JPH0785402A - Rotary transformer - Google Patents

Abstract

PURPOSE:To reduce the amplitude of the output voltage of a recording amplifier easily in a simple constitution thereby to lower the voltage of the power source of the recording amplifier without increasing the voltage of the power source even when the frequency of a recording signal becomes high during recording. CONSTITUTION:A middle tap 1c is connected to a coil 1a of a stator of a rotary transformer 1 so that the ratio of the number of turns of the coil 1a the stator to a coil 1b of a rotor is, for instance, 1. When the rotary transformer 1 is used in a magnetic recording/reproducing apparatus, the middle tap 1c is connected to a recording amplifier 5, thereby the amplitude of the output voltage of the recording amplifier in recording is made smaller than in a conventional manner easily in a simple constitution. Accordingly, the voltage of the power source for the recording amplifier in recording is naturally decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary transformer used in a magnetic recording / reproducing apparatus such as a video tape recorder (hereinafter abbreviated as VTR) and a digital audio tape recorder (hereinafter abbreviated as DAT).

[0002]

2. Description of the Related Art Generally, in a magnetic recording / reproducing apparatus such as a VTR, a helical scan system is used in which a head is rotated to perform magnetic recording or reproduction.

Such a helical scan type VTR
In the reproducing process of the apparatus, for example, at least two heads are mounted on a rotating drum, and the heads rotate on a magnetic recording medium on which magnetic recording has been performed so as to helically slide in the traveling direction. , A signal is obtained from this magnetic recording medium, and the obtained signal is amplified at a predetermined level by an electronic circuit such as a reproduction preamplifier and reproduced through a contactless rotary transformer (hereinafter referred to as a rotary transformer). Playback is performed by supplying to the circuit. Also in the case of recording by the device, a signal to be recorded is supplied through a rotary transformer, and a voltage / current necessary for recording is supplied to the head by an electronic circuit such as a recording amplifier, and at the same time a recording medium is recorded. Magnetic recording is performed by rotating the head so as to slide helically.

As described above, in the magnetic recording / reproducing apparatus,
A rotary transformer has been conventionally used to couple a video head with an amplifier for reproduction / recording (hereinafter referred to as an amplifier). The rotary transformer is excellent in terms of noise, durability, or reliability. It has a function.

3 and 4 show an electric circuit of a conventional rotary transformer, FIG. 3 is an equivalent circuit per groove of the rotary transformer, and FIG. 4 is a rotary transformer shown in FIG. 1 connected to a magnetic recording / reproducing apparatus. It is a circuit diagram which shows an example.

In FIG. 3, the rotary transformer 10
As is well known, is composed of a stator fixed to a rotating drum and the like, and a rotor that rotates together with the magnetic head, each of which is connected to a reproducing circuit, a magnetic head or the like via a lead wire. Further, the stator and the rotor are electromagnetically coupled to each other to transmit signals during reproduction and recording.

The rotary transformer 10 is provided with terminals a and b arranged on the stator side connected to a reproducing amplifier or recording amplifier, and terminals c and d arranged on the rotor side connected to the magnetic head. A coil is connected between these terminals (between a and b, between cd).

The stator and rotor coils forming the rotary transformer 10 have a winding ratio of the rotary transformer (the number of windings on the stator side / the number of windings on the stator side) in terms of the amplifier noise of the reproducing amplifier during reproduction and the reproduction output level of the magnetic head. The number of turns of the coil on the rotor side) is set to about 2, for example.

Generally, the leakage inductance Ll of the rotary transformer 10 is preferably smaller than the inductance of the magnetic head (1/4 times or less), and the exciting inductance Li is larger than the inductance of the magnetic head (at least 4 times). Above) is desirable.

Therefore, when the rotary transformer 10 thus constructed is connected to, for example, a magnetic recording / reproducing apparatus, the input circuit of the reproducing amplifier 40 as shown in FIG.
The inductance of the rotary transformer 10, the internal inductance of the magnetic head 90, the input capacitance of the reproducing amplifier 40, and the adjusting capacitor 60 constitute a resonance circuit, and normally, the resonance frequency is set near the upper limit of the FM luminance signal frequency to reproduce. I try to improve the sensitivity.

The operation of the magnetic recording / reproducing apparatus using the rotary transformer 10 will be described below.

First, at the time of reproduction, the terminal b is connected to the reference potential point by the switch 80 shown in FIG. 4 and connected to the circuit of the reproduction system. Then, the reproduction signal taken out from the magnetic recording medium (not shown) by the magnetic head 90 is electromagnetically transmitted from the rotor of the rotary transformer 10 to the stator, and to the terminals a and b provided on the stator side. Supplied with.

Thereafter, this reproduction signal is supplied to the reproduction amplifier 40 via the capacitor 60, amplified by a predetermined amplification factor, and output from the output terminal 20 to a reproduction circuit stage (not shown) for reproduction.

On the other hand, during recording, the switch 8 is used.
The terminal b is disconnected from the reference potential point by 0, and the recording power supply voltage RECVcc is further supplied through the diode 70 to form a recording system circuit, and the recording signal to be supplied is supplied to the recording amplifier 50 through the input terminal 30. To be done. The recording amplifier 50 supplies the magnetic head 90 with the voltage and current required for recording. The current at this time is supplied to the magnetic head 90 as the optimum recording current I so that the maximum reproduction output can be obtained.

After that, the same recording channel I is supplied from the recording amplifier 50 to the magnetic head 90 via the rotary transformer 10 using the same channel of the rotary transformer 10 as in the reproduction, and the magnetic head 90 does not show the recording current I. A recording signal is magnetically recorded on the magnetic recording medium.

By the way, the output voltage amplitude of the recording amplifier 50 at this time is obtained by multiplying the output current of the recording amplifier by the impedance seen from the stator side, where Z is the impedance of the magnetic head 4. That is,

## EQU1 ## I / 2 × 2 × 2 × Z = 2IZ.

Similarly, when the winding ratio of the rotary transformer is n, the output voltage amplitude of the recording amplifier 50 is nIZ.

When the inductance of the magnetic head 90 is L and the frequency is f, the magnetic head 9 is
The impedance of 0 is

## EQU00002 ## Z.apprxeq.2.pi.fL, that is, the output voltage amplitude of the recording amplifier 50 with respect to the turn ratio n of the rotary transformer 10 is

## EQU3 ## nIZ = 2nπfIL.

Thus, the output amplitude of the recording amplifier 50
Since nIZ = 2nπfIL is proportional to the frequency, the higher the frequency of the recording signal, the higher the power supply voltage RECV of the recording amplifier 4.
There is a problem that cc becomes large.

[0020]

As described above, the conventional rotary transformer has a problem that the power supply voltage of the recording amplifier increases as the frequency of the recording signal during recording increases.

Therefore, the present invention has been made in view of the above problems. Even when the frequency of the recording signal at the time of recording becomes high, the power source voltage of the recording amplifier is not increased and the configuration is simple. Another object of the present invention is to provide a rotary transformer capable of reducing the output voltage amplitude of the recording amplifier to reduce the power supply voltage.

[0022]

A rotary transformer according to the present invention is composed of a stator and a rotor, and electromagnetically coupled by windings respectively provided on the stator and the rotor to transmit signals to each other. In a magnetic head connected to the rotor winding, an intermediate tap provided on the stator winding, a reproducing circuit connected to one end of the stator winding, and a recording circuit connected to the intermediate tap. The stator winding is connected to the other end of the stator winding, and the other end is connected to a reference potential point at the time of reproducing operation to utilize the space between both ends of the stator winding as the stator winding, and is switched to an open state at the time of recording. The intermediate tap and the switching means for switching between the one ends so as to use it as the stator winding.

[0023]

In the present invention, by using the intermediate tap only during recording, reproduction can be performed with the conventional configuration during reproduction, and only the winding ratio of the rotary transformer during recording can be reduced during recording.

[0024]

EXAMPLES Examples will be described with reference to the drawings. 1 and 2 show an embodiment of a rotary transformer according to the present invention, FIG. 1 is a diagram showing an equivalent circuit of the rotary transformer, and FIG. 2 shows the rotary transformer shown in FIG. 1 used in a magnetic recording / reproducing apparatus. It is a circuit diagram which shows a case.

As shown in FIG. 1, the rotary transformer 1
Is composed of a stator fixed to a rotating drum (not shown) and a rotor that rotates together with the magnetic head. Each is connected to a reproducing circuit or a magnetic head via a lead wire. There is. Further, as is well known, the stator and the rotor are electromagnetically coupled to each other so that signals can be transmitted during reproduction and recording.

Further, like the rotary transformer of the prior art, terminals a and b arranged on the stator side connected to the reproducing amplifier or recording amplifier, and terminals c arranged on the rotor side connected to the magnetic head, d and the coils 1a and 1b are connected between these terminals (between a and b, between cd), respectively.

The stator side coil 1a is provided with an intermediate tap 1c which is a feature of this embodiment, and this intermediate tap 1c is connected to a terminal e so as to be connected to the recording amplifier 5.

Further, the coils 1a and 1b of the stator and rotor forming the rotary transformer 1 have a winding ratio of the rotary transformer (coil on the stator side) from the viewpoint of the amplifier noise of the reproduction amplifier and the reproduction output level of the magnetic head during reproduction. 1a turns / rotor side coil 1b turns)
Is set to be, for example, about 2, the number of turns of the stator-side coil 1a is 4T, the number of turns of the rotor-side coil 1b is 2T, and the intermediate tap 1c is, for example, (between terminals a and e). (Number of coil turns) and (terminal ec
The number of turns is 1: 1 and the winding ratio is 1: 1.

By the way, when the rotary transformer 1 having such a structure is used in, for example, a magnetic recording / reproducing apparatus, it is connected as shown in FIG.

For example, in the figure, a reproduction amplifier 4 and a resonance capacitor 6 are provided at a terminal a provided on the stator of the rotary transformer 1 for outputting a reproduction signal from a reproduction signal output terminal 2 during reproduction. It is provided.

Further, the coil 1a of the stator has an intermediate tap 1 so that the number of turns of the coil 1a is halved.
c is connected and connected to a terminal e to which a recording signal is input by being drawn out. At the time of recording, a recording amplifier 5 for supplying an optimum recording current I to the magnetic head 9 is connected to this terminal e in order to record the recording signal inputted from the recording signal input terminal 3.

Further, a switch 8 for selecting and switching a circuit at the time of recording or reproducing is provided at the terminal b of the stator, and a recording voltage RECVcc is applied via a diode 7 at the time of recording. It is designed to be used.

On the other hand, terminals c and d provided on the rotor of the rotary transformer 1 are provided with a magnetic head 9 for recording on or reproducing from a magnetic recording medium (not shown). The reproduction signal taken out from the magnetic recording medium is supplied to the reproduction system circuit by the electromagnetic coupling of the rotary transformer 1 and reproduced, and the recording signal amplified by the recording amplifier 5 at the time of recording is the intermediate tap 1c. Further, it is supplied to the magnetic head 9 through the rotary transformer 1 and recorded on the magnetic recording medium.

Next, the operation of the magnetic recording / reproducing apparatus having the rotary transformer as described above will be described in detail with reference to FIGS. First, at the time of reproduction, FIG.
The magnetic recording / reproducing apparatus having the rotary transformer 1 according to the present embodiment has the same performance as the magnetic recording / reproducing apparatus as the related art shown in FIG.

That is, the terminal b is connected to the reference potential point by the switch 8 shown in FIG. 2 to be connected to the circuit of the reproducing system, and the reproducing operation is carried out by the magnetic head 9 from the magnetic recording medium (not shown). The signal is electromagnetically transmitted from the rotor of the rotary transformer 1 to the stator,
It is supplied to the terminals a and b provided on the stator side.

Thereafter, this reproduction signal is supplied to the reproduction amplifier 4 via the capacitor 6, amplified by the reproduction amplifier 4 at a predetermined amplification factor, and output from the reproduction signal output terminal 2 to a reproduction circuit stage (not shown). Is played. That is, since the number of turns of the stator coil of the conventional rotary transformer shown in FIG. 4 is the same as that at the time of reproduction, the same reproduction effect can be obtained in this embodiment.

On the other hand, during recording, the switch 8
By this, the circuit of the reproducing system is turned off and the terminal b is switched to the open state, and the recording power supply voltage RECVcc is supplied through the diode and connected to the recording circuit system, and the recording signal to be recorded is the recording signal input terminal. It is supplied to the recording amplifier 5 via 3. The recording amplifier 5 supplies a voltage / current necessary for recording to the magnetic head 9, and the current at this time is supplied to the magnetic head 9 as an optimum recording current I so that the maximum reproduction output can be obtained.

After that, the recording signal given by the recording amplifier 5 at a predetermined level is passed through the terminal e of the stator connected to the recording amplifier 5 and the intermediate tap 1c, and the stator coil of the rotary transformer 1. The magnetic recording medium 1a is supplied to the magnetic head 9 through the rotary transformer 1, and the magnetic head 9 magnetically records a recording signal on a magnetic recording medium (not shown). Since the intermediate tap 1c is connected to, for example, the middle (1/2) of the number of turns of the stator coil 1a, the number of turns of the stator coil 1a of the rotary transformer 1 during recording is 2T, that is, FIG. As shown in Fig. 3, the stator side coil 1a is corresponding to the number of turns of the rotor side coil 1b.
The winding ratio of is 1.

Therefore, the output voltage amplitude of the recording amplifier 9 becomes I × 1 × 1 × Z = IZ, that is, FIG.
The output voltage amplitude of the recording amplifier 9 can be halved as compared with the conventional example shown in FIG.

As a result, the recording amplifier 5 at the time of recording
The power supply voltage of the recording amplifier 5 can be reduced as compared with the case where the conventional rotary transformer is used. For example, even when the frequency of the recording signal becomes high, the power supply voltage of the recording amplifier 5 can be reduced more than the conventional case. It's clear.

Therefore, according to the present embodiment, the intermediate tap 1c is provided on the stator side coil 1a of the rotary transformer 1 so that the winding ratio of the stator side coil 1a to the winding number of the rotor side coil 1b is 1. By providing and connecting the recording amplifier 5 to the intermediate tap 1c, the output voltage amplitude of the recording amplifier 5 at the time of recording can be made smaller than the conventional one easily with a simple configuration. Of course, the power supply voltage of the recording amplifier at that time can be reduced.

As a result, not only can cost reduction be achieved, but prevention of ignition failure, which is an important issue at present, can be realized with a simple structure.

Further, the higher the recording frequency is, the more the effect can be obtained. Therefore, it is a very effective means as a basic technology for consumer VTRs and digital VTRs expected in the future, and 5V of S-VHS, for example. A single power supply can also be realized.

In this embodiment, for example, a flat type rotary transformer may be used, or a cylindrical type rotary transformer may be used.
Of course, it can be easily realized, and the same effect can be obtained.

In the case of VHS HiFi, for example,
Since the recording frequency of the HiFi channel is low, cost reduction can be achieved when the present invention is applied only to the video channel.

Further, in this embodiment, the split ratio of the stator side coil 1a by the intermediate tap 1c (terminal e-
Even when the coil winding number between b / the coil winding number between the terminals a and e) is configured not to be 1, for example, it is obvious that the same effect as the above embodiment can be obtained.

[0047]

As described above, according to the present invention, only the output voltage amplitude of the recording amplifier can be easily reduced, so that the power supply voltage of the recording amplifier can be reduced.

As a result, the cost can be reduced, and the prevention of ignition failure, which is an important issue at present, can be realized with a simple structure.

[Brief description of drawings]

1 and 2 show an embodiment of a rotary transformer according to the present invention, and FIG. 1 is an equivalent circuit diagram of the rotary transformer.

FIG. 2 is a circuit diagram when the rotary transformer shown in FIG. 1 is used in a magnetic recording / reproducing apparatus.

3 and 4 show a conventional rotary transformer, and FIG. 3 is an equivalent circuit diagram of the rotary transformer.

FIG. 4 is a circuit diagram when the rotary transformer shown in FIG. 3 is used in a magnetic recording / reproducing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotary transformer 1a ... Stator side coil 1b ... Rotor side coil 1c ... Intermediate tap 2 ... Reproduction signal output terminal 3 ... Recording signal input terminal 4 ... Reproduction amplifier 5 ... Recording amplifier 6 ... Capacitor 7 ... Diode 8 ... Switch 9 ... Magnetic Heads a, b, e ... Stator side terminals c, d ... Rotor side terminals T ... Coil winding number I ... Optimal recording current RECVcc ... Recording power supply voltage

Claims (1)

[Claims] 1. A rotary transformer, comprising a stator and a rotor, which is electromagnetically coupled by windings respectively provided on the stator and the rotor to transmit signals to each other. A head, an intermediate tap provided on the stator winding, a reproducing circuit connected to one end of the stator winding, a recording circuit connected to the intermediate tap, and a other end of the stator winding. , The other end is connected to the reference potential point during the reproducing operation, the both ends of the stator winding are used as the stator winding, and the state is switched to the open state at the time of recording and the intermediate tap of the stator winding and the one end are used as the stator winding. A rotary transformer comprising: switching means for switching to use.