JP2015201587A - semiconductor laser drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser drive circuit capable of performing APC control at high speed.SOLUTION: The semiconductor laser drive circuit includes: a plurality of semiconductor lasers LD-LDconnected in series; a current source 2 from which currents flow to the plurality of semiconductor lasers; a current source drive circuit 3 which drives the current source to control the currents of the current source; detection means 5 for detecting laser lights from the plurality of semiconductor lasers; a current control element 4 connected from the final semiconductor laser LDamong the plurality of semiconductor lasers to one or more semiconductor lasers including the final semiconductor laser; and a current quantity control circuit 6 which controls the current control element on the basis of output of the detection means to control current quantities of one or more semiconductor lasers.

Description

  The present invention relates to a semiconductor laser driving circuit for driving a plurality of semiconductor lasers.

  In a semiconductor laser driving circuit for driving a plurality of semiconductor lasers, Patent Document 1 provides an APC (auto power control) circuit for each semiconductor laser, and the output of each semiconductor laser is set to a predetermined value by this APC circuit. It is stabilized independently by controlling.

JP 2007-49051 A

  However, Patent Document 1 requires the same number of APC circuits as the number of semiconductor lasers, and the configuration becomes complicated. In addition, when a plurality of semiconductor lasers are connected in series, the drive current is common, so the above-described method cannot be used. If the light amount is adjusted by the APC circuit based on the output of one semiconductor laser, the outputs of the other semiconductor lasers cannot be stabilized.

  In addition, although APC control can be performed on the combined output of all semiconductor lasers, the semiconductor lasers connected in series have a large floating component (for example, stray capacitance) in the drive circuit. APC cannot be controlled at high speed.

  Also, in the semiconductor lasers connected in parallel, for example, floating components are connected and increased in parallel, so that high frequency components are attenuated and APC control cannot be performed at high speed.

  An object of the present invention is to provide a semiconductor laser driving circuit capable of performing APC control at high speed.

  In order to solve the above-described problems, a semiconductor laser driving circuit according to the present invention includes a plurality of semiconductor lasers connected in series, a current source for passing a current through the plurality of semiconductor lasers, and driving the current source. 1 includes a current source driving circuit for controlling the current of the current source, detection means for detecting laser light from the plurality of semiconductor lasers, and a last semiconductor laser to a last semiconductor laser of the plurality of semiconductor lasers. A current control element connected to one or more semiconductor lasers, and a current amount control circuit for controlling a current amount of the one or more semiconductor lasers by controlling the current control element based on an output of the detection means. It is characterized by that.

  The semiconductor laser driving circuit is provided corresponding to the plurality of semiconductor lasers connected in parallel, the voltage source connected to the plurality of semiconductor lasers, and the plurality of semiconductor lasers, and connected in series to the semiconductor lasers. A plurality of connected current control elements, detection means for detecting laser light from the plurality of semiconductor lasers, and the rest excluding one current control element among the plurality of current control elements based on the output of the detection means A drive circuit for supplying current to the remaining semiconductor lasers by driving the current control element, and controlling the one current control element based on the output of the detection means to control the output of the detection means to a predetermined value And a power control circuit.

  The semiconductor laser drive circuit according to the present invention can provide a semiconductor laser drive circuit capable of performing APC control at high speed even when a plurality of semiconductor lasers are connected in series or in parallel.

1 is a block diagram showing a configuration of a semiconductor laser drive circuit according to Example 1 of the present invention. It is a block diagram which shows the structure of the semiconductor laser drive circuit which concerns on the modification of Example 1 of this invention. It is a block diagram which shows the structure of the semiconductor laser drive circuit which concerns on Example 2 of this invention. It is a block diagram which shows the structure of the semiconductor laser drive circuit which concerns on the modification of Example 2 of this invention. It is a block diagram which shows the structure of the semiconductor laser drive circuit which concerns on Example 3 of this invention.

  Hereinafter, embodiments of a semiconductor laser driving circuit of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration of a semiconductor laser driving circuit according to Embodiment 1 of the present invention. This semiconductor laser driving circuit includes a constant current source 2, a current source driving circuit 3, a plurality of semiconductor lasers LD _{1 to} LD _N , a MOSFET 4, a photodiode (PD) 5, and a current amount control circuit 6a.

The plurality of semiconductor lasers LD _{1 to} LD _N are connected in series, and the current source 2 is connected to the anode (one end) of the LD ₁ of the first semiconductor laser. The current source 2 supplies a constant current to the plurality of semiconductor lasers LD _{1 to} LD _N.

The current source drive circuit 3 controls the current of the current source 2 by driving the current source 2. The photodiode 5 corresponds to the detection means of the present invention, and detects the combined laser light from the plurality of semiconductor lasers LD _{1 to} LD _N.

MOSFET4 corresponds to the current control device of the present invention, the drain to the anode of the last of the semiconductor laser LD _N of the plurality of semiconductor lasers _LD 1 to Ld _N are connected. The source of the MOSFET 4 is connected to a reference potential, for example, ground. The gate of the MOSFET 4 is connected to the current amount control circuit 6a.

Current control circuit 6a controls the current amount of the semiconductor laser LD _N by controlling the MOSFET4 based on the output of the photodiode 5. Further, the current control circuit 6a controls the current amount of the semiconductor laser LD _N by the output of the photodiode 5 is controlled to be a predetermined value.

  Next, the operation of the semiconductor laser drive circuit according to the first embodiment configured as described above will be described with reference to FIG.

First, the current I ₂ from the current source 2 flows through the plurality of semiconductor lasers LD _{1 to} LD _N. The current _{I 2} is branched into a MOSFET4 connected in parallel with the semiconductor laser LD _N. MOSFET4 current _{I 4} flows in, a current flows _(I 2 -I ₄₎ on the semiconductor laser LD _N.

The current I ₄ is determined by controlling the MOSFET 4 by the current amount control circuit 6 a based on the output from the photodiode 5. The current value control of the current source 2 cannot be controlled at high speed because all the semiconductor lasers LD _{1 to} LD _N and the floating components of the wiring are affected.

In contrast, the object of control by the current control circuit 6a, is closed by a small circuit of the semiconductor laser LD _N and MOSFET 4, because the floating component is small, thereby enabling high-speed APC control.

As described above, according to the semiconductor laser drive circuit of the _first embodiment, the entire outputs of the plurality of semiconductor lasers LD _{1 to} LD _N can be controlled using the current source 2. Further, without being affected by stray components of a plurality of semiconductor lasers _LD 1 to Ld _N connected in series, because the APC circuit is closed by a small circuit of the semiconductor laser LD _N and MOSFET 4, the floating component is reduced, APC control can be performed at high speed. Further, in the range of one semiconductor laser LD _N content of the light amount can be APC control.

  Further, since feedback is applied at high speed from the photodiode 5 to the current amount control circuit 6a, low-speed noise can be removed.

FIG. 2 is a block diagram showing a configuration of a semiconductor laser drive circuit according to a modification of the first embodiment of the present invention. In Example 1 shown in FIG. 1, to adjust the amount of light using a semiconductor laser LD _N only MOSFET 4.

On the other hand, in the modification of the first embodiment, the drain of the MOSFET 4 is connected to the anode of the second semiconductor laser LD _N-1 including the last semiconductor laser LD _N from the last semiconductor laser LD _N. .

According to a variant of the first embodiment, current _{I 2} flows through the plurality of semiconductor lasers _LD 1 _{to Ld N-2,} the current _{I 4} flows in MOSFET 4, the semiconductor laser _{LD N-1,} LD _N current _{(I 2} -I ₄₎ flows. As a result, APC control can be performed at high speed in the light quantity range corresponding to the two semiconductor lasers LD _N-1 and LD _N.

  Further, the floating component to be controlled by the current amount control circuit 6b changes depending on the point at which the current from the current source 2 is branched. For this reason, it is possible to perform APC control with the maximum light amount adjustment width by selecting a branch point capable of realizing APC control in a desired band.

In the modification of the first embodiment, the end of the semiconductor laser LD is _N and diverts the current in the two second semiconductor laser LD _N-1 of the anode from the semiconductor of 3 or more counted from the end of the semiconductor laser LD _N The current may be branched at the anode of the laser.

  FIG. 3 is a circuit diagram showing a configuration of the semiconductor laser drive circuit according to the second embodiment of the present invention. The semiconductor laser drive circuit shown in FIG. 3 is characterized in that the current source drive circuit 3a controls the current of the current source 2 based on the laser light from the photodiode 5 as compared to the semiconductor laser drive circuit shown in FIG. .

The current source driving circuit 3a can process the current of the current source 2 at a low speed to increase the range of the amount of light. Further, the current control circuit 6c, a range of one semiconductor laser LD _N content of the light amount can be APC control at high speed.

  FIG. 4 is a circuit diagram showing a configuration of a semiconductor laser driving circuit according to a modification of the second embodiment of the present invention. The semiconductor laser drive circuit shown in FIG. 4 is characterized in that the current source drive circuit 3a controls the current of the current source 2 based on the laser light from the photodiode 5 as compared with the semiconductor laser drive circuit shown in FIG. .

The current source driving circuit 3a can process the current of the current source 2 at a low speed to increase the range of the amount of light. Further, the current amount control circuit 6d enables APC control at high speed in the light amount range corresponding to the two semiconductor lasers LD _N-1 and LD _N.

FIG. 5 is a circuit diagram showing a configuration of a semiconductor laser driving circuit according to Embodiment 3 of the present invention. This semiconductor laser driving circuit has a plurality of semiconductor lasers LD _{1 to} LD _N , a plurality of MOSFETs Q _{1 to} Q _N , an LD driving circuit 10, amplifiers 11 and 12, an APC circuit 13, and a voltage source Vcc.

The plurality of semiconductor lasers LD _{1 to} LD _N are connected in parallel, and a voltage source Vcc is connected to the anodes of the plurality of semiconductor lasers LD _{1 to} LD _N. The plurality of MOSFETs Q _{1 to} Q _N correspond to the current control element of the present invention, are provided corresponding to the plurality of semiconductor lasers LD _{1 to} LD _N , and are connected in series to the corresponding semiconductor lasers.

The photodiode 5 corresponds to the detection means of the present invention, and detects laser light from the plurality of semiconductor lasers LD _{1 to} LD _N. The LD driving circuit 10 drives the MOSFETs Q _{1 to} Q _N-1 via the amplifier 11 based on the output of the photodiode 5, thereby causing a current to flow through the plurality of semiconductor lasers LD _{1 to} LD _N−1 .

APC circuit 13 controls the output of the photodiode 5 to the predetermined value by driving the MOSFET Q _N via the amplifier 12 based on the output of the photodiode 5.

According to the semiconductor laser driving circuit of Example 3, by one of the APC circuit 13 only for turning on and off the one MOSFET Q _N, APC control can be faster.

  The present invention can be used for laser devices, laser processing devices, and the like.

2 Constant current source 3 Current source drive circuit 4, Q _{1 to} Q _N MOSFET
5 Photodiode (PD)
6a~6d current control circuit 10 LD driving circuit 11, 12 amplifier 13 APC circuit Vcc voltage source _LD 1 to Ld _N semiconductor laser

Claims (4)

A plurality of semiconductor lasers connected in series;
A current source for passing a current through the plurality of semiconductor lasers;
A current source driving circuit for controlling the current of the current source by driving the current source;
Detecting means for detecting laser light from the plurality of semiconductor lasers;
A current control element connected to one or more semiconductor lasers including the last semiconductor laser from the last semiconductor laser of the plurality of semiconductor lasers;
A current amount control circuit for controlling a current amount of the one or more semiconductor lasers by controlling the current control element based on an output of the detection means;
A semiconductor laser driving circuit comprising:   2. The semiconductor laser driving circuit according to claim 1, wherein the current amount control circuit controls the output of the detecting means to a predetermined value.   3. The semiconductor laser driving circuit according to claim 1, wherein the current source driving circuit controls the current of the current source to a constant value based on the output of the detecting means. A plurality of semiconductor lasers connected in parallel;
A voltage source connected to the plurality of semiconductor lasers;
A plurality of current control elements provided corresponding to the plurality of semiconductor lasers and connected in series to the semiconductor lasers;
Detecting means for detecting laser light from the plurality of semiconductor lasers;
A drive circuit for causing a current to flow through the remaining semiconductor laser by driving the remaining current control elements excluding one of the plurality of current control elements based on the output of the detection means;
A power control circuit for controlling the output of the detection means to a predetermined value by controlling the one current control element based on the output of the detection means;
A semiconductor laser driving circuit comprising:

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