Current source circuit, and direct diode laser device including the same

Abstract

To provide a current source circuit capable of improving the quality of laser processing by suppressing overshoot and oscillation of the supply current flowing to the light emission circuit.SOLUTION: A current source circuit 40 includes: a current detection unit 48 that detects supply current; a drive control unit 51 that controls switching elements 42a-42d of a switching circuit 42 based on a control voltage Vc; and a control voltage generation unit 52 that controls the control voltage Vc so that the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic is reduced, and while the command current Ic is below the detection value Im of the current detection unit 48, and when the absolute value exceeds a predetermined threshold, controls the response gain of the control voltage Vc to be larger than when it is below the predetermined threshold.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a current source circuit for supplying current to a light emitting circuit for laser processing having at least one laser diode, and a direct diode laser device including the current source circuit. [Background technology]

[0002] Patent Document 1 discloses a current source circuit that supplies a current to a light-emitting circuit for laser processing having at least one laser diode. This current source circuit includes a switching circuit having at least one switching element, which generates an AC voltage using a DC voltage by the switching operation of the switching element, a DC current generation circuit that supplies a DC supply current to the light-emitting circuit using the AC voltage generated by the switching circuit, a current detection unit that detects the supply current, a drive control unit that controls the switching element of the switching circuit based on a control signal, and a control means that controls the control signal so that the difference between the detection value of the current detection unit and a predetermined command current is small. In this current source circuit, the control means adjusts the responsiveness of the supply current supplied to the light-emitting circuit by controlling the conduction rate of the switching circuit depending on whether the detection value of the DC voltage input to the switching circuit is higher or lower than a reference input voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 186082 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in a current source circuit such as that disclosed in Patent Document 1, if it takes a long time for the supply current flowing to the light-emitting circuit to rise and fall, the quality of the laser processing will deteriorate.

[0005] On the other hand, if the response gain of the control signal is increased in order to improve the responsiveness of the supply current when the command current rises and falls, there is a risk that overshoot or oscillation will occur in the supply current.

[0006] The present disclosure has been made in consideration of these points, and has as its object to improve the quality of laser processing and to suppress overshoot and oscillation of the supply current flowing to the light-emitting circuit. [Means for solving the problem]

[0007] In order to achieve the above object, a first embodiment of the present disclosure is a current source circuit that supplies current to a light-emitting circuit for laser processing having one laser diode or multiple laser diodes connected in series with each other, the current source circuit comprising: a switching circuit having at least one switching element that generates a first AC voltage or a continuous pulse voltage using a DC voltage by the switching operation of the switching element; a DC current generation circuit that supplies a DC supply current to the light-emitting circuit using the first AC voltage or the continuous pulse voltage generated by the switching circuit; a current detection unit that detects the supply current; a drive control unit that controls the switching element of the switching circuit based on a control voltage; and a control voltage generation unit that controls the control voltage so that the absolute value of the difference between the detection value of the current detection unit and a predetermined command current is small, and that, while the command current is below the detection value of the current detection unit, increases the response gain of the control of the control voltage when the absolute value exceeds a predetermined threshold value compared to when the command current is below the predetermined threshold value.

[0008] As a result, while the command current is below the detection value of the current detection unit, when the absolute value of the difference between the detection value of the current detection unit and the command current exceeds a predetermined threshold, the response gain of the control voltage is made larger than when the absolute value is below the predetermined threshold, thereby shortening the time it takes for the supply current flowing through the light emission circuit to fall, thereby improving the quality of laser processing.

[0009] On the other hand, when the absolute value of the difference is below a predetermined threshold, the response gain of the control voltage is made smaller than when the absolute value exceeds the predetermined threshold, thereby suppressing overshoot and oscillation of the supply current flowing to the light-emitting circuit.

[0010] In addition, a second embodiment of the present disclosure is a current source circuit that supplies current to a light-emitting circuit for laser processing having one laser diode or multiple laser diodes connected in series with each other, the current source circuit including: a switching circuit having at least one switching element and generating a first AC voltage or a continuous pulse voltage using a DC voltage by the switching operation of the switching element; a DC current generation circuit that supplies a DC supply current to the light-emitting circuit using the first AC voltage or the continuous pulse voltage generated by the switching circuit; a current detection unit that detects the supply current; a drive control unit that controls the switching element of the switching circuit based on a control voltage; and a control voltage generation unit that controls the control voltage so that the absolute value of the difference between the detection value of the current detection unit and a predetermined command current is small, and that, while the detection value of the current detection unit is below the command current, makes the response gain of the control of the control voltage larger when the absolute value exceeds a predetermined threshold value than when the absolute value is below the predetermined threshold value.

[0011] As a result, while the detection value of the current detection unit is below the command current, when the absolute value of the difference between the detection value of the current detection unit and the command current exceeds a predetermined threshold, the response gain of the control voltage is made larger than when the absolute value is below the predetermined threshold, thereby shortening the time it takes for the supply current flowing through the light-emitting circuit to rise, thereby improving the quality of laser processing.

[0012] On the other hand, when the absolute value of the difference is below a predetermined threshold, the response gain of the control voltage is made smaller than when the absolute value exceeds the predetermined threshold, thereby suppressing overshoot and oscillation of the supply current flowing to the light-emitting circuit.

[0013] A third embodiment of the present disclosure is a current source circuit for supplying a current to a light-emitting circuit for laser processing having one laser diode or a plurality of laser diodes connected in series with each other, the current source circuit including at least one switching element, a switching circuit for generating a first AC voltage or a continuous pulse voltage by a switching operation of the switching element using a DC voltage, a DC current generation circuit for supplying a DC supply current to the light-emitting circuit using the first AC voltage or the continuous pulse voltage generated by the switching circuit, a current detection unit for detecting the supply current, and a control voltage for controlling the switch based on the control voltage. and a control voltage generating unit that controls the control voltage so that an absolute value of a difference between a detection value of the current detection unit and a predetermined command current becomes small, and that, while the command current is below the detection value of the current detection unit, when the absolute value exceeds a predetermined first threshold, the response gain of the control of the control voltage is larger than when the command current is below the first threshold, and that, while the detection value of the current detection unit is below the command current, when the absolute value exceeds a predetermined second threshold, the response gain of the control voltage is larger than when the command current is below the second threshold.

[0014] As a result, while the command current is below the detection value of the current detection unit, the response gain of the control of the control voltage is made larger when the absolute value of the difference between the detection value of the current detection unit and the command current exceeds a predetermined first threshold than when the command current is below the first threshold, thereby shortening the time it takes for the supply current to flow through the light-emitting circuit to fall. Also, while the detection value of the current detection unit is below the command current, the response gain of the control voltage is made larger when the absolute value of the difference between the detection value of the current detection unit and the command current exceeds a predetermined second threshold than when the command current is below the second threshold, thereby shortening the time it takes for the supply current to flow through the light-emitting circuit to rise. Therefore, the quality of laser processing can be improved.

[0015] On the other hand, while the command current is below the detection value of the current detection unit, when the absolute value of the difference is below a first threshold, the response gain of the control of the control voltage is made smaller than when the absolute value exceeds the first threshold, thereby suppressing overshoot and oscillation of the supply current flowing to the light-emitting circuit. Similarly, while the detection value of the current detection unit is below the command current, when the absolute value of the difference is below a second threshold, the response gain of the control voltage is made smaller than when the absolute value exceeds the second threshold, thereby suppressing overshoot and oscillation of the supply current flowing to the light-emitting circuit. Effect of the Invention

[0016] According to the present disclosure, it is possible to improve the quality of laser processing and suppress overshoot and oscillation of the supply current flowing to the light emitting circuit. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a direct diode laser device including a current source circuit according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a circuit diagram of a current source circuit according to the first embodiment of the present disclosure. [Diagram 3] FIG. 3 is a circuit diagram of the control voltage generating unit. [Figure 4] FIG. 4 is a timing chart of the detection values ​​of the current detection unit. [Diagram 5] FIG. 5 is a view corresponding to FIG. 2 of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0019] (Embodiment 1) 1 shows a configuration of a direct diode laser device 100 according to a first embodiment of the present disclosure. The direct diode laser device 100 is used to perform cutting, welding, and the like of a workpiece W. The direct diode laser device 100 includes a galvano scanning type laser head 10, a controller 20, a light emitting circuit 30 for laser processing, a current source circuit 40, and an optical fiber 90.

[0020] The galvano scanning type laser head 10 emits laser light LB that is emitted by a light emitting circuit 30 and passes through an optical fiber 90.

[0021] The controller 20 controls the irradiation position of the laser light LB by moving a plurality of galvanometer mirrors (not shown) built into the galvanometer scanning type laser head 10.

[0022] 2, the light-emitting circuit 30 includes one laser diode 31 connected between the first and second nodes N1, N2. Instead of this one laser diode 31, a plurality of laser diodes connected in series may be connected between the first and second nodes N1, N2. The cathode side of the laser diode 31 faces the second node N2. The laser light LB emitted by the light-emitting circuit 30 passes through the optical fiber 90 and is irradiated onto the workpiece W by the galvano scanning type laser head 10.

[0023] The current source circuit 40 supplies a DC current between the first and second nodes N1 and N2 to the light-emitting circuit 30. Specifically, the current source circuit 40 includes a first rectifier circuit 41, a switching circuit 42, a capacitor 43, a DC current generating circuit 44, a current detection unit 48, and a control unit 50.

[0024] The first rectifier circuit 41 converts the power supply voltage output from the AC power supply 200 into a DC voltage and outputs it from a pair of output nodes ON1, ON2. The first rectifier circuit 41 is formed of, for example, a diode bridge.

[0025] The switching circuit 42 is an inverter circuit that generates a first AC voltage according to the voltages of the output nodes ON1, ON2 of the first rectifier circuit 41. Specifically, the switching circuit 42 has a first upper arm switching element 42a and a first lower arm switching element 42b that are connected in series between the pair of output nodes ON1, ON2 of the first rectifier circuit 41, and a second upper arm switching element 42c and a second lower arm switching element 42d that are connected in series between the pair of output nodes ON1, ON2 of the first rectifier circuit 41. A freewheel diode 42e is connected in parallel to each of the switching elements 42a to 42d. The switching circuit 42 generates a first AC voltage using the DC voltage output by the first rectifier circuit 41 by the switching operation of these switching elements 42a to 42d.

[0026] The capacitor 43 is connected between the first rectifier circuit 41 and the switching circuit 42, in parallel with the first rectifier circuit 41 and the switching circuit 42. The capacitor 43 is connected between a pair of output nodes ON1, ON2 of the first rectifier circuit 41.

[0027] The DC current generating circuit 44 uses the first AC voltage generated by the switching circuit 42 to cause a DC supply current to flow through the light-emitting circuit 30. The DC current generating circuit 44 has an isolation transformer 45, a second rectifier circuit 46, and a reactor 47.

[0028] The isolation transformer 45 converts the first AC voltage generated by the switching circuit 42 into a second AC voltage and outputs the second AC voltage. The isolation transformer 45 has a primary coil 45a and a secondary coil 45b. The voltage of the primary coil 45a becomes the first AC voltage, and the voltage of the secondary coil 45b becomes the second AC voltage. The primary coil 45a is connected between a connection point of the first upper arm switching element 42a and the first lower arm switching element 42b and a connection point of the second upper arm switching element 42c and the second lower arm switching element 42d.

[0029] The second rectifier circuit 46 supplies a DC supply current to the laser diode 31 of the light-emitting circuit 30 based on the second AC voltage output by the isolation transformer 45. Specifically, the second rectifier circuit 46 has first and second diodes 46a and 46b. The anode of the first diode 46a is connected to one end of the secondary coil 45b, and the anode of the second diode 46b is connected to the other end of the secondary coil 45b. The cathodes of the first and second diodes 46a and 46b are connected to a first node N1.

[0030] The reactor 47 is connected between a middle portion of the secondary coil 45b and the second node N2.

[0031] The current detector 48 detects the supply current flowing through the laser diode 31 of the light-emitting circuit 30 .

[0032] The control unit 50 includes a drive control unit 51 and a control voltage generating unit 52 .

[0033] The drive control unit 51 controls the switching elements 42a to 42d of the switching circuit 42 based on a control voltage Vc generated by a control voltage generation unit 52, which will be described later in detail. Here, the control voltage Vc corresponds to a duty ratio of a period during which the switching circuit 42 supplies a voltage to the isolation transformer 45.

[0034] The control voltage generating unit 52 controls the control voltage Vc based on the detection value Im of the current detecting unit 48 and a predetermined command current Ic so that the absolute value of the difference between the detection value Im and the command current Ic becomes smaller. Furthermore, while the command current Ic is below the detection value Im, when the absolute value of the difference between the detection value Im and the command current Ic exceeds a predetermined first threshold, the control voltage generating unit 52 increases the response gain of the control of the control voltage Vc compared to when the difference is below the first threshold, and while the detection value Im is below the command current Ic, when the absolute value exceeds a predetermined second threshold, the control voltage generating unit 52 increases the response gain of the control of the control voltage Vc compared to when the difference is below the second threshold.

[0035] Specifically, the control voltage generating unit 52 is configured with a hardware circuit, and includes a differential voltage output circuit 521, first to fourth comparison voltage output circuits 522 to 525, first to fourth addition voltage output circuits 526 to 529, and a control voltage output circuit 530, as shown in FIG.

[0036] The differential voltage output circuit 521 is a differential amplifier that, based on the command current Ic and the detection value Im of the current detection unit 48, outputs a differential voltage Vdif obtained by amplifying the difference obtained by subtracting the detection value Im from the command current Ic.

[0037] The differential voltage output circuit 521 has first to fourth resistors 521a to 521d and a first operational amplifier 521e.

[0038] One end of the first resistor 521a is connected to an input terminal to which the detection value Im is input, and the other end of the first resistor 521a is connected to an inverting input terminal of the first operational amplifier 521e.

[0039] One end of the second resistor 521b is connected to the inverting input terminal of the first operational amplifier 521e, and the other end of the second resistor 521b is connected to the output terminal of the first operational amplifier 521e.

[0040] One end of the third resistor 521c is connected to an input terminal to which the command current Ic is input, and the other end of the third resistor 521c is connected to a non-inverting input terminal of the first operational amplifier 521e.

[0041] One end of the fourth resistor 521d is connected to the non-inverting input terminal of the first operational amplifier 521e, and the other end of the fourth resistor 521d is grounded.

[0042] The output of the first operational amplifier 521e becomes the differential voltage Vdif.

[0043] The first comparison voltage output circuit 522 is a differential amplifier that outputs a first comparison voltage Vcm1 obtained by amplifying the difference between the command current Ic and the detection value Im based on the command current Ic and the detection value Im of the current detection unit 48. The first comparison voltage output circuit 522 has fifth to eighth resistors 522a to 522d and a second operational amplifier 522e.

[0044] The second comparison voltage output circuit 523 is a differential amplifier that outputs a second comparison voltage Vcm2 obtained by amplifying the difference between the command current Ic and the detection value Im based on the command current Ic and the detection value Im of the current detection unit 48. The second comparison voltage output circuit 523 has ninth to twelfth resistors 523a to 523d ​​and a third operational amplifier 523e.

[0045] The third comparison voltage output circuit 524 is a differential amplifier that outputs a third comparison voltage Vcm3 obtained by amplifying the difference between the command current Ic and the detection value Im based on the command current Ic and the detection value Im of the current detection unit 48. The third comparison voltage output circuit 524 has thirteenth to sixteenth resistors 524a to 524d and a fourth operational amplifier 524e.

[0046] The fourth comparison voltage output circuit 525 is a differential amplifier that outputs a fourth comparison voltage Vcm4 by amplifying the difference between the command current Ic and the detection value Im, based on the command current Ic and the detection value Im of the current detection unit 48. The fourth comparison voltage output circuit 525 has seventeenth to twentieth resistors 525a to 525d and a fifth operational amplifier 525e.

[0047] The connection relationship between the resistors and the operational amplifiers in the first to fourth comparison voltage output circuits 522 to 525 is the same as that in the differential voltage output circuit 521, and therefore a detailed description thereof will be omitted. The resistance values ​​of the fifth to twentieth resistors 522a to 522d, 523a to 523d, 524a to 524d, and 525a to 525d included in the first to fourth comparison voltage output circuits 522 to 525 are set, for example, so that the amplification factors of the first to fourth comparison voltage output circuits 522 to 525 are the same. Note that the resistance values ​​of the fifth to twentieth resistors 522a to 522d, 523a to 523d, 524a to 524d, and 525a to 525d may be set, for example, so that the amplification factors of the first to fourth comparison voltage output circuits 522 to 525 are different from each other.

[0048] The first addition voltage output circuit 526 has a first comparison circuit 526a and a first selector 526b.

[0049] The first comparison circuit 526a outputs a comparison result between the first comparison voltage Vcm1 output by the first comparison voltage output circuit 522 and a predetermined first comparison value Vth1. When the first comparison voltage Vcm1 is lower than the first comparison value Vth1, the first comparison circuit 526a outputs a high level. On the other hand, when the first comparison voltage Vcm1 is equal to or higher than the first comparison value Vth1, the first comparison circuit 526a outputs a low level. The first comparison value Vth1 is set to a negative value.

[0050] When the first comparison circuit 526a outputs a high level, the first selector 526b selects the first comparison voltage Vcm1 and outputs it as the first addition voltage Vad1, whereas when the first comparison circuit 526a outputs a low level, the first selector 526b selects 0V (ground voltage) and outputs it as the first addition voltage Vad1.

[0051] Therefore, while the first comparison voltage Vcm1 is negative, i.e., while the command current Ic is below the detection value Im, when the first comparison voltage Vcm1 output by the first comparison voltage output circuit 522 is below a predetermined first comparison value Vth1, the first addition voltage output circuit 526 outputs, as the first addition voltage Vad1, a voltage (first comparison voltage Vcm1) that is lower than when the first comparison voltage Vcm1 exceeds the first comparison value Vth1.

[0052] The second addition voltage output circuit 527 has a second comparison circuit 527a and a second selector 527b.

[0053] The second comparison circuit 527a outputs a comparison result between the second comparison voltage Vcm2 output by the second comparison voltage output circuit 523 and a predetermined second comparison value Vth2. When the second comparison voltage Vcm2 is lower than the second comparison value Vth2, the second comparison circuit 527a outputs a high level. On the other hand, when the second comparison voltage Vcm2 is equal to or higher than the second comparison value Vth2, the second comparison circuit 527a outputs a low level. The second comparison value Vth2 is set to a negative value lower than the first comparison value Vth1.

[0054] The second selector 527b selects the second comparison voltage Vcm2 and outputs it as the second addition voltage Vad2 when the second comparison circuit 527a outputs a high level, and selects 0V (ground voltage) and outputs it as the second addition voltage Vad2 when the second comparison circuit 527a outputs a low level.

[0055] Therefore, while the second comparison voltage Vcm2 is negative, i.e., while the command current Ic is below the detection value Im, when the second comparison voltage Vcm2 output by the second comparison voltage output circuit 523 is below a predetermined second comparison value Vth2, the second addition voltage output circuit 527 outputs, as the second addition voltage Vad2, a voltage (second comparison voltage Vcm2) that is lower than when the second comparison voltage Vcm2 exceeds the second comparison value Vth2.

[0056] The third addition voltage output circuit 528 has a third comparison circuit 528a and a third selector 528b.

[0057] The third comparison circuit 528a outputs a comparison result between the third comparison voltage Vcm3 output by the third comparison voltage output circuit 524 and a predetermined third comparison value Vth3. When the third comparison voltage Vcm3 exceeds the third comparison value Vth3, the third comparison circuit 528a outputs a high level. On the other hand, when the third comparison voltage Vcm3 is equal to or lower than the third comparison value Vth3, the third comparison circuit 528a outputs a low level. The third comparison value Vth3 is set to a positive value.

[0058] When the third comparison circuit 528a outputs a high level, the third selector 528b selects the third comparison voltage Vcm3 and outputs it as the third addition voltage Vad3, whereas when the third comparison circuit 528a outputs a low level, the third selector 528b selects 0V (ground voltage) and outputs it as the third addition voltage Vad3.

[0059] Therefore, while the third comparison voltage Vcm3 is positive, i.e., while the detection value Im is below the command current Ic, when the third comparison voltage Vcm3 output by the third comparison voltage output circuit 524 exceeds a predetermined third comparison value Vth3, the third addition voltage output circuit 528 outputs, as the third addition voltage Vad3, a voltage (third comparison voltage Vcm3) that is higher than when the third comparison voltage Vcm3 falls below the third comparison value Vth3.

[0060] The fourth addition voltage output circuit 529 has a fourth comparison circuit 529a and a fourth selector 529b.

[0061] The fourth comparison circuit 529a outputs a comparison result between the fourth comparison voltage Vcm4 output by the fourth comparison voltage output circuit 525 and a predetermined fourth comparison value Vth4. When the fourth comparison voltage Vcm4 exceeds the fourth comparison value Vth4, the fourth comparison circuit 529a outputs a high level. On the other hand, when the fourth comparison voltage Vcm4 is equal to or lower than the fourth comparison value Vth4, the fourth comparison circuit 529a outputs a low level. The fourth comparison value Vth4 is set to a positive value higher than the third comparison value Vth3.

[0062] When the fourth comparison circuit 529a outputs a high level, the fourth selector 529b selects the fourth comparison voltage Vcm4 and outputs it as the fourth addition voltage Vad4, whereas when the fourth comparison circuit 529a outputs a low level, the fourth selector 529b selects 0V (ground voltage) and outputs it as the fourth addition voltage Vad4.

[0063] Therefore, while the fourth comparison voltage Vcm4 is positive, i.e., while the detection value Im is below the command current Ic, when the fourth comparison voltage Vcm4 output by the fourth comparison voltage output circuit 525 exceeds a predetermined fourth comparison value Vth4, the fourth addition voltage output circuit 529 outputs, as the fourth addition voltage Vad4, a voltage (fourth comparison voltage Vcm4) that is higher than when the fourth comparison voltage Vcm4 falls below the fourth comparison value Vth4.

[0064] The control voltage output circuit 530 outputs a control voltage Vc based on the differential voltage Vdif and the first to fourth addition voltages Vad1 to Vad4 such that the control voltage Vc becomes higher as the sum of the differential voltage Vdif and the first to fourth addition voltages Vad1 to Vad4 increases. Specifically, the control voltage output circuit 530 has an adding and integrating circuit 531 and an inverting amplifier circuit 532 as a control voltage generating circuit.

[0065] The summing integration circuit 531 integrates the sum of the differential voltage Vdif and the first to fourth addition voltages Vad1 to Vad4, inverts the result, and outputs it.

[0066] The summing integration circuit 531 has twenty-first to twenty-sixth resistors 531a to 531f, a capacitor 531g, and a sixth operational amplifier 531h.

[0067] One end of the twenty-first resistor 531a is connected to the output of the differential voltage output circuit 521, i.e., the output terminal of the first operational amplifier 521e. The other end of the twenty-first resistor 531a is connected to the inverting input terminal of the sixth operational amplifier 531h.

[0068] One end of the twenty-second resistor 531b is connected to the output of the first addition voltage output circuit 526, i.e., the output of the first selector 526b. The other end of the twenty-second resistor 531b is connected to the inverting input terminal of the sixth operational amplifier 531h.

[0069] One end of the resistor 531c is connected to the output of the second addition voltage output circuit 527, i.e., the output of the second selector 527b. The other end of the resistor 531c is connected to the inverting input terminal of the sixth operational amplifier 531h.

[0070] One end of the resistor 531d is connected to the output of the third addition voltage output circuit 528, i.e., the output of the third selector 528b. The other end of the resistor 531d is connected to the inverting input terminal of the sixth operational amplifier 531h.

[0071] One end of the twenty-fifth resistor 531e is connected to the output of the fourth addition voltage output circuit 529, i.e., the output of the fourth selector 529b. The other end of the twenty-fifth resistor 531e is connected to the inverting input terminal of the sixth operational amplifier 531h.

[0072] A resistor 531f and a capacitor 531g are connected in series between the inverting input terminal and the output terminal of the sixth operational amplifier 531h in this order from the inverting input terminal side. The non-inverting input terminal of the sixth operational amplifier 531h is grounded.

[0073] The inverting amplifier circuit 532 inverts and amplifies the output of the summing and integrating circuit 531, and outputs the result. The inverting amplifier circuit 532 has twenty-seventh and twenty-eighth resistors 532a and 532b, and a seventh operational amplifier 532c.

[0074] One end of the twenty-seventh resistor 532a is connected to the output of the summing and integrating circuit 531, i.e., the output terminal of the sixth operational amplifier 531h. The other end of the twenty-seventh resistor 532a is connected to the inverting input terminal of the seventh operational amplifier 532c.

[0075] One end of the resistor 532b is connected to the inverting input terminal of the seventh operational amplifier 532c, and the other end of the resistor 532b is connected to the output terminal of the seventh operational amplifier 532c.

[0076] In addition, the 26th resistor 531f, the capacitor 531g and the sixth operational amplifier 531h of the summing integration circuit 531 constitute an integration circuit 541 that outputs a voltage corresponding to the integral value of the input voltage (the voltage at the inverting input terminal of the sixth operational amplifier 531h).

[0077] The inverting amplifier circuit 532 inverts and amplifies the output of the integrating circuit 541, and outputs the result. That is, the inverting amplifier circuit 532 generates the control voltage Vc based on the output of the integrating circuit 541.

[0078] The change amount per unit time of the voltage of the capacitor 531g of the integrating circuit 541 (charge / discharge speed) changes according to the voltage of the inverting input terminal of the sixth operational amplifier 531h. Therefore, it can be said that the difference voltage output circuit 521, the first to fourth comparison voltage output circuits 522 to 525, the first to fourth addition voltage output circuits 526 to 529, and the twenty-first to twenty-fifth resistors 531a to 531e constitute a switching circuit 542 that changes the change amount per unit time of the output voltage of the integrating circuit 541. When the command current Ic is below the detection value Im of the current detection unit 48 and the first comparison voltage Vcm1 is below the first comparison value Vth1, the switching circuit 542 increases the change amount per unit time of the output voltage of the integrating circuit 541 compared to when the first comparison voltage Vcm1 exceeds the first comparison value Vth1. Furthermore, while the command current Ic is below the detection value Im of the current detection unit 48, when the second comparison voltage Vcm2 is below the second comparison value Vth2, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the second comparison voltage Vcm2 exceeds the second comparison value Vth2. On the other hand, while the detection value Im of the current detection unit 48 is below the command current Ic, when the third comparison voltage Vcm3 exceeds the third comparison value Vth3, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the third comparison voltage Vcm3 is below the third comparison value Vth3. In addition, when the detection value Im of the current detection unit 48 is below the command current Ic, when the fourth comparison voltage Vcm4 exceeds the fourth comparison value Vth4, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the fourth comparison voltage Vcm4 is below the fourth comparison value Vth4.

[0079] 4, graph W1 shows the supply current at the start-up of the current source circuit 40 configured as described above. Graph W2 shows the supply current when the response gain of the control of the control voltage Vc is low. Graph W3 shows the supply current when the response gain of the control of the control voltage Vc is high.

[0080] In the current source circuit 40 configured as described above, in order to raise the supply current flowing to the light-emitting circuit 30, the command current Ic and the detection value Im (supply current) are set to a first current value I S From this state, the command current Ic is changed to the first current value I S A second current value I L When the switching circuit 542 is switched to the third comparison voltage Vcm3, the third and fourth comparison voltages Vcm3 and Vcm4 become positive voltages. Then, the state in which the third comparison voltage Vcm3 exceeds the third comparison value Vth3 and the fourth comparison voltage Vcm4 exceeds the fourth comparison value Vth4 continues. Therefore, the third addition voltage output circuit 528 outputs, as the third addition voltage Vad3, a voltage (third comparison voltage Vcm3) higher than when the third comparison voltage Vcm3 falls below the third comparison value Vth3. That is, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the third comparison voltage Vcm3 falls below the third comparison value Vth3. Also, the fourth addition voltage output circuit 529 outputs, as the fourth addition voltage Vad4, a voltage (fourth comparison voltage Vcm4) higher than when the fourth comparison voltage Vcm4 falls below the fourth comparison value Vth4. That is, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the fourth comparison voltage Vcm4 is lower than the fourth comparison value Vth4. Therefore, the control voltage output circuit 530 outputs a relatively high control voltage Vc, and the amount of increase per unit time of the supply current becomes large. Also, the amount of change per unit time of the output voltage of the integrating circuit 541 becomes relatively large.

[0081] After that, when the supply current reaches the fourth current threshold Ith4 corresponding to the fourth comparison value Vth4, the third comparison voltage Vcm3 remains above the third comparison value Vth3, but the fourth comparison voltage Vcm4 falls below the fourth comparison value Vth4. As a result, the fourth addition voltage output circuit 529 outputs, as the fourth addition voltage Vad4, a voltage lower than when the fourth comparison voltage Vcm4 exceeds the fourth comparison value Vth4. In addition, the switching circuit 542 reduces the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the fourth comparison voltage Vcm4 exceeds the fourth comparison value Vth4. The fourth addition voltage Vad4 at this time becomes 0V (ground voltage). Therefore, the control voltage Vc output by the control voltage output circuit 530 becomes slightly lower, and the increase in the supply current per unit time becomes smaller. In addition, the amount of change per unit time of the output voltage of the integrating circuit 541 also becomes slightly smaller.

[0082] Thereafter, when the supply current exceeds the third current threshold Ith3 corresponding to the third comparison value Vth3, the third comparison voltage Vcm3 falls below the third comparison value Vth3. As a result, the third addition voltage output circuit 528 outputs, as the third addition voltage Vad3, a voltage lower than when the third comparison voltage Vcm3 exceeds the third comparison value Vth3. In addition, the switching circuit 542 reduces the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the third comparison voltage Vcm3 exceeds the third comparison value Vth3. At this time, the third addition voltage Vad3 becomes 0V (ground voltage). Therefore, the control voltage Vc output by the control voltage output circuit 530 becomes even lower, and the amount of increase per unit time of the supply current becomes even smaller. In addition, the amount of change per unit time of the output voltage of the integrating circuit 541 also becomes even smaller.

[0083] In this way, when the fourth comparison voltage Vcm4 exceeds the fourth comparison value Vth4, i.e., when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds the predetermined threshold (second threshold) corresponding to the fourth comparison value Vth4, the control voltage generation unit 52 increases the increase amount of the supply current per unit time more than when the fourth comparison voltage Vcm4 falls below the fourth comparison value Vth4, i.e., when the absolute value falls below the predetermined threshold. In other words, when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds the predetermined threshold (second threshold) corresponding to the fourth comparison value Vth4, the control voltage generation unit 52 increases the response gain of control of the control voltage Vc more than when the absolute value falls below the predetermined threshold. In addition, when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold (second threshold) corresponding to the fourth comparison value Vth4, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the absolute value falls below the predetermined threshold.

[0084] Furthermore, when the third comparison voltage Vcm3 exceeds the third comparison value Vth3, i.e., when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold (second threshold) corresponding to the third comparison value Vth3, the control voltage generation unit 52 increases the increase amount of the supply current per unit time more than when the third comparison voltage Vcm3 falls below the third comparison value Vth3, i.e., when the absolute value falls below the predetermined threshold. In other words, when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds the predetermined threshold (second threshold) corresponding to the third comparison value Vth3, the control voltage generation unit 52 increases the response gain of control of the control voltage Vc more than when the absolute value falls below the predetermined threshold. In addition, when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold (second threshold) corresponding to the third comparison value Vth3, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the absolute value falls below the predetermined threshold.

[0085] In this way, when the absolute value of the difference between the detection value Im and the command current Ic is relatively large during rise, the response gain of the control of the control voltage Vc is made relatively large, so that the time required for the supply current to flow to the light-emitting circuit 30 to rise can be shortened compared to graph W2, thereby improving the quality of the laser processing. Also, when the absolute value of the difference between the detection value Im and the command current Ic is relatively small, the response gain of the control of the control voltage Vc can be made relatively small, thereby suppressing overshoot and oscillation of the supply current to the light-emitting circuit 30 as shown in graph W3.

[0086] In addition, the detection value Im (supply current) is the second current value I L After the command current Ic rises to the first current value I S When the first and second comparison voltages Vcm1 and Vcm2 are lowered to 1, the first and second comparison voltages Vcm1 and Vcm2 become negative, and the state in which the first comparison voltage Vcm1 falls below the first comparison value Vth1 and the second comparison voltage Vcm2 falls below the second comparison value Vth2 continues. Therefore, the first addition voltage output circuit 526 outputs, as the first addition voltage Vad3, a voltage (first comparison voltage Vcm1) lower than when the first comparison voltage Vcm1 exceeds the first comparison value Vth1. That is, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the first comparison voltage Vcm1 exceeds the first comparison value Vth1. Also, the second addition voltage output circuit 527 outputs, as the second addition voltage Vad2, a voltage (second comparison voltage Vcm2) lower than when the second comparison voltage Vcm2 exceeds the second comparison value Vth2. That is, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the second comparison voltage Vcm2 exceeds the second comparison value Vth2. Therefore, the control voltage output circuit 530 outputs a relatively low control voltage Vc, and the amount of decrease per unit time of the supply current becomes large. Also, the amount of change per unit time of the output voltage of the integrating circuit 541 becomes relatively large.

[0087] Then, when the supply current reaches a second current threshold (not shown) corresponding to the second comparison value Vth2, the first comparison voltage Vcm1 remains below the first comparison value Vth1, but the second comparison voltage Vcm2 becomes equal to or higher than the second comparison value Vth2. As a result, the second addition voltage output circuit 527 outputs, as the second addition voltage Vad2, a voltage higher than when the second comparison voltage Vcm2 falls below the second comparison value Vth2. Also, the switching circuit 542 reduces the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the second comparison voltage Vcm2 falls below the second comparison value Vth2. At this time, the second addition voltage Vad2 becomes 0V (ground voltage). Therefore, the control voltage Vc output by the control voltage output circuit 530 becomes slightly higher, and the amount of decrease per unit time of the supply current becomes smaller. Also, the amount of change per unit time of the output voltage of the integrating circuit 541 becomes slightly smaller.

[0088] Thereafter, when the supply current decreases to a first current threshold (not shown) corresponding to the first comparison value Vth1, the first comparison voltage Vcm1 becomes equal to or higher than the first comparison value Vth1. As a result, the first addition voltage output circuit 526 outputs, as the first addition voltage Vad1, a voltage higher than when the first comparison voltage Vcm1 falls below the first comparison value Vth1. Also, the switching circuit 542 reduces the amount of change per unit time of the output voltage of the integrating circuit 541 compared to when the first comparison voltage Vcm1 falls below the first comparison value Vth1. At this time, the first addition voltage Vad1 becomes 0V (ground voltage). Therefore, the control voltage Vc output by the control voltage output circuit 530 becomes higher, and the amount of decrease per unit time of the supply current becomes smaller. Also, the amount of change per unit time of the output voltage of the integrating circuit 541 becomes smaller.

[0089] In this way, when the second comparison voltage Vcm2 falls below the second comparison value Vth2, i.e., when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold (first threshold) corresponding to the second comparison value Vth2, the control voltage generation unit 52 increases the amount of decrease in the supply current per unit time compared to when the second comparison voltage Vcm2 exceeds the second comparison value Vth2, i.e., when the absolute value falls below the predetermined threshold. In other words, when the absolute value of the difference between the detection value Im and the command current Ic exceeds a predetermined threshold (first threshold) corresponding to the second comparison value Vth2, the control voltage generation unit 52 increases the response gain of control of the control voltage Vc compared to when the absolute value falls below the predetermined threshold. In addition, when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold (first threshold) corresponding to the second comparison value Vth2, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the absolute value falls below the predetermined threshold.

[0090] Furthermore, when the first comparison voltage Vcm1 falls below the first comparison value Vth1, i.e., when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold (first threshold) corresponding to the first comparison value Vth1, the control voltage generation unit 52 increases the amount of decrease in the supply current per unit time compared to when the first comparison voltage Vcm1 exceeds the first comparison value Vth1, i.e., when the absolute value falls below the predetermined threshold. In other words, when the absolute value of the difference between the detection value Im and the command current Ic exceeds a predetermined threshold (first threshold) corresponding to the first comparison value Vth1, the control voltage generation unit 52 increases the response gain of control of the control voltage Vc compared to when the absolute value falls below the predetermined threshold. In addition, when the absolute value of the difference between the detection value Im of the current detection unit 48 and the command current Ic exceeds a predetermined threshold value (first threshold value) corresponding to the first comparison value Vth1, the switching circuit 542 increases the amount of change per unit time of the output voltage of the integration circuit 541 compared to when the absolute value falls below the predetermined threshold value.

[0091] In this way, when the absolute value of the difference between the detection value Im and the command current Ic is relatively large during the fall, the response gain of the control of the control voltage Vc is made relatively large, thereby shortening the time it takes for the supply current flowing to the light-emitting circuit 30 to fall, thereby improving the quality of the laser processing. Also, when the absolute value of the difference between the detection value Im and the command current Ic is relatively small, the response gain of the control of the control voltage Vc is made relatively small, thereby suppressing overshoot and oscillation of the supply current flowing to the light-emitting circuit 30.

[0092] According to the first embodiment, the drive control unit 51 and the control voltage generating unit 52 are configured as hardware circuits, so that the response of the operation of the switching circuit 42 can be made faster and the time required for the supply current flowing through the light-emitting circuit 30 to approach the command current Ic can be shortened, compared to the case where the functions of the drive control unit 51 and the control voltage generating unit 52 are realized by having a computer execute a program. Therefore, by applying this to the galvano scanning type laser head 10 that can realize a high-speed current response and control the laser light LB at high speed, advanced laser processing can be realized.

[0093] (Embodiment 2) Fig. 5 is a diagram corresponding to Fig. 2 of embodiment 2. In embodiment 2, current source circuit 40 includes, instead of first rectifier circuit 41 and capacitor 43, a voltage source circuit 54 that outputs a DC voltage to a pair of output nodes ON1, ON2.

[0094] Also, the switching circuit 42 has only one N-channel MOSFET 55 whose drain is connected to one output node ON1. The switching circuit 42 generates a continuous pulse voltage by the switching operation of the N-channel MOSFET 55 using the DC voltage output by the voltage source circuit 54.

[0095] The DC current generating circuit 44 includes a diode 56a and a reactor 56b.

[0096] The anode of the diode 56 a is connected to the other output node ON 2 , and the cathode of the diode 56 a is connected to the source of the N-channel MOSFET 55 .

[0097] One end of the reactor 56b is connected to the source of the N-channel MOSFET 55, and the other end of the reactor 56b is connected to the first node N1.

[0098] Moreover, the drive control section 51 of the control section 50 controls the N-channel MOSFET 55 of the switching circuit 42 based on the control voltage Vc.

[0099] In place of the diode 56a, a MOSFET whose on / off is controlled by the control unit 50 or the like may be provided.

[0100] The other configurations and effects are the same as those of the first embodiment, so the same configurations are given the same reference numerals and detailed descriptions thereof are omitted.

[0101] In the first embodiment, the switching circuit 42 is provided with four switching elements 42a to 42d, and in the second embodiment, the switching circuit 42 is provided with one switching element. However, the switching circuit 42 may have a number of switching elements other than one or four. [Industrial Applicability]

[0102] The current source circuit and a direct diode laser device including the same disclosed herein can improve the quality of laser processing and suppress overshoot and oscillation of the supply current flowing to the light-emitting circuit, and are useful as a current source circuit that flows current to a light-emitting circuit for laser processing having at least one laser diode, and a direct diode laser device including the same. [Explanation of symbols]

[0103] 10 Galvano scanning laser head 30 Light emitting circuit 31 Laser Diode 40 Current source circuit 42 Switching Circuits 42a~42d Switching elements 44 DC current generation circuit 45 Isolation transformer 46 Second rectifier circuit 48 Current detection section 51 Drive control unit 52 Control voltage generator 55 N-channel MOSFET (switching element) 532 Inverting amplifier circuit (control voltage generation circuit) 541 Integral circuit 542 Switching circuit Ic command current Im detection value Vc Control voltage Vad1 1st voltage for addition Vad2 Second voltage for addition Vad3 Third voltage for addition Vad4 4th voltage for addition Vdif Differential voltage 90 Optical Fiber 100 Laser processing equipment LB laser light W work

Claims

1. A current source circuit for supplying a current to a light emitting circuit for laser processing having one laser diode or a plurality of laser diodes connected in series with each other, a switching circuit having at least one switching element, the switching circuit generating a first AC voltage or a continuous pulse voltage using a DC voltage by a switching operation of the switching element; a DC current generating circuit that uses the first AC voltage or the continuous pulse voltage generated by the switching circuit to supply a DC current to the light-emitting circuit; A current detection unit that detects the supply current; a drive control unit that controls the switching element of the switching circuit based on a control voltage; a control voltage generating unit that controls the control voltage so that an absolute value of a difference between a detection value of the current detection unit and a predetermined command current becomes small, and that, while the command current is below the detection value of the current detection unit, when the absolute value exceeds a predetermined threshold, makes a response gain of the control of the control voltage larger than when the command current is below the predetermined threshold.

2. A current source circuit for supplying a current to a light emitting circuit for laser processing having one laser diode or a plurality of laser diodes connected in series with each other, a switching circuit having at least one switching element, the switching circuit generating a first AC voltage or a continuous pulse voltage using a DC voltage by a switching operation of the switching element; a DC current generating circuit that uses the first AC voltage or the continuous pulse voltage generated by the switching circuit to supply a DC current to the light-emitting circuit; A current detection unit that detects the supply current; a drive control unit that controls the switching element of the switching circuit based on a control voltage; a control voltage generating unit that controls the control voltage so that an absolute value of a difference between a detection value of the current detection unit and a predetermined command current becomes small, and that, while the detection value of the current detection unit is below the command current, makes a response gain of the control of the control voltage larger when the absolute value exceeds a predetermined threshold value than when the absolute value is below the predetermined threshold value.

3. A current source circuit for supplying a current to a light emitting circuit for laser processing having one laser diode or a plurality of laser diodes connected in series with each other, a switching circuit having at least one switching element, the switching circuit generating a first AC voltage or a continuous pulse voltage using a DC voltage by a switching operation of the switching element; a DC current generating circuit that uses the first AC voltage or the continuous pulse voltage generated by the switching circuit to supply a DC current to the light-emitting circuit; A current detection unit that detects the supply current; a drive control unit that controls the switching element of the switching circuit based on a control voltage; a control voltage generation unit that controls the control voltage so that an absolute value of a difference between a detection value of the current detection unit and a predetermined command current becomes small, and when the absolute value exceeds a predetermined first threshold, a response gain of the control voltage is made larger while the command current is below the detection value of the current detection unit than when the command current is below the first threshold, and when the detection value of the current detection unit is below the command current, a response gain of the control voltage is made larger when the absolute value exceeds a predetermined second threshold than when the command current is below the second threshold.

4. 4. The current source circuit according to claim 1, 2. A current source circuit, wherein the control voltage generating unit is configured as a hardware circuit.

5. 4. The current source circuit according to claim 1, The control voltage generating unit an integrating circuit that outputs a voltage corresponding to an integral value of an input voltage; a control voltage generating circuit that generates the control voltage based on an output voltage of the integrating circuit; a switching circuit that, while the command current is below a detection value of the current detection unit, increases an amount of change per unit time of the output voltage of the integrating circuit when the absolute value exceeds the predetermined threshold value compared to when the command current is below the predetermined threshold value.

6. 4. The current source circuit according to claim 2, The control voltage generating unit an integrating circuit that outputs a voltage corresponding to an integral value of an input voltage; a control voltage generating circuit that generates the control voltage based on an output voltage of the integrating circuit; a switching circuit that, while a detection value of the current detection unit is below the command current, when the absolute value exceeds the predetermined threshold, increases a change amount per unit time of the output voltage of the integrating circuit compared to when the detection value is below the predetermined threshold.

7. 4. The current source circuit according to claim 1, the switching circuit is an inverter circuit having four of the switching elements, the DC current generating circuit includes: an isolation transformer that converts the first AC voltage generated by the inverter circuit into a second AC voltage and outputs the second AC voltage; and a rectifier circuit that causes the supply current to flow to the light-emitting circuit based on the second AC voltage output by the isolation transformer.

8. A current source circuit according to any one of claims 1 to 3, The light emitting circuit; an optical fiber through which the laser light emitted by the light emitting circuit passes; and a head for emitting laser light that has passed through the optical fiber.

9. 9. The direct diode laser device according to claim 8, 11. A direct diode laser device, wherein the head is a galvano scanning type laser head.

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