JP3418268B2 - Semiconductor laser controller - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser control device used in the fields of laser printers, digital copying machines, optical disk devices, optical communication devices and the like.

[0002]

2. Description of the Related Art Conventionally known semiconductor lasers are extremely small in size and can be directly modulated at high speed by a driving current, and thus have been widely used in recent years as light sources for laser printers and the like. However, the relationship between the drive current of the semiconductor laser and the light output changes significantly depending on the temperature, which is a problem when trying to set the light intensity of the semiconductor laser to a desired value. Therefore, in the past, AP
Such a problem is solved by using a C (Automatic Power Control) circuit. APC circuits can be classified into the following three types.

The light output of the semiconductor laser is monitored by a light receiving element, and a signal proportional to the light receiving current proportional to the light output of the semiconductor laser generated in the light receiving element and the light emission level command signal are always equal to each other so that the light emitting level command signal becomes equal. A method of controlling the optical output of a semiconductor laser to a desired value by an optoelectric negative feedback loop that controls the forward current of the laser.

During the power setting period, the light output of the semiconductor laser is monitored by the light receiving element, and the signal proportional to the light receiving current (proportional to the light output of the semiconductor laser) generated in the light receiving element and the light emission level command signal The forward current of the semiconductor laser is controlled to be equal to each other, while the value of the forward current of the semiconductor laser set in the power setting period is held outside the power setting period to obtain a desired optical output of the semiconductor laser. A method of placing information on the optical output of the semiconductor laser by controlling the value to the value and modulating the forward current of the semiconductor laser set during the power setting period based on the information.

The optical output of the semiconductor laser is measured by measuring the temperature of the semiconductor laser and controlling the forward current of the semiconductor laser or controlling the temperature of the semiconductor laser to be constant according to the measured temperature signal. The method of controlling to a desired value.

In order to set the light output of the semiconductor laser to a desired value, the method is desirable, but the operating speed of the light receiving element,
There is a limit to the control speed due to the limit of the operating speed of the amplification element that constitutes the optoelectronic negative feedback loop. For example, when the crossover frequency in the photoelectric negative feedback loop is taken into consideration as a measure of the control speed, the step response characteristic of the optical output of the semiconductor laser should be approximated by the following equation when the crossover frequency is f _0. You can

Pout = P ₀ {1-exp (−2πf ₀ t)} Pout: Light output of semiconductor laser P ₀ : Set light intensity of semiconductor laser t: Time In this case, the light output of the semiconductor laser is changed. It is necessary that the total amount of light (integral value of light output ∫Pout) from the time immediately after the time lapse to the set time τ ₀ becomes a predetermined value, ∫Pout = P ₀ · t ₀ {1- [ The expression is 1-exp (-2πf ₀ τ ₀ )] / 2πf ₀ τ ₀ }. If τ ₀ = 50 nS and the allowable error range is 0.4%, f ₀ > 800 MHz must be set, which is extremely difficult.

The method (2) is widely used because it does not cause such a problem and can modulate the semiconductor laser at high speed. However, since the light output of the semiconductor laser is not always controlled, fluctuations in the light amount of the semiconductor laser easily occur due to disturbance or the like. As the disturbance, for example, there is a droop characteristic of a semiconductor laser, and this characteristic easily causes an error of about several percent in the laser light amount.

As an attempt to suppress such a droop characteristic, there has been proposed a method (for example, a method) in which the frequency characteristic of the semiconductor laser drive current is matched with the thermal time constant of the semiconductor laser to compensate. The time constant has individual variations for each semiconductor laser, and there is a problem that it varies depending on the surrounding environment of the semiconductor laser. In addition to this, there is a problem such as a change in the light amount due to the influence of the return light of the semiconductor laser.

As a means for solving such a problem, the present applicant has disclosed, for example, in Japanese Patent Laid-Open No. 20508/1990.
There are those disclosed in Japanese Patent No. 6 and Japanese Patent Application No. 6-103805. First, in the example of Japanese Patent Laid-Open No. 2-205086, the light output of the semiconductor laser is monitored by a light receiving element, and the forward current of the semiconductor laser is constantly controlled so that the light output and the light emission level command signal become equal. An optoelectronic negative feedback loop and a conversion means for converting a light emission level command signal into a forward current of a semiconductor laser, and a sum or difference current of a control current of the optoelectronic negative feedback loop and a current generated by the conversion means. The optical output of the semiconductor laser is controlled by. In this case, the conversion means reduces the control amount of the control current of the optoelectronic negative feedback loop to enable high-speed modulation of the semiconductor laser.

Further, in the example of Japanese Patent Application No. 6-103805, a part of the light output of the semiconductor laser is monitored by the light receiving section to obtain a monitor signal proportional to the light intensity of the light output,
In a semiconductor laser control device that controls the forward current of a semiconductor laser so that the monitor signal and the light emission command signal are equal, an error amplifier that amplifies the difference current between the monitor signal and the light emission command signal, and a proportional to the light emission command signal And a current amplifier that amplifies a signal obtained by adding the output of the error amplifier and the output of the current driver. The forward current of the semiconductor laser is controlled by the output current of the current amplifier. The present invention relates to a semiconductor laser control device configured to do so. In this case, by using a common current amplifier in the output section, it is possible to reduce the current consumption and the chip size when making an IC, and to enable high-speed control.

[0012]

FIG. 16 shows an example of a conventional semiconductor laser control device. This control device includes an error amplifier 1 for amplifying a difference current between a light emission command signal Isig and a monitor signal Im, a current driver 3 for outputting a current proportional to the light emission command signal Isig, an output of the error amplifier 1 and a current drive. The signal obtained by adding the output of section 3 (point a, transistor Q
1 base) and a current amplifier 2 for amplifying the base. Now, the difference current (Isig-Im) between the light emission command signal Isig and the monitor signal Im is charged and discharged by the capacitance Cf, and the voltage Vi is generated. This Vi is amplified by the error amplifier 1 and applied to the base of the transistor Q5.
By applying this to the base, an output signal ΔV ₃ (= AVi, A: voltage amplification factor) is obtained at the collector of the transistor Q5. Further, by applying V ₄ to the base of the transistor Q6, the voltage change ΔV ₂ (=
-R5 · Isig) is generated.

FIG. 17 shows an AC equivalent circuit based on the point a (note that points a, c, R1 and C1 correspond to those in FIG. 16). Here, assuming that the voltage signal applied at the point c is V ₁ , the voltage V ₀ at the point a is V ₀ = V ₁ · Z0 / (Z0 + Z1). The term Z0 / (Z0 + Z1) is R in the low frequency range.
0 / (R0 + R1), C1 / (C0 + C in high frequency range
It can be approximated to 1). In this case, R0 / (R0
When + R1) ≠ C1 / (C0 + C1), V ₀ does not become a perfect rectangular wave even if a rectangular wave is added to V ₁ . For example, in the case of R0 / (R0 + R1)> C1 / (C0 + C1), V 0 becomes a waveform as shown in FIG. 18, the difference between the square wave 4 to the desired delta (hatched ring region), delta = (1 / K) · exp (−t / τ ₀ ) · V ₁ (1) 1 / K = R0 / (R0 + R1) −C1 / (C0 + C1) τ ₀ : time constant t: time. In this case, when 1 / K increases, at the time of rising (t
The voltage difference (1 / K) V ₁ of (= 0) increases, and the desired rectangular wave 4 cannot be obtained. When the waveform as shown in FIG. 18 is applied to the point a in FIG. 16, the operation of the transistor Q1 is delayed and malfunction occurs, or stable operation cannot be performed, which causes a problem in the reliability of the device.

[0014]

Means for Solving the Problems] In the invention of claims 1 to 8, wherein the error amplifier for amplifying the difference current between the monitor signal and the light emission command signal, and a current drive unit that outputs a current proportional to the light emission command signal , A compensator for generating a differential signal from a value proportional to the light emission command signal of the output signal of the current driver, and amplifying a signal obtained by adding the output of the error amplifier, the output of the current driver and the output of the compensator basic structure that to a current amplifier to obtain an output current and the output current of the current amplifier to control a forward current of the semiconductor laser
It is equipped with.

According to the first aspect of the invention, in the above basic structure , the first transistor for changing the emitter current by the current proportional to the light emission command signal and the current proportional to the light emission command signal are the same. A second transistor having a current value and changing the emitter current by a current having a different sign, a first resistor connected to the collector of the first transistor, and a third transistor having a base connected to the first resistor. And a second resistor whose one end is connected to the emitter of the third transistor, a first capacitance which is connected in parallel with the second resistor, and one end of which is connected to the collector of the second transistor. A voltage conversion means having a third resistance and a fourth resistance connected to the other end of the third resistance is provided, and the output of the error amplifier is connected to the second resistance and the first capacitor of the voltage conversion means. A first current conversion means for converting into a current flowing in the shunt is provided, and the compensator includes a fourth transistor having a base connected to the third resistance and a fourth resistance, and a fourth transistor connected to the base. A second capacitance whose one end is connected to the emitter of the transistor, a fifth resistor connected to the other end of the second capacitance, and a voltage between terminals of the fifth resistor, And a second current conversion means for converting into a current flowing through the resistance and the first capacitance, and the second resistance and the first capacitance of the voltage conversion means and the first current on the input side of the current amplifier. The output side of the conversion means and the output side of the second current conversion means were connected . In the invention according to claim 2 , in the above basic structure
In the composition , a first transistor that changes the emitter current by a current proportional to the light emission command signal, and a second transistor that changes the emitter current by a current having the same current value as the current proportional to the light emission command signal but a different sign , A first resistor connected to the collector of the first transistor, a third transistor whose base is connected to the first resistor, and a second resistor whose one end is connected to the emitter of this third transistor And a first capacitance connected in parallel with the second resistor, and a fourth transistor whose base is connected to the emitter of the first transistor,
A fifth transistor whose base is connected to the emitter of the second transistor, a constant current source connected to the emitters of the fourth transistor and the fifth transistor, and a collector of the fourth transistor And a first current conversion means for converting the output of the error amplifier into a current flowing through the second resistance and the first capacitance of the voltage conversion means. , A second capacitance whose one end is connected to the third resistor, a fourth resistor connected to the other end of the second capacitance, and a voltage between terminals of the fourth resistor, A second resistance and a second capacitance of the voltage conversion means on the input side of the current amplifier, and a second current conversion means for converting into a current flowing through the second resistance and the first capacitance. An output side of one current converting means, and connects the output side of the second current converter.

According to a third aspect of the invention, in the second aspect of the invention, the constant current source current varying means for changing the current value of the constant current source is provided.

According to a fourth aspect of the present invention, in the above basic configuration , the first transistor for changing the emitter current by the current proportional to the light emission command signal and the current proportional to the light emission command signal are the same. A second transistor having a current value and changing the emitter current by a current having a different sign, a first resistor connected to the collector of the first transistor, and a third transistor having a base connected to the first resistor. A second resistor having one end connected to the emitter of the third transistor, a first capacitance connected in parallel with the second resistor, and one end connected to the collector of the second transistor. The voltage conversion means having the third resistance and the fourth resistance connected to the other end of the third resistance is provided, and the output of the error amplifier is connected to the second resistance and the first resistance of the voltage conversion means. A first current converting means for converting into a current flowing through the capacitor, and the compensator includes a fourth transistor whose base is connected to the third resistance and the fourth resistance, and an emitter of the fourth transistor. A second capacitance having one end connected to it, a fifth resistor connected to the other end of the second capacitance, a fifth transistor having a base connected to the fifth resistor, and a fifth resistor It has a sixth resistor connected to the emitter of the transistor and a current source connected to the collector of the fifth transistor and flowing a current equal to the offset current value of the collector current. The second resistance and the first capacitance of the means, the output side of the first current conversion means and the collector of the fifth transistor were connected.

According to a fifth aspect of the present invention, in the above basic structure , a first transistor for changing the emitter current by a current proportional to the light emission command signal and a constant current proportional to the light emission command signal. Current variable means for multiplying, a second transistor for changing the emitter current by the output current of the current variable means, a first resistor connected to the collector of the first transistor, and a base connected to the first resistor A third transistor, a second resistor whose one end is connected to the emitter of the third transistor, a first capacitance connected in parallel with the second resistor, and a collector of the second transistor. A voltage conversion means having a third resistance connected to the voltage conversion means, and converting the output of the error amplifier into a current flowing through the second resistance and the first capacitance of the voltage conversion means. Provided one of the current converting means, compensator, a second capacitance having one end to the third resistor is connected,
A first current source for flowing a current proportional to temperature, a fourth transistor having a collector and a base connected to the first current source, and a fourth resistor connected to the emitter of the fourth transistor. A fifth transistor whose base is connected to the base of the fourth transistor, a fifth resistor connected to the emitter of this fifth transistor, and the other end of the collector and second capacitance of the fifth transistor And a sixth transistor having an emitter connected to and a second current source connected to the collector of the sixth transistor and flowing a current equal to the current value of the first current source. On the side, the second resistance and the first capacitance of the voltage conversion means, the output side of the first current conversion means,
The collector of the sixth transistor was connected.

According to a sixth aspect of the invention, in the fifth aspect of the invention, the current source current varying means for changing the current values of the first current source and the second current source is provided.

According to a seventh aspect of the invention, in the fifth aspect of the invention, current source current varying means for varying the current values of the first current source and the second current source, and a light emission command signal of the current varying means. And a ratio changing means for changing a ratio of multiplying the current proportional to the constant by a constant.

According to an eighth aspect of the present invention, in the above basic configuration , the first transistor for changing the emitter current by the current proportional to the light emission command signal and the current proportional to the light emission command signal are the same. A second transistor having a current value and changing the emitter current by a current having a different sign, a first resistor having one end connected to the collector of the first transistor, and a first resistor having a base connected to the first resistor. Three transistors, a second resistance whose one end is connected to the emitter of this third transistor, a first capacitance which is connected in parallel with this second resistance, and the other end of the first resistance And a first current conversion means for converting the output of the error amplifier into a current flowing through the second resistance and the first capacitance of the voltage conversion means. , The compensator includes a fourth transistor whose base is connected to the first resistor and the third resistor, a fourth resistor whose one end is connected to the emitter of the fourth transistor, and the fourth transistor. A second capacitance connected to the other end of the resistance; and a second current conversion means for converting the terminal voltage of the second capacitance into a current flowing through the second resistance and the first capacitance of the voltage conversion means. Have
The second resistance and the first capacitance of the voltage conversion means, the output side of the first current conversion means, and the output side of the second current conversion means were connected to the input side of the current amplifier.

[0022] In the present invention of claim 9, wherein, an error amplifier for amplifying the difference current between the monitor signal and the light emission command signal, and a current drive unit that outputs a current proportional to the light emission command signal, the output of the current driving portions A simulation circuit for simulating, a differential amplifier for outputting a difference signal between the current proportional to the light emission command signal and the output of the simulation circuit, the output of the error amplifier, the output of the current driver and the output of the differential amplifier are added. A current amplifier for amplifying a signal to obtain an output current is provided, and the forward current of the semiconductor laser is controlled by the output current of the current amplifier.

According to a tenth aspect of the present invention, an error amplifier for amplifying a difference current between the monitor signal and the light emission command signal, a current driver for outputting a current proportional to the light emission command signal, and an output of the current driver are provided. A simulation circuit for simulating, a current varying means for multiplying a current proportional to a light emission command signal by a constant, a differential amplifier for outputting a differential signal between the output of the current varying means and the output of the simulation circuit, and an output of an error amplifier. A current amplifier for amplifying a signal obtained by adding the output of the current driver and the output of the differential amplifier to obtain an output current is provided, and the forward current of the semiconductor laser is controlled by the output current of the current amplifier.

[0024]

[Action] In the invention of claims 1 to 8, wherein an output signal proportional to the difference current between the monitor signal and the light emission command signal from the error amplifier, an output signal proportional to the light emission command signal from the current driving portions, The output current of the current amplifier is generated by adding the output signal obtained from the compensator using the difference signal from the value proportional to the light emission command signal of the current driver as the compensation signal, and the forward direction of the semiconductor laser is generated. The current is controlled. By creating the compensation signal by the compensator in this way, it is possible to eliminate the deviation of the output waveform of the current amplifier and create the desired waveform.

According to the first aspect of the present invention, on the input side of the current amplifier, the current flowing through the second resistance and the first capacitance forming the voltage converting means, that is, the current obtained by the first current converting means. A current obtained by adding the current that is generated and the current indicating the compensation signal obtained by the second current conversion unit that constitutes the compensator flows. As a result, the compensation signal amount in the compensator can be controlled with a simple circuit configuration.

According to a second aspect of the invention, a current flowing through the second resistor and the first capacitance, which comprises a constant current source on the input side of the current amplifier and constitutes the voltage conversion means,
That is, the current obtained by the first current conversion means,
A current obtained by adding the current indicating the compensation signal obtained by the second current conversion means forming the compensator flows. In this case, the maximum value of the compensation signal can be set by the current value of the constant current source.

In the third aspect of the invention, the maximum value of the compensation signal in the compensator can be arbitrarily changed by changing the current value of the constant current source using the constant current source current varying means. Becomes

[0028] In the invention of claim 4 is obtained on the input side of the current amplifier, a current flowing through the second resistor and the first capacitor constituting the voltage converting means, i.e., by the first current converting means And a current indicating a compensation signal flowing through the collector of the fifth transistor to which the current source forming the compensator is connected flows.
In this case, by using a current source connected to the collector of the fifth transistor and causing a current equal to the offset current value of the collector current to flow in the compensator, the compensation signal does not include the offset current.

According to a fifth aspect of the present invention, on the input side of the current amplifier, the current flowing through the second resistance and the first capacitance forming the voltage converting means, that is, the current obtained by the first current converting means. And a current indicating a compensation signal that flows through the collector of the sixth transistor to which the first and second current sources that form the compensator are connected. In this case, by using the second current source connected to the collector of the sixth transistor and causing a current equal to the offset current value of the collector current to flow in the compensator, the compensation signal does not include the offset current.
Further, the linearity of the compensation signal can be improved by the current varying means for multiplying the current proportional to the light emission command signal by a constant.

In the sixth aspect of the invention, the time constant of the compensation signal in the compensator is arbitrarily changed by changing the current values of the first and second current sources using the current source current varying means. Can be made.

According to the seventh aspect of the invention, the time constant of the compensation signal in the compensator is arbitrarily changed by changing the current values of the first and second current sources using the current source current varying means. The maximum value of the compensation signal can be arbitrarily changed by changing the ratio of multiplying the current proportional to the light emission command signal of the current changing unit by a constant using the ratio changing unit.

In the eighth aspect of the invention, on the input side of the current amplifier, the current flowing through the second resistor and the first capacitance forming the voltage converting means, that is, the current flowing through the first current converting means is obtained. A current obtained by adding the current that is generated and the current indicating the compensation signal obtained by the second current conversion unit that constitutes the compensator flows. In this case, since the second capacitance is connected to the input side of the second current converting means and functions as a low-pass filter, the compensation signal in the compensator does not include a high frequency component.

[0033] In the invention of claim 9, wherein an output signal proportional to the difference current between the monitor signal and the light emission command signal from the error amplifier, an output signal proportional to the light emission command signal from the current driving portions, emission command The output current of the current amplifier is created by adding the compensation signal from the differential amplifier obtained as the difference signal between the current proportional to the signal and the output of the simulation circuit, and the forward current of the semiconductor laser is controlled. Be seen. In this way, by creating a compensation signal using the simulation circuit and the differential amplifier, it is possible to perform compensation corresponding to device variations, temperature fluctuations, and the like.

According to the tenth aspect of the invention, an output signal proportional to the difference current between the monitor signal from the error amplifier and the light emission command signal, an output signal proportional to the light emission command signal from the current driver, and a light emission command. The output current of the current amplifier is created by adding the compensation signal from the differential amplifier, which is obtained as the difference signal between the output of the current variable means for multiplying the current proportional to the signal by a constant and the output of the simulation circuit, and the semiconductor current is generated. The forward current of the laser is controlled. In this way, by creating a compensation signal using the simulation circuit and the differential amplifier, it is possible to perform compensation corresponding to device variations, temperature fluctuations, and the like. Further, by multiplying the current proportional to the light emission command signal by a constant by using the current varying means, the high frequency component can be removed from the compensation signal.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment forming a basic configuration of the present invention will be described with reference to FIGS. 1 and 2 (corresponding to the invention described in claims 1 to 8 ). FIG. 1 shows the configuration of a semiconductor laser control device. Optical output Po of semiconductor laser 5 (hereinafter referred to as LD)
Part of the photodiode 6 as a light receiving portion (hereinafter, P
Error amplifier 1 for amplifying the difference current between the monitor signal Im and the light emission command signal Isig, which is proportional to the light intensity obtained by monitoring with (D)), and the current driver for outputting the current ΔIa proportional to the light emission command signal Isig. 3 and this current driver 3
Compensation device 7 for generating a differential signal (compensation signal) ΔIb from a value proportional to the light emission command signal Isig of the output signal of, and a current amplifier 2 for obtaining an output current (forward current) I _LD .

The operation of this apparatus having such a configuration will be described. A part of the optical output Po of the LD 5 is received by the PD 6, and the monitor signal I proportional to the optical intensity of the LD 5
m is induced. In the error amplifier 1, the light emission command signal Isi
The difference current Isig-Im between g and the monitor signal Im is amplified, and the output value is ΔI ₁ (= A1 (Isig-Im), A
1: current amplification factor of error amplifier 1). LD5 and P
An optoelectric negative feedback loop is formed by D6, the error amplifier 1, and the current amplifier 2, and the forward current I _{LD of the LD 5} is controlled so that the light emission command signal Isig and the monitor signal Im become equal. In this case, the forward current I _LD is shown as a signal obtained by adding ΔI ₁ which is the output value of the error amplifier 1, ΔIa which is the output value of the current driver 3 and ΔIb which is the output value of the compensator 7. be able to. In this way, the output value ΔIb from the compensator 7 is changed to the output value ΔIb of the current driver 3.
The output value ΔI of the current driver 3 is added to a.
The deviation from the desired value of a can be significantly improved.

The reason why the deviation of the output value ΔIa of the current driver 3 from the desired value can be improved by providing the compensator 7 will be described below. The waveform of ΔIa of the current driver 3 is as shown in FIG. On the other hand, the waveform of ΔIb (compensation signal) of the compensator 7 is as shown in FIG.
The waveform is such that the waveform of ΔIa as in (b) is interpolated. Now, ΔIa of the current driver 3 and ΔI of the compensator 7
The sum of b and ΔI ₂ (= k · Isig, k: proportional constant). This ΔI ₂ indicates the signal after compensating the output value of the current driver 3. The value of k is set in advance. And
An addition current of ΔI _{1 of the} error amplifier 1, ΔIa of the current driver 3 and ΔIb of the compensator 7 is added to the current amplifier 2,
It is converted into the forward current I _LD of the _{LD 5} and the laser output of the _{LD 5} is controlled. The forward current I _{LD at} this time is I _LD = Ao · (ΔI ₁ + ΔIa + ΔIb) = Ao · (ΔI ₁ + ΔI ₂ ) = Ao · (A1 (Isig −Im) + k · Isig) (2) By making ΔIb by the compensator 7 in this way, the difference Δ from the value proportional to the light emission command signal Isig
The laser output can be controlled by compensating (see the equation (1)). As a result, the waveform of the forward current I _LD can be an ideal output waveform (rectangular wave), malfunction can be eliminated, and high-speed processing can be performed.

However, the value of k in the equation (2) is set in advance based on the following concept.
That is, in general, the optical output Po of the LD 5 is approximated as Po = η · (I _LD −I _th ) η: differential quantum efficiency I _th : LD threshold current. The monitor current Im is LD5
When the coupling coefficient between PD and PD6 is α and the radiation sensitivity of PD6 is S, it can be expressed as Im = αSPo = αSη · (I _LD −I _th ) = αSη · (Ao · (ΔI ₁ + ΔI ₂ ) −I _th. Therefore, the light emission command signal Isi
The magnitude of the output ΔI ₂ of the current driver 3 after compensation, which is proportional to g, that is, the value of the proportional constant k is Ao · ΔI ₁ = I _th
Then, the light output / forward current characteristic of the LD 5 is set so that the light emission command signal Isig and the monitor current Im become equal.
It is set in advance based on the coupling coefficient between the LD 5 and the PD 6 and the optical input / received signal characteristics of the PD 6. That is, here, the value of k is set in advance so that k = 1 / aSηAo.

As described above, the signal ΔI ₁ proportional to the difference current between the monitor signal Im obtained from the error amplifier 1 and the light emission command signal Isig and the signal ΔIa proportional to the light emission command signal Isig obtained from the current driver 3. And the light emission command signal I
By using the sum of the three signals with the compensation signal ΔIb obtained from the compensator 7 which is a differential signal from a value proportional to sig as the forward current I _LD which is the output current of the current amplifier 2, the current amplifier 2 It is possible to greatly improve the deviation of the output current from the desired value, and it is possible to obtain a stable laser output at high speed.

Next, a first embodiment of the present invention will be described with reference to FIG. 3 (corresponding to the invention of claim 1 ). The description of the same parts as those of the above-described embodiment having the basic configuration is omitted, and the same reference numerals are used for the same parts.

First, the overall structure of this apparatus will be described with reference to FIG. This device includes an error amplifier 1, a current driver 3,
It is roughly divided into a compensator 7, a current amplifier 2, and a voltage converter 8 as a voltage converter.

The voltage conversion unit 8 includes a first transistor Q6 for changing the emitter current by a current proportional to the light emission command signal Isig, and an emitter having a current having the same current value as the current proportional to the light emission command signal Isig but having a different sign. A second transistor Q8 for changing the current, a first resistor R5 connected to the collector of the first transistor Q6,
A third transistor Q2 having a base connected to the first resistor R5, a second resistor R1 having one end connected to an emitter of the third transistor Q2, and a second transistor R1 connected in parallel with the second resistor R1. The first capacitance C1
The third resistor R9 has one end connected to the collector of the second transistor Q8, and the fourth resistor R8 connected to the other end of the third resistor R9. In addition,
The emitter of the transistor Q8 has a transistor Q9
And a current source 9a for flowing -Isig2 are connected. The transistor Q7 has an emitter connected to the transistor Q7,
The current source 9b for flowing Isig2 is connected.

A first current converter 10 is provided as a first current converter for converting the output of the error amplifier 1 into a current flowing through the resistor R1 and the capacitance C1 of the voltage converter 8. The first current converter 10 includes transistors Q5, Q4, Q3, resistors R4, R3, R2, capacitances C4, C3, C2, and a diode D1.

The compensator 7 has a fourth transistor Q10 whose bases are connected to the resistors R9 and R8, a second capacitance C5 whose one end is connected to the emitter of the fourth transistor Q10, and a second capacitance C5. A fifth resistor R11 connected to the other end of the second capacitance C5 and a voltage across the fifth resistor R11 are converted into a current flowing through the second resistor R1 and the first capacitance C1 of the voltage conversion unit 8. Second current conversion section 11 as second current conversion means
It is composed of and. This second current converter 11
Is a transistor Q11, Q12, Q13 and a resistor 1
2, R13, R14 and capacitances C6, C7, C
8 and.

The current amplifier 2 includes transistors Q1 and Q0.
And resistors R7 and RE. Then, at the base of the transistor Q1 on the input side of the current amplifier 2, the resistor R1 and the capacitance C1 of the voltage conversion unit 8, the collector of the transistor Q3 on the output side of the first current conversion unit 10, and the second The output side of the current converter 11 is connected to the collector of the transistor Q13. The apparatus is configured in this way.

The operation inside the compensator 7 through which the compensation signal Icomp flows will be mainly described below. In the voltage conversion unit 8, a current Isig2 (= −γk · Isig proportional to the light emission command signal Isig
, K, which is a proportional constant, is set in advance) is V ₄
Then, the emitter current of the transistor Q6 applied at is changed to generate a voltage change ΔV ₂ between the terminals of the resistor R5.
Further, the current −Isig (inversion signal of Isig2) changes the emitter current of the transistor Q8 applied at V ₄ ,
Between the terminals of the resistor R8 and the resistor R9 connected in series-
Change the voltage by ΔV ₂ (however, R8 + R9 = R5
And Q8 and Q6 are the same transistor). This voltage change is divided by the resistors R8 and R9, and the voltage change ΔVd at the point d is ΔVd = −R8 / (R8 + R9) · ΔV ₂ . Further, the resistor R11 and the capacitance C5 in the compensator 7 form a bypass filter, and the voltage change ΔVe at the point e is ΔVe = jωτ ₁ / (1 + jωτ ₁ ) · ΔVd τ ₁ = C5 · R11.

On the other hand, in the current driver 3 having the first current converter 10, the input impedance of the error amplifier 1 is high impedance, and the light emission command signal Isi.
The difference current Isig-Im between g and the monitor signal Im is charged and discharged by the capacitance Cf, and the voltage Vi is generated. This voltage Vi is amplified by the error amplifier 1 and the transistor Q
5 base. When the output signal of this error amplifier 1 is ΔV ₃ , ΔV ₃ = AVi = −A · (Isig −Im) / jωCf A: The voltage amplification factor of the error amplifier. Further, the transistors Q3 and Q4 and the resistors R2 and R3 in the first current converter 10 form a current mirror circuit. Here, for simplification, R2 and R
Assuming that the resistance value of 3 and the sizes of Q3 and Q4 are the same, and that D1 is composed of the same transistor as Q3 and Q4 and the variations in the characteristics are the same, the drive current I is I = (Vcc-V ₃ -3Vbe) / become (R3 + R4) ... (3 ).

Further, the second current converter 11 in the compensator 7
, The transistors Q12 and Q13, the resistor R13,
R14 (for simplicity, R13 = R14) constitutes a current mirror circuit, and the compensation current Icomp is Icomp =
Become _{(Vcc-V 6 -3Vbe) /} (R12 + R13).
The value of Icomp and the value of the drive current I of the equation (3) are added to the point a. Accordingly, the voltage Va at the point a becomes _{Va = Vcc-V 2 -Vbe-} R1 · I-R1 · Icomp. Here, for example, 2R1 = R3 + R4, 2R1
= Selecting resistance such that R12 + R13, Va = (1/2 ) V 3 + (1/2) V 6 -V 2 + 2Vbe , and the influence of variation in the power supply voltage Vcc eliminated. This V
The point a to which a is applied is ΔIa in FIG. 1 described above.
This corresponds to the current addition point of (the driving current I here) and ΔIb (here Icomp).

The value I + Icomp thus synthesized at the point a is input to the base of the transistor Q1 on the input side of the current amplifier 2 so that the forward current I _LD of the LD5 is applied to the collector of the transistor Q0. Flowing. This I _LD is expressed as I _LD = ((1/2) V ₃ + (1/2) V ₆ + V ₂ ) / RE. Incidentally, by setting the V _3, V _6, V ₂ of the bias voltage stable reference (d) is a source, stable unaffected by variations in temperature change and characteristic variations and Vbe of the power supply voltage Vcc Offset current flows.

The voltage change ΔVa at point a is ΔVa = − ((1/2) ΔV ₃ + (1/2) ΔVe−ΔV ₂ ′) = − ((1/2) ΔV ₃ − (1 / 2) jωτ ₁ / (1 + jωτ ₁ ) · R8 / (R8 + R9) · ΔV ₂ −ΔV ₂ ′) (4) However, ΔV ₂ ′ is a signal that is deviated from ΔV _{2 by} the difference Δ of the equation (1). Thus, ΔV ₂ ′ can be expressed as ΔV ₂ ′ = ΔV ₂ −Δ = ΔV ₂ − (1 / K) · exp (−t / τ ₀ ) · ΔV ₂ (5). From equations (4) and (5), satisfy the conditional equation of (1/2) R8 / (R8 + R9) = 1 / K = R0 / (R0 + R1) -C1 / (C0 + C1) C5 · R11 = τ ₀ By setting the value,
The voltage change ΔVa at point a is ΔVa = − ((1/2) ΔV ₃ −ΔV ₂ ). Thereby, the forward current I _LD for controlling the laser output flowing through the _{LD 5} is I _LD = − ((1/2) ΔV ₃ −ΔV ₂ ) / RE = − (− (1/2) A · (Isig− Im) / jωCf + R5 · Isig2) / RE = ((1/2) A · (Isig−Im) / jωCf + R5 · γk · Isig) / RE (6) The formula (6) has the same form as the formula (2),
The circuit of FIG. 3 can realize the circuit of FIG.
Therefore, from this, by adding the compensation signal Icomp, which is the output from the compensator 7, to the drive signal I, which is the output of the current driver 3, at the point a, the desired value of the output of the current driver 3 is obtained. Can be improved, and the waveform of the forward current I _LD of the _{LD 5} can be made an ideal output waveform (rectangular wave).

The resistor R1 serves as a low-pass filter with the parasitic capacitance Cx such as the collector capacitance of the transistor Q3.
Since this impedes speeding up, the capacitance C1 (C1 >> Cx) is connected in parallel with the resistor R1 to reduce the influence of the parasitic capacitance and speed up. Similarly, the resistors R2, R3, and R4 have capacitances C2 and C, respectively.
By connecting 3 and C4 in parallel, high speed operation can be achieved. Further, the transistors Q7, Q9 and the resistors R6, R10 to which the voltage V5 is applied as a base are for allowing a constant emitter current to flow as a bias current in the transistors Q6, Q8, respectively, and show linearity when Isig2 is small. Can be improved.

Next, a second embodiment of the present invention (corresponding to the invention of claim 2 wherein) which will be described with reference to FIG.
It should be noted that description of the same parts as those in the above-mentioned embodiment is omitted,
The same reference numerals are used for the same portions.

The voltage converter 8 includes a first transistor Q6 for changing the emitter current by a current proportional to the light emission command signal Isig, and an emitter with a current having the same current value as the current proportional to the light emission command signal Isig but having a different sign. A second transistor Q8 for changing the current, a first resistor R5 connected to the collector of the first transistor Q6,
A third transistor Q2 having a base connected to the first resistor R5, a second resistor R1 having one end connected to an emitter of the third transistor Q2, and a second transistor R1 connected in parallel with the second resistor R1. The first capacitance C1
A fourth transistor Q14 whose base is connected to the emitter of the first transistor Q6, and a second transistor Q14.
A fifth transistor Q15 whose base is connected to the emitter of 8, a constant current source 12 connected to the emitters of the fourth transistor Q14 and the fifth transistor Q15, and a collector of the fourth transistor Q14. The third resistor R15 is connected to the third resistor R15. The emitter of the transistor Q6 and the transistor Q1
A current source 9b for flowing Isig2 is connected to the base of No. 4. Transistor Q8 emitter and transistor Q
A current source 9a for flowing -Isig2 is connected to the base of 15. A resistor R16 is connected to the collector of the transistor Q15. A transistor Q9 and a resistor R10 are connected to the emitter side of the transistor Q8,
A resistor R8 is connected to the collector of the transistor Q8. A transistor Q7 and a resistor R6 are connected to the emitter side of the transistor Q6.

The compensator 7 has a second capacitance C5 having one end connected to the third resistor R15 and a fourth resistor R11 connected to the other end of the second capacitance C5.
And the voltage between the terminals of the fourth resistor R11 is converted to the voltage conversion unit 8
And a second current converter 11 that converts the current into a current flowing through the second resistor R1 and the first capacitance C1. The second current converter 11 includes transistors Q11, Q12, Q13 and resistors 12, R13, R1.
4 and capacitances C6, C7 and C8.

At the point a on the input side of the current amplifier 2, the second resistor R1 and the first capacitance C1 of the voltage converter 8 are provided.
Is connected to the output side of the first current converter 10 and the output side of the second current converter 11 of the compensator 7. The apparatus is configured in this way. In FIG. 4, the circuits of the error amplifier 1, the first current converter 10, and the current driver 3 are omitted.

Hereinafter, the voltage converter 8 having the constant current source 12 will be described.
And the operation inside the compensator 7 through which the compensation signal Icomp flows. Transistors Q6 and Q8 in the voltage conversion unit 8
Is a current Isig2, -I proportional to the light emission command signal Isig.
sig2 and the bias current I1 is flowing as the emitter current, respectively, when an equal bias current I1, the base-emitter voltage Vbe _6, Vbe ₈ of the transistors Q6, Q8 (the same transistor), Vbe ₆ = V to become _{T · ln ((I1 + Isig2} ) / Is 1) Vbe 8 = V T · ln ((I1-Isig2) / Is 1). Further, the base-emitter voltage Vbe _{14 of} the transistors Q14 and Q15 (assumed to be the same transistor),
Vbe ₁₅ becomes _{Vbe 14 = V T · ln (} (I0-Isig3) / Is 2) Vbe 15 = V T · ln ((I0 + Isig3) / Is 2). However, the emitter currents of the transistors Q14 and Q15 were set to I0-Isig3 and I0 + Isig3, respectively.

On the other hand, the emitter of the transistor Q6 is connected to the base of the transistor Q14, and the emitter of the transistor Q8 is connected to the base of the transistor Q15.
Bases of transistors Q6 and Q8, transistor Q1
4, since the emitter of Q15 are respectively _{connected, Vbe 6 -Vbe 8 = Vbe 15} -Vbe 14 next, the relation of the above equation, the Isig3 = (I0 / I1) Isig2 . In this case, the change in the emitter current of the transistors Q14 and Q15 is proportional to the light emission command signal Isig, and if the current amplification factor of the transistors Q14 and Q15 is sufficiently large,
The emitter currents of the transistors Q14 and Q15 are equal to the collector current. As a result, the voltage change ΔVd of the terminal voltage of the resistor R15 connected to the collector of the transistor Q14 becomes ΔVd = −R15 · Isig3 = −R15 · (I0 / I1) Isig2. As in the second embodiment, the resistor R11 and the capacitance C5 form a high pass filter.
The voltage change ΔVe at the point is ΔVe = jωτ ₁ / (1 + jωτ ₁ ) · ΔVd τ ₁ = C5 · R11, and the compensation signal Ico is the same as in the second embodiment.
Can be converted to mp. Accordingly, the voltage change ΔVa at the point a is ΔVa = − ((1/2) ΔV ₃ − (1/2) jωτ ₁ / (1 + jωτ ₁ ) · R15 · (I0 / I1) Isig ₂ −ΔV ₂ ′) … (7). In this case, since there is a relationship of ΔV ₂ = R5 · Isig2, 1 / K = (1/2) · R15 / R5 · (I0 / I1) C5 · R11 = τ _{0 Further} , in this embodiment, as shown in FIG. The circuit may be provided with constant current source current varying means (not shown) for changing the current value of the constant current source I0. By providing such constant current source current varying means, the current value ratio I0 / I of the equation (7) is obtained.
The ratio of 1 can be arbitrarily changed from the outside, and thus 1 / K can be arbitrarily set. As an example (not shown), the constant current source 12 is replaced by transistors Q7 and Q.
A transistor Q having a base connected to the base of 9 and an external variable resistor Rv having one end connected to the emitter of the transistor Q and the other end grounded. Then, by changing the resistance value of the variable resistor Rv, the current I0 can be arbitrarily changed, whereby 1 / K can be arbitrarily set from the outside.

Next, a third embodiment of the present invention will be described with reference to FIG. 5 (corresponding to the invention of claim 4 ). The description of the same parts as those in the above-mentioned embodiment is omitted, and the same reference numerals are used for the same parts.

The voltage converter 8 includes a first transistor Q6 for changing the emitter current by a current proportional to the light emission command signal Isig, and an emitter having a current having the same current value as the current proportional to the light emission command signal Isig but having a different sign. A second transistor Q8 for changing the current, a first resistor R5 connected to the collector of the first transistor Q6,
A third transistor Q2 having a base connected to the first resistor R5, a second resistor R1 having one end connected to an emitter of the third transistor Q2, and a second transistor R1 connected in parallel with the second resistor R1. The first capacitance C1
The third resistor R9 has one end connected to the collector of the second transistor Q8, and the fourth resistor R8 connected to the other end of the third resistor R9. In addition,
A current source 9a for flowing -Isig2, a transistor Q9, and a resistor R10 are connected to the emitter side of the transistor Q8. On the emitter side of the transistor Q6, Isi
Current source 9b for flowing g2, transistor Q7, resistor R6
And are connected.

The compensator 7 has a fourth transistor Q10 whose base is connected to the third resistor R9 and the fourth resistor R8.
A second capacitance C9 having one end connected to the emitter of the fourth transistor Q10, and a fifth resistor R17 connected to the other end of the second capacitance C9.
And a fifth transistor Q16 whose base is connected to the fifth resistor R17, and a fifth transistor Q16
Of the fifth transistor Q16 and a transistor Q18 serving as a current source for supplying a current equal to the offset current value of the collector current of the fifth transistor Q16. The diode D is connected to the collector of the transistor Q18.
3, the resistor R20 is connected. The base of the transistor Q18 is connected to the base of the transistor Q17, and the emitter of the transistor Q17 has a resistor R1.
9 is connected.

At the point a on the input side of the current amplifier 2, the second resistor R1 and the first capacitance C1 of the voltage converter 8 are provided.
Is connected to the output side of the first current converter 10 and the collector of the fifth transistor Q16 of the compensator 7.
The apparatus is configured in this way. Note that FIG.
The circuit configurations of the error amplifier 1, the first current converter 10, and the current driver 3 are omitted.

Hereinafter, the operation in the compensator 7 including the transistor Q18 in which the compensation signal Icomp flows will be mainly described. First, the DC operation in the compensator 7 will be described. The bases of the transistors Q17 and Q18 are biased to the same potential. Assuming that the emitter currents of the transistors Q17 and Q18 are I1 and I2, respectively, and they are substantially equal, the base-emitter voltages are also substantially equal, and the relational expression of the inter-terminal voltage of R19.I1 = R20.I2 + V _D3 V _D3 : D3 is established. Large current amplification factor of the transistor Q17,18 enough, when the emitter current and the collector current are equal, the voltage between the terminals of the resistor R17 connected to the collector of the transistor Q17 is, R17 · I1, and this voltage the transistor Q16 Applied to the base of. Accordingly, assuming that the emitter current of the transistor Q16 is I3 (assuming that the current amplification factor is sufficiently large and the emitter current and the collector current are equal) and the base-emitter voltage is Vbe ₁₇ , R17 · I1 = Vbe ₁₇ + R18 · I3 The relational expression holds. In this case, set D3 to transistor Q
16 and the same transistor, R19 = R17,
If R20 = R18, then I2 = I3.

Here, the AC operation in the compensator 7 will be described. Similarly to the first embodiment, the voltage change ΔVe at point e is ΔVe = −jωC9 · R17 / (1 + jωC9 · R17) · R8 / (R8 + R9) · ΔV ₂ . This ΔVe is applied to the base of the transistor Q16, the collector current of the transistor Q16 changes,
This current change is ΔI3. And the transistor Q
Assuming that the difference between the collector current of 18 and the collector current of the transistor Q16 is the compensation signal Icomp, Icomp = (I3 + ΔI3) −I2 = ΔI3 = ΔVe / R18. When this Icomp is added to the point a, the potential V at the point a
a becomes _{Va = Vcc-V 2 -Vbe-} R1 · I-R1 · Icomp. However, I is similar to the equation (3). here,
In this embodiment, since the Icomp no offset, if R1 = R3 + R4, the _{Va = V 3 -V 2 + 2Vbe} -R1 · Icomp. As a result, the potential change ΔVa at the point a becomes ΔVa = − (ΔV ₃ + R1 · Icomp−ΔV ₂ ′). If the difference Δ from ΔV _{2 of} ΔV ₂ 'is Δ = −R1 · Icomp = R1 / R18 · jωC9 · R17 / (1 + jωC9 · R17) · R8 / (R8 + R9) · ΔV ₂ , that is, 1 By setting each value so that / K = R1 / R18 · R8 / (R8 + R9) C9 · R17 = τ ₀ , the forward current I _LD flowing through the LD5 having the same shape as the equation (2) can be obtained. it can. By providing the transistor Q18 which is a current source in this way, a current equal to the offset current value of the collector current of the transistor Q16 can flow in the compensator 7. As a result, the compensation signal Icomp does not include an offset current, which facilitates the circuit design for DC operation. Therefore, from the above, the deviation of the output of the current driver 3 from the desired value can be improved, and the waveform of the forward current I _LD of the _{LD 5} can be made an ideal output waveform (rectangular wave).

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 6 and 7 (corresponding to the invention of claim 5 ). The description of the same parts as those in the above-mentioned embodiment is omitted, and the same reference numerals are used for the same parts.

In FIG. 6, the voltage converter 8 multiplies the first transistor Q6, which changes the emitter current by the current proportional to the light emission command signal Isig, and the current proportional to the light emission command signal Isig by a constant (-α). Current source 13 as a current varying means for flowing -αIsig2, a second transistor Q8 that changes the emitter current by the output current of the current source 13, and a first resistor connected to the collector of the first transistor Q6. R5, a third transistor Q2 having a base connected to the first resistor R5, a second resistor R1 having one end connected to an emitter of the third transistor Q2, and a second resistor R1. It is composed of a first capacitance C1 connected in parallel and a third resistor R8 connected to the collector of the second transistor Q8. A transistor Q9 and a resistor R10 are connected to the emitter side of the transistor Q8. A current source 9b for flowing Isig2, a transistor Q7, and a resistor R6 are connected to the emitter side of the transistor Q6.

The compensator 7 has a second capacitance C10 whose one end is connected to a third resistor R8, a first current source J1 for supplying a current proportional to temperature, and a first current source J1.
A fourth transistor Q whose collector and base are connected to
19, a fourth resistor R21 connected to the emitter of the fourth transistor Q19, and a fourth transistor Q1.
Fifth transistor Q whose base is connected to base 9
20, a fifth resistor R22 connected to the emitter of the fifth transistor Q20, and a fifth transistor Q2.
A sixth transistor Q21 having an emitter connected to the collector of 0 and the other end of the second capacitance C10, and a current equal to the current value of the first current source J1 connected to the collector of the sixth transistor Q21. And a second current source J2 to flow.

At the point a on the input side of the current amplifier 2, the second resistor R1 and the first capacitance C1 of the voltage converter 8 are provided.
The output side of the first current converter 10 is connected to the collector of the sixth transistor Q21 of the compensator 7.
The apparatus is configured in this way. Note that FIG.
The circuit configurations of the error amplifier 1, the first current converter 10, and the current driver 3 are omitted.

Hereinafter, the compensator 7 in which the voltage converter 8 having the current source 13 and the compensation signal Icomp having the current source J2 flows.
I will focus on the internal operations. The current sources J1 and J2 are current sources that supply the same current I1, and the transistor Q1
9, Q20 and resistors R21, R22 form a current mirror circuit, and the collector current of the transistor Q20 is I1. The bias voltage V7 is applied to the base of the transistor Q21, and the current amplification factor is sufficiently large.
The emitter current and the collector current are equal (I2). Since the output resistance of the transistor Q20 is large enough,
A high pass filter is formed by the capacitance C10 and the emitter resistance re of the transistor Q21. As a result, the current I flowing through the collector of the transistor Q21
2, I2 = I1 + (1 / re) · jωC10 · re / (1 + jωC10 · re) · αΔV 2 However, re = kT / q · I1 k: Boltzmann constant q: a temperature (K): elementary charge T . R5 = R8 and the current value applied to the emitter of the transistor Q8 is -αIsig2 (or R5 = αR
8). In this case, re becomes constant with respect to temperature by using the current sources J1 and J2 that flow currents in which I1 is proportional to temperature T. The compensation signal Icomp in the compensator 7, Icomp = I2-I1 = ( 1 / re) · jωτ 1 / (1 + jωτ 1) · αΔV 2 τ 1 = C10 · re next, thereby 1 / K = αR1 / Re ... (9) C10 · re = τ ₀ (10) By setting the respective values, it is possible to obtain the forward current I _LD flowing through the _{LD 5} having the same shape as the equation (2). By providing the current source J2 in this way, a current equal to the offset current value of the collector current of the transistor Q21 can flow in the compensator 7. As a result, the offset signal is not included in the compensation signal Icomp, and the circuit design for DC operation is further facilitated. In addition, the light emission command signal I
By providing the current source 13 for multiplying the current proportional to sig by a constant (-α), linearity is improved by setting α so that Icomp is sufficiently smaller than I ₁ . Therefore, from the above, the deviation of the output of the current driver 3 from the desired value is improved, and the forward current I of the LD 5 is reduced.
_{The LD} waveform can be an ideal output waveform (rectangular wave).

Here, temperature-dependent current sources J1 and J2
The circuit configuration of will be described. As shown in FIG.
The current sources J3 and J4 respectively have a temperature independent I0,
It is a current source that supplies a current of 2I0. Transistor Q
22, Q23 and resistors R23, R24 form a current mirror circuit (transistors Q22, Q23 are transistors of the same size). The current mirror circuit 14 is connected to the collector side current source J4 of the transistor Q23, and the current mirror circuit 15 is connected to the output side of the current mirror circuit 14. In this case, the current mirror circuit 14 includes transistors Q24 and Q2.
5, Q26 and resistors R25, R26, and R27. When the size of the transistor Q24 is 1, the size of the transistor Q26 is m, and R25 = m27.
And The current mirror circuit 15 includes transistors Q27, Q28, Q29, Q30, and resistors R28, R.
29, R30, R31, and when the size of the transistor Q27 is 1, the transistor Q29,
When the size of Q30 is m ', R28 = m'R30 = m'R
31.

Now, assuming that the base-emitter voltages of the transistors Q22 and Q23 are Vbe ₀ and Vbe ₁ , respectively, and the collector current of the transistor Q23 is I2, Vbe ₀ + R23 · I0 = Vbe ₁ + R24 · I2 ∴V _T · ln ( I0 / Is) + R23 · I0 = V _T · ln (I2 / Is) + R24 · I2 ∴V _T · ln (I0 / I1) = R24 · I2-R23 · I0 where R24 = nR23, for example, R24 = ( 1 /
When 2) R23, I2 = 2I0 + ΔI0 Toke, delta = the ΔI0 / I0«1 _{that, -V T · ln (2 +} Δ) = 1/2 · R0 (2I0 + ΔI0) -R0 · I0 ∴ -2V T · ln2- the _{V T · ΔI0 / I0 = R0} · ΔI0 (R0 + re0) ΔI0 = -2V T · ln2. However, it was re0 = V _T / I0. here,
If R0 >> re0 (for example, when I0 = 1 mA, r0
e0 = 26Ω (T = 300K), and ΔI0 = −2ln2 / R0 · k / q · T. As a result, the current ΔI0 becomes a current proportional to the temperature T. Such a circuit is used as a current mirror circuit 14,
If connected to 15, the current sources J1, J as shown in FIG.
2 can be obtained. As a result, the current I1 becomes I1 = mm ′ · 2ln2 / R0 · k / q · T, which is a current proportional to the temperature.

Next, a fifth embodiment of the present invention will be described with reference to FIGS. 8 and 9 (corresponding to the invention of claims 6 and 7 ). The description of the same parts as those in the above-mentioned embodiment is omitted, and the same reference numerals are used for the same parts.

This embodiment is the same as the above-mentioned fourth embodiment (see FIG. 6).
See) circuit. First, FIG.
The circuit configuration of the current source current varying means 16 for changing the current value I1 flowing in each of the current sources J1 and J2 is shown. The operation of the current source current varying means 16 will be described below. Transistors Q30, Q31, Q32, Q33, Q
34 and Q35 are differential switches. Transistor Q
If the size of 25-1 is 1, the transistor Q25-
The sizes of 2, Q25-3 are 2, 4 respectively. Further, the resistors R27-1, R27-2, R27-3
Letting Ia0, Ia1, and Ia2 be the currents flowing in the respective lines, Ia1 = 2Ia0 and Ia2 = 4Ia0. The current Ia0 flows to the transistor Q31 when D0 is at the L (Low) level, and the current Ia0 when D1 is at the L level.
a1 flows to the transistor Q33, which causes the current I
a = Ia0 + Ia1. In this way, the current Ia and further the current I1 are changed by D0 to D2. Ia0, I
Since a1 and Ia2 are currents proportional to temperature, the current I
1 is a current proportional to temperature and can be changed digitally from the outside. If the current I1 can be set arbitrarily, by using the current sources J1 and J2, (10)
Re can be set arbitrarily from the relationship of the equation, and by this, the time constant τ ₀ of the compensation signal Icomp can be adjusted.

FIG. 9 shows a current source 13 (current varying means, FIG.
2) shows the circuit configuration of the ratio varying means 17 for changing the ratio of multiplying the current proportional to the light emission command signal Isig by a constant (α). The operation of the ratio varying means 17 will be described below. A current of I0 always flows through the collector of the transistor Q50 due to the feedback of the transistor Q54, and the collector current of the transistor Q51 becomes I1-I0. However, there is a relation of I1 ≧ I0. Also, the transistor Q
Assuming that the current flowing through the collector of 53 is Ia, the collector current of the transistor Q52 becomes IT-Ia, and V _T · ln (I0 / Is) −V _T · ln (Ia / Is) = V _T · ln ((I1- _{I0) / is) -V T ·} ln ((iT-Ia) / is) of the relationship is established. However, transistors Q50 to Q5
3 is a transistor of the same size, and IT is a current proportional to temperature.

∴ I0 / Ia = (I1−I0) / (IT-Ia) ∴ Ia = I0 / I1 · IT On the other hand, when a current equal to I0 is supplied as the emitter current of the transistors Q55 and Q56, the transistor Q5
The collector currents of Q5 and Q56 are I2 and I0-I, respectively.
2 (I0 ≧ I2) and the collector current of the transistor Q58 is Ib, the collector current of the transistor Q58 becomes −Isig2−Ib, and Ib = I2 / I0 · (−Isig2) holds. Ia and Ib are I1. -ΑI
If used as sig2, 1 / K = I2 / I0 · R1 · I0 / I1 · qIT / kT ∴ 1 / K = I2 / I1 · K1 where K1 = R1 · qIT / kT (IT∝ T). Further, from the equation (10), τ0 = C10 · I0 / I1 · qIT / kT ∴τ0 = C10 · I0 / I1 · K2, where K2 = qIT / kT (IT∝T). As a result, I0, I1. By arbitrarily setting the value of I2 from the outside (I1 ≧ I0 ≧ I2), the compensation signal Icomp (= I2-I1, see FIG. 6) can be adjusted, whereby the maximum value of the compensation signal Icomp can be adjusted. It can be set arbitrarily.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. 10 and 11 (corresponding to the invention of claim 8 ). The description of the same parts as those in the above-mentioned embodiment is omitted, and the same reference numerals are used for the same parts.

The voltage converter 8 includes a first transistor Q6 for changing the emitter current by a current proportional to the light emission command signal Isig, and an emitter with a current having the same current value as the current proportional to the light emission command signal Isig but having a different sign. A second transistor Q8 that changes the current, and a first resistor R whose one end is connected to the collector of the first transistor Q6.
31, a third transistor Q2 whose base is connected to the first resistor R31, and a third transistor Q2
Second resistor R1 having one end connected to the emitter of, a first capacitance C1 connected in parallel with the second resistor R1, and a third resistor connected to the other end of the first resistor R31. And R30. In addition, on the emitter side of the transistor Q8, a current source 1 that flows -Isig2 '
9a, the transistor Q9, and the resistor R10 are connected. Isig2 'is provided on the emitter side of the transistor Q6.
Current source 19b, a transistor Q7, and a resistor R6.
And are connected.

The compensator 7 has a fourth transistor Q whose base is connected to the first resistor R31 and the third resistor R30.
36, a fourth resistor R28 having one end connected to the emitter of the fourth transistor Q36, and a fourth resistor R28.
Second capacitance C11 connected to the other end of 28
And a second current converter 11 for converting a voltage across the second capacitance C11 into a current flowing through the second resistor R1 and the first capacitance C1 of the voltage converter 8.
It is composed of and. This second current converter 11
Is a current source 18, a transistor Q37, and a resistor R29.
It has and. The current source 18 supplies a current I1 equal to the bias current flowing through the collector of the transistor Q37.

At the point a on the input side of the current amplifier 2, the second resistor R1 and the first capacitance C1 of the voltage converter 8 are provided.
Is connected to the output side of the first current converter 10 and the output side of the second current converter 11 of the compensator 7. The apparatus is configured in this way. In FIG. 10, the circuit configurations of the error amplifier 1, the first current converter 10, and the current driver 3 are omitted.

The operation in the compensator 7 in which the compensation signal Icomp having the second capacitance C11 flows will be mainly described below. In the voltage conversion unit 8, a current Isig2 ′ obtained by multiplying the current Isig2 proportional to the light emission command signal Isig by a constant changes the emitter current of the transistor Q6, and the voltage change ΔV is generated between the terminals of the resistors R30 and R31 connected in series.
_{Raises 1} . This ΔV ₁ is represented as ΔV ₁ = (R30 + R31) · Isig2 ′. Then, the signal R30 · Isig2 ′ obtained by dividing this ΔV ₁ by the resistors R30 and R31 causes a voltage change ΔVe at the point e via the low pass filter constituted by the transistor Q36 and the resistor R28 and the capacitance C11. . This ΔVe is ΔVe = 1 / (1 + jωτ ₁ ) · R30 · Isig2 ′ τ ₁ = R28 · C11. Here, the collector of the transistor Q37 is connected to the current source I1 that flows a current I1 equal to the bias current flowing through the collector, so that the compensation signal Icomp
Is Icomp = 1 / (1 + jωτ ₁ ) · R30 / R29 · Isig2 ′. On the other hand, ΔV ₁ is ΔV ₁ ′ = ΔV ₁ −1 / K · exp (−t / τ ₀ ) · ΔV ₁ = (1-1 / K) ΔV ₁ + 1 / K {1-exp (− t / τ ₀ )} ΔV ₁ . Thus, as shown in FIG. 11, when the desired value ΔV ₂ of the output waveform is ΔV ₂ {= (R30 + R31) Isig2}, ΔV ₂ = (1-1 / K) ΔV ₁ is satisfied, and the compensation signal Icomp is used. Only the difference Δ (hatched area in FIG. 11) Δ = 1 / K {1-exp (−t / τ ₀ )} ΔV ₁ needs to be subtracted. That is, by setting the values so that Isig2 '= K / (K- 1) Isig2 1 / K = R30 / (R30 + R31) · R1 / R29 τ 1 = R28 · C11 = τ 0, (2) formula It is possible to obtain the forward current I _LD flowing through the _{LD 5} having the same shape as the above. By connecting the capacitance C11 to the input side of the transistor Q37 in this way, it is possible to have a function as a low-pass filter, and the compensation signal Icomp in the compensator 7 does not include a high frequency component. Therefore, from the above, the deviation of the output of the current driver 3 from the desired value can be improved, and the waveform of the forward current I _LD of the _{LD 5} can be made an ideal output waveform (rectangular wave). In addition, Isig
2 '= Isig2, and the resistance value of the resistors R30 and R31 is K /
You may use what was (K-1) times.

Next, a seventh embodiment of the present invention will be described with reference to FIGS. 12 and 13 (corresponding to the invention of claim 9 ). The description of the same parts as those in the above-mentioned embodiment is omitted, and the same reference numerals are used for the same parts.

This apparatus comprises an error amplifier 1 for amplifying a difference current between the monitor signal Im and the light emission command signal Isig, a current driver 3 for outputting a current proportional to the light emission command signal Isig,
A simulation circuit 20 that simulates the output of the current drive unit 3, a differential amplifier 21 that outputs a differential signal between the current proportional to the light emission command signal Isig and the output of the simulation circuit 20, the output of the error amplifier 1, and the current drive. It is roughly divided into a current amplifier 2 that amplifies a signal obtained by adding the output of the section 3 and the output of the differential amplifier 21 to obtain an output current.

The simulation circuit 20 is a circuit for simulating the output waveform of the output section 22 including the current amplifier 2. The simulation circuit 20 is composed of a transistor Q38, a resistor R32, a capacitance C12, a constant current source 23 for flowing a current I4, and a simulation current amplifier 24. The simulated current amplifier 24 includes transistors Q39 and Q40 and a resistor R3.
3, R34. Also, the output unit 22
Is a current amplifier 2, a transistor Q2, and a resistor R1.
And a capacitance C1.

The differential amplifier 21 includes a transistor Q42,
It is composed of Q43, a resistor R36, and two current sources 21a and 21b for flowing a current I5. The resistor R36 is for expanding the linear operation range, and may be set so that the value of R36 · I5 is larger than the maximum value of the differential voltage. Further, here, the collector of the transistor Q43 is connected to a constant current source 25 for supplying a current I5 for canceling the offset current of the compensation current Icomp.

The collector of the transistor Q43 is connected to the emitter of the transistor Q6. A current source 9b for flowing a current Isig2, a transistor Q7, and a resistor R6 are connected to the emitter side of the transistor Q6. A resistor R5 is connected to the collector of the transistor Q6. The base of the transistor Q6 is connected to the base of the transistor Q8. On the emitter side of the transistor Q8, a current source 9a for flowing a current -Isig2
, The transistor Q9 and the resistor R10 are connected. A resistor R8 is connected to the collector of the transistor Q8. The base of the transistor Q41 is connected between the resistor R8 and the collector of the transistor Q8. A resistor R35 and one end of a capacitance C13 are connected to the emitter of the transistor Q41. The other end of the resistor R35 and the capacitance C13 is connected to the current source 26 for flowing the current I4. The base of the transistor Q43 is connected between the other end of the resistor R35 and the capacitance C13 and the current source 26. The apparatus is configured in this way. Note that the circuit configurations of the error amplifier 1 and the current driver 3 are omitted in FIG.

In general, when the semiconductor laser control device is composed of an IC, the absolute value of each individual element varies greatly, and the input impedance of the current amplifier 2 (in the AC equivalent circuit of FIG. , R0,
C0, which is a value in the range of _{R0 to} h _fe0 · h _fe1 · RE. In h _fe0 and h _fe1 , the current amplification factors of the transistors Q0 and Q1, respectively, greatly fluctuate, and thus the difference from the desired value of the output waveform also largely fluctuates. On the other hand, the compensation signal Ico
Since mp is set by the resistance value and the capacitance, the yield due to device variations decreases. Also,
Even if the compensation signal Icomp is set from the outside, it cannot be said to be perfect, and it is the current situation that it cannot cope with temperature fluctuations.

Therefore, the operation of the present device for dealing with such a problem, in particular, the simulation circuit 20 and the differential amplifier 21.
The operation will be mainly described. Now, assuming that the output resistance of the constant current source 26 and the input resistance of the differential amplifier 21 are sufficiently larger than the input resistance of the simulated current amplifier 24, the resistors R5 and R8.
Assuming that the resistance values are equal, the voltage change ΔVf at point f and the voltage change ΔV ₂ ′ at point a before compensation are ΔVf = −ΔV ₂ ′, and are equal to each other (however, the signs are different).
In the normal case, the relative variation is quite small in the IC, so if the simulation circuit 20 and the output unit 22 are configured by the same element, the voltage change ΔVf at the point f is compensated even if the absolute value of each individual element fluctuates. The voltage change ΔV ₂ 'at the previous point a is simulated and is almost equal. On the other hand, the voltage change −ΔV ₂ applied to the base of the transistor Q41 becomes a voltage change ΔVh at the point h, but in the case of the AC equivalent circuit as shown in FIG. 17, R0 becomes R1 (here, R35). Therefore, if the capacitance of the capacitance C13 is set sufficiently larger than C0, ΔVh and −ΔV ₂ are ΔVh≈−ΔV ₂ , and there is almost no difference between the two. Note that R35 = R3
2. If the value of the constant current source is I4, D at points f and h
The C potential becomes equal.

Then, ΔVf and ΔVh are fed to the differential amplifier 2
If it is input to 1, the difference between them, that is, the difference from the desired value at point a, is output from the transistor Q43. This output value is added to the output unit 22 as the compensation signal Icomp.
As a result, it is possible to perform compensation in accordance with the variation in the output waveform from the desired value, which occurs due to variations in devices, temperature variations, and the like. Therefore, from the above, the deviation of the output of the current driver 3 from the desired value is improved, and the LD 5
Of the forward current I _LD of the ideal output waveform (rectangular wave)
Can be Note that here, the compensation signal Icomp
Is added to the emitter of the transistor Q6, but it may be added to the point a as in the above-described embodiments.

FIG. 13 shows a modified example of the simulated current amplifier 24. In the circuit of FIG. 12 described above, the simulated current amplifier 24 has the same configuration as that of the current amplifier 2.
Has a resistance value of about 10Ω (ΔV ₂ ≈500 mV, I _LD ≈5
When it is 0 mA, RE≈10Ω), which is often an external component, and it is difficult to configure R34 = RE in the circuit in FIG. 12 in the chip. Therefore, the simulated current amplifier 24 is configured as shown in FIG.
By _{setting 40≈h fe0} · RE, it can be easily configured as a chip component.

Next, an eighth embodiment of the present invention will be described with reference to FIGS. 14 and 15 (corresponding to the invention of claim 10 ). The description of the same parts as those in the above-mentioned embodiment is omitted, and the same reference numerals are used for the same parts.

The circuit of FIG. 14 showing the configuration of the present device is basically the same as the circuit of the seventh embodiment (see FIG. 12) described above, but here, the current proportional to the light emission command signal Isig2 is used. Are connected to the emitter side of the transistors Q6 and Q8 as current variable means for multiplying (1 + 1 / α) by a constant.

The operation of the circuit will be described below. Now, as the input signal, a signal obtained by multiplying the current proportional to the light emission command signal Isig2 by a constant (1 + 1 / α) is used, and the voltage is converted by the resistors R37 and R38 satisfying the relationship of R37 + R38 = R5 and R37 = αR38. The voltage (1 + 1 / α) ΔV ₂ generated by this,
When ΔV ₂ is applied to the bases of the transistors Q38 and Q41, respectively, the voltage waveform ΔVf at the point f of the simulation circuit 20,
ΔVh at point h is as shown in FIG. However, ΔV ₂
= R5 · Isig2 Then, the differential amplifier 21 generates a difference ΔVcomp between ΔVf and ΔVh, converts this value into a compensation signal Icomp, and adds it to the emitter current of the transistor Q6. As a result, the voltage change ΔVi between the terminals of the resistor R5 on the collector side of the transistor Q6 is obtained, and the waveform at the point a has almost no deviation from the desired value. As a result, it is possible to perform compensation in accordance with the variation in the output waveform from the desired value, which occurs due to variations in devices, temperature variations, and the like. Therefore, from such a thing,
The deviation of the output of the current driver 3 from the desired value is improved, and L
The waveform of the forward current I _LD of D5 can be an ideal output waveform (rectangular wave). Further, in this case, by setting the maximum value of 1 / α ≧ (1 / K) max (1 / K) max: 1 / K, the compensation signal Icomp does not include a high-frequency component, which facilitates circuit design. Become.

[0092]

The invention of claim 1 to 8, wherein according to the present invention includes a signal proportional to the difference current between the monitor signal and the light emission command signal obtained from the error amplifier, signal and proportional to the emission command signal obtained from the current driving portions Since the sum of the three signals of the differential signal from the value proportional to the light emission command signal corresponding to the compensation signal obtained from the compensator is used as the output current of the current amplifier, the output current of the current amplifier is desired. The deviation from the value can be greatly improved, whereby a desired forward current of the semiconductor laser can be obtained and a stable laser output can be obtained at all times.

According to the first aspect of the invention, the input side of the current amplifier has the second resistance and the first capacitance of the voltage converting means, the output side of the first current converting means, and the second current converting means. Since it is connected to the output side, the compensation signal amount of the compensator can be easily controlled, and thus the output current amount of the current amplifier can be controlled with a simple circuit configuration.

According to a second aspect of the present invention, the input side of the current amplifier has a second resistance and a first capacitance of the voltage conversion means having a constant current source, and an output side of the first current conversion means. Since the output side of the second current conversion means is connected, the maximum value of the compensation signal of the compensator can be set by the current value of the constant current source, thereby controlling the output current amount of the current amplifier. The compensation circuit can be easily designed.

According to the third aspect of the present invention, since the constant current source current varying means for changing the current value of the constant current source is provided, the maximum value of the compensation signal in the compensator can be arbitrarily changed from the outside. Thus, the output current amount of the current amplifier can be controlled more accurately.

According to a fourth aspect of the present invention, the input side of the current amplifier has the second resistance and the first capacitance of the voltage converting means, the output side of the first current converting means, and the offset current value of the collector current. Since it is connected to the collector of the fifth transistor having a current source that supplies a current equal to, the compensation signal does not include the offset current, and
It is possible to easily design a circuit for DC operation.

According to a fifth aspect of the present invention, there is provided current varying means for multiplying the current proportional to the light emission command signal by a constant, and the second side and the first capacitance of the voltage converting means are provided on the input side of the current amplifier. Since the output side of the first current conversion means is connected to the collector of the sixth transistor having the first and second current sources for supplying a current equal to the offset current value of the collector current, the offset current is added to the compensation signal. Is not included, and the linearity of the compensation signal is improved, which makes it possible to easily design a circuit for DC operation with a much simpler configuration.

According to the sixth aspect of the present invention, since the current source current varying means for changing the current values of the first current source and the second current source is provided, the time constant of the compensation signal in the compensator is externally set. It can be changed arbitrarily, and thereby the output current amount of the current amplifier can be controlled more accurately.

According to a seventh aspect of the present invention, the current source current varying means for varying the current values of the first current source and the second current source and the current proportional to the light emission command signal of the current varying means are multiplied by a constant. Since the ratio changing means for changing the ratio is provided,
The time constant and the maximum value of the compensation signal in the compensator can be arbitrarily changed from the outside, whereby the output current amount of the current amplifier can be controlled more accurately.

According to the eighth aspect of the present invention, the input side of the current amplifier has the second resistance and the first capacitance of the voltage converting means, the output side of the first current converting means, and the second side of the input side. Since the second current converting means to which the capacitance is connected is connected, the compensation signal does not include a high frequency component, which facilitates the circuit design when increasing the speed.

According to a ninth aspect of the invention, a signal proportional to the difference current between the monitor signal obtained from the error amplifier and the light emission command signal, a signal proportional to the light emission command signal obtained from the current driver, and a light emission command signal. Since the sum of the three signals of the signal corresponding to the compensation signal from the differential amplifier, which is the difference signal between the current proportional to and the output of the simulation circuit, is used as the output current of the current amplifier, variations in the device and It is possible to compensate for temperature fluctuations, etc.
It is possible to always obtain a stable forward current of the semiconductor laser.

According to the tenth aspect of the present invention, a signal proportional to the difference current between the monitor signal obtained from the error amplifier and the light emission command signal, a signal proportional to the light emission command signal obtained from the current driver, and a light emission command signal. Is used as the output current of the current amplifier, which is the difference signal between the output of the current varying means for multiplying the current proportional to the constant by the constant and the output of the simulation circuit and the signal corresponding to the compensation signal from the differential amplifier. As a result, it is possible to compensate for device variations and temperature fluctuations, and to remove high-frequency components from the compensation signal, which makes it possible to obtain a stable forward current of the semiconductor laser at all times and at high speed. It is possible to facilitate the circuit design at the time of conversion.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a semiconductor laser control device that is a basic embodiment of the present invention.

FIG. 2 is a waveform diagram showing respective waveforms of a signal proportional to a light emission command signal and a compensation signal.

FIG. 3 is a circuit diagram showing a first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention.

FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a current source that depends on temperature.

FIG. 8 is a circuit diagram showing the configuration of a temperature-dependent current source different from that of FIG. 7, which is the fifth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration including means for changing a ratio of multiplying a current proportional to a light emission command signal by a constant.

FIG. 10 is a circuit diagram showing a sixth embodiment of the present invention.

11 is a waveform diagram showing a signal waveform at point a in FIG. 10 and a signal waveform corresponding to a compensation signal.

FIG. 12 is a circuit diagram showing a seventh embodiment of the present invention.

FIG. 13 is a circuit diagram showing a configuration of a simulated current amplifier.

FIG. 14 is a circuit diagram showing an eighth embodiment of the present invention.

FIG. 15 is a waveform diagram showing voltage waveforms at various points in FIG.

FIG. 16 is a circuit diagram showing a configuration of a conventional semiconductor laser control device.

17 is a circuit diagram showing an AC equivalent circuit at point a in FIG.

18 is a waveform diagram showing output waveforms corresponding to the circuit of FIG.

[Explanation of symbols]

1 Error amplifier 2 current amplifier 3 Current driver 5 Semiconductor laser 6 Light receiving part 7 compensator 8 Voltage conversion means 10 First current conversion means 11 Second current conversion means 12 constant current source 16 Current source current varying means 17 Ratio conversion means Q6 First transistor Q8 Second transistor Q2 Third transistor R5 first resistance R1 second resistance C1 first capacitance R8, R9, R15 Third resistance R8, R11, R21 Fourth resistance Q10, Q14, Q19 Fourth transistor C5, C9, C10 Second capacitance R11, R17, R22 Fifth resistance Q15, Q16 Fifth transistor R18 sixth resistance Q18 current source J1 First current source J2 Second current source Q21 Sixth transistor

Claims (10)

(57) [Claims] 1. A part of the optical output of a semiconductor laser is received by a light receiving part.
Monitor and monitor signal proportional to the light intensity of its optical output
Signal, and make sure that this monitor signal and the flash command signal are equal.
To control the forward current of the semiconductor laser so that
In a body laser control device, a difference current between the monitor signal and the light emission command signal is amplified.
Error amplifier, and a current driver that outputs a current proportional to the light emission command signal
And is proportional to the light emission command signal of the output signal of the current driver.
A compensator for generating a differential signal from the output, the output of the error amplifier, the output of the current driver, and the compensation
The output current is obtained by amplifying the signal obtained by adding the output of the compensator
A current amplifier, a first transistor that changes the emitter current by a current proportional to the light emission command signal, and a second transistor that changes the emitter current by a current having the same current value as the current proportional to the light emission command signal but a different sign. A transistor, a first resistor connected to the collector of the first transistor, a third transistor whose base is connected to the first resistor, and one end of which is connected to the emitter of the third transistor A second resistor, a first capacitance connected in parallel with the second resistor, a third resistor whose one end is connected to the collector of the second transistor, and the other end of the third resistor. A voltage converting means having a fourth resistor connected to the voltage converting means, and an output of the error amplifier flowing through the second resistor and the first capacitance of the voltage converting means. A first current converting means for converting the current into a current , wherein the compensator has a fourth transistor having a base connected to the third resistor and the fourth resistor, and a fourth transistor connected to the base. A second capacitance having one end connected to the emitter of the fourth transistor, a fifth resistance connected to the other end of the second capacitance, and a voltage between terminals of the fifth resistance are converted into the voltage. and a second current converting means for converting the current flowing through the second resistor and the first capacitor means, the input side of the current amplifier, a second resistor and said of said voltage converting means first and one capacitance, and the output side of the first current converting means, to connect the output side of the second current converter means, said semiconductor laser by the output current of the current amplifier
It is characterized in that the forward current of
That semi conductor laser control apparatus. 2. A part of the light output of a semiconductor laser is received by a light receiving portion.
Monitor and monitor signal proportional to the light intensity of its optical output
Signal, and make sure that this monitor signal and the flash command signal are equal.
To control the forward current of the semiconductor laser so that
In a body laser control device, a difference current between the monitor signal and the light emission command signal is amplified.
Error amplifier, and a current driver that outputs a current proportional to the light emission command signal
And is proportional to the light emission command signal of the output signal of the current driver.
A compensator for generating a differential signal from the output, the output of the error amplifier, the output of the current driver, and the compensation
The output current is obtained by amplifying the signal obtained by adding the output of the compensator
A current amplifier, a first transistor that changes the emitter current by a current proportional to the light emission command signal, and a second transistor that changes the emitter current by a current having the same current value as the current proportional to the light emission command signal but a different sign. A transistor, a first resistor connected to the collector of the first transistor, a third transistor whose base is connected to the first resistor, and one end of which is connected to the emitter of the third transistor A second resistor, a first capacitance connected in parallel with the second resistor, a fourth transistor whose base is connected to the emitter of the first transistor, and an emitter of the second transistor. A fifth transistor whose base is connected, and an emitter of the fourth transistor and an emitter of the fifth transistor. And a constant current source, said voltage converting means and a third resistor connected to the collector of the fourth transistor, said second resistor and said first of said voltage converting means the output of the error amplifier comprising a first current converting means for converting the current flowing to the capacitance, wherein the compensator includes a second capacitance having one end connected to the third resistor, the other end of the second capacitance A connected fourth resistance and a second current conversion means for converting a terminal voltage of the fourth resistance into a current flowing through the second resistance and the first capacitance of the voltage conversion means. and, on the input side of said current amplifier, a second resistor and said first capacitance of said voltage conversion unit, and an output side of the first current converting means, and an output side of the second current converter connect the electric It said semiconductor laser by the output current of the amplifier
It is characterized in that the forward current of
That semi conductor laser control apparatus. 3. The semiconductor laser control device according to claim 2, further comprising constant current source current varying means for changing the current value of the constant current source. 4. A part of the optical output of the semiconductor laser is received by the light receiving part.
Monitor and monitor signal proportional to the light intensity of its optical output
Signal, and make sure that this monitor signal and the flash command signal are equal.
To control the forward current of the semiconductor laser so that
In a body laser control device, a difference current between the monitor signal and the light emission command signal is amplified.
Error amplifier, and a current driver that outputs a current proportional to the light emission command signal
And is proportional to the light emission command signal of the output signal of the current driver.
A compensator for generating a differential signal from the output, the output of the error amplifier, the output of the current driver, and the compensation
The output current is obtained by amplifying the signal obtained by adding the output of the compensator
A current amplifier, a first transistor that changes the emitter current by a current proportional to the light emission command signal, and a second transistor that changes the emitter current by a current having the same current value as the current proportional to the light emission command signal but a different sign. A transistor, a first resistor connected to the collector of the first transistor, a third transistor whose base is connected to the first resistor, and one end of which is connected to the emitter of the third transistor A second resistor, a first capacitance connected in parallel with the second resistor, a third resistor whose one end is connected to the collector of the second transistor, and the other end of the third resistor. A voltage converting means having a fourth resistor connected to the voltage converting means, and an output of the error amplifier flowing through the second resistor and the first capacitance of the voltage converting means. Comprising a first current conversion means for converting the flow, wherein the compensator comprises: a fourth transistor having the third and the resistance the fourth base resistor and is connected, the fourth transistor A second capacitance whose one end is connected to the emitter of, a fifth resistor connected to the other end of the second capacitance, and a fifth transistor whose base is connected to the fifth resistor, has a sixth resistor connected to the emitter of the fifth transistor, and a current source for supplying a current equal to the offset current value of the collector current is coupled to the collector of the fifth transistor, an input side of said current amplifier to, said second resistor and said first capacitance of said voltage converting means, connected to the output side of the first current converting means, and a collector of the fifth transistor, before the current amplifier Wherein the output current semiconductor laser
It is characterized in that the forward current of
That semi conductor laser control apparatus. 5. A part of the optical output of a semiconductor laser is received by a light receiving portion.
Monitor and monitor signal proportional to the light intensity of its optical output
Signal, and make sure that this monitor signal and the flash command signal are equal.
To control the forward current of the semiconductor laser so that
In a body laser control device, a difference current between the monitor signal and the light emission command signal is amplified.
Error amplifier, and a current driver that outputs a current proportional to the light emission command signal
And is proportional to the light emission command signal of the output signal of the current driver.
A compensator for generating a differential signal from the output, the output of the error amplifier, the output of the current driver, and the compensation
The output current is obtained by amplifying the signal obtained by adding the output of the compensator
A current amplifier, a first transistor that changes an emitter current by a current proportional to a light emission command signal, a current variable unit that multiplies a current proportional to the light emission command signal by a constant, and an emitter current by an output current of the current variable unit. A second transistor for changing the voltage, a first resistor connected to the collector of the first transistor, a third transistor whose base is connected to the first resistor, and an emitter of the third transistor. Voltage conversion means having a second resistor whose one end is connected to the first resistor, a first capacitance connected in parallel with the second resistor, and a third resistor connected to the collector of the second transistor. When the first current converting means for converting a current flowing through the output of said error amplifier to said second resistor and said first capacitance of said voltage converting means , Comprising a said compensator comprises: a second capacitance the third end to the resistance of is connected, a first current source for supplying a current proportional to temperature, and the collector to the first current source A fourth transistor having a base connected to it, a fourth resistor connected to the emitter of the fourth transistor, a fifth transistor having a base connected to the base of the fourth transistor, and a fifth transistor A fifth resistor connected to the emitter of the transistor, a sixth transistor having an emitter connected to the collector of the fifth transistor and the other end of the second capacitance, and a collector of the sixth transistor. It is connected and a second current source for supplying a current equal to the current value of the first current source, the input side of the current amplifier, said second resistor and said first of said voltage converting means It connects the capacitance, and the output side of the first current converting means, and a collector of the sixth transistor, the semiconductor laser by the output current of the current amplifier
It is characterized in that the forward current of
That semi conductor laser control apparatus. 6. The semiconductor laser control device according to claim 5, further comprising current source current varying means for changing the current values of the first current source and the second current source. 7. A current source current varying means for varying the current values of the first current source and the second current source, and a ratio varying for varying a ratio of a current proportional to the light emission command signal of the current varying means multiplied by a constant. 6. The semiconductor laser control device according to claim 5, further comprising means. 8. A part of the optical output of a semiconductor laser is received by a light receiving portion.
Monitor and monitor signal proportional to the light intensity of its optical output
Signal, and make sure that this monitor signal and the flash command signal are equal.
To control the forward current of the semiconductor laser so that
In a body laser control device, a difference current between the monitor signal and the light emission command signal is amplified.
Error amplifier, and a current driver that outputs a current proportional to the light emission command signal
And is proportional to the light emission command signal of the output signal of the current driver.
A compensator for generating a differential signal from the output, the output of the error amplifier, the output of the current driver, and the compensation
The output current is obtained by amplifying the signal obtained by adding the output of the compensator
A current amplifier, a first transistor that changes the emitter current by a current proportional to the light emission command signal, and a second transistor that changes the emitter current by a current having the same current value as the current proportional to the light emission command signal but a different sign. A transistor, a first resistor whose one end is connected to the collector of the first transistor, a third transistor whose base is connected to this first resistor, and one end of which is connected to the emitter of this third transistor. Voltage conversion means having a second resistance connected to the second resistance, a first capacitance connected in parallel with the second resistance, and a third resistance connected to the other end of the first resistance.
If, anda first current converting means for converting said second resistor and a current flowing through said first capacitance of said voltage converting means the output of said error amplifier, said compensator, said first A fourth transistor whose base is connected to the resistor and the third resistor, a fourth resistor whose one end is connected to the emitter of the fourth transistor, and the other end of the fourth resistor. And a second current conversion means for converting a voltage across the second capacitance into a current flowing through the second resistor and the first capacitance of the voltage conversion means. , to the input side of the current amplifier, said second resistor and said first capacitance of said voltage conversion unit, and an output side of the first current converting means, and an output side of the second current converter connect, before It said semiconductor laser by the output current of the current amplifier
It is characterized in that the forward current of
That semi conductor laser control apparatus. 9. A part of the light output of the semiconductor laser is monitored by a light receiving part to obtain a monitor signal proportional to the light intensity of the light output, and the semiconductor laser is adjusted so that the monitor signal and the light emission command signal become equal. in the semiconductor laser control apparatus for controlling a forward current of the error amplifier for amplifying the difference current between the monitor signal and the emission command signal, and a current drive unit that outputs a current proportional to the light emission command signal, the current a simulation circuit for simulating the output of the drive unit, and the differential amplifier outputs a difference signal between the output of the current and the simulated circuit in proportion to the light emission command signal, the output of the error amplifier and the output of the current driving portions and a current amplifier to obtain an output current by amplifying a signal obtained by adding the output of said differential amplifier, the forward current of the semiconductor laser by the output current of the current amplifier A semiconductor laser control device characterized by being controlled. 10. A part of the light output of the semiconductor laser is monitored by a light receiving part to obtain a monitor signal proportional to the light intensity of the light output, and the semiconductor laser is adjusted so that the monitor signal and the light emission command signal become equal. in the semiconductor laser control apparatus for controlling a forward current of the error amplifier for amplifying the difference current between the monitor signal and the emission command signal, and a current drive unit that outputs a current proportional to the light emission command signal, the current a simulation circuit for simulating the output of the drive unit, and a current varying means for current constant multiple of which is proportional to the light emission command signal, a differential amplifier for outputting a differential signal between the output of the simulation circuit and the output of the variable current means , and a current amplifier to obtain an output current by amplifying a sum signal of the outputs with the differential amplifier of the current driving portions and the output of the error amplifier, the said current amplifier A semiconductor laser control device, wherein the forward current of the semiconductor laser is controlled by an output current.