JP2615340B2 - Magnetic recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording apparatus used for writing data on a recording medium such as a hard disk or a floppy disk.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional magnetic recording apparatus . This magnetic recording device is constituted by a semiconductor integrated circuit except for the magnetic heads 2A and 2B and the drive power supply 3. The magnetic heads 2A and 2B are provided corresponding to the two writing sides of the floppy disk, that is, the front and back surfaces (sides 0 and 1), and a common terminal is formed at the midpoint of each of the magnetic heads 2A and 2B. Have been.

In this magnetic recording apparatus , a magnetic head 2A,
Voltage output circuit 4A for applying the power supply voltage V _CC to the common terminal side of 2B, with 4B, corresponding to the side switching select each magnetic heads 2A, 2B, and a magnetic head 2A that is selected, the current flowing through the 2B Is provided with a current switching circuit 5 for switching the current.

That is, one voltage output circuit 4A includes transistors 6, 8, resistors 10, 12, 14 and a switch 15
A, and the other voltage output circuit 4B includes transistors 16, 18, resistors 20, 22, 24, and a switch 15
B. The switches 15A and 15B are switches for selecting the magnetic heads 2A and 2B to be driven.

The magnetic head 2A has its common terminal connected to a common terminal 26A formed on the emitter of the transistor 8, and connected between terminals 28A ₁ and 28A ₂ formed on the current switching circuit 5. The magnetic head 2B has a common terminal connected to a common terminal 26B formed on the emitter of the transistor 18 and also connected between terminals 28B ₁ and 28B ₂ .

The current switching circuit 5 has a terminal 28A
₁ , 28A ₂ and four NPN diode switches 31, 32, 34 provided for each of the terminals 28B ₁ , 28B ₂ ,
A pair of transistors 38 and 40 are provided with the emitters in common via 36. The four NPN diode switches 31, 32, 34, 36 are connected in series, because the breakdown voltage per switch is as low as 7V, so that they are combined.

The transistors 38 and 40 include a constant current source 4
2 is inverted by a current inverting circuit including transistors 44 and 46 and flows therethrough.
Are connected to resistors 48, 50 and voltage sources 54A, 54B via switches 52A, 52B so that a constant bias sufficient to conduct when switch 52A or 52B is closed is applied. Has become.

The driving power supply 3 includes a power supply terminal 56 and a ground terminal 5.
7 and V _CC is that voltage.

In this magnetic recording apparatus , the switches 15A,
15B, the magnetic heads 2A and 2B are selected.
A and 52B switch the direction in which current flows from the common terminals of the magnetic heads 2A and 2B, and switch the magnetic heads 2A and 2B.
The data is written on the floppy disk according to the magnetization and the direction of the data.

[0010]

By the way, this magnetic recording
In the recording apparatus , for example, when the power supply voltage V _CC is set to 5 V, the collector-emitter voltages of the transistors 6, 40, 46 are set to V _CE6 , V _CE40 , V _CE46 (= 0.1), the diodes 31, 32, The forward drop voltage at 34 and 36 is V
_{D31, V D32, V D34,} V D36 (= 0.7), the base-emitter voltage of the transistor 8 V _BE8 (= 0.7)
When the common terminal 26A- voltage V between the terminals 28A ₁
Is

[0011]

(Equation 1)

And its value is:

[0013]

(Equation 2)

## EQU1 ## Therefore, the magnetic heads 2A, 2A
The effective voltage applied to B is only about 1.2 V,
The operating voltage of the magnetic heads 2A and 2B, that is, the effective voltage range is small, and the power supply voltage V _CC needs to be set to be considerably high in order to realize reliable driving.

Therefore, in such a magnetic recording device ,
The circuit configuration is complicated, and it is not possible to increase the operating voltage or lower the driving voltage.

In order to selectively drive the two magnetic heads 2A and 2B with a single current switching circuit 5, a diode 3 is used as means for separating the magnetic heads 2A and 2B.
1, 32, 34, and 36 are used, but there is a problem that the diode characteristics greatly affect the drive current of the magnetic heads 2A and 2B. This magnetic recording device is I
C, but the diodes 31, 3
The formation of 2, 34 and 36 causes a parasitic current in the structure. The parasitic current is a current flowing on the IC substrate side in addition to the diode current flowing from the anode to the cathode. This parasitic current varies greatly from one IC to another and varies greatly, and its variation value reaches ± 50%. Such a parasitic current not only lowers the accuracy of the drive current but also makes it difficult to match the diode characteristics of each terminal of the magnetic heads 2A and 2B. For this reason, in the IC, in order to suppress the variation of the driving current and increase the accuracy, the diode 3
1, 32, 34 and 36 are obstacles.

Therefore, the present invention eliminates the adverse effects of using a diode and increases the operating voltage of a magnetic head.
It is an object of the present invention to provide a magnetic recording device that realizes a lower driving voltage.

[0018]

A magnetic recording apparatus according to the present invention comprises a plurality of magnetic heads (2A, 2B) connected to a power supply.
NPN type transistors are individually connected to each terminal of each coil.
NPN transistors (switches
Transistor 78 and switching transistor 8
0, switching transistor 92 and switching transistor
The emitters of the transistors 94) are connected in common,
A differential circuit (current switching circuit 6) installed corresponding to the head
0A, 60B) and a constant current source (10
4) receiving the constant current from the constant current source;
Current that draws the operating current from the differential circuit in response to the current
A mirror circuit (transistors 106 and 108) and the difference
The operation of each of the NPN transistors in the
The NPN type which is switched according to the level of the
From the common terminal through the transistor
By selectively passing current through each coil piece,
Operation switching means (switches 90A ₁ , 9
0A ₂ , 90B ₁ , 90B ₂ ) .

Further, the magnetic recording apparatus of the present invention has an intermediate structure.
It has a coil with a common terminal formed in front of this coil.
A plurality of magnetic heads (2
A, 2B), wherein the coil
NPN transistor (switching)
Transistor 78 and switching transistor 80
Switching transistor 92 and switching transistor
NPN transistors connected directly to the collector
The emitters of the magnetic head are connected in common,
A plurality of differential circuits (current switching circuits 60A, 6
0B), a constant current source (104) for generating a constant current,
Receives the constant current from the constant current source of
Current mirror circuit for drawing operating current from the differential circuit
And the operation of each of the NPN transistors of the differential circuit
Is switched according to the level of the base potential, and
Before the common terminal through an NPN transistor
By selectively applying current to each coil piece of the coil,
Operation switching means (switches) for exciting the coil pieces.
_{90A 1, 90A 2, 90B 1} , 90B 2) and wherein the <br/> further comprising a.

[0020]

In the magnetic recording apparatus according to the present invention, since a differential circuit is provided for each magnetic head, it is not necessary to use a diode for separation. As a result, the harmful effects of the diodes are prevented, and the coils of each magnetic head can be selectively excited by selectively switching each transistor of the differential circuit to the conductive state or the cutoff state.

Further, in the magnetic recording apparatus of the present invention, a constant current source circuit applies a constant current to each differential circuit to excite the coil pieces of the corresponding magnetic head, thereby simplifying the circuit configuration. Is being planned.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of the magnetic recording apparatus according to the present invention, and the same parts as those of the magnetic recording apparatus shown in FIG.

In FIG. 1, voltage output circuits 58A and 58B are provided for applying a power supply voltage V _CC to the common terminal of each of the magnetic heads 2A and 2B.
Current switching circuits 60A and 60B are provided as differential circuits for selectively supplying current to 2B.

The voltage output circuit 58A comprises a PNP transistor 62, resistors 64 and 66 and a switch 68A, and the voltage output circuit 58B comprises a PNP transistor 72, resistors 74 and 76 and a switch 68B. .

The current switching circuit 60A includes switching transistors 78 and 80 and a resistor 8 as a pair of transistors.
2, 84, constant current sources 86, 88 and switch 90A ₁ ,
It consists of 90A ₂ switching transistor 9, The current switching circuit 60B as a pair of transistors
2,94, resistors 96 and 98, and a constant current source 100, 102 and the switch 90B _1, 90B _2. The switching transistors 78 and 80 have their emitters combined to form a differential circuit. Similarly, the switching transistors 92 and 94 have their emitters combined to form a differential circuit.

The transistors 78, 80, 92,
A constant current source 104 and transistors 106 and 108 are connected to the constant current source 94 as a constant current source circuit.
The constant current generated in the transistor 04 flows into the transistors 106 and 108 forming a current mirror circuit, and a constant current is drawn into the transistor 108 from the differential circuit side by the current mirror effect.

The operation based on the above configuration will be described.

To select the magnetic heads 2A and 2B installed corresponding to the sides 0 and 1 of the floppy disk,
The switches 68A and 68B are selected and switched.

That is, when the switch 68A is closed,
The voltage output circuit 58A is activated and the magnetic head 2A
Is selected, and the magnetic head 2A can be supplied with current from the common terminal 26A by the drive power supply 3 via the transistor 62.

In this state, when writing data to the floppy disk, the switches 90A ₁ and 90A ₂ of the current switching circuit 60A are alternately switched.

In this case, since the side 0 is selected, the operation of the voltage output circuit 58B is stopped, and the switches 90B ₁ and 90B ₂ of the current switching circuit 60B are both closed.

Next, FIG. 2 shows the operation waveform, and A shows the write permission of the floppy disk and the prohibition thereof.
a ₁ is write-protected zone, a ₂ is a write permission section.
Correspondingly, B is write data, C is switch 90A
₁ switching, D is a switching of the switch 90A _2.

[0034] Here, when the switch 90A ₁ is opened, the switch 90A ₂ is closed, so that the bias sufficient to conduct the transistor 80 is given. That is, the constant current generated by the constant current source 104 flows to the transistor 80 by the current reversal action of the transistors 106 and 108, and the current sinking ability of the transistor 80 is determined by the constant current value.

On the other hand, the transistor 62 has a switch 68A
Is turned on by the conduction of the power supply terminal 5
A current path consisting of 6-transistor 62-common terminal 26A-magnetic head 2A-terminal 28A ₁ -transistor 80-transistor 108-ground point (GND) is formed, and the magnetic head 2A is connected from its common terminal 26A to terminal 28A ₁ . A current flows toward the transistor 80, and the current is absorbed by the transistor 80. As a result, the upper coil portion in the figure of the magnetic head 2A is excited.

Further, the switch 90A ₁ is closed, when the switch 90A ₂ is opened, the power supply terminal 56 - transistor 62 - common terminal 26A- magnetic head 2A- terminal 28A ₂ - transistor 78 - transistor 108-
A current path of the ground point (GND) is formed, and the magnetic head 2
The current flows from the common terminal 26A to the terminal 28A ₂ side A, so that the coils of the part is excited.

By switching the switches 90A ₁ and 90A _{2 in} this manner, the magnetic head 2A causes its common terminal 26
Since the exciting current flows around A, the coil portions on both sides thereof are alternately excited. For this reason, in the magnetic head 2A, voltages as shown in FIG. As a result, the data shown in FIG. 2B is written on the floppy disk.

The above operation is performed when the magnetic head 2A is selected. However, when the magnetic head 2B is selected, the voltage output circuit 58B is switched to the operating state and the current inverting circuit 60B is switched. , Magnetic head 2B
Is excited, and predetermined data is written to the floppy disk.

[0039] In such a magnetic recording apparatus, the transistors 62 and 80 (78), when the emitter-collector voltage of 108 to _{V CE62, V CE80, V CE108} , the voltage V applied to the magnetic head 2A is

[0040]

(Equation 3)

## EQU3 ## If V _CC = 5V, the value is:

[0042]

(Equation 4)

Is as follows. That is, the effective voltage applied to the magnetic head 2A reaches 4.5V even though the power supply voltage V _CC is as low as 5V, and the driving voltage can be reduced. That is, at the same drive voltage, the operating voltage of the magnetic head 2A is expanded. In this embodiment, the transistor 62 is a PNP transistor instead of the conventional NPN transistor 8, and the collector-emitter voltage V _CE62 is the base-emitter voltage V _BE (= 0. 7V), which is much smaller than that of the magnetic head 2 and can be ignored.
It contributes to the expansion of the operating voltage of A and 2B or the lowering of the driving voltage. Also, except for the voltage output circuits 58A and 58B,
The power supply voltage may be directly applied to the common terminal of each of the magnetic heads 2A and 2B. This contributes to an increase in the operating voltage and a reduction in the driving voltage.
The same applies to the magnetic head 2B.

Therefore, the magnetic recording device can be driven by a portable power source such as a dry battery, and a portable magnetic recording device can be realized.

In particular, since a logic circuit composed of a semiconductor integrated circuit is usually driven at 5 V, coordination with this logic circuit can be achieved and the power supply unit can be unified.
Along with the simplification of the design, the occupied volume of the power supply unit occupied in the device is reduced, and the device can be reduced in size and cost.

[0046]

As described above, according to the present invention, a pair of transistors in a differential circuit corresponding to each magnetic head are selectively turned on or off, so that the common terminal of the magnetic head is set to the center. Thus, since the coil pieces can be selectively excited and the diode is eliminated, the operating voltage of the magnetic head can be increased and the driving voltage can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a magnetic recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing operation waveforms of the magnetic recording device shown in FIG.

FIG. 3 is a circuit diagram showing a conventional magnetic recording device .

[Explanation of symbols]

 2A, 2B Magnetic head 60A, 60B Current switching circuit (differential circuit) 78, 80, 92, 94 Switching transistor 104 Constant current source (constant current source circuit) 106, 108 Transistor (constant current source circuit)

Claims (2)

(57) [Claims] A plurality of magnetic heads connected to a power supply;
NPN type transistor collector for each terminal of coil
The emitter of each NPN transistor directly connected to the
Connected to each other, and the difference
Operating circuit, a constant current source for generating a constant current, and receiving the constant current from the constant current source and corresponding to the constant current.
Current mirror circuit that draws the operating current from the differential circuit
And the operation of each of the NPN transistors of the differential circuit.
Switch in accordance with the level of the source potential
From the common terminal through the PN transistor,
By selectively passing current through each coil piece of the
A magnetic recording device , comprising: an operation switching unit that excites the coil piece . 2. A coil having a common terminal formed in the middle.
And the common terminal of the coil is connected to a power supply.
A magnetic recording apparatus having a plurality of magnetic heads, wherein each terminal of the coil is individually connected to a NPN transistor.
Emitter of each NPN transistor to which the collector is directly connected
Are connected in common and are installed corresponding to the magnetic head.
A plurality of differential circuits, a constant current source for generating a constant current, and receiving the constant current from the constant current source, corresponding to the constant current
Current mirror circuit that draws the operating current from the differential circuit
And the operation of each of the NPN transistors of the differential circuit.
Switch in accordance with the level of the source potential
From the common terminal through the PN transistor,
By selectively passing current through each coil piece of the
A magnetic recording device , comprising: an operation switching unit that excites the coil piece .