Power source for laser processing machines and direct diode laser device with the same

Abstract

To switch a light-emitting circuit from ON to OFF at high speed.SOLUTION: A power source for laser processing machines is provided with: a differential signal output circuit 535 which outputs a differential signal Vdif corresponding to the difference between a detection value Im from a current detection section and a predetermined command current Ic; a control voltage output circuit 536 which outputs a control voltage Vc based on the differential signal Vdif so as to reduce the absolute value of the difference between the detection value Im and the command current Ic; and a switching stop circuit 54 which, when the command current Ic is lower than a predetermined threshold Ith, applies a predetermined voltage to the transmission path of the differential signal Vdif to cause the control voltage output circuit 536 to output a control voltage Vc making a duty ratio of a first AC voltage become 0.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a power supply for a laser processing machine that supplies current to a light emitting circuit for laser processing having at least one laser diode, and a direct diode laser device including the same. [Background technology]

[0002] Patent Document 1 discloses a power supply for a laser processing machine that supplies a current to a light-emitting circuit for laser processing having at least one laser diode. This power supply for a laser processing machine includes a switching circuit having at least one switching element and generating an AC voltage using a DC voltage by the switching operation of the switching element, a DC current generating 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2005-209759 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in a power supply for a laser processing machine such as that disclosed in Patent Document 1, when the command current is switched from a predetermined current value greater than 0A to 0A in order to switch the supply current from the predetermined current value to 0A, it takes time for the supply current to converge from an oscillating state to 0A due to feedback control, and the light emitting circuit continues to emit light even after the command current is switched to 0A.

[0005] The present disclosure has been made in consideration of the above points, and has as its object to quickly switch a light emission circuit from on to off. [Means for solving the problem]

[0006] In order to achieve the above object, a first embodiment of the present disclosure is a power supply for a laser processing machine that supplies 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 power supply including at least one switching element, a switching circuit that generates a first AC voltage or a continuous pulse voltage using a DC voltage by 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, and a duty ratio of the first AC voltage or the continuous pulse voltage. a differential signal output circuit that outputs a differential signal corresponding to the difference between the detection value of the current detection unit and a predetermined command current; a control voltage output circuit that outputs the control voltage based on the differential signal so that the absolute value of the difference between the detection value and the command current becomes small; and a switching stop circuit that applies a predetermined applied voltage to a transmission path of the differential signal or a transmission path of a signal based on the differential signal in the control voltage output circuit when the command current is less than a predetermined threshold, thereby causing the control voltage output circuit to output a control voltage that sets the duty ratio to 0.

[0007] As a result, when the command current is switched from a predetermined current value greater than 0 A to 0 A, the switching stop circuit applies a predetermined voltage to the transmission path of the differential signal or the transmission path of the signal based on the differential signal in the control voltage output circuit. This makes it possible to cause the control voltage output circuit to output a control voltage that sets the duty ratio to 0 more quickly than when no switching stop circuit is provided. Therefore, the supply current can be quickly set to 0, and the light-emitting circuit can be quickly switched from on to off. Effect of the Invention

[0008] According to the present disclosure, the light emitting circuit can be switched from on to off quickly. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a blue direct diode laser device equipped with a power supply for a laser processing machine according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a circuit diagram of the power supply for a laser processing machine according to the first embodiment of the present disclosure. [Diagram 3] FIG. 3 is a circuit diagram of the control voltage generating circuit and the switching stopping circuit. [Figure 4] FIG. 4 is a state transition diagram illustrating the operation of the error detection microcomputer. [Diagram 5] FIG. 5 is a view equivalent to FIG. 3 of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the preferred embodiments of the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its uses.

[0011] (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 laser head 10, a controller 20, a light emitting circuit 30, a power supply 40 for a laser processing machine, and an optical fiber 90.

[0012] The laser head 10 emits laser light LB that is emitted by the light emitting circuit 30 and passes through an optical fiber 90 .

[0013] The controller 20 outputs a current command, a supply current mode (standby state, simmer state, main state), and the like in response to a user input.

[0014] As shown in Fig. 2, the light-emitting circuit 30 includes a plurality of laser diodes 31 connected in series between the first and second nodes N1 and N2. The plurality of laser diodes 31 constitute a DDL (direct diode laser). Instead of the plurality of laser diodes 31, one laser diode may be connected between the first and second nodes N1 and 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 laser head 10.

[0015] The power supply 40 for a laser processing machine supplies a DC current between the first and second nodes N1 and N2 to the light emitting circuit 30. Specifically, the power supply 40 for a laser processing machine has a first rectifier circuit 41, a switching circuit 42, a DC link capacitor 43, a DC current generating circuit 44, a current detection unit 48a, a voltage detection unit 48b, first and second capacitors 49a and 49b, a control board 51, and a drive circuit 57.

[0016] 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.

[0017] 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.

[0018] The DC link capacitor 43 is connected between the first rectifier circuit 41 and the switching circuit 42, and in parallel with the first rectifier circuit 41 and the switching circuit 42. The DC link capacitor 43 is connected between a pair of output nodes ON1, ON2 of the first rectifier circuit 41. A first reactor L is connected between the DC link capacitor 43 and one output node ON1 of the first rectifier circuit 41.

[0019] 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 second reactor 47.

[0020] The insulating 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 insulating 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. A capacitor 42f is connected between the primary coil 45a and the connection point of the first upper arm switching element 42a and the first lower arm switching element 42b.

[0021] 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.

[0022] The second reactor 47 is connected between a middle portion of the secondary coil 45b and the second node N2.

[0023] The current detector 48 a detects the supply current flowing through the laser diode 31 of the light-emitting circuit 30 .

[0024] The voltage detection unit 48b detects the voltage of the light emission circuit 30, that is, the voltage between the first and second nodes N1 and N2.

[0025] The first and second capacitors 49a, 49b are connected in series between the first and second nodes N1, N2. The connection point between the first and second capacitors 49a, 49b is grounded.

[0026] The control board 51 includes a control voltage generating circuit 53, a switching stop circuit 54, an error detection microcomputer 55, and a PWM control unit 56.

[0027] The control voltage generating circuit 53 generates a control voltage Vc based on the detection value Im of the current detecting unit 48a 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 small. In Fig. 2 and Fig. 3, the terminals and wiring marked with the symbols Im and Ic respectively have a voltage according to the detection value Im of the current detecting unit 48a and a voltage according to the command current Ic. The control voltage generating circuit 53 is configured as a hardware circuit.

[0028] 3, the control voltage generating circuit 53 includes a non-inverting amplifier circuit 531, a differential amplifier circuit 532, an integrating circuit 533, and an inverting amplifier circuit 534. The non-inverting amplifier circuit 531 and the differential amplifier circuit 532 configure a differential signal output circuit 535 that outputs a differential signal Vdif corresponding to the difference between the detection value Im of the current detecting unit 48a and a predetermined command current Ic. The integrating circuit 533 and the inverting amplifier circuit 534 configure a control voltage output circuit 536 that outputs a control voltage Vc based on the differential signal Vdif so that the absolute value of the difference between the detection value Im and the command current Ic becomes smaller.

[0029] The non-inverting amplifier circuit 531 amplifies the detection value Im of the current detector 48a. The non-inverting amplifier circuit 531 has a first operational amplifier 531a, and first and second resistors 531b and 531c.

[0030] A voltage according to the detection value Im is input to the non-inverting input terminal of the first operational amplifier 531a. One end of a first resistor 531b is connected to the inverting input terminal of the first operational amplifier 531a.

[0031] The other end of the first resistor 531b is grounded.

[0032] One end of the second resistor 531c is connected to the inverting input terminal of the first operational amplifier 531a, and the other end of the second resistor 531c is connected to the output terminal of the first operational amplifier 531a.

[0033] The differential amplifier circuit 532 outputs a differential signal Vdif obtained by amplifying the difference obtained by subtracting the output voltage of the non-inverting amplifier circuit 531 from the voltage according to the command current Ic. The differential signal Vdif is a signal according to the difference between the detection value Im and the command current Ic.

[0034] The differential amplifier circuit 532 includes a second operational amplifier 532a and third to sixth resistors 532b to 532e.

[0035] The inverting input terminal of the second operational amplifier 532a is connected to the output terminal of the first operational amplifier 531a via a third resistor 532b. A voltage according to the command current Ic is input to the non-inverting input terminal of the second operational amplifier 532a via a fourth resistor 532c. The output of the second operational amplifier 532a becomes the differential signal Vdif.

[0036] One end of the fifth resistor 532d is connected to the inverting input terminal of the second operational amplifier 532a, and the other end of the fifth resistor 532d is connected to the output terminal of the second operational amplifier 532a.

[0037] One end of the sixth resistor 532e is connected to the non-inverting input terminal of the second operational amplifier 532a, and the other end of the sixth resistor 532e is connected to the output terminal of the second operational amplifier 532a.

[0038] The integrating circuit 533 integrates the differential signal Vdif output by the differential amplifier circuit 532, and outputs the signal with the opposite polarity. The integrating circuit 533 has a third operational amplifier 533a, seventh and eighth resistors 533b and 533c, a third capacitor 533d, and a third diode 533e.

[0039] The differential signal Vdif is input to the inverting input terminal of the third operational amplifier 533a via the seventh resistor 533b. The non-inverting input terminal of the third operational amplifier 533a is grounded.

[0040] The eighth resistor 533c and the third capacitor 533d are connected in series with each other in this order from the inverting input terminal side between the inverting input terminal and the output terminal of the third operational amplifier 533a.

[0041] The third diode 533e is connected between the inverting input terminal and the output terminal of the third operational amplifier 533a with its cathode facing the inverting input terminal side. The third diode 533e is connected in parallel with the eighth resistor 533c and the third capacitor 533d.

[0042] The inverting amplifier circuit 534 inverts and amplifies the output of the integrating circuit 533, and outputs a control voltage Vc. The inverting amplifier circuit 534 has a fourth operational amplifier 534a, ninth and tenth resistors 534b and 534c, and a fourth diode 534d.

[0043] The inverting input terminal of the fourth operational amplifier 534a is connected to the output terminal of the third operational amplifier 533a via a ninth resistor 534b. The non-inverting input terminal of the fourth operational amplifier 534a is grounded.

[0044] The tenth resistor 534c is connected between the inverting input terminal and the output terminal of the fourth operational amplifier 534a.

[0045] The fourth diode 534d is connected between the inverting input terminal and the output terminal of the fourth operational amplifier 534a with its cathode facing the output terminal side. The fourth diode 534d is connected in parallel with the tenth resistor 534c.

[0046] The switching stop circuit 54 applies a predetermined voltage to the transmission path of the differential signal Vdif when the command current Ic is less than a predetermined threshold Ith. Specifically, the switching stop circuit 54 applies a negative voltage to the output terminal of the differential amplifier circuit 532. This causes the control voltage output circuit 536 to output a control voltage Vc of 0V that sets the duty ratio of the first AC voltage to 0. In FIG. 3, the terminals marked with the symbol Ith are each at a voltage corresponding to the current threshold Ith. The switching stop circuit 54 is configured of a hardware circuit.

[0047] In detail, the switching stop circuit 54 includes a phototransistor 541, an eleventh resistor 542, a light-emitting diode 543, a twelfth resistor 544, first to third bipolar transistors 545 to 547, a thirteenth resistor 548, a fourth bipolar transistor 549, and a comparator 550.

[0048] One end of the phototransistor 541 is connected to the output terminal of the differential amplifier circuit 532 via an eleventh resistor 542. A voltage of −15 V is applied to the other end of the phototransistor 541. The voltage applied to the other end of the phototransistor 541 is not limited to −15 V, but is set to a voltage value such that the control voltage Vc becomes 0 V when the phototransistor 541 is turned on.

[0049] The light-emitting diode 543 is disposed so as to be able to irradiate its light to the phototransistor 541. The anode of the light-emitting diode 543 is connected via a twelfth resistor 544 to a voltage source of 15 V.

[0050] The first bipolar transistor 545 is an NPN transistor. The collector of the first bipolar transistor 545 is connected to the cathode of the light emitting diode 543. The emitter of the first bipolar transistor 545 is grounded. A status signal St indicating the mode of the supply current is input to the base of the first bipolar transistor 545. This status signal St is at a high level in the standby state and at a low level in the output state. The user sets information indicating the mode of the supply current in the controller 20 by inputting it to an input device (not shown). The status signal St is generated based on the output of the controller 20 according to this setting.

[0051] The second bipolar transistor 546 is also an NPN transistor. The collector of the second bipolar transistor 546 is connected to the cathode of the light emitting diode 543. The emitter of the second bipolar transistor 546 is grounded. The base of the second bipolar transistor 546 is connected to the voltage source VCC via a thirteenth resistor 548.

[0052] The third bipolar transistor 547 is also an NPN transistor. The collector of the third bipolar transistor 547 is connected to the base of the second bipolar transistor 546. The emitter of the third bipolar transistor 547 is grounded. A laser setting signal Si indicating the type of laser is input to the base of the third bipolar transistor 547. The user sets in advance in the controller 20 by inputting information indicating whether or not to enable the function of the switching stop circuit 54, that is, the function of applying an applied voltage to the transmission path of the differential signal Vdif when the command current Ic is less than a predetermined threshold Ith, to an input device (not shown). The laser setting signal Si is generated based on the output of the controller 20 according to this setting. In this embodiment, the laser setting signal Si is set to a low level when the light emitting circuit 30 outputs a blue laser, and set to a high level when the light emitting circuit 30 outputs a near-infrared laser.

[0053] The fourth bipolar transistor 549 is also an NPN transistor. The collector of the fourth bipolar transistor 549 is connected to the base of the second bipolar transistor 546. The emitter of the fourth bipolar transistor 549 is grounded. The base of the fourth bipolar transistor 549 is connected to the output of the comparator 550. The trigger signal Tr output by the comparator 550 is input to the base of the fourth bipolar transistor 549.

[0054] The comparator 550 outputs a high-level trigger signal Tr when the command current Ic is equal to or greater than a predetermined threshold Ith, and outputs a low-level trigger signal Tr when the command current Ic is less than the predetermined threshold Ith.

[0055] When the error detection microcomputer 55 is in an output state and the trigger signal Tr is at a high level, the error detection microcomputer 55 judges whether or not there is an abnormality based on the detection value Im of the current detection unit 48a and the detection value Vm of the voltage detection unit 48b. When the error detection microcomputer 55 judges that there is an abnormality, the error detection microcomputer 55 causes the PWM control unit 56 to stop outputting a PWM signal, which will be described later. The error detection microcomputer 55 is a microcomputer. The detailed operation of the error detection microcomputer 55 will be described later.

[0056] The PWM control unit 56 generates a PWM signal having a duty ratio indicated by the control voltage Vc generated by the control voltage generation circuit 53. The PWM signal is a signal that indicates the on / off of the switching elements 42a to 42d. The control voltage Vc is a voltage that indicates the duty ratio of the first AC voltage, and corresponds to the duty ratio of the period during which the switching circuit 42 supplies a voltage to the isolation transformer 45.

[0057] The drive circuit 57 boosts the PWM signal generated by the PWM control unit 56 to a predetermined voltage level and outputs it to the switching elements 42a to 42d.

[0058] The PWM control unit 56 and the drive circuit 57 constitute a drive control unit 52 that controls the switching elements 42a to 42d of the switching circuit 42 based on the control voltage Vc.

[0059] The power supply 40 for a laser processing machine configured as described above can be applied to a light emitting circuit 30 using a blue laser diode that outputs a blue laser as the laser diode 31, and a light emitting circuit 30 using a red laser diode that outputs a near-infrared laser as the laser diode 31. Whether the laser diode 31 is a blue laser diode or a red laser diode, the supply current mode has a standby state and an output state. Whether the laser diode 31 is a blue laser diode or a red laser diode, in the standby state, the output of the PWM control unit 56 is controlled so that the supply current is 0 A. The control voltage Vc is controlled to be 0 V. When the laser diode 31 is a red laser diode, in the output state, the command current Ic is switched between a current value of a simmer current greater than 0 A and a current value of a first main current greater than the simmer current. When the laser diode 31 is a blue laser diode, in the output state, the command current Ic is switched between 0 A and a current value of a second main current greater than the simmer current.

[0060] When the laser diode 31 is a red laser diode and in the output state, the current value of the simmer current or the first main current is set as the command current Ic, the comparator 550 outputs a high-level trigger signal Tr. As a result, the fourth bipolar transistor 549 is turned on. In addition, since the laser setting signal Si is set to a high level, the third bipolar transistor 547 is also turned on. Therefore, the base voltage of the second bipolar transistor 546 is at a low level, and the second bipolar transistor 546 is turned off. In addition, since the state signal St is also set to a low level, the first bipolar transistor 545 is also turned off. Therefore, no current flows through the light-emitting diode 543, and the phototransistor 541 is turned off. In other words, the switching stop circuit 54 does not apply a negative voltage to the output terminal of the differential amplifier circuit 532.

[0061] Even when the laser diode 31 is a blue laser diode and is in an output state and the current value of the second main current is set as the command current Ic, the comparator 550 outputs a high-level trigger signal Tr. This causes the fourth bipolar transistor 549 to be in an on state. In addition, since the laser setting signal Si is set to a low level, the third bipolar transistor 547 is in an off state. Therefore, the base voltage of the second bipolar transistor 546 is at a low level, and the second bipolar transistor 546 is in an off state. In addition, since the state signal St is also set to a low level, the first bipolar transistor 545 is also in an off state. Therefore, no current flows through the light-emitting diode 543, and the phototransistor 541 is in an off state. In other words, the switching stop circuit 54 does not apply a negative voltage to the output terminal of the differential amplifier circuit 532.

[0062] When the laser diode 31 is a blue laser diode and 0A is set as the command current Ic in the output state, the comparator 550 outputs a low-level trigger signal Tr. As a result, the fourth bipolar transistor 549 is turned off. Also, since the laser setting signal Si is set to a low level, the third bipolar transistor 547 is also turned off. Therefore, the base voltage of the second bipolar transistor 546 is at a high level, and the second bipolar transistor 546 is turned on. Also, since the state signal St is set to a low level, the first bipolar transistor 545 is turned off. Therefore, a current flows through the light-emitting diode 543, and the phototransistor 541 is turned on. That is, the switching stop circuit 54 applies a negative applied voltage to the output terminal of the differential amplifier circuit 532. As a result, the control voltage Vc becomes 0V, that is, a voltage that sets the duty ratio of the first AC voltage to 0.

[0063] Furthermore, whether the laser diode 31 is a red laser diode or a blue laser diode, in the standby state, the state signal St is set to a high level, so that a current flows through the light emitting diode 543 and the phototransistor 541 is turned on. That is, the switching stop circuit 54 applies a negative voltage to the output terminal of the differential amplifier circuit 532. As a result, the control voltage Vc becomes 0V, that is, a voltage that sets the duty ratio of the first AC voltage to 0.

[0064] In the first embodiment, when the laser diode 31 is a blue laser diode, in the output state, if the command current Ic is switched from the current value of the second main current greater than 0A to 0A, the switching stop circuit 54 applies a negative applied voltage to the transmission path of the differential signal Vdif. This allows the control voltage Vc that sets the duty ratio to 0 to be output from the control voltage generation circuit 53 more quickly than when the switching stop circuit 54 is not provided. Therefore, it is possible to suppress oscillation of the supply current, quickly set the supply current to 0, and quickly switch the light emission circuit 30 from on to off. Since the light emission threshold of the blue laser diode is lower than that of the red laser diode, by enabling the function of the switching stop circuit 54 by the laser setting signal Si when the blue laser diode is used, it is possible to effectively suppress adverse effects such as blinking of the laser diode 31 caused by oscillation of the supply current.

[0065] 4 shows the operation of the error detection microcomputer 55. As shown in FIG. 4, when the error detection microcomputer 55 receives an output state transition command from the controller 20 to transition the supply current mode to an output state in state S1 in which the supply current mode is in the standby state, if the trigger signal Tr is at a high level, the error detection microcomputer 55 transitions to state S2. In state S2, the error detection microcomputer 55 compares the maximum value of the detection value Im of the current detection unit 48a in a predetermined time with a predetermined current threshold value, and compares the maximum value of the detection value Vm of the voltage detection unit 48b in a predetermined time with a predetermined voltage threshold value. If the maximum value of the detection value Im of the current detection unit 48a in a predetermined time is equal to or greater than the predetermined current threshold value, the maximum value of the detection value Vm of the voltage detection unit 48b in a predetermined time is equal to or greater than the predetermined voltage threshold value, and the trigger signal Tr is at a high level, the error detection microcomputer 55 repeats the comparison operation of the current value and the voltage value in state S2. When the maximum value of the detection value Im of the current detection unit 48a in a predetermined time is equal to or greater than a predetermined current threshold, the maximum value of the detection value Vm of the voltage detection unit 48b in a predetermined time is equal to or greater than a predetermined voltage threshold, and the trigger signal Tr is at a low level, the error detection microcomputer 55 transitions to state S3. In state S3, the error detection microcomputer 55 monitors the trigger signal Tr. While the trigger signal Tr is at a low level, the error detection microcomputer 55 maintains state S3. When the trigger signal Tr becomes a high level, the error detection microcomputer 55 transitions to state S2. In state S2, the error detection microcomputer 55 determines the presence or absence of an abnormality based on the detection value Im of the current detection unit 48a and the detection value Vm of the voltage detection unit 48b. When the maximum value of the detection value Im of the current detection unit 48a in a predetermined time is less than a predetermined current threshold, and the maximum value of the detection value Vm of the voltage detection unit 48b in a predetermined time is less than a predetermined voltage threshold, the error detection microcomputer 55 transitions to state S4. In state S4, the error detection microcomputer 55 determines that an abnormality has occurred in the switching circuit 42 (inverter circuit), and causes the PWM control unit 56 to stop outputting the PWM signal.In state S2, if the maximum value of the detection value Im of the current detection unit 48a in a predetermined time is less than a predetermined current threshold value and the maximum value of the detection value Vm of the voltage detection unit 48b in a predetermined time is equal to or greater than a predetermined voltage threshold value, the error detection microcomputer 55 transitions to state S5. In state S5, the error detection microcomputer 55 determines that there is an abnormality in the light-emitting circuit 30 (load) and causes the PWM control unit 56 to stop outputting the PWM signal. In state S2, if the maximum value of the detection value Im of the current detection unit 48a in a predetermined time is equal to or greater than a predetermined current threshold value and the maximum value of the detection value Vm of the voltage detection unit 48b in a predetermined time is less than a predetermined voltage threshold value, the error detection microcomputer 55 transitions to state S6. In state S6, the error detection microcomputer 55 determines that there is an abnormality in the output voltage and causes the PWM control unit 56 to stop outputting the PWM signal. By setting the cycle of judgment in state S2 and monitoring of the trigger signal Tr in state S3 to be short, it becomes possible to employ the error detection microcomputer 55 even when the laser is irradiated for a short period of time.

[0066] According to the first embodiment, even if the supply current mode is the output state, when the trigger signal Tr is at a low level, that is, when the command current Ic is less than a predetermined threshold Ith, the error detection microcomputer 55 does not determine whether or not there is an abnormality in the state S2. Therefore, when the laser diode 31 is a blue laser diode, it is possible to prevent the error detection microcomputer 55 from erroneously detecting an abnormality (error) due to the command current Ic being low.

[0067] Furthermore, in state S2, the error detection microcomputer 55 can identify the type of abnormality from three types based on the detection value Im of the current detection section 48a and the detection value Vm of the voltage detection section 48b, making it easier to analyze the cause of the abnormality.

[0068] Furthermore, when the laser diode 31 is a blue laser diode, the supply current can be switched between 0 A and the second main current by simply changing the command current Ic in the output state without causing the state of the error detection microcomputer 55 to transition between the standby state and the output state. Therefore, the time required to switch the supply current can be shortened.

[0069] (Embodiment 2) FIG. 5 is a diagram equivalent to FIG. 3 of the second embodiment. In the second embodiment, when the command current Ic is less than a predetermined threshold Ith, the switching stop circuit 54 applies a predetermined voltage to a transmission path of a control voltage Vc (signal) based on a difference signal Vdif in the control voltage output circuit 536. More specifically, the switching stop circuit 54 applies a voltage of about 0 V to the output terminal of the control voltage output circuit 536. As a specific configuration, the control voltage output circuit 536 further includes a fourteenth resistor 537. One end of the fourteenth resistor 537 is connected to the output terminal of the inverting amplifier circuit 534, and the voltage of the other end of the fourteenth resistor 537 becomes the control voltage Vc. The switching stop circuit 54 does not have an eleventh resistor 542, and one end of the phototransistor 541 is connected to the output terminal of the control voltage output circuit 536 (the other end of the fourteenth resistor 537). The other end of the phototransistor 541 is grounded.

[0070] 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.

[0071] In the second embodiment, the switching stop circuit 54 applies the applied voltage to the transmission path of the control voltage Vc, but the applied voltage may be applied to the transmission path of another signal based on the differential signal Vdif in the control voltage output circuit 536. For example, the switching stop circuit 54 may apply a predetermined applied voltage to the output terminal of the integrating circuit 533, thereby making the control voltage Vc 0 V.

[0072] In the first and second embodiments, the switching circuit 42 is provided with four switching elements 42a to 42d. However, the switching circuit 42 may have any number of switching elements other than four, as long as the number is one or more.

[0073] In the above-described first and second embodiments, the switching circuit 42 generates the first AC voltage. However, the switching circuit 42 may generate a continuous pulse voltage, the DC current generating circuit 44 may use a continuous pulse signal to cause a DC supply current to flow to the light-emitting circuit 30, and the control voltage Vc may indicate the duty ratio of the continuous pulse signal.

[0074] In addition, in the above embodiments 1 and 2, the error detection microcontroller 55 determines whether or not there is an abnormality based on both the detection value Im of the current detection unit 48a and the detection value Vm of the voltage detection unit 48b, but it may also determine whether or not there is an abnormality based on either one of the detection values. [Industrial Applicability]

[0075] The power supply for a laser processing machine and the direct diode laser device equipped with the same disclosed herein are useful as a power supply for a laser processing machine that can quickly switch the light-emitting circuit from on to off and that passes current through a light-emitting circuit for laser processing having at least one laser diode, and as a direct diode laser device equipped with the same. [Explanation of symbols]

[0076] 10 Laser Head 30 Light emitting circuit 31 Laser Diode 40 Power supply for laser processing machine 42 Switching Circuits 42a~42d Switching elements 44 DC current generation circuit 48a Current detection section 48b Voltage detection section 52 Drive control unit 535 Differential signal output circuit 536 Control voltage output circuit 54 Switching stop circuit 55 Error detection microcomputer Ic command current Ith threshold Im detection value Vm detection value Vc Control voltage Vdif Differential voltage 90 Optical Fiber 100 Direct Diode Laser Device LB laser light

Claims

1. A power supply for a laser processing machine that supplies 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 indicating a duty ratio of the first AC voltage or the continuous pulse voltage; a differential signal output circuit that outputs a differential signal corresponding to a difference between a detection value of the current detection unit and a predetermined command current; a control voltage output circuit that outputs the control voltage based on the difference signal so that an absolute value of a difference between the detection value and the command current becomes small; a switching stop circuit that applies a predetermined voltage to a transmission path of the differential signal or to a transmission path of a signal based on the differential signal in the control voltage output circuit when the command current is less than a predetermined threshold, thereby causing the control voltage output circuit to output a control voltage that sets the duty ratio to zero.

2. 2. The power supply for a laser processing machine according to claim 1, A voltage detection unit that detects a voltage of the light emission circuit; a microcomputer that determines whether or not there is an abnormality based on at least one of a detection value of the current detection unit and a detection value of the voltage detection unit, 2. The power supply for a laser processing machine, wherein the microcomputer does not determine the presence or absence of an abnormality when the command current is less than a predetermined threshold value.

3. 2. The power supply for a laser processing machine according to claim 1, 4. The power supply for a laser processing machine, wherein the switching stop circuit applies the predetermined voltage to a transmission path of the differential signal.

4. 2. The power supply for a laser processing machine according to claim 1, 4. The power supply for a laser processing machine, wherein the switching stop circuit applies the predetermined applied voltage to an output terminal of the control voltage output circuit.

5. A power supply for a laser processing machine according to any one of claims 1 to 4; The light emitting circuit; an optical fiber through which the laser light emitted by the light emitting circuit passes; a head that emits a laser beam that has passed through the optical fiber; 13. A direct diode laser device, wherein the laser diode of the light emitting circuit is a blue laser diode.

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