JPH07161005A - Field coil driving circuit - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording device equipped with a driving circuit for driving a field coil capable of inverting a magnetic field at high speed with only a low power source voltage required. CONSTITUTION:The field coil 10 is constituted to be a parallel resonance circuit, and by driving this field coil 10 alternately via current passages with a positive direction current and a negative direction current, a strong magnetic field is obtained by a low power source voltage. For example, the positive direction current flows in a passage of a switch 12a, a diode 13a, the field coil 10, a diode 17 and a switch 16, and the negative direction current flows in a passage of a switch 12, a diode 13, the field coil 10, a diode 17a and a switch 16a. Then, the strong magnetic field can be inverted at high speed by providing a booster coil 30 between a positive potential and the field coil driving circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording device and a drive circuit for driving a field coil used in such a magneto-optical recording device.

[0002]

2. Description of the Related Art Conventionally, when recording on a magneto-optical recording medium,
The following is done: That is, the magneto-optical material is magnetized in a specific direction prior to recording, and then, at the time of recording, the magneto-optical material is exposed to a magnetic field in the direction opposite to the magnetization direction previously given, and at the same time, a laser beam whose intensity is modulated. Is used to locally heat the material to a temperature near the Curie point, thereby generating a pattern of a magnetic region that corresponds to the modulation pattern and has a magnetization direction different from that of the surrounding region. Was there.

However, the above-mentioned method has a drawback in that a portion which has already been recorded must be erased in advance when newly recording.

Therefore, instead of the laser beam, a method in which the magnetic field is modulated is used. This is to generate the pattern of the magnetic region by heating the magneto-optical material to a temperature near the Curie point with a constant intensity laser beam and changing the magnetization direction according to the modulation pattern by the magnetically modulated field coil. To do.

[0005]

However, since the magnetic field generated in the field coil is strong, the energy stored in the magnetic field is high and it is necessary to generate a large voltage difference in the field coil. Moreover, it is necessary to reverse the strong magnetic field generated in the field coil at high speed. Theoretically, the above large voltage difference can be realized by a high voltage output voltage source. However, in the conventional magneto-optical recording apparatus, electronic circuits other than the magnetic field modulation operate at a low power supply voltage, which means that the magnetic field modulation must use another power supply voltage. Further, since the magnetic field generated in the field coil is strong, it is difficult to reverse at high speed.

It is an object of the present invention to provide a magneto-optical recording device which requires a low power supply voltage and is provided with a drive circuit for driving a field coil capable of reversing a magnetic field at high speed.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the object is to provide a field coil as a parallel resonant circuit, and a drive circuit controlled by a control circuit to alternate first and second current paths. The switch for driving the field coil alternately with the positive direction current and the negative direction current through these current paths and the third and fourth voltage paths controlled by the control circuit are formed alternately. As a result, a switch for alternately driving the first and second current paths with positive and negative voltages through these voltage paths and one of the current paths are cut off, and then the resonance cycle of the resonance circuit is reached. A current inhibiting means configured to inhibit current supply via the other of the current paths to the field coil for a period corresponding to half of the current Ri has been achieved.

Further, the present invention has been achieved by having a boosting coil provided between the power supply voltage supply terminal and the field coil driving circuit.

[0009]

In this case, since the field coil is constructed as a resonance circuit, resonance occurs in the resonance circuit after one current path is cut off. Thus, the current flowing through the field coil is sinusoidal and then the current direction is reversed. After half the resonance period, this current reaches a limit value whose absolute value is equal to the absolute value of the current value at the time of interruption and whose polarity is opposite to that of this interruption current. When this limit value is reached, the current in the field coil can be maintained at the limit value by driving the field coil in another current path. Then, in order to maintain this current, it suffices to compensate for the voltage drop due to the resistance value of the field coil, so that the voltage between both ends of this coil may be several volts. Thus, it becomes possible to use the low power supply voltage already required for the electronic circuits of other parts as the power supply voltage for this field coil drive circuit.

Further, current is always stored in the boosting coil, and when one of the current paths is cut off and then the other current path is connected, the current is instantly stored in the boosting coil. The current that was being applied flows into the field coil,
The magnetic field can be reversed at high speed.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. The components having the same configurations and operations as those in the other embodiments are designated by the same reference numerals.

FIG. 1 shows an embodiment of a magneto-optical recording apparatus 1. In this figure, the recording medium 4 is adapted to be rotated by a driving means having a turntable 2 and a motor 3. The recording medium 4 is provided with a recording layer 5 made of a usual magneto-optical material. Further, the optical head 6 directs a radiation beam 7 such as a laser beam to the recording layer 5. In this way
The magneto-optical material is heated to a temperature near the Curie point. Also, the heated portion of the magneto-optical material is exposed by the magnetic field modulator 8 to a magnetic field of sufficient intensity to magnetize the heated portion in a direction depending on the direction of the magnetic field. The recorded magnetization is retained even after cooling. The magnetic field modulator 8 modulates the magnetic field according to the control signal Vs extracted from the information signal Vi by an encoding circuit 9 such as an EFM encoder. Thus, the information signal V
A magnetic region pattern representing i is formed in the recording layer 5.

Next, FIG. 2 shows a magnetic field modulator 8 including an embodiment of a drive circuit for a field coil according to the present invention. In this figure, the boosting coil 30 is provided between the terminal 11 of the positive potential Vp and the positive power supply terminal 31 of the field coil drive circuit. A series connection of an electronic switch 12 and a current prohibiting rectifying element (hereinafter referred to as a diode) 13 is provided between the positive power supply terminal 31 and the node 14, and
A series connection of the electronic switch 16 and the diode 17 is similar to the first branch provided between the ground potential 15 and the node 14 and is similar to the first branch, the electronic switch 12a and the diode 13a. A series connection with and is provided between the positive power supply terminal 31 and the node 18, and a series connection with the electronic switch 16a and the diode 17a is provided between the ground terminal 15 and the node 18. Node 14
The node 18 is connected to the field coil 10 for generating a magnetic field. The capacitor 19 is connected in parallel to the field coil 10 to form a parallel resonance circuit.

The control circuit 20 creates control signals for the electronic switches 12 and 16 from the control signal Vs. The electronic switches 12a and 16a are also controlled by the control circuit 20a similar to the control circuit 20 in the same manner as above. Electronic switch 1
The control signals 2a and 16a are generated from -Vs, and this control signal is generated from the control signal Vs by the inverter circuit 21. According to the theoretical value of the control signal Vs, these electronic switches are configured such that when two opposing switches on the diagonal side are closed, the other two switches are opened. For example, electronic switch 12 and electronic switch 1
When 6a is closed, the electronic switch 12a and the switch 16 are open. Thus, the field coil 10
The voltage across both ends of V depends on the theoretical value of the control signal Vs.

Here, the operation of the magnetic field modulator 8 having the above configuration is shown in FIG. At time t0, the magnetic field modulator 8 is in a stable state when the theoretical value of the control signal Vs is "1". That is, the electronic switches 12a and 16 are closed and the electronic switches 12 and 16a are open. In this case, the voltage across the field coil 10 is equal to the potential difference between the positive power supply terminal 11 and the ground terminal 15. The current Im flowing through the field coil 10 depends on the resistance value of the field coil 10. Usually, this resistance value is about 1Ω, and even if the desired current intensity is several A, the required potential difference may be a value as low as several V.

Next, at time t1, the magnetic field modulator 8
Is in the state of change of the control signal Vs from "1" to "0".
That is, the electronic switches 12a and 16 are changed to the open state, and the electronic switches 12 and 16a are changed to the closed state, but the resonance circuit formed by the field coil 10 and the capacitor 19 is temporarily supplied with the positive power supply. It is cut off from the terminal 11. As a result, the resonance circuit causes the current Im and the voltage Vm.
A sine-change transient is caused. Field coil 1
Since 0 is configured as a resonance circuit, resonance occurs,
The current Im flowing through the field coil 10 reaches a limit value. At this time, the electronic switches 12 and 16a are closed, but the connection with the field coil 10 is prohibited by the diode 13 as a result of the high positive voltage induced in the field coil 10 and maintains its limit value. .

At time t2, the magnetic field modulator 8 is in a stable state when the theoretical value of the control signal Vs is "0", and is in a state corresponding to the state at time t0, and the diode 13 conducts. The absolute value of the current Im flowing through the magnetic coil 10 is equal to the absolute value of the current Im at the time t0, and its polarity is the time t1 of the current Im.
The opposite of the polarity in.

Next, FIG. 6 shows the difference in the current Im flowing through the field coil 10 depending on the presence or absence of the boosting coil 30 in the magnetic field modulator 8 having the above structure.

At time t1, the magnetic field modulator 8 is in a state of change of the control signal Vs from "1" to "0". That is, the electronic switches 12a and 16 are changed to the open state, and the electronic switches 12 and 16a are changed to the closed state, but the resonance circuit formed by the field coil 10 and the capacitor 19 is temporarily supplied with the positive power supply. It is cut off from the terminal 11. This causes a transient phenomenon of the sinusoidal change of the current Im and the voltage Vm in the resonant circuit. Since the field coil 10 is configured as a resonance circuit, resonance occurs, and the current Im flowing through the field coil 10 reaches a limit value. At this time, the current stored in the boosting coil 30 instantaneously flows into the field coil 10, and the current Im flowing through the field coil 10 reaches the limit value at high speed. This enables high-speed reversal of the magnetic field generated in the field coil 10.

Next, FIG. 3 shows a magnetic field modulator 8 including an embodiment of a field coil drive circuit in which the control circuit portion is simplified. A series connection of the electronic switch 12 and the diode 13 is provided between the positive power supply terminal 31 and the node 14, and a series connection of the electronic switch 16 and the diode 17 is provided between the ground potential 15 and the node 14. And the first branch which is similar to the first branch and which is connected in series with the electronic switch 12a and the diode 13a,
It is provided between the positive power supply terminal 31 and the node 18, and a series connection of the electronic switch 16a and the diode 17a is provided between the ground terminal 15 and the node 18. The control signal input terminal of the first branch electronic switch 12 is connected to the second branch electronic switch 16a, and the control signal input terminal of the second branch electronic switch 12a is the first branch electronic switch 12a. It is connected to the branch electronic switch 16. The node 14 and the node 18 are respectively connected to the field coil 10 for generating a magnetic field. The capacitor 19 is connected in parallel to the field coil 10,
It constitutes a parallel resonant circuit.

The control circuit 22 creates a control signal for the electronic switch 16 from the control signal Vs. Electronic switch 16a
Is also controlled in the same manner as above by a control circuit 23 similar to the control circuit 22. The control signal of the electronic switch 16a is -V.
and the control signal is generated from the inverter circuit 23.
Is generated from the control signal Vs. Moreover, since the control signal input terminal of the electronic switch 12 is connected to the electronic switch 16a, the electronic switch 12 is controlled in conjunction with the operation of the electronic switch 16a. Similarly, since the control signal input terminal of the electronic switch 12a is connected to the electronic switch 16, the electronic switch 12a is controlled in conjunction with the operation of the electronic switch 16. As a result, these electronic switches are configured such that when the two opposing switches on the diagonal side are closed, the other two switches are opened according to the theoretical value of the control signal Vs. For example, when the electronic switch 16 is closed, the electronic switch 12a is also interlocked, and similarly, when the electronic switch 16a is closed, the electronic switch 12 is also interlocked and closed. Thus, the voltage across the field coil 10 depends on the theoretical value of the control signal Vs. According to this, since the electronic switches controlled by the control signal are only 16 and 16a,
The control circuit can be easily constructed.

Next, FIG. 4 shows a magnetic field modulator 8 including an embodiment of a field coil drive circuit including a level conversion circuit and a voltage conversion circuit. Electronic switch 12 and diode 1
3 in series connection is provided between the positive power supply terminal 31 and the node 14, and an electronic switch 16 is provided between the ground potential 15 and the node 14 and a first branch Similar to the first branch, the electronic switch 12
A series connection of a and the diode 13a is provided between the positive power supply terminal 31 and the node 18, and an electronic switch 16a is provided between the ground terminal 15 and the node 18. The electronic switches 12 and 12a are p-channel field effect transistors, and the electronic switches 16 and 16a are n-channel field effect transistors. Nodes 14 and 18 are respectively connected to the field coil 10 for generating a magnetic field. Capacitor 19
Are connected in parallel to the field coil 10 to form a parallel resonance circuit. Further, a level converter 32 for converting the level of the control signal Vs and a voltage conversion circuit 33 for generating a positive voltage and a negative voltage which are the basis of the level conversion are included.

The control signal Vs is level-converted by the level converter 32 by the positive voltage and the negative voltage generated from the voltage conversion circuit 33. The control circuit 24 uses the control signal Vs ′ after the level conversion to switch the electronic switch 12,
Create 16 control signals. Electronic switches 12a, 16
a is also controlled in the same manner as above by a control circuit 25 similar to the control circuit 24. The control signal for the electronic switches 12a and 16a is generated from -Vs ', and this control signal is generated from the control signal Vs' by the inverter circuit 25. According to the theoretical value of the control signal Vs, these electronic switches are configured such that when two opposing switches on the diagonal side are closed, the other two switches are opened. For example, when the electronic switches 12 and 16a are closed, the electronic switches 12a and 16 are open. Thus, the voltage across the field coil 10 is equal to the control signal Vs
Depends on the theoretical value of.

Since the electronic switches 12 and 12a are composed of p-channel field effect transistors, a negative voltage control signal is required. Further, in the field effect transistor, it is possible to reduce the on-resistance by increasing the voltage difference between the gate and the source (hereinafter, referred to as Vgs). In other words, it is possible to obtain a high drain current by increasing Vgs. That is, this drain current flows to the field coil 10 via the diode 13 and the node 14 or the diode 13a and the node 18, so that a stronger magnetic field can be obtained. In short, the positive potential Vp
It is possible to obtain a stronger magnetic field without changing.

[0025]

According to the invention described above, the field coil is configured as a parallel resonance circuit, and the current paths of the two systems controlled by the control circuit are alternately formed. By alternately driving with a positive direction current and a negative direction current via the, there is an effect that a strong magnetic field can be obtained with a low power supply voltage.

Further, by providing the boosting coil between the positive potential and the field coil drive circuit, it is possible to reverse a strong magnetic field at high speed.

Further, by providing a field effect transistor as an electronic switch and converting the level of the control signal to increase the value of Vgs of the field effect transistor, it is possible to obtain a stronger magnetic field at a low power supply voltage. Has the effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a magneto-optical recording device according to the present invention.

FIG. 2 is a block diagram showing a magnetic field modulator including an embodiment of a drive circuit according to the present invention.

FIG. 3 is a waveform diagram showing waveforms of signals at various parts of the magnetic field modulator including the drive circuit according to the present invention.

FIG. 4 is a waveform diagram showing a waveform of a signal flowing in a field coil of a magnetic field modulator including a drive circuit according to the present invention.

FIG. 5 is a block diagram showing a magnetic field modulator including another embodiment of the driving circuit according to the present invention.

FIG. 6 is a block diagram showing a magnetic field modulator including still another embodiment of the driving circuit according to the present invention.

[Explanation of symbols]

 1 magneto-optical recording device 4 recording medium 8 magnetic field modulator 10 field coil 12, 16 switch 13, 17 diode 19 capacitor 20 control circuit 30 boosting coil 32 level converter 33 voltage converter

Claims (4)

[Claims] 1. A field coil for generating a magnetic field in a magneto-optical recording medium of a magneto-optical recording device for recording an information signal, a drive circuit for driving the field coil, and the magnetic field as the information. A control circuit that controls the drive circuit based on the information signal to modulate in accordance with a signal, wherein the field coil is configured as a parallel resonant circuit, and the drive circuit is controlled by the control circuit. By alternately forming the first and second current paths, the field coil is alternately driven by a positive direction current and a negative direction current through these current paths; After one is cut off, the current supply to the field coil is prohibited through the other of the current paths for a period corresponding to half of the resonance cycle of the resonance circuit. A field coil drive circuit comprising: a current prohibiting means. 2. The field coil drive circuit according to claim 1, wherein a boosting coil is provided between the drive circuit for driving the field coil and the power supply voltage supply terminal. 3. A first and a second current path are alternated by a positive voltage and a negative voltage through these voltage paths by being controlled by a control circuit to alternately form the third and fourth voltage paths. The field coil drive circuit according to claim 1 or 2, further comprising a switch for driving the field coil. 4. A field coil drive circuit according to claim 3, further comprising a voltage conversion circuit for converting a positive power supply voltage into a negative voltage as means for forming the third and fourth voltage paths. .