JPS58171706A - Digital magnetic recording system - Google Patents

Abstract

PURPOSE:To simplify the circuit, by supplying AC and DC bias currents to the bias winding of magnetic heads and connecting switching elements in parallel to signal windings and connecting these switching elements to a current source and inputting a digital signal to switching elements. CONSTITUTION:An AC power source Sa and a DC power source Sd are connected to a bias winding lB of magnetic heads MK, and AC and DC bias currents are flowed to this bias winding. Switching elements SWK are connected in parallel to signal windings lK, and they are connected to a current source S. An MOS FET or a bipolar TR is used to input the digital signal to elements SWK. The deflected residual magnetism which is generated on a tape by the unidirectional current source S adjusts the DC bias current and disappeas. Thus, the circuit is simplified, and the multichannel system is realized easily with a pair of power sources.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital magnetic recording/reproducing apparatus, and more particularly to a digital magnetic recording system using a multi-magnetic system having a bias winding.

A fixed head type PCM sound reproduction device uses a multi-magnetic head that reproduces (reproduces) a digital signal encoded as an audio signal on multi-tracks of a magnetic tape.

Fig. 1 is a block diagram showing the recording operation by a conventional multi-magnetic head, where ■ is a magnetic tape, ch-1, ch-2,...
..., ch-n indicates a multi-track where PCM signals are recorded, 1M indicates a multi-magnetic head formed of a thin film, and each signal winding 11- of the multi-magnetic head M1-Mm 11 is the drive circuit ^8~^. The digital signal (PCM signal) to be recorded is supplied from the bias winding 1. which is common to each head. is supplied with a high frequency bias current.

Normally, in a magnetic head without a bias winding 11, the alternating current bias signal and the electric current rlL1 are superimposed by an electric circuit and supplied to the magnetic head, whereas the multi-magnetic head M shown in FIG. In M1, the bias magnetic flux due to the bias current and the signal magnetic flux due to the signal current are superimposed in the magnetic circuit and recorded on the magnetic tape TK. Therefore, when recording digital signals on a magnetic tape using the multi-magnetic heads M1 to M, t-, it is especially important to
It is necessary to take care that ** is a positive value, such as Kameoka, and the drive circuits ^1 to ^ are operated with two power supplies.

In addition, a circuit that can adjust the DC offset voltage was used. However, as the number of recording track channels increases, the number of drive circuits that supply the signal Ml increases, which complicates the circuit configuration, increases power consumption, and makes it difficult to adjust the recording current. There were drawbacks.

The present invention has been made in view of this point, and in a multi-magnetic head having a common bias winding,
A recording current corresponding to a digital signal is supplied by one current source, and its circuit configuration! The present invention provides a digital magnetic recording method that is simplified and can be easily integrated.

The recording system of the magnetic head of the present invention will be explained below.

Figure @2 shows a magnetic head equipped with the magnetic head drive circuit of the present invention in one bias winding 1lAIj1. sl is a high frequency bias power supply, and sD is a DC power supply.

This drive circuit includes a bias winding J, a bias voltage aS and a DC voltage 11So as shown in FIG. 3, and a high frequency AC bias voltage 1111. A bias current (1) in which a bias current (i) and an i-current bias current -1a are superimposed is supplied, and on the other hand, when the switching element sw is controlled to open and close by a digital signal to be recorded in the signal winding 11, a voltage of 5 as shown in FIG. A unidirectional recording current +1 value is supplied from the current S:S.

By the way, due to the unidirectional current source SK, the magnetic head My
t' a @ Then, for obvious reasons, the magnetic tape will have a residual magnetism that is biased due to its magnetization characteristics, that is, it will be magnetized only in one direction, and it will not be possible to obtain a pulse signal with positive and negative symmetry during playback. There are no carp.

However, since the bias tfi IS, in which the AC bias current 1a and the DC bias current -Ia that provide a high-frequency bias for the digital magnetic recording system of this invention are superimposed, is passed through the bias winding J, the recording current 1 mK causes a bias. When the magnetized unidirectional magnetism is VB, the DC bias current -T61 is applied to cancel this residual magnetism B,v.
By setting , the magnetic tape TK can be heated so that no residual magnetic component due to biased magnetization remains.

That is, when the switching element SWv is closed when the digital signal is O, no current flows through the signal winding 11, but
The DC component (Ia) of the bias current I magnetizes the magnetic tape T through the bias voltage 1 mY so that the residual magnetism becomes -B, and when the digital signal is 1, the switching element swv14! If the control is performed as follows, the current from the current aS flows as the signal winding IKK memory current Im, and the bias current I.

The magnetism -B, Y due to the direct current component (-It) is canceled out, and the magnetic tape T is magnetized so that the residual magnetism becomes 10B. Therefore, on the magnetic tape T, the residual magnetism of 10B1 and -Ba is present on the digital signal 1. It is recorded with OK correspondence and is not biased.

Bias winding 1. The current DC bias current -1d is the recording current 1. The current value may be set to generate a magnetic flux that is approximately half the magnetic flux φ generated in the gap portion of the magnetic head ME when the magnetic flux φ is applied. It is only necessary to set it so that it can be done.

The switching element sw is connected to the signal winding J of the magnetic head M8.
, as long as it has an on-resistance sufficiently small (less than a fraction) compared to the impedance of the n-channel MOB field-effect transistor (
FET) Q or a bipolar transistor T1 as shown in FIG. 6 may be used to supply a digital signal to its control terminal 1 (-f).

Figure 7 shows a multi-magnetic head drive circuit in which several magnetic head drive circuits shown in Figure 2 are connected in series.
Current source S, bias power source S&e, and DC power source So are commonly used for each of the magnetic heads M1 to M.

The switching elements sw, .about.sw1 are respectively controlled to open and close in accordance with the digital signals to be recorded, and parallel digital signals are recorded on the multi-tracks of the magnetic tape T by the multi-magnetic heads M1-M.

If the current supplied by the current source S is a constant value, each magnetic head M
The recording current 1. flowing through the signal windings 11-l of , ~M,. are equal, so if you want to adjust the recording current by 1 gY depending on the magnetization characteristics of the magnetic tape T, you only need to adjust the supply current of one electron aSS (and its drive circuit becomes extremely simple).

Note that the current of the current source S and the DC component of the bias current 11 (
-1a) should be made to generate magnetic fluxes in opposite directions to each other (the direction is 1m).

+Id may be set as the DC bias current.

Figure 8 shows a MOS type FET as the switching element SW.
The control circuit for supplying digital signals to the multi-magnetic head M, which is connected in series to the 5th channel used in QY, is a 4-channel control circuit, and 111 is the plate. A signal output circuit consisting of flip-flops (hereinafter referred to as DF/F) ILa to 11d, and 12 a shift register consisting of DF/Fs 12a to 12d.

Next, the operation of this circuit will be explained based on the 9th waveform diagram. Serial data 801! input from terminal T! Terminal T
(Shifted by clock signal CLKK from C) 9:A
ri 12 each D-F/F 12 a~124Kj1
Next shifted.

When the data for four channels is input to the shift register 12, the first word clock pulse pulse PW input to the terminal Tv causes the shift register 2 final data to be sent to each D-F/F 11a~ of the signal output circuit 11.
11dK, so depending on the output, FIT91~Q
4 is controlled to open and close.

That is, at the time when the first word clock (res PWl) is input, the signal 0.1°0.1 at the position of point IIW is transferred to the signal output circuit 11 as a parallel signal, and
F 11 a~11 (each Q output of l &!1,0°1.
It becomes 0. Therefore, each rETQ, ~Q4it on,
The magnetic head M is controlled to turn off, on, and off.

The recording current ■ flows only in M4 and M4, and the other magnetic heads M,
BiM, is short-circuited by FFTQr-Qs and the recording current 1. does not flow.

Below, word clock Noriress pw, , pw
, .

. . . Each time the serial gator SD is serially parallel-converted by the shift register 12, the serial gator SD is connected to each magnetic head M, ~M4.
will be supplied to

When FET Q, (Qs - Qs - Q4) is on, no recording current flows, but as mentioned above, the residual magnetism of the magnetic tape is - due to the DC component (-Ia) of the bias current ■. B, and it goes without saying that the positive and negative are balanced.

FIG. 10 shows another embodiment for supplying digital signals, in which the control circuit of FIG.
and word clocks (response PW input terminals are swapped).

In this case, since the world clock pulse PW is input to the shift register 12, the shift register 12 receives the ripple clock signal -5cL.
Every time the world clock pulse PW is shifted by K, the D-F/F 11 of the signal output circuit 11 of that channel is shifted.
a to 11 d are driven, and the serial data 8D input to the D terminal at that time becomes the i output and F E
T Controls the cough channel of Q, ~Q.

Therefore, the magnetic heads M, ~M, receive the clock signal CL
Time division gIIK driven sequentially with a delay of K periods
Become.

This circuit 11 has the effect of eliminating the spike voltage tILvII that occurs in the circuit of FIG. 8 in which all the magnetic heads M1 to M4 are driven at the rising edge of the word clock pulse PW.

As explained above, in the digital magnetic recording system of the present invention, the drive circuit for the magnetic head, which was conventionally required for each recording track, is configured with a single-throw switching element. , and the power supply circuit can be greatly simplified, and even in the case of a drive circuit for one multi-magnetic head, the drive circuit can be constructed by simply connecting the drive circuits in series, so that the power supply circuit can be supplied in a single direction. There is an advantage that only one current 1lt- needs to be provided.

Furthermore, even when the number of recording tracks increases, circuit integration is easy and power consumption is low.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional multi-magnetic head, Fig. 2 is a basic magnetic head drive circuit diagram of the present invention, Fig. 3 is a bias current waveform diagram, Fig. 4 is a recording current waveform diagram, Fifth
Figure 6 is a drive circuit diagram consisting of a switching element vM08 type FET and bipolar transistor, Figure 7 is a drive circuit diagram with a multi-magnetic head, and Figure 8 is a control (b) for supplying digital signals. FIG. 9 is a waveform diagram explaining the operation of FIG. 8, and FIG. 10 is a circuit diagram showing another embodiment of the control circuit. In the figure, M, ~M are multi-magnetic heads, 11~l! l is signal 41! I j- is a bias winding, SW is a switching element, S is a current source, % sa is a bias power supply, and S is a DC power supply. Figure 1 Figure 2 Figure 3 Figure 1゜ Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] An alternating current bias current and a direct current bias current are supplied to the bias winding of the magnetic herad, and the signal IIklI of the magnetic head is supplied.
iC is connected to a switching element Y in parallel and connected to a current source, and the switching element is controlled by a digital signal to be described.
e-spring method.