JPS63124202A - Bias magnetic field generator - Google Patents

Abstract

PURPOSE:To reduce the power consumption of the whole circuit by switching the voltage of a driving circuit at the time of rising of a magnetic field and at the other time, using a high voltage source at the time of rising the magnetic field to shorten the rising time of the magnetic field, and after almost completing the rising, using a low voltage source. CONSTITUTION:The titled bias magnetic field generator is provided with a means for switching a 1st voltage source 12 to apply a driving voltage to an electromagnet and a 2nd voltage source 13 to apply a lower driving voltage and a control part 30 for controlling the voltage switching means based on a signal outputted from a voltage deciding part for detecting a voltage impressed to an exciting coil 1 and comparing the detected voltage with a reference voltage 18. When the voltage of the exciting coil 1 raised by the 1st high voltage source 12 is reduced lower than the voltage of the 2nd low voltage source 13, signals are outputted from comparators 16, 17 to the control part 30 to switch the voltage source. Since the high voltage source is used at the time of rising the magnetic field to shorten the rising time of the magnetic field and the low voltage source is used after almost completing the rising, the power consumption of the whole circuit can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a bias magnetic field generating device used for magneto-optical recording and reproduction, which is used for external storage of electronic computers, music and video signals, and recording and reproduction of other information. be.

Background of the Invention In recent years, with the development of electronic computers and means of high-speed mass transmission of information, low cost, high density, and large capacity.

Nonvolatile storage devices with high-speed transfer capabilities are required, and magnetic disk devices are often used, but their recording density is low, the price per unit of information is high, and fixed magnetic disk devices in particular require medium replacement. There are problems such as difficulty. Optical recording is currently in the spotlight as a technology that can solve these problems, and rewritable magneto-optical recording in particular has high expectations in many fields.

Conventional bias magnetic field generators drive electromagnets with a single voltage source.

Hereinafter, a conventional bias magnetic field generating device as described above will be explained with reference to the drawings.

Fig. 8 shows a conventional bias magnetic field generating device. Configure an electromagnet that provides a bias magnetic field. Reference numeral 3 denotes a control section that sends signals according to instructions from an input section (not shown) to control the timing and order of on/off operations of switches 6 to 9 by transistors and the like that drive the excitation coil 1 and switch the polarity of the output magnetic field. Control via lines 81-S4. Signal line”+18
2+ SSs S4 corresponds one-to-one to the switches 6.9 and 8.7, respectively, and the signal line voltage vH'
When the voltage is higher than that, the corresponding switch is turned on, and at any other voltage, the corresponding switch is turned off.

21 is a voltage source that applies voltage to the excitation coil 1, and maintains a constant voltage V. Reference numerals 4 and 6 denote a recording current source and an erasing current source that supply current to the exciting coil 1 when the exciting coil 1 performs a recording operation and an erasing operation, respectively.

The operation of the bias magnetic field generating device configured as described above will be explained below.

First, when performing an erase operation, the control unit 3 changes the voltage of the signal line S1*82 to vH at time t1, as shown in FIG.
Raise it to Then, switch 6.9 in FIG. 8 is turned on, closing the circuit, and current flows from voltage source 21 to switch 6, excitation coil 1. Switch 9. flows through the erase current source 5;
An electromagnet composed of an excitation coil 1 and a magnetic core 2 begins to apply an erasing bias magnetic field to the magneto-optical recording medium. After waiting until the bias magnetic field becomes large enough to perform an erasing operation, an optical head (not shown) applies an erasing light spot to the magneto-optical recording medium to perform the erasing operation.

When erasing is completed and time t2 arrives, the control unit 3 switches the signal line S1. Reduce the voltage of S2 to Ov. Then switch 6.
9 is turned off, the circuit is opened and the current is cut off, and the electromagnet composed of the exciting coil 1 and the magnetic core 2 stops outputting the magnetic field.

When performing the next recording operation, the control unit 3
increases the voltage of the signal line SS*S4 to vH at time t3. Then, switches 8 and 7 in FIG. 8 are turned on, closing the circuit, and current flows from voltage source 21 to switch 8. Excitation coil 1. The current flows through the switch 7 and the recording current source 4, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 begins to apply a recording bias magnetic field to a magneto-optical recording medium (not shown). After waiting until the bias magnetic field becomes large enough to perform a recording operation, the optical head applies a light spot corresponding to the information to be recorded on the magneto-optical recording medium, and the recording operation is executed. When recording is completed and time t4 arrives, the control unit 3 connects the signal line SS.
The voltage of m s is dropped to Ov. Then switches 8, 7
is turned off, the circuit is opened and the current is cut off, and the excitation coil 1
The electromagnet composed of the magnetic core 2 and the magnetic core 2 stops outputting the magnetic field.

Problems to be Solved by the Invention However, the above 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 excitation coil 1 and the magnetic core 2 rises to a magnitude that can be recorded or erased, that is, the length of the magnetic field rise time, is determined by the voltage source 21. It is almost inversely proportional to the voltage V, . Normally, magneto-optical recording is performed after erasing the relevant area on the medium as in the conventional example, in order to avoid overriding, but information is recorded using a device with a long magnetic field rise time. When performing this, first wait until the magnetic field rises to the size necessary for erasing, then start erasing, and even after erasing is completed, recording cannot be performed immediately, and the magnetic field rises to the size necessary for recording. You need to wait until then before recording.

Even if override is possible, a waiting time is required for the recording operation. That is, a large amount of overhead time occurs 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 magneto-optical recording and reproducing devices.

Generally, the self-inductance of an electromagnet for generating a bias magnetic field used in a magneto-optical recording/reproducing device is relatively large at several tens of mH, and the strength of the magnetic field required for recording or erasing is also large, so in order to sufficiently reduce the magnetic field rise time, it is necessary to The voltage vB of the voltage source 21 must be set to a sufficiently large value.

However, the absolute value Vc of the voltage across the excitation coil 1 and the relative value vX of the voltage across the recording current source 4 or erasing current source 60 change as shown in FIG. After the voltage completely rises, vc becomes a smaller value than the voltage vs immediately after the voltage rises.

On the other hand, vX is from Vs to V! due to the circuit configuration. Therefore, immediately after the magnetic field starts up, it is OV, but after the magnetic field has completely started up, it becomes a value close to Vs.

Considering power consumption now, the current value flowing through both is equal, so the ratio of vOh vX represents the ratio of power consumption. That is, most of the power consumption after the magnetic field has completely risen is generated in parts other than the excitation coil 1, and all of it becomes heat, raising the temperature inside the magneto-optical recording and reproducing apparatus. As mentioned above, it is necessary to increase the voltage vs of the voltage source 21, but as long as the current is constant, the power consumption of the entire circuit is lower than Vs.
Since this temperature rise is proportional to was.

In view of the above problems, the present invention provides a bias magnetic field generating device that can reduce power consumption without adversely affecting the magnetic field rise time.

Precautionary Means to Solve the Problems In order to achieve this object, the bias magnetic field generating device of the present invention includes an electromagnet composed of an excitation coil and a magnetism core around which the excitation coil is wound, and a drive magnet for the electromagnet. a second voltage source that provides the electromagnet with a driving voltage lower than that of the first voltage source;
a switching means for switching between the voltage source and the second voltage source; a voltage determining section for detecting the voltage applied to the excitation coil and comparing it with a reference voltage; and controlling the voltage switching means based on a signal from the voltage determining section. It consists of a control section and a control section.

Effect With this configuration, the magnetic field of the electromagnet is first started up by a high voltage source which is the first voltage source, and then the voltage determination section detects the voltage of the excitation coil of the electromagnet and compares it with the voltage of the reference voltage source, When the voltage of the coil or the result of amplifying the voltage of the excitation coil becomes smaller than the voltage of the reference voltage source, a signal is output from the voltage determination section to the control section, and the control section selects the voltage source as a second voltage source. The voltage switching means switches the voltage source by outputting a signal to switch to a low voltage source to the voltage switching means.In other words, the voltage of the drive circuit is switched at the time of magnetic field startup and in other states, and the high voltage is set at the time of magnetic field startup. By using a power source, the rise time of the magnetic field is shortened by nine hours, and once the rise is almost complete, a low voltage power source is used to reduce the power consumption of the entire circuit.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a bias magnetic field generating device in one 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 6 is an erasing current source, which are the same as in the conventional example. 14
．． Reference numeral 15 denotes a differential amplifier that amplifies the potential difference between both ends of the excitation coil 10 by an amplification factor, and performs amplification with opposite polarities. The output S8 of the differential amplifier 14 is sent to the comparator 16,
Similarly, the output S7 of the differential amplifier 16 is sent to a comparator 17.

Comparators 16.17 output voltage 8 of differential amplifier 14.15.
8*S7 is compared with the voltage Vref of the reference voltage source 18, and when the voltage S8a S7 becomes less than the voltage Vraf', the voltage of the output S10*S9 becomes v! Becomes I% S8
a When S7 is larger than Vref, output S1o,
S9 becomes 0.

Reference numerals 12 and 13 denote voltage sources that apply voltage to the excitation coil 1, which are a high voltage source and a low voltage source that maintain a constant voltage v81*vSLr, respectively. Here, V5g) 'l'5L.

Further, the voltage Vrθf of the reference voltage source 18 is
The comparators 16 and 17 are set to a voltage that operates when the potential difference between the two ends of the voltage drops to a value that can be driven by the output vsL of the low voltage source. 30 is a control unit, which includes a high voltage source 12 for driving the excitation coil 1. A switch 6 including a transistor or the like for switching the low voltage source 13 and switching the polarity of the output magnetic field.
~11 on.

The timing and order of the off operation are controlled via signal lines 81 to S6 according to instructions from an input section (not shown) and outputs JO and S9 of the comparator 16.1. Signal line S1゜S2*
S5* S4a S5+ s, respectively, are switches 6.
10゜9.8 and 11.7 correspond one to one, and when the voltage of the signal line exceeds a certain voltage vH, the corresponding switch is turned on, and at other voltages, the corresponding switch is turned off. .

The operation of the bias magnetic field generating device configured as described above will be explained below.

First, when performing an erase operation, the control unit 3o raises the voltage of the signal line 81m'3S to vH at time t1, as shown in FIG. Switch 6.9 in FIG. 1 is then turned on, closing the circuit, and current flows from high voltage source 12 to switch e.
, excitation coil 1. Switch 9. The current flows through the erasing current source 6, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 begins to apply an erasing bias magnetic field to the magneto-optical recording medium (not shown).

Voltage S1. Immediately after S5 goes to vH and switch 6.9 turns on, the output $7 of differential amplifier 16 becomes Vref
The output S9 of the comparator 17 becomes vII
becomes 0. Thereafter, when S7 becomes equal to or less than Yref at time t2, S9 rises from 0 to vIK, and when the control section 3o detects the rising edge 9 of S9, it sets Sl to 0 and sets Sl to vB. Then, at the same time that switch 6 in FIG. 1 is turned off, switch 10 is turned on, and current flows from low voltage source 13 to switch 10 and excitation coil 1. Switch 9. It flows through the erase current source 6.

After waiting until the bias magnetic field becomes large enough to perform the erasing operation, an optical head (not shown) applies an erasing optical slit to the magneto-optical recording medium to perform the erasing operation. When erasing is completed and time t3 arrives, the control unit 3o connects the signal line S.
2. Reduce the voltage of S5 to Ov. Then switch 1o,
9 is turned off 9, the circuit is opened and the current is cut off, and the electromagnet composed of the exciting coil 1 and the magnetic core 2 stops outputting the magnetic field.

When performing the next recording operation, the control unit 3
o changes the voltage of signal line S4 # S6 to V■ at time t4.
Raise it to Switches 8 and 7 in FIG. 1 are then turned on, closing the circuit, and current flows from high voltage source 12 to switch 8.
Excitation coil 1. A current flows through the switch 7 and the recording current source 4t, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 begins to apply a recording bias magnetic field to the magneto-optical recording medium.

Immediately after the voltage s4e S6 becomes V, and the switches 8 and 7 are turned on, the output S8 of the differential amplifier 14 becomes vr
ot greater than 9, the output 910 of comparator 16 is v
From H to O. Thereafter, when S8 becomes equal to or less than Vref at time t5, it rises from 510Fio to vH, and when the control unit 3o detects the rise of 810, it sets 84 to 0 and S5 to vlI. Then switch 8 in Figure 1
Switch 11 is turned on at the same time that switch 11. is turned off, and current now flows from low voltage source 13 to switch 11. Excitation coil 1
．． The current flows through the switch 7 and the recording current source 5. After waiting until the bias magnetic field becomes large enough to perform a recording operation, the optical head applies a light spot corresponding to the information to be recorded on the magneto-optical recording medium, and the recording operation is executed.

When the recording is completed and time t6 arrives, the control unit 30 reduces the voltage of the signal lines S5 #S6 to oV. Then, the switches 11 and 7 are turned off, the circuit is opened and the current is cut off, and the electromagnet composed of the exciting coil 1 and the magnetic core 2 stops outputting a magnetic field.

FIG. 3 shows the absolute value vc of the voltage across the exciting coil 1 and the absolute value vX of the voltage across the recording current source 4 or erasing current source 6 when the magnetic field of the exciting coil 1 rises in this embodiment.
shows the change in Now, since the magnitude of the amplification factor of the differential amplifier is human, the voltage source is switched from a high voltage source to a low voltage source when vc drops below mu It decreases after that time, and the size after the rise is completed is significantly smaller than that of the conventional example. That is, power consumption is determined by the voltage VSH of the low voltage source 13 and is almost independent of the voltage VSH of the high voltage source. Therefore, compared to the conventional example, the power consumption of the entire circuit after the magnetic field has finished rising is significantly reduced.

Normally, a magneto-optical recording/reproducing device has two power supplies: a power supply of more than 10 V used for the motor drive system, etc., and a power supply of 6 V used for the logic circuit of the control system.
Two power sources, ie, low voltage source 13 and low voltage source 13, can be easily obtained.

As described above, according to this embodiment, the voltage of the drive circuit is switched between the magnetic field startup and other states, and the high voltage source is used at the magnetic field startup to shorten the magnetic field startup time. , the power consumption of the entire circuit can be reduced by using a low voltage source once the startup is almost complete.

Furthermore, since the voltage of the high voltage source 12 has little effect on power consumption, it is possible to prepare a power source with a sufficiently large vssi value, and 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 generating device in a second embodiment of the present invention. In Figure 4, 1 is an excitation coil, 2
is a magnetic core, 4 is a recording current source, 5 is an erasing current source, 6 to 1
1 is a switch, 12 is a high voltage source, 13 is a low voltage source, 14
is a differential amplifier 1e+17 is a comparator, 3o is a control section and the first
This is the same as the embodiment. Output S7 of differential amplifier 14
is input to the non-inverting input of comparator 16 and the inverting input of comparator 170. The comparator 17 compares the output voltage S7 of the differential amplifier 14 with the voltage Vref of the positive reference voltage source 19, and when S7 becomes less than Vref, the voltage of the output S8 becomes V, and when S7 is greater than Vref, the output S8 becomes becomes 0. Similarly, the comparator 16 is the differential amplifier 14
The output voltage S7 is the voltage Vre of the negative reference voltage source 20
When S7 becomes -Vref or more, the output S
The voltage at 9 is vI! When S7 is lower than -Vref, the output S9 becomes 0. Further, the magnitude of the voltage Vref of the positive reference voltage source 19 and the negative reference voltage source 2o is such that the magnitude of the potential difference between both ends of the excitation coil 1 is the same as that of the low voltage source 13.
The voltage is set to a voltage that activates the comparator when the voltage drops to a value that can be driven by the output VSL.

The operation of the bias magnetic field generating device configured as described above will be explained below.

First, when performing an erasing operation, as shown in FIG. 6, the control unit 3o controls the signal line S1. Increase the voltage of S3 to vH. Then, switches 6 and 9 shown in FIG. Switch 9. The erasing current flows through the erasing current source 5, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 begins to apply an erasing bias magnetic field to the magneto-optical recording medium (not shown). 511S3 voltage becomes vH, switch 6.9
Immediately after turning on, the output S7 of the differential amplifier 14 becomes Vr.
ef' becomes larger, and the output S8 of the comparator 17 becomes 0 from vB. After that, when S7 becomes equal to or less than Vref at time t2, S8 rises from 0 to vII, and when the control unit 3o detects the rise of S8, it sets 81 to 0.
Set S2 to vII. Then, at the same time that switch 6 in FIG. 4 is turned off, switch 1o is turned on, and current flows from low voltage source 13 to switch 10. Excitation coil 1. Switch 9. The erase current flows through the erase current source 5. After waiting until the bias magnetic field becomes large enough to perform an erasing operation, an optical head (not shown) applies an erasing light spot to the magneto-optical recording medium to perform the erasing operation. When erasing is completed and time t3 arrives, the control unit 3o switches the signal line S2. Reduce the voltage of S3 to Ov. Then, the switches 1o and 9 are turned off, the circuit is opened and the current is cut off, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 stops outputting a magnetic field.

Next, a case in which a recording operation is performed will be explained. As shown in FIG. 5, the control unit 3o controls the signal line S4 at time t4. S6
Increase the voltage to V, . Then switch 8 in Figure 4
, 7 are turned on to close the circuit and current flows from the high voltage source 12 to the switch 8 . The current flows through the excitation coil 1° switch 7 and the recording current source 4, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 begins to apply a recording bias magnetic field to the magneto-optical recording medium.

Immediately after the voltage S4 + S6 becomes vH and the switches 8 and 7 are turned on, the output S7 of the differential amplifier 14 becomes Vr.
ef, and the output S9 of the comparator 16 becomes vll
becomes 0. After that, at time t5, S7 becomes -Vref
'When S9 rises from 0 to vH, the control unit 3o detects the rise of S9, and S9 rises to vH.
to 0 and S5 to vH. Then, at the same time that switch 8 in FIG. 4 is turned off, switch 11 is turned on, and current flows from low voltage source 13 to switch 11. Excitation coil 1. The current flows through the switch 7 and the recording current source 6. After waiting until the bias magnetic field becomes large enough to perform a recording operation, the optical head applies a light spot corresponding to the information to be recorded on the magneto-optical recording medium, and the recording operation is executed.

When recording is completed and time t6 arrives, the control unit 30 reduces the voltage of the signal lines S5 #S6 to OV. Then, the switches 11 and 7 are turned off, the circuit is opened and the current is cut off, and the electromagnet composed of the exciting coil 1 and the magnetic core 2 stops outputting a magnetic field.

This embodiment has the same effect as the first embodiment, but
Compared to the embodiment described above, it is possible to eliminate one differential amplifier.

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 according to a 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, 6 is an erasing current source, 6 to 11 are switches, 12 is a high voltage source, 13 is a low voltage source, 16.17 1 is a comparator, and 18 is a reference voltage source, which are the same as in the first embodiment.

Both ends of the excitation coil 1 are each input to a non-inverting input of a comparator 16.17, and a reference voltage source 18 is input to an inverting input of the comparator 16.17. The comparator 16 is the excitation coil 1
The voltage S7 at one end of the reference voltage source 18 is the voltage "fre"
t, when S7 becomes equal to or higher than Vraf', the output S
The voltage at 9 becomes vH, and when S7 is lower than Vref, the output S8 becomes 0. Similarly, the comparator 17 converts the voltage S8 at the other end of the exciting coil 1 into the voltage Vr of the reference voltage source 18.
Compared with ef, when S8 becomes more than Vref, the output becomes 31.
The voltage of G becomes vH, and when S8 is lower than Vref, the output is 81 (l becomes 0. 31 is a control section, which is basically the same as the leg restraint shown in the first embodiment. However, during erasing operation, signal lines 84 to S6 are connected, and during recording operation, signal lines 81 to S6 are connected to
The difference is that S5 is always maintained at Ov.

The operation of the bias magnetic field generating device configured as described above will be explained below.

First, when performing an erase operation, the control unit 31 changes the voltage of the signal line SI a S5 to v at time t1 as shown in FIG.
Raise it to H. Switch 6.9 in FIG. 6 is then turned on, closing the circuit and passing current from high voltage source 12 to switch 6.
Excitation coil 1. Switch 9. The current flows through the erasing current source 6, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 begins to apply an erasing bias magnetic field to the magneto-optical recording medium. Voltage S
1. Immediately after S3 goes to vll and switch 6.9 turns on, signal S7 gradually starts to rise to 9, and S7 goes to Vr.
When ef is reached, the output S9 of the comparator 16 rises from 0 to vH.

Then, the control unit 31 sets Sl to vII and drops Sl to 0. At this time, the switch 6 and the switch 10 are switched, and the voltage source that drives the excitation coil 1 is momentarily switched from the high voltage source 12 to the low voltage source 13, but immediately after switching, S7 drops below Vref as shown in FIG. , the output S9 of the comparator 16 falls to 0 again, the driving voltage source of the exciting coil 1 is switched again to the high voltage source 12, and S7 starts to rise again. However, since S7 has not fallen to Ov at this time, the time it takes to rise to Vref is shorter than the first time, and from then on, the high voltage source 12 and low voltage source 13 show a more sawtooth waveform as shown in FIG. As the switching is repeated, the driving time with the high voltage source 12 gradually becomes shorter, and finally, at time t2, the driving voltage source of the excitation coil is switched to the low voltage source 13. After waiting until the bias magnetic field becomes large enough to perform an erasing operation, the optical head applies an erasing light spot to the magneto-optical recording medium to perform the erasing operation. When erasing is completed and time t3 arrives, the control unit 31 switches the signal line S2. Reduce the voltage of S3 to OV. Then, the switches 1o and 9 are turned off, the circuit is opened and the current is cut off, and the electromagnet composed of the excitation coil 1 and the magnetic core 2 stops outputting a magnetic field.

When performing the next recording operation, the control unit 3
1 raises the voltage of the signal line S4 e 86 to vH at time t4. Switches 8 and 7 in FIG. 6 are then turned on, closing the circuit, and current flows from high voltage source 12 to switch 8. Excitation coil 1. flowing through the switch 7 and the recording current source 4;
An electromagnet composed of an excitation coil 1 and a magnetic core 2 begins to apply a recording bias magnetic field to the magneto-optical recording medium. Voltage S4
# Immediately after S6 becomes vII and switches 8 and 7 are turned on, signal S8 starts to rise gradually and S8 reaches Vre.
When reaching f, the output 81G of the comparator 17 changes from 0 to vII
rise to Then, the control unit 31 sets S5 to vH, and sets S5 to vH.
Drop 4 to 0. At this time, the switch 8 and the switch 11 are switched, and the voltage source that drives the excitation coil 1 is the high voltage source 1.
There is a momentary switch from 2 to low voltage source 13, but immediately after the switch, 88 falls below Vre f, as shown in Figure 7.
The output Sho of the comparator 17 falls to 0 again and the excitation coil 1
The drive voltage source is switched again to the high voltage source 12, and S8 starts to rise again. However, at this time S7 has not fallen to Ov, so next Vref'! The rising time 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 a more sawtooth waveform as shown in FIG. 7, and the time of driving with the high voltage source 12 gradually increases becomes shorter, and finally, at time t5, the drive voltage source for the exciting coil is switched to the low voltage source 1.3. After waiting until the bias magnetic field becomes large enough to perform a recording operation, the optical head applies a light spot corresponding to the information to be recorded on the magneto-optical recording medium to perform the recording operation. When recording is completed and time t6 arrives, the control unit 31 switches the signal line S5
# Reduce the voltage of S6 to OV.

Then, the switches 11 and 7 are turned off, the circuit is opened and the current is cut off, and the electromagnet composed of the exciting coil 1 and the magnetic core 2 stops outputting a magnetic field.

This embodiment has the same effect as the first embodiment, but
Compared to the first embodiment, the differential amplifier can be completely eliminated, and the switching of the voltage source can be done in the first embodiment. The switching method does not suddenly switch to a low voltage source as in the second embodiment, but the probability of being driven by a high voltage source gradually decreases.
．． Compared to the second embodiment, the total driving time with the high voltage source is longer, and a bias magnetic field generating device with a shorter magnetic field rise time can be realized.

Effects of the Invention The present invention provides an electromagnet composed of an excitation coil that provides a bias magnetic field for recording and erasing on a magneto-optical recording medium, and a magnetic core around which the excitation coil is wound, and an electromagnet that applies a driving voltage to the electromagnet. a first voltage source, a second voltage source that applies a driving voltage lower than the first voltage source to the electromagnet, and switching means for switching between the first voltage source and the second voltage source; By having a voltage determination section that detects the voltage applied to the excitation coil and compares it with a reference voltage, and a control section that controls the voltage switching means based on a signal from the voltage determination section, the high voltage that is the first voltage source When the voltage of the excitation coil of the electromagnet started by the source becomes lower than the voltage of the low voltage source, which is the second voltage source, a signal is output from the comparator to the control unit, and the control unit changes the voltage source to the low voltage source. The voltage switching means switches the voltage source by outputting a switching signal to the voltage switching means. In other words, by switching the voltage of the drive circuit when the magnetic field is starting up and in other states, and using a high voltage source when the magnetic field is starting up, the 9 time it takes to start up the magnetic field can be shortened, and when the starting up is almost completed, the voltage of the drive circuit can be reduced by using a high voltage source. By using a power source, the power consumption of the entire circuit can be reduced. That is, improved efficiency is achieved without adversely affecting rise time.

Since the voltage of the high voltage source has little effect on power consumption, it is possible to prepare a power source with a sufficiently large voltage, and it is also possible to significantly shorten the rise time of the magnetic field. Furthermore, unnecessary power consumption can be reduced, and the temperature rise inside the magneto-optical recording and reproducing device can be minimized, allowing the optical head, which is relatively sensitive to temperature changes, to operate stably and improving the reliability of information. This makes it possible to realize a bias magnetic field generating device that can obtain a number of excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a bias magnetic field generating device in an embodiment of the present invention, FIG. 2 is a timing chart showing the signal states of various parts during erasing and recording of the bias magnetic field generating device of FIG. 1, FIG. 3 is a characteristic diagram showing changes in the voltage across the excitation coil and the voltage across the current source when the magnetic field rises in the bias magnetic field generator of FIG. 1, and FIG. 4 shows the bias in the second embodiment of the invention. A block diagram of the magnetic field generating device, FIG. 6 is a timing chart showing the signal states of each part during erasing and recording of the bias magnetic field generating device of FIG. 4, and FIG. 6 is a bias magnetic field in the third embodiment of the present invention. 7 is a block diagram of the bias magnetic field generator shown in FIG. 6; a timing chart showing the state of signals in each part during erasing and recording in the bias magnetic field generator shown in FIG. 6; FIG. 8 is a block diagram of the conventional bias magnetic field generator; Figure 9 is a timing chart showing the state of signals in each part of the bias magnetic field generator shown in Figure 8 during erasing and recording, and Figure 10 is the voltage across the excitation coil when the magnetic field of the bias magnetic field generator shown in Figure 8 rises. FIG. 3 is a characteristic diagram showing changes in the voltage across the current source and the voltage across the current source. 1...Excitation coil, 2...Magnetic core, 3,
30.31...control unit, 4...recording current source, 5...erasing current source, 6-11...
...Switch, 12...High voltage source, 13...
...Low voltage source, 14.15...Differential amplifier, 16.17...Comparator, 18...Reference voltage source, 19...・Positive reference voltage source, 2o...
...Negative electrode reference voltage source 0 Name of agent: Patent attorney Toshio Nakao and 1 other person 5.
-Taku Utazawa 18°゛° Reference temperature No. 2 Fig. 3 Fig. 5 (21 Fig. 6 ゑ 7121 No. 8 concave)

Claims (4)

[Claims] (1) An electromagnet consisting of an excitation coil that provides a bias magnetic field for recording and erasing on a magneto-optical recording medium and a magnetic core around which the excitation coil is wound, and a first voltage source that provides a driving voltage to the electromagnet. a second voltage source that applies a driving voltage to the electromagnet lower than that of the first voltage source;
a switching unit for switching between the voltage source and the second voltage source; a voltage determining unit that detects the voltage applied to the excitation coil and compares it with a reference voltage; and controlling the voltage switching unit by a signal from the voltage determining unit. A bias magnetic field generating device characterized by having a control section. (2) The voltage determination unit is configured to detect and amplify the potential difference between both ends of the excitation coil, compare the amplified voltage with a reference voltage output from the reference voltage source, and output the comparison result to the control unit. A bias magnetic field generating device according to claim 1, characterized in that: (3) A patent claim characterized in that the voltage determination unit is configured to compare at least one of the voltages across the excitation 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 item 1. (4) The voltage determination unit is the first
detects and amplifies the voltage applied to the excitation coil, and switches the voltage source for driving the excitation coil to a second voltage source when the amplified voltage becomes smaller than the voltage of the reference voltage source. 2. The bias magnetic field generating device according to claim 1, wherein the bias magnetic field generating device is configured to output a signal to a control section.