JP2790049B2 - Recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly to a recording apparatus for AGC-amplifying a recording signal to a recording head.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing an example of a conventional recording apparatus. This recording device is an example of a magnetic recording / reproducing device, and this recording device has an input terminal 20 for receiving a low-frequency conversion color signal.
And an amplifier circuit (C-AMP) connected to the input terminal 20
21, an input terminal 22 for receiving a supply of a luminance signal, and an AGC amplifier circuit (Y-AGC) 2 connected to the input terminal 22.
3, an addition circuit 24 connected to each of the outputs of the amplification circuit 21 and the AGC amplification circuit 23, a current amplification circuit (REC AMP) 25 connected to the output of the addition circuit 24,
Switching circuit 26 connected to the output of current amplification circuit 25
And a mute control terminal 27 to which a control voltage for controlling the switching circuit 26 is input, and an output terminal 28 for taking out the output of the switching circuit 26, constitute an amplifier circuit for a low-frequency conversion color signal and a luminance signal.

Then, via a resistor 29 and a magnetic head 30, a terminal 31, a detection resistor 32, a detection circuit (DET)
A voltage conversion circuit is composed of 33 and a detection circuit capacitor 34.

Further, the voltage extracted by the detection circuit 33 is compared with an internal reference voltage E by a comparison circuit 35, and a voltage corresponding to the comparison result is supplied to a capacitor 37 via a terminal 36. Then, the voltage at the terminal 36 is
3 is controlled by a loop including an AGC amplification circuit 23, an addition circuit 24, a current amplification circuit 25, a switching circuit 26, a magnetic head 30, a detection circuit 33, and a comparison circuit 35.
A C control loop is formed.

Next, the operation of the recording apparatus when the recording current is muted will be described. A mute control signal is input to the mute control terminal 27 so that the mute is turned on when a high level signal (H) is input and turned off when a low level signal (L) is input.

When a mute control signal (H) is input to the mute control terminal 27 (mute ON), the switching circuit 26 switches to the open terminal 26c side, and the output recording current does not flow to the terminal 28. Therefore, the output of the comparison circuit 35 functions to maximize the gain of the AGC amplifier circuit 23.

Next, when the mute control signal (L) is input to the mute control terminal 27 (mute off), the switching circuit 26 switches to the terminal 26b side,
A signal current flows to the magnetic head 30 via the terminal 28.

A video tape recorder provided with a mute circuit is disclosed in Japanese Patent Application Laid-Open No. 63-94407. According to this technique, when a normally recorded video signal is reproduced, an excessive output signal of the AGC reproduction amplifier during mute off is prevented from being generated.

[0009]

FIG. 4 is a timing chart of a mute control voltage and an output recording current of a conventional recording apparatus. According to the conventional recording apparatus, when the mute control signal (L) is input to the mute control terminal 27 (mute off), the AGC amplifier circuit 23 stands by at the maximum gain, so that the AGC control loop is momentarily stabilized until it is stabilized. An excessive output current as shown by Ia flows through the magnetic head 30. Therefore, there is a problem in that the output excessive current is written on a recording medium (magnetic tape), so that the image is disturbed during reproduction.

The invention disclosed in Japanese Patent Application Laid-Open No. Sho 63-94407 relates to a technique for preventing an excessive output signal generated when a normally recorded video signal is reproduced, as described above. It does not mention a technique for preventing an excessive signal generated during recording.

An object of the present invention is to prevent an excessive recording signal from being generated when the mute is turned off.

[0012]

According to the present invention, there is provided a recording apparatus for amplifying a recording signal to a recording head by AGC, comprising: amplifying means for amplifying a recording signal to a recording medium; Control means comprising a control loop for variably controlling the gain of the amplification means in accordance with the amplification output level; mute means for cutting off the amplification output; and
A capacitor to be held, and a
A voltage corresponding to the amplified output at that time is applied to the capacitor.
Switch for supplying the capacitor to the capacitor and disconnecting the control loop.
By holding the voltage corresponding to the amplified output immediately before the mute means is turned on by the capacitor, and using the held output as a control signal of the amplifying means when the mute means is turned off, And holding means for supplying the amplified output to the amplifier before the mute is turned on when the mute is turned off.

[0013]

When the mute circuit is turned off, the voltage corresponding to the gain immediately before the mute circuit is turned on is held by a capacitor to turn off the AGC loop. Therefore, the gain of the amplifier circuit becomes equal before the mute is turned on. Therefore, it is possible to prevent the occurrence of an excessive output current when the mute is turned off.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram of an example of a recording apparatus according to the present invention, and FIG. 2 is a timing chart of a mute control voltage and an output recording current of the recording apparatus. Note that the same components as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, a recording device using a magnetic tape as a recording medium will be described. However, the present invention is not limited to a magnetic tape, and the present invention can be applied to, for example, a magnetic disk or a magneto-optical disk. is there.

The recording apparatus has the same amplifying circuit 21 as in the prior art.
An AGC amplification circuit 23, an addition circuit 24, a current amplification circuit 25, a switching circuit 26, a magnetic head 30,
The AGC control loop formed by the detection circuit (DET) 33 and the comparison circuit 35 is obtained by adding the loop on / off switch 1 and the holding capacitor 37.

That is, the output side of the comparison circuit 35 and the AGC
The loop open / close switch 1 is provided between the control input sides of the amplifier circuit 23. The switch 1 is configured by a two-contact switching relay circuit as an example, but may be configured by an open / close relay circuit having one contact. Incidentally, the switching circuit 26 can also be constituted by the same one as this relay circuit. Further, a switching circuit using a transistor instead of a relay circuit may be used.

The common contact 1a of the switch 1 is
One contact 1b is connected to the terminal 36, the capacitor 37, and the control input side of the AGC amplifier 23, and the other contact 1c is open. The other end of the capacitor 37 is grounded. Further, the switch 1 is configured to be controlled by a mute control signal via a mute control terminal 27. That is, both the switching circuit 26 and the switch 1 are simultaneously controlled by the mute control signal.

Next, the operation of this device will be described.
First, the mute control signal is (L), that is, the mute
When the switch is off, the contact of the switching circuit 26 is in contact with the side 26b, and the contact of the switch 1 is in contact with the contact 1b. Therefore, the AGC control loop is closed and the gain of the AGC amplifier circuit 23 is controlled according to the recording current flowing through the magnetic head 30.

On the other hand, when the mute control signal is (H), that is, when the mute is turned on, the contact of the switching circuit 26 is switched to the side 26c, and the contact of the switch 1 is switched to the side 1c. Therefore, the AGC control loop is disconnected at the two positions of the switching circuit 26 and the switch 1, and the recording current does not flow through the magnetic head 30. At this time, the voltage immediately before the contact of the switch 1 is switched to the contact 1c is held in the capacitor 37.

Next, when the mute control signal is again switched to (L), that is, to mute / off, the switching circuit 26
The contact of switch 1 is switched to the side 26b, and the contact of switch 1 is switched to the side 1b.
, A recording current flows. However, since the capacitor 37 holds the voltage immediately before the contact of the switch 1 is switched to the contact 1c, the gain of the AGC amplifier circuit 23 is muted and turned on immediately after the contact of the switch 1 is switched to the side 1b. Equals the previous gain. Therefore, since the excessive output current does not flow to the magnetic head 30 immediately after the mute / off operation, it is possible to prevent the excessive output current from being recorded on the magnetic tape and disturbing the image during reproduction.

[0022]

According to the present invention, the AGC control loop is provided with a capacitor for holding the AGC control voltage immediately before the mute is turned on and an AGC loop on / off switch, and these capacitors and the switch immediately before the mute is turned on. Since it is configured to hold the AGC voltage,
Immediately after the power is turned off, an excessive output current is generated, and this current can be prevented from being recorded on the recording medium and disturbing the image during reproduction.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an example of a recording apparatus according to the present invention.

FIG. 2 is a timing chart of a mute control voltage and an output recording current of the recording apparatus.

FIG. 3 is a circuit diagram of an example of a conventional recording apparatus.

FIG. 4 is a timing chart of a mute control voltage and an output recording current of a conventional recording apparatus.

[Explanation of symbols]

 1 switch 23 AGC amplifier circuit 26 mute switching circuit 37 capacitor

Claims (4)

(57) [Claims] 1. A recording apparatus for AGC-amplifying a recording signal to a recording head, comprising: amplifying means for amplifying a recording signal to a recording medium; and variably controlling the gain of the amplifying means in accordance with the amplified output level. Control means comprising a control loop; mute means for cutting off the amplified output; a capacitor for holding the amplified output;
When the stage is turned off, the capacitor is
Supply voltage to the capacitor and the control loop
And a switch for cutting the said muting means the voltage corresponding to the amplified output immediately before is on a capacitor
With control signal of the amplifying means the holding output at the time of off of the muting means to hold by, comprise a holding means for providing a mute-on front amplified output of said amplifying means at the OFF time of the muting means A recording device characterized by the above-mentioned. 2. The recording apparatus according to claim 1, wherein said control loop is connected by said switch when said mute means is turned off. 3. The recording apparatus according to claim 1, wherein the recording signal to be recorded on the recording medium is a signal obtained by adding a chrominance signal frequency-converted to a low frequency and a luminance signal frequency-modulated. . 4. The apparatus according to claim 1, wherein said control means includes a comparing means for comparing said amplified output with a predetermined reference voltage, and variably controls a gain of said amplifying means in accordance with a result of the comparison. The recording device according to any one of the above.