JPH0770004B2 - Bias magnetic field generator - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias magnetic field generator used for magneto-optical recording / reproduction used for external storage of electronic computers, recording / reproduction of music and video signals, and other information. is there.

2. Description of the Related Art In recent years, along with the development of electronic computers and the means of high-speed and large-volume transmission of information, low-cost, high-density, large-capacity, and high-speed transfer non-volatile storage devices are required, and magnetic disk devices are mostly used. However, there are problems that the recording density is low, the price per information unit is high, and that medium exchange is difficult especially in a fixed magnetic disk device. Optical recording is currently in the spotlight as a technique for solving these problems, and rewritable magneto-optical recording is expected in many fields.

In the conventional bias magnetic field generator, the electromagnet is driven by a single voltage source.

Hereinafter, the conventional bias magnetic field generator as described above will be described with reference to the drawings.

FIG. 8 shows a conventional bias magnetic field generator. In FIG. 8, 1 is an exciting coil, 2 is a magnetic core, and these are for recording and erasing information on a magneto-optical recording medium (not shown). An electromagnet that provides a bias magnetic field is configured. Reference numeral 3 denotes a control unit, which controls the timing and order of on / off operations of the switches 6 to 9 by a transistor or the like for driving the excitation coil 1 and switching the polarity of the output magnetic field according to an instruction from an input unit (not shown). Control via S _{1 to} S ₄ . Signal lines S ₁ , S ₂ , S ₃ ,
S ₄ has a one-to-one correspondence with switches 6, 9, 8 and 7, respectively, and when the voltage on the signal line exceeds a certain voltage V _H , the corresponding switch turns on, and at other voltages, the corresponding switch turns on. Turns off. Reference numeral 21 denotes a voltage source for applying a voltage to the exciting coil 1, which maintains a constant voltage V _S. 4 and 5 are excitation coils 1
Are a recording current source and an erasing current source that supply a current to the exciting coil 1 when performing a recording operation and an erasing operation.

The operation of the bias magnetic field generator configured as described above will be described below.

First, when the erase operation is performed, the control unit 3 raises the voltage of the signal lines S ₁ and S ₂ to V _H at time t ₁ as shown in FIG. Then, the switches 6 and 9 shown in FIG. 8 are turned on to close the circuit, and the current flows from the voltage source 21 through the switch 6, the exciting coil 1, the switch 9 and the erasing current source 5, and the exciting coil 1 and the magnetic core. The electromagnet constituted by 2 starts to give an erasing bias magnetic field to the magneto-optical recording medium. After waiting until the bias magnetic field has a size capable of performing the erasing operation, an optical head (not shown) gives an erasing light spot to the magneto-optical recording medium to execute the erasing operation. Control unit 3 and the erasing at time t ₂ to complete the dropping the voltage of the signal line S _1, S ₂ to 0V. Then switch
6, 9 are turned off, the circuit is opened, the current is cut off, and the electromagnet constituted by the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

When the recording operation is performed next, as shown in FIG.
Raises the voltage of signal lines S ₃ and S ₄ to V _H at time t ₃ . Then, the switches 8 and 7 shown in FIG. 8 are turned on to close the circuit, and the current flows from the voltage source 21 through the switch 8, the exciting coil 1, the switch 7 and the recording current source 4, and the exciting coil 1 and the magnetic core. The electromagnet composed of 2 starts to apply a recording bias magnetic field to a magneto-optical recording medium (not shown). After waiting until the bias magnetic field reaches a level at which the recording operation is possible, the optical head gives an optical spot according to the information to be recorded on the magneto-optical recording medium, and executes the recording operation. Control unit 3 records and becomes a time instant t ₄ to complete the dropping the voltage of the signal line S _3, S ₄ at 0V. Then the switches 8 and 7 are turned off, the circuit opens and the current is cut off,
The electromagnet composed of the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

Problems to be Solved by the Invention However, the above-described configuration has the following problems.

That is, the length of the waiting time until the bias magnetic field output by the electromagnet composed of the exciting coil 1 and the magnetic core 2 rises to a size capable of recording or erasing, that is, the length of the magnetic field rising time is determined by the voltage source 21. It is almost inversely proportional to the voltage V _S.
Normally, magneto-optical recording does not perform overwriting, so when recording information, it is performed after erasing the corresponding area on the medium as shown in the information example, but when recording information with a device with a long magnetic field rise time When performing, wait until the magnetic field rises to the level required for erasing and then start erasing
Further, recording cannot be performed immediately after the erasing is completed, and it is necessary to wait until the magnetic field rises to a magnitude required for recording before performing recording. Even if overwriting becomes possible, a waiting time for the recording operation is necessary.
That is, a large overhead time is generated even when recording a small amount of information, and the actual operating rate of the magneto-optical recording / reproducing apparatus is greatly reduced. Therefore, shortening the magnetic field rise time is very important for improving the performance of the magneto-optical recording / reproducing apparatus.

Generally, the self-inductance of a bias magnetic field generating electromagnet used in a magneto-optical recording / reproducing apparatus is relatively large, such as several tens mH,
Further, since the strength of the magnetic field required for recording or erasing is large, the voltage V _S of the voltage source 21 must be set to a sufficiently large value in order to make the magnetic field rise time sufficiently small.

However, when the magnetic field rises, the absolute value V _{C of the} voltage across the exciting coil 1 and the absolute value V _I of the voltage across the recording current source 4 or the erasing current source 5 change as shown in FIG. After rising to V _C , V _C has a smaller value than the voltage V _S immediately after rising.

On the other hand, because V _I is the value obtained by subtracting V _I from V _S in the circuit configuration,
It is 0 V immediately after the magnetic field rises, but it becomes a value close to V _S after the magnetic field rises completely. Considering the power consumption now, the current values flowing through both are equal, so the ratio of V _C and V _I represents the ratio of power consumption. That is, most of the power consumption after the magnetic field completely rises occurs in the portion other than the exciting coil 1 and becomes heat to raise the temperature inside the magneto-optical recording / reproducing apparatus. As described above, the voltage V _S of the voltage source 21 needs to be increased, but since the power consumption of the entire circuit is proportional to V _S as long as the current is constant, this temperature rise becomes a non-negligible amount, and the magneto-optical recording medium However, it has a problem that it shortens the life of the optical disk, adversely affects the optical head that is particularly vulnerable to temperature rise, and deteriorates the reliability of information.

In view of the above problems, the present invention provides a bias magnetic field generator capable of reducing power consumption without adversely affecting the magnetic field rise time.

Means for Solving the Problems In order to achieve this object, a bias magnetic field generating apparatus of the present invention is an electromagnet composed of an exciting coil and a magnetic core around which the exciting coil is wound, and a voltage for driving the electromagnet. A first voltage source that provides a driving voltage lower than that of the first voltage source to the electromagnet;
Switching means for switching between the voltage source and the second voltage source, a voltage determining section for detecting an applied voltage of the exciting coil and comparing it with a reference voltage, and a control for controlling the switching means by a signal from the voltage determining section. When the magnetic field of the electromagnet is raised, the electromagnet is initially driven by the first voltage source, and then the control unit controls the switching unit according to the output of the voltage determination unit. In the configuration, the drive voltage source of the electromagnet is switched to the second voltage source.

With this configuration, the magnetic field of the electromagnet is first raised by the high voltage source that is the first voltage source, and then the voltage determination unit detects the voltage of the exciting coil of the electromagnet and compares it with the voltage of the reference voltage source to perform the excitation. When the voltage of the coil or the result of amplifying the voltage of the exciting coil becomes smaller than the voltage of the reference voltage source, a signal is output from the voltage determination unit to the control unit, and the control unit uses the voltage source as the second voltage source. The voltage switching unit switches the voltage source by outputting a signal for switching to the voltage source to the voltage switching unit. That is, the voltage of the drive circuit is switched between when the magnetic field is raised and other times, and when the magnetic field rises, the high voltage source is used to shorten the magnetic field rise time, and when the rise is almost complete, the low voltage source is used. By doing so, the power consumption of the entire circuit is reduced.

The "rise of the magnetic field" referred to in the present invention means a time when the magnetic field is changed by the electromagnet, and includes a time when the magnetic field is changed from the state showing the value of the predetermined magnetic field, and it is not always necessary to change the magnetic field from 0 magnetic field. It's not just a launch.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a bias magnetic field generator according to an embodiment of the present invention.

In FIG. 1, 1 is an exciting coil, 2 is a magnetic core, 4 is a recording current source, and 5 is an erasing current source, which is the same as the conventional example. 14,1
Reference numeral 5 denotes a differential amplifier that amplifies the potential difference between both ends of the exciting coil 1 by the magnitude A of the amplification factor, and performs amplification of opposite polarities. The output S ₈ of the differential amplifier 14 is input to the comparator 16, and the output S ₇ of the differential amplifier 15 is input to the comparator 17. Comparator 1
6, 17 is a reference voltage source 1 output voltage S _8, S ₇ of the differential amplifier 14, 15
Compared with the voltage V _{ref of} 8, the voltage of the outputs S ₁₀ and S ₉ becomes V _H when the voltages S ₈ and S ₇ become less than the voltage V _ref , and the output S ₈ when S ₈ and S ₇ are larger than V _{ref. 10} and S ₉ become 0. Reference numerals 12 and 13 are voltage sources for applying a voltage to the exciting coil 1, which are constant voltages V _SH and V _SL , respectively.
A high voltage source and a low voltage source that maintain Where V _SH ＞ V
_SL . The voltage V _ref of the reference voltage source 18 is set to a voltage at which the comparators 16 and 17 operate when the potential difference across the exciting coil 1 drops to a value that can be driven by the output V _SL of the low voltage source. . Reference numeral 30 denotes a control unit, which signals the timing and sequence of ON / OFF operations of the switches 6 to 11 by transistors or the like for switching the high voltage source 12 and the low voltage source 13 for driving the exciting coil 1 and switching the polarity of the output magnetic field. Indication of input section (not shown) and output of comparators 16 and 17 via lines S _{1 to} S ₆
Controlled according to S _10, S _9. Signal lines S ₁ , S ₂ , S ₃ , S ₄ ,
S ₅ and S ₆ correspond to switches 6, 10, 9, 8, 11, and 1 on a one-to-one basis, and when the voltage on the signal line becomes V _H or higher, the corresponding switch turns on, and other voltages Then the corresponding switch is turned off.

The operation of the bias magnetic field generator configured as described above will be described below.

First, when performing the erase operation, as shown in FIG.
30 raises the voltage of signal lines S ₁ and S ₃ to V _H at time t ₁ . Then, the switches 6 and 9 in FIG. 1 are turned on and the circuit is closed, and the current flows from the high voltage source 12 to the switch 6, the exciting switch 1, the switch 9 and
Flowing through the erasing current source 5, the electromagnet composed of the exciting coil 1 and the magnetic core 2 starts to give the erasing bias magnetic field to the magneto-optical recording medium (not shown).

Immediately after the voltages S ₁ and S ₃ become V _H and the switches 6 and 9 are turned on, the output S ₇ of the differential amplifier 15 becomes larger than V _ref , and the output S ₉ of the comparator 17 becomes 0 from V _H. become. Then, at time t ₂ , S ₇
When V _ref or less, S ₉ rises from 0 to V _H
30 sets S ₁ to 0 and S ₂ to V _H when the rising edge of S ₉ is detected.
To Then, the switch 6 shown in FIG. 1 is turned off, and at the same time, the switch 10 is turned on.
Flows through the switch 10, the exciting coil 1, the switch 9, and the erasing current source 5.

An optical head (not shown) gives an erasing light spot to the magneto-optical recording medium after waiting until the bias magnetic field has a size capable of performing the erasing operation, and executes the erasing operation. Control unit 30 and the erasing at time t ₃ to complete the dropping the voltage of the signal line S _2, S ₃ at 0V. Then, the switches 10 and 9 are turned off, the circuit is opened and the current is cut off, and the electromagnet constituted by the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

When performing the recording operation next, as shown in FIG.
Raises the voltage of signal lines S ₄ and S ₆ to V _H at time t ₄ . Then, the switches 8 and 7 in FIG. 1 are turned on to close the circuit, and the current flows from the high voltage source 12 through the switch 8, the exciting coil 1, the switch 7 and the recording current source 4, and the exciting coil 1 and the magnetic An electromagnet composed of the core 2 begins to apply a recording bias magnetic field to the magneto-optical recording medium.

Immediately after the voltages S ₄ and S ₆ become V _H and the switches 8 and 7 are turned on, the output S ₈ of the differential amplifier 14 becomes larger than V _ref , and the output S ₁₀ of the comparator 16 becomes 0 from V _H. become. After that, at time t ₅ , S ₈ becomes V
_When it becomes less than _ref , S ₁₀ rises from 0 to V _H , and the control unit
When 30 detects the rising edge of S ₁₀ , S _{4 is set} to 0 and S _{5 is set} to V
_Set to _H. Then, the switch 8 shown in FIG. 1 is turned off, and at the same time, the switch 11 is turned on.
Flow through the switch 11, the exciting coil 1, the switch 7, and the recording current source 5. After waiting until the bias magnetic field reaches a level at which the recording operation is possible, the optical head gives an optical spot according to the information to be recorded on the magneto-optical recording medium, and executes the recording operation.

At the time t ₆ when the recording is completed, the control unit 30 controls the signal lines S ₅ , S ₆
Drop the voltage to 0V. Then, the switches 11 and 7 are turned off, the circuit is opened and the current is cut off, and the electromagnet constituted by the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

FIG. 3 shows changes in the absolute value V _{G of the} voltage across the exciting coil and the absolute value V _I of the voltage across the recording current source 4 or the erasing current source 5 when the magnetic field of the exciting coil 1 of this embodiment rises. . Since the magnitude of the amplification factor of the differential amplifier is A,
When V _{C drops} below A × V _ref , the voltage source is switched from the high voltage source to the low voltage source, so the magnitude of V _I decreases after switching and the magnitude after completion of rising is the conventional example. It is significantly smaller than. That is, the power consumption is determined by the voltage V _SL of the low voltage source 13 and hardly depends on the voltage V _SH of the high voltage source. Therefore, compared with the conventional example, the power consumption of the entire circuit after the completion of the rise of the magnetic field is significantly reduced.

Normally, a magneto-optical recording / reproducing apparatus is used for a power supply of more than 10V used for a motor drive system and a logic circuit for a control system.
Since it has two power supplies of 5V, the two power supplies of the high voltage source 12 and the low voltage source 13 shown in the embodiment can be easily obtained.

As described above, according to the present embodiment, the voltage of the drive circuit is switched between the time when the magnetic field is raised and the state other than that, and the rise time of the magnetic field is shortened by using the high voltage source when the magnetic field rises. When the startup is almost completed, the power consumption of the whole circuit can be reduced by using the low voltage source.

Also, since the voltage of the high voltage source 12 has almost no effect on the power consumption, it is possible to prepare a power supply with a sufficiently large V _SH value.
It is also possible to significantly shorten the rise time of the magnetic field.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a diagram showing a bias magnetic field generator according to the second embodiment of the present invention. In FIG. 4, 1 is an exciting coil, 2
Is a magnetic core, 4 is a recording current source, 5 is an erasing current source, and 6 to 11
Is a switch, 12 is a high voltage source, 13 is a low voltage source, 14 is a differential amplifier, 16 and 17 are comparators, and 30 is a control unit, which are the same as those in the first embodiment. The output S ₇ of the differential amplifier 14 is input to the non-inverting input of the comparator 16 and the inverting input of the comparator 17. Comparator
17 compares the output voltage S ₇ of the differential amplifier 14 with the voltage V _ref of the positive reference voltage source 19, and when S ₇ becomes V _ref or less, the voltage of the output S ₈ becomes
The output S ₈ goes to 0 when it goes to V _H and S ₇ is greater than V _ref . Similarly, the comparator 16 compares the output voltage S ₇ of the differential amplifier 14 with the voltage −V _ref of the negative reference voltage source 20, and when S ₇ becomes −V _ref or more, the voltage of the output S ₉ becomes V _H and S _The output S ₉ is 0 when ₇ is lower than −V _ref . Further, the voltage magnitude V _ref of the positive reference voltage source 19 and the negative reference voltage source 20 is when the magnitude of the potential difference between both ends of the exciting coil 1 falls to a value that can be driven by the output V _SL of the low voltage source 13. Set to the voltage at which the comparator operates.

The operation of the bias magnetic field generator configured as described above will be described below.

First, when performing the erase operation, as shown in FIG.
30 raises the voltage of signal lines S ₁ and S ₃ to V _H at time t ₁ . Then, the switches 6 and 9 shown in FIG. 4 are turned on and the circuit is closed, and the current flows from the high voltage source 12 through the switch 6, the exciting coil 1, the switch 9 and the erasing current source 5 to the exciting coil 1 and the magnetic field. An electromagnet composed of the core 2 starts to give an erasing bias magnetic field to a magneto-optical recording medium (not shown). Immediately after the voltage of S ₁ and S ₃ becomes V _H and the switches 6 and 9 are turned on, the output S ₇ of the differential amplifier 14 becomes larger than V _ref , and the output S ₈ of the comparator 17 becomes V _H from V _H. It becomes 0. Then, at time t ₂ , when S ₇ becomes V _ref or less, S ₈
Rises from 0 to V _H , and the control unit 30 sets S ₁ to 0 and S ₂ to V _H when the rise of S ₈ is detected. Then, the switch 6 shown in FIG. 4 is turned off, and at the same time, the switch 10 is turned on, and the current flows from the low voltage source 13 through the switch 10, the exciting coil 1, the switch 9, and the erasing current source 5. An optical head (not shown) gives an erasing light spot to the magneto-optical recording medium after waiting until the bias magnetic field has a size capable of performing the erasing operation, and executes the erasing operation. Control unit 30 and the erasing at time t ₃ to complete the voltage of the signal line S _2, S ₃
Drop to 0V. Then, the switches 10 and 9 are turned off, the circuit is opened and the current is cut off, and the electromagnet constituted by the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

Next, the case of performing the recording operation will be described. As shown in FIG. 5, the control unit 30 raises the voltage of the signal lines S ₄ and S ₆ to V _H at time t ₄ . Then, the switches 8 and 7 in Fig. 4 are turned on and the circuit is closed, and the current flows from the high voltage source 12 to the switch 8 and the exciting coil.
1, a switch 7, a current source 4 for recording, and an electromagnet composed of an exciting coil 1 and a magnetic core 2 starts to give a bias magnetic field for recording to the magneto-optical recording medium. Immediately after the voltages S ₄ and S ₆ become V _H and the switches 8 and 7 are turned on, the differential amplifier 14
The output S ₇ of the comparator 16 is lower than −V _ref , and the output S ₉ of the comparator 16 is V _H
To 0. After that, when S ₇ becomes −V _ref or more at time t ₅ , S ₉ rises from 0 to V _H , and the control unit 30 sets S ₄ to 0 and S ₅ to V _H when the rise of S ₉ is detected. To Then, the switch 8 in FIG. 4 is turned off, and at the same time, the switch 11 is turned on. This time, the current flows from the low voltage source 13 to the switch 11,
It flows through the exciting coil 1, the switch 7, and the recording current source 5. After waiting until the bias magnetic field reaches a level at which the recording operation is possible, the optical head gives an optical spot according to the information to be recorded on the magneto-optical recording medium, and executes the recording operation.

At the time t ₆ when the recording is completed, the control unit 30 controls the signal lines S ₅ , S ₆
Drop the voltage to 0V. Then, the switches 11 and 7 are turned off, the circuit is opened and the current is cut off, and the electromagnet constituted by the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

This embodiment has the same effect as the first embodiment, but
It is possible to eliminate one differential amplifier as compared with the above embodiment.

A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is a block diagram showing a bias magnetic field generator in the third embodiment of the present invention. In FIG. 6, 1 is an exciting coil, 2 is a magnetic core, 4 is a recording current source, 5 is an erasing current source, 6 to 11 are switches, 12 is a high voltage source, 13 is a low voltage source,
Reference numerals 16 and 17 are comparators and reference numeral 18 is a reference voltage source. The above is the same as that of the first embodiment.

Both ends of the exciting coil 1 are input to the non-inverting inputs of the comparators 16 and 17, respectively, and the reference voltage source 18 is input to the inverting inputs of the comparators 16 and 17. Comparator 16 is the voltage at one end of exciting coil 1.
The S ₇ is compared with the voltage V _ref of the reference voltage source 18, the voltage of the output S ₉ S ₇ is equal to or greater than V _ref becomes V _H, when S ₇ is less than V _ref is output S ₈ 0 . Similarly, the comparator 17 compares the voltage S ₈ at the other end of the exciting coil 1 with the voltage V _ref of the reference voltage source 18, and S ₈
Above V _ref , the voltage at output S ₁₀ goes to V _H and S ₈ goes to V _ref.
When it is lower, the output S ₁₀ becomes 0. Reference numeral 31 denotes a control unit, which is basically the same as the control unit 30 shown in the first embodiment, except that the signal lines S _{4 to} S ₆ are used during the erasing operation and the signal lines S _{4 to} S ₆ are used during the recording operation.
The difference is that S _{1 to} S ₃ are always maintained at 0V.

The operation of the bias magnetic field generator configured as described above will be described below.

First, when performing the erase operation, as shown in FIG.
31 raises the voltage of signal lines S ₁ and S ₃ to V _H at time t ₁ . Then, the switches 6 and 9 in FIG. 6 are turned on and the circuit is closed, and the current flows from the high voltage source 12 through the switch 6, the exciting coil 1, the switch 9 and the erasing current source 5, and the exciting coil 1 and the magnetic An electromagnet composed of the core 2 starts to give an erasing bias magnetic field to the magneto-optical recording medium. Voltages S ₁ and S ₃ go to V _H and switches 6 and 9
Immediately after that but was turned on, the signal S ₇ is gradually began to rise, S ₇ is
When V _ref is reached, the output S ₉ of the comparator 16 rises from 0 to V _H. Then, the control unit 31 sets S ₂ to V _H and drops S ₁ to 0. At this time, the switches 6 and 10 are switched, and the voltage source for driving the exciting coil 1 is momentarily switched from the high voltage source 12 to the low voltage source 13. Immediately after the switching, as shown in FIG.
S ₇ drops below V _ref , the output S ₉ of the comparator 16 drops to 0 again, the drive voltage source of the exciting coil 1 switches to the high voltage source 12 again, and S ₇ starts to rise again. But at this time S ₇
Since it has not dropped to 0V, the time to rise to V _ref next becomes shorter than the first time, and thereafter switching between the high voltage source 12 and the low voltage source 13 is repeated while showing a sawtooth waveform as shown in FIG. The time during which the high voltage source 12 is driving is gradually shortened, and finally the driving voltage source of the exciting coil is switched to the low voltage source 13 at time t ₂ . After waiting until the bias magnetic field reaches a level at which the erasing operation is possible, the optical head gives an erasing light spot to the magneto-optical recording medium and executes the erasing operation. 31 with the control unit erasure is time t ₃ to complete the dropping the voltage of the signal line S _2, S ₃ at 0V. Then switch 10,9
Turns off, the circuit opens, the current is cut off, and the excitation coil 1
The electromagnet constituted by the magnetic core 2 and the magnetic core 2 stops the output of the magnetic field.

When performing the recording operation next, as shown in FIG.
Raises the voltage of signal lines S ₄ and S ₆ to V _H at time t ₄ . Then, the switches 8 and 7 in FIG. 6 are turned on to close the circuit, and the current flows from the high voltage source 12 through the switch 8, the exciting coil 1, the switch 7 and the recording current source 4, and the exciting coil 1 and the magnetic An electromagnet composed of the core 2 starts to apply a recording bias magnetic field to the magneto-optical recording medium. Immediately after the voltages S ₄ and S ₆ become V _H and the switches 8 and 7 are turned on, the signal S ₈ gradually starts to rise and S ₈ becomes V
_{When ref} is reached, the output S ₁₀ of the comparator 17 rises from 0 to V _H. Then, the control unit 31 sets S ₅ to V _H and drops S ₄ to 0. The time of switching the switch 8 and the switch 11, a voltage source for driving the exciting coil 1 is switched instantaneously from a high voltage source 12 to the low voltage source 13, as shown in Figure 7 immediately after switching S ₈
Falls below V _ref , the output S ₁₀ of the comparator 17 drops to 0 again, the drive voltage source of the exciting coil 1 switches to the high voltage source 12 again, and S ₈ starts to rise again. But at this time S ₇ is 0V
Since it has not fallen to V _ref , the time to rise to V _ref becomes shorter than the first time, and after that, switching between the high voltage source 12 and the low voltage source 13 is repeated while showing the sawtooth waveform as shown in FIG. Then, the driving time of the high voltage source 12 is shortened, and finally the driving voltage source of the exciting coil is switched to the low voltage source 13 at time t ₅ . After waiting until the bias magnetic field reaches a level at which the recording operation is possible, the optical head gives an optical spot according to the information to be recorded on the magneto-optical recording medium,
Perform recording operation. Control unit 31 and the recording is time t ₆ to complete the dropping the voltage of the signal line S _5, S ₆ to 0V. Then, the switches 11 and 7 are turned off, the circuit is opened and the current is cut off, and the electromagnet constituted by the exciting coil 1 and the magnetic core 2 stops the output of the magnetic field.

This embodiment has the same effect as the first embodiment, but
It is possible to eliminate the differential amplifier altogether compared to the embodiment of the present invention, and the switching of the voltage source is not suddenly switched to the low voltage source as in the first and second embodiments, but is driven by the high voltage source. Is a switching system in which the bias voltage is gradually lowered, the total driving time by the high voltage source is longer than that in the first and second embodiments, and a bias magnetic field generator having a shorter magnetic field rise time can be realized. .

EFFECTS OF THE INVENTION The present invention relates to an electromagnet composed of an exciting coil for applying a bias magnetic field for recording and erasing to a magneto-optical recording medium and a magnetic core around which the exciting coil is wound, and a voltage for driving the electromagnet. A first voltage source, a second voltage source that gives the electromagnet a driving voltage lower than that of the first voltage source, a switching unit that switches between the first voltage source and the second voltage source, and A high voltage source, which is a first voltage source, has a voltage determination unit that detects an applied voltage to the exciting coil and compares it with a reference voltage, and a control unit that controls the voltage switching unit according to a signal from the voltage determination unit. When the voltage of the exciting coil of the electromagnet started in step 2 becomes lower than the voltage of the low voltage source which is the second voltage source, the comparator outputs a signal to the control section, and the control section changes the voltage source to the low voltage source. Turn off the signal to switch The voltage switching means switches the voltage source by outputting the voltage to the switching means. That is, the voltage of the drive circuit is switched at the time of rising the magnetic field and in other states, and the rising time of the magnetic field is shortened by using the high voltage source at the rising of the magnetic field, and the low voltage source is used when the rising is almost completed. As a result, the power consumption of the entire circuit can be reduced. That is, efficiency improvement is achieved without adversely affecting the rise time.

Further, since the voltage of the high voltage source has almost no effect on the power consumption, it is possible to prepare a power source having a sufficiently large voltage, and it is also possible to significantly shorten the rise time of the magnetic field.
Further, since unnecessary power consumption can be reduced, the temperature rise inside the magneto-optical recording / reproducing apparatus can be minimized, and the optical head relatively vulnerable to temperature change can be stably operated to improve the information reliability. That is, it is possible to realize a bias magnetic field generator capable of obtaining various excellent effects.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a bias magnetic field generator according to an embodiment of the present invention, and FIG. 2 is a timing chart showing signal states of respective parts at the time of erasing and recording of the bias magnetic field generator of FIG. FIG. 3 is a characteristic diagram showing changes in the voltage across the exciting coil and the voltage across the current source when the magnetic field of the bias magnetic field generator of FIG. 1 rises, and FIG. 4 is the bias in the second embodiment of the present invention. FIG. 5 is a block diagram of a magnetic field generator, FIG. 5 is a timing chart showing the states of signals at various portions during erasing and recording of the bias magnetic field generator of FIG. 4, and FIG. 6 is a bias magnetic field in the third embodiment of the present invention. FIG. 7 is a block diagram of the generator, FIG. 7 is a timing chart showing the state of signals of each part at the time of erasing and recording of the bias magnetic field generator of FIG. 6, and FIG. 8 is a block of the conventional bias magnetic field generator. FIG. 9 is a timing chart showing the signal states of various parts during erasing and recording of the bias magnetic field generator of FIG. 8, and FIG. 10 is a diagram of the exciting coil at the rising of the magnetic field of the bias magnetic field generator of FIG. It is a characteristic view which shows the change of the voltage between both ends and the voltage between both ends of a current source. 1 ... Excitation coil, 2 ... Magnetic core, 3,30,31 ... Control unit,
4 ... Recording current source, 5 ... Erase current source, 6-11 ...
Switch, 12 …… High voltage source, 13 …… Low voltage source, 14,15…
… Differential amplifier, 16,17 …… Comparator, 18 …… Reference voltage source, 1
9 …… Positive reference voltage source, 20 …… Negative reference voltage source.

Claims (4)

[Claims] 1. An electromagnet composed of an exciting coil for giving a bias magnetic field for recording and erasing to a magneto-optical recording medium and a magnetic core around which the exciting coil is wound, and a first magnet for giving a driving voltage to the electromagnet. A voltage source, a second voltage source that gives the electromagnet a driving voltage lower than that of the first voltage source, a switching unit that switches between the first voltage source and the second voltage source, and the exciting coil Of the applied voltage is detected and compared with a reference voltage, and a control means for controlling the switching means, and when the magnetic field of the electromagnet is raised,
Initially, the electromagnet is driven by the first voltage source, and then the control unit controls the switching means according to the output of the voltage determination unit to switch the drive voltage source of the electromagnet to the second voltage source. Bias magnetic field generator characterized by. 2. A voltage determination section detects and amplifies a potential difference between both ends of an exciting coil, compares the amplified voltage with a reference voltage output from a reference voltage source, and outputs a comparison result to a control section. The first aspect of the invention is characterized in that
The bias magnetic field generator according to the item. 3. The voltage determination unit is configured to compare at least one of the voltages across the exciting coil with a reference voltage output from a reference voltage source, and output the comparison result to the control unit. The bias magnetic field generator according to claim 1. 4. The voltage determination unit is driven by the first voltage source when the magnetic field of the electromagnet is activated, detects and amplifies the applied voltage of the exciting coil, and the amplified voltage is smaller than the voltage of the reference voltage source. The bias magnetic field generating device according to claim 1, wherein a signal for switching the voltage source for driving the exciting coil to the second voltage source is output to the control unit when .