JPS623404A - current output device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a device for driving a magnetic recording head, and more particularly to a current output device that supplies a recording current to the magnetic head via a rotary transformer. .

[Conventional technology]

A current output device is a device that has an output characteristic that fixes the current supplied to the load at a predetermined value even if the impedance of the load changes.It is suitable for driving magnetic heads, etc. whose electrical characteristics are determined by the current. Such a device is optimal.

About the current output device that drives the conventional magnetic head i@
This will be explained using Figure 4. (1) is the input terminal of the recording signal J&EL, (2) is an operational amplifier with amplification degree A, (3) is a resistor with resistance value R, (4) is a drive transistor with a pnp structure, (
5) is a magnetic head as a load, and (6) is a power source of voltage Vc.

Next, the operation will be explained. The recording signal ei applied to the input terminal (1) is applied to the non-inverting input terminal of the operational amplifier (2), amplified by the amplification factor A, and supplied from the output terminal to the base of the drive transistor (4). On the other hand, a resistor R (3) is connected between the power supply (6) and the emitter of the drive transistor (4).
) is connected, and the connection point is connected to the inverting input terminal of the operational amplifier (2) to perform a negative feedback operation.

At this time, the current 1 flowing through the resistor R(3) is 1=(Vc
-Ve)/R---[1) and (ei -Ve)
It is determined by the following two conditions: A + VBI = Ve --(2). From formula [2], ve=A(A+1)-1ei+(1+
A) -'VBz ---(3) Generally, A is several tens of dB or more, VBE ~ 0.6v, and Vee1
becomes. Substituting this into formula [1], 1=(vc-6
1 in/R---(4). In other words, the DC bias current (Va/R) and the recording current (e1/R) related to the recording signal are independent of the load magnetic head (5) connected to the collector of the drive transistor (4).
5). By the way, the magnetic head (5) is equivalent to an inductance, and responds only to the recording current without responding to the DC bias current, and its value is determined only by the recording signal ei and the resistance value R of the resistor (3). If el is a constant amplitude signal, its current value is also fixed at a constant amplitude. Therefore, it can be put to practical use as a current output device.

However, for example, in video tape recorder (VTR) devices that are currently in practical use, the drive transistor (4
) and the magnetic head (5) are not directly connected,
As shown in FIG. 5, current is transferred through a rotary transformer (7). In this case, the current transfer characteristics of the rotary transformer (7) become a problem. In FIG. 6, as shown in the current transfer characteristic in (a) and the equivalent circuit in (b), the transfer characteristic is a first-order high-pass filter characteristic. Therefore, rotary fist transformer (7)
Even if a fixed current is supplied to the primary side of the device, the current value will attenuate on the secondary side due to the transmission characteristics in the low frequency range being distorted.

Expressing this in a formula, the current 12 on the secondary side of the rotary transformer is 12=α・(scR)・(1+5OR)−1i
l---[5], and in the low frequency range of 1>SCH, 1
2(α・(SCR)j, 1 and 5=j2πf, so 12 is attenuated as it gets closer to DC. However, 1l=ei
/R. In the high frequency range of 5CR)>1, 12~
The current value is a constant υ of α・11. Note that α is a variable related to the turns ratio between the primary and secondary sides of the rotary transformer (7), and in VTR devices, α = 2 is often used for the purpose of improving the S/N ratio. There is.

[Problem that the invention seeks to solve]

Since the conventional current output device is configured as described above, a rotary wire is connected between the drive transistor and the magnetic head.
When a transformer is used, the current value of the magnetic head does not have a constant value independent of the recording signal frequency, and the current value in the low frequency region is attenuated. At present, solving this drawback with a rotary transformer alone cannot be expected to achieve any significant improvement due to constraints in the design of the device and high costs due to the use of expensive magnetic materials. be.

This invention was made to solve the above-mentioned problems, and provides a current output device that can significantly improve the low-frequency transfer characteristics by electrically correcting the deterioration of the low-frequency transfer characteristics of the rotary transformer. The purpose is to obtain.

[Means for Solving Problems J] A current output device according to the present invention is such that a circuit having a transfer characteristic opposite to that of an equivalent circuit of a rotary-9 transformer is provided in a primary current circuit.

[Effect]

In this invention, [5] formula % formula % in the explanation of the above-mentioned conventional example
) for the input recording signal e1 to the primary current 11 of il =
(1/R) (1+l/5CIRt) el, CR=C
If it is set to IR1, 12=αe 1 /R, and it no longer has frequency characteristics.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (8) is an integrator, (9) is an adder,
Other configurations are the same as before. The configuration of a typical integrator is shown in FIG. In the figure, qO and (b) are the resistor R1 and capacitor C1 that form the product 9 and 1, respectively, (2) is the operational amplifier necessary to perform the complete integration operation, and α is the wide band with a gain of -1. In the operational amplifier, a and a are integral output terminals. The recording signal e1 of the input inner (1) is connected to the resistor R.
1α0, the capacitor αη, and the operational amplifier (2) convert it into −(5CIR1) −′ e t, which is further inverted (−1 times) by the wideband operational amplifier (to) and becomes (SCIR
l)-'e1. This is the integrator (8) shown in Figure 2.
If the output signal yJI is added one-to-one with the original signal 01 in the adder (9) in Figure 1, then (x+(sc, R1
)-')et.

If this addition signal is input to the non-inverting input terminal of the operational amplifier (2), all operations can be performed as before [,7, the total current 1 of the drive transistor (4) is i=[Vc-(1+(SCIR)
+))e+]/R, where the current il corresponding to the recording signal ei is il = (1+(5CIRI)-'
)el /R is the primary current of the rotary transformer (7), and the corresponding secondary current ±2 is:
12=α(SCR)(1+5CR)""Substituting 11 for il, it becomes. Here, the integrator α is set so that CR=CIR1.
If all of the integral constants of the sword are selected, each term in the numerator and denominator can be eliminated, resulting in 12=(αe i)/R. This shows that the deterioration of the low-frequency transmission characteristics of the rotary transformer can be completely corrected.

FIG. 3 shows another embodiment that does not use the adder (9) of FIG. 1 and the broadband operational amplifier α3 of FIG. 2. In FIG. The configuration in Figure 3 has an input resistance α0 (resistance value r) and a feedback resistance (1G (resistance value Rr) t) connected to the inverting terminal of the operational amplifier (2).
The feature is that the output signal of the integrator (8) is inverted and summed by the integrator (8) output signal - (5CIR, door 1eit).The emitter voltage of the drive transistor (4) at this time is Ve=
el(1+Rf/r)-(-(SCIR4)-'et
)(Rr/r). Therefore, the primary current II of the rotary transformer corresponding to the recorded signal 9e1 is il = (1+Rr/r+Rr/(SCIRlr)
)et/R, and the secondary current 12 is 12=α(SCR
)(1+5CR)"-' Substitute 11 into the equation of i1 and process it. This is l, )> r / Rr and CR = C
When li’ll, i2”q(αRye1) / (rR
), and the influence of the rotary transformer (7) is removed.
be done.

As described above, the recorded signal e1 and the integral signal of the signal are combined at an addition ratio according to the selected circuit format, and the integration time constant is made to match the low-frequency equivalent circuit time constant of the rotary transformer. Accordingly, the gist of the present invention can be realized.

By the way, in the explanation, one character indicating the polarity of the signal is omitted.

In the above embodiment, the current drive circuit using a single transistor was explained as an example, but in the present invention, the signal is applied to the current drive circuit after performing signal processing on the recorded signal to realize the gist of the present invention. Because of this configuration, it can be applied regardless of the type of current drive circuit.

Moreover, it is applicable not only to VTR devices but also to all devices that use a rotary transformer.

〔Effect of the invention〕

As described above, according to the present invention, the rotary - It is possible to electrically correct the deterioration of the transfer characteristics of the transformer in the low frequency region, and by relaxing the design conditions of the rotary transformer, it has the effect of making the device cheaper.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a basic embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of the integrator shown in FIG. 1, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. FIG. 4 is a circuit diagram showing an example of the basic driving system of a conventional magnetic head, and FIG. 5 is a circuit diagram showing another example of the driving force system of a conventional magnetic head, which is the subject of improvement in the present invention. , FIG. 6 is a diagram showing the characteristics and equivalent circuit of a rotary transformer. In the figure, (1) is a recording signal input terminal, (4) is a current drive means (drive transistor), (5) is a magnetic head,
(7) is a rotary transformer, (the sub is an integrating means (integrator), and m is a combining means (adder). In addition, the same reference numerals in the figure indicate the same or corresponding parts. 1121 FIG. 2 Figure 4 Figure 5 Figure 6 (a) Circumstances, numbers (H2) (b) Procedural amendment (voluntary) Showa 2013, month, Z, day 3, person making the amendment 5, specification to be amended Detailed Description of the Invention Column and Figure 4 of the Drawings 6゜ Contents of Amendment fi+ The following is corrected on page 8, line 10 of the specification. +21 Figure 4 of the drawings is as shown in attached Figure m. Figure 4: At least one drawing showing the corrections in Figure 84 of the catalog of attached documents.

Claims (2)

[Claims] (1) In a device that supplies a recording current according to an input recording signal to a magnetic head via a rotary transformer, an integrating means integrates the input recording signal, and the output of the integrating means and the input recording signal are integrated into a predetermined manner. Comprising means for adding at a ratio, and current driving means for supplying a current corresponding to the output of the combining means to the primary circuit of the rotary transformer,
A current output device comprising: compensating for deterioration of current transfer characteristics of the rotary transformer in a low frequency region. (2) The current output device according to claim 1, wherein the characteristic time constant of the rotary transformer and the integration time constant of the integrating means are made equal.