JP2865077B2 - LD drive circuit for magneto-optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LD driving circuit for a magneto-optical recording / reproducing apparatus, and more particularly to an LD driving circuit for a magneto-optical recording / reproducing apparatus for switching the amount of light emitted from an LD (laser diode) during recording and reproduction.

[0002]

2. Description of the Related Art Conventionally, this type of magneto-optical recording / reproducing
The D drive circuit has, for example, the configuration shown in FIG.

In FIG. 3, the amount of light emitted from an LD 21 is monitored by a photodiode 22, and this output current is converted into a voltage signal by a current-to-voltage conversion circuit 23. The voltage signal is input to an operational amplifier 24 and is supplied to a reference voltage source. Compared to 25,
The difference voltage is amplified and output as the control voltage 201. At the time of reproduction, since the switch 29 selects the control signal 201, the control voltage 201 is applied to the LD drive current generation circuit 30. The LD drive current generation circuit 30 outputs the drive current controlled by the control voltage 201 to LD2
1 That is, the drive current is stabilized against temperature fluctuations and the like by the above-described APC (Auto Power Control).

In recording, the switch 29 selects the control voltage 202.
The memory 26 stores the control voltage 201 at this time in an analog manner by the ground signal sent from the memory 26. The output voltage of the memory 26 is divided and attenuated by the voltage attenuator 28 to become a control signal 202. The control voltage 202 is applied to the LD drive current generation circuit 30 to reduce the drive current to the LD to the bias current for recording.

[0005] Generally, the amount of bias light during recording is less than the amount of light emitted during reproduction. Since the control voltage 202 varies depending on the temperature or the like, the memory 26 holds the bias voltage at the time of recording immediately before recording, that is, the control voltage 201 at the end of reproduction.
During recording, the signal current is added to the bias current,
Is emitted to irradiate the medium, so that the amount of LD light emission at the time of recording exceeds that at the time of reproduction when there is a signal current.

[0006]

As described above, according to the conventional example, the control voltage 202 selected at the time of recording is obtained by dividing the output voltage of the memory 26 (that is, the control voltage 201) by the attenuator 28. When the output voltage at the time of storage of the memory changes due to temperature fluctuation, there is a problem that the bias light slightly changes for the following reason.

That is, FIG. 2 shows the relationship between the light emission amount of the LD and the drive current at each temperature. It can be seen that when the drive current increases, the light emission amount sharply increases from a certain point in time. At this time, the ratio of the driving current to the light emission amount after the light emission amount sharply increases is almost constant with little difference due to the temperature.
Considering the characteristics of the LD of FIG. 2, when an attenuator is used, bias light is obtained at the time of adjustment. However, since the attenuator based on the partial pressure has a proportional output with respect to the input, for example, in FIG.
It is assumed that the current value of the bias light emission amount during recording is I1. Similarly, the current at 25 ° C. is changed to I4, I3, 50 °
In the case of C, they are I6 and I5. The attenuation ratio of the attenuator is a constant partial pressure ratio, whereas I1 / I2 ≠ I3 / I4 ≠ I5 / I6
(I1−I2 = I3−I4 = I5−I6 = constant value), there is a problem that the bias light switch at the time of recording changes with temperature.

[0008]

An LD drive circuit of a magneto-optical recording / reproducing apparatus according to the present invention comprises: a drive current generation circuit for generating a drive current supplied to an LD by varying the control voltage; A photodiode to be monitored, an operational amplifier circuit that converts an output current of the photodiode into a voltage, amplifies a difference voltage from a reference voltage, and outputs the amplified voltage as a first control voltage, and a switch signal that receives the first control voltage, , A memory for recording the value at the time of input, a voltage attenuating circuit for attenuating the output voltage of this memory and outputting it as a second control voltage, and the first mode when the operation mode of the magneto-optical recording / reproducing apparatus is reproduction. Select the second control voltage during recording, apply the second control voltage to the drive current generating circuit as the control voltage, and simultaneously output the switch signal when selecting the second control voltage. An LD drive circuit of a magneto-optical recording / reproducing apparatus including a switch circuit, wherein the voltage attenuating circuit includes a voltage source that generates a constant voltage, and a subtractor that subtracts the constant voltage from an output voltage of the memory. Have.

Further, the voltage source may be capable of changing a voltage value.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment.

In FIG. 1, the light emission amount of the LD 1 is monitored by a photodiode 2, and the output current is converted into a voltage signal by a current-voltage conversion circuit 3, and the voltage signal is input to an operational amplifier 4 and supplied to a reference voltage source. 5, and the difference voltage is amplified and output as the control voltage 101. During playback,
Since the switch 9 has selected the control signal 101, the LD 9
The control voltage 101 is applied to the drive current generation circuit 10. The LD drive current generation circuit 10 controls the control voltage 1
01 is supplied to the LD 1. That is, this drive current is supplied to the APC (Au
To Power Control), it is stabilized against temperature fluctuations and the like.

During recording, the switch 9 is set to the control voltage 1
02 is selected, and the memory 6 stores the control voltage 101 at this time in an analog manner by the ground signal sent from the switch 29 at the same time as the selection. The output voltage of the memory 6 is attenuated by subtracting a voltage of a constant value by a voltage attenuating circuit 8 to become a control signal 102. The control voltage 102 is applied to the LD drive current generation circuit 10 to reduce the drive current to the LD to a bias current for recording.

The voltage attenuating circuit 8 comprises a voltage source 82 for generating a constant voltage and a subtractor 81 for subtracting the constant voltage from the output voltage of the memory 6. Control voltage 102 for obtaining bias light
Output at a constant value until The voltage source 82 can be changed to obtain a predetermined bias light.

Generally, the amount of bias light during recording is less than the amount of light emitted during reproduction. Since the control voltage 101 fluctuates depending on the temperature or the like, the memory 26 holds the control voltage 201 at the time of recording immediately before recording, that is, at the end of reproduction.
During recording, the signal current is added to the bias current,
Is emitted to irradiate the medium, so that the amount of LD light emission at the time of recording exceeds that at the time of reproduction when there is a signal current.

[0016]

As described above, the LD drive circuit of the magneto-optical recording / reproducing apparatus of the present invention obtains the control voltage for determining the bias light at the time of recording by subtracting a constant value instead of dividing the voltage. Therefore, there is an effect that an optimum recording light waveform which is not affected by temperature during recording can be maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating a relationship between a light emission amount of an LD and a drive current.

FIG. 3 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 LD (laser diode) 2 photodiode 3 current-voltage conversion circuit 4 operational amplifier 5 reference voltage source 6 memory 8 voltage attenuation circuit 9 switch 10 LD drive current generation circuit

Claims (2)

(57) [Claims] 1. A drive current generating circuit that varies a drive current supplied to an LD by a control voltage to generate a drive current, a photodiode that monitors a light emission amount of the LD, and converts an output current of the photodiode into a voltage to generate a reference voltage. An operational amplifier circuit for amplifying a difference voltage from the voltage and outputting the amplified voltage as a first control voltage;
A memory for recording the value at the time when the first control voltage is input and the switch signal is input, a voltage attenuating circuit for attenuating the output voltage of the memory and outputting it as a second control voltage;
When the operation mode of the magneto-optical recording / reproducing apparatus is reproduction, the first
And a switch circuit that outputs the switch signal when the second control voltage is selected and at the same time selects the second control voltage and applies the same to the drive current generation circuit as the control voltage during recording. In the LD drive circuit of the magneto-optical recording / reproducing apparatus provided, the voltage attenuating circuit includes a voltage source that generates a constant voltage, and a subtractor that subtracts the constant voltage from an output voltage of the memory. LD driving circuit of the magneto-optical recording and reproducing apparatus. 2. The LD driving circuit according to claim 1, wherein said voltage source is capable of changing a voltage value.