JP2001094174A - Magnetoresistance coupling circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily mount a magnetoresistance coupling circuit on a circuit substrate with a simple and small structure and with stable and reliable transmission of a signal without being thermally influenced, when the signal is transmitted between a plurality of electric circuit systems under an electrically isolated condition. SOLUTION: This magnetoresistance coupling circuit includes a first electric circuit system formed on a substrate, a second electric circuit system formed on another substrate as electrically isolated from the first system, and a magnetoresistance coupler for transmitting a signal from the first system to the second system in a noncontact manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method of transmitting a signal between a plurality of electric circuit systems provided on a substrate so as to be electrically insulated from each other in a non-contact manner by utilizing a magnetoresistance effect. The present invention relates to a magnetoresistive coupling circuit.

[0002]

2. Description of the Related Art Conventionally, for example, when a high-voltage motor drive system and a low-voltage control system coexist as in an electric vehicle, a motor is provided to protect the low-voltage system from surges in the high-voltage system. The drive system and the control system are connected to a reference voltage (normally GN
D) is provided electrically insulated so as not to be shared, and a control signal is transmitted from the control system to the motor drive system via a photocoupler or an insulating transformer.

[0003]

A problem to be solved is that a signal is transmitted from a first electric circuit system, which is electrically insulated from each other, to a second electric circuit system via a photocoupler. It is weak to heat itself, and cannot transmit signals properly depending on the temperature environment.

Further, when signals are transmitted from a first electric circuit system to a second electric circuit system, which are electrically insulated from each other, via an insulating transformer, the insulating transformer itself is large, and the electric power of each system is large. It is difficult to integrate the circuit into a circuit board on which the circuit is mounted, and the assembly becomes large and complicated. In addition, there is a problem that a DC signal cannot be transmitted because a change in current is detected.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of transmitting a signal between a plurality of electric circuit systems formed on a substrate and electrically insulated from each other in a non-contact manner. A first electric circuit system formed on the substrate so as to be able to perform the operation stably with high reliability and to be easily mounted on the substrate with a simple and small structure. And a second electric circuit system formed on the same substrate or another substrate while being electrically insulated from the first electric circuit system, and transmitting a signal from the first electric circuit system to the second electric circuit system. Non-contact magnetic coupling element (hereinafter referred to as magnetoresistive coupler)
Thus, a magnetoresistive coupling circuit is configured.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a magnetoresistive coupling circuit according to the present invention comprises a plurality of electric circuit systems 21, 22 provided on a substrate 1 forming a monolithic IC or a hybrid IC and electrically insulated from each other. ,..., 2n are transmitted to the magnetoresistive couplers 41, 42,.
(M = n-1) is used to perform the operation in a non-contact state. In the figure, 31, 32,..., 3n indicate main circuits in each system.

Each of the electric circuit systems 21, 22,.
Needless to say, even if they are not formed on the same substrate 1, they may be formed separately and independently on each dedicated substrate.

FIGS. 2 and 3 show a magnetoresistive coupler 4 (4
1, 42,..., 4m), in which a signal line 6 in a second electric circuit system provided electrically insulated from a signal line 5 in the first electric circuit system is shown.
The signal is directly transmitted using the magnetoresistive element 7.

[0009] It is formed into an IC by forming a thin film of a magnetoresistive element 7 via an insulating layer 8 so as to straddle the signal line 5 wired on the substrate 1. The signal line 6 is connected to both ends of the magnetoresistive element 7.
9 is a protective film for the magnetoresistive element 7.

The magnetoresistive element 7 has such a characteristic that the resistance value is largely changed by slightly applying a magnetic field so that the lines of magnetic force act in the plane direction. FIG. 5 shows the characteristics of the rate of change in resistance of the magnetoresistive element 7 with respect to the applied magnetic field. The magnetoresistive element 7 is resistant to heat, and the characteristics of the resistance change due to the applied magnetic field are stable without being thermally affected.

In the above-described structure, when no current flows through the signal line 5, the magnetoresistive element 7
Have a high resistance, and the signal line 6 is in a small current state (OFF state). When the current I flows through the signal line 5, a magnetic field H as shown in FIG. 4 is generated around the signal line 5, and the resistance value is greatly changed by the magnetic force lines acting in the surface direction of the magnetoresistive element 7. The resistance becomes low, and the signal line 6 is brought into a state of high current (on state).

The on / off state of the signal line 6 according to the change in the resistance value of the magnetoresistive element 7 can be set by circuit constants such as the number of turns of the signal line 6 and current.

By supplying or not supplying a current to the signal line 5 in the first electric circuit system, on / off signals can be transmitted to the second electric circuit system in a non-contact manner.
The transmission can be performed stably without being affected by heat.

At this time, since the strength of the generated magnetic field H when the current I flows through the signal line 5 is inversely proportional to the distance from the signal line 5, the magneto-electric conversion in the magnetoresistive element 7 is performed by microfabrication using IC manufacturing technology. Sensitivity can be sufficiently increased.

FIG. 6 shows another example of the configuration of the magnetoresistive coupler 4 '. In this case, when transmitting an on / off signal in accordance with a change in the resistance value of the magnetoresistive element 7, its resistance value is reduced. The change of is taken out using a bridge circuit.

Here, two magnetoresistive elements (GMR) 71, 72 are provided for the signal line 5, and the reference resistance Rs
1 and Rs2 to form a bridge circuit, and a signal line 5
When no current is flowing through the circuit, an equilibrium state is established.

In this bridge circuit, as shown in FIG. 7, when a current I flows through the signal line 5 (a in FIG. 7), the resistance of each of the magnetoresistive elements GMR71 and GMR72 changes from the high resistance HR to the high resistance HR, respectively. The state changes to the state of low resistance LR (b in the figure), whereby the bridge circuit becomes unbalanced and A
The potential Va at the point is lower than the reference level (zero potential), and the potential Vb at the point B is higher than that (FIG. 3C).

Therefore, the transmission state of the on / off signal from the first electric circuit system can be detected by observing the potential states at points A and B in the second electric circuit system.

FIG. 8 shows the magnetoresistive coupler 4 '(4
1 ′, 42 ′,..., 4m ′)
1, 2,..., 2n are shown when signals are transmitted. Here, by looking at the potential state between A and B of the bridge circuit, the ON signal is transmitted from the first electric circuit system to the second electric circuit system when the potential state changes from 0 to a high level. I have to.

[0020]

As described above, in the magnetoresistive coupling circuit according to the present invention, the first electric circuit system formed on the substrate,
A second electric circuit system formed on the same substrate or another substrate and electrically insulated from the first electric circuit system;
And a magneto-resistive coupler that transmits signals from the electric circuit system to the second electric circuit system in a non-contact manner. It can be performed stably with the nature.

In particular, according to the present invention, the magnetoresistive coupler can be easily integrated into an IC, can be integrated on a substrate together with a plurality of electric circuit systems, and can be compactly mounted as a monolithic IC or a hybrid IC. It has the advantage that it can be done.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a magnetoresistive coupling circuit according to the present invention.

FIG. 2 is a front sectional view showing a configuration example of a magnetic coupler according to the embodiment.

FIG. 3 is a plan view of a magnetic coupler according to one configuration example.

FIG. 4 is a front cross-sectional view showing a state where lines of magnetic force act in a plane direction of a magnetoresistive element by a magnetic field generated when a current flows through a signal line.

FIG. 5 is a diagram illustrating characteristics of a rate of change in resistance with respect to an applied magnetic field of a magnetoresistive element.

FIG. 6 is a bridge circuit diagram showing another configuration example of the magnetic coupler.

FIG. 7 is a time chart showing characteristics of various states of change in the bridge circuit.

FIG. 8 is a circuit configuration diagram showing another embodiment according to the present invention when a magnetic coupler having a bridge configuration is used.

[Explanation of symbols]

 , 2n Electrical circuit system 31, 32, ..., 3n Main circuit 4 (41, 42, ..., 4m) Magnetoresistive coupler 4 '(41', 42 ', ..., 4m') Magnetoresistance Coupler 5 Signal line of first electric circuit system 6 Signal line of second electric circuit system 7, 71, 72 Magnetic resistance element 8 Insulating layer 9 Protective film

Claims (4)

[Claims] A first electric circuit system formed on a substrate, and a second electric circuit system formed on the same substrate or another substrate and electrically insulated from the first electric circuit system. ,
A magnetoresistive coupling circuit comprising: a magnetoresistive coupler for transmitting a signal from a first electric circuit system to a second electric circuit system in a non-contact manner. 2. A magnetoresistive coupler, comprising: a magnetoresistive element disposed so as to straddle a signal line of a first electric circuit system in a non-contact manner and connected to a signal line of a second electric circuit system;
2. The magnetoresistive coupling circuit according to claim 1, wherein a signal is transmitted by a change in resistance of the magnetoresistive element when a current flows through a signal line of the first electric circuit system. 3. A first electric circuit comprising a bridge circuit constituted by a magnetoresistive element and a reference resistor disposed so as to straddle a signal line of a first electric circuit system in a non-contact manner. 2. The magnetoresistive device according to claim 1, wherein the signal is transmitted by an unbalanced output of the bridge circuit when the resistance of the magnetoresistive element changes due to a current flowing through the signal line of the circuit system. Coupling circuit. 4. A magnetoresistive element according to claim 2, wherein a thin film of a magnetoresistive element is formed on a signal line of the first electric circuit system wired on the substrate via an insulating layer. The ultimate circuit.