Leakage reduction circuit

• US 10,063,156 B2
• Filed: 03/27/2014
• Issued: 08/28/2018
• Est. Priority Date: 03/27/2014
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Fong, Chee Kiong, Perchilk, David Richard, Tin, Suet Fong, Rulien, Michael Donovan, Stultz, Perry Samuel, Giaimo, III, Edward C.
• Primary Examiner(s): Moody, Kyle J
• Assistant Examiner(s): Dang, Trinh Q
• Application Number:
  US14/227,119
• Publication Number:
  US 20150280587A1
• Time in Patent Office: 1,615 Days
• Field of Search: 363 2104, 363 52
• CPC Class Codes: H02M 1/123 Suppression of common mode voltage or current
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H02M 3/33546 with automatic control of the output voltage or current H02M3/33561 takes precedence

Abstract

A leakage reduction circuit is described herein that is configured to reduce high voltage leakage that may occur in electrical power step-down scenarios. The leakage reduction circuit, for instance, may be employed in a power adapter for a client device, such as a mobile computing device. For example, a power adapter may include a high voltage alternating current (AC) input, and circuitry for converting the AC input into lower voltage direct current (DC) for output to a client device. Implementations of the disclosed leakage reduction circuit include an arrangement of capacitors that provides a noise return path (e.g., for common mode noise) in a power adapter, while reducing high voltage leakage that may occur from a high voltage AC input to a lower voltage DC output of the power adapter.

Claims

1. A power adapter comprising:

a primary circuit portion configured to be connected to an alternating current (AC) power source;

a secondary circuit portion operably connected to the primary circuit portion and configured to convert AC power received from the primary circuit portion into direct current (DC) power;

a connector operably connected to the secondary circuit portion and connectable to a client device to provide DC power from the secondary circuit portion to the client device; and

a leakage reduction circuit configured to provide a noise return path from the secondary circuit portion to the primary circuit portion and to reduce high voltage leakage from the primary circuit portion to the secondary circuit portion, the leakage reduction circuit including;

a first Y-capacitor operably connected between a secondary ground of the secondary circuit portion and a primary ground of the primary circuit portion;

a second Y-capacitor operably connected between the secondary ground of the secondary circuit portion and an AC neutral connection of the primary circuit portion, the second Y-capacitor setting an AC voltage on the secondary ground to zero with respect to the AC neutral connection, the first Y-capacitor and the second Y-capacitor having a same nominal capacitance value; and

an X-capacitor operably connected between the AC neutral connection and an AC line input of the primary circuit portion.

2. The power adapter as described in claim 1, further comprising a line prong configured to connect the AC line input of the primary circuit portion to an AC line output of the AC power source, a neutral prong configured to connect the AC neutral connection of the primary circuit portion to an AC neutral line of the AC power source, and wherein the power adapter does not include a dedicated ground prong.

3. The power adapter as described in claim 1, wherein the first Y-capacitor and the second Y-capacitor each have a capacitance value of 330 picofarads.

4. The power adapter as described in claim 1, wherein:

connection of the first Y-capacitor between the secondary ground of the secondary circuit portion and the primary ground of the primary circuit portion defines a first noise return path for the leakage reduction circuit;

connection of the second Y-capacitor between the secondary ground of the secondary circuit portion and the AC neutral connection of the primary circuit portion defines a second noise return path for the leakage reduction circuit; and

connection of the X-capacitor between the AC neutral connection and the AC line input of the primary circuit portion defines a third noise return path for the leakage reduction circuit.

5. The power adapter as described in claim 1, wherein the leakage reduction circuit does not include a Y-capacitor operably connected between the secondary ground and the AC line input.

6. The power adapter as described in claim 2, wherein the line prong and the neutral prong are one or more of foldable or retractable into a housing of the power adapter.

7. The power adapter as described in claim 3, wherein the X-capacitor has a capacitance value of 1 nanofarad.

8. A leakage reduction circuit for a power adapter comprising:

a primary circuit portion configured to be connected to an alternating current (AC) power source;

a secondary circuit portion operably connected to the primary circuit portion and configured to convert AC power received from the primary circuit portion into direct current (DC) power for output to a computing device;

a first Y-capacitor operably connected between a secondary ground of the secondary circuit portion and a primary ground of the primary circuit portion;

a second Y-capacitor operably connected between the secondary ground of the secondary circuit portion and an AC neutral connection of the primary circuit portion, the second Y-capacitor setting an AC voltage on the secondary ground to zero with respect to the AC neutral connection, the first Y-capacitor and the second Y-capacitor having a same nominal capacitance value; and

an X-capacitor operably connected between the AC neutral connection and an AC line input of the primary circuit portion.

9. The leakage reduction circuit as described in claim 8, wherein the first Y-capacitor and the second Y-capacitor each have a capacitance value of 330 picofarads.

10. The leakage reduction circuit as described in claim 8, wherein:

connection of the first Y-capacitor between the secondary ground of the secondary circuit portion and the primary ground of the primary circuit portion defines a first noise return path for the leakage reduction circuit;

connection of the second Y-capacitor between the secondary ground of the secondary circuit portion and the AC neutral connection of the primary circuit portion defines a second noise return path for the leakage reduction circuit; and

connection of the X-capacitor between the AC neutral connection and the AC line input of the primary circuit portion defines a third noise return path for the leakage reduction circuit.

11. The leakage reduction circuit as described in claim 8, wherein the leakage reduction circuit does not include a Y-capacitor operably connected between the secondary ground and the AC line input.

12. The leakage reduction circuit as described in claim 8, wherein the primary circuit portion includes:

a line prong operably connected to an AC line input of the primary circuit portion;

a neutral prong operably connected to an AC neutral connection of the primary circuit portion, and

wherein the power adapter does not include a dedicated ground prong.

13. The leakage reduction circuit as described in claim 12, wherein the line prong and the neutral prong are one or more of foldable or retractable into a housing of the power adapter.

18. The leakage reduction circuit as described in claim 8, wherein at least part of the leakage reduction circuit is positioned within a client device.

14. A leakage reduction circuit for a power adapter comprising:

a primary circuit portion configured to be connected to an alternating current (AC) power source;

a secondary circuit portion operably connected to the primary circuit portion and configured to convert AC power received from the primary circuit portion into direct current (DC) power for output to a computing device;

a plurality of noise return paths for returning noise from the secondary circuit portion to the primary circuit portion, the noise return paths including;

a first noise return path including a first Y-capacitor operably connected between a secondary ground of the secondary circuit portion and a primary ground of the primary circuit portion;

a second noise return path including a second Y-capacitor operably connected between the secondary ground of the secondary circuit portion and an AC neutral connection of the primary circuit portion, the second Y-capacitor setting an AC voltage on the secondary ground to zero with respect to the AC neutral connection, the first Y-capacitor and the second Y-capacitor having a same nominal capacitance value; and

a third noise return path including an X-capacitor operably connected between the AC neutral connection and an AC line input of the primary circuit portion, the X-capacitor having a nominal capacitance value different than the same nominal capacitance value.

15. The leakage reduction circuit as described in claim 14, wherein the first Y-capacitor and the second Y-capacitor each have a capacitance value of 330 picofarads.

16. The leakage reduction circuit as described in claim 14, wherein the leakage reduction circuit does not include a Y-capacitor operably connected between the secondary ground and the AC line input.

17. The leakage reduction circuit as described in claim 14, wherein the primary circuit portion includes:

a line prong operably connected to an AC line input of the primary circuit portion;

a neutral prong operably connected to an AC neutral connection of the primary circuit portion, and

wherein the power adapter does not include a dedicated ground prong.

19. The leakage reduction circuit as described in claim 15, wherein the X-capacitor has a capacitance value of 1 nanofarad.

20. The leakage reduction circuit as described in claim 17, wherein the line prong and the neutral prong are one or more of foldable or retractable into a housing of the power adapter.