JPS62154335A - Semiconductor laser driving circuit - Google Patents

Abstract

PURPOSE:To make feedback control possible at the time of recording and to obtain stable light emission power by providing a light emission power holding circuit that holds the value at the time of recording power light emission during recording period and the value at the time of recording power light emission immediately before the emission at the time other than the time of recording power light emission, and a correction detecting circuit that outputs the amount of driving of a semiconductor laser. CONSTITUTION:At the time of reproducing, the output of a power detecting circuit 1 and the output of a reproduction power setting circuit 2 are added to the input of a control circuit 3. Terminals (c) and (b) of the first switching circuit 5 are closed, and the control circuit 3 controls so as to make two inputted signals equal, and a semiconductor laser 7 emits light stably at light emission power set by the reproduction power setting circuit 2. At this time, the second switching circuit 13 is opened, and the second driving circuit is not operating. Thus, the feedback control of driving of the semiconductor laser at high frequency can be made by a simple circuit configuration by utilizing the characteristic of the semiconductor laser, and recording power can be stabilized.

Description

【発明の詳細な説明】 産業上の利用分野 本発明はディスクに光学的に情報を記録し、再生する光
学式情報記録再生装置に用いる半導体レーザ駆動装置に
関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser drive device used in an optical information recording/reproducing device for optically recording and reproducing information on a disk.

従来の技術 従来の技術を第２図、第３図を参照して説明する。第２
図は半導体レーザの電流対光出力特性を示すが温度依存
性が高く、定電流駆動では一定出力を得ることは困難で
ある。このため半導体レーザ後方光を検出し駆動回路に
フィードバックをかけることが行われている。−力先学
的記録装置における半導体レーザ駆動回路は、情報を読
取る再生時に低パワーの一定出力になるように動作し、
情報を書込む記録時には高鳴・くワーと低・くワーの発
光を高速に繰り返す必要がある。しかしながら単純に温
度補償用のフィードパ、クループをもった定出力回路に
変調回路を付加しただけでは一般てフィードバックルー
ズの時定数が大きいため変調信号に比例した発光パワー
を得ることは困難である。Prior Art The conventional technology will be explained with reference to FIGS. 2 and 3. Second
The figure shows the current vs. optical output characteristics of a semiconductor laser, but it is highly temperature dependent, and it is difficult to obtain a constant output with constant current drive. For this reason, the backward light of the semiconductor laser is detected and feedback is applied to the drive circuit. - The semiconductor laser drive circuit in the force-based recording device operates to provide a constant low power output during reproduction to read information,
When recording information, it is necessary to repeat high-pitched and low-pitched light emissions at high speed. However, simply adding a modulation circuit to a constant output circuit having a feedper and a loop for temperature compensation makes it difficult to obtain light emitting power proportional to the modulation signal because the feedback loose time constant is generally large.

以下この問題に対応した従来例とその問題点を第３図に
沿って説明する。A conventional example dealing with this problem and its problems will be explained below with reference to FIG.

第３図は従来の半導体レーザ駆動回路のブロック図を表
わしている。再生時には、第１の切換え回路５は端子す
とＣが閉じており、第２の切換え回路１３は開いている
。半導体レーザ７の光出力は、その後方光がパワー検出
回路１により検出され、制御回路３及び第１の駆動回路
６により半導体レーザの駆動電流が制御される。よって
このフィードバック制御により再生パワーが周囲温度に
対して安定化される。つぎに記録時には第１の切換え回
路６は端子ａとｂが閉じ、第２の切換え回路１３が閉じ
る。FIG. 3 shows a block diagram of a conventional semiconductor laser drive circuit. During playback, the first switching circuit 5 has terminal C closed, and the second switching circuit 13 is open. The light output from the semiconductor laser 7 is detected by the power detection circuit 1, and the drive current of the semiconductor laser is controlled by the control circuit 3 and the first drive circuit 6. Therefore, this feedback control stabilizes the reproduction power with respect to the ambient temperature. Next, during recording, the terminals a and b of the first switching circuit 6 are closed, and the second switching circuit 13 is closed.

再生時値保持回路４は再生時の制御信号１４を保持しそ
の信号に対応した半導体レーザ駆動電流が流れる。また
この時記録パワー設定回路１１の値に対応した半導体レ
ーザ、駆動電流が重畳され記録パワーで発光する。また
スイッチング回路１２は、記録データにしたがって第２
の駆動回路１０をオン又はオフし半導体レーザ７は記パ
ワーと再生パワーを高速に繰り返すことになる。The reproduction value holding circuit 4 holds the reproduction control signal 14, and a semiconductor laser drive current corresponding to the signal flows. At this time, the semiconductor laser and drive current corresponding to the value of the recording power setting circuit 11 are superimposed and emit light with recording power. Further, the switching circuit 12 switches the second switch according to the recorded data.
By turning on or off the drive circuit 10, the semiconductor laser 7 repeats the recording power and the reproducing power at high speed.

発明が解決しようとする問題点 第３図に示した従来の回路構成では記録時のパワー制御
が行なわれていないため、周囲温度や回路の発熱状態に
より発光パワーが設定した記録パワーよりずれるという
問題がある。Problems to be Solved by the Invention In the conventional circuit configuration shown in Figure 3, power control during recording is not performed, so the problem is that the light emitting power deviates from the set recording power depending on the ambient temperature and the heat generation state of the circuit. There is.

本発明は、かかる点に鑑みてなされたもので再生時のみ
ならず、記録時においてもパワー制御を行い安定したパ
ワー設定が可能な半導体レーザ駆動回路を提供すること
を目的としている。SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor laser drive circuit that can perform power control not only during reproduction but also during recording and can stably set power.

問題点を解決するだめの手段 本発明は上記問題点を解決するため、パワー検出回路の
出力信号に対し記録期間の記録パワー発光時にはその値
を又記録パワー発光時以外にはその直前の記録パワー発
光時の値を保持する発光しくワー保持回路と、記録パワ
ー設定回路の値と発光パワー保持回路の値を比較しその
差を補正する半導体レーザの駆動量を出力する補正量検
出回路を付加する。Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses the value of the output signal of the power detection circuit when the recording power is emitted during the recording period, and the value of the immediately preceding recording power when the recording power is not emitted during the recording period. A light emitting power holding circuit that holds the value at the time of light emission and a correction amount detection circuit that compares the value of the recording power setting circuit and the value of the light emitting power holding circuit and outputs the drive amount of the semiconductor laser to correct the difference are added. .

作　　　用 本発明は、上記した構成により再生時のみならず記録時
においてもフィードバック制御が可能となり安定した発
光パワーが得られる。Effect of the Invention With the above-described configuration, the present invention enables feedback control not only during reproduction but also during recording, and stable light emission power can be obtained.

実癩例 第１図は、本発明の半導体レーザ駆動回路の一実施例を
示すブロック図である。第１図において１は半導体レー
ザの後方光のパワーを検出するパワー検出回路である。Practical Example FIG. 1 is a block diagram showing an embodiment of the semiconductor laser driving circuit of the present invention. In FIG. 1, reference numeral 1 denotes a power detection circuit for detecting the power of the backward light of the semiconductor laser.

再生時にはパワー検出回路１の出力と再生パワー設定回
路２の出力が制御回路３の入力に加わる。第１の切換え
回路５は端子Ｃとｂが閉じており制御回路３は、入力さ
れている２つの信号が等しくなるように制御を行い半導
体レーザ７は再生パワー設定回路２により設定された発
光パワーで安定に発光する。このとき第２の切換え回路
１３は開いており第２の駆動回路は動作していない。During reproduction, the output of the power detection circuit 1 and the output of the reproduction power setting circuit 2 are applied to the input of the control circuit 3. The first switching circuit 5 has terminals C and b closed, and the control circuit 3 controls the two input signals to be equal, and the semiconductor laser 7 has the emission power set by the reproduction power setting circuit 2. It emits light stably. At this time, the second switching circuit 13 is open and the second drive circuit is not operating.

第４図に記録期間における各回路の波形の一例を示す。FIG. 4 shows an example of waveforms of each circuit during the recording period.

第４図記録期間Ａがｔ１〜ｔ６とする。またＣ　は再生
パワー、Ｃ２は記録パワーであり記碌パワー設定回路の
値はＣ２となっている。第２図に示すように半導体レー
ザの電流に対する光出力の関係は、安定にレーザ発光し
ている領域では温度によらずほぼ（Ｐ　　−Ｐｌ　）／
　（ｉ□−１１）＝に（一定）となっている。It is assumed that the recording period A in FIG. 4 is from t1 to t6. Further, C is the reproduction power, C2 is the recording power, and the value of the recording power setting circuit is C2. As shown in Figure 2, the relationship between the optical output and the current of the semiconductor laser is approximately (P - Pl )/in the region where the laser emits light stably, regardless of the temperature.
(i□-11)=(constant).

記録期間Ａのｔ１〜ｔ６の間第１図再生時値保持回路４
はｔ１直前の制御信号１４を保持し、第１の切換え回路
５が端子ａとｂが閉じる。よって半導体しτザ７にはｔ
１直前の再生時の駆動電流が流れる。また第２の切換え
回路１３は閉じる。このとき第２の駆動回路１ｏによっ
て半導体レーザ７に重畳され流れる駆動電流について説
明する。During the period t1 to t6 of the recording period A, the reproduction value holding circuit 4 shown in FIG.
holds the control signal 14 immediately before t1, and the first switching circuit 5 closes terminals a and b. Therefore, as a semiconductor, t
A drive current flows during the previous playback. Also, the second switching circuit 13 is closed. At this time, the drive current that is superimposed and flows through the semiconductor laser 7 by the second drive circuit 1o will be explained.

ｔ１〜ｔ２の間はパワー検出回路１の出力は第４図Ｃに
示すように０１である。発光パワー保持回路８は、ｔ２
までの間は再生パワー０１の値を保持している。また、
記録パワー設定回路１１の出力はＣ２であり補正量検出
回路９は（Ｃ２−０１）に比例した電流値Ｘ・（Ｃ２−
０１）を出力する。Between t1 and t2, the output of the power detection circuit 1 is 01 as shown in FIG. 4C. The light emitting power holding circuit 8
Until then, the value of the reproduction power 01 is held. Also,
The output of the recording power setting circuit 11 is C2, and the correction amount detection circuit 9 outputs a current value X·(C2-01) proportional to (C2-01).
01) is output.

、°’（Ｃ２−０１）の電流が第２の駆動回路１ｏによ
って半導体レーザ７に重畳され流されたとすると、発光
パワーはＣ２−Ｃ，たけ増加し結果的に０２の記録パワ
ーで発光することになる。しかし、この時（１１〜ｔ２
）は、第４図記録データＢは“０”であり実際に記録パ
ワーで発光すべき区間ではない。よって、このときスイ
ッチング回路１２は、第２の駆動回路１ｏの動作をオフ
させ実際に半導体レーザ７には重畳して電流が流れない
。ｔ２〜ｔ３の区間は、実際に記録パワーで発光すべき
区間でありこのときスイッチング回路１２は、第２の、
駆動回路１Ｑの動作をオンさせる。このｔ２〜ｔ３の区
間のパワー検出回路１の出力が第４図Ｃのようになった
とする。本来ならば、補正量検出回路９の出力によって
記録パワー０２になるはずであるが、温度などの影響に
よりΔＣ２だけ増加している。よって補正量検出回路９
は （７（Ｃ２−Ｃ１）−マΔＣ２〕を出力する・発光パワ
ーは回路の時定数により徐々に０２に近づいてくる。第
４図では一例としてｔ３において発光パワーがＣになっ
たとしている。ｔ３〜ｔ４は、第４図記録データＢが“
０゛であり記録パワーで発光すべき区間ではないため、
スイッチング回路１２が第２の駆動回路１０の動作をオ
フし、半導体レーザ７に重畳して流していた電流が流れ
なくなる。よって発光パワーは再生時の０１となる。こ
のとき発光パワー保持回路８は、　ｔ３直前の値を保持
する（第４図ではＣ２）。, °' (C2-01) are superimposed on the semiconductor laser 7 by the second drive circuit 1o, and the emission power increases by C2-C, resulting in light emission with a recording power of 02. become. However, at this time (11~t2
), the recorded data B in FIG. 4 is "0" and is not the section where light should actually be emitted with the recording power. Therefore, at this time, the switching circuit 12 turns off the operation of the second drive circuit 1o, so that no superimposed current actually flows through the semiconductor laser 7. The period from t2 to t3 is the period in which light should actually be emitted at the recording power, and at this time, the switching circuit 12
Turn on the operation of the drive circuit 1Q. Assume that the output of the power detection circuit 1 in the period from t2 to t3 becomes as shown in FIG. 4C. Normally, the output of the correction amount detection circuit 9 should have resulted in a recording power of 02, but it has increased by ΔC2 due to the influence of temperature and the like. Therefore, the correction amount detection circuit 9
outputs (7(C2-C1)-maΔC2). The light emission power gradually approaches 02 due to the time constant of the circuit. In FIG. 4, as an example, it is assumed that the light emission power becomes C at t3. From t3 to t4, the recorded data B in FIG.
Since it is 0゛ and is not the section where light should be emitted at the recording power,
The switching circuit 12 turns off the operation of the second drive circuit 10, and the current superimposed on the semiconductor laser 7 no longer flows. Therefore, the light emission power is 01 during reproduction. At this time, the light emission power holding circuit 8 holds the value immediately before t3 (C2 in FIG. 4).

以後同様な動作を記録期間ｔ１〜ｔ６の間繰り返し、記
録パワーが記録パワー設定回路１１の値Ｃ２に安定する
。Thereafter, similar operations are repeated during the recording period t1 to t6, and the recording power is stabilized at the value C2 of the recording power setting circuit 11.

発明の効果 以上述べてきたように本発明によれば従来の回路構成で
はフィードバック制御不可能な高い周波数における半導
体レーザの駆動を、半導体レーザの特性を利用し簡易な
回路構成でフィートノ＜、ツク制御を行うことができ、
記録パワーの安定が可能となり実用的にきわめて有用で
ある。Effects of the Invention As described above, according to the present invention, it is possible to drive a semiconductor laser at a high frequency, which is impossible to perform feedback control with a conventional circuit configuration, using a simple circuit configuration that utilizes the characteristics of a semiconductor laser. can be done,
This makes it possible to stabilize the recording power and is extremely useful in practice.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明の一実施例における半導体レーザ駆動回
路のブロック図、第２図は半導体レーザの電流対光出力
の特性図、第３図は従来の半導体レーザ駆動回路のブロ
ック図、第４図は本発明の一実施例における各回路の出
力値の時間による変化を示す図である。 １・・・・・・パワー検出回路、２・・・・・再生パワ
ー設定回路、３・・・・・・制御回路、４・・・・・・
再生時値保持回路、５・・・・・第１の切換え回路、６
・・・・・・第１の駆動回路、７・・・・半導体レーザ
、８・・・・・・発光パワー保持回路、９・・・・・・
補正量検出回路、１０・・・・・・第２の駆動回路、１
１・・・・・・記録パワー設定回路、１２・・・・・・
スイッチング回路、１３・・・・・・第２の切換え回路
、１４・・・・・・制御信号、ａ〜ｅ・・・・・・端子
。 代理人の氏名　弁理士　中　尾　敏　男　ほか１名第１
図 再主パフー役疋週発 第２図 、ｍｓ＋ｊ九 １すＬツノ１し 第３図FIG. 1 is a block diagram of a semiconductor laser drive circuit according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of current versus optical output of a semiconductor laser, FIG. 3 is a block diagram of a conventional semiconductor laser drive circuit, and FIG. The figure is a diagram showing changes over time in the output values of each circuit in an embodiment of the present invention. 1...Power detection circuit, 2...Reproduction power setting circuit, 3...Control circuit, 4......
Reproduction value holding circuit, 5...first switching circuit, 6
...First drive circuit, 7...Semiconductor laser, 8...Emission power holding circuit, 9...
Correction amount detection circuit, 10...Second drive circuit, 1
1... Recording power setting circuit, 12...
Switching circuit, 13... Second switching circuit, 14... Control signal, a to e... Terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 from the main role of Puffu, ms + j 91 L horn 1 and Figure 3

Claims (1)

【特許請求の範囲】[Claims] （１）半導体レーザの発光の強さを検出するパワー検出
回路と、再生時に前記パワー検出回路の出力を見ながら
再生パワーとなるよう制御する制御回路と、記録期間前
記制御回路の再生時の出力を保持する再生時値保持回路
と、前記パワー検出回路の出力信号に対し記録期間の記
録パワー発光時にはその値を又記録パワー発光時以外に
はその直前の記録パワー発光時の値を保持する発光パワ
ー保持回路と、記録パワーの設定値と前記発光パワー保
持回路の値を比較しその差を補正する半導体レーメの駆
動量を出力する補正量検出回路と、前記補正量検出回路
出力の駆動量を記録期間再生時の駆動量に重畳しかつ記
録データにより変調し半導体レーザに出力するスイッチ
ング回路とを備えた半導体レーザ駆動回路。（２）パワ
ー検出回路の出力信号に対し記録期間の記録パワー発光
時には発光が安定している区間の値を又記録パワー発光
時以外にはその直前の安定した記録パワー発光時の値を
保持する発光パワー保持回路とした特許請求の範囲第１
項記載の半導体レーザ駆動回路。(1) A power detection circuit that detects the intensity of light emission from a semiconductor laser, a control circuit that controls the reproduction power while monitoring the output of the power detection circuit during reproduction, and an output of the control circuit during reproduction during the recording period. a reproduction time value holding circuit that holds the output signal of the power detection circuit, and a light emission that holds the value when the recording power is emitted during the recording period and the value when the recording power is emitted immediately before when the recording power is emitted for the output signal of the power detection circuit. a power holding circuit; a correction amount detection circuit for outputting a driving amount of a semiconductor laser for comparing a set value of recording power and a value of the light emitting power holding circuit and correcting the difference; A semiconductor laser drive circuit comprising a switching circuit that superimposes the drive amount during playback during a recording period, modulates it with recorded data, and outputs the modulated signal to the semiconductor laser. (2) For the output signal of the power detection circuit, when the recording power is emitted during the recording period, the value in the period where the light emission is stable is held, and when the recording power is not emitted, the value when the light emission is stable immediately before that is held. Claim 1 as a light emitting power holding circuit
The semiconductor laser drive circuit described in .