System and method for an inductive proximity switch on a common substrate

• US 8,203,335 B2
• Filed: 03/28/2008
• Issued: 06/19/2012
• Est. Priority Date: 03/28/2008
• Status: Expired due to Fees

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Inventors: Feldtkeller, Martin
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US12/058,521
• Publication Number:
  US 20090243601A1
• Time in Patent Office: 1,544 Days
• Field of Search: 324/207.26, 307/130
• US Class Current: 324/207.26
• CPC Class Codes: H03K 17/9505 Constructional details
• CPC Class Codes: H03K 17/954 controlled by an oscillatory signal
• CPC Class Codes: H03K 2217/96072 Phase comparison, i.e. where a phase comparator receives at one input the signal directly from the oscillator, at a second input the same signal but delayed, with a delay depending on a sensing capacitance

Abstract

An inductive proximity switch device has inductive elements including at least one transmitter coil and at least one receiver coil disposed on a common substrate. The inductive elements are arranged in one or more metalizing layers on the common substrate, and an evaluation circuit is coupled to at least one of the plurality of the inductive elements.

Claims

1. An inductive proximity switch device comprising:

a plurality of inductive elements disposed on a common substrate, the inductive elements arranged in one or more metalizing layers on the common substrate, the inductive elements comprising

a transmitter coil, and

a plurality of receiver coils; and

an evaluation circuit coupled to at least one of the plurality of the inductive elements, wherein the transmitter coil is configured to generate a magnetic stray field that reaches a metal object present in the vicinity of the proximity switch device, and the receiver coils are arranged and configured such that, with an undisturbed magnetic stray field, voltages induced by the magnetic stray field in the receiver coils are substantially equal; and

a plurality of capacitors integrated on the common substrate, wherein the receiver coils are coupled with the capacitors to form LC oscillator circuits, each comprising an inductive element and a capacitive element.

2. The inductive proximity switch device according to claim 1, wherein the common substrate comprises a single chip such that the inductive elements are monolithically integrated on the single chip.

3. The inductive proximity switch device according to claim 1, wherein the inductive elements of the proximity switch are implemented as coils with a plurality of conductor paths or windings or antennas.

4. The inductive proximity switch device according to claim 1, wherein the evaluation circuit and the inductive elements are integrated on the common substrate.

5. The inductive proximity switch device according to claim 1, wherein two of the receiver coils are arranged and configured such that, if a metal body is present in the magnetic stray field, a magnetic field flowing through one of the two receiver coils changes more strongly than a magnetic field flowing through an other one of the two receiver coils.

6. The inductive proximity switch device according to claim 1, wherein the evaluation circuit is configured to evaluate output signals of the inductive elements that is integrated on the common substrate, and is configured to detect an approximation of a metal object in the vicinity of the proximity switch device from a difference between induced voltage or current characteristics of the receiver coils.

7. The inductive proximity switch device according to claim 1, wherein the evaluation circuit is configured to evaluate output signals of the inductive elements that is integrated on the common substrate, wherein the evaluation circuit comprises a differential amplifier for detecting the difference between induced voltage or current characteristics of the receiver coils.

8. The inductive proximity switch device according to claim 7, wherein conductor paths or windings of the receiver coils are coupled to the differential amplifier, respectively, the differential amplifier being configured to recognize a difference of the voltages induced into the receiver coils.

9. The inductive proximity switch device according to claim 1, wherein the receiver coils are complementary connected in series with each other, so that their induced voltages substantially compensate each other in an undisturbed magnetic stray field with no metal object positioned in the vicinity of the proximity switch device, and do not compensate each other in case of an disturbed stray field due to a metal object or body positioned in the vicinity of the proximity switch.

10. The inductive proximity switch device according to claim 1, wherein the LC oscillators circuits are configured to be alternately switched on and off, and an evaluation circuit is configured to evaluate a frequency modulation of a sum signal derived from an addition of output signals of the LC oscillator circuits.

11. The inductive proximity switch device according to claim 1, wherein the receiver coils are arranged in a layer parallel to a layer of the transmitter coil such that the transmitter coil and the receiver coils are arranged in a planar manner integrated on the common substrate.

12. The inductive proximity switch device according to claim 11, wherein part of a cross-section of the receiver coils is positioned inside dimensions of the transmitter coil and another part of the cross-section of the receiver coils is positioned outside dimensions of the transmitter coil.

13. The inductive proximity switch device according to claim 12, wherein the receiver coils are arranged in a staggered manner with respect to the transmitter coil such that, with an undisturbed stray field, magnetic flux passing through the receiver coil outside and inside the transmitter coil is substantially compensated.

20. The inductive proximity switch device according to claim 1, wherein the transmitter coil is connected to a switchable current source configured to switch current flowing through the transmitter coil on and off in a pulse-shaped or in a sinusoidal manner.

21. The inductive proximity switch device according to claim 1, wherein conductor paths or windings of the at least one transmitter coil comprises a larger cross section than conductor paths or windings of the at least one receiver coil.

14. An inductive proximity switch device comprising:

a plurality of inductive elements disposed on a common substrate, the inductive elements arranged in one or more metalizing layers on the common substrate, the inductive elements comprising

at least one transmitter coil, and

at least one receiver coil; and

an evaluation circuit coupled to at least one of the plurality of the inductive elements, wherein the transmitter coil comprises asymmetric conductor paths or windings with a longitudinal layout causing an asymmetric magnetic field.

15. The inductive proximity switch device according to claim 14, wherein at least one inductive element is coupled to a switchable current source configured to provide alternating current pulses to the inductive element to generate a magnetic stray field surrounding the inductive element, such that a current is induced in the inductive element during a subsequent relaxation of the magnetic stray field, when the switchable current source is switched off.

16. The inductive proximity switch device according to claim 15, wherein the switchable current source is configured to generate, using the transmitter coil, an alternating magnetic field with a frequency that does not significantly penetrate into a metal body present in the magnetic field.

17. The inductive proximity switch device according to claim 14, comprising at least one inductive element flown through by a pulse-shaped or a sinusoidal current, wherein the evaluation circuit is configured to evaluate a time characteristic of a voltage induced in the at least one inductive element after switching off the pulse-shaped or sinusoidal current.

18. The inductive proximity switch device according to claim 14, wherein sections of the conductor paths or windings of the transmitter coil comprise a larger diameter than other sections of the conductor paths or windings of the transmitter coil.

19. An inductive proximity switch device comprising:

a plurality of inductive elements disposed on a common substrate, the inductive elements arranged in one or more metalizing layers on the common substrate, the inductive elements comprising

at least one transmitter coil, and

at least one receiver coil; and

an evaluation circuit coupled to at least one of the plurality of the inductive elements, wherein the transmitter coil comprises conductor paths or windings having a first pitch in a first portion of the transmitter coil and a second pitch in a second portion of the transmitter coil, such that the transmitter coil generates an asymmetric magnetic stray field, wherein the first pitch is different from the second pitch, and the second portion is opposite the first portion.

22. An inductive proximity switch device comprising:

a plurality of inductive elements disposed on a common substrate, the inductive elements arranged in one or more metalizing layers on the common substrate, the inductive elements comprising

at least one transmitter coil, and

at least one receiver coil; and

an evaluation circuit coupled to at least one of the plurality of the inductive elements, wherein the evaluation circuit comprises a phase locked loop circuit for evaluation of frequency modulation.

23. The inductive proximity switch device according to claim 22, wherein the transmitter coil and the receiver coil are arranged in a manner such that a magnetic stray field generated by the at least one transmitter coil surrounds the at least one receiver coil inducing a voltage or current in the at least one receiver coil.

24. The inductive proximity switch device according to claim 23, wherein conductor paths or windings of the transmitter coil comprise a larger cross section than conductor paths or windings of the receiver coils.

25. The inductive proximity switch device according to claim 23, wherein the evaluation circuit is configured to evaluate output signals of the inductive elements that is integrated on the common substrate, and is configured to evaluate the induced voltage or current characteristics of the receiver coils for detecting objects comprising metals present in the magnetic stray field generated by the transmitter coil of the proximity switch device.

26. The inductive proximity switch device according to claim 23, wherein the evaluation circuit is configured to evaluate output signals of the inductive elements that is integrated on the common substrate, and is configured to evaluate the induced voltage or current characteristics of the receiver coils for differentiation between objects comprising different ferromagnetic metals or non-magnetic metals present in the magnetic stray field generated by the transmitter coil.

27. The inductive proximity switch device according to claim 23, wherein the evaluation circuit is configured to evaluate output signals of the inductive elements that is integrated on the common substrate, and is configured to evaluate the induced voltage or current characteristics of the receiver coils for differentiation between a presence of smaller metal bodies in a closer vicinity of the proximity switch device and larger metal bodies in a farther distance from the proximity switch device.

28. The inductive proximity switch device according to claim 22, wherein the transmitter coil and the receiver coil are configured such that they comprise the same inductance.

29. The inductive proximity switch device according to claim 22, further comprising a plurality of capacitor integrated on the common substrate, wherein the receiver coils are coupled with the capacitors to form LC oscillator circuits, each comprising an inductive element and an capacitive element, wherein the phase locked loop circuit is configured to perform frequency demodulation of a sum signal derived from an addition of output signals of the LC oscillator circuits.

30. The inductive proximity switch device according to claim 22, wherein the evaluation circuit further comprises an active rectifier circuit configured to convert a demodulator output of the phase locked loop circuit into a rectified signal.

31. The inductive proximity switch device according to claim 30, wherein the active rectifier circuit is coupled to a clock generator for synchronization of the rectified signal with a clock signal.

32. The inductive proximity switch device according to claim 30, wherein the evaluation circuit further comprises a threshold value detector configured to evaluate the rectified signal.