KR20020062959A - Current generating circuit and method - Google Patents

Abstract

The laser driving circuit for generating a level driving current corresponding to three or more kinds of laser powers has first to third signal generating circuits (110, 120, and 130) and a signal combining circuit (140). The first signal generating circuit 110 detects the output level of the current semiconductor laser 50 by referring to the light receiving signal Vp detected by the light receiving element 51 and outputs a first driving current Ib. The second signal generating circuit 120 generates a difference current Ibe that is smaller than the second driving current corresponding to the erase power by the first driving current. The third signal generating circuit 130 generates a proportional current Ibw obtained by multiplying the differential current to the differential current Ibe. This magnification is defined by (write power-bias power) (erase power-bias power). The signal synthesizing circuit 140 generates the drive current Id of the semiconductor laser 50 by combining the currents Ib, Ibeb and Ibw in accordance with the operation mode.

Description

[0001] Current generating circuit and method [0002]

The laser drive circuit is exemplified as the current generation circuit.

Various optical disc apparatuses have been known. However, many general optical disc apparatuses have a recording function for recording data on an optical disc, an erasing function for erasing data recorded on the optical disc, and a reproducing function for reproducing data recorded on the optical disc .

The optical disc apparatus generally records, reproduces, or erases data by irradiating the optical disc with a laser beam using one semiconductor laser. Generally, laser power (output level of laser) during recording, during reproduction and during erasing are different from each other. The laser power at the time of recording is higher than the laser power at the time of erasure, and the laser power at the time of erasure is higher than the laser power at the time of erasure.

1A and 1B are waveform diagrams illustrating waveforms of data write pulses of a semiconductor laser when data is recorded by irradiating a phase change type optical disc with a laser beam from a semiconductor laser in an optical disc apparatus, Twd) indicates the data length of the recording data.

Fig. 1B is a waveform diagram showing the waveform (or intensity) of the laser light corresponding to the recording data shown in Fig. 1A.

In the write data pulse at the time of recording shown in Figs. 1A and 1B, the minimum cycle of the write pulse is T. The width (T _WD ) of the write data pulse shown in FIG. 1A is 8T and 3T. 1B, the minimum pulse width in the minimum period T is T _mp = 0.4 × T, the maximum pulse width is T _top = 0.5 × T, the pulse is reset (cleared) to the bias power Pb after writing, The width is T _c1 = 0.6 x T.

The laser power (laser output level) at the time of recording shown in Fig. 1B has three levels. That is, there are three kinds of the bias power level Pb as the first level, the erase power level Pe as the second level, and the write power level Pw as the third level. 0 < Pb < Pe < Pw.

2 is a block diagram illustrating a laser driving circuit in an optical disc apparatus.

2, the illustrated laser drive circuit 90 has first to third signal generating circuits 10, 20 and 30 and a signal synthesizing circuit 40. [

The laser drive circuit 90 is connected to the optical disc apparatus in cooperation with the semiconductor laser 50, the light receiving element 51, the current / voltage conversion circuit (I / V) 52 and the control means 60 The semiconductor laser 50 emits laser light for reading data, erasing data, and writing data. In other words, the optical disc apparatus has a semiconductor laser 50, a light receiving element 51, a current / voltage conversion circuit 52, a control means 60 and a laser drive circuit 90.

The first signal generating circuit 10 includes a sample-and-hold circuit (SHb) 11 and an addition (subtraction) circuit 12 for calculating an error, a loop filter (LPb) 13, a voltage / And a target value setting circuit (SETb) 15 for applying a target value (reference value) to the addition circuit 12.

The second signal generating circuit 20 includes a sample / hold circuit (SHe) 21, an addition (subtraction) circuit 22 for calculating a deviation, a loop filter (LPe) 23, (V / Ie) 24 and a target value setting circuit (SETe) 25 for applying a target value (reference value) to the addition circuit 22.

The third signal generating circuit 20 includes a sample hold circuit (SHw) 31, an adder (subtraction) circuit 32 for calculating a deviation, a loop filter (LPw) 33, (V / Iw) 34 and a target value setting circuit (SETw) 35 for applying a target value (reference value) to the addition circuit 22.

The signal synthesizing circuit 40 has three switching circuits 41 to 43 and two adding circuits 44 and 45. [

A first switching circuit 41 is provided between the addition circuit 45 and the voltage / current conversion circuit 14 of the first signal generation circuit 10. A second switching circuit 42 is provided between the addition circuit 44 and the voltage / current conversion circuit 24 of the second signal generation circuit 20. A third switching circuit 43 is provided between the addition circuit 44 and the voltage / current conversion circuit 34 of the third signal generation circuit 30.

The signal synthesizing circuit 40 outputs the current signals Ib, Ie and Iw output from the first to third signal generating circuits 10, 20 and 30 to the control signal Sc of the control means 60 Through the first to third switching circuits 41 to 43 which are turned on only by one, and the driving current Id of the semiconductor laser 50 is generated by additionally adding them.

The first to third signal generating circuits 10 to 30 have the same circuit configuration and operate independently.

The control means 60 controls the laser power LO to be output from the semiconductor laser 50 in accordance with the operation of the optical disc apparatus by using any of the first switching circuits 41 to 43 in the signal combining circuit 10 shown in Table 1 And outputs a control signal Sc to select one of them. Therefore, the outputs of the first to third signal generating circuits 10, 20 and 30 are applied to the semiconductor laser 50 independently.

Table 1

When playing erase at the time of replay

Laser power (LO) Pb Pe Pw

First ON circuit (41) ON OFF OFF

Second SW circuit (42) OFF ON OFF

3rd SW circuit (41) OFF OFF ON

Further, the control means 60 outputs the control signal Sc so that the switching circuits 41 to 43 are controlled on / off in accordance with the data length of the recording data. For example, the control means 60 outputs a control signal Sc for performing on / off operations so that the write pulse shown in Fig. 1B is outputted from the semiconductor laser 50 to the recording data in Fig. 1A.

The light receiving element 51 is constituted by, for example, a photodiode for generating an electric signal according to light. A power supply voltage Vc is applied to the cathode of the photodiode. A photodiode, that is, a light receiving element 51 Is reverse-biased.

The light receiving element 51 receives a part of the laser light output from the semiconductor laser 50 to perform photoelectric conversion and generates a light receiving signal Ip of a current signal in accordance with the intensity of the received laser light.

The current / voltage conversion circuit (I / V) 52 converts the light receiving signal Ip of the current signal generated by the light receiving element 51 into the light receiving signal Vp of the voltage signal.

The semiconductor laser 50 has a nonlinear characteristic as shown in Fig. 4, and irradiates light of bias power (Pb), erase power (Pe), and write power (Pw) to an optical disk not shown. The semiconductor laser 50 has a non-linear characteristic as shown in Fig. 4, and the bias power level Pb, the erase power level Pe, and the write power level Pw are straight lines. However, due to the temperature characteristics around the semiconductor laser 50, changes over time, etc., characteristic changes occur as exemplified in the characteristic curves A1 and A2. Therefore, the laser driving circuit 90 is controlled by the semiconductor laser 50 so that the bias power level Pb, the erase power level Pe, and the write power level Pw are secured even when the characteristics of the semiconductor laser 50 change. (Id) &lt; / RTI &gt;

The first signal generating circuit 10 generates the first drive current Ib so that the light receiving signal Vp becomes the level at which the output power Lo of the semiconductor laser 50 indicates the bias power level Pb .

In the first signal generating circuit 10, the sample-and-hold circuit 11 samples the light-receiving signal Vp at a predetermined cycle based on the sampling theory, and generates an output signal S11 indicating a sample value. As the sample hold circuit 11, a bottom hold circuit may be used.

The target value setting circuit 15 sets the target value Lo so that the first drive current Ib indicative of the bias power level Pb is outputted from the first signal generation circuit 10, And outputs the first target signal S15 to the adder circuit 12. [

The adding circuit 12 subtracts the output signal S11 of the sample-and-hold circuit 11 from the first target signal S15 and generates a difference signal S12 (= S15-S11) indicating the deviation.

The loop filter 13 generates a filter signal S13 by attenuating the high frequency component of the difference signal S12 and applies the filter signal S13 to the voltage /

The voltage / current conversion circuit 14 converts the filter signal S13 of the voltage signal into the current signal Ib.

The second signal generating circuit 20 generates the second driving current Ie such that the light receiving signal Vp becomes the level at which the output power Lo of the semiconductor laser 50 indicates the erase power level Pe do.

The operation of the second signal generation circuit 20 is the same as that of the first signal generation circuit 10 described above. Only the points differing from the operation of the first signal generating circuit 10 will be described below.

The target value setting circuit 25 generates the second target signal S25 indicating the target value (reference value) of the output signal S21 of the sample hold circuit 21 and supplies the second target signal S25 to the adder circuit 22.

The third signal generating circuit 30 generates the third drive current Iw in which the light receiving signal Vp becomes the level at which the output power Lo of the semiconductor laser 50 indicates the write power level Pe.

The operation of the third signal generating circuit 20 is the same as that of the first signal generating circuit 10 described above. Only the points differing from the operation of the first signal generating circuit 10 will be described below.

The target value setting circuit 35 generates the third target signal S35 indicating the target value (reference value) of the output signal S31 of the sample hold circuit 31 and supplies the third target signal S35 to the adder circuit 32.

The drive signal (Id) from the signal composition circuit (40) is input to the anode of the semiconductor laser (50). The cathode is grounded and grounded (GND). In this semiconductor laser 50, the laser power Lo corresponding to the drive current Id applied to the anode

And emits laser light.

It is desired to simplify the circuit configuration of the laser driving circuit 90 shown in Fig.

A first signal generating circuit 10 for generating a driving current Ib for bias power Pb and a second signal generating circuit 20 for generating a driving current Ie for an erase power Pe And the third signal generating circuit 30 for generating the drive current Iw for the write power Pw operate independently of each other and have a similar circuit configuration and a simple circuit configuration is desired.

Subsequently, the signal synthesizing circuit 40 has three switching circuits 41 to 43 for selecting the driving currents Ib, Ie, and Iw, and simplification of the circuit configuration is desired.

Furthermore, although the laser drive circuit used in the optical disk device has been described as an example of the current generation circuit of the present invention, it is desired to overcome the same problem as the other current generation circuits not only in the laser drive circuit.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current generating circuit and method such as a laser driving circuit and a laser driving method for driving a semiconductor laser used for an optical disk device, for example.

1 is a waveform diagram illustrating laser power of a semiconductor laser when data is recorded by irradiating a phase change type optical disc with laser light from a semiconductor laser in an optical disc apparatus.

2 is a block diagram illustrating a laser driving circuit in an optical disc apparatus.

3 is a block diagram showing a first embodiment of a laser driving circuit as an example of a current generating circuit according to the present invention.

Fig. 4 is a characteristic diagram illustrating characteristics of the semiconductor laser in Fig. 3. Fig.

5 is a block diagram showing a second embodiment of a laser driving circuit as an example of a current generating circuit according to the present invention.

Fig. 6 is a flowchart showing a laser driving method performed in the laser driving circuit of Figs. 3 and 5. Fig.

DESCRIPTION OF THE REFERENCE NUMERALS

50 semiconductor laser 51 light receiving element

52 current / voltage conversion circuit 110,120,130 first to third signal generation circuits

111, 121 Sample hold circuits 112, 122 Addition (subtraction) circuit

113,123 loop filter 114,124,134 voltage / current conversion circuit

115, 125 Target setting circuit 135 Magnification setting circuit

136 multiplication circuit 142, 143 switching circuit

144, 145 Addition circuit 190 Laser driving circuit

Id drive current Lo laser power

A first object of the present invention is to simplify the circuit configuration of a current generation circuit that outputs three or more kinds of drive currents in a linear relationship.

A second object of the present invention is to provide a method usable in the current generation circuit.

A third object of the present invention is to provide an appropriate optical disk apparatus by using the current generation circuit as a laser drive circuit.

According to a first aspect of the present invention, there is provided a driving method of a driving device, comprising: inputting a signal indicating an operating state of a driving device used in a characteristic portion having nonlinear operating characteristics and displayed in a straight line, A first signal generation circuit for generating a first drive current at which the power becomes a first power level on the basis of a first target value and a second signal generation circuit for inputting a signal indicating an operation state of the drive device, A second driving current that is smaller than the first driving current at a second driving current at which the output power of the semiconductor laser 50 becomes a second power level higher than the first power level is generated based on a second target value 2 signal generating circuit, and a third drive current having a third power level higher than the second power level, A third signal generation circuit for generating a corrected third drive current smaller than the first drive current by multiplying the corrected second drive current by a predetermined multiple and a first switching circuit for selecting an output signal of the third signal generation circuit A second switching circuit for selecting an output signal of the second signal generating circuit; and an adder circuit for adding the signal selected by the first switching circuit and the signal selected by the second switching circuit to the output of the first signal generating circuit Wherein the first and second switching circuits are off in a first operation mode and the first switching circuit is turned off in a third operation mode, Off state, and the second switching circuit is in an on-state when the second switching circuit is turned off.

The signal combining circuit may further have a second adding circuit for adding the signal selected by the first switching circuit and the signal selected by the second switching circuit to output to the adding circuit.

The predetermined magnification is defined by the following formula.

(Third power level - first power level)

(Second power level-first power level)

According to a second aspect of the present invention, there is provided a semiconductor laser device comprising: a light receiving element for receiving a light receiving signal from a light receiving element for generating a light receiving signal corresponding to light emitted from a semiconductor laser; A first signal generation circuit for receiving the light receiving signal and outputting a first semiconductor laser driving current based on a first output signal of the semiconductor laser, A second signal generation circuit for generating, based on a second target value, a correction second driving current smaller than the first semiconductor laser driving current, which is a second semiconductor laser driving current which becomes a second power level; 2 &lt; / RTI &gt; higher than the first semiconductor laser drive current, which is lower than the third semiconductor laser drive current, A second switching circuit for selecting an output signal of the third signal generating circuit, and a second switching circuit for selecting a signal selected by the first switching circuit and a signal selected by the first switching circuit, 2 switching circuit and an adder circuit for adding the output of the first signal generator circuit and applying the result of the adder circuit to the semiconductor laser, wherein in the first operation mode, The second switching circuit is off, and in the second operation mode, the second switching circuit is off when the first switching circuit is on, the first switching circuit is off in the third operation mode, There is provided a laser driving circuit having a signal combining circuit in which the switching circuit is in the on state.

The signal combining circuit may further include a second adding circuit for adding the signal selected by the first switching circuit and the signal selected by the second switching circuit to output to the adding circuit.

Preferably, the laser driving circuit is used in an optical disc apparatus, laser light emitted from the semiconductor laser is irradiated onto a phase change type optical disc and the light receiving element, and the first power level is a level of a bias power , The second power level is a level of erasing power for erasing data recorded on the optical disc, the third power level is a level of write power for writing data to the optical disc, Wherein the second operation mode is a level of the erase power and is a mode for driving the semiconductor laser, the third operation mode is the level of the light, Wherein the first and second switching circuits are turned on in accordance with an erase pulse waveform and a light waveform, It is driven off.

According to a third aspect of the present invention, there is provided a phase-change type optical disc, comprising: a phase-change type optical disc; a semiconductor laser for irradiating the optical disc with laser light; a light-receiving element for generating a light-receiving signal in accordance with the emitted light of the semiconductor laser; Control means for controlling reading of the optical data, erasing of the optical data, writing of data into the optical data, and the laser driving circuit. Wherein said control means operates said first and second switching circuits in an off mode in said data read mode, and in said erase mode, in a state in which said second switching circuit is off, And turns on and off the second switching circuit in accordance with the write waveform in a state in which the first switching circuit is turned off in the writing mode.

According to a fourth aspect of the present invention, there is provided a semiconductor laser device comprising: a light receiving element for receiving a light receiving signal from a light receiving element for generating a light receiving signal corresponding to light emitted from a semiconductor laser; A first signal generating means for generating a first semiconductor laser driving current based on a first target value and a second signal generating means for generating a first semiconductor laser driving current based on a first target value, A second signal generating means for generating a corrected second driving current smaller than the first semiconductor laser driving current at a higher second power level than a second semiconductor laser driving current based on a second target value; Is smaller than the first semiconductor laser driving current in a third semiconductor laser driving current which is a third power level higher than the second power level Third signal generating means for generating a third driving current by multiplying the corrected second driving current by a predetermined multiple, first switching means for selecting an output signal of the third signal generating means, Means for selecting a signal selected by the first switching means and a signal selected by the second switching means and adding means for adding the output of the second signal generating means to the signal selected by the first switching means, Wherein the first and second switching means are turned off in the first operation mode and the first switching means is turned on in the second operation mode, 2 switching means is off, and in the third operation mode, the first switching means is off and the second switching means is on.

The signal synthesizing means may further have second adding means for adding the signal selected by the first switching circuit and the signal selected by the second switching means to output to the adding means.

According to a fifth aspect of the present invention, there is provided a phase change optical disc, comprising: a phase change type optical disc; a semiconductor laser for irradiating the optical disc with laser light; a light receiving element for generating a light receiving signal in accordance with the emitted light of the semiconductor laser; Control means for controlling reading of the optical data, erasing of the optical data, writing of data into the optical data, and the laser driving circuit. Wherein said control means operates said first and second switching circuits in an off mode in said data read mode, and in said erase mode, in a state in which said second switching circuit is off, And turns on and off the second switching means according to the write waveform in a state in which the first switching circuit is turned off in the writing mode.

According to a sixth aspect of the present invention, there is provided a semiconductor laser device comprising: (a) a step of inputting a light receiving signal from a light receiving element for generating a light receiving signal according to light emitted from a semiconductor laser; (b) Wherein the first semiconductor laser driving current is generated based on a first target value and the output power of the semiconductor laser represented by the light receiving signal is higher than the second power The second semiconductor laser driving current is lower than the first semiconductor laser driving current based on a second target value, and the output power of the semiconductor laser is higher than the second power level A third compensating driving current which is smaller than the first semiconductor laser driving current in a third semiconductor laser driving current which is a third power level, (C) outputting the first semiconductor laser drive current in a first operation mode, and outputting the first semiconductor laser drive current and the corrected second drive current in a second mode, And adding and outputting the first semiconductor laser drive current and the correction third drive current in a third mode and outputting the sum.

Best Mode for Carrying Out the Invention Hereinafter, a preferred embodiment of the current generation circuit of the present invention will be described with reference to the drawings.

As a preferred embodiment of the current generating circuit of the present invention, for example, there is provided a drive circuit for providing three kinds of drive currents having a linear relationship in a use region, having nonlinear characteristics such as semiconductor lasers, A laser driving circuit for use in an apparatus will be described.

It should be noted that, in the following preferred embodiments, the current generation circuit of the present invention is applicable to various fields that have nonlinear characteristics and provide three kinds of drive currents in a linear relationship in the use region .

First Embodiment

3 is a block diagram of a first embodiment of a laser driving circuit as a preferred embodiment of a current generating circuit according to the present invention.

The laser driving circuit 190 shown in Fig. 3 is provided in an optical disc apparatus for writing, erasing and reproducing data by using, for example, a phase change type optical disc as a recording medium, And drives the semiconductor laser that generates the irradiated laser light.

The laser driving circuit 190 shown in FIG. 3 has first to third signal generating circuits 110, 120, and 130 and a signal combining circuit 140.

The laser drive circuit 190 is configured to cooperate with the semiconductor laser 50, the light receiving element 51, the current / voltage conversion circuit (I / V) 52 and the control means 160, The semiconductor laser 50 emits laser light for reading data, erasing data, and writing data from the semiconductor laser 50. In other words, the optical disc device has a semiconductor laser 50, a light receiving element 51, a current / voltage conversion circuit 52, a control means 160, and a laser drive circuit 190.

The semiconductor laser 50, the light receiving element 51, and the current / voltage conversion circuit (I / V) 52 are substantially the same as those described with reference to Fig.

The first signal generating circuit 110 has substantially the same circuit configuration as that of the first signal generating circuit 10 described with reference to Fig. 2, and on the basis of the detection current Ip of the light receiving element 51, And generates a bias current Ib as a drive current. The first signal generating circuit 110 includes a sample hold circuit (SHb) 111, an addition (subtraction) circuit 112, a loop filter LPb and a voltage / current conversion circuit (V / And a target value setting circuit (SETb)

The second signal generating circuit 120 is basically the same as the second signal generating circuit 20 described with reference to Fig. 2, and is a second laser generating device, which is based on the detection current Ip of the light receiving element 51, (Erase) current Ibe is generated as the driving current.

The correction current Ibe is different from the erase current Ie described with reference to Fig. 2, and Ibe = Ie-Ib. Ib is a bias current as the first laser drive current generated by the first signal generation circuit 110. [

The second signal generation circuit 120 shown in Fig. 3 is different from the second signal generation circuit 20 shown in Fig. 2, and applies an intermediate output signal to the third signal generation circuit 130. [

The second signal generating circuit 120 includes a sample hold circuit (SHbe) 121, an addition (subtraction) circuit 122, a loop filter LPbe and a voltage / current conversion circuit V / And a target value setting circuit (SETB) 125. [

The circuit configuration of the third signal generating circuit 130 is greatly different from that of the third signal generating circuit 30 described with reference to Fig. The sample / hold circuit 31, the adder circuit 32 and the loop filter (LPbe) 33 in the third signal generating circuit 30 of Fig. 2 are eliminated and the voltage / current converting circuit V / Ibw) 134, a magnification setting circuit (SETwa) 135, and a multiplication circuit 136. [ The output signal of the loop filter (LPbe) 123 of the second signal generation circuit 20 is applied to the multiplication circuit 136.

The corrected third drive current Ibw output from the third signal generation circuit 130 is different from the third drive current Ih described with reference to Fig. 2, and Ibw = Iw-Ib.

The signal combining circuit 140 has two switching circuits 142 and 143 and two adding circuits 144 and 145. [ Compared with the signal synthesizing circuit 40 described with reference to Fig. 2, there is only one switching circuit.

The signal synthesizing circuit 140 generates the drive current Id of the semiconductor laser 50 according to the purpose by combining the current signals Ib, Ibeb and Ibw under the control of the control means 160. [

A switching circuit 142 is provided between the addition circuit 144 and the voltage / current conversion circuit 124. A switching circuit 143 is provided between the addition circuit 144 and the voltage / current conversion circuit 134.

The control means 160 differs from the control means 60 shown in Fig. 2 in the processing contents.

The switching circuits 142 and 143 perform ON / OFF operations as shown in Table 2 on the basis of the control signal Sc output from the control means 160 that specifies the target value of the laser power Lo.

Table 2

When playing erase at the time of replay

Laser power (Lo) Pb Pe Pw

SW circuit (142) OFF ON OFF

SW circuit (143) OFF OFF ON

The control means 160 outputs the control signal Sc so that the write pulse shown in Fig. 1B is outputted from the semiconductor laser 50 to the recording data in Fig. 1A, for example, 142, and 143, respectively.

When the semiconductor laser 50 is driven with the bias power Pb, that is, when the data is reproduced from the optical disk, the switching circuits 142 and 143 are turned off by the control signal Sc output from the control means 160 do. As a result, the adding circuit 145 applies the current signal Ib, which is the output of the first signal generating circuit 110, to the semiconductor laser 50 as the driving current Id.

When the semiconductor laser 50 is driven with the erase power Pe, the switching circuit 142 is turned on by the control signal Sc output from the control means 160 and the switching circuit 143 is turned off do. The resultant addition circuit 145 adds the current signal Ib output from the first signal generation circuit 110 and the second current signal Ia through the addition circuit 144 which is the output of the second signal generation circuit 120 Ibe) is applied to the semiconductor laser 50 as the driving current Id.

When the semiconductor laser 50 is driven with the write power Pw, the switching circuit 142 is turned off and the switching circuit 143 is turned on by the control signal Sc output from the control means 160 . The resultant addition circuit 145 receives the current signal Ib as the output of the first signal generation circuit 110 and the third current signal Ia passing through the addition circuit 144 which is the output of the third signal generation circuit 130 Iwe) is applied to the semiconductor laser 50 as the driving current Id.

The light receiving element 51 is constituted by, for example, a photodiode, as described with reference to Fig. 2, in which the power supply voltage Vc is applied to the cathode of the photodiode, that is, The light receiving element 51 is reverse biased.

The light receiving element 51 receives a part of the laser light output from the semiconductor laser 50 to perform photoelectric conversion and generates a light receiving signal Ip of a current signal in accordance with the intensity of the received laser light.

The semiconductor laser 50 emits front light used for writing data to the optical disc and white light used for monitoring the level of light received by the light receiving element 51. [ The light receiving element 51 normally receives the white light of the semiconductor laser 50.

The current / voltage conversion circuit (I / V) 52 converts the light receiving signal Ip of the current signal generated by the light receiving element 51 into the light receiving signal Vp of the voltage signal.

The first signal generating circuit 110 generates the first drive current, that is, the bias current Ib, at which the output power Lo of the semiconductor laser 50 represented by the light receiving signal Vp becomes the bias power level Pb, On the basis of the target value of the target value setting circuit 115.

In the first signal generating circuit 110, the sample-and-hold circuit 111 samples and holds the light-receiving signal Vp at predetermined intervals, and generates an output signal S111 indicating a sample value. As the sample hold circuit 111, a bottom hold circuit may be used.

The target value setting circuit 115 generates a target value (or a reference value) signal S115 for generating a first drive current, i.e., a bias current Ib, and supplies the first target signal S115 to the adder circuit 112 .

The adding circuit 112 reduces the output signal S111 of the sample hold circuit 111 in the first target signal S115 and generates a difference signal S112 (= S115-S111) indicating the deviation.

The loop filter 113 generates a filter signal S113 that attenuates the high-frequency component of the difference signal S112 and passes the low-frequency component, and supplies the filter signal S113 to the voltage / current conversion circuit 114 . The loop filter 113 is a low-pass filter.

The voltage / current conversion circuit 114 converts the filter signal S113 of the voltage signal into the bias current signal Ib of the current signal.

The second signal generating circuit 120 generates the second drive current Ie from the second drive current Ie whose output power Lo of the semiconductor laser 50 indicated by the light receiving signal Vp becomes the eithless power level Pe, (Corrected aperture current) Ibe (Ibe = Ie-Ib) which is a difference current smaller than the bias current signal Ib.

Second signal generating reason for generating a second drive current (Ie) a first drive current (bias current signal (Ib) smaller current signal (correction seven days device current) (I _be) as in in the circuit 120, the signal In the adding circuit 145 in the combining circuit 140, the first driving current (bias current I) output from the first signal generating circuit 110 is supplied to the current signal I _be outputted from the second signal combining circuit 120, The signal Ib is added and the drive current Id of the semiconductor laser 50 becomes the second drive current Ie.

The circuit configuration of the second signal composition circuit 120 is similar to that of the first signal generation circuit 110 and its operation is the same as that of the first signal generation circuit 110 described above.

The sample-and-hold circuit 121 samples the light-receiving signal Vp at a predetermined cycle to maintain its value, and generates an output signal S121 indicating a sample value.

The target value setting circuit 125, the output of the semiconductor laser 50 power (Lo) is seven days device power level, a first drive current (bias current signal (I _b)) in the second drive current (Ie) is a (Pe) generating a second target signal (S125) indicating a small primary current of the target value of the current signal (correction seven days device current) (I _be), as, and outputs the second target signal (S125) to the addition circuit 122. the

The adding circuit 122 reduces the output signal S121 of the sample hold circuit 121 in the second target signal S125 and generates a difference signal S122 (= S125-S121) indicating the deviation.

The loop filter 123 attenuates the high-frequency component of the difference signal S112 to generate a filter signal S123 that passes the low-frequency component, and supplies the filter signal S123 to the voltage / current conversion circuit 124 and the multiplication circuit 124. [ (136). The loop filter 113 is a low-pass filter.

The voltage / current conversion circuit 124 converts the filter signal S123 from the voltage signal to the current signal Ibe.

The third signal generating circuit 130 generates the first signal from the third driving current Iw at which the output power Lo of the semiconductor laser 50 represented by the light receiving signal Vp becomes the writing power level Pw (Corrected write current) I _bw (I _bw = Iw-Ib) smaller than the first drive current Ib outputted from the circuit 110 to the magnification m from the magnification setting circuit 135 Based on the signal S135.

The reason why the third signal generating circuit 130 generates the corrected third drive current (or corrected write drive current) signal I _bw by the first drive current Ib in the third drive current Iw And outputs the first driving current (I _bw ) output from the first signal generating circuit 110 to the current signal I _bw output from the third signal combining circuit 130 in the adding circuit 145 in the signal combining circuit 140, I _b ).

In the third signal composition circuit 130, the multiplication circuit 136 multiplies the filter signal S123 output from the second signal generation circuit 120 by the output signal S135 of the magnification setting circuit 135 Multiplies the multiplication factor m, and generates a multiplication result signal S136.

The magnification setting circuit 135 generates a magnification setting signal S135 indicating a magnification m defined by the following equation and outputs the magnification setting signal S135 to the multiplication circuit 136. [

m = (Pw-Pb) / (Pe-Pb)

Pw is the write power level of the semiconductor laser 50,

Pb is the bias power of the semiconductor laser 50,

Pe is an erase power of the semiconductor laser 50. ... (One)

The voltage / current conversion circuit 134 converts the multiplication signal S136 of the multiplication circuit 136 from the voltage signal to the current signal Ibw.

The driving signal (Id) from the signal combining circuit 140 is input to the anode of the semiconductor laser 50. [ The cathode is grounded and grounded (GND). The semiconductor laser 50 emits laser light at a laser power Lo in accordance with the drive current Id.

Fig. 4 is a characteristic diagram illustrating the characteristics of the semiconductor laser 50 in Fig. 3. The horizontal axis of the characteristic diagram shows the driving current Id, and the vertical axis shows the laser power Lo.

The characteristics of the semiconductor laser 50 may vary depending on the temperature, a change with time, and the like, and these changes are exemplified by changes in temperature, time, and the like. Of course, the change of the characteristics of the semiconductor laser 50 is not limited to the two characteristic curves A1 and A2 shown in Fig. 4, but may be changed between the characteristic curves A1 and A2 due to the change of temperature and aging, A2. &Lt; / RTI &gt;

The laser drive circuit 190 shown in Fig. 3 drives the semiconductor laser 50 whose characteristic changes by the temperature and the change with time shown in Fig.

The characteristic curve A1 has the following characteristics.

When the drive current Id = Ib _1, the laser power L _o = Pb.

When the drive current Id Ie = _1, the laser power L _o = Pe.

When the drive current Id = Iw ₁ , the laser power L _o = Pw.

The characteristic curve A2 has the following characteristics.

When the drive current Id = Ib _2, the laser power L _o = Pb.

When the drive current Id = Ie _2, the laser power L _o = Pe.

When the drive current Id = Iw _2, the laser power L _o = Pw.

In FIG. 4, Ie ₁ -Ib ₁ = Ibe ₁ , and Iw ₁ -Ib ₁ = Ibw ₁ . Further, Ie ₂ -Ib ₂ = Ibe ₂ , and Iw ₂ -Ib ₂ = Ibw ₂ .

The drive currents Ib _{1 and} Ib ₂ represent the output current Ib of the voltage / current conversion circuit 114 in the first signal generation circuit 110 when the laser power L _o = Pb.

3 detects the output power of the semiconductor laser 50 with the light receiving element 51 when the characteristic of the semiconductor laser 50 is the characteristic curve A1, and it performs a feedback control so that the output current Ib is equal to the driving current Ib _1. The first signal generating circuit 110 in Fig. 3 detects the output power of the semiconductor laser 50 with the light receiving element 51 when the characteristic of the semiconductor laser 50 is the characteristic curve A2, the corresponding first driving current Ib ₂ and performs a feedback control to be the same as the output current Ib.

The currents Ibe _{1 and} Ibe ₂ represent the output current Ibe of the voltage / current conversion circuit 124 in the second signal generation circuit 120 when the laser power L _o = Pe.

The second signal generating circuit 120 in Fig. 3 detects the output power of the semiconductor laser 50 at the light receiving element 51 when the characteristic of the semiconductor laser 50 is the characteristic curve A1, Feedback control is performed so that the output current Ibe is equal to Ibe ₁ . 3 detects the output power of the semiconductor laser 50 at the light receiving element 51 when the characteristic of the semiconductor laser 50 is the characteristic curve A2, in response to the differential current Ibe ₂ and it performs a feedback control so that the output current is equal to Ibe.

Current Ibw _{1 and} Ibw ₂ represent the output current Ibw of voltage / current conversion circuit 134 in third signal generation circuit 130 when laser power L _o = Pw.

3 detects the output power of the semiconductor laser 50 at the light receiving element 51 when the characteristic of the semiconductor laser 50 is the characteristic curve A1 and outputs the proportional current in Ibw ₁ it is subjected to feedback control such that the output current is equal Ibw. The third signal generating circuit 130 in Fig. 3 detects the output power of the semiconductor laser 50 with the light receiving element 51 when the characteristic of the semiconductor laser 50 is the characteristic curve A2, an output current proportional to the current Ibw Ibw ₂ and performs a feedback control to be the same.

The characteristic curves A1 and A2 of the semiconductor laser 50 are linear or substantially linear when O <L _o and have different slopes of straight lines from the characteristic curves A1 and A2. Therefore, the following equation (2) is established. That is, the ratio Ibw ₁ / Ibe ₁ is equal to the ratio Ibw ₂ / Ibe ₂ and is equal to the magnification m defined in Equation 1, i.e., (Pw-Pb) / (Pe-Pb).

Ibw ₁ / Ibe ₁ = Ibw ₂ / Ibe ₂ = (Pw-Pb) / (Pe-Pb) (2)

Even if the characteristics of the semiconductor laser 50 change, the output currents Ibe ₁ and Ibe ₂ of the voltage / current conversion circuit 124 in the second signal generation circuit 120 can be used as the third signal generation circuit The output currents Ibw ₁ and Ibw ₂ of the voltage / current conversion circuit 134 in the output circuit 130 can be calculated.

Further, the input signal of the voltage / current conversion circuit 124 can be generated by multiplying the input signal of the voltage / current conversion circuit 124 by the ratio (magnification) m shown in Expression 2.

More specifically, the magnification m indicated by the output signal S135 of the magnification setting circuit 135 is multiplied by a magnification ratio ((Pw-Pb) / (Pe-Pb) 136) by multiplying the multiplication factor by the filter signal S123, it is possible to generate the multiplication signal S136 which is the input signal of the voltage / current conversion circuit 134. [

The laser driving circuit 190 shown in Fig. 3 is different from the laser driving circuit 90 of Fig. 2 in that the third signal generating circuit 130 removes the sample hold circuit and the loop filter, The number of switching circuits is reduced, so that the circuit configuration is simplified.

The laser drive circuit 190 shown in Fig.3 sets the filter signal S123 input to the voltage / current conversion circuit 124 to the magnification setting circuit 135 in the multiplication circuit 136 in the third signal generation circuit 130, Current conversion circuit 134, the ratio of the current Ibw to the current Ibe is multiplied by the multiplication factor of the equation (2) Can be exactly matched.

Second Embodiment

5 is a configuration diagram of a second embodiment of the laser driving circuit of the present invention.

The laser driving circuit 190A shown in Fig. 5 omits the adding circuit 144 in the signal generating circuit 140 shown in Fig. 3 and outputs the output of the switching circuits 142 and 143 directly to the adding circuit 145a And the signal synthesizing circuit 140A is used. The other circuit configuration is the same as the laser driving circuit 190 described with reference to Fig.

As described above, only one of the switching circuits 142 and 143 is on / off controlled, and the other is turned off, so that the output of the switching circuits 142 and 143 can be directly applied to the adding circuit 145a. As a result, the laser driving circuit 190A of Fig. 5 has a simpler circuit configuration than the laser driving circuit 190 shown in Fig.

Third Embodiment

Although the first to third signal generating circuits 110, 120, and 130 and the signal combining circuits 140 and 140A constituting the laser driving circuit 190 and 190A shown in Figs. 3 and 5 are described as circuits, It is also possible to realize a circuit by a software process by a computer, a signal process by a digital signal processor (DSP), or a dedicated signal processing integrated circuit.

In this case, the computer or the like performs signal processing of the components of the circuit shown in Figs. 3 and 5.

Hereinafter, a case where a computer is used will be described. Also, the control means 160 can be realized by using the same computer.

Laser driving method

Fig. 6 is a flowchart of a laser driving method showing the processing in the case where the signal processing of the laser driving circuit 190, 190A in Figs. 3 and 5 is performed by a computer, a DSP, or the like.

Step S1: The generation of the light receiving signal

The light receiving element 51 receives a part of the output laser light of the semiconductor laser 50 and generates a light receiving signal Ip of the current signal.

The current / voltage conversion circuit 52 converts the light reception signal Ip of the current signal into the light reception signal Vp of the voltage signal.

Step S2: generation of drive current

The signal processing of the first to third signal generating circuits 110, 120, and 130 of FIG. 3 and FIG. 5 is performed independently and simultaneously. When the operation of the first to third signal generation circuits 110, 120, and 130 is performed by using a computer or a DSP, the first to third signal generation circuits 110, 120 and 130 are sequentially operated. However, And is performed in one sampling period by performing high-speed processing, so that it is practically performed at the same time. The relationship between the processing of the first signal generating circuit and the processing of the second signal generating circuit is not required. However, since the third signal generating circuit performs calculation using the result of the second signal generating circuit, the processing of the third signal generating circuit is desirable after the processing of the second signal generating circuit.

As a process of the first signal generating circuit 110, the computer generates the first target signal S115 indicating the target value of the sample value of the light receiving signal Vp and the signal indicating the sample value of the light receiving signal Vp (S115-S111) between the bias current (S111) and the bias current (S111), and generates a first drive current corresponding to the bias power Pb, that is, a bias current, based on the deviation.

As a process of the second signal generating circuit 120, the computer calculates the difference between the second target signal S125 indicating the target value of the sample value of the light receiving signal Vp and the signal S121 indicating the sample value of the light receiving signal Vp (S125-S121), and based on the deviation, generates a first current, that is, a corrected erase current, which is smaller than the second driving current corresponding to the erase power Pe.

As a process of the third signal generating circuit 130, the computer calculates a value {(S125-S121) - (Pw-Pb) / (Pe) obtained by multiplying the deviation m by the deviation S125-S121 obtained by the second signal generating circuit -Pb)}. Based on the result, a second current (proportional current) smaller than the third drive current corresponding to the write power Pw by the first drive current is generated.

When a computer is used, the multiplication process is fairly simple,

Steps S3 and S4:

The control means 160 detects the current operation mode of the optical disc apparatus and allows the drive current according to the mode to be applied to the semiconductor laser 50. [

The control means 160 determines whether the target value of the laser power Lo indicating that the operation mode of the optical disk apparatus is the write mode is the write power Pw or whether the target value of the laser power Lo It is determined whether or not it is power Pe. In the other modes, the bias mode is used.

When the operation mode is determined, any of the following processes is performed.

Step S5: generation of write drive current

The control means 160 adds the first drive current Ib and the corrected third write current Iwb so that the target value of the laser power Lo becomes the write power Pw.

Step S6: Creation of an erase driving current

The control means 160 adds the first drive current Ib and the corrected second erase current Ieb so that the target value of the laser power Lo becomes the eithless power Pe.

Step S7: Generation of bias drive current

The control means 160 outputs only the first drive current Ib so that the target value of the laser power Lo becomes the bias power Pb.

The control means 160 repeats the above processing.

In the optical disk apparatus having the laser driving circuit 190, the magnification is read from the optical disk on which the data representing the magnification of the equation (2) is recorded in advance by the control means 160, and the magnification read by the magnification setting circuit 135 Setting.

The optical disc may be a phase-change type DVD-RW or DVD-RAM, for example.

The above embodiment is an example of the present invention, and the present invention is not limited to the above embodiment.

For example, the above-described laser driving circuit is not limited to application to an optical disc apparatus, and even when generating three types of driving signals in a predetermined linear relationship, the above-described laser driving circuit can be applied as a current generating circuit .

As described above, according to the present invention, it is possible to simplify the circuit configuration of a current generation circuit such as a laser drive circuit that outputs three or more laser powers in a semiconductor laser. As a result, for example, when the laser driving circuit of the present invention is used, the configuration of the optical disk apparatus becomes simple.

Further, according to the present invention, it is possible to provide a method usable in the current generating circuit or the current generating apparatus.

The laser driving circuit of the present invention can be applied as a driving circuit of a semiconductor laser in an optical disc apparatus. The driving current generating circuit of the present invention can be applied as a circuit for generating a current for driving a driving device used in a linear region while having a nonlinear characteristic such as a semiconductor laser.

Claims (21)

A linear driving circuit for inputting a signal indicative of an operating state of a driving device used in a linear region and outputting a first driving current having a first power level at which the output power of the driving device, A first signal generation circuit for generating a first signal based on a first target value, A signal indicating the operating state of the driving device is inputted to the first driving circuit and the second driving current is outputted from the second driving circuit in a state where the output power of the semiconductor laser is a second power level higher than the first power level, A second signal generation circuit for generating a corrected second drive current smaller than the drive current based on a second target value, A third compensating driving current that is smaller than the first driving current in a third driving current at which the output power of the driving device becomes a third power level higher than the second power level, A third signal generation circuit for generating a second signal, A second switching circuit for selecting an output signal of the third signal generating circuit and an adding circuit for adding the signal selected by the first switching circuit and the signal selected by the second switching circuit to the output of the first signal generating circuit Wherein the first and second switching circuits are turned off in a first operation mode and the first switching circuit is turned on in a second operation mode, And the second switching circuit is turned on when the first switching circuit is turned off in the third operation mode. The method according to claim 1, The signal combining circuit further includes a second adding circuit for adding the signal selected by the first switching circuit and the signal selected by the second switching circuit to output to the adding circuit. 3. The method according to claim 1 or 2, The predetermined magnification is determined by the following formula, (Third power level - first power level) (Second power level-first power level) And the current generation circuit. Receiving a light receiving signal from a light receiving element for generating a light receiving signal according to light emitted from a semiconductor laser, and outputting a first semiconductor laser driving current, which is output power of the semiconductor laser represented by the light receiving signal, A first signal generation circuit for generating, based on one target value, A first semiconductor laser driving current which is lower than the first semiconductor laser driving current and whose output power is higher than a first power level and which is represented by the light receiving signal, A second signal generation circuit for generating a second drive current based on a second target value, And a third semiconductor laser drive current having a third power level higher than the second power level by the output power of the semiconductor laser is set to a predetermined third drive current smaller than the first semiconductor laser drive current, A third signal generation circuit for generating a signal by multiplying a multiple thereof, A second switching circuit for selecting an output signal of the second signal generation circuit; and a second switching circuit for selecting a signal selected by the first switching circuit and a signal selected by the second switching circuit A signal synthesizing circuit having a selected signal and an addition circuit for adding the output of the first signal generation circuit and applying a result of the addition circuit to a semiconductor laser, wherein in the first operation mode, the first and second switching circuits The second switching circuit is off in the second operation mode and the first switching circuit is off in the third operation mode and the second switching circuit is on when the first switching circuit is on, State, wherein the signal synthesizing circuit is in a state of being turned on. 5. The method of claim 4, Wherein the signal combining circuit further has a second adding circuit for adding the signal selected by the first switching circuit and the signal selected by the second switching circuit to output to the adding circuit. The method according to claim 4 or 5, The predetermined magnification is determined by the following formula, (Third power level - first power level) (Second power level-first power level) And a laser driving circuit for driving the laser driving circuit. The method according to claim 4 or 5, Wherein the first signal generation circuit comprises: A first sample hold circuit for sampling the light reception signal, A first target value generating circuit for outputting, as a first target value, a first semiconductor laser driving current whose output power of the semiconductor laser is the first power level, And a first subtraction circuit for subtracting the output signal of the first sample-and-hold circuit at the first target value to generate a first differential signal, And outputs the first differential signal as the first driving current. The method according to claim 4 or 5, Wherein the second signal generation circuit comprises: A second sample hold circuit for sampling the light receiving signal, A second target value generating circuit for outputting, as a second target value, a second semiconductor laser driving current whose output power of the semiconductor laser indicated by the light receiving signal becomes a first power level higher than the first power level, And a second subtraction circuit for subtracting the output signal of the second sample / hold circuit from the second target value to generate a second differential signal, And outputs the second differential signal as the second correction drive current. 9. The method of claim 8, The second signal generation circuit further has a filter for passing a low-frequency component of the second differential signal, which is an output of the subtraction circuit, And outputs a signal that has passed through the filter as the second correction drive current. 10. The method according to claim 8 or 9, Wherein the third signal generation circuit comprises: Outputting a magnification for generating a corrected third drive current smaller than the first semiconductor laser drive current in a third semiconductor laser drive current at which the output power of the semiconductor laser becomes a third power level higher than the second power level, Circuit, And a multiplier circuit that multiplies the corrected second drive current generated by the second signal generator circuit by a magnification output from the magnification generator circuit, And outputs the multiplication result as the third drive current. The method according to claim 4 or 5, The laser driving circuit is used in an optical disk apparatus, The laser light emitted from the semiconductor laser is irradiated onto the phase change type optical disk and the light receiving element, Wherein the first power level is a level of a bias power, The second power level is a level of erase power for erasing data recorded on the optical disk, The third power level is a level of write power for recording data on the optical disk, Wherein the first operation mode is a mode for driving the semiconductor laser at a level of the bias power and the second operation mode is a mode for driving the semiconductor laser at a level of the erase power, A mode for driving the semiconductor laser at a level of write power, Wherein the first and second switching circuits are driven on and off in accordance with an erase pulse waveform and a light waveform. A phase change type optical disc, A semiconductor laser for irradiating the optical disk with a laser beam, A light receiving element for generating a light receiving signal corresponding to the emitted light of the semiconductor laser, Control means for controlling reading of data from the optical disc, erasing of the optical data, and writing of data into the optical data; A first signal generating circuit which receives a light receiving signal from the light receiving element and generates a semiconductor laser driving current whose output power of the semiconductor laser is represented by the light receiving signal at a bias power level on the basis of a first target value, And a second semiconductor laser drive current which is smaller than the first semiconductor laser drive current in which the output power of the semiconductor laser represented by the light reception signal becomes an erase power level at the bias power level, A second signal generation circuit for generating a second drive current based on a second target value, The third semiconductor laser driving current being smaller than the first semiconductor laser driving current in a case where the output power of the semiconductor laser becomes a write power level higher than the erase power level, A third signal generation circuit for generating a signal by multiplying a multiple thereof, A second switching circuit for selecting an output signal of the second signal generating circuit, and a second switching circuit for selecting a signal selected by the first switching circuit and a signal selected by the second switching circuit And a signal synthesizing circuit having an addition circuit for adding the selected signal and the output of the first signal generation circuit and applying a result of the addition circuit to the semiconductor laser, Wherein, In the data read mode, the first and second switching circuits are turned off, In the erase mode, the first switching circuit is turned on and off according to the erase waveform in a state in which the second switching circuit is turned off, And the second switching circuit is turned on and off in accordance with a write waveform in a state in which the first switching circuit is turned off in the writing mode. 13. The method of claim 12, Wherein said signal combining circuit further has a second adding circuit for adding the signal selected by said first switching circuit and the signal selected by said second switching circuit to output to said adding circuit. The method according to claim 12 or 13, The predetermined magnification is determined by the following formula, (Third power level - first power level) (Second power level-first power level) . Receiving a light receiving signal from a light receiving element for generating a light receiving signal according to light emitted from a semiconductor laser, and outputting a first semiconductor laser driving current, which is output power of the semiconductor laser represented by the light receiving signal, First target signal generation means for generating, based on one target value, A second semiconductor laser driving current having a second power level higher than the first power level, the output power of the semiconductor laser represented by the light receiving signal being smaller than the first semiconductor laser driving current Second signal generating means for generating a second driving current based on a second target value, The third semiconductor laser driving current having a third power level higher than the second power level by the output power of the semiconductor laser is set to be smaller than the first semiconductor laser driving current, A third signal generating means for generating a predetermined multiplied signal by multiplying, A second switching means for selecting an output signal of the second signal generating means, and a second switching means for selecting a signal selected by the first switching means and a second switching means And a signal adding means for adding the output of the first signal generating means and applying a result of the adding means to the semiconductor laser. In the first operation mode, the second switching means is turned off In the second operation mode, the second switching means is on, the second switching means is off, the first switching means is on in the third operation mode, and the second switching means is on And a signal synthesizing means. 16. The method of claim 15, Further comprising second adding means for adding the signal selected by the first switching circuit and the signal selected by the second switching means to output to the adding means the signal combining means. 17. The method according to claim 15 or 16, The predetermined magnification is determined by the following formula, (Third power level - first power level) (Second power level-first power level) And a laser driving circuit for driving the laser driving circuit. A phase change type optical disc, A semiconductor laser for irradiating the optical disk with a laser beam, A light receiving element for generating a light receiving signal corresponding to the emitted light of the semiconductor laser, Control means for controlling reading of data from the optical disc, erasing of the optical data, and writing of data into the optical data; First signal generating means for receiving a light receiving signal from the light receiving element and generating a semiconductor laser driving current whose output power of the semiconductor laser is represented by the light receiving signal at a bias power level on the basis of a first target value, And a second semiconductor laser drive current which is smaller than the first semiconductor laser drive current in which the output power of the semiconductor laser represented by the light reception signal becomes an erase power level at the bias power level, A second signal generation circuit for generating a second drive current based on a second target value, The third semiconductor laser driving current being smaller than the first semiconductor laser driving current in a case where the output power of the semiconductor laser becomes a write power level higher than the erase power level, A third signal generating means for generating by multiplying a multiple, First switching means for selecting an output signal of the third signal generating means, second switching means for selecting an output signal of the second signal generating means, and a signal selected by the first switching means, And signal adding means for adding the selected signal to the output of the first signal generating means and for applying the result of the adding means to the semiconductor laser, Wherein, In the read-out mode of the data, the first and second switching means are turned off, In the erase mode, the first switching means is turned on and off according to the erase waveform in a state in which the second switching means is turned off, In the write mode, the second switching means is turned on and off according to a write waveform in a state in which the first switching circuit is turned off. 19. The method of claim 18, Further comprising second adding means for adding the signal selected by the first switching circuit and outputting the added signal to the adding means. 20. The method according to claim 18 or 19, The predetermined magnification is determined by the following formula, (Third power level - first power level) (Second power level-first power level) . Receiving a light receiving signal from a light receiving element for generating a light receiving signal corresponding to light emitted from a semiconductor laser; Wherein the first semiconductor laser driving current is generated based on a first target value and the output power of the semiconductor laser represented by the received light receiving signal is a first power level, Generating a correction second driving current that is smaller than the first semiconductor laser driving current in the second semiconductor laser driving current, which is a second power level higher than the first power level, based on a second target value, A third compensating driving current which is smaller than the first semiconductor laser driving current in the third semiconductor laser driving current and whose power is a third power level higher than the second power level, ; And In the first mode, the first semiconductor laser driving current is output, the first semiconductor laser driving current and the correction second driving current are added and output in the second mode, and in the third mode, And a step of adding and outputting the first semiconductor laser driving current and the correction third driving current.