JP5972603B2 - Laser power supply device and control method thereof - Google Patents

Description

  The present invention relates to a laser power supply apparatus having an improved simmer circuit for simmering a lamp.

  Conventionally, a circuit shown in FIG. 6 has been used as a laser power supply device 1 for a solid-state laser represented by a YAG laser. This power supply device includes a main circuit 2 for supplying a main circuit current to a lamp 6 that emits laser light, a simmer circuit 3 for supplying a simmer current for simmering the lamp 6, and a high-voltage generating circuit 4 for increasing the simmer current. The trigger circuit 5 for starting the simmer discharge is included.

  The main circuit 2 is connected to an AC power supply via contactors 8a to 8c. Reactors 10a to 10c are connected to the main circuit 2 side of the contactors 8a to 8c, and a converter bridge 11 and a capacitor 21 are provided at the ends thereof. The voltage boosted and DC converted by the converter bridge 11 is charged in the capacitor 21. FIG. 6 shows a case of a three-phase AC power supply, and current detectors 9a and 9b are provided for the two phases to which the reactors 10a and 10c are connected.

  The main circuit 2 is provided with a resistor 22 and a switch 8d for discharging the capacitor 21. By closing the switch 8d, the electric charge stored in the capacitor 21 is discharged through the resistor 22. The main circuit current is generated by a step-down chopper circuit composed of the switching element 24, the diode 28 and the reactor 25, and is supplied to the lamp 6 through the back pressure prevention diode 27. The switching element 24 is subjected to switching control at high speed by the control circuit 23. The control circuit 23 is configured to feed back the current value detected by the current detector 26.

  On the other hand, the laser power supply device 1 is provided with a shimmer circuit 3 in addition to the main circuit 2. The simmer circuit 3 is a circuit for simmering the lamp 6. The shimmer circuit 3 has a step-down chopper circuit including a switching element 31, a diode 34, and a reactor 35 via a fuse 38 from the positive electrode of the capacitor 21. This chopper circuit is connected to the lamp 6 via a current detector 36 and a diode 37. The simmer circuit 3 is provided with a control circuit 32. The control circuit 32 controls the switching element 31 so as to control the simmer current constant. The control circuit 32 is configured to feed back the current value detected by the current detector 36.

  In order to pass the simmer current, it is necessary to first apply a high voltage of 1500 to 2000 V to the lamp 6. The high voltage generation circuit 4 is a circuit for this purpose. The high voltage generation circuit 4 boosts the AC power source by the transformer 44, converts it to DC by the diode 43, and stores it in the capacitor 41. The resistor 42 is inserted for the purpose of controlling the current of the diode 43.

  The simmer current flows out from the state in which a high voltage of 1500 to 2000 V is applied to the lamp 6 by causing the trigger circuit 5 to discharge at a higher voltage. When a simmer current of 1 to 2 A flows, the voltage of the lamp 6 decreases to about 100 V and the current continues. In this state, laser light is emitted by flowing a main current of 400 to 500 A (voltage of 400 to 500 V).

JP 2003-78191 A

The characteristics of the simmer circuit 3 shown in FIG. 6 are as follows.
(1) Control of a minute current of about 1 to 2A.
(2) Step-down chopper control from the high-voltage DC 700-750V class to the 100V class.
(3) As shown in FIG. 2, the load characteristic of the lamp 6 is widely used in output power control because it exhibits a negative resistance characteristic in which the load voltage decreases as the current increases in the simmer current range. Triangle wave comparison PWM cannot be used.

  For the reason described in (3) above, so-called delta modulation (described later) is generally used as a method for controlling the switching element 31 in the simmer circuit 3 shown in FIG. This method has the disadvantage that the switching frequency changes over a wide range, and the switching loss of the switching element 31 and the high-speed diode 34 increases, and the reliability of these elements decreases.

  In this current class step-down chopper circuit, the circuit components are generally arranged on a printed circuit board. Therefore, the fuse 38 is generally inserted in series with the power supply line for the purpose of preventing the printed circuit board from burning due to an abnormal current generated due to a short circuit failure of the semiconductor element.

  However, the shimmer circuit 3 has a configuration in which the switching element 31, the diode 37, and the lamp 6 are connected, so that the input impedance is as high as several ohms, and it takes time for sufficient current to flow to blow the fuse 38. . Therefore, in such a shimmer circuit 3, there is a problem that the probability that the printed circuit board is burned out is extremely high when the switching element or the like is short-circuited.

  The present invention has been proposed to solve the above-described problems, and improves the reliability by suppressing the switching loss of the semiconductor element, and the printed circuit board is burned even if the semiconductor element breaks down. It is an object of the present invention to provide a reliable and reliable laser power supply apparatus and a control method therefor.

  In order to achieve the above object, a laser power supply apparatus according to the present embodiment includes a main circuit that receives power from a power supply and supplies power for laser output to a lamp, and a simmer current for simmering the lamp. A simmer circuit that generates and supplies the simmer to the lamp, wherein the main circuit is severably connected to the power source, and the simmer circuit is a control circuit for maintaining the simmer current A switching element controlled by the power supply, and a power supply side of the switching element having an abnormality detection unit that detects that the simmer current is abnormal and outputs an abnormality signal, and the abnormality signal is input A shutoff instruction unit for shutting off the main circuit and the power supply is provided.

  The abnormality detection unit includes a resistor connected to the power supply side of the switching element, detects that the current flowing through the resistor exceeds a predetermined current value, and outputs an abnormality signal. May be.

  Further, in the laser power supply device of the present embodiment, the control circuit includes a pulse output unit that outputs a pulse having a constant period, and a peak current detection unit that outputs a detection signal when the value of the simmer current reaches a set value. A frequency fixing unit configured to input the pulse and the detection signal, turn the output on when the pulse rises or falls, and turn the output off when the peak detection signal is input You may have.

Further, the shut-off instruction unit may be connected to the abnormality detection unit by an insulating element so as to be communicable, and the abnormality signal may be input via the insulating element.
An abnormality signal may be output by detecting that the temperature of the resistor exceeds a predetermined temperature. Further, the simmer circuit is configured to insert a filter capacitor between the connection point of the switching element and the resistor and the power line on the negative side of the lamp so as to suppress a ripple of current flowing through the resistor. May be.

  Note that this embodiment can also be understood as a method for controlling a laser power supply apparatus that realizes the above functions.

It is a circuit diagram which shows the laser power supply device which concerns on 1st embodiment. It is a figure which shows the load characteristic of the lamp | ramp 6. FIG. It is a figure which shows the output relationship of a simmer current and a switching element. It is a circuit diagram which shows the control circuit which concerns on 2nd embodiment. It is a circuit diagram which shows the abnormality detection part which concerns on 3rd embodiment. It is a circuit diagram which shows the laser power supply device which uses the conventional simmer circuit.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.
[First embodiment]
(1. Overall configuration)
As shown in FIG. 1, the laser power source apparatus 1 according to the first embodiment includes a main circuit 2 for supplying a main circuit current to a lamp 6 that emits laser light, and a simmer for supplying a simmer current for simmering the lamp 6. The circuit 3 includes a high voltage generating circuit 4 for increasing the simmer current and a trigger circuit 5 for starting simmer discharge.

(2. Main circuit)
The main circuit 2 is connected to a three-phase AC power source via contactors 8a, 8b, and 8c. Reactors 10a, 10b, and 10c are connected to the main circuit 2 side of each of the contactors 8a, 8b, and 8c, and are connected to the converter bridge 11 at the end thereof. That is, the reactor 10 and the converter bridge 11 constitute a non-insulated boost converter circuit. The voltage boosted and DC converted by the converter bridge 11 is charged in the capacitor 21.

  For each phase to which reactors 10a and 10c are connected, current detectors 9a and 9b are provided. The switching element of the converter bridge 11 is controlled based on the current value detected by the current detectors 9a and 9b.

  The resistor 22 is provided to discharge the capacitor 21. When the switch 8d inserted in series is closed, a current flows to discharge the capacitor 21. In the present embodiment, the switch 8d opens and closes in conjunction with the contactor 8. That is, when the contactor 8 is closed and the power supply is connected to the main circuit 2, the switch 8d is opened and the capacitor 21 is in a chargeable state. Conversely, the contactor 8 is opened and the main circuit 2 and the power supply are connected. When the connection is interrupted, the switch 8d is closed, and the charge stored in the capacitor 21 is discharged.

A main circuit current for discharging the lamp 6 is generated by a step-down chopper circuit composed of a switching element 24, a diode 28 and a reactor 25, and is supplied to the lamp 6 through a back pressure prevention diode 27. The switching element 24 is controlled at high speed by the control circuit 23. The control circuit 23 is configured to feed back the current value detected by the current detector 26.
(3. Shimmer circuit)

  In addition to the main circuit 2, the laser power supply device 1 is provided with a simmer circuit 3 that generates a simmer discharge in the lamp 6. The simmer discharge is performed for preionizing the inside of the lamp. The shimmer circuit 3 branches from the positive electrode side of the capacitor 21 and is connected to the switching element 31 via a resistor 71. A connection point between the resistor 71 and the switching element 31 is connected to the negative electrode side of the lamp 6 via the capacitor 33. The resistor 71 limits the current flowing from the main circuit 2 to i71 and constitutes a filter circuit in relation to the capacitor 33.

  As shown in FIG. 1, a photocoupler 74 is connected from the positive side of the resistor 71 via a Zener diode 72 and a resistor 73, and the photocoupler 74 is connected to the negative side of the resistor 71. That is, a circuit in which the Zener diode 72, the resistor 73, and the photocoupler 74 are connected in series is provided in parallel with the resistor 71. In the present embodiment, the circuit including the resistor 71, the Zener diode 72, the resistor 73, and the photocoupler 74 constitutes the abnormality detection unit 7.

  The photocoupler 74 is connected to the cutoff instruction unit 12. This shut-off instruction unit 12 outputs a signal for shutting off the power source and the main circuit 2. Specifically, it is connected to the contactor coil 13 for turning on or off the contactor 8 connecting the power source and the main circuit 2. The photocoupler 74 has a light emitting element and a light receiving element therein, and is an insulating element capable of transmitting a signal while maintaining insulation therebetween. In this embodiment, the photocoupler 74 is disposed so as to insulate the abnormal current detection unit 7 and the cutoff instruction unit 12 from each other.

  In the present embodiment, the photocoupler 74 is used for the abnormal current detector 7, but the configuration is not limited to such a configuration. Any configuration that can transmit a signal while maintaining insulation between the abnormal current detection unit 7 and the cutoff instruction unit 12 may be used. For example, other insulating elements such as an electromagnetic relay may be used.

  A step-down chopper circuit including a diode 34 and a reactor 35 is configured on the lamp 6 side of the switching element 31, and is connected to the lamp 6 via a current detector 36 and a diode 37 therefrom. That is, the current i 36 flowing through the current detector 36 is a simmer current for maintaining the simmer discharge of the lamp 6. The control circuit 32 controls the switching element 31 so as to control the current i36 to be constant. The control circuit 32 is configured to feed back the value of the current i 36 detected by the current detector 36.

(4. High voltage generation circuit, trigger circuit)
In order to pass a simmer current, it is necessary to first apply a high voltage of 1500 V to 2000 V to the lamp 6. The circuit for this purpose is the high voltage generation circuit 4, and the high voltage generation circuit 4 boosts the AC power source by the transformer 44, converts it to DC by the diode 43 and stores it in the capacitor 41. The resistor 42 is inserted for the purpose of controlling the current of the diode 43.

  The simmer current flows from the state in which a high voltage of 1500 V to 2000 V is applied to the lamp 6 by discharging it with a higher voltage by the trigger circuit 5. When a simmer current of 1 to 2 A flows, the voltage of the lamp 6 decreases to about 100 V and the current continues. In this state, a laser beam is emitted by applying a main current of 400 to 500 A (voltage of 400 V to 500 V).

(5. Effects)
As shown in FIG. 3, the simmer current i <b> 36 generates a triangular ripple as the switching element 31 is switched. The capacitor 33 is designed to suppress the fluctuation of the current i71 due to this ripple. For example, the ripple of the current i71 can be extremely reduced by using a capacitor 33 having a relatively large capacity of about 1 μF.

Here, the loss of the current i71 and the resistor 71 can be obtained as follows.
As shown in FIG. 2, the lamp voltage V1 when a simmer current is passed is about 100V. Assuming that the simmer current i36 is 2A, the current i71 flowing through the resistor 71 is expressed as follows.
(Formula 1) i71 × 750V = i36 × 100V
If i36 = 2A, i71 can be obtained by the following equation.
(Formula 2) i71 = (2A × 100V) /750V=0.27A
Therefore, assuming that the resistance 71 is 120Ω, the loss of the resistance 71 during the simmer discharge is as follows.
(Formula 3) 120 × 0.27 × 0.27 = 8.7 W

  The current when the switching element is short-circuited is 750/120 = 6.25 A, and the resistance loss is 750 × 6.25 A = 4687 W.

  Since the short-time withstand capability of the resistor is 20 times or more than the rated capacity, 4687/20 = 234 W, and it can be seen that the short-time withstand capability of the resistor 71 can withstand about 250 W.

  Next, the operation of the present embodiment when the switching element 31 is short-circuited due to deterioration or the like will be described.

  The Zener diode 72 of the abnormality detection unit 7 is configured such that current flows when the voltage across the resistor 71 exceeds a predetermined voltage value. This voltage value can be arbitrarily designed by changing constants such as the breakdown voltage of the Zener diode 72, the resistance value of the resistor 73, and the resistance value when the photocoupler 74 is turned on. When a current flows through the Zener diode 72, the current is limited by the resistor 73, and then an abnormal current generation signal is transmitted to the cutoff instruction unit 12 by the photocoupler 74.

  Upon receiving the abnormal current generation signal, the shutoff instruction unit 12 quickly turns off the power supply of the operating coil 13 of the contactor 8 to shut off the connection between the main circuit 2 and the three-phase AC power supply. In this embodiment, since the switch 8d operates in conjunction with the contactor 8, the switch 8d is closed at the same time when the contactor 8 is turned off, and the electric charge stored in the capacitor 21 is quickly discharged through the resistor 22. Is done.

  With the above operation, even when the switching element or the like is short-circuited and the current of the simmer circuit 3 becomes abnormal, it does not take time as the fuse is blown. That is, since the AC power supply and the main circuit 2 can be immediately interrupted and the capacitor 21 can be discharged in response to the occurrence of an abnormal current, the printed circuit board can be prevented from being burned by the abnormal current, and the reliability of the laser power supply device can be prevented. Improve sexiness.

  Since the shutoff instruction unit 12 is insulated from the abnormality detection unit 7, an overvoltage or overcurrent is not applied from the main circuit 2 or the simmer circuit 3 to cause a failure. Further, since the shut-off instruction unit 12 can use low-voltage components, it can be configured at low cost. Therefore, it is possible to realize a highly reliable laser power supply apparatus without cost.

[Second Embodiment]
Next, a second embodiment will be described in detail with reference to FIGS. The second embodiment is characterized in that a fixed frequency switching system is employed in the control circuit 32 of the simmer circuit 3. The configuration other than the control circuit 32 is the same as that of the first embodiment.

(Constitution)
As shown in FIG. 4, the control circuit 32 of the second embodiment is configured as follows. That is, the pulse output unit 14 that outputs a pulse of a constant frequency, the peak current detection unit 15 that outputs a signal when the value of the simmer current i 36 detected by the current detector 36 exceeds a set value, the pulse output unit 14, The flip-flop 16 is configured to receive a signal from the peak current detector 15 and control the drive circuit 17. A switching element 31 is connected to the tip of the drive circuit 17 via a resistor 18.

(Function and effect)
First, a control method used for step-down chopper control of the laser power supply device will be described. As shown in FIG. 2, the load characteristic of the lamp 6 exhibits a negative resistance characteristic in the range of the simmer discharge. The negative resistance characteristic is a characteristic that the load voltage decreases as the current increases. In the case of such a negative resistance characteristic, the triangular wave comparison method generally used in output voltage control cannot be used. Therefore, as a method for controlling the simmer current i36, so-called delta modulation in which the PWM output level is constant during a current change is generally used.

  The feature of the control system using delta modulation is that the circuit is simple and the operation is stable. However, on the other hand, there are disadvantages that the switching frequency is greatly changed depending on the load condition and the noise of the reactor is increased, and the loss of the switching element is significantly changed, so that it is difficult to ensure the reliability of the semiconductor element.

  In the present embodiment, the flip-flop 16 is set in response to the rise or fall of the pulse signal input from the pulse output unit 14. That is, the output of the flip-flop 16 is turned on. This ON state refers to a state in which a current flows through the switching element 31. Therefore, in this state, the simmer current i36 increases.

  Next, when the value of the simmer current i 36 reaches the value set by the peak detector 15, the peak detector 15 outputs a reset signal to the flip-flop 16. In response to this signal, the output of the pulse signal of the flip-flop 16 is turned off. As a result, the switching element 31 is opened, and the simmer current i36 is decreased.

  By repeatedly performing the above operation, the control circuit 32 of the present embodiment performs switching control of the switching element 31 at a fixed frequency, thereby maintaining the simmer current i36 at a constant peak value while maintaining the minimum value voltage variable. .

By adopting such a configuration of the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment. That is, although it is a control method of delta modulation, the switching frequency which is the drawback does not change greatly. Therefore, the loss of the switching element 31 can be made almost constant, the temperature rise of the switching element 31 becomes stable, and a more reliable laser power supply apparatus can be realized.
[Third embodiment]
Next, a third embodiment will be described in detail with reference to FIGS. 1 and 5. The third embodiment is characterized in that a temperature sensor is employed in the abnormality detection unit 7 of the simmer circuit 3. The configuration other than the abnormality detection unit 7 is the same as that of the first embodiment.

(Constitution)
As shown in FIG. 5, the abnormality detection unit 7 of the third embodiment is configured by attaching a temperature detection unit 19 to a resistor 71. The output of the temperature detection unit 19 is connected to the cutoff instruction unit 12. The temperature detection unit 19 detects that the current i 71 flowing through the resistor 71 has reached an abnormal current value from the temperature rise of the resistor 71 and notifies the cutoff instruction unit 12.

(Function and effect)
By adopting the configuration of the third embodiment as described above, even when the switching element or the like is short-circuited and the current of the simmer circuit 3 becomes abnormal, it takes time to blow the fuse. Absent. That is, the occurrence of the abnormal current is immediately detected by the temperature detection unit 19 and notified to the shut-off instruction unit 12, so that the printed circuit board can be prevented from being burned by the abnormal current, and the reliability of the laser power supply device To improve.

[Other Embodiments]
In the present specification, a plurality of embodiments according to the present invention have been described. However, these embodiments are presented as examples, and are not intended to limit the scope of the invention. Specifically, a combination of all or any of the embodiments is also included. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

DESCRIPTION OF SYMBOLS 1 Laser power supply device 2 Main circuit 21 Capacitor 22 Resistance 23 Control circuit 24 Switching element 25 Reactor 26, 36, 9a, 9b Current detector 27, 28 Diode 3 Shimmer circuit 31 Switching element 32 Control circuit 33 Capacitor 34, 37 Diode 35 Reactor 38 Fuse 4 High voltage generation circuit 41 Capacitor 42 Resistance 43 Diode 44 Transformer 5 Trigger circuit 6 Lamp 7 Abnormality detection unit 71, 73 Resistance 72 Zener diode 74 Photocoupler 8a, 8b, 8c Contactor 8d Switch 10a, 10b, 10c Reactor 11 Converter bridge 12 shut-off instruction unit 13 contactor coil 14 pulse output unit 15 peak current detection unit 16 flip-flop 17 drive circuit 18 resistor 19 temperature detection unit

Claims (8)

A main circuit that receives power from a power source and supplies power to the lamp for laser output;
A simmer circuit for generating a simmer current for simmer discharge of the lamp and supplying the simmer current;
A laser power supply device comprising:
The main circuit is connected to the power source so as to be cut off,
The shimmer circuit is
A switching element controlled by a control circuit to maintain the simmer current;
On the power supply side of the switching element, there is an abnormality detection unit that detects that the simmer current is abnormal and outputs an abnormal signal,
A shut-off instruction unit that shuts off the main circuit and the power supply when the abnormal signal is input;
A laser power supply device. The abnormality detection unit
Comprising a resistor connected to the power supply side of the switching element;
Detecting that the current flowing through the resistor exceeds a predetermined current value, and outputting the abnormal signal;
The laser power supply device according to claim 1. The control circuit includes:
A pulse output unit that outputs pulses with a constant period;
A peak current detector that outputs a detection signal when the value of the simmer current reaches a set value;
Having a frequency fixing unit configured to input the pulse and the detection signal, turn the output on when the pulse rises or falls, and turn the output off when the detection signal is input;
The laser power supply device according to claim 1, wherein: The blocking instruction unit
It is connected to an insulating element capable of communicating while maintaining insulation with the abnormality detection unit ,
The abnormal signal is input to the shutoff instruction unit via the insulating element;
The laser power supply device according to claim 1, wherein: The abnormality detection unit
Detecting that the temperature of the resistor exceeds a predetermined temperature, and outputting an abnormal signal;
The laser power supply device according to claim 1, wherein: The shimmer circuit is
Inserting a filter capacitor between the connection point of the switching element and the resistor, and the power line on the negative side of the lamp,
The laser power supply device according to claim 1, wherein the laser power supply device is configured to suppress a ripple of a current flowing through the resistor. A main circuit that receives power from a power source and supplies power to the lamp for laser output;
A simmer circuit for generating a simmer current for simmer discharge of the lamp and supplying the simmer current to the lamp;
Detecting that the simmer current in the simmer circuit is abnormal and outputting an abnormal signal;
A process of shutting off the main circuit and the power supply when the abnormal signal is input;
A control method of a laser power supply device characterized by the above. The simmer circuit includes a switching element for controlling the simmer current,
The process of controlling the switching element is:
Pulse output processing that outputs pulses with a constant period;
A peak current detection process for outputting a detection signal when the value of the simmer current reaches a set value;
A frequency fixing process in which the pulse and the detection signal are input, the output is turned on when the pulse rises or falls, and the output is turned off when the peak detection signal is input;
The method of controlling a laser power supply device according to claim 7.

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