JP2571604B2 - Magnetic recording / reproducing device - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing information,
In particular, the present invention relates to the improvement of noise generation prevention.

[Prior Art] With the advance of computer technology in recent years, the importance of magnetic recording / reproducing devices as external storage means has been increasing. For example, floppy disks are widely used as magnetic recording means in OA devices such as personal computers, microcomputers, and word processors. A floppy disk drive for writing and reading information on the floppy disk is widely used as a magnetic recording / reproducing apparatus.

In such a floppy disk drive, a magnetic head is brought into close contact with a magnetic recording surface of a floppy disk that rotates continuously at a constant speed, and information is written and read by a writing and reading coil built in the magnetic head.

Here, such a conventional magnetic recording / reproducing apparatus will be described with reference to FIG.

The magnetic head 10 is in close contact with the magnetic recording surface of a floppy disk, and writes and reads recorded information by a built-in write / read coil 12.

That is, when performing writing, a current signal according to desired recording information is supplied from the writing circuit 14 to the writing / reading coil 12.
To supply. The magnetizing action is performed along the tracks on the magnetic recording surface in a desired direction according to the direction of the current flowing through the write / read coil 12, and desired recording information is recorded along the tracks on the floppy disk.

The recorded information is read by detecting a current induced in the write / read coil 12 according to the direction of magnetization recorded on the magnetic recording surface of the floppy disk as a change in the potential between both ends of the write / read coil 12. .

Next, details of the reproducing circuit 100 will be described. The write / read coil 12 has a central portion connected to the COM terminal, and both ends connected to the bases 28b, 30b of the differential amplifying transistors 28, 30 via the diodes 20, 22 or the diodes 24, 26, respectively. I have.

Then, the bases 28b, 3 of the differential amplification transistors 28, 30
The power supply Vcc is connected to 0b via the resistors R1 and R2. The collectors 28c and 30c of the differential amplifying transistors 28 and 30 are also connected via a power supply Vcc resistor.

Further, predetermined resistors are respectively connected to the emitters of the differential amplifying transistors 28 and 30, and these resistors are grounded via the constant current transistor 32. The connection between the diodes 20, 22 and the connection between the diodes 24, 26 are grounded via constant current transistors 34, 36, respectively.

Further, the reproduction circuit constant current source 38 turns on and off the constant current transistors 32, 34, and 36 and controls the current value to a predetermined value. The output terminal 40 is a terminal for taking out the amplified reproduction output.

The detection of the induced current in the write / read coil 12 in such a reproducing circuit is performed as follows.

First, when reading is performed by the magnetic head 10, a bias voltage is applied from the reproduction circuit constant current source 38 to turn on the constant current transistors 32, 34, and 36, and the diodes 20, 22, and
24 and 26 are energized, and the transistors 28 and 30 for differential amplification operate. As a result, when the potential at both ends of the write / read coil 12 changes due to the induced current flowing through the write / read coil 12, the diodes 20, 22, 24, and 26 are in a conducting state. The potentials of the bases 28b, 30b of the transistors 28, 30 will change.

Here, the potentials of the bases 28b and 30b of the transistors 28 and 30 are set so as to be in an unsaturated state.
Therefore, the amount of current flowing between the collector and the emitter of the transistors 28 and 30 depends on the potential change of each base. And the emitters 28 of the transistors 28 and 30
Since e and 30e are grounded via the common transistor 32, a current flows through the transistors 28 and 30 in accordance with a potential change at both ends of the write / read coil 12.

The transistors 28 and 30 can amplify the current change in the base by about 100 times, and the amplified signal is output from the reproduction output terminal 40.

Here, if only a potential change at both ends of the write / read coil 12 is detected, the diodes 22, 26 and the resistors R1, R2
May be omitted, and both ends of the write / read coil 12 may be directly connected to the bases of the transistors 28 and 30. That is, even with such a circuit, the potential at the bases of the transistors 28 and 30 changes due to the potential change at both ends of the write / read coil 12, and accordingly, the transistors 28 and 30
The current flowing through changes. Therefore, a desired reproduction output can be obtained.

However, if the diodes 22 and 26 are not provided, a leakage current flows toward the power supply Vcc via the bases and collectors of the transistors 28 and 30 due to the back electromotive force generated in the write / read coil 12 at the time of writing information, and an error component is included in the write current. There is a problem that writing occurs and erroneous writing is performed. That is, when a pulse-like write current is supplied to the write / read coil 12, a large back electromotive force is generated at the time of rising and falling. If no current corresponding to the back electromotive force flows, there is no adverse effect. However, at the time of writing, although the constant current transistors 32, 34, and 36 are off,
Since a reproducing circuit is connected to the write / read coil 12, a current corresponding to the back electromotive force is applied to the transistors 28 and 30.
Flows towards Then, a leak current caused by such a back electromotive force flows into a circuit connected thereto.

For example, if this current flows into the magnetic head 10, an error component occurs in the write current, and an error occurs during reading. In addition, the magnetic head 10 has one
When a leakage current occurs through a magnetic head connected to the back surface, erroneous writing is performed on the back surface, and there is a possibility that previously written data is erased.

For this reason, it is necessary to prevent such a leak current, and it is necessary to arrange the diodes 22, 26 in a circuit to the bases 28b, 30b of the differential amplifying transistors 28, 30.

[Problems to be Solved by the Invention] As described above, in the conventional magnetic recording / reproducing apparatus, in order to prevent a leakage current, the diodes 22 and 26 are inserted into the signal input circuit to the bases of the transistors 28 and 30. Was needed.

However, when the diodes 22 and 26 are provided, the base resistance of the transistors 28 and 30 increases according to the operating resistance. For this reason, there is a problem that the input conversion noise voltage is deteriorated by the operating resistance. Further, an active element such as a diode generates a certain amount of noise as its property, and when this is input to a base, this noise is amplified. For this reason, there is a problem that even if the noise due to the diode is relatively small, non-negligible noise is included in the reproduced output.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to eliminate the need for diodes 22 and 26, suppress generation of noise, and prevent leakage current. The purpose is to provide.

[Means for Solving the Problems] A magnetic recording / reproducing apparatus according to the present invention comprises: a write / read coil for writing information to a magnetic recording medium and reading information from the magnetic recording medium; A write circuit that is connected and supplies a predetermined write current at the time of writing; and a reproducing circuit that is connected to both ends of the write / read coil and detects a potential change at both ends, wherein the read circuit includes the write / read coil. Are connected to a base, respectively, and a pair of differential amplification transistors whose current amount changes according to a potential change at both ends of the write / read coil; a common end of the pair of differential amplification transistors and a power supply. And a current flowing from the power supply to the pair of differential amplification transistors during reproduction, and A pnp transistor for blocking a current flowing from the differential amplification transistor toward the power supply; a base current control means connected to the base of the pnp transistor for supplying a base current during reproduction and stopping supply of the base current during writing And constant current means for regulating the sum of the amounts of current flowing through both of the pair of differential amplification transistors to a constant amount. The reproduction signal is generated by the amount of current flowing through each of the pair of differential amplification transistors. Take out the above pn
It is characterized in that a p-transistor blocks a current flowing toward a power supply via a differential transistor at the time of writing, thereby preventing noise from occurring.

[Operation] Writing of information to a magnetic recording medium such as a floppy disk and reading of information from the magnetic recording medium are performed by a write / read coil. That is, the writing of information to the recording medium is performed by supplying a predetermined writing current from the writing circuit to the writing / reading coil. Reading of information is performed by detecting a potential change at both ends of the write / read coil by a reproducing circuit.

Here, the reproducing circuit has a pair of differential amplifying transistors, and both ends of the write / read coil are connected to the base of the differential transistor, respectively. For this reason, the amount of current in the differential transistor changes according to the change in the potential at both ends of the write / read coil. Further, since the differential transistor is connected to the power supply and the constant current means, the sum of the current amounts flowing through both is constant. Therefore, a reproduced signal can be obtained by a relative change in the amount of current between the two transistors for differential amplification.

Further, in the present invention, a pnp transistor for preventing leakage current is arranged between the power supply and the common one end of the differential amplification transistor and the power supply. Therefore, even if a back electromotive force is generated in the write / read coil during writing to the recording medium, a leak current flowing from the back electromotive force toward the power supply via the base of the differential transistor is blocked by the pnp transistor. You. Therefore, there is no adverse effect on the magnetic head and the like. further
The pnp transistor is on / off controlled by the base current control circuit. For example, the transistor is turned on / off by a current of a transistor which is turned on during reproduction. So, pnp
When the transistor is turned on, it can be saturated and driven, the voltage drop there can be used as the saturation voltage of the pnp transistor, and the dynamic range of the differential transistor can be increased.

[Embodiment] A magnetic recording and reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.
4 shows a configuration in which a diode is arranged instead of the pnp transistor in the embodiment of the present invention. Here, the same members as those of the conventional example shown in FIG.

In this basic configuration, a circuit connected to the bases of the transistors 28 and 30 includes diodes 22 and 2 in FIG.
That is, no active element corresponding to 6 is provided.
Since the amount of current flowing through the constant current transistors 34 and 36 is constant, the base voltage of the transistors 28 and 30 changes due to the potential difference generated between both ends of the write / read coil 12 at the time of reading. Then, a reproduction output signal amplified in accordance with this is obtained at the output terminal 40.

As described above, according to the circuit having the basic configuration, since the diodes 22 and 26 are not provided, no noise is generated based on the diodes 22 and 26, and reading with high accuracy can be performed.

In this basic configuration, the transistors 28, 3
A current blocking diode 60 is provided as a leak current blocking element between the zero collectors 28c and 30c and the power supply. The leakage current blocking diode 60 can prevent the leakage current based on the back electromotive force generated in the write / read coil 12 at the time of writing from flowing into the power supply.

Here, as the diode for preventing leakage current,
A pnp diode is suitable. This is because the pnp diode has a higher breakdown voltage than the npn diode. In particular, when a voltage of about 5 V is adopted as the power supply Vcc, n
A pnp diode or a pnp diode may be used, but when a voltage of about 12 V is employed as the power supply Vcc, a pnp diode is preferable.

According to this basic configuration, the leak current blocking diode 60 can prevent the leak current flowing from the bases of the transistors 28 and 30 to the collectors. Thereby, generation of noise in the reproduction output can be minimized.

Next, FIG. 2 is a circuit diagram of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. In this embodiment, a leakage current blocking transistor 70 is employed in place of the leakage current blocking diode 60 having the basic configuration.
The base of the leakage current blocking transistor 70
70b is connected to the power supply Vcc via a resistor 72. The resistor 72 is grounded via a resistor and a constant current transistor 74.

Therefore, when the constant current transistor 74 is on at the time of reading, a predetermined constant current flows here. The pnp transistor is used as the leakage current blocking transistor 70. When the base current is supplied by the constant current transistor 74, the transistor 70 is turned on. Therefore,
When reading, this transistor for preventing leakage current
70 is turned on, a predetermined current flows through the differential amplifying transistors 28 and 30, and a change in the current of the write / read coil 12 can be amplified and output.

At the time of writing, the constant current source 38 turns off the constant current transistors 32, 36, 34, and 74. In this state, the base current of the leakage current prevention transistor 70 is not supplied by the constant current transistor 74,
If 72 is made sufficiently large so that the current flowing into the resistor 72 due to the back electromotive force can be ignored, the leakage current blocking transistor 70 is cut off. Since the leakage current blocking transistor 70 is formed of a pnp transistor, the leakage current flowing toward the power supply Vcc can be effectively blocked by the transistor 70.

Further, according to this embodiment, since the leakage current blocking transistor 70 is used, if this is saturated at the time of reading, the voltage drop here is very small. Therefore, the current in the differential amplification transistors 28 and 30 can be increased, and the reproduction output can be increased.

[Effects of the Invention] As described above, according to the magnetic recording / reproducing apparatus of the present invention, it is possible to prevent the leakage current from flowing into the power supply or the like, but to prevent the leakage current from flowing into the base circuit of the differential amplification transistor. There is no need to insert a blocking diode,
It is possible to suppress noise from being mixed into the reproduction output. In particular, since a pnp transistor whose base current is turned off at the time of writing is adopted as a leak current blocking element, the voltage drop in the pnp transistor during reproduction can be suppressed to the saturation voltage of the pnp transistor, and suitable amplification of the reproduction signal is achieved. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a magnetic recording / reproducing apparatus according to a basic configuration example of the present invention, FIG. 2 is a circuit diagram showing a configuration of a magnetic recording phase value according to an embodiment of the present invention, FIG. FIG. 2 is a circuit diagram showing a configuration of a conventional example. 12 Write coil 14 Write circuit 28, 30 Transistor for differential amplification 32, 34, 36 Constant current transistor (constant current means) 60 Diode for preventing leakage current (leakage current prevention element) 70 …… Leakage current prevention transistor (leakage current prevention element) 100 …… Regeneration circuit

Claims (1)

(57) [Claims] 1. A writing / reading coil for writing information on a magnetic recording medium and reading information from the magnetic recording medium, and a writing circuit connected to both ends of the writing / reading coil for supplying a predetermined writing current at the time of writing. And a reproducing circuit connected to both ends of the write / read coil and detecting a potential change at the both ends, wherein the read circuit has both ends of the write / read coil connected to a base, respectively, A pair of differential amplifying transistors whose current amounts change in accordance with potential changes at both ends, and a pair of differential amplifying transistors are disposed between a common end of the pair of differential amplifying transistors and a power supply. A current flowing to the differential amplification transistor flows from the differential amplification transistor to the power supply during writing. A pnp transistor for blocking, a base current control means connected to the base of the pnp transistor for supplying a base current at the time of reproduction and stopping supply of the base current at the time of writing, and flowing to both of the pair of differential amplification transistors A constant current means for regulating the sum of the current amounts to a constant amount, wherein a reproduction signal is extracted by the current amount flowing through each of the pair of differential amplification transistors, and the pnp
A magnetic recording / reproducing apparatus wherein a transistor blocks a current flowing toward a power supply via a differential transistor at the time of writing, thereby preventing generation of noise.