JP2017184372A - Laser driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser driver capable of stabilizing output energy.SOLUTION: A high-frequency power supply 106 is configured so that an input is connected with a bank capacitor 104 and to intermittently supply an alternating voltage Vto a laser light source 2. A charging power supply 102 charges the bank capacitor 104 to a target voltage Vduring a stopping period of the high-frequency power supply 106.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a laser driving device.

Laser processing apparatuses are widely used as industrial processing tools. FIG. 1 is a block diagram of the laser processing apparatus 1r. The laser processing device 1r includes a laser light source 2 such as a CO ₂ laser, and a laser driving device 4r that supplies AC power to the laser light source 2 to excite it. The laser driving device 4 r includes a direct current power source 6 and a high frequency power source 8. The DC power supply 6 stabilizes the output DC voltage _VDC at a target value by feedback control using PID (Proportional-Integral-Differential) control or PI control. The high frequency power supply 8 receives the direct current voltage _VDC , converts it into an alternating voltage, and supplies it to the laser light source 2 that is a load.

In the laser processing apparatus 100r for drilling, the laser light source 2 operates discontinuously. That is, a relatively short light emission period of several microseconds to 10 microseconds and a pause period that is the same, short, or long are alternately repeated. In order to stabilize the output energy of the laser light source 2, the DC voltage _VDC must be within a predetermined allowable fluctuation range.

Japanese Patent Laying-Open No. 2015-100029

  FIG. 2 is an operation waveform diagram of the laser processing apparatus 1r of FIG. The vertical and horizontal axes of the waveform diagrams and time charts referred to in this specification are enlarged or reduced as appropriate for easy understanding, and each waveform shown is also simplified for easy understanding. Or exaggerated or emphasized.

The high frequency power supply 8 repeats an operation period and a rest period in accordance with the turning on and off of the laser light source 2. When the high-frequency power supply 8 shifts from the rest period to the operation period, a feedback response delay occurs in the direct-current power supply 6, and the direct-current voltage _VDC may decrease and deviate from the allowable variation range. When the operation period of the high-frequency power supply 8 shifts from the operation period to the idle period, the direct-current voltage _VDC increases due to a feedback delay, and may deviate from the allowable variation range.

In addition, when switching to a different processing, the target value of the DC voltage _VDC may be switched. Again, if the response speed of the DC power supply 6 is slow, the transition time until the DC voltage _VDC reaches the next target value becomes long. During the transition time, the laser light source 2 cannot emit light, which causes a reduction in operating rate.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and one of exemplary purposes of an embodiment thereof is to provide a laser driving device capable of stabilizing output energy.

  One embodiment of the present invention relates to a laser driving device. The laser driving device includes a bank capacitor, a high-frequency power source that has an input connected to the bank capacitor and intermittently supplies an alternating voltage to the laser light source, a charging circuit that charges the bank capacitor to a target voltage during a pause period of the high-frequency power source, Is provided.

  In this aspect, the bank capacitor behaves as a power source for supplying power to the high frequency power source. During the charging period of the bank capacitor by the charging power source, the high frequency power source is stopped, so that the charging power source is substantially in a no-load state. Therefore, the voltage of the bank capacitor can be charged to the target voltage stably in a short time as compared with the conventional DC power supply that needs to stabilize the voltage during load fluctuation, and the output energy can be stabilized.

  The charging power supply may include a first boost converter.

  The first boost converter may operate in a discontinuous mode. In this case, the amount of charge supplied to the bank capacitor by one switching can be accurately controlled according to the on-time, reactor inductance, and converter input voltage, and the bank capacitor voltage can be accurately controlled. It becomes.

  The charging power supply may further include a second boost converter in which the inductance of the reactor is smaller than the first boost converter. As a result, the first boost converter can quickly charge the bank capacitor with coarse accuracy, and the second boost converter can accurately charge the bank capacitor with high accuracy, and the voltage of the bank capacitor can be made closer to the target voltage. It becomes.

  The bank capacitor charging operation by the first boost converter may be followed by the bank capacitor charging operation by the second boost converter.

  The first boost converter may be a diode rectification type, and the second boost converter may be a synchronous rectification type. The second boost converter can be charged and discharged, and the bank capacitor voltage can be adjusted more precisely.

  The charging power source may obtain the ON time of the first boost converter by numerical calculation. From the difference between the voltage of the bank capacitor before the start of charging and the target voltage, the amount of charge to be supplied to the bank capacitor can be calculated, and further the on-time can be calculated. This eliminates the need for PI control or PID control and reduces response delay.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to an aspect of the present invention, output energy can be stabilized.

It is a block diagram of a laser processing apparatus. It is an operation | movement waveform diagram of the laser processing apparatus of FIG. It is a block diagram of the laser processing apparatus which concerns on embodiment. It is an operation | movement waveform diagram of the laser processing apparatus of FIG. It is a block diagram which shows the structural example of the charging power supply of FIG. It is an operation | movement waveform diagram of a 1st step-up converter. It is an operation | movement waveform diagram of the charging power supply of FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

FIG. 3 is a block diagram of the laser processing apparatus 1 according to the embodiment. The laser processing apparatus 1 includes a laser light source 2 and a laser driving device 100. The laser light source 2 is, for example, a CO ₂ laser. The laser driving device 100 supplies AC power to the laser light source 2 to excite it.

The laser driving apparatus 100 includes a charging power source 102, a bank capacitor 104, and a high frequency power source 106. The high frequency power supply 106 has an input 108 connected to the bank capacitor 104 and an output connected to the laser light source 2. The high-frequency power source 106 receives the DC voltage _VDC generated in the bank capacitor 104 and intermittently supplies an alternating voltage (drive voltage) V _DRV to the laser light source 2. That is, the high frequency power supply 106 performs a switching operation during the light emission period of the laser light source 2, and the switching of the high frequency power supply 106 is stopped during the light extinction period of the laser light source 2. A period during which the high-frequency power source 106 is switched is referred to as an operation period, and a period during which the switching is stopped is referred to as a pause period. The configuration of the high-frequency power source 106 is not particularly limited, and a known technique may be used.

The bank capacitor 104 can be grasped as a direct current power source such as an electric storage device that supplies power to the high frequency power source 106 by itself. The charging power source 102 charges the bank capacitor 104 to the target voltage V _REF during the pause period of the high frequency power source 106. During the operation period of the high-frequency power source 106, the charging of the bank capacitor 104 is stopped, so that the voltage _VDC of the bank capacitor 104 decreases due to discharge by the high-frequency power source 106. Therefore, the capacity of the bank capacitor 104 is designed so that the DC voltage _VDC does not fall below the allowable range even in the process of discharge by the high-frequency power source 106.

The above is the configuration of the laser processing apparatus 1. Next, the operation will be described. FIG. 4 is an operation waveform diagram of the laser processing apparatus 1 of FIG. The high frequency power supply 106 operates intermittently at a repetition frequency of about 5 kHz and a duty ratio of about 5%. During the operation period of the high frequency power source 106, the bank capacitor 104 behaves as a power source for supplying power to the high frequency power source 106. During this time, the charging power supply 102 is stopped, and the DC voltage _VDC of the bank capacitor 104 is lowered by discharging. However, since the capacity of the bank capacitor 104 is sufficiently large, the direct voltage _VDC does not fall below the allowable voltage range.

When the operation of the high-frequency power supply 106 is stopped and the suspension period starts, the charging of the bank capacitor 104 by the charging power supply 102 starts, and the bank capacitor 104 is charged to the target voltage _VREF . The laser processing apparatus 1 repeats this operation.

The above is the operation of the laser processing apparatus 1. Next, the advantages will be described.
In the laser processing apparatus 1r of FIG. 1, the DC power supply 6 is always operating, and therefore the load fluctuates greatly during the operation, which causes the fluctuation of the output voltage _VDC . In contrast, in the laser processing apparatus 1 of FIG. 3, the high-frequency power source 106 is stopped during the charging period of the bank capacitor 104 by the charging power source 102, and the charging power source 102 is substantially in a no-load state. That is, the bank capacitor 104 is charged in a static state where no load fluctuation occurs. Therefore, the voltage V _DC of the bank capacitor 104 can be charged to the target voltage V _REF stably in a short time as compared with the DC power supply 6 of FIG. 1 that needs to stabilize the voltage during the load fluctuation. Output energy can be stabilized.

  The present invention is understood as the block diagram and circuit diagram of FIG. 3 or extends to various devices and circuits derived from the above description, and is not limited to a specific configuration. In the following, more specific configuration examples and examples will be described in order not to narrow the scope of the present invention but to help understanding and clarify the essence and circuit operation of the present invention.

FIG. 5 is a block diagram illustrating a configuration example of the charging power source 102 of FIG. The charging power source 102 includes a rectifying / smoothing circuit 110, a first boost converter 112, and a second boost converter 114. Rectifier smoothing circuit 110 receives a commercial AC voltage _{V AC,} rectifies it, and smoothed to produce a DC voltage _{V IN.} For example the commercial AC voltage _{V AC} is a three-phase 220V, DC voltage _{V IN} is 300 V.

The target voltage V _REF of the voltage V _DC of the bank capacitor 104 is, for example, 500V. The first boost converter 112 receives the DC voltage _VIN and supplies a charging current I _CHG1 to the bank capacitor 104. The first boost converter 112 charges the bank capacitor 104 rapidly. The first boost converter 112 is a diode rectification type including a reactor L1, a switching transistor M1, and a rectifier diode D1. The charging current I _CHG1 generated by the first boost converter 112 flows only in the direction in which the bank capacitor 104 is charged.

The second boost converter 114 is provided to accurately charge the bank capacitor 104 with higher accuracy than the first boost converter 112. The second boost converter 114 is a synchronous rectification type including a reactor L2, a switching transistor M2, and a synchronous rectification transistor M3. The charging current I _CHG2 generated by the second boost converter 114 can flow not only in the direction of charging the bank capacitor 104 but also in the direction of discharging it. When the voltage V _DC exceeds the target value V _REF , the second boost converter 114 can finely adjust the voltage _DC to decrease.

By the combined use of the first boost converter 112 and the second boost converter 114, the voltage V _DC of the bank capacitor 104 is brought close to the target voltage V _REF in a short time by the first boost converter 112, and the voltage is increased with high accuracy by the second boost converter 114. V _DC can be brought closer to the target voltage V _REF and stabilized.

Here, the first boost converter 112 needs to rapidly charge the bank capacitor 104 and is required to supply as much current I _CHG1 as possible to the bank capacitor 104 in one switching operation. Therefore, a large value is selected for the inductance of reactor L1.

  The charge amount is a time integration amount of the charge current. Therefore, when charging a certain amount of charge, the higher the current peak value, the shorter the charging pulse time width. In other words, the smaller the inductance, the faster the charging speed. The second boost converter 114 is required to quickly finely adjust the charge of the bank capacitor 104 by several switching operations. Therefore, the inductance of reactor L2 is preferably a value smaller than that of reactor L1.

FIG. 6 is an operation waveform diagram of the first boost converter 112. Preferably, first boost converter 112 is controlled to operate in a discontinuous mode. In the on-time _TON1 of the switching transistor M1, the reactor current I _L1 increases with time t at a slope V _IN / L1 according to the equation (1).
I _L1 = V _IN / L1 × t (1)

When the on-time of the switching transistor M1 is T _ON1 , the peak value I _PEAK of the reactor current I _L1 is expressed by Equation (2).
I _PEAK = V _IN / L1 × T _ON1 (2)

When the switching transistor M1 is turned off, the reactor current I _L1 decreases with time t at a slope (V _DC + Vf−V _IN ) / L1 according to the equation (3). Vf is a forward voltage of the rectifier diode D1. If normal DC / DC converter, V _DC is considered to be constant, the charging power supply 102 of FIG. 5, during the off time of the switching transistor M1, because the voltage V _DC increases, the slope is constant Absent. However, here, for ease of explanation, it is assumed that voltage _VDC is constant.
I _L1 = I _PEAK − (V _DC + Vf−V _IN ) / L1 × t (3)
If Vf is ignored, equation (4) is obtained.
I _L1 = I _PEAK − (V _DC −V _IN ) / L1 × t (4)

The hatched portion of reactor current _{IL1 in} FIG. 6 flows through rectifier diode D1, and is supplied to bank capacitor 104 as charging current _ICHG1 . By operating in the current discontinuous mode, the amount of charge supplied to the bank capacitor 104 by one switching is accurately controlled according to the _ON time TON, the inductance of the reactor L1, and the input voltage _{VIN of the} converter. Thus, the voltage V _DC of the bank capacitor 104 can be accurately controlled.

  Next, a converter control method will be described.

If the first boost converter 112 of the charging power source 102 is controlled using a PID controller or PI controller as in the conventional case, the calculation cost increases and causes a delay. Therefore, in the present embodiment, the ON time _TON1 of the first boost converter 112 is obtained by numerical calculation not using a PID controller or the like. Further, the first boost converter 112 is switched only once.

The amount of charge ΔQ to be supplied to the bank capacitor 104 can be calculated according to the equation (5) from the difference between the voltage V _INIT of the bank capacitor 104 before the start of charging and the target voltage V _REF . C _BANK is the capacity of the bank capacitor 104.
ΔQ = C _BANK × (V _REF −V _INIT ) (5)

Therefore, the on-time _TON1 of the switching transistor M1 may be calculated so that the integral value of the charging current I _CHG1 in FIG.
ΔQ = ∫I _CHG1 dt = I _PEAK × T _D1 / 2 = C _BANK × (V _REF −V _INIT )
(6)

Specifically, the on time _TON1 may be calculated as follows. A time T _D1 during which the current I _D1 (that is, the charging current I _CHG1 ) flows through the rectifier diode D1 can be calculated from the equation (4) and is expressed by the equation (7).
T _D1 = I _PEAK × L1 / (V _DC −V _IN ) (7)

Substituting equation (7) into equation (6) yields equation (8).
I _PEAK × I _PEAK × L1 / (V _DC −V _IN ) / 2 = C _BANK × (V _REF −V _INIT )
... (8)

By substituting equation (2) into equation (8) and solving for _TON1 , equation (9) is obtained.
T _ON1 = √ {2 × L1 × C _BAN × (V _REF −V _INIT ) × (V _DC −V _IN ) / V _IN ² }
... (9)

  This eliminates the need for PI control or PID control and reduces response delay. A specific arithmetic expression is not limited to this.

FIG. 7 is an operation waveform diagram of the charging power source 102 of FIG. When the high-frequency power supply 106 enters a halt period, first, the bank capacitor 104 is quickly charged by the first boost converter 112. Subsequently, switching of the transistors M2 and M3 of the second boost converter 114 is started, and the voltage V _DC of the bank capacitor 104 is further brought closer to the target voltage V _REF .

  Similarly to the first boost converter 112, the on-time of the switching transistor M2 and the synchronous rectification transistor M3 may be determined for the second boost converter 114 by arithmetic processing not using a PID controller or the like.

  In the above, this invention was demonstrated based on some embodiment. Those skilled in the art will understand that these embodiments are exemplifications, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. By the way. Hereinafter, such modifications will be described.

When the voltage _VDC can be made sufficiently close to the target value by charging by the first boost converter 112 of FIG. 5, the second boost converter 114 may be omitted. In the above description, the first boost converter 112 is switched only once, but may be switched twice or three times. What is necessary is just to prescribe | regulate the frequency | count of switching according to the capacitance value of the bank capacitor | condenser 104, and the inductance of the reactor L1.

  Further, the first boost converter 112 and the second boost converter 114 of the charging power source 102 may be controlled by a PID controller. When designing the first boost converter 112 and the second boost converter 114, it is not necessary to consider load fluctuations, and therefore the feedback loop may be designed to be stable in a no-load state. Therefore, the responsiveness can be improved as compared with the DC power supply 6 of FIG.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments merely show one aspect of the principle and application of the present invention. Many variations and modifications of the arrangement are allowed without departing from the spirit of the present invention defined in the scope.

DESCRIPTION OF SYMBOLS 100 ... Laser drive device, 102 ... Charging power supply, 104 ... Bank capacitor, 106 ... High frequency power supply, 110 ... Rectification smoothing circuit, 112 ... First boost converter, 114 ... Second boost converter, L1, L2 ... Reactor, M1 ... Switching transistor.

Claims (7)

A bank capacitor;
A high-frequency power source whose input is connected to the bank capacitor and intermittently supplies an alternating voltage to the laser light source;
A charging power source for charging the bank capacitor to a target voltage during a pause period of the high-frequency power source;
A laser driving device comprising:   The laser driving apparatus according to claim 1, wherein the charging power source includes a first boost converter.   The laser driving apparatus according to claim 2, wherein the first boost converter operates in a discontinuous mode.   4. The laser driving apparatus according to claim 2, wherein the charging power supply further includes a second boost converter having a reactor inductance smaller than the first boost converter. 5.   5. The laser drive device according to claim 4, wherein after the charging operation of the bank capacitor by the first boost converter, the operation proceeds to the charging operation of the bank capacitor by the second boost converter. 6. The first boost converter is a diode rectification type,
The laser driving apparatus according to claim 4, wherein the second boost converter is a synchronous rectification type.   7. The charging power supply according to claim 2, wherein the on-time of the first boost converter is obtained by a numerical calculation not based on PID (Proportional-Integral-Differential) or PI (Proportional-Integral) control. A laser driving device according to claim 1.

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