JP7828233B2 - Laser driving device and laser marking device - Google Patents

Description

This disclosure generally relates to laser driving devices and laser markers. More specifically, this disclosure relates to laser driving devices that emit light from semiconductor lasers, and laser markers that include such laser driving devices.

Patent Document 1 describes a marking mark. The marking mark described in Patent Document 1 has an illumination device that illuminates an object. The illumination device has a light source and an illumination element that receives a light beam from the light source and emits an illumination light beam. The light source emits a light beam under the control of a circuit board. The light beam that enters the illumination element, an illumination mirror, is reflected radially by the outer peripheral surface of the illumination mirror. The light beam reflected from the illumination mirror constitutes an illumination light beam that is irradiated onto an object such as a wall or ceiling. The illumination light beam is emitted in a direction perpendicular to the central axis of the illumination mirror.

Japanese Patent Application Laid-Open No. 2017-152193

In laser markers such as the one described in Patent Document 1, it may be desirable to reduce power consumption.

The purpose of this disclosure is to reduce power consumption.

A laser driving device according to one aspect of the present disclosure includes a voltage conversion unit, a transistor, a detection unit, and a processing unit. The voltage conversion unit boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser. The transistor is connected to the semiconductor laser and adjusts the magnitude of a current flowing through the semiconductor laser. The detection unit detects a voltage between terminals of the transistor. The processing unit controls the magnitude of the DC voltage based on the detection result of the detection unit. The processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of multiple preset target voltage values. The processing unit reduces the magnitude of the DC voltage when the voltage between terminals increases and exceeds a first threshold, and increases the magnitude of the DC voltage when the voltage between terminals decreases and becomes equal to or lower than a second threshold. The first threshold is greater than the second threshold.

A laser driving device according to one aspect of the present disclosure includes a voltage conversion unit, a detection unit, and a processing unit. The voltage conversion unit boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser. The detection unit detects a terminal voltage of the semiconductor laser. The processing unit controls the magnitude of the DC voltage based on the detection result of the detection unit. The processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of a plurality of preset target voltage values. The processing unit reduces the magnitude of the DC voltage when the terminal voltage increases and exceeds a first threshold, and increases the magnitude of the DC voltage when the terminal voltage decreases and becomes equal to or lower than a second threshold. The first threshold is greater than the second threshold.

A laser driving device according to one aspect of the present disclosure includes a voltage conversion unit, a detection unit, and a processing unit. The voltage conversion unit boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser. The detection unit detects a current flowing through the semiconductor laser. The processing unit controls the magnitude of the DC voltage based on the detection result of the detection unit. The processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of a plurality of preset target voltage values. The processing unit reduces the magnitude of the DC voltage when the current increases and exceeds a first threshold, and increases the magnitude of the DC voltage when the current decreases and becomes equal to or less than a second threshold. The first threshold is greater than the second threshold.

A laser driving device according to one aspect of the present disclosure includes a voltage conversion unit, a transistor, a detection unit, and a processing unit. The voltage conversion unit boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser. The transistor is connected to the semiconductor laser and adjusts the magnitude of a current flowing through the semiconductor laser. The detection unit detects the temperature of the semiconductor laser or the transistor. The processing unit controls the magnitude of the DC voltage based on the detection result of the detection unit. The processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of multiple preset target voltage values. The processing unit reduces the magnitude of the DC voltage when the temperature increases and exceeds a first threshold, and increases the magnitude of the DC voltage when the temperature decreases and becomes equal to or lower than a second threshold. The first threshold is greater than the second threshold.

A laser marking device according to one aspect of the present disclosure comprises a laser driving device according to any of the above aspects and an optical system that converts the light emitted from the semiconductor laser into linear light.

This disclosure has the advantage of making it possible to reduce power consumption.

FIG. 1 is a perspective view of a laser marking device according to an embodiment of the present invention with legs opened. FIG. 2 is a perspective view of the laser marking device with the legs closed. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a perspective view of the internal configuration of the laser marking device. FIG. 5 is a perspective view of the optical body of the laser marker. FIG. 6 is an exploded perspective view of a power supply-equipped leg of the laser marker. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 8 is a circuit diagram of a laser driving device provided in the laser marking device. FIG. 9 is a circuit diagram of a laser driving device provided in the laser marking device of the first modified example. FIG. 10 is a circuit diagram of a laser driving device provided in the laser marking device of the second modification. FIG. 11 is a circuit diagram of a laser driving device provided in the laser marking device of the third modification.

The laser driving device and laser marking device equipped with the same according to the embodiments of the present disclosure will be described using the drawings. The drawings described in the following embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

(1) Overview The laser driving device 9 (see Figure 8) of this embodiment is provided in a laser marking device 1 (see Figures 1 to 7) that includes a semiconductor laser 52 and an optical system 53 that converts the light emitted from the semiconductor laser 52 into linear light (laser light L2, L3).

In this example, the laser driver 9 generates DC power from input power supplied from the power supply 90 to be supplied to the semiconductor laser 52. The semiconductor laser 52 is, for example, a laser diode.

As shown in FIG. 8, the laser driving device 9 includes a voltage conversion unit 92, a transistor 951, a detection unit 96, and a processing unit 94.

The voltage conversion unit 92 boosts the input voltage Vin to a DC voltage Vdc that is higher than the input voltage Vin, and outputs the DC voltage Vdc to the semiconductor laser 52.

Transistor 951 is connected to semiconductor laser 52. Here, transistor 951 is connected in series with semiconductor laser 52. Transistor 951 adjusts the magnitude of the current flowing through semiconductor laser 52. Transistor 951 has a first main electrode (collector), a second main electrode (emitter), and a control electrode (base). Here, transistor 951 is used in the active region, and adjusts the magnitude of the current flowing through the series circuit of semiconductor laser 52 and transistor 951 depending on the magnitude of the voltage applied to the control electrode (base).

Detection unit 96 detects the voltage between the terminals of transistor 951. Here, "voltage between the terminals of transistor 951" means the collector-emitter voltage of transistor 951.

The processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96.

In conventional laser markers, the DC voltage generated by the voltage converter is set higher than the value determined by design, taking into account manufacturing errors of parts, etc., so that the semiconductor laser can emit light in the various temperature environments in which the laser marker may be used. As a result, conventional laser markers consume excess (and essentially unnecessary) power.

In contrast, in the laser driving device 9 of this embodiment, the magnitude of the DC voltage Vdc generated by the voltage conversion unit 92 is controlled (adjusted, changed) based on the terminal voltage of the transistor 951 detected by the detection unit 96. If the terminal voltage (collector-emitter voltage) of the transistor 951 is excessive, the processing unit 94 can reduce the magnitude of the DC voltage Vdc. As a result, it is possible to adjust the magnitude of the DC voltage Vdc to the minimum level necessary for the semiconductor laser 52 to emit light at the desired brightness, for example, and to suppress excess power consumption. As a result, the laser driving device 9 of this embodiment can reduce power consumption.

(2) Details The laser driving device 9 according to this embodiment and the laser marking device 1 equipped with the same will be described in detail below with reference to the drawings.

(2.1) Laser Marker First, the structure of the laser marking device 1 will be described with reference to Figures 1 to 8. In the following description, the top, bottom, left, right, front and back of the laser marking device 1 will be basically described as the top, bottom, left, right, front and back of the laser marking device 1 when the laser marking device 1 is installed on a horizontal installation surface.

As shown in FIG. 1, the laser level 1 has multiple (e.g., three) legs 3. With the legs 3 spread apart, the laser level 1 is placed on an installation surface, such as the ground or floor, at a work site (e.g., a home construction site or electrical work site). When installed on an installation surface at the work site, the laser level 1 emits three laser beams: point light L1, which is a point-shaped beam; horizontal line light L2, which spreads horizontally in a fan-like fashion; and vertical line light L3, which spreads vertically in a fan-like fashion. The point light L1 is emitted vertically upward, the horizontal line light L2 is emitted horizontally forward, and the vertical line light L3 is emitted vertically forward. These point light L1, horizontal line light L2, and vertical line light L3 are used as reference points and reference lines to be marked on walls and ceilings during work at the work site (e.g., home construction or electrical work). Hereinafter, the point light L1, horizontal line light L2, and vertical line light L3 may be collectively referred to as laser beams L1-L3.

As shown in Figure 1, the laser marking device 1 comprises a device main body 2 and multiple (three) legs 3. The device main body 2 is the part for emitting laser light L1 to L3. The multiple legs 3 are parts for supporting the device main body 2 on an installation surface. As shown in Figure 2, the laser marking device 1 can be easily carried by closing the multiple legs 3 to form a rod shape.

As shown in Figures 1 and 3, the device main body 2 includes a first housing 4, an optical body 5, a support member 6, and a detection mechanism 7.

As shown in Figures 1 and 3, the first housing 4 includes a body 41 and a base 42.

The body 41 houses the optical body 5, support member 6, and detection mechanism 7. The body 41 is formed, for example, from a light-blocking resin. The body 41 is, for example, approximately cylindrical and includes a peripheral wall portion 411, an upper wall portion 412, and a bottom portion 413 (see Figure 3).

The peripheral wall portion 411 is tubular (e.g., cylindrical). The upper wall portion 412 is provided on the peripheral wall portion 411 so as to close the upper opening of the peripheral wall portion 411, and is, for example, plate-shaped (e.g., disk-shaped). The bottom portion 413 is provided on the peripheral wall portion 411 so as to close the lower opening of the peripheral wall portion 411, and is, for example, plate-shaped (here, disk-shaped). The outer diameter of the lower portion of the body 41 is smaller than the outer diameter of the upper portion of the body 411.

The body 41 has three transmission windows (first transmission window 401 to third transmission window 403) (see Figures 1 to 3). The first transmission window 401 is a transmission window through which the point light L1 is emitted. The first transmission window 401 is, for example, a substantially circular transmission window and is provided in the center of the upper wall portion 412 of the body 41. The second transmission window 402 is a transmission window through which the horizontal line light L2 is emitted. The second transmission window 402 is, for example, a horizontally elongated rectangular transmission window and is provided in the peripheral wall portion 411 of the body 41. The third transmission window 403 is a transmission window through which the vertical line light L3 is emitted. The third transmission window 403 is, for example, a vertically elongated rectangular transmission window and is provided across the upper wall portion 412 and peripheral wall portion 411 of the body 41. The three transmission windows 401 to 403 are made of a transparent material (resin or glass).

The base 42 is fixed to the bottom of the body 41. Multiple legs 3 are rotatably connected to the base 42 (see Figures 1 and 2).

The base 42 is formed, for example, from a light-blocking resin. The base 42 is tubular (e.g., cylindrical) with an open upper end and a bottom. The lower part of the body 41 is inserted into the upper opening of the base 42 and fixed thereto, thereby fixing the base 42 to the body 41 (see Figure 3).

The optical body 5 generates and emits laser beams L1 to L3. As shown in Figures 3 to 5, the optical body 5 includes a case 51, a semiconductor laser 52, an optical system 53, a holder 54, and a vertical support 55.

As mentioned above, the semiconductor laser 52 is a laser diode. The semiconductor laser 52 emits laser light L0 (see Figure 5), which is the source of laser light L1 to L3, to the optical system 53. As shown in Figures 3 and 4, the semiconductor laser 52 is mounted (placed) on a first substrate 56.

The holder 54 positions and holds the semiconductor laser 52 below the optical system 53 (more specifically, below the vertical support portion 55).

The optical system 53 is disposed above the semiconductor laser 52 (more specifically, above the vertical support 55). As shown in Figure 5, the optical system 53 generates laser beams L1 to L3 from the laser beam L0 emitted from the semiconductor laser 52.

As shown in Figures 4 and 5, the optical system 53 has a first beam splitter 531, a second beam splitter 532, a first exit lens 533, and a second exit lens 534. The first beam splitter 531 transmits a portion of the laser light L0 from the semiconductor laser 52, causing it to enter the second beam splitter 532, and reflects the remaining portion, causing it to enter the first exit lens 533. The first exit lens 533 converts the laser light L0 from the first beam splitter 531 into a horizontal line light L2 and emits it. The second beam splitter 532 transmits a portion of the laser light L0 from the first beam splitter 531, causing it to exit vertically (upward) as point light L1, and reflects the remaining portion, causing it to enter the second exit lens 534. The second exit lens 534 converts the laser light L0 from the second beam splitter 532 into a vertical line light L3 and emits it.

The vertical support portion 55 supports the case 51 while being supported by the support member 6 of the device body 2. As shown in Figures 4 and 5, the vertical support portion 55 has a first shaft portion 551 supported by the support member 6 and a second shaft portion 552 that supports the case 51. More specifically, as shown in Figure 3, the vertical support portion 55 is supported by the support member 6 so that it can swing about the first shaft portion 551 and supports the case 51 so that it can swing about the second shaft portion 552 so that the case 51 hangs down vertically. This allows the optical body 5 to always hang down vertically regardless of the inclination of the device body 2. This allows the optical body 5 to always emit laser beams L1 to L3 in the correct directions (vertically upward, forward horizontal, and forward vertical).

As shown in FIG. 5, the vertical support portion 55 is disposed, for example, between the holder 54 and the optical system 53. The vertical support portion 55 has, for example, a rectangular parallelepiped base portion 553, a pair of first shaft portions 551, and a pair of second shaft portions 552. The base portion 553 is, for example, approximately rectangular parallelepiped. The base portion 553 has a through-hole 554 that allows the laser light L0 from the semiconductor laser 52 to pass in the vertical direction. The pair of first shaft portions 551 protrude in the front-rear direction from both the front and rear side surfaces of the base portion 553. The pair of first shaft portions 551 protrude to the outside of the case 51 through a pair of openings 511 (see FIG. 4) in the case 51 and are rotatably supported by a pair of bearings 61 of the support member 6 (see FIG. 3). The pair of second shaft portions 552 protrude in the left-right direction from both the left and right side surfaces of the base portion 553 and are rotatably supported by a pair of bearings 512 (see FIG. 4) in the case 51. The axial direction (front-to-back direction) of the first shaft portion 551 and the axial direction (left-to-right direction) of the second shaft portion 552 are perpendicular to each other.

As shown in Figures 4 and 5, the case 51 houses the semiconductor laser 52, the optical system 53, the holder 54, and the vertical support 55. The case 51 is, for example, a long, vertical rod with a slanted top surface. The optical system 53 is located in the upper part of the interior of the case 51. The vertical support 55 is located below the optical system 53 inside the case 51. The semiconductor laser 52 is located below the vertical support 55 inside the case 51 via the holder 54.

As shown in FIG. 4, the case 51 has three windows (first window 513 to third window 515). The first window 513 to third window 515 are each openings formed in the case 51. The first window 513 is a window through which point light L1 is emitted and is provided on the inclined top surface of the case 51. The second window 514 is a window through which horizontal line light L2 is emitted and is provided on the side surface of the case 51. The third window 515 is a window through which vertical line light L3 is emitted and is provided on the side surface of the case 51. The second window 514 and third window 515 are provided on the side surface of the case 51 that faces the inclined top surface of the case 51.

As shown in FIG. 3 , the support member 6 is fixed to the inner circumferential surface of the body 41 and rotatably supports a pair of first shafts 551 of the vertical support part 55. The support member 6 has an annular portion with a central opening that penetrates vertically, and a pair of bearings 61. The annular portion is fixed to the inner circumferential surface of the body 41. The pair of bearings 61 are components that rotatably support the pair of first shafts 551 of the optical body 5 and are fixed to the annular portion. With the optical body 5 inserted and hanging down in a swingable manner within the central opening of the annular portion, the pair of first shafts 551 of the optical body 5 are rotatably supported by the pair of bearings 61. In this way, the support member 6 supports the optical body 5 so that it swings around the first shafts 551 and hangs down.

The detection mechanism 7 detects whether the lower end of the optical body 5 contacts the inner circumferential surface of the body 41. As shown in FIG. 3 , the detection mechanism 7 has a first contact portion 71 and a second contact portion 72. The first contact portion 71 is a metal component (e.g., a cylindrical component). The first contact portion 71 is fixed to the lower end of the optical body 5. The second contact portion 72 is a metal annular component (e.g., a cylindrical component with a bottom). The second contact portion 72 is disposed at the bottom of the body 41. In this arrangement, the second contact portion 72 is disposed so as to surround the outer periphery of the first contact portion 71 fixed to the lower end of the optical body 5. As a result, when the lower end of the optical body 5 contacts the inner circumferential surface of the body 41, the first contact portion 71 and the second contact portion 72 are electrically connected to each other. In this embodiment, the laser level 1 is equipped with a detection circuit that detects electrical contact between the first contact portion 71 and the second contact portion 72. When the detection circuit detects electrical contact between the first contact portion 71 and the second contact portion 72, it stops the emission of light from the semiconductor laser 52 in the optical body 5.

In other words, if the lower end of the optical body 5 comes into contact with the inner circumferential surface of the body 41, the optical body 5 will no longer be able to hang down accurately in the vertical direction. In this case, the laser marker 1 of this embodiment stops the emission of the semiconductor laser 52 inside the optical body 5. In this way, the laser marker 1 of this embodiment uses the detection mechanism 7 to detect whether the lower end of the optical body 5 has come into contact with the inner circumferential surface of the body 41, and based on the detection result of the detection mechanism 7, the detection circuit stops the emission of the semiconductor laser 52 inside the optical body 5.

As shown in Figure 1, the base 42 is fixed to the bottom of the body 41. Multiple legs 3 are rotatably connected to the base 42. The base 42 is, for example, cylindrical with one end (upper end) open and the other end (lower end) having a bottom. The bottom of the body 41 is inserted into and fixed inside the base 42, thereby fixing the base 42 to the bottom of the body 41 (see Figure 3). Multiple legs 3 are rotatably connected to the lower peripheral edge 421 (see Figure 2) of the bottom of the base 42.

As shown in Figure 1, the multiple (e.g., three) legs 3 are members for supporting the device main body 2 on the installation surface. As shown in Figures 1 and 2, the multiple legs 3 are composed of multiple segments obtained by dividing a tube (e.g., a cylindrical body) into multiple segments (the same number as the number of legs 3) in the circumferential direction.

As shown in Figures 1 and 2, each of the multiple legs 3 has a leg body 31 and a connecting protrusion 32. The leg body 31 has approximately the same shape as one of multiple segments obtained by equally dividing a tube (e.g., a cylindrical body) into multiple segments (the same number as the number of legs 3) in the circumferential direction. The connecting protrusion 32 protrudes upward from the center of the top surface of the leg body 31.

The multiple legs 3 are rotatably connected to the lower peripheral edge 421 of the bottom of the base 42. Each of the multiple legs 3 is rotatable around its first end (upper end) between a direction along the center line M1 of the base 42 (i.e., the first housing 4) (see FIG. 2) and a direction along the inclined line M2 (see FIG. 1). The center line M1 is an imaginary line that passes through the center of the base 42 (i.e., the first housing 4). The inclined line M2 is an imaginary line that is inclined toward the outer periphery of the base 42 with respect to the center line M1 of the base 42.

2, the lower peripheral edge 421 of the bottom of the base 42 is provided with a plurality of (e.g., three) connecting recesses 422 that correspond one-to-one with the plurality of (e.g., three) legs 3. The connecting protrusion 32 of the corresponding leg 3 is disposed in each of the connecting recesses 422. A rotation shaft 423 is disposed within the connecting recess 422. The rotation shaft 423 is parallel to a tangent to the connecting recess 422 on the outer peripheral contour (e.g., circular) of the base 42. The connecting protrusion 32 of the leg 3 is rotatably coupled to the rotation shaft 423. As a result, each of the plurality of legs 3 is coupled to the lower peripheral edge 421 of the base 42 so as to be rotatable around the first end (connecting protrusion 32) between a direction along the center line M1 of the base 42 (first housing 4) and a direction along the inclined line M2.

The multiple legs 3 can be in an open position (along inclined line M2; see Figure 1) or a closed position (along center line M1; see Figure 2). With the multiple legs 3 in an open position, the laser level 1 can be placed upright by placing the second ends (lower ends) of the multiple legs 3 on the installation surface. When the multiple legs 3 are closed, the multiple legs 3 are bundled together and extend along center line M1 of the device body 2, giving the overall shape of the laser level 1 a straight rod shape. This improves the portability of the laser level 1.

One of the multiple legs 3 is a powered leg 300. As shown in Figures 1 and 6, the powered leg 300 further includes a power supply case 33, a power supply holder 34, and a second board 35.

The second board 35 is housed in a housing recess 311 provided on the inner main surface of the leg body 31 of the powered leg 300. At least a transistor 951 is mounted on the second board 35.

The power supply holder 34 is a member that detachably holds the power supply 90. The power supply 90 is a power source for emitting light and controlling the semiconductor laser 52, and is, for example, a dry cell battery (e.g., a size AA battery). The power supply holder 34 has a base portion 341 and a pair of clamping plates 342, 343. The base portion 341 is, for example, a rectangular plate and is fixed to the leg main body 31 so as to cover the opening of the storage recess 311. The pair of clamping plates 342, 343 are used to hold the power supply 90 vertically and protrude from the main surface of the base portion 341 opposite the storage recess 311, leaving a predetermined gap (the length of the dry cell battery) between them in the vertical direction. Terminals for electrical contact with the positive or negative pole of the power supply 90 are arranged on the opposing surfaces of the pair of clamping plates 342, 343. The power supply holder 34 holds multiple (e.g., three) dry batteries as the power supply 90 by sandwiching them in a stacked, parallel arrangement between a pair of clamping plates 342, 343.

The power supply case 33 is a roughly rectangular box with one open surface (opening surface 330). The power supply case 33 houses the power supply holder 34 inside the power supply case 33 and is fixed to the inner main surface of the leg main body 31 so that the opening surface 330 of the power supply case 33 is closed by the inner main surface of the leg main body 31.

The power supply case 33 is divided into two parts, an upper part and an lower part. That is, the power supply case 33 comprises an upper fixed case part 331 and a lower detachable cover part 332. The fixed case part 331 is fixed to the inner main surface of the leg main body 31. The detachable cover part 332 is detachably attached to the inner main surface of the leg main body 31.

In the laser level 1, the multiple legs 3 can be opened (see Figure 1) and the removable cover 332 can be removed from the leg body 31 to expose the power supply holder 34 inside the power supply case 33. In this exposed state, the power supply (dry cell battery) held in the power supply holder 34 can be replaced. After the battery replacement, the removable cover 332 is removably attached to the inner main surface of the leg body 31.

Furthermore, in the laser marker 1, when the multiple legs 3 are closed, the power supply case 33 of the powered leg 300 is housed inside the cylindrical body formed by the multiple legs 3 (see Figure 2).

In this embodiment, the leg body 31 and power supply case 33 of the powered leg 300 form a housing (second housing) 36 that houses the transistor 951.

(2.2) Laser Driving Device The laser driving device 9 provided in the laser marking device 1 will be described with reference to FIG.

As shown in FIG. 8, the laser driving device 9 includes a pair of input terminals 911, 912, a voltage conversion unit 92, a reference value generation unit 93, a processing unit 94, a light emission circuit 95, a detection unit 96, and a pair of output terminals 971, 972. Hereinafter, where necessary, the input terminal 911 may be referred to as the "high-potential side input terminal 911," the input terminal 912 as the "low-potential side input terminal 912," the output terminal 971 as the "high-potential side output terminal 971," and the output terminal 972 as the "low-potential side output terminal 972."

A power supply 90 is connected between the pair of input terminals 911, 912. For example, three dry batteries connected in series are connected between the pair of input terminals 911, 912 as the power supply 90. An input voltage Vin is applied from the power supply 90 between the pair of input terminals 911, 912.

The voltage conversion unit 92 is connected to a pair of input terminals 911, 912. The voltage conversion unit 92 receives the input voltage Vin via the pair of input terminals 911, 912 and boosts the received input voltage Vin to a DC voltage Vdc that is higher than the input voltage Vin. The voltage conversion unit 92 outputs the DC voltage Vdc from a pair of output terminals.

The voltage conversion unit 92 includes a choke coil 921, a diode 922, a switching element 923 (transistor), a smoothing capacitor 924, a switching control unit 925, and a signal input terminal 926. The choke coil 921, the diode 922, the switching element 923, and the smoothing capacitor 924 constitute the voltage conversion circuit 920.

The first end of the choke coil 921 is connected to the high-potential side input terminal 911. The second end of the choke coil 921 is connected to the anode of the diode 922. The cathode of the diode 922 is connected to the low-potential side input terminal 912 via the smoothing capacitor 924. The first main electrode (e.g., collector) of the switching element 923 is connected to the second end of the choke coil 921. The second main electrode (e.g., emitter) of the switching element 923 is connected to the low-potential side input terminal 912.

The voltage conversion circuit 920 is a boost chopper. The voltage conversion circuit 920 converts the input voltage Vin applied across a pair of input terminals 911 and 912 into a DC voltage Vdc.

A reference signal Sin indicating a reference value is input to the signal input terminal 926.

The switching control unit 925 controls the switching of the switching element 923. The switching control unit 925 is realized, for example, by an IC (Integrated Circuit) or the like.

The switching control unit 925 receives a reference signal Sin via a signal input terminal 926. The switching control unit 925 controls the duty of the switching element 923 (transistor) so that the reference value indicated by the reference signal Sin matches a predetermined specified value. As described below, the reference value is a value proportional to the magnitude of the DC voltage Vdc. Therefore, by the switching control unit 925 controlling the duty of the switching element 923 so that the reference value matches the specified value, the magnitude of the DC voltage Vdc can be controlled to a constant value proportional to the specified value. If the reference value is smaller than the specified value, the switching control unit 925 increases the duty of the switching element 923 to increase the magnitude of the DC voltage Vdc, and if the reference value is greater than the specified value, the switching control unit 925 decreases the duty of the switching element 923 to decrease the magnitude of the DC voltage Vdc.

The reference value generation unit 93 generates a reference value proportional to the magnitude of the DC voltage Vdc.

As shown in FIG. 8, the reference value generation unit 93 includes a first resistor 931, a second resistor 932, a third resistor 933, a fourth resistor 934, a first switch 935, and a second switch 936.

The first terminal of the first resistor 931 is connected to the high-potential output terminal of the voltage conversion unit 92. The second resistor 932, the series circuit of the third resistor 933 and the first switch 935, and the series circuit of the fourth resistor 934 and the second switch 936 are connected in parallel to each other to form a parallel circuit 930. The second terminal of the first resistor 931 is connected to the first terminal of the parallel circuit 930. The second terminal of the parallel circuit 930 is connected to the low-potential output terminal of the voltage conversion unit 92. In other words, the reference value generation unit 93 includes a series circuit (hereinafter also referred to as a "voltage divider circuit") of the first resistor 931 and the parallel circuit 930. This voltage divider circuit is connected between a pair of output terminals of the voltage conversion unit 92.

In the reference value generation unit 93, the connection point NO between the first resistor 931 and the parallel circuit 930 in the voltage divider circuit is connected to the signal input terminal 926 of the voltage conversion unit 92. The reference value generation unit 93 outputs the potential of the connection point NO (the voltage between the connection point NO and ground) as a reference signal Sin to the signal input terminal 926. The magnitude of the potential of the connection point NO is the reference value. In the reference value generation unit 93, the resistance value RO of the parallel circuit 930 changes as the first switch 935 and the second switch 936 are turned on and off, thereby changing the reference value. For convenience, the following description will be given assuming that the resistance value of the parallel circuit 930 is RO, the resistance value of the first resistor 931 is RO, the resistance value of the second resistor 932 is RO, the resistance value of the third resistor 933 is RO, the resistance value of the fourth resistor 934 is RO, and the magnitude of the DC voltage Vdc is RO.

When the first switch 935 and the second switch 936 are both off, the resistance value R0 of the parallel circuit 930 is R2. On the other hand, when the first switch 935 is on and the second switch 936 is off, the resistance value R0 of the parallel circuit 930 is R2·R3/(R2+R3). For convenience, if R2·R3/(R2+R3) is defined as "R5," R5 is smaller than R2. Furthermore, when the first switch 935 and the second switch 936 are both on, the resistance value R0 of the parallel circuit 930 is R2·R3·R4/(R2·R3+R2·R4+R3·R4). For convenience, if R2·R3·R4/(R2·R3+R2·R4+R3·R4) is defined as "R6," R6 is smaller than R5.

The reference value is expressed as R0 · |Vdc| / (R1 + R0), so if the magnitude of Vdc, |Vdc|, is constant, the reference value will change according to changes in the resistance value R0 of the parallel circuit 930 (the smaller the resistance value R0, the smaller the reference value).

As described above, the switching control unit 925 of the voltage conversion unit 92 controls the duty of the switching element 923 (transistor) so that the reference value indicated by the reference signal Sin matches a predetermined specified value. That is, when the resistance value R0 of the parallel circuit 930 changes as a result of the first switch 935 or the second switch 936 of the parallel circuit 930 being switched on or off, the switching control unit 925 changes the duty of the switching element 923 to change the magnitude of the DC voltage Vdc so that the reference value remains at a predetermined value. Specifically, when the first switch 935 or the second switch 936 is switched from off to on and the resistance value R0 of the parallel circuit 930 decreases, the switching control unit 925 increases the duty of the switching element 923 to increase the magnitude of the DC voltage Vdc. Furthermore, when the first switch 935 or the second switch 936 switches from on to off and the resistance value R0 of the parallel circuit 930 increases, the switching control unit 925 reduces the duty of the switching element 923 to reduce the magnitude of the DC voltage Vdc.

As a result, even if the resistance value R0 of the parallel circuit 930 changes, the reference value is maintained at a default value. Meanwhile, the magnitude of the DC voltage Vdc generated by the voltage conversion unit 92 changes in accordance with changes in the resistance value R0 of the parallel circuit 930 (specifically, it decreases when the resistance value R0 increases, and increases when the resistance value R0 decreases). In other words, in the laser driving device 9 of this embodiment, the magnitude of the DC voltage Vdc generated by the voltage conversion unit 92 can be changed by changing the reference value input to the switching control unit 925 without changing the processing operation of the switching control unit 925.

For convenience, below, the magnitude of the DC voltage Vdc when the first switch 935 and the second switch 936 are both on will be referred to as the "first voltage value," the magnitude of the DC voltage Vdc when the first switch 935 is on and the second switch 936 is off will be referred to as the "second voltage value," and the magnitude of the DC voltage Vdc when the first switch 935 and the second switch 936 are both off will be referred to as the "third voltage value." The first voltage value is greater than the second voltage value, which in turn is greater than the third voltage value. While not particularly limited, for example, the first voltage value is 8V, the second voltage value is 7V, and the third voltage value is 6V (the first resistance value R1 to the fourth resistance value R4 and the above-mentioned default values are set so that this is the case).

The processing unit 94 is realized, for example, by an IC (Integrated Circuit), FPGA (Field Programmable Gate Array), etc.

The processing unit 94 controls the magnitude of the DC voltage Vdc generated by the voltage conversion unit 92. The processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96.

The processing unit 94 changes the magnitude of the DC voltage Vdc by changing the reference value. Here, the processing unit 94 controls the on/off of the first switch 935 and the second switch 936 of the reference value generation unit 93. The processing unit 94 changes the reference value by switching the first switch 935 and the second switch 936 of the reference value generation unit 93 on and off, thereby changing the magnitude of the DC voltage Vdc. When it is desired to increase the magnitude of the DC voltage Vdc, the processing unit 94 switches either the first switch 935 or the second switch 936 from off to on. When it is desired to decrease the magnitude of the DC voltage Vdc, the processing unit 94 switches either the first switch 935 or the second switch 936 from on to off.

As shown in FIG. 8, a pair of input terminals of the light-emitting circuit 95 are connected to a pair of output terminals of the voltage conversion unit 92 via the reference value generation unit 93. The pair of output terminals of the light-emitting circuit 95 are connected to a pair of output terminals 971, 972. The high-potential side output terminal of the light-emitting circuit 95 is at the same potential as the high-potential side input terminal of the light-emitting circuit 95. Therefore, the high-potential side output terminal 971 is at the same potential as the high-potential side output terminal of the voltage conversion unit 92.

As shown in Figure 8, the semiconductor laser 52 is connected between a pair of output terminals 971 and 972. The anode of the semiconductor laser 52 (laser diode) is connected to the output terminal 971, and the cathode is connected to the output terminal 972.

As shown in FIG. 8, the light-emitting circuit 95 includes a voltage source 950, a transistor (hereinafter also referred to as the "first transistor") 951, a second transistor 952, a light-receiving element 953, and resistors 954, 955, 956, and 957.

The first transistor 951 is a semiconductor element that controls the amount of light emitted by the semiconductor laser 52 by adjusting the amount of current flowing through the semiconductor laser 52. The first transistor 951 is, for example, an NPN bipolar transistor.

The first transistor 951 has a first main electrode (e.g., a collector), a second main electrode (e.g., an emitter), and a control electrode (e.g., a base). The first main electrode of the first transistor 951 is connected to the output terminal 972 (the cathode of the semiconductor laser 52) via a detection resistor 963 (shunt resistor) for current detection. The second main electrode of the first transistor 951 is connected to the low-potential output terminal of the voltage conversion unit 92. In the laser driving device 9 of this embodiment, the detection resistor 963 may be omitted.

The first transistor 951 operates in the active region. The first transistor 951 controls the current flowing through it (collector current), i.e., the current flowing through the semiconductor laser 52, in accordance with the current flowing through its control electrode (base current).

The second transistor 952 controls the current flowing through the control electrode of the first transistor 951 depending on the amount of light received by the light-receiving element 953. The second transistor 952 is, for example, a PNP bipolar transistor.

The second transistor 952 has a first main electrode (e.g., a collector), a second main electrode (e.g., an emitter), and a control electrode (e.g., a base). The second main electrode of the second transistor 952 is connected to a voltage source 950. The voltage source 950 outputs a DC voltage Vc having a fixed (constant) voltage value. The DC voltage Vc is generated, for example, from the output voltage of the power source 90. The first main electrode of the second transistor 952 is connected to the low-potential output terminal of the voltage conversion unit 92 via a first voltage divider circuit including resistors 954 and 955 connected in series. The output terminal of the first voltage divider circuit (connection point N1 between resistors 954 and 955) is connected to the control electrode of the first transistor 951.

The second transistor 952 operates in the active region. The second transistor 952 controls the current flowing through it (collector current), i.e., the current flowing through the first voltage divider circuit (resistors 954 and 955), depending on the current flowing through its control electrode (base current).

The light receiving element 953 is, for example, a photodiode. The light receiving element 953 receives light that leaks from the laser light L0 emitted by the semiconductor laser 52. In this way, the light receiving element 953 detects the amount of light emitted by the laser light L0 from the semiconductor laser 52.

The cathode of the light receiving element 953 is connected to the high-potential output terminal of the voltage conversion unit 92. The anode of the light receiving element 953 is connected to the low-potential output terminal of the voltage conversion unit 92 via a second voltage divider circuit including resistors 956 and 957 connected in series. The output terminal of the second voltage divider circuit (connection point N2 between resistors 956 and 957) is connected to the control electrode of the second transistor 952.

When the power supply to this light-emitting circuit 95 is turned on, the voltage source 950 applies a DC voltage Vc, causing the second transistor 952 to conduct, and a base current is supplied to the first transistor 951, causing the first transistor 951 to initially conduct. This causes a current due to the DC voltage Vdc to flow through the semiconductor laser 52 and the first transistor 951. This causes the semiconductor laser 52 to emit light, emitting laser light L0.

When the semiconductor laser 52 is emitting laser light L0 and the amount of light emitted by the semiconductor laser 52 increases, the amount of light received by the light-receiving element 953 increases, the current flowing through the light-receiving element 953 increases, the voltage across resistor 957 increases, and the potential at node N2 increases. As the potential at node N2 increases, the base current of the second transistor 952 decreases, the collector current of the second transistor 952 decreases, the voltage across resistor 955 decreases, and the potential at node N1 decreases. As the potential at node N1 decreases, the base current of the first transistor 951 decreases, and the collector current of the first transistor 951, i.e., the current flowing through the semiconductor laser 52, decreases. This reduces the amount of light emitted by the semiconductor laser 52.

Furthermore, when the semiconductor laser 52 is emitting laser light L0 and the light emission amount of the semiconductor laser 52 decreases, the amount of light received by the light receiving element 953 decreases, the current flowing through the light receiving element 953 decreases, the voltage across resistor 957 decreases, and the potential at node N2 decreases. When the potential at node N2 decreases, the base current of the second transistor 952 increases, the collector current of the second transistor 952 increases, the voltage across resistor 955 increases, and the potential at node N1 increases. When the potential at node N1 increases, the base current of the first transistor 951 increases, and the collector current of the first transistor 951, i.e., the current flowing through the semiconductor laser 52, increases. This increases the light emission amount of the semiconductor laser 52.

As such, the light-emitting circuit 95 comprises a light-receiving element 953 that receives light from the semiconductor laser 52, and a current control circuit 959 that is connected to the control electrode of the transistor 951 and controls the current flowing to the control electrode in accordance with the amount of light received by the light-receiving element 953 so that the amount of light received by the light-receiving element 953 converges to a predetermined value. The current control circuit 959 comprises a voltage source 950, a second transistor 952, and resistors 954, 955, 956, and 957. Such a light-emitting circuit 95 (current control circuit 959) performs feedback control to maintain a constant light emission amount of the semiconductor laser 52. As a result, the light emission amount of the semiconductor laser 52 is maintained at a constant value that corresponds to the magnitude of the DC voltage Vdc.

The detection unit 96 detects a physical quantity that indicates the operating state of the semiconductor laser 52 or the transistor 951. In this case, the detection unit 96 detects the voltage between the terminals of the transistor 951 as the physical quantity.

As shown in FIG. 8, the detection unit 96 includes a voltage divider circuit 960. The voltage divider circuit 960 is connected in parallel with the transistor 951. The voltage divider circuit 960 is connected across the first and second main electrodes of the transistor 951.

The voltage divider circuit 960 includes a first voltage divider resistor 961 and a second voltage divider resistor 962. The first terminal of the first voltage divider resistor 961 is connected to the first main electrode of the transistor 951, the second terminal of the first voltage divider resistor 961 is connected to the first terminal of the second voltage divider resistor 962, and the second terminal of the second voltage divider resistor 962 is connected to the second main electrode of the transistor 951. The connection point between the first voltage divider resistor 961 and the second voltage divider resistor 962 is connected to the processing unit 94. The detection unit 96 outputs the voltage across the second voltage divider resistor 962 to the processing unit 94 as the detection result. Note that the voltage across the second voltage divider resistor 962 is proportional to the voltage across the transistor 951, and therefore in this disclosure, the voltage across the second voltage divider resistor 962 detected by the detection unit 96 is also simply referred to as the "voltage across the transistor 951."

The processing unit 94 controls the magnitude of the DC voltage Vdc generated by the voltage conversion unit 92 based on the detection result of the detection unit 96. The processing unit 94 controls the magnitude of the DC voltage Vdc by controlling the reference value generation unit 93 (first switch 935 and second switch 936).

The processing unit 94 controls the magnitude of the DC voltage Vdc so that it matches one of multiple preset target voltage values. The multiple target voltage values include a first voltage value (8 V), a second voltage value (7 V), and a third voltage value (6 V). When the processing unit 94 controls the DC voltage Vdc to match the first voltage value, it turns on both the first switch 935 and the second switch 936. When the processing unit 94 controls the DC voltage Vdc to match the second voltage value, it turns on the first switch 935 and the second switch 936 and turns off the second switch 936. When the processing unit 94 controls the DC voltage Vdc to match the third voltage value, it turns off both the first switch 935 and the second switch 936. Using multiple target voltage values enables a simpler circuit configuration than a configuration in which the target voltage value changes continuously.

Below, an example of how the processing unit 94 controls the reference value generation unit 93 (first switch 935 and second switch 936) is described.

When the power is turned on, the processing unit 94 turns on the first switch 935 and the second switch 936 so that the DC voltage Vdc generated by the voltage conversion unit 92 becomes the first voltage value (8 V), which is the maximum voltage that can be output.

Immediately after power-on, the processing unit 94 compares the physical quantity detected by the detection unit 96 (the magnitude of the voltage between the terminals of the transistor 951) with a first reference value and a second reference value (second reference value > first reference value).

If the magnitude of the voltage across the terminals of transistor 951 exceeds the second reference value, this means that the voltage drop between the collector and emitter of transistor 951 is large, i.e., the magnitude of DC voltage Vdc is excessive (the second reference value is set accordingly). In this case, the processing unit 94 turns off the second switch 936 and reduces the magnitude of DC voltage Vdc from the first voltage value (8 V) to the second voltage value (7 V).

On the other hand, if the magnitude of the voltage between the terminals of the transistor 951 is equal to or less than the first reference value, the processing unit 94 determines that the semiconductor laser 52 is not emitting light normally. The processing unit 94 may warn the user, for example, by turning on a warning light provided on the first housing 4.

Note that when the magnitude of the voltage between the terminals of the transistor 951 exceeds the first reference value and is equal to or less than the second reference value, the processing unit 94 keeps the first switch 935 and the second switch 936 on. Hereinafter, the state in which the first switch 935 and the second switch 936 are both on will also be referred to as the "both on state."

After turning off the second switch 936, the processing unit 94 compares the physical quantity detected by the detection unit 96 (the magnitude of the voltage between the terminals of the transistor 951) with the third reference value and the fourth reference value (fourth reference value > third reference value).

If the magnitude of the voltage between the terminals of transistor 951 exceeds the fourth reference value, the processing unit 94 further turns off the first switch 935 and reduces the magnitude of the DC voltage Vdc from the second voltage value (7 V) to the third voltage value (6 V).

On the other hand, when the magnitude of the voltage between the terminals of the transistor 951 exceeds the third reference value and is equal to or less than the fourth reference value, the processing unit 94 keeps the first switch 935 on and the second switch 936 off. Hereinafter, the state in which the first switch 935 is on and the second switch 936 is off is also referred to as the "one-off state."

Note that if the voltage between the terminals of the transistor 951 is equal to or lower than the third reference value, the processing unit 94 may turn on the second switch 936 again. When turning on the second switch 936 again, the processing unit 94 may set a predetermined delay time.

After turning off the first switch 935, the processing unit 94 compares the physical quantity detected by the detection unit 96 (the voltage between the terminals of the transistor 951) with a fifth reference value.

If the voltage between the terminals of the transistor 951 exceeds the fifth reference value, the processing unit 94 keeps the first switch 935 and the second switch 936 off. Hereinafter, the state in which the first switch 935 and the second switch 936 are both off will also be referred to as the "both off state."

If the voltage between the terminals of the transistor 951 is equal to or lower than the fifth reference value, the processing unit 94 may turn on the first switch 935 again. When turning on the first switch 935 again, the processing unit 94 may set a predetermined delay time.

In this way, the processing unit 94 sets the magnitude of the DC voltage Vdc at power-on to the maximum value (8V) within the selectable voltage range (here, 6V, 7V, 8V). This increases the likelihood that the semiconductor laser 52 will be able to emit laser light L0 immediately after power-on. However, this is not a limitation, and the processing unit 94 may also set the magnitude of the DC voltage Vdc at power-on to the minimum value (6V) within the selectable voltage range (here, 6V, 7V, 8V).

After the above initial operation is completed, the processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96.

Here, the processing unit 94 reduces the magnitude of the DC voltage Vdc when the physical quantity (the voltage between the terminals of the transistor 951) detected by the detection unit 96 increases and exceeds a predetermined threshold. For example, in the double-on state (when the magnitude of the DC voltage Vdc is 8 V), if the processing unit 94 detects that the voltage between the terminals of the transistor 951 has increased and exceeded a predetermined threshold (e.g., the second reference value described above), it turns off the second switch 936 and reduces the magnitude of the DC voltage Vdc to 7 V. Also, in the single-off state (when the magnitude of the DC voltage Vdc is 7 V), if the processing unit 94 detects that the voltage between the terminals of the transistor 951 has increased and exceeded a predetermined threshold (e.g., the fourth reference value described above), it turns off the first switch 935 and reduces the magnitude of the DC voltage Vdc to 6 V.

Furthermore, when the physical quantity (terminal voltage of transistor 951) detected by the detection unit 96 decreases and falls below a predetermined threshold, the processing unit 94 increases the magnitude of the DC voltage Vdc. For example, in the double-off state (when the magnitude of DC voltage Vdc is 6 V), if the processing unit 94 detects that the terminal voltage of transistor 951 has decreased and fallen below a predetermined threshold (e.g., the fifth reference value described above), the processing unit 94 turns on the first switch 935 and increases the magnitude of the DC voltage Vdc to 7 V. Furthermore, in the single-off state (when the magnitude of DC voltage Vdc is 7 V), if the processing unit 94 detects that the terminal voltage of transistor 951 has decreased and fallen below a predetermined threshold (e.g., the third reference value described above), the processing unit 94 turns on the second switch 936 and increases the magnitude of the DC voltage Vdc to 8 V.

In this way, the processing unit 94 of the laser driving device 9 reduces the magnitude of the DC voltage Vdc when the physical quantity (voltage across the transistor 951) detected by the detection unit 96 increases and exceeds the first threshold (second reference value, fourth reference value). Furthermore, the processing unit 94 increases the magnitude of the DC voltage Vdc when the physical quantity (voltage across the transistor 951) detected by the detection unit 96 decreases and becomes equal to or less than the second threshold (third reference value, fifth reference value). By controlling the magnitude of the DC voltage Vdc based on the voltage across the transistor 951, the processing unit 94 can adjust the magnitude of the DC voltage Vdc to the minimum level required for the semiconductor laser 52 to emit laser light L0. This makes it possible for the laser driving device 9 of this embodiment to suppress excess power consumption and reduce power consumption.

In the laser driving device 9 of this embodiment, the second reference value is greater than the third reference value, and the fourth reference value is greater than the fifth reference value. In other words, when the physical quantity (voltage across the transistor 951) detected by the detection unit 96 increases and exceeds the first threshold (second reference value, fourth reference value), the processing unit 94 reduces the magnitude of the DC voltage Vdc. When the physical quantity decreases and becomes equal to or less than the second threshold (third reference value, fifth reference value), the processing unit 94 increases the magnitude of the DC voltage Vdc. The first threshold is greater than the second threshold. In other words, the processing unit 94 applies hysteresis when changing the magnitude of the DC voltage Vdc. This reduces the likelihood of oscillation, in which the magnitude of the DC voltage Vdc switches between 8V and 7V or between 7V and 6V multiple times in a short period of time.

Note that one example of a cause of a change in the detection result of the detection unit 96 (the physical quantity detected by the detection unit 96) after the semiconductor laser 52 starts emitting light is a change in the temperature of the semiconductor laser 52. Examples of causes of a change in the temperature of the semiconductor laser 52 include heat generation from the semiconductor laser 52 or surrounding circuit components, or a change in the outside air temperature.

The semiconductor laser 52 has a characteristic that, under conditions where the current flowing through the semiconductor laser 52 is constant, the forward voltage of the semiconductor laser 52 decreases as the temperature of the semiconductor laser 52 increases. Therefore, when the temperature of the semiconductor laser 52 increases, the forward voltage of the semiconductor laser 52 decreases, the voltage across the transistor 951 increases, and the physical quantity detected by the detection unit 96 increases. In this case, the processing unit 94 decreases the magnitude of the DC voltage Vdc. On the other hand, when the temperature of the semiconductor laser 52 decreases, the forward voltage of the semiconductor laser 52 increases, the voltage across the transistor 951 decreases, and the physical quantity detected by the detection unit 96 decreases. In this case, the processing unit 94 increases the magnitude of the DC voltage Vdc.

In short, when the temperature of the semiconductor laser 52 increases and the voltage across the transistor 951 exceeds a predetermined threshold, the processing unit 94 reduces the magnitude of the DC voltage Vdc. As a result, for example, when the laser marking device 1 is used in a cold climate, if the forward voltage required for the semiconductor laser 52 to emit laser light L0 decreases from the initial state of light emission due to heat generation by the semiconductor laser 52, etc., the processing unit 94 changes the magnitude of the DC voltage Vdc to a relatively small value. This makes it possible to reduce power consumption.

In addition, even if there are manufacturing errors or deterioration over time in the circuit components of the laser marking device 1, the processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection results of the detection unit 96, making it possible to operate the laser driving device 9 in accordance with the actual state of the circuit components. This makes it possible to reduce power consumption.

As shown in Figures 3 to 6, in the laser marking device 1 of this embodiment, the semiconductor laser 52 and the transistor 951 are housed in different housings. Specifically, the semiconductor laser 52 is mounted on the first board 56 and housed in the first housing 4. Meanwhile, the transistor 951 is mounted on the second board 35 and housed in the second housing 36. The second housing 36 is a separate housing from the first housing 4. This removes the transistor 951, which is a heat source that thermally affects the semiconductor laser 52, from the first housing 4 housing the semiconductor laser 52. This prevents the transistor 951 from causing a temperature rise inside the first housing 4, which in turn prevents a temperature rise in the semiconductor laser 52 due to heat generated by the transistor 951. By suppressing the temperature rise in the semiconductor laser 52, it is possible to prevent a decrease in the light-emitting efficiency and a shortened lifespan of the semiconductor laser 52.

In the laser marking device 1 of this embodiment, the light receiving element 953 is also mounted on the first board 56 and housed in the first housing 4. On the other hand, other components in the laser driving device 9 that may become heat sources (such as the switching element 923, smoothing capacitor 924, first switch 935, second switch 936, second transistor 952, switching control unit 925, and processing unit 94) may be housed in the first housing 4, but are preferably housed in the second housing 36. If the components that become heat sources are housed in the second housing 36, the temperature rise of the semiconductor laser 52 can be suppressed, and a decrease in the light emission efficiency and shortened lifespan of the semiconductor laser 52 can be suppressed.

(3) Modifications The above embodiment is merely one of various embodiments of the present disclosure. The above embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the embodiment are listed below. The above embodiment and the modifications described below can be applied in appropriate combinations.

(3.1) Modification 1
The laser driving device 9 of this modified example will be described with reference to Fig. 9. The laser driving device 9 of this modified example differs from the laser driving device 9 of the above embodiment in the configuration of the detection unit 96. In the laser driving device 9 of this modified example, the description of the same configuration as the laser driving device 9 of the above embodiment may be omitted as appropriate.

As shown in FIG. 9 , in the laser driving device 9 of this modified example, the detection unit 96 detects the terminal voltage of the semiconductor laser 52. "Terminal voltage of the semiconductor laser 52" refers to the voltage between both ends of the semiconductor laser 52 (between the anode and cathode).

As shown in FIG. 9, the detection unit 96 includes a voltage divider circuit 964. The voltage divider circuit 964 is connected in parallel with the semiconductor laser 52. The voltage divider circuit 964 is connected across the anode and cathode of the semiconductor laser 52.

The voltage-dividing circuit 964 includes a first voltage-dividing resistor 965 and a second voltage-dividing resistor 966. The first terminal of the first voltage-dividing resistor 965 is connected to a high-potential output terminal 971 (the anode of the semiconductor laser 52). The second terminal of the first voltage-dividing resistor 965 is connected to a first terminal of the second voltage-dividing resistor 966. The second terminal of the second voltage-dividing resistor 966 is connected to a low-potential output terminal 972 (the cathode of the semiconductor laser 52). The junction between the first voltage-dividing resistor 965 and the second voltage-dividing resistor 966 is connected to the non-inverting input terminal of an operational amplifier 967 that constitutes a differential amplifier circuit. The inverting input terminal of the operational amplifier 967 is connected to a voltage source 968 that outputs a constant voltage, and the output terminal of the operational amplifier 967 is connected to the processing unit 94. The detection unit 96 outputs the voltage obtained by subtracting the voltage across the second voltage-dividing resistor 966 from the constant voltage to the processing unit 94 as the detection result (physical quantity).

The processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96 (the voltage between the terminals of the semiconductor laser 52).

As described above, the semiconductor laser 52 has a characteristic in which the forward voltage decreases as the temperature of the semiconductor laser 52 increases. Therefore, when the physical quantity detected by the detection unit 96 (the voltage obtained by subtracting the voltage across the second voltage divider resistor from a constant voltage) increases due to a decrease in the temperature of the semiconductor laser 52 and exceeds a predetermined threshold, the processing unit 94 reduces the magnitude of the DC voltage Vdc. Furthermore, when the physical quantity detected by the detection unit 96 decreases due to an increase in the temperature of the semiconductor laser 52 and falls below the predetermined threshold, the processing unit 94 controls the reference value generation unit 93 to increase the magnitude of the DC voltage Vdc.

In the laser driving device 9 of this modified example, the processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96, making it possible to adjust the magnitude of the DC voltage Vdc to the minimum level necessary for the semiconductor laser 52 to emit laser light L0. This makes it possible to suppress excess power consumption and reduce power consumption.

(3.2) Modification 2
The laser driving device 9 of this modified example will be described with reference to Fig. 10. The laser driving device 9 of this modified example differs from the laser driving device 9 of the above embodiment in the configuration of the detection unit 96. In the laser driving device 9 of this modified example, the description of the same configuration as the laser driving device 9 of the above embodiment may be omitted as appropriate.

As shown in Figure 10, in this modified laser driving device 9, the detection unit 96 detects the current flowing through the semiconductor laser 52.

As shown in FIG. 10, the detection unit 96 includes a detection resistor 963. The detection resistor 963 is connected in series with the semiconductor laser 52. The detection unit 96 detects the current flowing through the detection resistor 963 as the detection result (physical quantity).

The processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96 (the current flowing through the semiconductor laser 52).

As the temperature of the semiconductor laser 52 increases, the light emission output of the semiconductor laser 52 decreases. In the laser driving device 9, the light emission circuit 95 performs feedback control to maintain the light emission output of the semiconductor laser 52, increasing the current flowing through the semiconductor laser 52. Therefore, as the temperature of the semiconductor laser 52 increases, the physical quantity detected by the detection unit 96 increases. In this case, the processing unit 94 controls the reference value generation unit 93 to reduce the magnitude of the DC voltage Vdc.

Furthermore, as the temperature of the semiconductor laser 52 decreases, the light emission output of the semiconductor laser 52 increases. In the laser driving device 9, the light emission circuit 95 performs feedback control to maintain the light emission output of the semiconductor laser 52, thereby reducing the current flowing through the semiconductor laser 52. Therefore, as the temperature of the semiconductor laser 52 increases, the physical quantity detected by the detection unit 96 decreases. In this case, the processing unit 94 controls the reference value generation unit 93 to increase the magnitude of the DC voltage Vdc.

In the laser driving device 9 of this modified example, the processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96, making it possible to adjust the magnitude of the DC voltage Vdc to the minimum level necessary for the semiconductor laser 52 to emit laser light L0. This makes it possible to suppress excess power consumption and reduce power consumption.

(3.3) Modification 3
The laser driving device 9 of this modified example will be described with reference to Fig. 11. The laser driving device 9 of this modified example differs from the laser driving device 9 of the above embodiment in the configuration of the detection unit 96. In the laser driving device 9 of this modified example, the description of the same configuration as the laser driving device 9 of the above embodiment may be omitted as appropriate.

As shown in FIG. 11, in this modified laser driving device 9, the detection unit 96 detects the temperature of the semiconductor laser 52.

As shown in FIG. 11, the detection unit 96 is equipped with a temperature sensor 969. The temperature sensor 969 is disposed near the semiconductor laser 52 and detects the temperature of the semiconductor laser 52 as the detection result (physical quantity).

The processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result (temperature of the semiconductor laser 52) of the detection unit 96.

When the temperature of the semiconductor laser 52, i.e., the physical quantity detected by the detection unit 96, increases, the processing unit 94 controls the reference value generation unit 93 to decrease the magnitude of the DC voltage Vdc. Furthermore, when the temperature of the semiconductor laser 52, i.e., the physical quantity detected by the detection unit 96, decreases, the processing unit 94 controls the reference value generation unit 93 to increase the magnitude of the DC voltage Vdc.

In the laser driving device 9 of this modified example, the processing unit 94 controls the magnitude of the DC voltage Vdc based on the detection result of the detection unit 96, making it possible to adjust the magnitude of the DC voltage Vdc to the minimum level necessary for the semiconductor laser 52 to emit laser light L0. This makes it possible to suppress excess power consumption and reduce power consumption.

The detection unit 96 may detect the temperature of the transistor 951 instead of or in addition to the temperature of the semiconductor laser 52. Because a common current flows through the semiconductor laser 52 and the transistor 951, the heat generation status of the transistor 951 can be said to indicate the heat generation status of the semiconductor laser 52. Therefore, by detecting the temperature of the transistor 951, the temperature status of the semiconductor laser 52 can be indirectly determined. The processing unit 94 may control the magnitude of the DC voltage Vdc based on the detected temperature of the transistor 951.

(4) Aspects As is clear from the above-described embodiments and modifications, the present specification discloses the following aspects.

The laser driving device (9) of the first aspect includes a voltage conversion unit (92), a transistor (951), a detection unit (96), and a processing unit (94). The voltage conversion unit (92) boosts the input voltage (Vin) to a DC voltage (Vdc) higher than the input voltage (Vin) and outputs the DC voltage (Vdc) to the semiconductor laser (52). The transistor (951) is connected to the semiconductor laser (52) and adjusts the magnitude of the current flowing through the semiconductor laser (52). The detection unit (96) detects the voltage between the terminals of the transistor (951). The processing unit (94) controls the magnitude of the DC voltage (Vdc) based on the detection result of the detection unit (96).

This aspect makes it possible to reduce power consumption.

The laser driving device (9) of the second aspect includes a voltage conversion unit (92), a detection unit (96), and a processing unit (94). The voltage conversion unit (92) boosts the input voltage (Vin) to a DC voltage (Vdc) higher than the input voltage (Vin) and outputs the DC voltage (Vdc) to the semiconductor laser (52). The detection unit (96) detects the voltage between the terminals of the semiconductor laser (52). The processing unit (94) controls the magnitude of the DC voltage (Vdc) based on the detection result of the detection unit (96).

This aspect makes it possible to reduce power consumption.

The laser driving device (9) of the third aspect includes a voltage conversion unit (92), a detection unit (96), and a processing unit (94). The voltage conversion unit (92) boosts the input voltage (Vin) to a DC voltage (Vdc) higher than the input voltage (Vin) and outputs the DC voltage (Vdc) to the semiconductor laser (52). The detection unit (96) detects the current flowing through the semiconductor laser (52). The processing unit (94) controls the magnitude of the DC voltage (Vdc) based on the detection result of the detection unit (96).

This aspect makes it possible to reduce power consumption.

The laser driving device (9) of the fourth aspect includes a voltage conversion unit (92), a transistor (951), a detection unit (96), and a processing unit (94). The voltage conversion unit (92) boosts the input voltage (Vin) to a DC voltage (Vdc) higher than the input voltage (Vin) and outputs the DC voltage (Vdc) to the semiconductor laser (52). The transistor (951) is connected to the semiconductor laser (52) and adjusts the magnitude of the current flowing through the semiconductor laser (52). The detection unit (96) detects the temperature of the semiconductor laser (52) or the transistor (951). The processing unit (94) controls the magnitude of the DC voltage (Vdc) based on the detection result of the detection unit (96).

This aspect makes it possible to reduce power consumption.

In the laser driving device (9) of the fifth aspect, in the first or fourth aspect, the semiconductor laser (52) is housed in a first housing (4). The transistor (951) is housed in a second housing (36) separate from the first housing (4).

This embodiment can suppress the temperature rise of the semiconductor laser (52) due to heat generation by the transistor (951), thereby suppressing the decrease in the light-emitting efficiency and shortening of the lifespan of the semiconductor laser (52).

The laser driving device (9) of the sixth aspect is any one of the first, fourth, and fifth aspects and includes a light-emitting circuit (95) including a transistor (951). The light-emitting circuit (95) further includes a light-receiving element (953) and a current control circuit (959). The light-receiving element (953) receives light from the semiconductor laser (52). The current control circuit (959) is connected to the control electrode of the transistor (951). The current control circuit (959) controls the current flowing through the control electrode in accordance with the amount of light received by the light-receiving element (953) so that the amount of light received by the light-receiving element (953) converges to a predetermined value.

This aspect makes it possible to perform feedback control so that the light emission intensity of the semiconductor laser (52) remains constant.

In the seventh aspect of the laser driving device (9), in any one of the first to sixth aspects, the processing unit (94) controls the magnitude of the DC voltage (Vdc) so that the magnitude of the DC voltage (Vdc) matches one of multiple preset target voltage values.

This aspect makes it possible to simplify the circuit configuration.

In the eighth aspect of the laser driving device (9), in any one of the first to seventh aspects, the detection result of the detection unit (96) includes a physical quantity detected by the detection unit (96). The processing unit (94) reduces the magnitude of the DC voltage (Vdc) when the physical quantity increases and exceeds a first threshold, and increases the magnitude of the DC voltage (Vdc) when the physical quantity decreases and becomes equal to or less than a second threshold. The first threshold is greater than the second threshold.

This aspect makes it possible to suppress the occurrence of so-called vibrations.

In a ninth aspect of the laser driving device (9), in any one of the first to eighth aspects, the voltage conversion unit (92) includes a signal input terminal (926), a voltage conversion circuit (920), and a switching control unit (925). A reference signal (Sin) indicating a reference value proportional to the magnitude of the DC voltage (Vdc) is input to the signal input terminal (926). The voltage conversion circuit (920) includes a switching element (923) and converts the input voltage (Vin) into a DC voltage (Vdc). The switching control unit (925) controls the duty of the switching element (923) so that the reference value matches a predetermined specified value. The processing unit (94) changes the magnitude of the DC voltage (Vdc) by changing the reference value.

According to this aspect, it is possible to change the magnitude of the DC voltage (Vdc) generated by the voltage conversion unit (92) by changing the reference value input to the switching control unit (925) without changing the processing of the switching control unit (925).

The laser marking device (1) of the tenth aspect comprises a laser driving device (9) of any one of the first to ninth aspects and an optical system (53) that converts light emitted from the semiconductor laser (52) into linear light.

This aspect makes it possible to reduce power consumption.

REFERENCE SIGNS LIST 1 Laser marking device 36 Second housing 4 First housing 52 Semiconductor laser 53 Optical system 9 Laser driving device 92 Voltage conversion unit 920 Voltage conversion circuit 923 Switching element 925 Switching control unit 926 Signal input terminal 94 Processing unit 95 Light emitting circuit 951 Transistor (first transistor)
953 Light receiving element 959 Current control circuit 96 Detector Sin Reference signal Vin Input voltage Vdc DC voltage

Claims (13)

a voltage conversion unit that boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser;
a transistor connected to the semiconductor laser and adjusting the magnitude of a current flowing through the semiconductor laser;
a detection unit that detects a voltage between the terminals of the transistor;
a processing unit that controls the magnitude of the DC voltage based on the detection result of the detection unit;
Equipped with
the processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of a plurality of preset target voltage values;
The processing unit
When the voltage between the terminals increases and exceeds a first threshold, the magnitude of the DC voltage is reduced;
increasing the magnitude of the DC voltage when the inter-terminal voltage decreases to a second threshold value or less;
The first threshold is greater than the second threshold.
Laser driver. a voltage conversion unit that boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser;
a detection unit for detecting a voltage between terminals of the semiconductor laser;
a processing unit that controls the magnitude of the DC voltage based on the detection result of the detection unit;
Equipped with
the processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of a plurality of preset target voltage values;
The processing unit
When the voltage between the terminals increases and exceeds a first threshold, the magnitude of the DC voltage is reduced;
increasing the magnitude of the DC voltage when the inter-terminal voltage decreases to a second threshold value or less;
The first threshold is greater than the second threshold.
Laser driver. a voltage conversion unit that boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser;
a detection unit that detects a current flowing through the semiconductor laser;
a processing unit that controls the magnitude of the DC voltage based on the detection result of the detection unit;
Equipped with
the processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of a plurality of preset target voltage values;
The processing unit
When the current increases and exceeds a first threshold, the magnitude of the DC voltage is decreased;
increasing the magnitude of the DC voltage when the current decreases to a second threshold value or less;
The first threshold is greater than the second threshold.
Laser driver. a voltage conversion unit that boosts an input voltage to a DC voltage higher than the input voltage and outputs the DC voltage to a semiconductor laser;
a transistor connected to the semiconductor laser and adjusting the magnitude of a current flowing through the semiconductor laser;
a detection unit that detects the temperature of the semiconductor laser or the transistor;
a processing unit that controls the magnitude of the DC voltage based on the detection result of the detection unit;
Equipped with
the processing unit controls the magnitude of the DC voltage so that the magnitude of the DC voltage matches one of a plurality of preset target voltage values;
The processing unit
decreasing the magnitude of the DC voltage when the temperature increases above a first threshold;
increasing the magnitude of the DC voltage when the temperature decreases to a value equal to or less than a second threshold;
The first threshold is greater than the second threshold.
Laser driver. the semiconductor laser is housed in a first housing;
The transistor is housed in a second housing separate from the first housing.
5. The laser driving device according to claim 1. a light-emitting circuit including the transistor,
The light emitting circuit includes:
a light receiving element that receives light from the semiconductor laser;
a current control circuit connected to a control electrode of the transistor, the current control circuit controlling the current flowing through the control electrode in accordance with the amount of light received by the light receiving element so that the amount of light received by the light receiving element converges to a predetermined value;
Further comprising:
5. The laser driving device according to claim 1. a transistor connected to the semiconductor laser and configured to adjust the magnitude of a current flowing through the semiconductor laser;
the semiconductor laser is housed in a first housing;
The transistor is housed in a second housing separate from the first housing.
4. The laser driving device according to claim 2 or 3. The voltage conversion unit
a signal input terminal to which a reference signal indicating a reference value proportional to the magnitude of the DC voltage is input;
a voltage conversion circuit including a switching element for converting the input voltage into the DC voltage;
a switching control unit that controls a duty of the switching element so that the reference value coincides with a predetermined specified value;
Equipped with
The processing unit changes the reference value to change the magnitude of the DC voltage.
The laser driving device according to any one of claims 1 to 4. The laser driving device according to any one of claims 1 to 4,
an optical system that converts the light emitted from the semiconductor laser into linear light;
Equipped with
Laser level. The laser driving device according to claim 5 ;
an optical system that converts the light emitted from the semiconductor laser into linear light;
Equipped with
Laser level. The laser driving device according to claim 6 ;
an optical system that converts the light emitted from the semiconductor laser into linear light;
Equipped with
Laser level. The laser driving device according to claim 7,
an optical system that converts the light emitted from the semiconductor laser into linear light;
Equipped with
Laser level. The laser driving device according to claim 8 ;
an optical system that converts the light emitted from the semiconductor laser into linear light;
Equipped with
Laser level.