JPH04165517A - Interface circuit using electromagnetic induction coupling - Google Patents

Abstract

PURPOSE:To always hold a period of a binarized output and a duty ratio constant irrespective of whether a magnetic flux is large or small by inputting a coil induced voltage whose level is shifted by a first capacitor to a binarizing circuit part having a threshold voltage of half of a power supply voltage and binarizing it. CONSTITUTION:An induction voltage induced in a coil 10 is subjected to voltage doubler half-wave rectification and a capacitor C2 is charged with a voltage Vcc of two folds of the induction voltage. In this case, since a threshold voltage of a binarizing circuit part 14 is Vcc/2 which becomes half of the power supply voltage Vcc, when an input voltage Vin from a (b) point exceeds, for instance, the threshold voltage Vcc/2, a binarized output Fout becomes an H level, and when the said input voltage is below the threshold Vcc/2, the binarized output Fout becomes an L level, and a binarized square wave output is generated. Accordingly, a zero crossing point in the induction voltage of the coil 10 becomes the same since the frequency is constant, even if amplitude is varied by a magnetic flux and the induction voltage becomes small. In such a way, a binarized output whose period and duty ratio become constant can be obtained irrespective of a variation of the magnetic flux for working on the coil.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an interface circuit for a data carrier that receives data writing or data reading by electromagnetic inductive coupling with a league writer, and in particular, relates to an interface circuit for a data carrier that receives data writing or data reading by electromagnetic inductive coupling with a league writer. The present invention relates to an interface circuit using electromagnetic inductive coupling that generates its own power supply voltage from a signal voltage, binarizes the induced voltage, and performs digital signal processing.

[Prior Art] Conventionally, an electromagnetic inductive coupling method has attracted attention as a non-contact coupling method for data carriers. Since the electromagnetic inductive coupling method is a non-contact method, there is no problem of poor contact due to dirt or rust as with electrical connections, and the signal voltage induced in the coil of the data carrier is rectified and smoothed to provide its own power source. This has the advantage that unlike the optical coupling method, there is no need to provide a battery power source that requires replacement for the data carrier.

For this reason, a data carrier using electromagnetic inductive coupling includes a power supply circuit section 12 that rectifies and smoothes the signal voltage induced in a coil 10 to generate its own DC power supply voltage, and a power supply circuit section 12, as shown in FIG. 4, for example. A binarization circuit 1 operates upon receiving power supply voltage Vcc from the unit 12, and binarizes the signal voltage induced in the coil 10 to generate a digital output Foul.
4 is provided.

To explain in more detail, the power supply circuit section 12 includes a coil 10
The induced voltage at both ends of is full-wave rectified by diodes Di and D2, and capacitor C1 is charged and smoothed, and the power supply voltage Vc
It is creating c.

The binarization circuit 14 uses, for example, a CMO8 type IC, and binarizes the coil induced voltage into a rectangular signal using Vcc/2, which is half of the power supply voltage Vcc, as a threshold voltage.

[Problems to be Solved by the Invention] However, in such a conventional interface circuit using electromagnetic inductive coupling, as shown in FIG.
The amplitude of the coil induced voltage at point a input to the binarization circuit 14 changes depending on the magnitude of the magnetic flux φ shown by the broken line, and Vcc/2
When binarized at the threshold voltage of Therefore, there is a problem that stable data processing cannot be performed with such a binary output.

The present invention has been made in view of such conventional problems, and provides an interface circuit using electromagnetic inductive coupling that can always keep the period and duty ratio of binary output constant regardless of the magnitude of magnetic flux. The purpose is to provide

[Means for Solving the Problems] To achieve this object, the present invention is configured as follows. In addition, the reference numerals in the drawings of the embodiments are also shown.

First, the present invention includes a power supply circuit unit 12 that rectifies an AC signal voltage induced in a coil 10 by electromagnetic induction coupling to generate its own DC power supply voltage, and a binarization circuit unit 14 that binarizes the coil induced voltage. The target is an interface circuit using electromagnetic inductive coupling.

As such an interface circuit, the first invention of the present application includes a first rectifying element D that rectifies the induced voltage of the coil 1.0.
1, a first capacitor C1 that smoothes the rectified output of the first rectifying element D1, and a first capacitor C1 that is connected in parallel to the first rectifying element D1, and the charging voltage of the first capacitor C1 is added to the induced voltage of the coil. a second rectifying element D2 that rectifies the voltage;
A binarization circuit section that includes a second capacitor C2 that smoothes the rectified output of the second rectifying element D2, and that converts the coil induced voltage level-shifted by the first capacitor C1 into a binarization circuit section that has a threshold voltage that is half the power supply voltage Vcc. 14 and binarized.

Further, in the interface circuit as the second invention of the present application, the power supply circuit section 12 includes a first capacitor C1 and a second capacitor C1.
a voltage doubler smoothing circuit 16 in which capacitors C2 are connected in series, and a first rectifying element D1 that rectifies the positive half-cycle induced voltage of the coil 10 to charge the first capacitor C1.
and a first rectifying element D that rectifies the negative half-cycle induced voltage of the coil 10 to charge the second capacitor C2.
2 are provided, and the coil induced voltage level-shifted by the second capacitor C2 is transferred to the first and second rectifying elements D1 . ．． D2
It is characterized in that it is taken out from the connection point of and binarized by a binarization circuit section 14 having a threshold voltage that is half the power supply voltage.

Furthermore, in the interface circuits of the first and second inventions, the power supply circuit section 12 and the binarization circuit section 14 are incorporated into a data carrier that receives data writing or reading by electromagnetic inductive coupling between the reader/titer. It is characterized by

According to the interface circuit using electromagnetic inductive coupling according to the present invention having such a configuration, even if the amplitude of the induced voltage changes due to the change in the strength of the magnetic flux acting on the coil, the induced voltage can be directly connected to the power supply. By performing a level shift that increases by Vcc/2, which is half the voltage, it is possible to match the zero cross level of the induced voltage with the threshold level of the binarization circuit, and therefore It is possible to always perform binarization with a constant cycle and duty ratio even if the frequency changes.

[Embodiment] FIG. 1 is an embodiment circuit diagram showing an embodiment of the present invention.

In FIG. 1, a coil 10 is wound around a core 18 with a predetermined number of turns. As the core 18, a pot-type core 18 is used, which has a single annular coil groove opened at one end of a disc-shaped member.

A magnetic flux is applied to the coil 10 wound around the core 18 by an alternating magnetic field obtained by energizing a predetermined frequency signal to a magnetic inductive coupling unit made of the same core and coil provided on the reader/writer side, for example. An induced voltage corresponding to the strength of the magnetic flux is generated between the coil terminals 20 and 22.

A power supply circuit section 12 is provided following the coil 10. In the power supply circuit section 12, a terminal 20 of the coil 10 is connected to the anode side of a diode D2 as a first rectifying element via a first capacitor C1, and a second terminal used for smoothing is connected to the cathode side of the diode D2. capacitor C2 is connected.

A ground line GND is drawn out from the terminal 22 of the coil 10, and the anode side of a diode D1 as a first rectifying element is connected to the terminal 22 side, and the cathode side is connected to the connection point between the anode of the diode D2 and the capacitor C1. are doing.

14 is a binarization circuit section, for example, a CMO8 type IC is used, and the power supply voltage +V generated by the power supply circuit section 12 is
It operates by receiving the supply of cc. The induced voltage of the coil 10 obtained via the capacitor C1 in the power supply circuit section 12 is inputted to the binarization circuit section 14 as Vin.

Next is the 1st TI! The operation of the embodiment J will be explained with reference to the signal waveform diagrams in FIGS. 2A and 2B. Here is the 2nd A.

The signal waveform diagram in Figure 2B shows the induced voltage of the coil 10 at point a in Figure 1, and the input voltage Vin to the binarization circuit section 14 at point b.
, shows the output Font of the binarization circuit 14 and the power supply voltage Vcc.

When the coil 10 receives magnetic flux due to electromagnetic inductive coupling at a predetermined frequency from the reader/writer side, when the magnetic flux φ is strong, an induced voltage as shown in the waveform 24 in FIG. 2A (a) is obtained, while on the other hand, the magnetic flux φ is weak. In this case, a signal voltage shown by waveform 26 in FIG. 2B is induced.

The induced voltage induced in the coil 10 is applied to the diodes Di and D.
2. Voltage doubler half-wave rectified by C1 and C2 and capacitor C
2 to a voltage Vcc twice the induced voltage. When charging the capacitor C2, the capacitor C1 is charged to Vec/2, which is half of the power supply voltage Vcc. That is, in a half cycle when the terminal 22 is set to (+), the capacitor C1 is charged to V CC / 2 + through the diode D1; and in the next half cycle when the terminal 20 is set to (+), the coil 10 is charged.
The capacitor C2 is charged with Vcc, which is the sum of the capacitor C1 and the capacitor C1.

Therefore, the coil induced voltage at point a shown in Figures 2A and 2B (a) undergoes a level shift that is increased by the charging voltage Vcc/2 of the capacitor CI.
) is expressed as the voltage at point b. Vcc at this point b
The shift voltage whose level has been increased by /2 is input to the binarization circuit section 14.

Since the threshold voltage of the binarization circuit unit 14 is VCC/2, which is half of the power supply voltage Vcc, the input voltage Vin from point b
For example, when the voltage exceeds the threshold voltage Vcc/2, the binary output Foul becomes H level, and when it falls below the threshold voltage Vcc/2, the binary output Foul becomes L level.
A binarized rectangular wave output as shown in Figure B (C) is produced. That is,
Binarization in which the zero cross point of the coil induced voltage at point a in FIGS. 2A and 2B (a) is detected and the output is inverted has essentially been performed. Even if the amplitude changes due to the magnetic flux and the induced voltage becomes smaller, the zero-crossing point of the induced voltage in the coil 10 remains the same as shown in Figure 2B because the frequency is constant, and therefore, as shown in Figure 2B (C). There is a one-to-one relationship in which the on time t1 and the off time t2 are both equal, and the period T determined by tl + t2 is constant,
Moreover, a stable binary output with a duty ratio of 50% can be obtained.

Further, in the embodiment shown in FIG. 1, the center-tapped coil 10 in the conventional example shown in FIG. 4 is not required, and the number of turns of the coil 10 can be halved. If the number of turns of the coil 10 can be reduced in this way, the stray capacitance of the coil 10 can be reduced, and as a result, the frequency band that can be transmitted in electromagnetic inductive coupling can be made wider, thereby reducing signal waveform distortion and loss. can.

FIG. 3 is an embodiment circuit diagram showing another embodiment of the present invention corresponding to the second invention of the present application, which is characterized by using a power supply circuit section based on voltage doubler full-wave rectification.

In FIG. 3, the power supply circuit section 12 has a first circuit for voltage doubler smoothing.
A voltage doubler smoothing circuit 16 is provided in which a capacitor C1 and a second capacitor C2 are connected in series.

The capacitor C1 of the voltage doubler rectifier circuit is charged by the rectified output of the positive half-cycle induced voltage induced in the coil 10 by the diode D1 as the first rectifier, with the terminal 20 side being positive. Further, the capacitor C2 is charged by the rectified output of a half cycle of the negative electromotive force induced in the coil 10 by the diode D2 as a second rectifying element, with the terminal 22 side being positive. Therefore, C1,
C2 is charged to the induced voltage of the coil, and the power supply voltage Vcc becomes twice the induced voltage of the coil.

For the binarization circuit section 14, the terminal 20 of the coil 10,
That is, the signal voltage at the connection point of diodes D1 and D2 is Vin
is entered as .

Even in the embodiment shown in FIG. 3, the input voltage Vin to the binarization circuit section 14 is the charging voltage of the capacitor C2 provided in the voltage doubler smoothing circuit 16, that is, half of the power supply voltage VCC.
The voltage has been leveled up by C/2, and therefore, as shown in the signal waveform diagrams of Figures 2A and 2B,
The zero crossing point of the induced voltage can be detected by the binarization circuit section 14 and binarized. Therefore, coil 10
Even if the magnetic flux acting on the magnetic flux changes, the period T and duty ratio of the output Fouj of the binarization circuit section 14 can always be kept constant.

It should be noted that although the above-mentioned embodiment was an example of an interface circuit used in a data carrier using electromagnetic inductive coupling, the present invention is not limited to data carriers.
It can be applied as is to any suitable electromagnetic inductive coupling interface circuit.

[Effects of the Invention] As explained above, according to the present invention, the binarization circuit produces a binarized output whose period and duty ratio are constant regardless of changes in the magnetic flux acting on the coil due to electromagnetic inductive coupling. Even if there is a change in the amplitude of the induced voltage depending on fluctuations in magnetic flux, digital data processing can be performed without errors due to the always stable binary output.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention; Figs. 2A and 2B are signal waveform diagrams of the embodiment of Fig. 1; Fig. 3 is a circuit diagram of another embodiment of the invention; Fig. 4 is a circuit diagram of the prior art. Circuit diagram; FIG. 5 is a signal waveform diagram of a conventional circuit. [Explanation of symbols] 10: Coil 12: Power supply circuit section 14: Binarization circuit section 16: Voltage doubler smoothing circuit 18: Core 20.22: Coil terminal Dl: Diode (first rectifying element) D2: Diode ( (Second rectifying element) C1: First capacitor C2: Second capacitor Patent applicant Tokimec Co., Ltd.

Claims (3)

[Claims] (1) A power supply circuit unit (12) that rectifies a signal voltage of a desired frequency induced in the coil (10) by electromagnetic inductive coupling to generate its own DC power supply voltage, and a binary value that binarizes the coil induced voltage. In the interface circuit using electromagnetic inductive coupling, the power supply circuit section (12) includes: a first rectifier element (D1) that rectifies the induced voltage of the coil (10); , a first capacitor (C1) that smoothes the rectified output of the first rectifier (D1), and a first capacitor (C1) that is connected in parallel to the first rectifier (D1) and is connected to the induced voltage of the coil. a second rectifying element (D2) that rectifies the voltage obtained by adding the charging voltage of C1); and a second capacitor (C2) that smoothes the rectified output of the second rectifying element (D2), The coil induced voltage level-shifted by the first capacitor (C1) is input to the binarization circuit section (14) having a threshold voltage half of the power supply voltage (Vcc) and binarized. Interface circuit using electromagnetic inductive coupling. (2) A power supply circuit unit (12) that rectifies a signal voltage of a desired frequency induced in the coil (10) by electromagnetic inductive coupling to generate its own DC power supply voltage, and a binary value that binarizes the coil induced voltage. In the interface circuit using electromagnetic inductive coupling, the power supply circuit section includes a first capacitor (C1) and a second capacitor (C2).
a voltage doubler smoothing circuit (16) connected in series, and a first rectifying element (D1) that rectifies the positive half-cycle induced voltage of the coil (10) to charge the first capacitor (C1). and a first one that rectifies the negative half-cycle induced voltage of the coil (10) to charge the second capacitor (C2).
rectifying element (D2), and transmits the coil induced voltage level-shifted by the second capacitor (C2) to the first and second rectifying element (D2).
An interface circuit using electromagnetic inductive coupling, characterized in that the signal is taken out from the connection point (1, D2) and binarized by the binarization circuit section (14) having a threshold voltage half the power supply voltage. (3) In the interface circuit using electromagnetic inductive coupling according to claim 1 or 2, the power supply circuit section (12) and the binarization circuit section (14),
An interface circuit using electromagnetic inductive coupling, characterized in that it is incorporated into a data carrier that receives data writing or reading by electromagnetic inductive coupling with a reader/writer.