JPH1126846A - Laser power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser power supply device which can obtain a boost voltage for starting lighting of a lamp stabilized to fluctuations in an input power voltage to the device. SOLUTION: A D.C. voltage Ec is applied to an inverter 80. Drive circuits 85 and 86 act to alternately turn on a first set of transistors 81 and 84 and a second set of transistors 82 and 83 in the inverter 80. Through such switching operation, a high frequency A.C. voltage EM of a pulse (rectangular) shaped waveform is outputted from an output terminal of the inverter 80. The voltage EM is applied to a Cockcroft boosting circuit 87, in which the voltage EM is rectified in diodes D10 to D17 and boosted in superposition of voltage levels through a series circuit of capacitors C10 to C17. As a result, a D.C. boost voltage EF boosted up to about 8 times the voltage value (about 2800 V) can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0010]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser power supply for supplying power to a laser oscillation pump lamp.

[0020]

2. Description of the Related Art In a solid-state laser device such as a YAG laser,
The excitation lamp is turned on, and its light energy is applied to a laser medium such as a YAG rod to cause laser oscillation.

FIG. 7 shows a circuit configuration of a conventional laser power supply device used in this type of solid-state laser device.

In this laser power supply, output terminals [OUTa, OUTb] are connected to both electrode terminals of an excitation lamp (not shown) of the laser oscillation section.

The three-phase rectifier circuit 200 on the input side rectifies the three-phase AC voltage of the commercial frequency from the three-phase AC power supply terminals [U, V, W] and converts it into a DC voltage. This three-phase rectifier circuit 2
00, the DC charging current Ic flows through the electromagnetic switch 202 and the smoothing coil 204 to the capacitor 206,
Capacitor 206 is charged to a predetermined voltage, for example, 280V.

The capacitor 206 and the output terminals [OUTa, OUT
b], a discharge switching element 208 is connected in series. When the switching element 208 is turned on, the capacitor 206 is discharged, and the discharge current i
L is the switching element 208, the inductance coil 2
10. The current flows to the excitation lamp via the output capacitor 212 and the backflow prevention diode 214. The excitation lamp is turned on by the lamp current iL.

When the switching element 208 is turned off,
Although the discharge of the capacitor 206 is interrupted, the lamp current iL continues to flow due to the release of the electromagnetic energy and the charge energy stored in the inductance coil 210 and the output capacitor 212.

The discharge switching element 208 is turned on / off by a high frequency switching signal cs of, for example, 50 kHz from the control unit 220. As a result, the lamp current iL can be continuously supplied without interruption, the excitation lamp can be continuously lit, and continuous oscillation laser light can be obtained from the laser oscillation section. The voltage applied to the excitation lamp by such continuous oscillation is, for example, about 150 V in a rated value.

The backflow prevention diode 214 and the output terminal OUTa
A current sensor 216 for detecting the lamp current iL is provided between the two. In response to the output signal from the current sensor 216, the current detection circuit 218 obtains a lamp current detection signal SiL representing the magnitude of the lamp current iL (for example, a current effective value). The lamp current detection signal SiL is provided to the control unit 220.

The control unit 220 controls the lamp current i based on the lamp current detection signal SiL from the current detection circuit 218.
Switching element 2 so that L matches the set current value.
In addition to controlling the switching operation of step 08, the electromagnetic switch 202 is shut off when the lamp current iL becomes abnormally large due to the destruction of the switching element 208 or the like. The resistor 203 connected in parallel with the electromagnetic switch 202 is a current limiting resistor.

In this type of laser power supply device, as described above, a trigger circuit (not shown) for starting the excitation lamp to turn on, and a trigger circuit (not shown) for supplying the excitation lamp with power for laser oscillation to the excitation lamp are provided. A booster circuit is provided.

In the conventional laser power supply device shown in the figure, an AC voltage e (220 V) for one phase of a three-phase AC power supply voltage is supplied to the primary coil of the step-up transformer 224, and is supplied to the secondary coil of the step-up transformer 224. Boosted voltage (for example, 1
000V) is input to the booster circuit 226. The booster circuit 226 rectifies the AC voltage from the transformer 224 by the diodes d1 and d2 and boosts the AC voltage to, for example, 2500 V so as to be stacked on the capacitors c1 and c2. And applied to the excitation lamp as a boost voltage Ef.

When the excitation lamp is turned on, the control unit 22
0 activates the main power supply unit and the booster circuit 226 first. That is, for the main power supply unit, the electromagnetic switch 202
Is closed and the switching control signal cs is supplied to the switching element 208. For the booster circuit 226, the switch 222 provided in the primary circuit of the step-up transformer 224 is closed.

With the main power supply unit and the booster circuit 226 kept on standby in this way, the control unit 220 operates a trigger circuit (not shown). Then, the gas in the excitation lamp is broken down by the action of the trigger circuit, and the impedance of the lamp rapidly drops. When a boost voltage Ef of about 2500 V is applied to the excitation lamp from the booster circuit 226, the impedance of the excitation lamp further decreases, and a current flows into the excitation lamp. Thereafter, even with a lamp voltage of about 150 V from the main power supply, a lamp current iL large enough to light the lamp can flow.

[0150]

As described above, in the conventional laser power supply, the AC power supply voltage e is boosted by the boosting transformer 224, and the secondary voltage of the transformer 224 is further boosted by the boosting circuit or the booster circuit 226. By doing so, a booster voltage Ef of a required voltage value is generated.

However, in such a boost system, there is a problem that the AC voltage is apt to fluctuate and the boost voltage Ef becomes unstable. That is, the AC power supply voltage e
Is increased many times (for example, ten times) through the step-up transformer 224 and the booster circuit 226 and reflected on the boost voltage Ef.

For this reason, at the start of the lighting of the excitation lamp, the boost voltage Ef was considerably lower than the set voltage value (2500 V), so that the excitation lamp did not light or the boost voltage Ef became abnormally high. In some cases, the excitation lamp failed.

The present invention has been made in view of the above-mentioned problems, and provides a laser power supply device that obtains a boost voltage for starting an excitation lamp, which is stabilized with respect to a fluctuation of an input power supply voltage. The purpose is to:

Another object of the present invention is to provide a laser power supply device capable of obtaining a stable boost voltage even from a single-phase AC power supply voltage.

It is a further object of the present invention to provide a laser power supply device in which the excitation lamp is turned on safely at the start of lighting.

[0210]

According to a first aspect of the present invention, there is provided a laser power supply for supplying power to an excitation lamp of a laser oscillation unit, comprising: Rectifier circuit for inputting and rectifying, a capacitor for temporarily storing DC power from the rectifier circuit, charging voltage control means for controlling a charging voltage of the capacitor to a predetermined constant voltage value, and A lamp current supply unit that discharges stored electric energy to supply a lamp current to the excitation lamp, an inverter that inputs a charging voltage of the capacitor and converts the voltage into an AC voltage having a predetermined frequency higher than a commercial frequency, A booster circuit that boosts an AC voltage from the inverter to generate a DC boost voltage having a preset voltage value;
Lighting start control means for supplying the boost voltage to the excitation lamp at the start of lighting of the excitation lamp.

The second laser power supply of the present invention is the first laser power supply, wherein the AC voltage of the commercial frequency is a single-phase AC voltage, and the rectifier circuit rectifies the single-phase AC voltage by full-wave rectification. A single-phase rectifier circuit.

A third laser power supply according to the present invention, in the second laser power supply, wherein the charging voltage control means includes a switching means connected between the single-phase rectifier circuit and the capacitor; Switching control of the switching means at a predetermined frequency higher than the commercial frequency so that the phase of the charging current supplied to the capacitor from the single-phase rectifier circuit matches the phase of the DC voltage output from the single-phase rectifier circuit. And a power factor control means.

[0240]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a circuit configuration of a laser power supply device according to one embodiment of the present invention. This laser power supply device is incorporated in a solid-state laser device, for example, a YAG laser processing device, and supplies power to an excitation lamp 102 of a laser oscillation unit 100.

In laser oscillating section 100, excitation lamp 102 and YAG rod 104 (laser medium) are arranged adjacent to each other in a reflecting lens barrel (not shown) provided in chamber 106 made of, for example, acrylic resin. Have been. On the optical axis of the YAG rod 104 outside the chamber 106, a pair of optical resonator mirrors 108 and 110 are provided.
They are arranged facing each other in parallel with the rod 104 interposed therebetween.

When the excitation lamp 102 emits light by the lamp current IL supplied from the laser power supply of the present embodiment, which will be described later, the YAG rod 10
4 is excited, light emitted in the axial direction from both end surfaces of the YAG rod 104 is repeatedly reflected between the optical resonator mirrors 108 and 110, amplified, and then passes through the output mirror 108 as laser light LB. The laser beam LB that has passed through the output mirror 108 is directed to a processing point of a workpiece (not shown) via a mirror (not shown) or via an input unit, an optical fiber, and an output unit (not shown). Irradiation is aimed at.

The laser power supply device of this embodiment has a main power supply section 10 for supplying power for laser oscillation to the excitation lamp 102, a booster circuit 12 for starting the excitation lamp 102 and a trigger circuit (see FIG. And a power factor control circuit 34 for controlling the power factor of the main power supply unit.

The main power supply section 10 receives a single-phase AC power supply voltage EA having a commercial frequency (50 Hz or 60 Hz) and converts (rectifies) it into DC. Capacitor that temporarily stores power 1
8, a charging circuit 20 connected between the single-phase rectifier circuit 16 and the capacitor 18, a capacitor 18 and the excitation lamp 1
02 and a lamp current supply circuit 22 connected between the first and second lamps.

The single-phase rectifier circuit 16 is composed of, for example, a single-phase full-wave rectifier circuit. The single-phase full-wave rectifier circuit 16 rectifies the input single-phase AC voltage EA by full-wave rectification and repeats a half-wave of a sine waveform by 180 °. Output the DC voltage EB.

The charging circuit 20 includes a charging switching element 24 connected in parallel with the capacitor 18 between the single-phase rectifier circuit 16 and the capacitor 18, and a charging switching element 24 between the single-phase rectifier circuit 16 and the charging switching element 24. Inductance coil 26 connected in series and charging switching element 2
4 includes a diode 28 connected in series between the capacitor 4 and the capacitor 18.

An inductance coil 26 and a diode 28 are provided between the single-phase rectifier circuit 16 and the capacitor 18.
A charging bypass circuit including a current limiting resistor 30 and a backflow prevention diode 32 is connected in parallel with the charging circuit including. A thyristor 36 is provided as a switch of the charging circuit. The conduction (on) / interruption (off) state of the thyristor 36 is controlled by a thyristor control circuit 38.

The charging switching element 24 comprises, for example, an FET (Field Effect Transistor), and is switched by the power factor control circuit (PFC) 34 of the present embodiment.

As will be described later, the power factor control circuit 34 adjusts the phase of the charging current Ic supplied to the capacitor 18 to the phase of the DC voltage EB output from the single-phase rectification circuit 16, for example, a high frequency of 70 kHz. The switching of the charging switching element 24 is controlled by the frequency. As a result, the excitation lamp 1
The ratio of the active power actually (effectively) supplied to the 02 side, that is, the power factor can be made as close to 1 as possible. Therefore, high power efficiency and laser oscillation efficiency can be realized in a single-phase power supply device. Also, for example, the charging voltage Ec of the capacitor 18 with respect to the input AC voltage EA of 220 V
Is raised to, for example, 360 V, so that the input AC power supply supplies stable power not affected by voltage fluctuations to the excitation lamp 1.
02 can be supplied.

The lamp current supply circuit 22 includes a discharge switching circuit 40, an inductance coil 42, an output capacitor 44, a return diode 46, and a backflow prevention diode 48.

The discharging switching circuit 40 is, for example, an FET or an IGBT (Insulated Gate Bipolar transistor).
stor) and a pair of switching elements 40a, 40
b. These switching elements 40
The switching of a and 40b is controlled by a switching control signal Ga and Gb of, for example, 50 kHz from the control unit 14 so as to be alternately turned on.

When one of the discharge switching elements 40a, 40b, for example, 40a is on,
The capacitor 18 is discharged, and the discharge current IL is turned on.
2. Output capacitor 44 and backflow prevention diode 48
Through the excitation lamp 102. The excitation lamp 102 is turned on by this discharge current, that is, the lamp current IL.

When the switching element 40a is turned off,
Although the discharge of the capacitor 18 is temporarily stopped, the lamp current IL continues to flow by discharging the electromagnetic energy and the charge energy stored in the inductance coil 42 and the output capacitor 44. Immediately after this, the other switching element 40b is turned on and the capacitor 18
Discharge resumes.

As described above, the dual discharge switching element 4
Since 0a and 40b are alternately turned on by the high-frequency switching control signals Ga and Gb of 50 kHz, the lamp current IL flows continuously without interruption. This allows
The excitation lamp 102 is continuously turned on, and continuous oscillation laser light LB is obtained from the laser oscillation unit 100.

The backflow prevention diode 48 and the excitation lamp 10
2, a current sensor 50 for detecting the lamp current IL is provided. In response to the output signal of the current sensor 50, the current detection circuit 52 obtains a lamp current detection signal SIL representing the magnitude of the lamp current IL (for example, a current effective value). This lamp current detection signal SIL is provided to the control unit 14.

Both terminals of the output capacitor 44 are connected to the input terminal of the voltage detecting circuit 54, and a voltage detecting signal SED representing the voltage ED of the output capacitor 44 is obtained at the output terminal of the voltage detecting circuit 54. This voltage detection signal SED is also supplied to the control unit 14.

A temperature sensor 56 composed of, for example, a thermistor is provided near the switching circuit 40 for discharge. In response to the output signal of the temperature sensor 56, the temperature detection circuit 56 outputs a temperature detection signal ST indicating the temperature in the vicinity of the discharge switching circuit 40. This temperature detection signal ST is also provided to the control unit 14.

The control unit 14 comprises, for example, a microprocessor, and is connected to an input device, a display device, etc. (not shown) via an appropriate interface circuit (not shown).
The required control in the apparatus is performed based on various set values and various measured values according to a predetermined program.

That is, the control unit 14 controls the current detection circuit 5
4, a switching control signal G modulated by, for example, pulse width modulation (PWM) so that the lamp current IL matches the set current value.
a and Gb are supplied to the discharge switching elements 40a and 40b via a drive circuit (not shown).

Further, the control section 14 outputs control signals Ki and Kt for stopping the main power supply section 10 when the lamp current IL becomes excessively large or when the discharge switching circuit 40 becomes overheated. To the thyristor control circuit 38.

In the normal state, the control signals Ki and Kt are held at the H level, respectively, so that the H level control signal K is supplied to the thyristor control circuit 38 from the output terminal of the AND gate 60. Thus, the thyristor control circuit 38 holds the thyristor 36 in the ON (conductive) state.

However, for example, when the discharge switching circuit 40 is destroyed and the lamp current IL exceeds a predetermined current monitoring value, the control signal Ki goes low, whereby the output signal K of the AND gate 60 also goes low. Level, and the thyristor control circuit 38 turns off (cuts off) the thyristor 36
Switch to state. Further, the discharge switching circuit 40
If the temperature rises to a level higher than the predetermined temperature monitoring value even if the thyristor does not break down, the control signal Kt goes low, and in response, the thyristor control circuit 38 turns the thyristor 36 off (interrupted). It is designed to switch.

[0480] The control unit 14 controls the booster circuit 12 by the inverter switching control signal HV. The booster circuit 12 of the present embodiment includes a capacitor 18
Is input, and a predetermined voltage required for starting the lighting of the excitation lamp 102, for example, a boost voltage E of 2500 V is input.
Generates F.

FIG. 2 shows a circuit configuration of the booster circuit 12. The booster circuit 12 includes an inverter 80, inverter driving circuits 85 and 86, a Cockcroft boosting circuit 87
And a boost voltage output circuit 90.

The inverter 80 has four transistors 8
1, 82, 83 and 84 are bridge-connected, and the DC voltage Ec from the capacitor 18 is received at input terminals 88 and 89. The drive circuits 85 and 86 respond to the two-phase inverter switching control signals HVa and HVb of which the phases are different from each other by 180 ° from the control unit 14, and the first set of transistors (81 and 84) of the inverter 80 and the second set of The transistors (82, 83) are turned on alternately. Inverter
The switching control signals HVa and HVb are, for example, 50
Provided as pulses having a frequency of kHz.

By performing the switching operation as described above, the inverter 80 has a voltage level (amplitude) substantially equal to the voltage level of the input DC voltage Ec, and has a pulse shape (frequency) equal to the switching frequency (50 kHz). A high-frequency AC voltage EM (square wave) is output. This high-frequency AC voltage EM is input to the Cockcroft booster circuit 87.

The Cockcroft booster circuit 87 has eight capacitors C10 to C17 and eight diodes D10 to D17.
Are connected in the form of a ladder. The high-frequency AC voltage EM having an amplitude of 360 V and a frequency of 50 kHz from the inverter 80 is rectified by the diodes D10 to D17 and is increased in series with the capacitors C10 to C17. To about 8 times the voltage value (about 2800 V).

The boost voltage from the Cockcroft boosting circuit 87 is once charged in an output capacitor 92 formed by connecting eight 100 μF electric field capacitors CE in series, for example, and then output through a resistor 93 and a backflow prevention diode 94 to an output terminal 95. , 96. Note that, for example, a diode having a withstand voltage of 600 V is used as the backflow prevention diode 94.

As described above, the DC voltage Ec from the capacitor 18 is input to the booster circuit 12 according to the present embodiment. This capacitor voltage Ec is equal to the single-phase rectifier circuit 1
6. The charge circuit 20 and the power factor control circuit 34
This is a constant voltage obtained by rectifying and boosting the single-phase AC power supply voltage EA of 0 V at a high power factor, and is stably maintained at the set voltage value (360 V) without being affected by the fluctuation of the AC power supply voltage EA.

In the booster circuit 12, the input DC voltage E
c is converted by an inverter 80 into a high frequency (50 kHz) pulsed AC voltage EM. AC power supply voltage EA
The voltage level of the input DC voltage Ec is stable at the set voltage value (360 V) with respect to the fluctuation of the pulsed AC voltage EM.
60V).

Then, such a high-frequency pulse-like AC voltage EM having a stable voltage level (amplitude) from the inverter 80 is boosted by being rectified by the Cockcroft boosting circuit 87 so as to be stacked in small increments at a high frequency. And a stable high voltage DC boost voltage EF is obtained.

As described above, the voltage level of the DC voltage Ec input to the booster circuit 12 is stable, and the frequency of the DC voltage Ec is higher than that of the inverter 80, that is, the fine pulse AC voltage Ec.
Since M is applied to Cockcroft booster circuit 87, the voltage level of boost voltage EF is also stable, and is maintained at a set value (for example, 2700 V) without being affected even if AC power supply voltage EA fluctuates. .

[0580] The booster circuit 12 includes the excitation lamp 10
2 is used to start lighting. Excitation lamp 1
Numeral 02 is composed of, for example, a xenon lamp, electrode terminals are attached to both ends of a glass tube, and gas is sealed in the tube.
In order to turn on the excitation lamp 102, it is necessary to break through the gas insulation in the lamp and discharge between both electrodes.

When lighting the excitation lamp 102, the control unit 14 first activates the main power supply unit 10 and the booster circuit 12. That is, for the main power supply section 10, the control signals Ki and Kt are set to the H level so that the thyristor control circuit 3
8, the thyristor 36 is turned on, and the switching control signals Ga and Gb are supplied to the discharge switching circuit 40. Further, for the booster circuit 12, the inverter switching control signals HVa and HVb are supplied to the inverter drive circuits 85 and 86, respectively.

Then, the control section 14 operates a trigger circuit (not shown). The trigger circuit breaks down the gas in the lamp 108 by applying a high voltage of about 20 kV between the cathode terminal of the excitation lamp 102 and a metal plate disposed around the glass tube of the lamp 102, and reduces the impedance. Lower. Then, a current flows into the excitation lamp 102 at a high voltage of about 2500 V from the booster circuit 12 so as to follow thereafter, and the impedance of the excitation lamp 102 further decreases. Thereafter, a sufficiently large current (lamp current IL) can flow even with a lamp voltage ED of about 150 V from the main power supply unit 10.

When the excitation lamp 102 starts lighting,
The control unit 14 controls the inverter switching control signal HV
The supply of (HVa, HVb) is stopped, and the operation of the booster circuit 12 is stopped. As the backflow prevention diode 48 of the main power supply unit 10, for example, a high withstand voltage type diode having a withstand voltage of 3200V is used.

In the laser power supply device of this embodiment, at the start of lighting of the excitation lamp, even if the input AC power supply voltage EA fluctuates, the set voltage value (2700) is supplied from the booster circuit 12.
V) A stable boost voltage E maintained or constant voltage
Since F is supplied to the excitation lamp 102, the excitation lamp 1
02 starts lighting with safety.

In the laser power supply of this embodiment, the single-phase rectifier circuit 16, the charging circuit 20, and the capacitor 18 are shared by the main power supply 10 and the booster circuit 12. However, temporally, the booster circuit 12 operates only at the start of lamp lighting, and only the main power supply unit 10 functions after lighting, so that there is no problem of contention.

Next, the configuration and operation of the power factor control circuit 34 in this embodiment will be described with reference to FIGS.

[0650] Fig. 3 shows a circuit configuration of the power factor control circuit 34. The power factor control circuit 34 includes a reference value generation circuit 61, a bypass circuit 62, a switching timing detection circuit 63, a clock circuit 64, and a current switching circuit 65.

The reference value generating circuit 61 includes a voltage dividing circuit 66, a reference voltage source 67, an operational amplifier 68, and a multiplier 69. The voltage dividing circuit 66 divides the charging voltage EC of the capacitor 18 at a constant ratio k by the resistors r1 and r2. The operational amplifier 68 receives the divided voltage k from the voltage dividing circuit 66.
The difference between Ec and the reference voltage E0 from the reference voltage source 67 (E
0 -kEc). The multiplier 69 includes the single-phase rectifier circuit 16
DC voltage EB of the full-wave rectified waveform from
And the difference voltage (E0-kEc) from the operational amplifier 68 is input to the other input terminal Y, and the product [EB (E0-kEc)] of the two input voltage values is calculated, and the value of the product is calculated. A voltage signal representing (instantaneous value) is generated from an output terminal Z as a reference value signal JC.

The reference value signal JC obtained from the reference value generation circuit 61 is proportional to the DC voltage EB from the single-phase rectifier circuit 16 and inversely proportional to the charging voltage EC of the capacitor 18. That is, the reference value signal JC has a voltage waveform similar to the waveform of the DC voltage EB from the single-phase rectifier circuit 16, and when the capacitor voltage EC decreases, the voltage level (amplitude) increases and the capacitor voltage EC increases. And voltage level (amplitude)
Has the characteristic of becoming smaller.

[0680] Reference value signal JC from reference value generation circuit 61
Is supplied to the switching timing detection circuit 63. The switching timing detection circuit 63 has a current sensor 70 and a comparator 72. The current sensor 70 includes a current transformer coil 71, a diode d3, and a resistor r3, and generates a current detection signal (voltage) SIsw representing the current value (instantaneous value) of the bypass current Isw flowing through the bypass circuit 62.
The comparator 72 detects the current detection signal SI from the current sensor 71.
sw and the reference value signal JC from the reference value generating circuit 61 are input, and when the voltage level of SIsw reaches the voltage level of JC, an H level pulse is output as the switching timing signal AH. This switching timing signal AH is provided to the current switching circuit 65.

The current switching circuit 65 is composed of an RS flip-flop, and its set terminal S is supplied with a high frequency, for example, 75 kHz clock pulse CK from the clock circuit 64.
And receives a switching timing signal AH from the switching timing detection circuit 63 at its reset terminal R. The output Q of the current switching circuit 65 is provided to one input terminal of the AND gate 73. A clock pulse C from the clock circuit 64 is applied to the other input terminal of the AND gate 73.
K is input. The output of the AND gate 73 is given as a control pulse DP to the gate terminal of the charging switching element 24.

FIG. 4 shows the operation of the power factor control circuit 34. When each clock pulse CK is output from the clock circuit 64, the output Q of the current switching circuit 65 becomes H level at the start end thereof, and the H level control pulse DP is output from the AND gate 73. In response to the H-level control pulse DP, the charging switching element 24 is turned on, and the bypass circuit 62 is turned on substantially in a short-circuit state. Then, the current path on the output side of the single-phase rectifier circuit 16 is changed from the path that has been flowing to the capacitor 18 side to the bypass circuit 6.
Switch to the path flowing through 2. That is, the capacitor 18
The charging current Ic flowing into the bypass circuit 62 is interrupted once and the bypass current 62 is supplied to the bypass circuit 62 instead.
sw starts to flow. At this switching point, the current value of the charging current Ic (the value at the time of interruption) and the current value of the bypass current Isw (the initial value) are continuous.

When the bypass current Isw flows through the bypass circuit 62, the switching timing detection circuit 63 outputs the current detection signal S corresponding to the bypass current Isw from the current sensor 70.
Isw occurs. The bypass current Isw rises rapidly from the initial value at the time of switching, and the current detection signal S
Isw also rises rapidly. On the other hand, the voltage level of the reference value signal JC from the reference value generation circuit 61 is
Of the output voltage EB (full-wave rectified waveform) and changes in a sinusoidal manner.

When the voltage level of current detection signal SIsw reaches the voltage level of reference value signal JC, comparator 7
The H-level switching timing signal AH is instantaneously output from the output terminal 2.

Then, the switching timing signal AH
, The output Q of the current switching circuit 65 becomes L level, and the control pulse DP of the output of the AND gate 73 also falls to L level. As a result, the charging switching element 24 is turned off, and the bypass circuit 62 is shut off.

When the bypass circuit 62 is cut off, the current path on the output side of the single-phase rectifier circuit 16 is switched to the path on the capacitor 18 side. Therefore, the charging current Ic to the capacitor 18 starts to flow at the same time as the bypass current Isw stops. At this time, an electromotive force is generated in the inductance coil 26 based on the bypass current Isw that has flowed immediately before, and the electromotive force is generated by the output voltage E of the single-phase rectifier circuit 16.
B is applied to the capacitor 18. As a result, the charging current Ic starts to flow at an initial value equal to the current value when the bypass current Isw is interrupted. However, since the impedance of the charging circuit is larger than the impedance of the bypass circuit 62 in the short-circuit state, the charging current Ic gradually decreases from the initial value.

[0750] When the next clock pulse CK is output from the clock circuit 64, the next cycle CY starts, and the current switching circuit 65 switches the charging current Ic to the bypass current Isw in the same manner as described above. And
When the bypass current Isw reaches the reference value signal JC, it is switched from the bypass current Isw to the charging current IC in the same manner as described above.

[0760] Even when the output Q of the current switching circuit 65 remains at the H level when the clock pulse CK falls from the H level to the L level in each cycle CY (that is, the bypass current Isw Even if the signal JC has not been reached), the control pulse DP of the output of the AND gate 73
Becomes L level, and the charging switching element 24 is forcibly switched to the off state.

When the output voltage EB of the single-phase rectifier circuit 16 is at a relatively low level (at the bottom of the full-wave rectified waveform), the level of the reference value signal JC also becomes lower, but the bypass current Isw
May be smaller than this and may not reach the reference value signal JC within the H level period of the clock pulse CK. But,
By the forced switching function as described above, the clock pulse C
During the period when K is at the L level, the current is always switched to the charging current Ic.

On the other hand, when the output voltage EB of the single-phase rectifier circuit 16 is at a relatively high level (at a portion near the peak value of the full-wave rectified waveform), the level of the reference value signal JC is high. , The degree of increase of the bypass current Isw is greater than that, and reaches the reference value signal JC in a short time. Therefore, the charging current Ic flows with a large current value over most of the period of each cycle CY.

The duty ratio of clock pulse CK in each cycle can be arbitrarily selected. For example, the H level period may be set to 80%, and the L level period may be set to 20%.

As described above, in the power factor control circuit 34, the charging current has a current waveform that follows the waveform (full-wave rectification waveform) of the output voltage EB of the single-phase rectification circuit 16, that is, the phases are matched. Ic is supplied to capacitor 18. Thereby, the ratio of the active power actually (effectively) supplied to the excitation lamp 102 side with respect to the input power from the single-phase AC power supply, that is, the power factor can be made as close to 1 as possible.

[0810] Therefore, in a single-phase laser power supply, high power efficiency and laser oscillation efficiency equal to or higher than those of a three-phase laser power supply can be realized, and high-output laser light LB can be obtained.

Also, in a three-phase power supply device, the three-phase rectifier circuit occupies a large space, and the size, weight, and price of the entire device increase. In that respect, the single-phase rectifier circuit is small and does not take up much space. In addition, in this laser power supply 10, 75 k
Since the charging current Ic flows at a high frequency of about Hz, the inductance coil 26 of the charging circuit can be reduced in size. This makes it possible to reduce the weight and size of the entire apparatus and reduce the cost.

[0832] In this laser power supply, the electromotive force based on the electromagnetic energy stored in the inductance coil 26 by the bypass current Isw is added to the DC voltage EB from the single-phase rectifier circuit 16 and supplied to the capacitor 18. The capacitor 18 is charged by the boosting method. As a result, the charging voltage Ec of the capacitor 18 is changed to the input AC voltage EA (220
V) to a desired voltage higher than V), for example, 360V.

As described above, since the capacitor 18 is charged to a voltage higher than the input AC voltage EA at a high power factor, the charging voltage EB of the capacitor 18 can be maintained constant against fluctuations in the power supply voltage and the like.

FIG. 5 shows the output voltage EB and the charging current Ic of the single-phase rectifier circuit 16 in the laser power supply of this embodiment.
3 shows the waveforms of FIG. FIG. 6 shows, as a comparative example, waveforms of the output voltage EB and the charging current Ic 'when the power factor control circuit 34 is not provided. In a conventional single-phase laser power supply,
Since the power factor control circuit 34 is not provided, the power factor can be increased only to about 60%. On the other hand, in the laser power supply device 10 of the present embodiment, the power factor can be improved to about 98% by including the power factor control circuit 34.

According to the power factor control circuit 34 of this embodiment, the current IL supplied to the capacitor 18 is
Since the output voltage EB is adjusted not only in phase but also in waveform, an extremely high power factor can be realized. However, it is possible to achieve a relatively high power factor simply by matching the phases, even if the waveforms are completely separate.

In the above-described embodiment, the generation start / end of the boost voltage EF in the booster circuit 12 is controlled by the inverter switching control signal HV from the control unit 14. However, other schemes, such as capacitor 18
Open / close switch (not shown) between the power supply and the booster circuit 12
It is also possible to control the start / end of the generation of the boost voltage EF by opening and closing the switch.

[0880] The boost voltage EF is detected by a voltage detection circuit (not shown), and the control unit 14 generates an inverter switching control signal HV by a feedback system, for example, a pulse width control system, based on the voltage detection signal. It may be.

Although the laser power supply of the above embodiment uses a single-phase AC power supply as an input AC power supply, the present invention is also applicable to a power supply device using a three-phase AC power supply.

[0900]

As described above, according to the laser power supply of the present invention, the input AC power supply voltage is obtained by rectifying and converting the input AC power supply voltage to a stable DC voltage to a capacitor and discharging the capacitor. The lamp current is used to drive the excitation lamp for laser oscillation, and at the start of lamp lighting, the charging voltage of this capacitor is converted to a high-frequency AC voltage by an inverter, and then the high-frequency AC voltage is boosted by a booster circuit to obtain a stable voltage. Since an appropriate boost voltage is applied to the excitation lamp, it is possible to start the excitation lamp safely and reliably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a laser power supply device according to one embodiment of the present invention.

FIG. 2 is a circuit diagram showing a circuit configuration of a booster circuit in the embodiment.

FIG. 3 is a circuit diagram illustrating a circuit configuration of a power factor control circuit according to the embodiment.

FIG. 4 is a waveform chart showing waveforms at various parts of the power factor control circuit according to the embodiment.

FIG. 5 is a waveform diagram showing a phase relationship between an output voltage of a rectifier circuit and a capacitor charging current in the single-phase laser power supply device of the embodiment.

FIG. 6 is a waveform diagram illustrating a phase relationship between an output voltage of a rectifier circuit and a capacitor charging current in a single-phase laser power supply device without a power factor control circuit according to an embodiment.

FIG. 7 is a block diagram showing a circuit configuration of a conventional laser power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main power supply part 12 Booster circuit 14 Control part 16 Single-phase rectifier circuit 18 Capacitor 20 Charging circuit 22 Lamp current supply circuit 24 Charging switching element 26 Reactance coil 28 Diode 34 Power factor control circuit 80 Inverter 85, 86 Inverter driving circuit 87 Cockcroft Step-up circuit 90 Boost voltage output circuit 100 Laser oscillation unit 102 Excitation lamp 104 YAG rod (laser medium)

Claims (3)

[Claims] 1. A laser power supply device for supplying power to an excitation lamp of a laser oscillation unit, comprising: a rectifier circuit for inputting and rectifying an AC voltage of a commercial frequency; a capacitor for temporarily storing DC power from the rectifier circuit; Charge voltage control means for controlling the charge voltage of the capacitor to a predetermined constant voltage value, lamp current supply means for discharging electric energy stored in the capacitor and supplying a lamp current to the excitation lamp, An inverter that inputs a charging voltage of the capacitor and converts the voltage into an AC voltage having a predetermined frequency higher than a commercial frequency; and a booster circuit that boosts the AC voltage from the inverter to generate a DC boost voltage having a predetermined voltage value. A lighting start control means for supplying the boost voltage to the excitation lamp at the start of lighting of the excitation lamp; Laser power supply apparatus characterized by comprising and. 2. The method according to claim 1, wherein the AC voltage at the commercial frequency is a single-phase AC voltage, and the rectifier circuit is a single-phase rectifier circuit that performs full-wave rectification on the single-phase AC voltage. Laser power supply. 3. The charging voltage control means includes a switching means connected between the single-phase rectifier circuit and the capacitor, and a charging current supplied from the single-phase rectifier circuit to the capacitor. The power factor control device according to claim 2, further comprising: a power factor control device that performs switching control of the switching device at a predetermined frequency higher than the commercial frequency so as to match a phase of the DC voltage output from the phase rectifier circuit. Laser power supply.