JP3140564B2 - Magnetic head 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 head device used in a magneto-optical recording device of a magnetic field modulation system.

[0002]

2. Description of the Related Art Conventionally, as a recording method of a magneto-optical recording apparatus, an optical modulation method, a magnetic field modulation method, and the like are known.
In particular, a magnetic field modulation method capable of directly writing (overwriting) new data on old data is excellent. FIG. 21 is a diagram showing a schematic configuration of the magnetic field modulation system. Reference numeral 1 denotes a magneto-optical disk serving as an information recording medium, and reference numeral 2 denotes a magneto-optical recording layer provided on the disk. The magneto-optical disk 1 is driven by a spindle motor (not shown).
It rotates at a constant speed. A magnetic head 3 is provided on the upper surface of the magneto-optical disk 1, and an optical head 4 is provided on the lower surface so as to face the magnetic head 3. When recording information, the optical head 4 irradiates a laser beam of a semiconductor laser provided as a light source inside the optical head 4 as a minute light spot on the recording layer 2 to raise the temperature of the recording portion to the Curie temperature or higher. On the other hand, the magnetic head 3 generates a bias magnetic field modulated in accordance with recording information by driving of the driving circuit 5, and applies the bias magnetic field to a temperature rising portion of the recording layer 2. As a result, the direction of the magnetization of the temperature-raised portion on the recording layer 2 is oriented in the direction of the bias magnetic field. Is fixed in the direction of the bias magnetic field. Thus, the recording layer 2
Above, a series of information is recorded as minute pits whose magnetization direction corresponds to the information signal.

[0003] In recent years, higher-density and higher-speed information recording has been required, and various studies have been made. For example, as a recording method for increasing the recording density,
There is a so-called pit edge recording method in which digital signals to be recorded correspond to both ends (edges) of the pit, that is, positions where the direction of magnetization is reversed. In this recording method, it is necessary to clearly record the edges of the pits in order to obtain sufficient reproduction signal reliability. Particularly, when performing high-speed recording in which a high-frequency signal is recorded by speeding up the rotation of the disk,
The polarity of the magnetic field of the magnetic head must be reversed in a very short time. Therefore, the switching time of the drive current for generating the modulation magnetic field to be supplied to the magnetic head is required to be short, and in order to perform high-speed and high-density information recording, a high-performance A head device is desired.

[0004] As such a magnetic head device, for example, one disclosed in Japanese Patent Application Laid-Open No. 63-94406 is known. FIG. 22 is a circuit diagram showing the magnetic head device. Reference numeral 7 denotes a magnetic head for generating a bias magnetic field;
₁ and L ₂ are auxiliary coils. The magnetic head 7 has a coil wound around a magnetic core (not shown), and generates a magnetic field modulated according to the information signal by switching the direction of the current supplied to the coil in accordance with the information signal. T ₁ , T ₂
Is a switching element, and a field effect transistor is generally used to switch a current of 100 mA or more at high speed. 8 and 9 are gate drive circuits for driving the switch elements T ₁ and T ₂ .

In the magnetic head driving device described above, digitized information signals S ₁ and S ₂ are input to the gate driving circuits 8 and 9 from a control unit (not shown). Information signals S ₁ and S
_The phase of ₂ is inverted. If the information signal S ₁ is “1”, S ₂ is “0”, and if S ₁ is “0”, S ₂ is “1”. The gate drive circuits 8 and 9 generate drive voltages having the same phase as the input information signals, and switch elements T ₁ ,
It applied to the gate of T _2. Thereby, the switching element T
₁ and T ₂ are alternately turned on, and the current supplied to the magnetic head 1 switches its direction in accordance with the information signals “1” and “0”. Therefore, the current of the magnetic head 7 alternates and generates a modulation magnetic field whose polarity is switched according to the information signal. here,
As is well known, the auxiliary coils L ₁ , L ₂ are connected to the switch elements T ₁ ,
ON T _2, regardless off, always is supplied with a constant current, but that act to invert faster the current of the magnetic head 1.

[0006]

In general, the smaller the inductance of the magnetic head, the more suitable it is for inverting the supply current at a high speed. The larger the inductance is, the larger the driving voltage is required for reversing the current at a high speed. It is necessary and a practical drive cannot be realized. For this reason, the inductance of the magnetic head is conventionally kept small, but the smaller the inductance, the lower the current efficiency of the generated magnetic field strength. Need to be increased. However, when the current of the magnetic head is increased, the power consumption of the driving device is increased, which contradicts the recent demand for miniaturization of the device, and realizes a high-speed magnetic field reversal and a small driving device. Was difficult.

Further, in the related art, the magnitude of the alternating current supplied to the magnetic head depends on the power supply voltage and the on-resistance of the field-effect transistor. In fact, the magnitude of the alternating current of the magnetic head is not constant due to various factors. In addition, as another characteristic of the driving device, the driving device has a property that the magnitude of the current changes depending on the frequency of the information signal. As described above, in the conventional magnetic head device, since the magnitude of the current of the magnetic head fluctuates or differs from device to device, the magnetic field generated by the magnetic head also fluctuates or differs depending on the device.
When recording information, the recording conditions are not constant, and the reliability of information recording may be impaired. Further, conventionally, it is necessary to switch the magnetic field of the magnetic head at a high speed. However, if an abnormality occurs in the switching time of the generated magnetic field for some reason, an abnormality occurs in information recording, and particularly, the pit edge described above. Since high speed reversal of the magnetic field is an essential condition in recording, there is a problem that a recording error occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic head device capable of performing high-speed magnetic field reversal without increasing power consumption. .

[0009]

[0010]

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic head.
The direction of the current supplied to the main coil of the
A magnetic head device that alternately switches the
The head device includes a first current path (CH1) and an auxiliary coil.
Including the second current path (CH3) and the switch element
For switching the current supplied to the main coil
In this case, first, the switching of the switch element
In addition to causing the current coil to oscillate,
Second current path a current I ₂ to the main coil from (CH3)
Supply and supply to the main coil by the oscillation phenomenon of the current
After the current to be reached reaches a maximum, the first current path
(CH1), the current I ₁ and the second current path (C
H3), the current I ₂ is supplied to the main coil.
Further, the current is supplied to the main coil by the oscillation phenomenon of the current.
Energy loss when the maximum current
Assuming that the corresponding decrease in current is ΔI, I ₂ > ΔI
With this, the current supplied to the main coil is switched off.
Immediately after the replacement, the voltage is instantaneously increased to a value greater than I ₁ + I _2.
The following is achieved by a magnetic head device characterized by I ₁ + I ₂ .

[0012]

[0013]

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, the basic principle of the magnetic head device of the present invention will be described. FIG. 3 is a diagram showing an example of a magnetic field generated by the magnetic head according to the present invention. In FIG. 3, + H ₁ is the peak magnetic field intensity that instantaneously reaches when the magnetic field is reversed to a positive polarity, and + H ₃ is the steady state magnetic field intensity in the positive polarity. Further, -H ₁ magnetic field intensity of the peak is reached instantaneously when the magnetic field is inverted to the negative polarity, -H ₃ is a magnetic field intensity of the steady state in the negative polarity. Furthermore, ± H ₂
Is the magnetic field strength of a conventional magneto-optical recording device. In the present invention, by strengthening the magnetic field strength instantaneously ± H ₁ Thus, without increasing the supply current of the magnetic head, is that attempts to record information. Hereinafter, the details will be described.

FIG. 4 is a diagram showing a waveform of a normal applied magnetic field in the magneto-optical recording apparatus. Here, the magnetic field intensity is changed stepwise as indicated by a, b, and c. a is ±
H ₁ and b are ± H ₂ and c is ± H ₃ , which correspond to the magnetic field intensity shown in FIG. FIG. 5 is a diagram showing the relationship between the magnetic field intensity and the amount of jitter of a reproduced signal when information recorded by the magnetic field shown in FIG. 4 is reproduced. Here, the jitter amount is defined by quantifying the temporal fluctuation width of the edge portion of the reproduction signal as indicated by J in FIG. FIG.
In the case where recording information in the magnetic field strength of ± H ₁ shown in a, the amount of jitter of the reproduced signal is not the change in the jitter amount increases J _1, and the magnetic field strength more, it is saturated . Here, it is defined as the amount of jitter in order to ensure the reliability of the reproduced signal is J ₀ or less. Further, when information is recorded with a magnetic field strength of ± H ₂ shown in b,
Jitter amount of the reproduced signal becomes smaller than J ₂ becomes, J _0. Further, the jitter amount of the reproduced signal when recorded at a magnetic field strength of ± H ₃ shown in c is J ₃ , and J ₀
It becomes a value larger than. The present invention is based on the results of further studies based on the relationship between the magnetic field strength and the amount of jitter as described above. That is, if a high-intensity magnetic field is instantaneously applied when the magnetic field is reversed as shown in FIG. 3, the amount of jitter of the reproduced signal is a value sufficient for practical use even when the magnetic field in a steady state is low in intensity. Based on the fact that the magnetic field ± H _{1 is} strong enough to record when the field reverses.
Is applied instantaneously, even if the steady-state magnetic field ± H ₃ is a magnetic field that is insufficient for recording, the jitter amount of the reproduced signal is sufficiently low, and does not affect the recording and reproduction of information at all. Things. In other words, if a sufficient magnetic field is applied when the edge of the information pit is formed when the magnetic field is reversed, the edge of the pit is clearly formed. Therefore, the signal can be reproduced favorably. According to the present inventor's experiments, to record information under the conditions of the magnetic field in FIG. 3, the jitter amount when playing it was a level of J ₂ in FIG. That is, the jitter amount was the same as the jitter amount when recording was performed at the conventional magnetic field strength of ± H ₂ shown by b in FIG. According to the present inventor's experiments, about 120 when a magnetic field strength ± H ₁ shown in FIG. 3 is a ± H ₂ and 100, ± H ₃
Is about 80, and it was confirmed that information could be recorded / reproduced without any problem if ± H ₃ was a ratio of about 80. As described above, since the current supplied to the magnetic head can be equal to or less than that of the conventional magnetic head on average, it is not necessary to increase the current of the magnetic head even if the inductance of the magnetic head is reduced. Power consumption can be suppressed.

FIG. 7 is a diagram showing the relationship between the magnetic field strength and the C / N ratio of the reproduced signal when information recorded by the magnetic field shown in FIG. 4 is reproduced. 7, when recording information in the magnetic field strength of ± H ₁ shown in FIG. 4, the reproduction signal C
The / N ratio is CN ₁ , and even if the magnetic field strength is further increased, C
The / N ratio hardly changes and is in a saturated state. In order to ensure the reliability of the reproduced signal, the C / N ratio is specified to be CN ₀ or more. The C / N ratio when recorded at a magnetic field strength of ± H ₂ is CN ₂ , and the C / N ratio at a magnetic field strength of ± H ₃ is C / N.
N ratio was CN _3. With this ± H ₃ field strength, C
The / N ratio was lower than the specified value of CN ₀ . Therefore, measurement of the C / N ratio of the reproduced signal to record information in the magnetic field strength shown in FIG. 3, the resulting value is the level of CN ₂ shown in FIG. 7, the ± H ₂ field strength The results were the same as those recorded with. Therefore, the same result as when the jitter amount was measured was obtained, and it was found that the evaluation of the reproduced signal may be either the jitter amount or the C / N ratio.

Therefore, based on the above concept,
An embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing one embodiment of the magnetic head device of the present invention. In FIG.
V1 is a 5V DC power supply, for example, and V2 is a 12V DC power supply having a higher voltage, for example. This DC power supply V1
Is connected to the switch element SW1 via a resistor R3 and a rectifying element D3 such as a diode, and is connected to the switch element SW2 via a resistor R4 and a rectifying element D4. These resistors R3, rectifier D3 and resistor R4
As the circuit of the rectifier element D4 is the detail impedance changes upon switching of the switch elements SW1, SW2 as described later, serves to supply a momentarily high current to the main coil L _H when the magnetic field reversal of a magnetic head It is. Also, L
_H is a main coil of a magnetic head wound around a magnetic core (not shown), L ₁ and L ₂ are auxiliary coils, and SW ₁ and SW ₂ are switching elements such as field effect transistors which are turned on and off alternately. The inductance of each auxiliary coil is set to be sufficiently larger than that of the main coil.

Next, the operation of this embodiment will be described. First,
When the switch element SW1 is turned on and the switch SW2 is turned off, the path from the DC power supply V1 to the current paths CH1 and CH5, the path from the DC power supply V1 to the current path CH2, and the main coil L
_H , the path to the current path CH5, and the DC power supply V
2 to the current paths CH3 and CH5, the DC power supply V
2 from the current path CH4, a state where the path to the current path CH5 was respectively conducted through the main coil L _H. At this time, the current flowing through the current path CH1, CH2 and I _1, the current flowing through the current path CH3, CH4 and I _2. In this state, when the switch element SW1 is turned off and SW2 is turned on, the current path CH5 is cut off and the current path CH5 is turned off.
6 conducts. At this time, since the inductances of the auxiliary coils L ₁ and L ₂ are large, the currents of the current paths CH 3 and CH 4 maintain almost constant currents, but are instantaneously induced between the auxiliary coil L ₁ and the main coil L _H. Due to the high voltage, the rectifying element D3 is in a reverse-biased state, and the current path CH
1 is temporarily cut off and becomes high impedance.

Meanwhile, the current flowing through the current path CH3, flow path at substantially a very short time while maintaining a constant value I ₂ is changed from the current path CH5 to the main coil L _H. Also, the main coil L _H is originally ＬLI ² (I = I ₁ + I
Since the magnetic energy of ₂₎ is stored, the vibration phenomenon of current occurs due to such capacity inductance and a switching element of the main coil L _H. In this case, as shown in FIG. 2, the current flowing in the reverse direction of the main coil L _H reaches a maximum when a half of the period of the current oscillation has elapsed,
Its value is I ₁ + I ₂ -ΔI. ΔI is 1 /
The amount of decrease in current due to energy loss at two cycles, which is about 20% of I ₁ + I ₂ . Then, on the one hand to a constant current I ₂ is supplied instantaneously to the main coil L _H from the current path CH3, current flowing through the main coil L _H at this point and I ₁ + 2I ₂ -.DELTA.I as shown in FIG. 2 Become. Here, if it is set so that I ₂ > ΔI,
The current flowing through the main coil L _H becomes larger than I ₁ + I ₂ . Since this current is set to a current value corresponding to the field strength of + H ₁ shown in FIG. 3, the current instantaneously I ₁ + 2I ₂ -ΔI is supplied when the current of the magnetic head is inverted In addition, the magnetic head is instantaneously +
A high magnetic field of H _1.

Thereafter, when the current of the main coil L _H reaches a maximum value, the voltage induced between the auxiliary coil L ₁ and the main coil L _H decreases, and the reverse bias of the rectifying element D 1 is released. You. Thus, the temporarily closed current path CH
Since 1 is turned on and changes from high impedance to low impedance, the oscillation phenomenon of the current flowing through the main coil L _H does not continue thereafter, but gradually decreases to I ₁ + I ₂ . Therefore, the current paths CH1 to I ₁ , CH3 to I ₂ ,
At the same time, the current of I ₁ + I ₂ is subsequently supplied to the main coil L _H, and the reversal of the current ends. This current of I ₁ + I ₂ is of course set to a current value corresponding to the magnetic field strength of + H ₃ shown in FIG. 3, and the magnetic field in the steady state has a low magnetic field strength.
Also, contrary to the above, the switch element SW2 is turned off, and SW
1 turns on, the current path CH2 changes from high impedance to low impedance in the same manner, so that when the current of the magnetic head rises to the negative side as shown in FIG. 2,-(I ₁ + 2I ₂ −ΔI) is supplied, and then gradually decreases to − (I ₁ + I ₂ ). Also at this time, the current value is set so that-(I ₁ + 2I ₂ -ΔI) corresponds to the magnetic field strength of -H ₁ in FIG. 3 and-(I ₁ + I ₂ ) corresponds to the magnetic field strength of -H ₃ , respectively. when the magnetic field is inverted to the negative polarity generates a momentarily high magnetic field -H ₁ as shown in FIG. 3, then generates a low magnetic field -H _3.

As described above, in the present embodiment, a high current is supplied instantaneously at the time of reversal of the current of the magnetic head, and a high magnetic field sufficient to perform recording instantaneously is generated. Even when the magnetic field in the steady state is a magnetic field strength that is insufficient for recording, the jitter amount and the C / N ratio of the reproduced signal are not deteriorated, and the information can be recorded and reproduced satisfactorily. Therefore, the magnetic field intensity in a steady state after an instantaneous high magnetic field may be low, so that the average current of the magnetic head can be reduced as compared with the related art, and the power consumption of the drive device can be reduced. Here, when recording information, a high-speed magnetic field reversal is required, and for that purpose, the inductance of the magnetic head must be reduced. However, when the inductance is reduced, the current efficiency is reduced, so that a sufficient magnetic field strength is obtained. Requires increasing the supply current. In this regard,
In this embodiment, since the information can be sufficiently recorded even when the supply current is small, if the average supply current of the magnetic head is equal to the conventional one, the magnetic inductance can be further reduced while the power consumption is the same. It is. This makes it possible to further increase the reversal speed of the magnetic field by reducing the inductance of the magnetic head, and has the effect that information can be recorded at a higher speed.

In the above embodiment, as shown in FIG. 3, a high-intensity magnetic field is instantaneously generated immediately after the magnetic field of the magnetic head rises from negative to positive and from positive to negative. A magnetic field as shown in FIG. 8 may be used. That is, FIG.
It may be the magnetic field of the magnetic head in opposition from positive to negative, instantaneously generating a magnetic field ± H ₁ of high strength immediately before reversal from negative to positive with. Also in this case, since a high magnetic field is applied at the time of forming the edge of the information pit, the information recording / reproducing is performed satisfactorily without the jitter amount and the C / N ratio of the reproduced signal being deteriorated as in the above embodiment. be able to. In the embodiment, an example is shown in which a large current is instantaneously supplied at the time of reversal of the current of the magnetic head using the impedance change of the path of the rectifying element due to the voltage induced between the auxiliary coil and the main coil. The present invention is not limited to this, and it goes without saying that there are various means such as providing a dedicated means for instantaneously supplying a large current to the magnetic head when the current is reversed.

Next, a reference of the magnetic head driving device of the present invention will be described.
An example will be described with reference to FIG. In FIG. 9, components having the same functions as those of the conventional device shown in FIG. 22 are denoted by the same reference numerals, and a detailed description thereof will be omitted. FIG.
In the figure, 10 is a current detector connected in series to the magnetic head 7, 11 is a differential amplifier, and 12 is a detection circuit for rectifying the output signal of the differential amplifier 11. Reference numeral 13 denotes a reference voltage generation circuit for generating a predetermined reference voltage;
Reference numeral 4 denotes an error amplifier for outputting an error signal between the output voltage of the detection circuit 12 and the reference voltage of the reference voltage generation circuit 13. Further, a field effect transistor is used as the switch elements T ₁ and T ₂ , and a control type which can change a gate drive voltage according to a control signal of the error amplifier 14 is used as the gate drive circuits 8 and 9. I have.

Next, the operation will be described. First, at the time of recording information, digitized information signals S ₁ and S ₂ are input to the gate drive circuits 8 and 9. The information signals S ₁ and S ₂
Are signals whose phases are inverted as described above. The gate drive circuits 8 and 9 generate drive signals having the same phase as the input information signals and apply the generated drive signals to the gates of the switch elements T ₁ and T ₂ , respectively. As a result, the switching elements T ₁ and T ₂ are turned on alternately, and an alternating current is supplied to the magnetic head 7.
At this time, the current of the magnetic head 7 is detected by the current detector 10 and output to the differential amplifier 11. Here, the current detector 10 includes a resistor R as shown in FIG. 10A, and the current of the magnetic head 7 is output as a voltage signal as a voltage drop of the resistor R. The terminals P _{1 to} P shown in FIG.
₄ corresponds to that of FIG. 10, and the detection signal of the current detector 10 is output to the differential amplifier 11 from the terminals P ₃ and P ₄ . Further, as the resistor R, it is preferable to use a resistor having a small temperature coefficient in order to increase current detection accuracy. After the signal thus detected is differentially amplified by the differential amplifier 11,
The DC voltage signal rectified by the detection circuit 12 and corresponding to the current of the magnetic head 7 is generated. The obtained DC voltage signal is output to the error amplifier 14, and is compared with the reference voltage of the reference voltage generation circuit 13 to output the error signal.

Since the reference voltage of the reference voltage generating circuit 13 is set in advance so as to correspond to the target current value of the magnetic head 7, the difference between the reference voltage and the output voltage of the detection circuit 12 is actually Is a voltage signal corresponding to the error of the target current of the magnetic head 7. The output signal of the error amplifier 14 is output to the gate drive circuits 8 and 9, and the drive voltage of the switching elements T ₁ and T ₂ is controlled according to the output signal of the error amplifier 14. That is, the output voltages of the gate drive circuits 8 and 9 increase and decrease according to the output signal of the error amplifier 14, and the drive voltages of the switch elements T ₁ and T ₂ are adjusted. For example, if the current of the magnetic head 7 decreases below the target value for some reason, the error amplifier 14 controls the current of the magnetic head 7 based on the detection result of the current detector 10 and the reference voltage so as to compensate for the shortage of the current of the magnetic head 7 with respect to the target value. The signal is output to the gate drive circuits 8 and 9. Accordingly, the driving voltage increases in response to the shortage in the gate driving circuit 8 and 9, since the element resistance value of the switch element T _1, T ₂ is reduced, correspondingly switching element T _1, T ₂
Of the magnetic head 7 is maintained at the target value. Conversely, when the current of the magnetic head 7 increases, the error amplifier 14 outputs a control signal to reduce the increase with respect to the target value, and the gate drive circuits 8 and 9 decrease the gate drive voltage accordingly. As a result, the element resistances of the switching elements T ₁ and T ₂ increase, so that the current of the magnetic head 7 decreases and is maintained at the target value.

As described above, in this embodiment , the current of the magnetic head is detected, and the feedback control is performed based on the detection result. Irrespective of this, the current of the magnetic head can always be kept constant. Therefore, it is possible to always record information under constant conditions, without the magnetic field strength of the magnetic head fluctuating or being different for each device.

[0027] FIG. 11 is a circuit diagram showing another reference example of the present invention. In this reference example , the switching elements T ₁ and T ₂
Field effect transistors T ₃ and T ₄ for controlling current in series with
Is newly provided to control the current of the magnetic head to be constant. That is, the switching elements T ₁ and T ₂ are simply turned on,
Performs only switching operation off, the field effect transistor T _3, T ₄ is intended that controls the element resistance had been kept connected. Therefore, here, similarly to the embodiment of FIG. 9, the element resistance of the field effect transistors T ₃ and T ₄ is reduced by the current control circuit including the current detector 10, the differential amplifier 11, the detection circuit 12, the error amplifier 14, and the like. As a result, the current of the magnetic head is constantly controlled to be constant. Thus, also the reference of FIG. 9 in the present embodiment
As in the example , the current of the magnetic head can be controlled to be constant irrespective of power supply fluctuations, and the magnetic field generated by the magnetic head can be maintained at a constant value.

In the reference example , a resistor is shown as the current detector 10. However, the present invention is not limited to this, and a transformer TS may be used as shown in FIG. In this case, since the power loss is smaller than that of the resistor, the power consumption of the driving device does not increase due to the current detection. In addition, participants
Although the current example shows an example in which the current detector is connected in series with the magnetic head, a current path on the power supply side or a current path on the ground side, which is a current path of the magnetic head, may be used.

Next, still another embodiment of the magnetic head device of the present invention will be described.
A reference example will be described. First, a book based on FIG.
A schematic configuration of a magneto-optical recording device of a magnetic field modulation system using a magnetic head device of a reference example will be described. In FIG. 12, 2
0 is a magneto-optical disk as an information recording medium, 21
Denotes a magneto-optical recording layer provided on the magneto-optical disk 20. The magneto-optical disk 20 rotates at a constant speed by driving a spindle motor (not shown). Reference numeral 22 denotes a magnetic head for generating a magnetic field modulated in accordance with an information signal;
Reference numeral 3 denotes a magnetic head drive circuit for driving the magnetic head 22, and reference numeral 24 denotes a magnetic head abnormality detection circuit for detecting a reversal time of a magnetic field generated by the magnetic head 22. That is,
When information is recorded on the magneto-optical disk 20, information pits having a magnetization direction corresponding to the information signal are recorded. The quality of the information pits, particularly, noise components at the edges of the information pits depend on the magnetic field generated by the magnetic head 22. Inversion speed (switching time). Therefore, accurate information pits cannot be recorded unless the switching time of the magnetic head is within the time determined by the size of the information pits and the number of rotations of the magneto-optical disk 20. Therefore, the magnetic head abnormality detection circuit 24 monitors the switching time of the magnetic field of the magnetic head 22 and detects an operation abnormality of the magnetic head 22 when the switching time deviates from a predetermined reference time, and does not show an abnormality detection signal. Output to the control unit.

Reference numeral 25 denotes a semiconductor laser provided as a recording / reproducing light source, and reference numeral 26 denotes a laser drive circuit for driving the semiconductor laser 25. Laser drive circuit 26
Turns on the semiconductor laser 25 at a predetermined constant recording power during information recording, and turns on the semiconductor laser 25 at a constant reproducing power lower than the recording power during information reproduction. Reference numeral 27 denotes a collimator lens for collimating the laser beam of the semiconductor laser 25, and reference numeral 28 condenses the collimated laser beam to form a minute light spot on the magneto-optical recording layer 21 of the magneto-optical disk 20. Objective lens. The objective lens 28 is arranged to face the magnetic head 22 with the magneto-optical disk 20 interposed therebetween. The objective lens 25, the collimator lens 27, and the semiconductor laser 25 are integrated as an optical head, and are configured to be movable in the radial direction of the magneto-optical disk 20.

FIG. 13 shows a specific example of the optical head drive circuit 23, in which a bridge type drive circuit is used. 13, SW1 to SW4 are switch elements such as field effect transistors, and 29 is a drive coil of the magnetic head 22. In this drive circuit, for example, when the information signal is "1", the switch elements SW1 and SW4
Is turned on, the switch elements SW2 and SW3 are turned off, and current is supplied to the coil 29 in the direction of arrow A in the figure. When the information signal becomes "0", the switch elements SW1 and SW4
Is turned off, the switch elements SW2 and SW3 are turned on, and a current is supplied to the drive coil 29 in the direction of arrow B. That is,
Switch elements SW1, SW4 and switch elements SW2, S
By controlling W3 according to the information signal, the current direction of the drive coil 29 is switched according to the information signal, and the polarity of the generated magnetic field is switched.

FIG. 14 is a diagram showing a configuration around the magnetic head abnormality detection circuit 24. As shown in FIG. In FIG. 14, reference numeral 30 denotes a magnetic core made of a magnetic material of the magnetic head 22, and 29 denotes a drive coil wound around the magnetic core 30 as described above. The drive coil 29 is driven by the magnetic head drive circuit 23 as described above, and as a result, the magnetic head 2
2 generates a magnetic field modulated according to the information signal. A ring-shaped detection core 31 is inserted into a wiring connecting the drive coil 29 and the magnetic head drive circuit 23, and the detection core 31 is wound with a plurality of detection coils 32 as a secondary winding. The detection coil 32 is connected to the magnetic head abnormality detection circuit 24, and the abnormality detection circuit 24 detects an abnormality in the switching time of the generated magnetic field by monitoring the current of the magnetic head. This detection method is generally called a current transformer method. The detection core 31 is made of a soft magnetic material.

FIG. 15 shows the magnetic head abnormality detecting circuit 24.
FIG. 3 is a circuit diagram showing a specific example of the embodiment. In FIG. 15, 33
Is a differentiation circuit for differentiating the current signal of the drive coil 29 of the magnetic head 22 detected by the detection core 31. The differentiating circuit 33 differentiates the current signal of the coil of the magnetic head to output a signal proportional to the rate of change when the coil current changes from positive to negative or from negative to positive. That is, a signal proportional to the switching time of the coil current is output. 34 to 37 are comparators for comparing the output signal of the differentiating circuit 33 with a predetermined reference voltage, and 38 is an OR circuit for ORing the output signals of these comparators. Here, the reference voltage ± V _th1 of the comparators 34 and 35 is a voltage corresponding to the reference speed of the switching time of the magnetic field generated in the magnetic head 22. If the reference voltage is lower than this reference voltage, normal recording cannot be performed. is there. Although the comparators 36 and 37 will be described in detail later, for example, when the switching time becomes shorter than usual even if an abnormality occurs, for example, when the coil 29 of the magnetic head 22 is partially short-circuited, the reference voltage ± V _th2 Is to detect an abnormality that cannot be detected by the comparators 34 and 35 described above.

Next, the operation of the magnetic head abnormality detecting circuit 24 will be described with reference to FIGS. 16A and 16B show the operation when the magnetic head 22 is normal. FIG. 16A shows the current of the drive coil 29 of the magnetic head 22, and FIG. 16B shows the output signal of the differentiating circuit 33. It is. The alternating current supplied to the drive coil 29 of the magnetic head 22 is ± _IM , and here shows the drive current when recording information pits of about 0.8 μm at a duty of 50%. In this case, assuming that the linear velocity of the magneto-optical disk 20 is about 8 m / s, the current switching time of the coil 29 must be about 15 ns or less. The driving current of the coil 29 is the same as that of the detection core 31 described above.
The current is detected by the current transformer constituted by the detection coil 32 and output to the differentiating circuit 33. The differentiating circuit 33 differentiates the input signal and outputs a signal as shown in FIG. The obtained differential signal becomes a signal proportional to the rate of change of the coil current. When the coil current changes from negative to positive, it becomes a positive pulse signal, and when the coil current changes from positive to negative, it becomes a negative pulse signal. . That is, the output signal of the differentiating circuit 33 changes in proportion to the switching time of the coil current, and when the switching time of the coil current is delayed, the level of the differentiated output decreases in proportion to this. If switching time of current of the drive coil 29 is normal, the level of the peak value of the output signal of the differentiation circuit 33 becomes ± V _d. Further, ± V _th1 shown in FIG. 16B is a voltage corresponding to the above-mentioned prescribed value of the switching time of 15 ns, which is input to the comparators 34 and 35 as a reference voltage.

Here, it is assumed that some abnormality occurs in the magnetic head 22 and the switching time of the coil current is delayed. That is, as shown in FIG.
If only the switching time is delayed with _M
The level of the peak value of the output signal of the differentiating circuit 33 decreases as shown in FIG. The output signal of the differentiating circuit 33 is output to the comparators 34 and 35. Since the output level of the differentiating circuit 33 is lower than ± V _th1 , the comparators 34 and 35 output signals indicating abnormalities, respectively. . These abnormality detection signals are output to a control unit (not shown) via the OR circuit 38, and the control unit that receives the signals detects the abnormality by performing control such as interrupting the recording operation. In this embodiment , since the comparators 34 and 35 are provided independently to compare the reference voltage of ± V _th1 with the output of the differentiating circuit 33, one of the switching times when the coil current rises or falls is abnormal. Can be detected even if the error occurs. When the drive coil 29 is disconnected,
Since the level of the output signal of the differentiating circuit 33 becomes 0, disconnection can be detected.

On the other hand, as shown in FIG.
When the drive coil 29 is short-circuited to X and Y, the inductance and the DC resistance of the magnetic head 22 decrease, so that the switching time of the coil current becomes faster than in the normal state.
FIG. 19A shows the coil current when such a situation occurs. The switching time is shorter than that in the normal state (FIG. 16A) due to the decrease in the inductance and the DC resistance. This is because the switching time of the current of the magnetic head 22 depends on the time constant of its inductance and DC resistance. FIG. 19B shows the differentiating circuit 3.
A diagram showing a third output signal, the switching time is faster than the normal, higher than the output voltage ± V _d at the output level of course normal. The abnormality that the switching time of the coil current is shortened in this manner is caused by the comparators 36 and 37.
Is detected by That is, since the reference voltage ± V _th2 higher than the normal output voltage ± V _d is input to the comparators 36 and 37, the switching speed of the coil current increases, and the output voltage of the differentiating circuit 33 becomes ± V _th2. Is exceeded, the comparator 3
An abnormality detection signal is output from 6, 37 to the control unit via the OR circuit 38. Therefore, the control unit performs a countermeasure against the abnormality of the magnetic head 22 such as the interruption of the recording operation as described above.

As described above, in the present embodiment , the reversal speed of the magnetic field of the magnetic head is indirectly detected by monitoring the coil current of the magnetic head. Is output, recording errors due to abnormal magnetic fields generated by the magnetic head can be prevented beforehand, and information can be recorded with high reliability. That is, if the switching time of the generated magnetic field becomes slower than the reference value, a recording error occurs due to an increase in the jitter amount of the reproduction signal. In this embodiment , the occurrence of the recording error is detected by detecting such a decrease in the switching speed. It can be prevented beforehand. Also, if the switching time of the magnetic field is shortened due to a partial short circuit of the magnetic head,
While recording error due to the lack of the magnetic field strength due to a reduction in the inductance of the magnetic head will occur, this reference
In the example , the occurrence of a recording error can be prevented beforehand by detecting such an abnormality.

In the reference example , the coil current of the magnetic head is detected using a ring-shaped detection core, but there are various other detection means. For example, the coil current can also be detected by directly winding the detection coil 39 around the magnetic core 30 of the magnetic head 22 as shown in FIG. Further, although the abnormality of the magnetic field generated by the magnetic head is indirectly detected by the coil current, the abnormality can be directly detected by providing an electric field detecting element near the magnetic head.

[0039]

As described above, according to the present invention, the current for generating a magnetic field sufficient for instantaneously recording information is supplied immediately or immediately before the current of the magnetic head is reversed. Even if the normal current is insufficient for recording information, information can be recorded well. Therefore, the power consumption can be reduced because the current of the magnetic head is small, and if the power consumption is equivalent to the conventional one, the inductance of the magnetic head can be reduced correspondingly, and the reversal time of the generated magnetic field can be shortened. This has the effect of realizing high-speed recording of information.

[0040]

[0041]

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram showing a current of the magnetic head of the embodiment of FIG.

FIG. 3 is a diagram showing a generated magnetic field of a magnetic head according to the present invention.

FIG. 4 is a diagram showing an applied magnetic field of a general magneto-optical recording device in which the magnetic field strength is changed stepwise.

FIG. 5 is a diagram showing the relationship between the magnetic field intensity and the amount of jitter of a reproduced signal when information recorded with the magnetic field intensity of FIG. 4 is reproduced.

FIG. 6 is a diagram showing a definition of a jitter amount of a reproduction signal.

7 is a diagram showing the relationship between the magnetic field intensity and the C / N ratio of a reproduced signal when information recorded with the magnetic field intensity of FIG. 4 is reproduced.

FIG. 8 is a diagram showing another example of the magnetic field generated by the magnetic head according to the present invention.

FIG. 9 is a circuit diagram showing a reference example of the magnetic head device of the present invention.

FIG. 10 is a diagram showing a specific example of a current detector used in the reference example of FIG. 9;

FIG. 11 is a circuit diagram showing a modification of the reference example of FIG. 9;

FIG. 12 is a diagram showing a configuration example of a magneto-optical recording device using the magnetic head device of the present invention.

FIG. 13 is a diagram showing details of a magnetic head drive circuit used in the magneto-optical recording device of FIG.

FIG. 14 is a diagram showing a detection unit for detecting a coil current of the magnetic head of FIG.

15 is a diagram showing the magnetic head abnormality detection circuit of FIG. 12 in detail.

16 is a diagram showing an operation of the magnetic head abnormality detection circuit of FIG. 15 when a magnetic field reversal time is normal.

FIG. 17 is a diagram showing an operation of the magnetic head abnormality detection circuit of FIG. 15 when the magnetic field reversal time is later than normal.

FIG. 18 is a diagram showing a state where a part of a coil of the magnetic head is short-circuited.

FIG. 19 is a diagram showing an operation of the magnetic head abnormality detection circuit of FIG. 15 when the magnetic field reversal time is shorter than normal.

FIG. 20 is a diagram showing another example of current detection of a magnetic head.

FIG. 21 is a diagram illustrating a schematic configuration of a general magnetic field modulation type magneto-optical recording device.

FIG. 22 is a diagram showing a conventional magnetic head drive device.

[Explanation of symbols]

SW1~SW4 switching element L _H main coil T ₁ through T ₄ switch elements 7, 22 magnetic head 8,9 gate drive circuit 10 a current detector 12 detecting circuit 14 the error amplifier 20 the magneto-optical disc 23 a magnetic head drive circuit 24 a magnetic head abnormality Detection circuit 29 Drive coil 30 Magnetic core 31 Detection core 33 Differentiator 34-37 Comparator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-113402 (JP, A) JP-A-62-111103 (JP, A) JP-A-3-178009 (JP, A) 77410 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 5/02 G11B 5/09 311

Claims (2)

(57) [Claims] 1. A magnetic head device for alternately switching the direction of a current supplied to a main coil of a magnetic head according to an information signal, wherein the magnetic head device includes a first current path (C).
H1), a second current path (CH3) including an auxiliary coil,
When the current supplied to the main coil is switched, first, the switching element switches the main coil to generate a current oscillation phenomenon and the second current path (CH3) supplying a current I ₂ to the main coil, the oscillation phenomenon of the current after a current supplied to said main coil has reached a maximum, the first current path (CH1) than the current I ₁ and the second the current I ₂ from the current path (CH3) and supplies to the main coil, [Delta] I further decrease in current corresponding to the energy loss at the time the current supplied to said main coil has reached a maximum by the vibration phenomenon of the current When I ₂ > ΔI, the current supplied to the main coil is instantaneously set to I ₁ +
A magnetic head device characterized by being larger than I ₂ and thereafter I ₁ + I ₂ . 2. The first current path (CH1) is a rectifier element.
Rectifier by switching the switch element
When the element is in a reverse bias state, the first current
The path (CH1) is cut off and the second current path (CH
3) The current I ₂ is supplied to the main coil from
After the current supplied to the main coil reaches a maximum,
When the reverse bias of the rectifying element is released, the
First current path (CH1) is conducting, the current I ₁ + I ₂ is pre
Claims characterized by flowing through the main coil.
2. The magnetic head device according to 1.