JPH02116001A - Rotary head type magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To prevent the destruction of a semiconductor element and the distortion of the recording signal by inhibiting the application of the recording signal of a large amplitude to the input and output sides of a head amplifier. CONSTITUTION:In a recording state the 1st and 2nd switches 4 and 5 have short circuits and the input and output sides of a head amplifier 2 are grounded. Therefore the recording signal of a large amplitude is never applied to the input and output sides of the amplifier 2. As a result, a semiconductor element of the first stage of the amplifier 2 is not destroyed nor the recording signal has no distortion. In a reproducing state the minute voltage produced by the ON resistance of a 3rd switch 6 is fed back to the input side of the amplifier 2 via a magnetic head 1 in case the output current of the amplifier 2 flows to the switch 6. However this feedback is negative and therefore the amplifier 2 never oscillates.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applied to high-definition VTRs, etc., and includes a rotating drum having a magnetic head, a playback head amplifier, a rotary transformer, and a recording/playback switching circuit. The present invention relates to a rotary head type magnetic recording/reproducing device 6.

[Prior art] Fig. 7 shows the recording/reproducing switching of a conventional rotary head type magnetic recording/reproducing device, as shown in, for example, Proceedings of the 1985 National Conference of the Television Society 7-5 “Circuit Mounting System in Rotating Cylinder of rVTR”. FIG. 2 is a block diagram showing the configuration of a circuit. In the figure, (1) is a magnetic head for recording and generating signals, and (2) is a reproducing head amplifier, which amplifies the reproducing output of the magnetic head. (3) is a rotary transformer which transmits the output signal of the head amplifier (2) to the fixed side, and transmits the recording signal from the fixed side to the rotating side during recording. (18) is a recording/reproduction switching circuit which short-circuits or opens between the input and output of the head amplifier (2). (17) is an input terminal for a recording/reproducing switching signal, which controls the recording/reproducing switching circuit (8).

Note that one of the winding terminals (^) of the magnetic head (1) is connected to the input side of the head amplifier (2), and the other (B) is grounded. Further, one (C) of the rotation side winding terminals of the rotary transformer (3) is connected to the output side of the head amplifier (2), and the other (D) is grounded.

Next, the operation of the above configuration will be explained.

During recording, a recording mode signal is applied to the recording/reproducing switching signal input terminal (17) by a slip ring (not shown) or the like, and the recording/reproducing switching circuit (18) is brought into a short-circuited state. In this state, the recording signal transmitted from the fixed side to the rotating side via the rotary transformer (3) passes through the recording/reproduction switching circuit (18), is applied to the magnetic head (1), and a recording current flows.

Also, during % playback, power is supplied to the head amplifier (2) by a slip ring or the like, and at the same time, a playback mode signal is given to the recording/playback switching signal input terminal (17), and the recording/playback switching circuit (18) is opened. state, and the input side and output side of the head amplifier (2) are separated. In this state, the main output from the magnetic head (1) is input to the head amplifier (2), where it is amplified and then transmitted from the rotating side to the stationary side via the rotary transformer (3), where signal processing is performed. Video and audio are played back in circuits, etc.

[Problems to be Solved by the Invention] The recording/reproducing switching circuit of the conventional rotary head type magnetic recording/reproducing device is configured as described above, so that the recording signal is applied to the magnetic head at the time of recording, and at the same time the input signal to the head amplifier is input to the head amplifier. The other side also joins in, and the minute signals are human-powered. As a result, the semiconductor element in the first stage of the head amplifier may be destroyed by the large amplitude recording signal.

In addition, the recording signal transmitted to the rotation side via the rotary transformer is applied to the recording/reproduction switching circuit, and at the same time is also applied to the output side of the head amplifier, and the recording signal is sent to a low impedance circuit such as an emitter follower on the output side of the head amplifier. There were problems such as a portion of the liquid flowing in and causing distortion in the recorded signal.

This invention was made in order to solve the above-mentioned problems, and prevents the recording signal from being applied to the input side and output side of the head amplifier in a state of large amplitude, thereby preventing damage to the semiconductor element and preventing the recording signal from being applied to the input side and output side of the head amplifier. An object of the present invention is to provide a rotary head type magnetic recording/reproducing device that can eliminate the occurrence of distortion.

[Means for Solving the Problems] In the rotary head type magnetic recording/reproducing device according to the present invention, the reproducing head amplifier is constituted by an inverting amplifier circuit, and the recording/reproducing switching circuit is connected to the input side of the head amplifier and The first
and a third switch interposed between the second switch, the winding terminal of the magnetic head, the rotating side winding terminal of the rotary transformer, and ground.

[Function] According to the present invention, during recording, the first and second switches are short-circuited and the input terminal and output side of the head amplifier are grounded, so that the input terminal of the head amplifier is not connected when the recording signal has a large amplitude. This prevents damage to the semiconductor element at the first stage of the head amplifier and distortion of the recording signal. Furthermore, when the output current of the head amplifier flows through the third switch during playback, even if a minute voltage generated by the on-resistance of the third switch is fed back to the input terminal of the head amplifier via the magnetic head, Since this results in negative feedback, the head amplifier will not oscillate.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a recording/reproducing switching circuit of a rotary head type magnetic recording/reproducing device according to an embodiment of the present invention. In the figure, (1) is a magnetic head, and (2) is a reproducing head amplifier. It consists of a 1-inverting amplifier circuit. (
3) is a rotary transformer.

In the above configuration, one of the winding terminals (A) of the magnetic head (+) is connected to the input side of the head amplifier (2), and the output side of the head amplifier (2) is connected to the rotary transformer (3). One of the rotating side winding terminals (C)
The other (B) of the winding terminals of the magnetic head +11 and the other (D) of the rotating side winding terminals of the rotary transformer (3) are connected.

In FIG. 1, (4) is a first switch interposed between the input terminal of the head amplifier (2) and the ground;
5) is a second switch interposed between the output side of the head amplifier (2) and the ground, and (6) is the other (B) of the winding terminals of the magnetic head (+) and the rotary rotor. The other of the rotating side winding terminals of the transformer (3) (a third switch interposed between the DJ and the ground; these first to
The third switches (4), (5), and (6) constitute a recording/reproduction switching circuit.

FIG. 2 is an example of a circuit similar to that shown in FIG. 1 above. In the figure, (7) is a switching transistor, which constitutes the first switch (4). (9) is also a switching transistor and constitutes the second switch (5). (8) and (10) are base resistances of the switching transistors (7) and (9).

(11) is a field effect transistor (hereinafter referred to as FET), which constitutes the third switch (6).

(12) is a DC cutoff capacitor, (I3) is a lease resistor, (+41 is a bypass capacitor connected in parallel to the lease resistor (13), (15) is FET (
II) is the resistor that provides reverse bias, (16) is F E
T is the gate resistance of (11).

(II) is a recording/reproduction switching signal input terminal, and the base resistance (
8) and (10) are connected to resistors (15) that provide reverse bias to FET (11), respectively. Further, the gate resistor (16) of the FET (1-th) is connected to the power supply (Vcc) of the head amplifier (2).

Next, the operation of the above configuration will be explained.

During recording, the recording/playback switching signal input to the input terminal (17) is at a high level, and the head amplifier (2)
As a result, the switching transistors (7) and (9) are in a short-circuited state, and F[E T (II) is in an open state.

In other words, as shown in FIG. 3, the first and second switches +4) (Fl) are turned on, and the third switch (6)
) is turned off.

In this state, the recording signal (IREC) transmitted from the stationary side to the rotating side via the rotary transformer (3) is transmitted to the rotating side winding terminal of the rotary transformer (3), as shown by the arrow in Figure 3. A current flows through a current loop consisting of one side (Dl → magnetic head (1) → first switch (4) → ground → second switch (5) - the other side (C) of the rotating side winding terminal of the rotary transformer (3). When a predetermined signal is recorded, the input side and output side of the head amplifier (2) are grounded, so that a recording signal with a large amplitude is not applied.

Next, during reproduction, the recording/reproduction switching signal input to the input terminal (17) is at a low level.

Power (Vcc) is supplied to the head amplifier (2). As a result, switching transistors, resistors (7) and (
9) becomes open, and F ET (II) becomes short-circuited. That is, as shown in FIG. 4, the first and second switches +4) (5) are turned off, the third switch (5) is turned on, and one of the winding terminals (B) and One (D) of the rotating side winding terminals of the rotary transformer (3) is grounded.

In this state, the playback output from the magnetic head (1) is input to the head amplifier (2), where it is amplified and then transmitted from the rotating side to the stationary side via the rotary transformer (3), where it is transmitted to the signal processing circuit, etc. Video and audio are played back.

Here, since the head amplifier (2) is composed of an inverting amplifier circuit, the output current of this head amplifier (2) (
1) flows through FET (11), which is the switch (6), a minute voltage generated by the on-resistance of r''ET (II) flows through the magnetic head (+) to the head amplifier (2). Even if it is fed back to the input side, it becomes negative feedback, so the head amplifier (2) will not oscillate.

Note that, as shown in FIG. 2, using FET (11) as the third switch (5) has the following advantages.

For example, it is possible to use an NPN type transistor as the third switch (5) as shown in FIG. 5, but in this case, during the negative half cycle of the recording signal shown in FIG. , the collector potential becomes lower than the base potential, which is approximately O[V]. Due to warping, the base
If the collectors are electrically connected, the recording signal will be lost in Figure 6 (b).
), the waveform becomes distorted in part of the negative half cycle, making it impossible to record normally. On the other hand, FE
When using T, the current flowing from the drain to the gate is very small, so there is no distortion in the recorded signal, and the recording signal is normal.
Good recording can be made.

In addition, in the above embodiment, semiconductors, that is, transistors are used as the first to third switches, but switches having small mechanical contacts such as reed relays may also be used.
The same effects as in the embodiment described in U are obtained.

Furthermore, if a switch whose stray capacitance when open is smaller than the stray capacitance h↑ of other switches when open is used as the first switch (4), for example, a transistor with a small collector capacitance, the head amplifier (2) Since it is possible to reduce the aged component added to the input, it is effective in expanding the transmission band of the reproduced signal.

[Effects of the Invention] As described above, according to the present invention, during recording, the recording signal is not applied to the input side and output side of the head amplifier in a large amplitude state, so that the semiconductor of the first stage of the head amplifier is It is possible to prevent the element from being destroyed and also to prevent distortion from occurring in the recording signal. Further, even if a part of the output signal of the head amplifier is fed back to the input side of the head amplifier, the head amplifier will not oscillate and stable operation can be expected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a recording/reproducing switching circuit of a rotary head type magnetic recording/reproducing device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a specific example of the circuit configuration of FIG. 1, and FIG. 3 and 4 are block diagrams illustrating operations during recording and reproduction. FIG. 5 is a block diagram explaining a comparative example with respect to FIG. 2, FIGS. 6(a) and (b) are waveform diagrams of recording signals with the configuration shown in FIG. 5, and FIG. 7 is a diagram of a conventional rotary head. FIG. 2 is a block diagram showing the configuration of a recording/reproducing switching circuit of a type magnetic recording/reproducing device. (1) - "Magnetic head, (2) -" Playback head amplifier, (3) - Rotary transformer, (4) - First switch, (5) - Second switch, (6) Axis/No. 3
switch. Note that the same reference numerals in Figure 1 indicate the same or corresponding parts. Fig. 1 Horizontal cut '7F Navel and '7 arrow rotary transformer 1 switch 2 switch 3 switch 3

Claims (1)

[Claims] (1) A rotating drum having a magnetic head, a playback head amplifier, a rotary transformer, and a recording/playback switching circuit, means for supplying power to the head amplifier, and means for inputting a recording/playback switching signal to control the recording/playback switching circuit. A rotary head type magnetic recording device, wherein one of the winding terminals of the magnetic head is connected to the input side of the head amplifier, and the output side of the head amplifier is connected to one of the rotating side winding terminals of the rotary transformer. In the playback device, the head amplifier is configured with an inverting amplifier circuit, the other winding terminal of the magnetic head is connected to the other rotating side winding terminal of the rotary transformer, and the recording/playback switching is performed. A circuit includes a first switch interposed between the input side of the head amplifier and ground, a second switch interposed between the output side of the head amplifier and ground, and the other of the winding terminals of the magnetic head. and a third switch interposed between the other of the rotation-side winding terminals of the rotary transformer and ground.