JPH087239A - Magnetic signal recorder - Google Patents

Abstract

PURPOSE: To obtain a magnetic signal recorder capable of preventing unintended erasing of record data following the disconnection, and the like of a head. CONSTITUTION: A record current is supplied form two current sources 6, 7 which are performed pushpull controlling to a head coil 10 with an intermediate tap of a magnetic record head 11. In order to prevent unintended erasing of record data when a record circuit is unbalanced due to failure, damages, etc., voltage dividers 14, 15 are connected in parallel to the head coil 10. Based on a signal on a tap 16 of this divider, the current sources 6, 7 are turned off by circuits 17 to 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording head in which a winding end of a head winding is controlled by a signal to be recorded.
The present invention relates to a magnetic signal recording device in which an intermediate tap of the head winding is connected to output terminals of two current sources and is connected to a first fixed potential point.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus having a rotary scanning system, an electric signal is transmitted from a stationary portion to a rotating portion of the scanning system during a recording operation. The rotating part of the scanning system (for example the rotating upper cylinder or the rotating head wheel) is
At least one magnetic head is provided around the periphery thereof, and a signal for magnetic recording on the magnetic carrier is supplied to the head via a rotary transformer. In order to magnetically record a signal in a very wide band, an amplifier is inserted in the signal path between the rotor winding of the rotary transformer and the magnetic head, and the amplifier generates a recording current required for the magnetic head. In addition, the current is directly supplied to the head winding of the magnetic head in the shortest possible path.

A circuit for recording a wideband signal is known from DE-A-3705930 A1, which circuit comprises two transistors of a differential amplifier. The base terminals of these transistors are connected to the rotor winding of the rotary head, and the collector terminals are connected to both ends of the head winding with an intermediate tap of the magnetic recording head. The operating voltage of the two transistors is supplied via the center tap of the head winding. In the above circuit, when unintentional erasure of the magnetic tape occurs due to imbalance such as transistor stage failure, head winding disconnection or lead wire disconnection between the head winding and collector terminal, etc. There is. The probability of such erasure due to damage increases as the number of recording heads used increases. Magnetic tape devices currently on the market for recording / reproducing digital HDTV signals have a rotary scanning system in which 16 rotary head discs are mounted along the circumference of the head disc. 16 rotary recording amplifiers for a magnetic recording head of Therefore, especially when the above HDTV magnetic tape device is used, it is desirable to prevent unintentional erasure of an image that is stored on the magnetic tape and cannot possibly be reproduced. .

For the purpose of detecting head disconnection and erroneous data recording at the time of data recording operation, a comparison circuit is assigned to the recording / reproducing amplifier circuit for monitoring the base voltage and the emitter voltage. A circuit is known which has a cascade connection of a transistor and a differential amplifier, and in which the magnetic head without a center tap is inserted between the transistor circuits (Japanese Patent Laid-Open No. 4-24).
8111). However, this known circuit cannot prevent erasure due to circuit damage. Moreover, this known amplifier circuit is not suitable for magnetically recording wideband signals with data rates of, for example, over 160 Mbit / s.

[0005]

OBJECT AND SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic signal recording apparatus as described at the beginning of the present specification, which apparatus can prevent unintentional erasure. is there.

The object of the present invention is to provide a voltage divider connected in parallel with the head winding and a circuit for cutting off the current of the current source in response to a signal extracted from a tap of the voltage divider. To be achieved.

The device according to the invention has the advantage that even in the case of an amplifier circuit for wideband recording, unintentional erasure of the magnetic tape due to the imbalance of the amplifier circuit resulting from damage can be eliminated.

In a concrete embodiment of the magnetic signal recording apparatus according to the present invention, each emitter terminal is connected to a second fixed potential point through each of a first resistor and a second resistor, and each base-emitter terminal is connected. Is supplied with the signal to be recorded, first and second transistors having collector terminals connected to winding ends of the intermediate tapped head winding of the magnetic recording head, and the voltage divider at the base terminal. A third transistor having the emitter terminal connected to the first fixed potential point, the emitter terminal connected to the second fixed potential point, and the collector terminal connected to the second fixed potential point. Are respectively connected to the bases of the first and second transistors, each base terminal is connected to the collector terminal of the third transistor, and the second fixed potential is connected via a third resistor. A fourth and fifth transistors connected to, is provided. With such an amplifying structure, it is possible to generate a wide-band, distortion-free recording current extracted from a signal voltage whose limit frequency is set to exceed 80 MHz.

According to another embodiment of the present invention, each emitter terminal is connected to the second fixed potential point via a fourth resistor, and each base terminal connects a fifth and a sixth resistor. A sixth transistor connected to the emitter terminals of the first and second transistors and via which the signal to be recorded is input, and collector terminals thereof connected to the base terminals of the first and second transistors, respectively; And a seventh transistor are provided.

In this embodiment, the input resistance of the recording amplification section is so low that even a low frequency signal component of the input signal can be transmitted by the rotary transformer. Further, as a result of the current feedback to the input stage transistor, there is an advantage that it is not necessary to pair the final transistor that generates the recording current.

Furthermore, according to another embodiment of the present invention, the device according to the present invention can be turned off not only due to damage but also in response to an operation.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a stationary winding (stator winding) of a rotary transformer 2 is designated by reference numeral 1. This static winding 1 is connected to a signal generator 3, which has an internal resistance 4. This signal generator 3 generates a recording signal, which is a result of the inductive coupling of the rotary transformer 2.
It is transmitted from the stationary winding 1 to the rotor winding 5.

The rotary transformer 2 acting as a signal transmission path
Are arranged in a rotary scanning system, which system comprises, for example, stationary cylinders arranged concentrically to one another and a rotary head wheel disk which rotates concentrically in the gap between the two cylinders. Have A plurality of recording, reproducing and erasing magnetic heads are mounted along the circumference of the head wheel disk, and these heads scan the magnetic tape spirally wound around the above-mentioned concentrically arranged cylinders. .

As described at the beginning of this specification, an amplifier is inserted in the signal transmission path between the individual rotor windings and the magnetic heads corresponding to these windings, and an amplifier is inserted between the recording and reproduction channels. Improve the signal-to-noise ratio of. In FIG. 1, the recording signal extracted from the rotor winding 5 drives two controllable current sources 6 and 7 by push-pull, and the output terminals of these current sources are magnetically recorded via terminals 8 and 9. Each of the head windings 10 with a center tap of the head 11 is connected to a winding end.

The center tap (terminal 12) of the head winding 10 is connected to the positive operating voltage point (terminal 13). Two series-connected resistors 14 and 15 are connected in parallel with the head winding 10. The base of the PNP transistor 18 is connected to the tap 16 of the resistors 14 and 15 connected in series via the resistor 17. The P
The emitter terminal of the NP transistor 18 is connected to the positive operating voltage point (terminal 13). The base-emitter path of the PNP transistor 18 is bypassed by the capacitor 19. The collector terminal of the PNP transistor 18 is grounded via the resistor 20 and is also connected to the base terminals of the two NPN transistors 21 and 22, and the emitter terminals of these transistors 21 and 22 are grounded. The collector terminals of the NPN transistors 21 and 22 are connected to the control input terminals of the current sources 6 and 7, respectively. A capacitor 23 is inserted in the line of the rotor winding 5 for DC separation.

The basic circuit shown in FIG. 1 has the following operation modes. That is, the signal of the signal generator 3 induced in the rotor winding 5 by the stationary winding 1 controls the current sources 6 and 7 to operate in the push-pull mode. In this case, opposite alternating currents flow through the output terminals of the current sources 6 and 7 at the timing of the alternating voltage of the input signal, and these currents follow the winding direction of the head winding 10 (see the position of the flow point). Since the vector-wise addition is performed, a leakage magnetic field is generated in the gap range of the magnetic recording head 11,
The magnetic field completely magnetizes the magnetic tape 24 passing through the head surface of the magnetic head 11.

Not only the AC recording current but also the DC current flows through the head winding 10 of the magnetic head 11 to set the operating points of the current sources 6 and 7. Since the two sub windings of the head winding 10 are wound in opposite directions, the DC magnetic field is compensated,
Therefore, in a normal recording operation, the magnetic tape 24 is not erased as a result of the DC magnetic field. However,
When one end of the head winding 10 is broken and separated during the recording operation, the compensation of the DC magnetic field is lost, so that the information recorded on the magnetic tape is erased by the DC magnetic field generated later in the gap range of the magnetic head 11. To be done. In order to cope with such an unintentional erasure, the current sources 6 and 7 should be protected against damage.
The current that flows through is blocked by appropriate control by the transistors 21 and 22. These transistors 21
The control currents required for 22 and 22 are generated by resistors 14 and 15 combined in parallel with the head winding. During a recording operation without a fault, that is, when all the head lines are connected, there is no current flowing through the resistors 14 and 15, and the PNP transistor 18 remains off. On the other hand, when there is a disconnection in the sub winding of the head winding 10 or in the supply wire of the head winding, current flows through the resistors 14 and 15, and the emitter-collector path of the PNP transistor 18 becomes conductive. However, at that time, a time delay occurs depending on the value of the time constant formed by the capacitor 19 and the resistor 17. When the PNP transistor 18 becomes conductive, the NPN transistors 21 and 22 also become conductive, and as a result, the current sources 6 and 7 are turned off.

The basic circuit diagram of FIG. 1 is shown in a more specific form in FIG. The signals that can be extracted from the rotor winding 5 are fed to the base terminals of the transistors 25 and 26, whose emitter terminals are the resistor 27.
Grounded through. The collector terminal of the transistor 25 is connected to the base terminal of the transistor 28, the output terminal of the current source 29, and the collector terminal of the transistor 22. Based on the symmetry of the circuit, the transistor 2
The collector terminal of 6 is the base terminal of the transistor 30,
It is connected to the output terminal of the current source 31 and the collector terminal of the transistor 21. The input terminals of the current sources 29 and 31 are connected to the positive potential point (terminal 13). The emitter terminal of the transistor 28 is grounded via the resistor 32, and is connected to the base terminal of the transistor 25 via the resistor 33. The emitter terminal of the transistor 30 is grounded via the resistor 34, and the resistor 35 connects the emitter terminal of the transistor 30 to the base terminal of the transistor 26.

Similar to the basic circuit diagram of FIG. 1, in the specific embodiment shown in FIG. 2 also, two resistors 14 connected in series are connected.
And 15 are connected in parallel with the head winding 10 of the magnetic recording head 11. The terminal 8 is connected to the collector terminal of the transistor 28, the terminal 9 is connected to the collector terminal of the transistor 30, and the terminal 12 is connected to the terminal 13. The series connected tap point 16 of resistors 14 and 15 configured as a voltage divider is connected via resistor 17 to the base terminal of a PNP transistor 18.
The emitter terminal of 8 is connected to the positive potential point (terminal 13). The collector terminal of the PNP transistor 18 is connected to the base terminals of the transistors 21 and 22, and the collector terminal of the transistor 18 is a resistor 2
It is grounded through 0 and the signal generator 36. The signal generator is used to turn the recording amplifier on or off. The emitter terminals of the transistors 21 and 22 are each grounded.

In the circuit shown in FIG. 2, the circuits of the transistors 25 and 28 take over the function of the first current source 6 shown in FIG. 1, and the circuits of the transistors 26 and 30 are the second.
The function of the current source 7 is taken over, and these are the magnetic recording head 1.
A recording current is supplied to the two sub windings of the head winding 10 of No. 1. In this case, the transistors 28 and 30 are the last transistors of the current sources 6 and 7, and the offset is compensated by the current feedback of the corresponding transistors 25 and 26. The current gain v _i of the current source can be calculated based on the following equation.

V _i = (R32 + R33) / R32 and v _i =
(R34 + R35) / R34

The final transistors 28 and 30 should have substantially the same high frequency characteristics as the transistors 25 and 26. However, the final transistors 28 and 30 are less than a pair thanks to the current feedback. Since the input impedance of the current source is about 3 ohms, when the internal resistance of the signal generator 3 is 100 to 200 ohms, the very low frequency signal component of the input signal can also be transmitted by the rotary transformer 2.

Transistors 21 and 22 shut off the current source if damaged. In this case, it is detected with the help of the PNP transistor 18 whether a current is flowing through the resistors 14 and 15. In the event of damage, current will flow through resistors 14 and 15, causing PNP
Transistor 18 is conducting and therefore transistors 21 and 22 are also conducting. Therefore, the base terminals of the final transistors 28 and 30 are grounded, and the current flowing through the emitter-collector paths of these final transistors 28 and 30 is cut off.

Although the current sources 29 and 31 are constructed as constant current sources, they may be resistors.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic circuit of a magnetic signal recording device according to the present invention,

FIG. 2 is a circuit diagram showing a specific circuit of the magnetic signal recording device according to the present invention.

[Explanation of symbols]

1 ... Static winding, 2 ... Rotating transformer, 3 ... Signal source, 5 ... Rotor winding, 6, 7 ... Current source,
8, 9 ... Terminal, 10 ... Head winding,
11 ... Magnetic recording head, 12 ... Intermediate tap,
18 ... 3rd transistor, 20 ... 3rd resistance, 21 ... 5th transistor, 22 ... 4th transistor, 25 ... 6th transistor, 26 ... 7th transistor,
27 ... Fourth resistance, 28 ... First transistor,
30 ... 2nd transistor, 32 ... 1st resistance, 33 ... 5th resistance, 34 ...
2nd resistance, 35 ... 6th resistance.

Claims (6)

[Claims] 1. A head end of a head winding of a magnetic recording head is connected to output terminals of two current sources controllable by a signal to be recorded, and an intermediate tap of the head winding has a first fixed potential. In a magnetic signal recording device connected to a point, a voltage divider connected in parallel to the head winding, and a circuit for turning off the current of the current source based on a signal extracted from a tap of the voltage divider. A magnetic signal recording device comprising: 2. The magnetic signal recording device according to claim 1, wherein each emitter terminal has a second resistor via a first resistor and a second resistor, respectively.
Connected to a fixed potential point, the signal to be recorded is supplied between each base-emitter terminal, and each collector terminal is connected to a winding end of the intermediate tapped head winding of the magnetic recording head. 1 and a second transistor, a base terminal to which the signal extracted from the tap of the voltage divider is supplied, a third transistor whose emitter terminal is connected to the first fixed potential point, and each emitter terminal The collector terminal is connected to the second fixed potential point, the collector terminals are connected to the bases of the first and second transistors, respectively, and the base terminals are connected to the collector terminals of the third transistor and the third terminal. And a fourth and a fifth transistor connected to the second fixed potential point via a resistor. 3. The magnetic signal recording device according to claim 2, wherein each emitter terminal is connected to the second fixed potential point through a fourth resistor, and each base terminal has a fifth resistor and a sixth resistor. Connected to the emitter terminals of the first and second transistors through the input of the signal to be recorded and the collector terminals of which are connected to the base terminals of the first and second transistors, respectively. A magnetic signal recording device having a sixth transistor and a seventh transistor. 4. The magnetic signal recording device according to claim 2 or 3, wherein base terminals of the first and second transistors are connected to a constant current source, respectively. apparatus. 5. The magnetic signal recording device according to claim 2, wherein a signal source for switching a recording current to an on state or an off state is connected in series to the third resistor. A magnetic signal recording device characterized by the above. 6. The magnetic signal recording apparatus according to claim 1, wherein the signal to be recorded is supplied via an inductive transmitter. And a magnetic signal recording device.