Magnetic coupling circuit-driving system

• US 5,610,384 A
• Filed: 09/28/1995
• Issued: 03/11/1997
• Est. Priority Date: 09/30/1994
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Goto, Yuichi
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): Le, Thien Minh
• Application Number:
  US08/534,939
• Time in Patent Office: 530 Days
• Field of Search: 235/439, 235/449, 235/487, 235/441, 235/492, 235/448, 235/435, 307/300, 307/307
• US Class Current: 235/435
• CPC Class Codes: G06K 7/082 using inductive or magnetic sensors

Abstract

To create a critical coupling state of coils provided in the first and second series resonance circuits, the output resistances of circuits for driving the resonance circuits are adjusted, or the distance between the coils is adjusted. A sine wave AC signal of a frequency identical to the resonance frequency of the resonance circuits is applied to one of the resonance circuits in accordance with transmission data. When one of the coils has been excited, the other coil electromagnetically coupled with the excited coil is also excited, thereby generating magnetic fields of the same intensity and different phases. The coils which constitute a magnetic coupling circuit can be driven by a power lower than that required in the conventional case, thereby transmitting carrier waves of a necessary intensity.

Claims

1. A magnetic coupling circuit-driving system comprising:

a magnetic coupling circuit including a first resonance circuit having a first coil, and a second resonance circuit having a second coil and a resonance frequency identical to that of the first resonance circuit;

first and second driving circuits for driving the first and second resonance circuits, respectively; and

switching means for supplying an AC signal of a frequency identical to the resonance frequency, to one of the first and second resonance circuits in accordance with input data;

wherein the first and second coils generate magnetic fields having the same intensity each other and different phases.

2. The system according to claim 1, wherein the second driving circuit has means for inverting the AC signal from the switching means, and the inverted AC signal drives the second resonance circuit.

3. The system according to claim 2, wherein the first and second resonance circuits are series resonance circuits each including a capacitor and both opposite terminals, and said first and second driving circuits have means for applying a signal voltage between the both opposite terminals of the first resonance circuit, and applying another signal voltage with a phase opposite to that of the first-mentioned signal voltage, between the both opposite terminals of the second resonance circuit.

4. The system according to claim 2, wherein each of the first and second resonance circuits is a parallel resonance circuit including a capacitor.

5. The system according to claim 1, wherein the positions of the first and second coils are adjusted such that magnetic fields having phases shifted by 90°

from each other are generated at the first and second coils.

6. The system according to claim 1, wherein the first and second driving circuits have output resistances, respectively, and the output resistances are adjusted such that magnetic fields having phases shifted by 90°

from each other are generated at the first and second coils.

7. The system according to claim 1, further comprising a non-contact type data record medium, having third and fourth coils magnetically coupled with each other, for receiving carrier waves transmitted from magnetic fields generated at the first and second coils, each of the third and fourth coils having an axis, and each of the first and second coils having an axis, the distance between the axes of the first and second coils being set wider than the distance between the axes of the third and fourth coils so that magnetic field having the same intensity and phases shifted from each other are generated at the first and second coils of the resonance circuits.

8. A method for driving a magnetic coupling circuit formed by magnetically coupling a first coil which constitutes a first resonance circuit, with a second coil which constitutes a second resonance circuit, to thereby generate magnetic fields of a predetermined intensity at the coils and transmit carrier waves having phases varied in accordance with transmission data, comprising the steps of:

adjusting the first and second resonance circuits such that magnetic fields generated at the coils have the same intensity and different phases; and

exciting one of the first and second coils in accordance with the transmission data to excite the other coil by mutual induction between them.

9. The method according to claim 8, further comprising:

adjusting the first and second resonance circuits such that they have the same resonance frequency;

exciting, by means of a signal having a frequency identical to the resonance frequency, one of the first and second coils which constitute the first and second resonance circuits, in accordance with the transmission data, thereby exciting the other coil by mutual induction between them and transmitting carrier waves having phases varied in accordance with transmission data.

10. The method according to claim 9, wherein the exciting step includes the step of supplying one of the first and second resonance circuit with one of a first signal having a predetermined amplitude and a frequency identical to the resonance frequency, and a second power signal having a phase shifted by 180°

from the phase of the first power signal, in accordance with the transmission data, thereby exciting one of the first and second coils and exciting the other coil by mutual induction between them.

11. The method according to claim 8, wherein the adjusting step includes the step of adjusting the positions of the first and second coils such that the first and second resonance circuits reach a predetermined coupling state in which they generate magnetic fields with a phase difference of 90°

.

12. The method according to claim 8, wherein the exciting step includes the step of supplying the non-contact type data record medium with carrier waves having their phases varied in accordance with the transmission data;

and the adjusting step includes the step of setting the distance between axes of the first and second coils wider than the distance between axes of magnetically coupled third and fourth coils employed in the non-contact type data record medium, such that the first and second resonance circuits reach a predetermined coupling state in which they can generate magnetic fields with a predetermined intensity and different phases.