JPH08124235A - Disc temperature detection circuit for magnetooptic disc player - Google Patents

Abstract

PURPOSE: To detect the temperature of a disc accurately without requiring any detection member using a magnetic head touching the disc. CONSTITUTION: A signal appearing at the end A of a magnetic coil 1 is passed through an LPF 9 in order to remove the AC component and a DC voltage is fed through an amplifier circuit 10 and an AD conversion circuit 11 to a control circuit 14 where the DC voltage is detected as the temperature of a disc. In other words, resistance of the coil 1, and thereby the temperature of a magnetic head can be detected from the voltage at the end A. Since the magnetic head incorporating the coil 1 is touching the disc, the temperature of the magnetic head represents the temperature of the disc. A signal for producing a laser output appropriate for the detected temperature is delivered from the control circuit 14 through a laser drive circuit to a laser generator 12 which generates a laser corresponding to the temperature of the disc. Since the operation for recording a signal onto the disc is carried out with an optimal laser output, the signal recording operation can be carried out accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk player configured to record a signal on a disk by a laser emitted from an optical pickup and a magnetic change output from a disk contact type magnetic head.

[0002]

2. Description of the Related Art Recently, a device called a magneto-optical disc player, which can not only reproduce a signal recorded on a disc but also repeatedly record the signal on the disc, is becoming widespread.

Such a magneto-optical disc player raises the temperature of the surface of the recording film constituting the disc to a predetermined temperature by the laser emitted from the optical pickup, and changes the magnetism output from the disc contact type magnetic head. It is configured to record the signal on a disc.

[0004]

In a magneto-optical disc player configured to raise the temperature of the recording film surface constituting a disc to a predetermined temperature by a laser emitted from an optical pickup, a constant laser output is used. When recording is performed, the ambient temperature changes depending on the environment in which the disc player is used, so the temperature of the disc also changes according to the ambient temperature.
As a result, the characteristics of the signal recorded on the disc change depending on the temperature, which has a problem of affecting the recording / reproducing operation of the signal.

In order to solve such a problem, a technique has been developed in which the output of the laser is changed in response to the temperature change. However, since such a technique detects the temperature of the device, When a cold disk is used, the temperature rise may not reach a predetermined value, which may hinder the signal recording operation.

The present invention is intended to provide a disk temperature detecting circuit which solves such a problem.

[0007]

A temperature detecting circuit according to the present invention comprises a first field effect transistor having a drain connected to one terminal of a magnetic coil constituting a magnetic head and a source grounded. A second field effect transistor having a drain connected to the other terminal of the magnetic coil and a source grounded, and a data signal, which is a recording signal, is applied to the gate of the first field effect transistor and the second field effect. The first field effect transistor is turned on and the second field effect transistor is turned off when the level of the input signal is at the H level and the second field effect transistor is turned off.
And a signal input circuit for turning off the first field-effect transistor and turning on the second field-effect transistor when the level of the input signal is at the L level; and one terminal of the magnetic coil. It is composed of a low-pass filter for inputting a signal and converting the signal into a direct current.

[0008]

According to the present invention, the temperature of the disk is detected by utilizing the magnetic head which is in contact with the disk.

[0009]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, reference numeral 1 is a magnetic coil constituting a magnetic head that contacts the surface of the disk, and 2 and 3 are first and second auxiliary coils having a function of inverting the current supplied to the magnetic coil 1 at high speed. And one end thereof is commonly connected to each other and connected to the power supply V, and the other end thereof is connected to the end portions A and B of the magnetic coil 1, respectively.

Reference numeral 4 denotes a first field effect transistor having a drain connected to an end A which is a connection point between the magnetic coil 1 and the first auxiliary coil 2 and a source grounded. A second field-effect transistor which is connected to an end B which is a connection point between the magnetic coil 1 and the second auxiliary coil 3 and whose source is grounded. 6 is a data signal to which a pulsed data signal is input. An input terminal, 7 is a buffer amplifier circuit whose input terminal is connected to the data signal input terminal 6 and which outputs a signal at the same level as the level of the signal input to the input terminal. 1 is connected to the gate of the field effect transistor 4.

An input terminal 8 is the data signal input terminal 6
Is an inverter circuit that outputs a signal of a level that is the level of the signal that is connected to the input terminal and that is input to the input terminal, the output terminal of which is connected to the gate of the second field effect transistor 5.

Reference numeral 9 is a low-pass filter having an input terminal connected to the end A of the magnetic coil 1, that is, the drain of the first field effect transistor 4, and outputs a DC voltage with an AC component cut off to an output terminal. Is configured to. Reference numeral 10 is an amplifier circuit to which the DC voltage output from the low pass filter 9 is input and which amplifies the signal. Reference numeral 11 is an A / D conversion circuit for converting the DC voltage, which is the output signal of the amplifier circuit 10, into a digital signal according to its level. Reference numeral 12 denotes a laser generator that constitutes an optical pickup (not shown) and generates a laser. Reference numeral 13 denotes a laser drive circuit that drives the laser generator 12, which has a function of adjusting the laser output.

A control circuit 14 controls the operation of the laser drive circuit 13 based on the signal output from the A / D conversion circuit 11. The control operation of the laser drive circuit 13 causes the laser generator 12 to output the signal. It serves to adjust the output of the laser.

The present invention is constructed as described above,
Next, the operation of such a circuit will be described. When a recording operation switch (not shown) provided on the magneto-optical disc player is operated, the control circuit 14 causes each circuit and the like to perform a recording operation.

When the signal recording operation state is configured, a recording data signal is input to the data signal input terminal 6, so that a pulsed data signal is input to the buffer amplifier circuit 7 and the inverter circuit 8. Applied to the terminals.
When the level of the data signal is H (high) level, the output signal of the buffer amplification circuit 7 becomes H level and is applied to the gate of the first field effect transistor 4 and the output of the inverter circuit 8. The signal becomes L (low) level and is applied to the gate of the second field effect transistor 5. As a result, the first field effect transistor 4 becomes conductive and the second field effect transistor 5 becomes non-conductive. Therefore, in such a state, the recording current flows through the magnetic coil 1 from the end B side to the end A side.

On the contrary, when the level of the data signal is L level, the output signal of the buffer amplifying circuit 7 becomes L level and is applied to the gate of the first field effect transistor 4 and the inverter circuit 8 is provided. Output signal of H level is applied to the gate of the second field effect transistor 5. As a result, the first field effect transistor 4 becomes non-conductive and the second field effect transistor 5 becomes conductive. Therefore,
In such a state, the magnetic coil 1 has the end portion B from the end portion A side.
The recording current will flow to the side.

As described above, when the pulsed data signal is input, the first field effect transistor 4 and the second field effect transistor 5 alternately repeat the conducting operation and the non-conducting operation. From 1, a magnetic field for recording is generated. Then, in such a state, a laser is generated from the laser generator 12 by the driving operation of the laser driving circuit 13 and the recording track of the disc is irradiated with the laser, so that the temperature of the recording film surface of the disc becomes a predetermined temperature. Can be raised. As a result of such operation, a data signal, for example, a music signal can be recorded on the disc.

As described above, the signal recording operation according to the present invention is performed. Next, the temperature detecting operation will be described.
Such detection operation is performed in the state where the above-described signal recording operation is being performed.

The first field effect transistor 4 and the second field effect transistor 5 have a characteristic that the resistance value between the drain and the source in the conductive state is 0.1Ω to 0.2Ω. . Therefore, the resistance value of the magnetic coil 1 can be detected by detecting the voltage value obtained by dividing the resistance value of the first field effect transistor 4 and the resistance value of the magnetic coil 1.

Here, the resistance value of the magnetic coil 1 is 1
It has a positive temperature coefficient of about 0.4% per ℃, 25 ℃
When the resistance value at 1.1 is 1.1Ω, the resistance value at 50 ° C. is 1.1 + 1.1 × (50−25) × 0.004 =
1.21Ω, and the resistance value at 0 ° C is 1.1+
It becomes 1.1 * (0-25) * 0.004 = 0.99 (ohm). Therefore, the resistance value of the magnetic coil 1 changes from 0.99Ω to 1.21Ω when the temperature changes from 0 ° C. to 50 ° C., and thus the change resistance value becomes 0.22Ω.

Therefore, by detecting the voltage at the end A of the magnetic coil 1, the resistance value of the magnetic coil 1, that is, the temperature can be detected. And the magnetic coil 1
Since the magnetic head incorporating the is in contact with the disk, the temperature of the magnetic head becomes the temperature of the disk,
As a result, the temperature of the disc can be detected.

The signal appearing at the end A of the magnetic coil 1 is input to the low pass filter 9 and its AC component is cut off. As a result, a DC voltage with the AC component removed is output to the output terminal of the low-pass filter 9, and the DC voltage is input to the amplifier circuit 10 and amplified. Since the DC voltage output from the amplifier circuit 10 is input to the A / D conversion circuit 11, the digital signal corresponding to the value of the DC voltage input to the A / D conversion circuit 11 is A / D.
It is output from the conversion circuit 11 and input to the control circuit 14. Therefore, the temperature of the disk is detected by the control circuit 14.

When the temperature of the disk is detected by the control circuit 14, a control signal is output to the laser drive circuit 13 in order to obtain the laser output suitable for the detected temperature. When such a signal is output from the control circuit 14 to the laser drive circuit 13, the drive control operation for the laser generator 12 is performed by the laser drive circuit 13, so that the laser generator 12 changes the temperature of the disk. A laser of corresponding output will be generated. Therefore, the signal recording operation on the disk can be performed with the optimum laser output, and the signal recording operation can be performed accurately.

In this embodiment, the end portion A of the magnetic coil 1 is
Although a signal for detection is obtained more, it is of course possible to obtain a detection signal from the opposite end B.

In this embodiment, the drain of the field effect transistor is connected to the terminal of the magnetic coil 1 and the source is grounded. On the contrary, the source of the field effect transistor is connected to the terminal of the magnetic coil 1. Can be connected and the drain can be grounded.

[0026]

According to the present invention, the temperature of the disk is detected instead of the temperature of the magneto-optical disk player, so that the signal recording operation can be performed accurately. Also,
Since the temperature of the disk is detected using the magnetic head that contacts the disk, not only can accurate detection be performed, but a special detection member is not required, which simplifies the configuration. The present invention has

Further, according to the present invention, since the temperature of the disk can be detected while the data signal is being recorded, the temperature of the disk in the recording state is detected and the laser output is optimized. It can be adjusted, and therefore the signal recording operation can always be performed with the optimum laser output.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a disk temperature detection circuit of the present invention.

[Explanation of symbols]

 1 Magnetic Coil 4 First Field Effect Transistor 5 Second Field Effect Transistor 6 Data Signal Input Terminal 9 Low Pass Filter 10 Amplification Circuit 11 A / D Conversion Circuit 12 Laser Generator 13 Laser Drive Circuit 14 Control Circuit

Claims (2)

[Claims] 1. A magneto-optical disk player configured to record a signal on a disk by a laser emitted from an optical pickup and a magnetic change output from a disk contact type magnetic head. A first field effect transistor having a drain and a source connected between one terminal of the coil and the ground, and a second field effect transistor having a drain and the source connected between the other terminal of the magnetic coil and the ground. -Type transistor and a data signal, which is a recording signal, are guided to the gates of the first field-effect transistor and the gate of the second field-effect transistor, and the first field-effect transistor is turned on when the level of the input signal is H level. The second field effect transistor is turned off and the input signal is turned on. A signal obtained from one terminal of the magnetic coil and a signal input circuit that makes the first field-effect transistor non-conductive and the second field-effect transistor conductive when the level of L is L level. A disk temperature detecting circuit for a magneto-optical disk player, comprising: a low-pass filter for converting the signal into a direct current, and detecting the temperature of the disk based on a direct-current voltage obtained from the low-pass filter. 2. The disk temperature detecting circuit according to claim 1, wherein the output of the laser emitted from the optical pickup is set based on the detected temperature of the disk.