JPH0724087B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus which uses the same magnetic head for recording a signal on a magnetic recording medium and reproducing the recorded signal.

[Outline of Invention]

The present invention relates to a magnetic recording / reproducing apparatus equipped with a magnetic head for both recording and reproduction, in which an analog switch is connected in series to the magnetic head, and the control current of the analog switch is changed from that during reproduction during recording according to the operation mode of the apparatus. By increasing the number of signals, it is possible to prevent the saturation of signals during recording and the mixing of noise during reproduction, thereby preventing the deterioration of image quality.

[Conventional technology]

As a magnetic recording / reproducing apparatus having a magnetic head for both recording and reproduction, for example, as shown in FIG. 3, a standard tape speed mode (called "SP mode") and a long tape speed mode (called "LP mode") are available. In order to correspond
As magnetic heads, two types of magnetic heads having different track widths, that is, SP magnetic head 1 and LP magnetic head 2 are mounted on a rotary cylinder, and the rotary cylinder is rotated to form a magnetic head and a magnetic tape as a magnetic recording medium. There is a video tape recorder (so-called VTR) that records and reproduces video signals by contacting with.

In such a VTR, the SP magnetic head 1 having a wide track width corresponding to the SP mode is used in the SP mode, and the LP magnetic head 2 having a narrow track width corresponding thereto is used in the LP mode.

Therefore, connect the magnetic heads 1 and 2 in series with the transistors 3 and 4 as analog switches, and set the SP mode or L
Depending on the P mode, the base current is controlled to turn on either one of the transistors 3 or 4, and the other is turned off to select the SP magnetic head 1 or the LP magnetic head 2. I was doing.

[Problems to be Solved by the Invention]

In such a conventional VTR, SP mode or LP
The conductivity in the state where the analog switch such as the transistor 3 or 4 is turned on according to the mode is the same during recording and during reproduction.

However, since the current flowing through the magnetic head is different during recording and reproduction, if the conductivity of this analog switch is low, the signal current will be limited during recording and the image quality will be deteriorated. A large amount of control current is applied, which causes a problem that image quality is deteriorated due to generation of noise.

The present invention has been made in view of the above points, and an object thereof is to prevent deterioration of image quality in such a magnetic recording / reproducing apparatus in both recording and reproducing modes.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a magnetic recording / reproducing apparatus which also uses the same magnetic head for recording a signal on a magnetic recording medium and reproducing the recorded signal, in the magnetic head either directly or via a rotary transformer. An analog switch is connected in series, and an operation mode signal indicating whether the device is recording or reproducing is input, and a current generating means for generating a larger current during recording as a control current for the analog switch is provided. It is a thing.

A transistor is used as the analog switch, and the emitter and collector are connected in series to the magnetic head either directly or via a rotary transformer.
There is also provided a device provided with a current generating means for generating a larger current as a base current of the transistor during recording than during reproduction.

[Work]

With the above-described configuration, the control current of the analog switch (base current of the transistor) during recording is higher than that during reproduction in response to the operation mode signal indicating whether the device is recording or reproducing. The conductivity of the switch (between the emitter and collector of the transistor) in the ON state is higher during recording than during playback.

Therefore, a large signal current can be passed during recording, and a small control current can reduce noise during reproduction.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a magnetic recording / reproducing apparatus VT embodying the present invention.
FIG. 4 is a circuit diagram showing a main part of R, and parts corresponding to those in FIG. 3 are denoted by the same reference numerals.

Reference numeral 1 denotes an SP magnetic head for recording / reproducing, which is provided on a rotating cylinder (not shown), and exchanges a recording signal or a reproducing signal with a recording circuit / reproducing circuit (not shown) via a rotary transformer 5.

Reference numeral 3 is a transistor used as an analog switch, and a collector and an emitter are connected in series to the SP magnetic head 1 and its base is connected to the current generating circuit 7.

On the other hand, 2 is a magnetic head for LP for both recording and reproduction, and SP
It is provided on the same rotating cylinder as the magnetic head 1 for
The recording / reproducing circuit is switched and connected via the rotary transformer 6 to exchange a recording signal or a reproducing signal.

4 is a transistor used as an analog switch,
A collector and an emitter are connected in series to the LP magnetic head 2 and the base thereof is connected to the current generating circuit 8.

The current generation circuits 7 and 8 are current generation means, and both of these V
Input an operation mode signal that indicates whether TR is recording or reproducing in SP mode, or recording or reproducing in LP mode, and use transistor 3 or 4 as the control current for the analog switch.
This circuit selectively generates the base current of the. Therefore, high voltage E ₁ , E ₂ (E ₁
It comprises a voltage select circuit 7s or 8s for selecting <E ₂ ) and a resistor R ₁ or R ₂ for converting the selected voltage into a current.

Next, the operation of this embodiment will be described.

When the operation mode signal indicates SP mode recording or reproduction, the current generation circuit 8 does not output the base current to the transistor 4 because the voltage selection circuit 8s selects 0V. Therefore, since the transistor 4 is held in the OFF state, LP
Magnetic head 2 does not work.

On the other hand, in the current generating circuit 7, if the operation mode signal indicates the reproduction time of the SP mode, the voltage selecting circuit 7s selects a predetermined voltage E ₁ and converts it into a current by the resistor R ₁ to convert it into a current. Since it is supplied as a base current, the transistor 3 is turned on with a degree of conductivity corresponding to the base current, and a signal current reproduced from a magnetic tape (not shown) by the SP magnetic head is supplied to the rotary transformer 5 to reproduce it. Can be sent to.

At this time, the level of the voltage E ₁ for setting the base current is determined so that the base signal of the transistor 5 is not too much and noise is mixed in the reproduced signal.

If the operation mode signal indicates recording in SP mode,
The voltage select circuit 7s selects the voltage E ₂ higher than the voltage E ₁ , converts it into a current by the resistor R ₁ and supplies it as the base current of the transistor 3, so that the transistor 3 becomes conductive according to the base current. The recording signal sent from the recording circuit through the rotary transformer 5 becomes SP
The magnetic head 1 can be used for recording on a magnetic tape (not shown).

At this time, the level of the voltage E ₂ for setting the base current is determined so that the conductivity of the transistor 5 is not too low and the recording signal is saturated.

On the other hand, when the operation mode signal indicates LP mode recording or reproduction, the current generation circuit 7 is operated by the voltage selection circuit 7s.
Selects 0V and does not output the base current to the transistor 3. Therefore, since the transistor 3 is held in the OFF state, the SP magnetic head does not perform one operation.

On the other hand, if the operation mode signal indicates the reproduction in the LP mode, the current generating circuit 8 causes the voltage select circuit 8s to output the predetermined voltage E ₁
Is selected and converted into a current by the resistance R ₂ of the selected transistor, and the current is supplied as the base current of the transistor 4,
Is turned on with the conductivity according to the base current, and the signal current reproduced from the magnetic tape (not shown) by the LP magnetic head can be passed to the rotary transformer 6 and sent to the reproducing circuit.

At this time, the base current of the transistor 5 is limited so that noise will not be mixed in the reproduced signal.

If the operation mode signal indicates recording in SP mode,
The voltage select circuit 8s selects a voltage E ₂ higher than the voltage E ₁ and converts it into a current by the resistor R ₂ and supplies it as a base current of the transistor 4, so that the transistor 4 becomes conductive according to the base current. The recording signal sent from the recording circuit through the rotary transformer 5 to the LP state.
The magnetic head 2 can be used for recording on a magnetic tape (not shown).

At this time, the conductivity of the transistor 5 is maintained sufficiently high so that the recording signal is not saturated.

Here, the reason why noise is reduced by reducing the base current of the transistor 3 or 4 will be described.

In order to connect the collector and the emitter as a transistor using an analog switch, it is necessary to add a base current equal to or higher than the collector current / DC amplification and a base voltage equal to or higher than the lower voltage of the collector and the emitter. The base current needs to satisfy the above conditions.

However, the base current cannot flow indefinitely. Because there is no constant voltage or constant current in the actual circuit, noise components are always included, and the base current is no exception. Therefore, the noise component of the base current is transmitted to the collector and the emitter via the floating resistance and the floating capacitance.

Further, when the transistor is conductive, a collector-emitter saturation voltage, which is a voltage corresponding to the base current, remains, which also causes the base current to be transmitted to the collector and the emitter.

Therefore, if the base current is made to flow indefinitely, the noise that appears in the collector and the emitter will increase, so
The optimum magnitude of the base current exists depending on the magnitude of the signal current handled.

Next, another embodiment of the present invention is shown in FIG. This circuit shows only the circuit on the side of the SP magnetic head, and the circuit on the side of the magnetic head for LP is omitted.

In this embodiment, the SP magnetic head 1 is connected in parallel to the coil L ₁ on the rotary cylinder side of the rotary transformer 5 that electrically connects the rotary cylinder and its fixed portion, and the emitter of the transistor 3 as an analog switch is connected. -The collectors are connected in series to the coil L ₂ on the fixed side of the rotary transformer 5.

Even with this configuration, if the base current of the transistor 3 generated by the current generating circuit 7 is controlled by the operation mode signal, the same effect as that of the above-described embodiment can be obtained.

Since the control on the magnetic head side for LP is the same, the description is omitted.

Although a resistor is used as the voltage-current converting means in each of the above-described embodiments, a constant current circuit using a transistor or the like may be used instead of the resistor.

Further, each of the above embodiments is an example in which the present invention is applied to a VTR, but the present invention can be similarly applied to various magnetic recording / reproducing devices such as an audio tape recorder and a hard disk device.

〔The invention's effect〕

As described above, according to the present invention, in a magnetic recording / reproducing apparatus provided with a magnetic head for both recording and reproduction, the control current of the analog switch is increased at the time of recording so that a large amount of recording signal current is passed through the magnetic head. Therefore, it is possible to prevent the deterioration of image quality due to the limitation of the recording current.

Further, during reproduction, the control current of the analog switch is reduced to prevent noise components of the control current from being mixed into a small reproduction signal current, so that image quality can be improved and power consumption can be reduced. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main part of a magnetic recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a main part of a magnetic recording / reproducing apparatus according to another embodiment of the present invention. FIG. 3 is a circuit diagram showing a head switching unit of a conventional magnetic recording / reproducing apparatus having SP and LP magnetic heads. 1 …… SP magnetic head 2, 2LP magnetic head 3,4 …… Transistor (analog switch) 5,6 …… Rotary transformer 7,8 …… Current generator circuit 7s, 8s …… Voltage select circuit

Claims (2)

[Claims] 1. A magnetic recording / reproducing apparatus having the same magnetic head for recording a signal on a magnetic recording medium and reproducing the recorded signal, wherein an analog switch is directly connected to the magnetic head or in series via a rotary transformer. In addition to being connected, the apparatus is provided with a current generating means for inputting an operation mode signal indicating whether the apparatus is in recording or reproducing and generating a larger current in recording as a control current of the analog switch than in reproducing. Magnetic recording / reproducing device. 2. A magnetic recording / reproducing apparatus which also uses the same magnetic head for recording a signal on a magnetic recording medium and reproducing the recorded signal, wherein the magnetic head is used as an analog switch directly or in series through a rotary transformer. In addition to connecting between the emitter and collector of the transistor, there is provided a current generating means for inputting an operation mode signal indicating whether the device is at the time of recording or reproducing and generating a larger current as the base current of the transistor during recording than during reproducing. Magnetic recording / reproducing means characterized by the above.