. The method of claim 1, wherein there are no intervening zero crossings between the second zero crossing and the first zero crossing.

4. The method of claim 1, wherein switching off a first switching device having a diode aligned with a current polarity of an AC current flow prior to a first zero crossing comprises causing a diode of the first switching device to operate as a freewheeling diode, thereby allowing current in the inductive load to continue to flow.

5. The method of claim 1, wherein switching the second switching device off after said delay and before a second zero crossing occurs when a half cycle of the AC current is approximately 90 degrees past the first zero crossing.

6. The method of claim 1, further comprising determining a current polarity of an AC current flowing into an inductive load prior to switching off the first switching device.

7. The method of claim 6, wherein determining a current polarity of an AC current flowing into an inductive load prior to switching off the first switching device further comprises determining a corresponding switching device having an aligned diode.

8. The method of claim 1, wherein delaying a switching off of a second switching device until after said first zero crossing comprises delaying switching of the second switching device for one of a predetermined period of time period and a time period defined as elapsing when the current has completely stopped flowing.

9. The method of claim 1, wherein delaying a switching off of a second switching device until after said first zero crossing comprises determining a required delay length such that said switching the second switching device off after said delay and before a second zero crossing occurs between the first zero crossing and the second zero crossing.

10. The method of claim 1, wherein switching off a first switching device having a diode aligned with a current polarity of an AC current flow prior to a first zero crossing further comprises switching off a second switching device having a diode unaligned with a current polarity of an AC current flow when a load fault is detected, thereby bypassing the steps of delaying a switching off of a second switching device until after said first zero crossing, and switching the second switching device off after said delay and before a second zero crossing.

11. A power control circuit comprising:

a solid state power controller operable to connect an AC power source to a load, wherein the solid state power controller includes a first switching device and a second switching device arranged serially and wherein each of said switching devices includes a diode,

a controller controllably coupled to each of said first switching device and said second switching device, such that said controller is capable of controlling an on/off state of said first switching device and said second switching device;

said controller further including a non-transitory memory storing instructions for causing the controller to perform the steps of;

switching off a first switching device having a diode aligned with a current polarity of an AC current flow prior to a first zero crossing;

delaying a switching off of a second switching device until after said first zero crossing; and

switching the second switching device off after said delay and before a second zero crossing.

12. The power control circuit of claim 11, wherein said controller is a component of said solid state power controller.

13. The power control circuit of claim 11, wherein said controller is an independent controller.

14. The power control circuit of claim 11, wherein said first switching device is a MOSFET and said second switching device is a MOSFET.

15. The power control circuit of claim 11, wherein said first switching device is a MOSFET transistor network and said second switching device is a MOSFET transistor network.

16. The power control circuit of claim 11, further comprising an AC power source connected to said solid state power controller, such that said solid state power controller is operable to control a flow of AC power from said AC power source to a load connected to the solid state power controller.