JPH06150207A - Coil drive circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable driving by a high-frequency signal and suppress unnecessary power consumption. [Configuration] When driving the coil 10 with a signal of a relatively low frequency, the switches 31 and 32 are turned off, and the auxiliary coil 3
Do not use 5,36. When driving the coil 10 at a relatively high frequency, the switches 2 and 3 are turned off, the switches 31 and 32 are turned on, and the auxiliary coils 35 and 36 are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil drive circuit suitable for driving a magnetic head of a magneto-optical disk device, for example.

[0002]

2. Description of the Related Art FIG. 6 shows the principle of recording on a magneto-optical disk. Magneto-optical disk 25 having recording layer 26
Are rotated by a spindle motor 24. An optical head 23 is arranged on the upper surface of the magneto-optical disk 25 so that the recording layer 26 of the magneto-optical disk 25 is irradiated with laser light emitted from a built-in laser diode or the like. On the other hand, a magnetic head 22 is arranged on the lower surface of the magneto-optical disk 25, and is driven by the drive circuit 21 corresponding to the recording data to apply a magnetic field corresponding to the recording data to the recording layer 26.

When the laser light emitted from the optical head 23 is irradiated, the temperature of the recording layer 26 rises above the Curie point temperature in the range where the laser light is irradiated, and the recording layer 26 is irradiated.
The magnetic field recorded in is erased. And the recording layer 2
When 6 cools below the Curie point temperature, the direction of its magnetic field corresponds to the direction of the magnetic field applied by the magnetic head 22. Therefore, by changing the direction of the magnetic field applied by the magnetic head 22 in accordance with the recording data, it is possible to record digital data of logic 1 or logic 0 on the recording layer 26.

FIG. 7 shows a conventional configuration example of the drive circuit 21. In this example, the magnetic head 22 is composed of the coil 10 and the capacitor 11 connected in parallel to the coil 10. The magnetic head 22 includes switches 2 to 5 and a diode 6
9 to 9 is connected to the middle point of the bridge circuit. That is, each side of the bridge circuit has a switch 2 and a diode 6, a switch 3 and a diode 7, and a diode 8
And the switch 4, the diode 9 and the switch 5, respectively, and the magnetic head 22 is connected between the connection points of the diodes 6 and 8 and the diodes 7 and 9. One end of each of the switches 2 and 3 has a predetermined voltage source V
_It is connected to ₁ , and one ends of switches 4 and 5 are grounded. The control circuit 1 corresponds to the input recording data,
The switches 2 to 5 are driven.

Next, the operation will be described with reference to the timing chart of FIG. When a magnetic field of N pole, for example, is applied to the recording layer 26 by the magnetic head 22, a current + is applied to the coil 10 from left to right in FIG.
I will be washed away. At this time, the control circuit 1 uses the clock (see FIG.
The switches 2 and 5 are turned on in synchronization with (d) (see FIG. 8).
(B)), switches 3 and 4 are turned off (FIG. 8)
(C)). As a result, a current + I is generated in the path of the switch 2, the diode 6, the coil 10, the diode 9, and the switch 5.
Flows (FIG. 8A).

On the other hand, when the magnetic head 22 generates an S-pole magnetic field, the coil 10 is supplied with a current of -I flowing to the left in FIG. At this time, the control circuit 1 turns on the switches 3 and 4 (FIG. 8C), and switches 2 and 5
Is turned off (FIG. 8 (d)). As a result, the switch 3,
Diode 7, coil 10, diode 8, switch 4
An electric current flows through the route (Fig. 8 (a)).

By the way, the recording layer 26 is formed by the coil 10.
To apply a magnetic field of sufficient strength to the coil 10,
It is preferable to make the value of the inductance of (1) as large as possible. However, if the inductance of the coil 10 is increased, the counter electromotive force is also increased, and the switch 2
It becomes difficult to switch the direction of the current supplied to the coil 10 at high speed by switching the switches 5 to 5. That is, a high frequency signal is recorded (switches 2 to 5).
In order to switch at high speed), the inductance of the coil 10 should be small. However, as described above, if the inductance of the coil 10 is reduced, it becomes impossible to generate a magnetic field of sufficient strength.

Therefore, the present applicant has filed Japanese Patent Application No. 4-22753.
As No. 9, a drive circuit as shown in FIG. 9 was previously proposed.

In this proposal, a constant current source circuit 15 and an auxiliary coil 17 are inserted between the switch 2 and the coil 10, and similarly, a constant current source circuit 16 and a constant current source circuit 16 are inserted between the switch 3 and the coil 10. The auxiliary coil 18 is inserted.

As described above, by inserting the auxiliary coils 17 and 18, at the timing of switching the direction of the current flowing through the coil 10, the energy accumulated in the auxiliary coils 17 and 18 is utilized to cause the current flowing through the coil 10 to flow. The direction of can be switched quickly.

[0011]

However, in the case of the configuration shown in FIG. 9, there is a problem that power consumption increases.

The present invention has been made in view of the above circumstances, and it is possible to reverse a magnetic field at high speed and to reduce power consumption as much as possible.

[0013]

A coil drive circuit according to the present invention comprises a coil 10 for generating a magnetic field and a switch 2 as a bridge-connected first to fourth switching element for switching to drive the coil 10. Through 5,
First auxiliary coil 35 connected in parallel with the switch 2
And a second auxiliary coil 3 connected in parallel with the switch 3.
6, a switch 31 as a first auxiliary switching element that switches to turn on or off the first auxiliary coil 35, and a second auxiliary switching that switches to turn on or off the second auxiliary coil 36. When the switch 32 as an element and the coil 10 are driven with a signal having a relatively low frequency, the coil 10 is driven using the switches 2 to 5, and when the coil 10 is driven with a signal having a relatively high frequency, the switch 4 is used. And switch 5
In addition, the switch 2 to 5 and the control circuit 1 for driving the switches 31 and 32 are provided so as to drive the coil 10 using the first auxiliary coil 35 and the second auxiliary coil 36. .

Between the coil 10 and the first auxiliary coil 35,
Between the coil 10 and the second auxiliary coil 36, diodes 37, 38 as a separating circuit for separating them are provided.
Can be inserted.

[0015]

In the coil drive circuit having the above-described structure, the switches 2 to 5 are used when driving with a relatively low frequency signal, and the switches 4 and 5 and the auxiliary coil 35 are used when driving with a relatively high frequency signal. , 36 are used. As a result, high speed inversion of the drive current in the coil 10 is allowed, and when the frequency is relatively low, the auxiliary coils 35 and 36 are not used, and wasteful power consumption is suppressed. be able to.

[0016]

1 is a circuit diagram showing the configuration of an embodiment of a coil drive circuit of the present invention, in which parts corresponding to those in the conventional case shown in FIG. The description thereof will be repeated and will be appropriately omitted. In this embodiment,
A series circuit of the switch 31, the constant current source circuit 33, the auxiliary coil 35, and the diode 37 is connected in parallel to the series circuit of the switch 2 and the diode 6. Also,
The series circuit of the switch 32, the constant current source circuit 34, the auxiliary coil 36, and the diode 38 is connected in parallel to the series circuit of the switch 3 and the diode 7. Then, the switches 31 and 32 are similar to the switches 2 to 5,
Switching is controlled by the control circuit 1. A circuit switching signal for switching the operating state of the drive circuit 21 is supplied to the control circuit 1 from a circuit (not shown). Other configurations are the same as those in FIG. 7.

Next, the operation will be described with reference to the timing charts of FIGS. Control circuit 1
Turns off the switches 31 and 32 when the circuit switching signal is a signal (low-frequency mode signal) indicating that the frequency of the recording data is relatively low (FIG. 2).
(D)). Then, the input recording data (see FIG.
In response to (e)), the switches 2 to 5 are turned on or off. That is, when the logic 0 is input as the recording data, the control circuit 1 turns on the switches 3 and 4 (see FIG. 2).
(C)), and switches 2 and 5 are turned off (FIG. 2 (b)).
As a result, the switch 3, the diode 7, the coil 10,
A current -I flows through the path of the diode 8 and the switch 4 (Fig. 2 (a)).

On the other hand, when a logic 1 is input,
The control circuit 1 turns on the switches 2 and 5 (FIG. 2B),
The switches 3 and 4 are turned off (FIG. 2 (c)). As a result, the current + I flows through the path of the switch 2, the diode 6, the coil 10, the diode 9, and the switch 5 (see FIG. 2).
(A)).

That is, the above operation is similar to that in the example of FIG.

On the other hand, the control circuit 1 turns off the switches 2 and 3 when a circuit switching signal (high frequency mode signal) indicating that the input recording data is a signal of a relatively high frequency is input. (FIG. 3B), switches 31 and 3
2 is turned on (FIG. 3 (c)). And the control circuit 1
The switches 4 and 5 are turned on or off according to the input recording data.

For example, when the recording data (FIG. 3 (f)) is logic 0, the control circuit 1 turns on the switch 4 (FIG. 3).
(E)), and the switch 5 is turned off (FIG. 3 (d)). Thereby, the switch 32, the constant current source circuit 34, the auxiliary coil 36, the diode 38, the coil 10, the diode 8,
The current −I flows through the path of the switch 4 (FIG. 3A).

On the other hand, recording data (FIG. 3 (f))
Is logic 1, the control circuit 1 turns on the switch 5 (FIG. 3D) and turns off the switch 4 (FIG. 3).
(E)). As a result, the switch 31, the constant current source circuit 3
A current + I flows through the path of 3, the auxiliary coil 35, the diode 37, the coil 10, the diode 9, and the switch 5 (FIG. 3A).

Now, the switch 32, the constant current source circuit 34,
Assuming that the current −I is flowing in the path of the auxiliary coil 36, the diode 38, the coil 10, the diode 8, and the switch 4, at this time, the switch 31, the constant current source circuit 33, the auxiliary coil 35, the diode 37, the diode 8, The constant current output from the constant current source circuit 33 also flows through the auxiliary coil 35 in the path of the switch 4.

In this state, when the switch 4 that is currently on is turned off and the switch 5 that is currently off is turned on to switch the direction of the current flowing through the coil 10, the coil 10 and the capacitor 11 resonate, and 10
Generates a counter electromotive force to hold the current -I.
Therefore, the potential at the connection point between the diode 6 and the diode 8 becomes high potential. However, the auxiliary coil 35 is connected to the connection point between the diode 6 and the diode 8 via the diode 37. The value of the inductance of the auxiliary coil 35 is set to a value sufficiently larger than the value of the inductance of the coil 10. As a result, a current is supplied from the auxiliary coil 35 against the counter electromotive force generated by the coil 10, and the direction of the current flowing through the coil 10 is quickly switched.

This means that the switch 31, the constant current source circuit 33, the auxiliary coil 35, the diode 37, the coil 10,
+ Current to coil 10 via diode 9 and switch 5
The same applies when the switch 5 is switched from on to off and the switch 4 is switched from off to on in the state where I is flowing. That is, also in this case, since the auxiliary coil 36 is connected to the connection point between the diodes 7 and 9 via the diode 38, the current supplied from the auxiliary coil 36 becomes the counter electromotive force generated in the coil 10. The direction of the current flowing through the coil 10 is rapidly switched against.

As described above, the coil 10 can be driven at high speed.

The diode 37 or 38 is provided to separate the auxiliary coil 35 or 36 from the coil 10, respectively. When the diodes 37 and 38 are not provided, the auxiliary coil 35 or the auxiliary coil 36 is connected to the coil 10 in series. As a result, the auxiliary coil 35 or 36 is added to the resonance phenomenon that occurs between the coil 10 and the capacitor 11 when the current direction is switched, and the resonance frequency becomes smaller. In other words, the resonance cycle becomes long, and quick switching becomes difficult (switching from the current -I to + I or vice versa is performed in about 1/2 time of this resonance cycle). Therefore, as in the embodiment, it is preferable to provide diodes 37 and 38 for separating the auxiliary coil 35 or 36 from the coil 10 when the coil 10 performs the resonance operation.

The coil 1 is switched between driving the driving circuit 21 in the low frequency mode and the high frequency mode.
When the values of 0 and the inductance and the capacitance of the capacitor 11 are L and C, respectively, the resonance frequency f (= 1 / (2π (LC) ^1/2 )) can be used as a reference. That is, when the frequency of the recorded data is higher than this resonance frequency, the operation is performed in the high frequency mode, and when it is lower than this resonance frequency, the operation is performed in the low frequency mode.

When operating in the high frequency mode, the current output from the auxiliary coil 35 is applied to the coil 10 as described above.
The current output from the auxiliary coil 36 also flows through the path of the diode 9 and the switch 5 even in the state of being supplied to the. Similarly, while the current supplied from the auxiliary coil 36 is flowing through the coil 10, the auxiliary coil 3
The current output from 5 flows through the path of the diode 8 and the switch 4. Therefore, power is consumed more than necessary. However, in low frequency mode,
Since the auxiliary coils 35 and 36 are not used, such useless power is not consumed.

In the above embodiment, the switches 31,
Although the switch 32 is always turned on in the high frequency mode, the switch 31 or 32 may be turned on immediately before switching the direction of the current supplied to the coil 10.

That is, in this case, as shown in the timing chart of FIG. 4, the switch 5 is turned on, the switch 4 is turned off (FIGS. 4 (d) and (e)), and the switch 32 is turned off (see FIG. 4). 4 (c)), when the current flowing through the coil 10 is switched from −I to + I (FIG. 4 (a)), the switch 4 is turned off, the switch 5 is turned on, and the switch 32 is turned off at time t ₂ ( The switch 31 is turned on at a time t ₁ slightly before (c), (d) and (e) in FIG.
(B)).

With this arrangement, at the time before time t ₁ , the switch 31 is turned off, so that the auxiliary coil 35 is not supplied with current and the wasteful consumption of power is suppressed. To be done. Then, since the switch 31 is turned on at the timing when the switch 4 is turned on between the time t ₁ and the time t ₂ , the switch 31,
Constant current source circuit 33, auxiliary coil 35, diode 37,
A current flows through the path of the diode 8 and the switch 4. Therefore, at time t ₂ , the switch 5 is turned on (see FIG.
(D)), the switch 4 is turned off (FIG. 4 (e)), the switch 32 is turned off (FIG. 4 (c)), and the current flowing in the coil 10 (FIG. 4 (a)) is switched from -I to + I. At this time, since a current (FIG. 4 (f)) is flowing in the auxiliary coil 35,
The switching is performed quickly.

Similarly, at time t ₄ , the switch 5 is turned off (FIG. 4 (d)) and the switch 4 is turned on (FIG. 4 (d)).
(E)), when the switch is turned off 31 (FIG. 4 (b)), in some previous time t ₃ to time t _4, switch 3
When turned on 2 (FIG. 4 (c)), in the period of time t ₄ from time t _3, switch 32, constant current source circuit 34, the auxiliary coil 36, the diode 38, the diode 9, the current in the path of the switch 5 (Fig. 4 (g)) flows, and the operation of switching the current (FIG. 4 (a)) of the coil 10 from + I to −I is quickly performed.

In the embodiment of FIG. 4, the switches 2,
3 is always turned off (FIG. 4 (h)) means that FIG.
It is similar to the case in.

FIG. 5 shows another embodiment of the coil drive circuit of the present invention. In this embodiment, the diodes 8 and 9 in the embodiment of FIG. 1 are omitted. Other configurations are similar to those in FIG.

In the case of the configuration of the embodiment of FIG. 5,
Since the back electromotive force generated by the coil 10 must be borne by the diodes 6 and 7, its withstand voltage is shown in FIG.
It is necessary to make the size larger than that in the above embodiment. Figure 1
In this embodiment, since the back electromotive force generated by the coil 10 is borne by the diodes 6 and 8 or the diodes 7 and 9, its withstand voltage is 1/2 of that in the embodiment of FIG. Good. However, when the breakdown voltages of the diodes 6 and 7 are large, the diodes 8 and 9 can be omitted and the number of components can be reduced.

The switching of the frequency of the recording data is performed, for example, when the data is recorded on a disc called a so-called zone CAV system. In this case, the clock frequency in the outer peripheral region is switched to a higher frequency than the clock frequency up to a predetermined radial position.

Alternatively, the present invention can be applied to a case where different clocks are used for each disk.

[0039]

As described above, according to the coil drive circuit of the first aspect, the first auxiliary coil and the second auxiliary coil are used only when driven by a signal having a relatively high frequency. When driving with a relatively low frequency signal, the first auxiliary coil and the second auxiliary coil are not used. Therefore, when driving with a high frequency signal, high-speed response is possible and low When driving with a frequency signal, it is possible to suppress unnecessary power consumption.

According to the coil drive circuit of the second aspect, since the separation circuit for separating the coil and the auxiliary coil is inserted between the coil and the auxiliary coil, it is difficult to drive with a signal having a relatively high frequency. Is prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of a coil drive circuit of the present invention.

FIG. 2 is a timing chart explaining the operation in the low frequency mode of the embodiment of FIG.

FIG. 3 is a timing chart explaining the operation in the high frequency mode of the embodiment of FIG.

FIG. 4 is a timing chart for explaining another operation in the high frequency mode of the embodiment of FIG.

FIG. 5 is a circuit diagram showing a configuration of another embodiment of the coil drive circuit of the present invention.

FIG. 6 is a diagram illustrating a recording principle of a magneto-optical disk device.

FIG. 7 is a circuit diagram showing a configuration example of a conventional coil drive circuit.

FIG. 8 is a timing chart illustrating the operation of the example of FIG.

FIG. 9 is a circuit diagram showing a configuration of another example of a conventional coil drive circuit.

[Explanation of symbols]

 1 Control Circuit 2 to 5 Switch 6 to 9 Diode 10 Coil 11 Capacitor 21 Drive Circuit 22 Magnetic Head 23 Optical Head 25 Magneto-Optical Disk 31,32 Switch 33,34 Constant Current Source Circuit 35,36 Auxiliary Coil 37,38 Diode

Claims (2)

[Claims] 1. A coil for generating a magnetic field, first to fourth switching elements connected in bridge for switching to drive the coil, and a first element connected in parallel with the first switching element. An auxiliary coil, a second auxiliary coil connected in parallel with the second switching element, a first auxiliary switching element that switches to turn on or off the first auxiliary coil, and the second A second auxiliary switching element that switches to turn the auxiliary coil on or off; and when driving the coil with a signal of a relatively low frequency,
When the coil is driven by using the first to fourth switching elements and the coil is driven by a signal having a relatively high frequency, the first switching element and the fourth switching element together with the first switching element are used. To drive the coil using an auxiliary coil and a second auxiliary coil,
A coil drive circuit comprising: the first to fourth switching elements; and a control circuit for driving the first and second auxiliary switching elements. 2. A separation circuit for separating the coils from the first auxiliary coil and between the coil and the second auxiliary coil are inserted. 1. The coil drive circuit according to 1.