JPH06309606A - High requency modulation magnetic field generation circuit for magnetic recorder - Google Patents

Abstract

PURPOSE:To make a high frequency modulation magnetic field generation circuit for a magnetic recorder overwriting by a magnetic field modulation system low in power consumption and simple in circuit. CONSTITUTION:Plural first exciting coils 11-1m and second exciting coils 21-2n have the roughly same impedance respectively, and respective one ends are connected to a common connection point C, and the magnetic fields with reverse directions each other are generated by currents comming through the common connection point C. Plural control signals CT1-CTm+n are generated based on a clock signal CK with a frequency higher than a recording signal R and the recording signal R. Then, plural switching means 41-4m+n are switching- controlled by plural control signals CT1-CTm+n so as to turn on alternately any ones of plural first exciting coils 11-1m and plural second exciting coils 21-2n respectively at fixed timing according to the clock signal CK and by the roughly same ON-resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency modulation magnetic field generation circuit for a magnetic recording device, and more particularly to a high frequency modulation magnetic field generation circuit for a magnetic recording device for overwriting by a magnetic field modulation method.

[0002]

2. Description of the Related Art In recent years, with the development of electronic computers, magneto-optical disk devices have been demanded as low cost and large capacity auxiliary storage devices. In order to perform high-speed data recording by the magneto-optical disk device, various overwrite methods have been proposed. As one of them, recording is performed by modulating the direction of the bias magnetic field while keeping the laser light intensity constant. A magnetic field modulation method is known. As a method of modulating the bias magnetic field, there is a method of performing modulation by reversing the direction of the exciting current flowing through the exciting coil using, for example, a switching element.

An example of a high frequency modulation magnetic field generating circuit of a conventional magnetic recording device will be described below with reference to FIG.
In FIG. 5, the constant current sources J1 and J2 are supplied with a constant voltage V from the constant voltage source E, and supply predetermined constant currents to the compensation coils L1 and L2, respectively. An exciting coil LM is connected between both coils, and switching elements 51 and 52 such as transistors and MOSFETs are connected to each connection point. The inductance values of the compensating coils L1 and L2 are sufficiently larger than the inductance value of the exciting coil LM arranged at a predetermined distance from the magnetic recording medium (not shown).

Both switching elements 51 and 52 respond to a recording signal R inputted from the outside, and a switching control unit 5
The direction of the exciting current IM flowing through the exciting coil LM is modulated based on the recording signal R by being switching-controlled by 3. As a result, the bias magnetic field of the magnetic recording medium is high-frequency modulated to perform predetermined recording.

That is, the switching element 51 is turned off,
When the switching element 52 is on, the exciting current IM flows through the switching element 52 as shown by the solid line, and a magnetic field (in the positive direction) according to the direction of the exciting current IM is generated in the magnetic recording medium. At this time, the current source J2
A constant current I2 flows to the switching element 52 through the compensation coil L2, and the switching element 52 is saturated.

Next, when the switching element 51 is turned on and the switching element 52 is turned off, the current I2
Flows through the exciting coil LM as shown by a broken line to be an exciting current, and generates a negative magnetic field in the magnetic recording medium. At the same time, the current I2 flows into the switching element 51 together with the constant current I1 supplied from the current source J1 via the compensation coil L1, and saturates it after a predetermined switching time.

In the above circuit, a constant current is constantly flowing through the compensation coils L1 and L2, and by turning these currents into each switching element at the time of switching, the turn-on time of each switching element is shortened and switching is performed at high speed. In this case, the exciting coil LM is configured to supply an exciting current having a substantially constant amplitude.

[0008]

However, according to the high frequency modulation magnetic field generating circuit of the conventional magnetic recording device described above, there is a problem that power consumption is large and the circuit is complicated because the constant current circuit is used. It was

It is an object of the present invention to provide a high frequency modulation magnetic field generating circuit for a magnetic recording device which solves the above problems.

[0010]

The above problems can be solved by constructing according to the principle diagram of FIG.

That is, it is modulated based on the recording signal R.
By supplying the generated current to the exciting coil,
Generates a high frequency modulation magnetic field and magnetically records the high frequency modulation magnetic field
High frequency of magnetic recording device applied to medium D for magnetic recording
In the wave modulation magnetic field generation circuit,
And have one end connected to the common connection point C.
And the currents coming from common connection point C
Each of the plurality of windings is wound so as to generate a magnetic field in the opposite direction.
Excitation coil 1₁~ 1m and the second exciting coil 2 ₁~ 2n
(However, m and n are integers of 2 or more) and a constant voltage at one end
Drive coil with V coming in and the other end connected to common connection point C
3 has substantially the same on-resistance and one end of each
A plurality of first exciting coils 1₁~ 1m and multiple second excitation
Coil 2₁Multiple switches connected to the other end of each ~ 2n
Etching means 4₁~ 4m + n, higher than recording signal R
Based on the wave number clock signal CK and the recording signal R, a plurality of
Control signal CT₁~ Multiple CTm + n first exciting coils
1₁~ 1m and multiple second exciting coils 2₁~ 2n each
One of the shifts is a constant timing according to the clock signal CK
Switching means 4 so that they are turned on alternately by₁
Up to 4m + n multiple control signals CT₁~ Switch by CTm + n
The problem is solved by providing the control means 5 for controlling the pitching.
To be done.

[0012]

SUMMARY OF] According to the present invention having the above structure, a plurality of first exciting coil 1 ₁ to 1 m and a plurality of switching means 4 ₁ ～4M, and a plurality of second exciting coil 2 ₁ to 2n and a plurality of switching means 4m + _{1 to} 4m + n are respectively connected in series, and a constant voltage is input to the series circuit from the common connection point C via the drive coil 3. Then, the control means 5 generates a plurality of control signals CT _{1 to} CTm + n based on the clock signal CK having a higher frequency than the recording signal R and the recording signal R to generate a plurality of first exciting coils 11 _{1 to} 1m. And a plurality of second exciting coils 2 ₁
One ~2n each one at a certain timing according to the clock signal CK, and a plurality of switching means so as to alternately turned on at substantially the same on-resistance 4 ₁ ~4m + n a plurality of control signals CT ₁ By controlling the switching by ~ CTm + n, the current modulated based on the recording signal R is applied to the plurality of first exciting coils 1 _{1 to 1} m and the plurality of second exciting coils 2 _{1 to} 2n at a constant timing. The supplied magnetic fields alternately generate magnetic fields in opposite directions, and act to generate a high frequency modulation magnetic field.

[0013]

Next, an embodiment of the present invention will be described with reference to FIGS.

FIG. 2 is a circuit diagram of a high frequency modulation magnetic field generating circuit of an overwritable magneto-optical disk device. In FIG. 2, the constant voltage source E generates a constant voltage V and supplies it to one end of the drive coil LD. The constant voltage source E may be inside the device or outside the device.

The other end of the drive coil LD is connected to a common connection point C. The exciting coil LE is connected to the common connection point C.
One end of each of 1 and LE2 and LE3 and LE4 is connected. The exciting coils LE1 and LE2 (first exciting coils) are wound around a common magnetic core 10 in the same direction. The magnetic core 10 is arranged at a predetermined distance from a magneto-optical disk (magnetic recording medium) (not shown). Further, the magneto-optical disk is irradiated with laser light having a constant intensity.

On the other hand, the exciting coils LE3 and LE4 (second
(Exciting coils) are wound around a common magnetic core 10 in the same direction and in the opposite direction to the winding direction of the exciting coils LE1 and LE2. Exciting coils LE1 and LE2
And LE3 and LE4 are wound so as to have substantially the same inductance value and resistance value, respectively.

Further, the exciting coils LE1 and LE2 and L
MOS FETs Q1 and Q are connected to the other ends of E3 and LE4, respectively.
The sources of 2 and Q3 and Q4 (switching means) are respectively connected. The drains of the MOS FETs Q1 and Q2 and Q3 and Q4 are grounded.

MOS FETs Q1 and Q2 and Q3 and Q4
The gate is connected to the switching control unit 11 (control means)
Has been done. As a result, the MOS FETs Q1 and Q2 and Q
3 and Q4 are control signals from the switching controller 11.
C₁And C₂And C₃And C _FourAs described below
Switching is controlled. At this time, MOS FET Q1 and
The on resistances of Q2, Q3, and Q4 are set to be approximately the same.
ing.

When the MOS FET Q1 or Q2 is turned on,
A magnetic field in the positive direction is generated in the magnetic core 10 by the current flowing from the common connection point C to the exciting coil LE1 or LE2. On the other hand, when the MOS FET Q3 or Q4 is turned on, a magnetic field in the opposite direction is generated in the magnetic core 10 by the current flowing from the common connection point C to the exciting coil LE3 or LE4.

The switching control section 11 is composed of gate circuits 12, 13 and 14 and 15.
Each gate circuit 12 to 15 has a recording signal R and a clock signal.
CK is input, and the gate circuit 12 takes the AND of the recording signal R and the clock signal CK and outputs the control signal C ₁ . The gate circuit 15 has a recording signal R and a clock signal CK.
And the control signal C ₄ is output.

Further, the gate circuit 13 inhibits the recording signal R by the clock signal CK and outputs the control signal C ₂ .
The gate circuit 14 inhibits the clock signal CK by the recording signal R and outputs the control signal C ₃ . As a result, the switching control unit 11 generates the control signals C ₁ and C ₂ and C ₃ and C ₄ as shown in the timing chart of FIG.

In FIG. 3, (A) is a recording signal R,
(B) is a clock signal CK, (C) is a control signal C ₁ ,
(D) is the control signal C ₂ , (E) is the control signal C ₃ , (F)
Indicate the control signal C ₄ , respectively.

The clock signal CK has a duty ratio of 50% in a cycle T. The frequency of the clock signal CK is higher than the frequency of the recording signal R as shown in the figure, and T /
2 is sufficiently smaller than the minimum holding time Tmin of the recording signal R. Further, the edge of the clock signal CK and the edge of the recording signal R are synchronized in timing.

Therefore, for example, from time t ₁ to time t
During the high level period of the recording signal R up to ₂ , the control signal C
₁ and the control signal C ₂ are alternately set to the high level every time T / 2. As a result, MOS FET Q1 and MOS FET Q2 have T /
It turns on alternately every two hours.

On the other hand, for example, during the low level period of the recording signal R from the time t ₂ to the time t ₃ , the control signal C ₃ and the control signal C ₄ are alternately set to the high level every time T / 2. As a result, the MOS FET Q3 and the MOS FET Q4 are alternately turned on every time T / 2.

By controlling the switching of each of the MOS FETs Q1 to Q4 as described above, the energy loss per unit time is made constant regardless of the frequency and duty ratio of the recording signal R, and a constant current source is required. Instead, a constant current can always flow through each exciting coil.

Here, the value of the current flowing in each exciting coil in the circuit of FIG. 2 is obtained by calculation. Each MOS FET Q1
FIG. 4 shows an equivalent circuit after Laplace conversion when Q4 is switched and turned on. Excitation coils LE1 to LE
4 Le inductance, the inductance of the driving coil LD and L _3, the resistance value of each coil LE1~LE4 and LD are ignored. In addition, the output voltage of the voltage source E is V,
If the ON resistance of the MOS FET is set to R _ON , from Fig. 4,

[0028]

[Equation 1]

Inverse Laplace transform,

[0030]

[Equation 2]

Here, if Le >> L ₃ ,

[0032]

[Equation 3]

It becomes

Therefore, the term dependent on the inductance value is eliminated from the equation (3) representing the exciting current, and each MOS FET
Each time Q1 to Q4 are alternately turned on, the exciting current rises quickly.

Next, the exciting coils LE1 to L1 are turned on during the period T / 2 from when the MOS FETs Q1 to Q4 are turned on to when they are turned off.
The current value Ion consumed by E4 is obtained. From equation of the electromagnetic energy, V · Ion · (T / 2) = Ion 2 · R ON · (T / 2) + (Le · Ion 2/2) become (5).

Here, if fsw = 1 / T,

[0037]

[Equation 4]

[0038]

In the equation (6), V, fsw, and Le are constant values. Therefore, fsw is made constant by alternately turning on the MOSFETs Q1 to Q4 at a constant timing according to the clock signal, and each of the MOSFETs Q1 to Q4 is turned on.
By using Q4 having the same on-resistance R _ON , the current Ion consumed during T / 2 by the exciting coil, that is, the energy loss per unit time, is independent of the frequency and duty ratio of the recording signal R. The constant current can be always applied to the exciting coil without the need for a constant current source.

The drive coil LD and each exciting coil LE
The resistance values of 1 to LE4 have been calculated by ignoring them up to now, but the same result can be obtained by adding these values to the ON resistance R _ON of the MOS FET.

As described above, according to this embodiment, it is possible to always supply an exciting current having a constant amplitude value to the exciting coil without using a constant current source, and to realize low power consumption. Moreover, there is an advantage that the circuit configuration can be simplified.

[0042]

As described above, according to the present invention, the control means generates a plurality of control signals based on a clock signal having a frequency higher than that of the recording signal and the recording signal to generate a plurality of first exciting coils and a plurality of first exciting coils. Of the second excitation coils are switched on by a plurality of control signals so as to alternately turn on any one of the second excitation coils at a constant timing according to the clock signal, and are modulated based on the recording signal. Is supplied to the plurality of first exciting coils and the plurality of second exciting coils at a constant timing, so that the energy per unit time by the plurality of first exciting coils and the plurality of second exciting coils is increased. By always keeping the loss constant, the head can be driven with a constant current with low power consumption, and the circuit configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a timing chart showing the operation of the circuit of FIG.

FIG. 4 is a diagram for analyzing the circuit of FIG. 2 by Laplace transform.

FIG. 5 is a diagram showing an example of a conventional high frequency modulation magnetic field generation circuit.

[Explanation of symbols]

1 _1, ... 1 m the first exciting coil 2 _1, ... 2n second exciting coil 3, LD driving coil 4 _1, ... 4m + n switching means 5 control means 11 switching control unit D magnetic recording medium LE1, ... LE4 excitation Coil Q1, ... Q4 MOS FET

Claims (1)

[Claims] 1. A magnetic recording device for supplying magnetic field to a magnetic recording medium by supplying a current modulated based on a recording signal to generate a high frequency modulating magnetic field, and applying the high frequency modulating magnetic field to a magnetic recording medium to perform magnetic recording. In the high frequency modulation magnetic field generation circuit of the recording device, each has substantially the same impedance and one end of each is connected to a common connection point, so that magnetic fields in opposite directions are generated by currents coming from the common connection point. A plurality of first excitation coils and a plurality of second excitation coils each wound around, and a drive coil in which a constant voltage is applied to one end and the other end is connected to the common connection point, and the drive coils are substantially the same as each other. A plurality of switching means having resistance and one end of each of which is connected to the other end of each of the plurality of first exciting coils and the plurality of second exciting coils; On the basis of the clock signal and the recording signal of the wave to generate a plurality of control signals, a first plurality of
Switching control of the plurality of switching means by the plurality of control signals so that any one of the plurality of excitation coils and the plurality of second excitation coils are alternately turned on at a constant timing according to the clock signal. A high frequency modulation magnetic field generation circuit for a magnetic recording device, comprising: