JPH02250294A - Shimmer circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention particularly relates to a simmer circuit that maintains the discharge state of a flash lamp by flowing a minimum current even when the flash lamp is not lit, in order to shorten the rise time and extinction time of the discharge of a Franche lamp for excitation with a solid-state laser.

[Conventional technology]

Current solid state lasers for processing are mostly limited to those using Nd:YAG as a laser medium because of their good oscillation stability and relatively large output. The laser medium Nd:YAG is an optical crystal called yttrium aluminum garnet (YJIsO+z) containing a trace amount of Nd at a weight ratio of approximately 1%. , apply a non-reflective coating on it. The side surfaces are made into a frosted glass shape so that the excitation light is easily absorbed by the entire YAG rod. Note that the YAG rod absorbs light of 500 to 800 n-, enters a so-called excited state, and oscillates a laser beam of around 1.06 microns. The output form is usually a continuously repeated normal pulse. This is a laser beam that is concentrated in pulses over a short period of time, and has a high energy density to improve so-called sharpness. This continuously repeated normal pulse is obtained by lighting the excitation lamp in a pulsed manner, that is, as a flash lamp, and controlling the laser output waveform by electrically controlling the lamp lighting time width and lamp current value. As flash lamps, straight discharge tubes using xenon (Xe) gas or krypton (Kr) gas are 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 Figure 5, 1 is a DC power supply, 2 is a chopper circuit, and 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, 3
0 is a simmer circuit. The simmer circuit 30 mainly consists of a DC power supply 31. It consists of a diode 32° and a resistor 33. Now, in order to cause the lamp 5 to emit flash light, first a high voltage trigger pulse of 10 to 20 KV is applied to the lamp 5 by the trigger circuit 4 to start discharging. Immediately after that, the simmer circuit 30 is 100-150V. The lamp 5 is maintained in a discharged state by acting as a current source for the current. Next, by turning on the main switch circuit 6, the electric energy of the capacitor 3 charged to 300 to 900 μ is supplied to the lamp 5 as a current of several tens of OA by the DC power supply 1 and the chopper circuit 2. Turn this on. The high-energy light generated by this lighting irradiates a laser medium (not shown) and excites it to cause laser oscillation. In the above operation, in order for the lamp 5 to reliably enter the simmer mode by the trigger circuit 4, the output characteristics of the simmer circuit 30 are important; for example, when the trigger voltage is applied, the output characteristics are 4 to 15 times the simmer mode voltage. voltage is required. The solid line S1 in FIG. 4 indicates the characteristics of the simmer circuit 30, and the broken line L1
The double broken line L2 shows the characteristics of two different lamps, with current 1 on the horizontal axis and voltage E on the vertical axis. When lamp 5 in FIG. 5 has the characteristics shown by broken line L1, the lamp 5 is triggered. Since no simmer current flows before the simmer current is applied to the lamp 5, the voltage applied to the lamp 5 is equal to the voltage Eo of the DC type R31. When the lamp 5 is turned off after being turned on, the minimum current Is that can maintain the discharge state, which is determined by its internal impedance and the resistance 33, flows through the lamp 5, and the lamp enters the simmer mode. Note that the diode 32 prevents current from flowing into the simmer circuit 30 from the DC power supply 1 due to the operation of the main switch circuit 6.

[Problem to be solved by the invention]

The conventional simmer circuit 30 of FIG. 5 as described above has the following drawbacks. (1) When the lamp 5 has the characteristics shown by the double broken line L2 in FIG. 4, two simmer currents may exist depending on the relationship with the solid line S1 showing the characteristics of the simmer circuit 30, causing a problem. (2) Since a resistor is used, power loss is large and the efficiency is only about 25%. Furthermore, this is Figure 4.
This is a case of Eo-4Es, and as Eo becomes larger, the efficiency decreases. (3) For the reason mentioned above, the loss in the resistor is several hundreds of W, so a resistor with a large size is required, and therefore fan cooling may be required in some cases. (4) The DC power supply 31 needs to be isolated from other power supplies, and is generally boosted using a commercial power supply and a transformer, and then rectified and smoothed.
The weight increases. It is an object of the present invention to provide a simmer circuit which solves the problems of the conventional technology and improves efficiency, size, and weight.

[Means to solve the problem]

In order to solve this problem, the simmer circuit according to the present invention is a circuit that maintains a discharge state by flowing a predetermined current to a flash lamp when the flash lamp is not lit, and includes an inverter that obtains AC power from a DC power source for the flash lamp. and; A reactor and a transformer connected in series provided in the output stage of this inverter; A rectification/smoothing circuit provided on the secondary side of this transformer; The output voltage of this rectification/smoothing circuit and the voltage flowing through the reactor and transformer. and a control circuit that determines the frequency of the inverter based on the current.

[For use]

The alternating current generated in the reactor by the inverter changes to a value according to the winding ratio of the transformer, is transmitted to its secondary side, and is converted into smoothed direct current by a rectifier/smoothing circuit. At this time, if the on/off frequency of the inverter is kept constant, the impedance of the reactor will be constant,
It works almost the same as a resistor. Before entering simmer mode, the transformer is almost unloaded.
Since the exciting current only flows through the primary side, there is almost no voltage drop in the reactor, and half of the voltage of the DC power supply becomes a value corresponding to the turns ratio of the transformer, and the output terminal of the rectifier/smoothing circuit is output from. After transitioning to 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 corresponding to the winding ratio is connected in series with the reactor, so the output of the rectifier/smoothing circuit is A predetermined voltage and current are output from the end.

【Example】

An embodiment of a discharge power supply device including a simmer circuit according to the present invention will be described with reference to FIG. 1, which is a block diagram showing its configuration. In FIG. 1, the circuit is the same as the conventional example shown in FIG. 5 except for the simmer circuit 10 surrounded by a dashed line. The configuration of this simmer circuit 10 is as follows. The inverter arms of MOS-FETII, 12 connected in series, and the pair of capacitors 15 and 16 connected in series are each connected in parallel to the DC power supply 1, and each midpoint between the inverter arm and the pair of capacitors is A reactor 13, a current transformer 17, and a transformer 14 are connected in series. A capacitor 2 is connected to the secondary side of the transformer 14.
2, the rectifier circuit 1, and the smoothing circuit 19 are connected. A voltage detector 20 is provided at the output end of the smoothing circuit 19. The control circuit 21 controls the MO3-FET 11.1 based on signals from the current transformer 17 as a current detector related to the reactor 13 and the voltage detector 20 related to the output end of the smoothing circuit.
Controls the on/off frequency of 2. By frequency control of this control circuit 21, the simmer circuit 10 is connected to the solid line S2 in FIG.
It is possible to provide constant current characteristics such as
Even for a lamp having characteristics as indicated by the double broken line L2 (see FIG. 4), only one simmer current is obtained, and the disadvantages of the conventional example are eliminated. In FIG. 2, the voltage E moves toward the simmer mode following a trajectory like a broken line, and finally reaches the constant current characteristic S2. The function of capacitor 22 is that before lamp 5 is triggered,
In other words, the voltage applied to the lamp before the simmer current flows is slightly increased to make it easier to light the lamp.
Since the no-load voltage of the lamp varies to some extent, depending on the design conditions, the lamp may not turn on when replaced, and it is necessary to eliminate this possibility. In FIG. 3, the solid line S1 shows the characteristics of the simmer circuit without the capacitor 22, especially without frequency control, and the solid line S2 shows the characteristics of the simmer circuit with the capacitor 22 inserted, especially the simmer circuit without frequency control. By inserting the capacitor 22, it is possible to obtain a no-load voltage Ec that is slightly higher than the voltage EO of the DC power supply 1. [Effects of the Invention] Therefore, the present invention has the following superior effects compared to the conventional technology. (1) Since the loss of the inverter is smaller than the large loss due to resistance in the conventional example, the efficiency can be improved from about 25% of the conventional example to about 90%. (2) Since the commercial transformer and resistor required in the conventional example are not used, it is possible to reduce each of the external dimensions and weight by approximately 30%.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the 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. 4 is a characteristic diagram of this embodiment. Characteristic Diagram of Conventional Example FIG. 5 is a block diagram showing the configuration of a discharge power supply device including the conventional example. Symbol explanation 1: DC power supply, 2: Chopper circuit, 3: Capacitor, 4: Trigger circuit, 5: Lamp, 6: Main switch circuit, 10 Nijimer circuit, 11.12:
MOS-FET, +3: Reactor, 14 Nidorance, 15.16, 22: Capacitor, 17: Current transformer, 1
8: Rectifier circuit, 19: Smoothing circuit, 20: Voltage detector, 2
1: Control circuit. Ryo 3 figures and 4 figures

Claims (1)

[Scope of Claims] 1) In a circuit that maintains a discharge state by flowing a predetermined current to a flash lamp when the flash lamp is not lit, an inverter that obtains AC power from a DC power supply for the flash lamp; an output stage of the inverter; A reactor and a transformer connected in series are provided; a rectifier/smoothing circuit is provided on the secondary side of this transformer; A simmer circuit comprising: a control circuit that determines a frequency; 2) A simmer circuit according to claim 1, characterized in that the secondary side of the transformer includes a capacitor inserted in parallel.