JPS6174105A - Helical scan type magnetic recorder - Google Patents

Abstract

PURPOSE:To reduce power consumption by controlling its supply current to an amplifier supplying a recording current to a rotary head so as to be interrupted except at a time when at least the rotary head comes into contact with a tape. CONSTITUTION:Switches SA, SB switching the supply power to amplifiers GA, GB for drive are provided at magnetic heads MA, MB and the switch is controlled for switching by using signals (servo signals) V, W obtained from a rotary phase detector of the rotary drum. That is, when any of the signals V, W is at H, the switch SA is closed, a power supply VCC is applied to the amplifier GA, and when the signal V is logical L, the switch SB is closed, a power is applied to the amplifier GB so as to attain control so that no power is applied to the amplifier of a magnetic head not coming into contact with the tape. Thus, the power consumption is reduced, the crosstalk at reproduction is reduced and noise due to suprious radiation is lowered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a helical scan type magnetic recording device that employs a rotating head, and particularly to a power-saving magnetic recording device that is suitable for operating on batteries or the like. It is related to the device.

[Conventional technology]

As shown in FIG. 3, a two-head helical scan type magnetic recording device has two rotary heads 2A and 2B disposed so as to scan the magnetic tape 1 in an oblique direction. It is configured to alternately record signals on the tracks.

In this case, conventionally, an output amplifier 4 is connected to the two rotary heads 2A and 2B via rotary transformers 3A and 3B, respectively.
Recording signals were constantly supplied from A and 4B.

[Problem that the invention seeks to solve]

As mentioned above, the conventional helical scan type magnetic recording device uses the output amplifier 4A at all times during recording.

Since 4B is configured in the operating state, the rotor rad 2A
, or 2B is not in contact with the magnetic tape 1, both output amplifiers 4A and 4B consume power.

This kind of power consumption is a small value of only a few percent compared to the overall power consumption in large magnetic recording devices, but in the case of small magnetic recording devices that are battery-powered. The power consumption by the output amplifiers 4A and 4B is also a value that cannot be ignored.

In addition, if the tape wrapping angle around the drum is larger than 180°, as seen in 8mm VTRs, if the head recording current of both channels is left flowing, there will be problems such as increased crosstalk during playback. In addition, there is a concern that noise may be generated due to unnecessary radiation.

In order to solve this problem, the present invention is designed to cut off the supply current to the amplifier that supplies recording current to the rotating head, except at least during the time when the rotating head is in contact with the tape. The present invention provides a magnetic recording device that reduces power consumption and is advantageous against crosstalk.

[Means for solving problems]

In this invention, in a helical scan type magnetic recording device having two or more rotating drums, each magnetic head is provided with a drive amplifier and a switch for opening and closing the power supply to the amplifier. Opening/closing is controlled by an opening/closing signal formed from a signal (servo signal) obtained from a rotational phase detection device.

Power is not supplied to the amplifier of the magnetic head that is not in contact with the tape.

Embodiment C] FIG. 1 is a simplified block diagram of the recording circuit of the magnetic recording device of the present invention, in which MA, MB are magnetic heads attached to a rotating head at approximately 180° intervals, RTA, RT,
is a rotary transformer.

Ga and Gs are output amplifiers for supplying recording current to the magnetic heads MA and M, and AD is an adder circuit.

FM-modulated luminance signals and chrominance signals are supplied to this adder circuit AD.aS A r 58 indicates a switch for supplying power to the output amplifiers Ga and Gs;
These switches SA, S8 are 1, for example, OR circuits OR, , O
It is configured to be closed by the output (H level) of R2.

In addition, IV is the inverter, ■ is the first control signal (CTL signal) obtained from the phase detector of the rotating drum as shown in the waveform diagram in Figure 2, and W is also shown in the waveform diagram in Figure 2. This is the second control signal.

[Effect]

Hereinafter, the opening and closing operations of the switches SA and Ss will be explained with reference to the waveform diagram in FIG.

Second control signal W and first control signal V
The OR circuit OR, which is supplied with
Since the output becomes H level, the switch SA is turned on during this period, and the output amplifier GA is supplied with the power supply Vcc and becomes in operation.

Therefore, the magnetic head MA is supplied with a recording current during this period as shown by signal A, and at this time, the magnetic head MA
If it is controlled so that it is in contact with the tape, the signal for one frame AI + A 2 * A 3...
・Can be recorded with plenty of time.

On the other hand, when the first control signal V is at the L level, the output of the OR circuit OR2 is at the H level, so the switch SB is closed, and power is supplied to the output amplifier Ga during this period.

Therefore, a recording current is supplied to the magnetic head Me side,
Signals B, , B2, B3, . . . for one frame are recorded on the tape.

When the second control signal W is at H level, both output amplifiers Ga and Gs are activated and recording current is supplied to both magnetic heads MA and MB. Signal dropout can be prevented.

If this overlap period is chosen to be several H-10 several H,
Signal dropout during playback can be completely prevented.

As described above, in the magnetic recording device of the present invention, the output amplifier GA*G that drives the magnetic heads Ma and Ms
Since power is supplied to B only during recording, the power consumed by the output amplifier G A + G 8 can be reduced by 30 to 40%.

Therefore, when the power source is battery-powered, the usage time can be extended, especially for small VTRs (8mm).
In this case, the effect is that the battery capacity can be reduced.

The case where two rotary heads are used has been described above, but for a four-head type in which a magnetic head is dedicated for recording and reproduction, and for multiple rotary heads each having an erasing head, each head is By providing an output amplifier and an on/off switch for its operating power source, it is possible to save power. Note that the two rotating heads have a tape wrapping angle of 18
In some cases, the winding angle is driven at 0°+α, and an audio PCM signal is recorded in the portion of this winding angle α.

In this case, the rise time of the second control signal W can be made faster by the time (Tα) corresponding to the wrapping angle α, as shown by the dotted line in FIG.

The operating time of the output amplifier G A + G 8 becomes correspondingly longer, and it can be applied to recording tracks of 180°+α.

Note that other logic circuits may be used as the control circuits for the switches SA and SB, and they may be designed to perform on/off rise and fall with a time constant to eliminate noise. good.

〔Effect of the invention〕

As explained above, the magnetic recording device of the present invention is configured such that output amplifiers are individually provided for a plurality of rotating magnetic heads, and operating power is supplied to the output amplifiers only during tape recording. This has the effect of reducing power consumption compared to a helical scan type magnetic recording device that records by keeping the recording current flowing.

In addition, especially in magnetic recording devices where the tape wrapping angle is 180″+α, crosstalk during playback is reduced.
This has the advantage that noise due to unnecessary radiation is also reduced.

[Brief explanation of drawings]

FIG. 1 is a simplified block diagram of the recording circuit of the magnetic recording device of the present invention, FIG. 2 is a waveform diagram of the main part of FIG. 1, and FIG. 3 is a schematic diagram showing a helical scan type magnetic recording device. It is. In the figure, 1 is a magnetic tape, and 2A and 2B are rotating shafts. De, MA and Ms are magnetic heads, RTA and RT are rotary transformers, and GA+08 is an output amplifier. SA+38 is a switch, ORI and OR2 are OR circuits, IV is an inverter, and ■ and W are first and second control signals, respectively. 11:4 Figure 2

Claims (1)

[Claims] In a helical scan magnetic recording device that includes a plurality of rotating magnetic heads and an amplifier that supplies recording current to each of the rotating magnetic heads, each of the amplifiers has a magnetic head driven by the amplifier that is connected to the tape. A helical scan type magnetic recording device characterized by having an additional switch circuit that supplies a power supply voltage during a contact period.