JP2844646B2 - Shimmer circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Industrial applications]

The present invention relates to a simmer circuit for maintaining a discharge state of a flash lamp by supplying a minimum current even when the lighting of the flash lamp is stopped, in order to shorten the rise time and the extinction time of the discharge of a flash lamp for exciting a solid-state laser.

[Prior art]

Currently, solid-state lasers for processing are almost exclusively limited to those using Nd: YAG as a laser medium because of their good oscillation stability and relatively high output. Nd: YAG, a leather medium, is a rod-like material that contains an optical crystal called yttrium aluminum garnet (Y ₃ AI ₅ O ₁₂ ) containing Nd in a small weight ratio of about 1%. Both ends are mirror-polished, and an anti-reflection coating is applied thereon. The side is ground glass, and the excitation light is YA
It is designed to be easily absorbed by the entire G bar. The YAG rod absorbs light having a wavelength of 500 to 800 nm, enters a so-called excited state, and emits a laser beam having a wavelength of about 1.06 μm. The output form is normally a continuously repeated normal pulse. This is a laser beam concentrated in a pulse for a short time, and has a high energy density in order to improve the so-called sharpness. The continuous repetition normal pulse is obtained by controlling the laser output waveform by turning on the excitation lamp in a pulsed manner, that is, as a flash lamp, and electrically controlling the lamp lighting time width and the lamp current value. As a flash lamp, a straight discharge tube using xenon (Xe) gas or krypton (Kr) gas is widely used from the viewpoints of long life, reliability, and ease of use. A discharge power supply device including a conventional example will be described with reference to FIG. 5 which is a block diagram thereof. In FIG. 5, 1 is a DC power supply, 2 is a chopper circuit, 3 is a capacitor, 4 is a trigger circuit, 5 is a flash lamp (hereinafter simply referred to as a lamp), 6 is a main switch circuit, and 30 is a simmer circuit. The simmer circuit 30 mainly includes a DC power supply 31, a diode 32, and a resistor 33. In order to cause the lamp 5 to emit flash light, first, the trigger circuit 4 applies a high-voltage trigger pulse of 10 to 20 KV to the lamp 5 to start discharging. Immediately thereafter, the simmer circuit 30 operates as a current source of 100 to 150 V and several A, thereby keeping the lamp 5 in a discharged state. next,
When the main switch circuit 6 is turned on, the electric energy of the capacitor 3 charged to 300 to 900 V is supplied to the lamp 5 as a current of several hundreds A by the DC power supply 1 and the chopper circuit 2, and the lamp 5 is turned on. . High-energy light generated by this lighting irradiates a laser medium (not shown), and excites the laser medium to cause laser oscillation. In the operation described above, the output characteristics of the simmer circuit 30 are important in order for the lamp 5 to be reliably switched to the simmer mode by the trigger circuit 4. For example, when a trigger voltage is applied, 4 to 15 times the simmer mode voltage is applied. Voltage is required. In FIG. 4, a solid line S1 shows the characteristics of the simmer circuit 30, and a broken line L1 and a double broken line L2 show the characteristics of two different lamps, with the current I on the horizontal axis and the voltage E on the vertical axis. When the lamp 5 of FIG. 5 has the characteristic of the dashed line L1, no simmer current flows before the lamp 5 is triggered, so that the voltage applied to the lamp 5 is equal to the voltage _Eo of the DC power supply 31. Once the time of lighting rest after being lit, the lamp 5, determined by its internal impedance and the resistor 33, the minimum current I _s capable of maintaining discharge state becomes flow simmer mode. In addition,
The diode 32 is connected to the DC power source 1 by the operation of the main switch circuit 6.
Current from flowing into the simmer circuit 30 from above.

[Problems to be solved by the invention]

The conventional simmer circuit 30 of FIG. 5 described above has the following disadvantages. (1) When the lamp 5 has the characteristics of the double dashed line L2 in FIG. 4, there is a problem that two simmer currents exist due to the relationship with the solid line S1 indicating the characteristics of the simmer circuit 30. (2) Since resistors are used, the power loss is large and the efficiency is only about 25%. This is shown in FIG.
A case of the E _o = 4E _s, further E _O increases efficiency decreases. (3) For the reason described in the preceding paragraph, since the loss in the resistor is several hundred watts, a resistor having a large size is required, and therefore, fan cooling may be required in some cases. (4) The DC power supply 31 needs to be insulated from other power supplies, and is generally boosted using a commercial power supply and a transformer, and then rectified and smoothed. However, the outer shape and weight of this transformer become large. . SUMMARY OF THE INVENTION An object of the present invention is to provide a simmer circuit which solves the above problems of the prior art and improves the efficiency, size and weight.

[Means for Solving the Problems]

In order to solve this problem, a simmer circuit according to the present invention is a circuit for maintaining a discharge state by flowing a predetermined current to a flash lamp when the flash lamp is stopped, and an inverter for obtaining AC power from a DC power supply for the flash lamp. A reactor and a transformer connected in series at an output stage of the inverter; a rectifying / smoothing circuit provided on a secondary side of the transformer; an output voltage of the rectifying / smoothing circuit and flowing through the reactor and the transformer. A control circuit for determining the frequency of the inverter based on the current.

[Operation]

The AC current generated in the reactor by the inverter is
The value is changed to a value corresponding to the winding ratio of the transformer, transmitted to the secondary side, and converted into a direct current smoothed by a rectifying / smoothing circuit. At this time, if the ON / OFF frequency of the inverter is kept constant, the impedance of the reactor becomes constant, and it works almost the same as the resistance. Before entering the simmer mode, the transformer has almost no load and only the exciting current flows through its primary side, so there is almost no voltage drop in the reactor and half of the DC power supply voltage is equal to the transformer turns ratio. Rectification
Output from the output terminal of the smoothing circuit. After the shift to the simmer mode, the load of the transformer is a flash lamp, and on the primary side of the transformer, the impedance of the flash lamp according to the winding ratio is connected in series to the reactor. A predetermined voltage and current are output from the end.

【Example】

An embodiment of a discharging power supply device including a simmer circuit according to the present invention will be described with reference to FIG. 1 of a block diagram showing the configuration thereof. In FIG. 1, the configuration is the same as that of the conventional example in FIG. 5, except for a simmer circuit 10 surrounded by a dashed line. The configuration of the simmer circuit 10 is as follows. An inverter arm of MOS-FETs 11 and 12 connected in series and a pair of capacitors 15 and 16 connected in series are respectively connected in parallel to the DC power supply 1, and each midpoint between the inverter arm and the capacitor is connected to a reactor. 13, a current transformer 17 and a transformer 14 connected in series. The capacitor 22, the rectifier circuit 18, and the smoothing circuit 19 are connected to the secondary side of the transformer 14. A voltage detector 20 is provided at an output terminal of the smoothing circuit 19. The control circuit 21 controls the on / off frequencies of the MOS-FETs 11 and 12 based on signals from an AC device 17 as a current detector related to the reactor 13 and a voltage detector 20 related to an output terminal of the smoothing circuit. I do. By the frequency control of the control circuit 21,
The simmer circuit 10 can be provided with a constant current characteristic as shown by a solid line S2 in FIG. 2, and as a result, even for a lamp having a characteristic as shown by a double broken line L2 (see FIG. 4), only one A simmer current is obtained, and the disadvantages in the conventional example are eliminated. In FIG. 2, the voltage E follows a trajectory like a broken line and shifts to the simmer mode, and finally the constant current characteristic S2
Leads to. The function of the capacitor 22 is that before the lamp 5 is triggered,
That is, the voltage applied to the lamp before the simmer current flows is slightly increased to facilitate the lighting of the lamp. That is,
Since the no-load voltage of the lamp has some variation, the lamp may not be turned on when the lamp is replaced depending on design conditions, and it is necessary to eliminate this fear. In FIG. 3, the solid line S1 shows the characteristics of the simmer circuit when the capacitor 22 is not provided, especially without frequency control, and the solid line S2 shows the simmer circuit when the capacitor 22 is inserted, particularly without frequency control. The characteristics of each capacitor
By inserting a 22, can be obtained slightly higher no-load voltage E _c from the voltage E _o of the DC power supply 1.

【The invention's effect】

Therefore, according to the present invention, the following excellent effects are obtained as compared with the prior art. (1) Since the loss of the inverter is smaller than the large loss due to the resistance in the conventional example, the efficiency can be improved from about 25% of the conventional to about 90%. (2) Approximately 30% of the external dimensions and weight can be eliminated because the commercial transformer and resistor required in the conventional example are not used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a discharge power supply device including an embodiment according to the present invention, FIG. 2 is a characteristic diagram of this embodiment, FIG. 3 is a characteristic diagram of another embodiment, and FIG. FIG. 5 is a block diagram showing a configuration of a discharge power supply device including a conventional example. Description of symbols 1: DC power supply, 2: Chopper circuit, 3: Capacitor, 4: Trigger circuit, 5: Lamp, 6: Main switch circuit, 10: Simmer circuit, 11, 12: MOS-FET, 13: Reactor, 14: Transformers, 15, 16, 22: capacitors, 17: current transformers, 18: rectifier circuits, 19: smoothing circuits, 20: voltage detectors, 21: control circuits.

Continuation of the front page (56) References JP-A-63-43295 (JP, A) JP-A-60-20728 (JP, A) JP-A-63-43297 (JP, A) JP-A-63-43296 (JP, A) JP-A-57-174895 (JP, A) JP-A-52-135377 (JP, U) JP-A-56-92396 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB Name) H05B 41/32 H05B 41/29

Claims (2)

(57) [Claims] 1. A circuit for maintaining a discharge state by supplying a predetermined current to a flash lamp when the flash lamp is turned off, comprising: an inverter for obtaining AC power from a DC power supply for the flash lamp; and a series provided at an output stage of the inverter. A connected reactor and transformer; a rectifying / smoothing circuit provided on the secondary side of the transformer; and determining a frequency of the inverter based on an output voltage of the rectifying / smoothing circuit and a current flowing through the reactor and the transformer. A control circuit; and a simmer circuit. 2. The simmer circuit according to claim 1, wherein a capacitor inserted in parallel is included on the secondary side of the transformer.