JP2018093231A - Semiconductor laser drive circuit - Google Patents

Abstract

A semiconductor laser driving circuit capable of APC control at high speed is provided.
A plurality of semiconductor lasers LD1 to LDN connected in series, a current source 2 for passing a current to the plurality of semiconductor lasers, a current source driving circuit 3 for driving a current source and controlling a current of the current source, Detection means 5 for detecting laser light from a plurality of semiconductor lasers, and current control element 4 connected to one or more semiconductor lasers including the last semiconductor laser from the last semiconductor laser LDN among the plurality of semiconductor lasers And a current amount control circuit 6 that controls the current amount of one or more semiconductor lasers by controlling the current control element based on the output of the detection means.
[Selection] Figure 1

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 flowing through the plurality of semiconductor lasers connected in series by controlling the current control element based on an output of the detection means; A current amount control circuit that controls to branch into a current to the laser and a current to the current control element, and the control target by the current amount control circuit is the one or more It closed with a small closed circuit by a conductor laser and said current control element, one end of the closed circuit, characterized in that it is fixed to the reference potential.

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.

  According to the semiconductor laser drive circuit of the present invention, the current flowing through the plurality of semiconductor lasers connected in series with the current amount control circuit is branched into a current to one or more semiconductor lasers and a current to the current control element. To control. The object to be controlled by the current amount control circuit is closed by a small closed circuit composed of a current to one or more semiconductor lasers and a current control element, and one end of the closed circuit is fixed to a reference potential. Since it is small, it is possible to provide a semiconductor laser driving circuit capable of performing APC control at high speed even when a plurality of semiconductor lasers are connected in series.

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 drive circuit includes a constant current source 2, a current source drive circuit 3, a plurality of semiconductor lasers LD1 to LDN, a MOSFET 4, a photodiode (PD) 5, and a current amount control circuit 6a.

  The plurality of semiconductor lasers LD1 to LDN are connected in series, and the current source 2 is connected to the anode (one end) of the LD1 of the first semiconductor laser. The current source 2 supplies a constant current to the plurality of semiconductor lasers LD1 to LDN.

  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 LD1 to LDN.

  The MOSFET 4 corresponds to the current control element of the present invention, and has a drain connected to the anode of the last semiconductor laser LDN among the plurality of semiconductor lasers LD1 to LDN. 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.

  The current amount control circuit 6 a controls the current amount of the semiconductor laser LDN by controlling the MOSFET 4 based on the output of the photodiode 5. The current amount control circuit 6a controls the current amount of the semiconductor laser LDN by controlling so that the output of the photodiode 5 becomes 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 I2 from the current source 2 flows through the plurality of semiconductor lasers LD1 to LDN. This current I2 branches to MOSFET 4 and semiconductor laser LDN connected in parallel. A current I4 flows through the MOSFET 4 and a current (I2-I4) flows through the semiconductor laser LDN.

  The current I4 is determined by controlling the MOSFET 4 by the current amount control circuit 6a 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 LD1 to LDN and the floating components of the wiring are affected.

  On the other hand, the object to be controlled by the current amount control circuit 6a is closed by a small circuit of the semiconductor laser LDN and the MOSFET 4, and the floating component is small, so that high-speed APC control is possible.

  As described above, according to the semiconductor laser driving circuit of the first embodiment, the total output of the plurality of semiconductor lasers LD1 to LDN can be controlled using the current source 2. In addition, since the APC circuit is closed by a small circuit formed by the semiconductor laser LDN and the MOSFET 4 without being affected by the floating components of the plurality of semiconductor lasers LD1 to LDN connected in series, the floating component is reduced and the APC is performed at high speed. Control becomes possible. In addition, APC control can be performed within a range of light quantity corresponding to one semiconductor laser LDN.

  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, only the semiconductor laser LDN uses the MOSFET 4 to adjust the amount of light.

  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 LDN-1 including the last semiconductor laser LDN from the last semiconductor laser LDN.

  According to the modification of the first embodiment, the current I2 flows through the plurality of semiconductor lasers LD1 to LDN-2, the current I4 flows through the MOSFET 4, and the current (I2-I4) flows through the semiconductor lasers LDN-1 and LDN. As a result, APC control can be performed at high speed within the light quantity range of two semiconductor lasers LDN-1 and LDN.

  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 current is branched by the anode of the second semiconductor laser LDN-1 from the last semiconductor laser LDN. However, the anodes of the third or more semiconductor lasers from the last semiconductor laser LDN are used. The current may be branched by.

  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. In addition, the current amount control circuit 6c can perform APC control at high speed within a light amount range corresponding to one semiconductor laser LDN.

  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. In addition, the current amount control circuit 6d enables APC control at high speed in the light amount range corresponding to the two semiconductor lasers LDN-1 and LDN.

  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 LD1 to LDN, a plurality of MOSFETs Q1 to QN, an LD driving circuit 10, amplifiers 11 and 12, an APC circuit 13, and a voltage source Vcc.

  The plurality of semiconductor lasers LD1 to LDN are connected in parallel, and a voltage source Vcc is connected to the anodes of the plurality of semiconductor lasers LD1 to LDN. The plurality of MOSFETs Q1 to QN correspond to the current control element of the present invention, are provided corresponding to the plurality of semiconductor lasers LD1 to LDN, 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 LD1 to LDN. The LD driving circuit 10 drives the MOSFETs Q1 to QN-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 LD1 to LDN-1.

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

  As described above, according to the semiconductor laser driving circuit of the third embodiment, APC control can be performed at high speed only by turning on / off one MOSFET QN by one APC circuit 13.

  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, Q1 to QN MOSFET
5 Photodiode (PD)
6a-6d Current amount control circuit 10 LD drive circuit 11, 12 Amplifier 13 APC circuit Vcc Voltage source LD1-LDN Semiconductor laser

Claims (3)

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;
By controlling the current control element based on the output of the detection means, the current flowing through the plurality of semiconductor lasers connected in series is changed into a current to the one or more semiconductor lasers and a current to the current control element. A current amount control circuit for controlling to branch;
With
A target to be controlled by the current amount control circuit is closed by a small closed circuit including the one or more semiconductor lasers and the current control element, and one end of the closed circuit is fixed to a reference potential. Laser drive circuit.   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.