Electronic devices with magnetic field compensating conductive traces

• US 9,046,365 B2
• Filed: 10/27/2011
• Issued: 06/02/2015
• Est. Priority Date: 10/27/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wade, Jeremy L., Eng, Michael, Garrone, Ryan J., Brown, Mark
• Primary Examiner(s): GUADALUPE, YARITZA
• Application Number:
  US13/283,438
• Publication Number:
  US 20130104410A1
• Time in Patent Office: 1,314 Days
• Field of Search: 333/56, 333/57, 333/55.R, 333/55.D, 333/61
• US Class Current: 1/1
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26

Abstract

Electronic devices may be provided with compasses for detecting the Earth'"'"'s magnetic field. Electronic devices may be provided with electronic components that generate interfering magnetic fields for the compass. Electronic components may be coupled between a power supply line and a power return line on a printed circuit. The power return line may be configured to generate a compensating magnetic field to counteract the interfering magnetic fields. The power return line may be formed parallel to the power supply line. The power supply line may have multiple branches equidistant from the compass. The power return line may have a portion closer to the compass than the power supply line and the electronic component. The power return line may have multiple branches, may be provided with resistors on each branch and may include a portion of a circular loop the runs around the compass on the printed circuit board.

Claims

1. A portable electronic device, comprising:

a printed circuit board;

a compass mounted on the printed circuit board;

at least one conductive power line on the printed circuit board that generates an interfering magnetic field for the compass; and

at least one conductive return line on the printed circuit board that generates a compensating magnetic field that compensates for the interfering magnetic field for the compass.

2. The portable electronic device defined in claim 1 wherein the printed circuit board comprises opposing first and second sides, wherein the at least one conductive power line and the at least one conductive return line are formed on the first side, and wherein at least a portion of the at least one conductive return line is parallel to the at least one conductive power line.

3. The portable electronic device defined in claim 2, further comprising an electronic component coupled to the at least one conductive power line and the at least one conductive return line.

4. The portable electronic device defined in claim 1 wherein the printed circuit board comprises opposing first and second sides, wherein the at least one conductive power line is formed on the first side, wherein at least a portion of the at least one conductive return line is formed on the second side parallel to the at least one conductive power line.

5. The portable electronic device defined in claim 4, further comprising an electronic component configured to receive power from the at least one conductive power line and the at least one conductive return line.

6. The portable electronic device defined in claim 5, further comprising at least one conductive via in the printed circuit board that extends from the first side to the second side, wherein the at least one conductive via electrically couples the electronic component to the at least one conductive return line on the second side.

7. The portable electronic device defined in claim 6, further comprising a conductive ground plane on the second side that is coupled to the at least a portion of the at least one conductive return line on the second side.

8. The portable electronic device defined in claim 1 wherein the at least one conductive power line has a minimum distance from the compass and a maximum distance from the at least one conductive return line, and wherein the maximum distance is smaller than the minimum distance.

9. A portable electronic device, comprising:

a printed circuit board;

a compass mounted on the printed circuit board; and

first and second conductive power lines mounted on the printed circuit board on opposing sides of the compass, wherein the first and second conductive power lines are separated from the compass by a common minimum lateral distance.

10. The portable electronic device defined in claim 9, further comprising power supply circuitry, wherein the first and second conductive power lines comprise first and second branches of a common conductive power path that is coupled to the power supply circuitry.

11. The portable electronic device defined in claim 10, further comprising a conductive ground plane, wherein the printed circuit board comprises opposing first and second sides, wherein the conductive ground plane is formed on the second side, and wherein the conductive power path is formed on the first side.

12. The portable electronic device defined in claim 9 wherein the printed circuit board comprises opposing first and second sides, wherein the first and second conductive power lines are formed on the first side, wherein the first conductive power line is separated from the compass by the common minimum distance, and wherein the second conductive power line is separated from the compass by the common minimum distance, the electronic device further comprising:

a first conductive return line parallel to the first conductive supply line; and

a second conductive return line parallel to the second conductive supply line, wherein the first and second conductive return lines are formed on the second side.

13. A portable electronic device, comprising:

a printed circuit board;

a compass mounted on the printed circuit board;

an electronic component on the printed circuit board;

power supply circuitry on the printed circuit board;

a first conductive line on the printed circuit board that extends along a path between the power supply circuitry and the electronic component; and

a second conductive line on the printed circuit board that is coupled between the power supply circuitry and the electronic component, wherein power is distributed from the power supply circuitry to the electronic component using the first and second conductive lines, wherein the electronic component generates an interfering magnetic field for the compass during operation of the electronic component, and wherein at least a portion of the second conductive line deviates away from the path towards the compass so that the second conductive line generates a compensating magnetic field that compensates for the interfering magnetic field.

14. The portable electronic device defined in claim 13 wherein the second conductive line comprises a first portion that is parallel to the first conductive line, a second portion that is perpendicular to the first conductive line, and at least one portion that is formed at an acute angle with respect to the first conductive line.

15. The portable electronic device defined in claim 13 wherein the compass is mounted on a surface of the printed circuit board, wherein the second conductive line is formed on the surface, and wherein the portion of the second conductive line comprises a portion of a circular loop that runs around the compass on the surface of the printed circuit board.

16. The portable electronic device defined in claim 13 wherein the portion of the second conductive line comprises a branch of the second conductive line having a resistor, wherein the second conductive line comprises an additional branch coupled to the branch, wherein the additional branch has an additional resistor, and wherein at least a portion of the additional branch is parallel to the first conductive line.

17. The portable electronic device defined in claim 16 wherein the compass is mounted on a surface of the printed circuit board, wherein the second conductive line is formed on the surface of the printed circuit board, and wherein the branch of the second conductive line comprises a portion of a circular loop that runs around the compass on the surface of the printed circuit board.

18. The portable electronic device defined in claim 13, further comprising power supply circuitry having a positive terminal coupled to the first conductive line.

19. The portable electronic device defined in claim 18 wherein the electronic component comprises a camera having a lens, at least one fixed magnet, and a wire coil, wherein an electric current that flows through the wire coil and the first conductive line generates the interfering magnetic field, and wherein the power supply circuitry is configured to change the electric current to move the lens.

20. The portable electronic device defined in claim 13 wherein the electronic component comprises a light source, wherein an electric current that flows through the first conductive line and the second conductive line generates the interfering magnetic field and the compensating magnetic field respectively, and wherein the power supply circuitry is configured to control the electric current to operate the light source.

21. A portable electronic device comprising

a printed circuit board having at least one layer with opposing first and second sides;

a compass mounted on the first side of the layer; and

a conductive ground plane on the second side of the layer having a recess under the compass.