JPH0847256A - Power circuit for laser - Google Patents

Abstract

(57) [Abstract] [Purpose] The current flowing through the primary side of a center-tap type single-phase full-wave rectifier circuit can be kept constant at all times to prevent power supply circuits and laser pumped lamps from falling into a continuous discharge state. Prevent damage. [Structure] A center tap type single-phase full-wave rectifier circuit is provided, and a first choke coil L2, a thyristor 1, a second choke coil L3, and a laser are provided on the secondary side of the center-tap type single-phase full-wave rectifier circuit. In the laser power supply circuit in which the excitation lamp 2 is connected in series and the first capacitor C2 is connected in parallel, the primary side of the center tap type single-phase full-wave rectifier circuit is connected in series to the power supply line. The third choke coil L1 and the second choke coil L1 connected in parallel.
And a resonance circuit including the capacitor C1. This resonant circuit keeps the current flowing in the primary side of the center tap type single-phase full-wave rectifier circuit constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser power supply circuit used for a pumping light source such as a pulse laser.

[0002]

2. Description of the Related Art FIG. 4 is a conventional laser power supply circuit, more specifically, a circuit diagram showing a schematic configuration of a power supply circuit for an excitation lamp of a YAG laser.

The conventional laser power supply circuit is
A center-tap type single-phase full-wave rectification circuit that changes the entire cycle into a current in the same direction by using two rectifying elements by means of a tapped transformer T10, and the secondary side of the center-tap type single-phase full-wave rectification circuit The choke coil L10, the thyristor 10 and the choke coil L11 are connected in series, and the capacitor C10 is connected in parallel. In this laser power supply circuit, the laser excitation lamp 11 is connected to the output stage of the circuit on the secondary side.

In the above laser power supply circuit, the choke coil L10 and the capacitor C10 are smoothing circuits.
The thyristor 10 has a very high resistance value in the off state and a low resistance value in the on state similar to the forward direction of the PN junction, and has a three-terminal structure having a gate terminal as a trigger electrode. Has become. This thyristor 1
0 means that a gate current is applied or a positive voltage is applied up to the breakdown voltage (breakover voltage).
The thyristor 10 changes from the off state to the on state. However, once the thyristor is in the on state, it cannot be returned to the off state except by making the applied voltage zero or making the current very small.

In the laser power supply circuit configured as described above, the power supply on the primary side of the center-tap type single-phase full-wave rectifier circuit depends on the preset charging time and discharging time of the capacitor C10. Sequence controlled. Charging / discharging of the capacitor C10 and discharging to the laser excitation lamp 11 are performed as follows.

Center tap type single-phase full-wave rectifier circuit 1
When power is supplied to the next side, the DC current rectified by the center tap type single-phase full-wave rectifier circuit flows into the capacitor C10 via the choke coil L10, and the capacitor C10 is charged. At this time, since the thyristor 10 is in the off state, the laser excitation lamp 11
No current flows to.

Center tap type single-phase full-wave rectifier circuit 1
When a predetermined time has passed since the power was supplied to the secondary side,
The power supply on the primary side of the center tap type single-phase full-wave rectifier circuit is turned off, and the charging of the above-mentioned capacitor C10 is completed. Then, a predetermined gate current flows through the thyristor 10, and the thyristor 10 is turned on. Thyristor 1
When 0 is turned on, the energy stored in the capacitor C10 is discharged to the laser excitation lamp 11 at once, and pumping light is emitted from the laser excitation lamp 11.

FIG. 5 is a waveform diagram of the discharge current discharged from the capacitor C10 to the laser excitation lamp 11. In this figure, the vertical axis represents the discharge current value and the horizontal axis represents the discharge time from when the thyristor 10 is in the on state to when it is in the off state. When the discharge in the capacitor C10 becomes almost zero (discharge At time t), the thyristor 10 is o
It is in the ff state.

The discharge to the laser excitation lamp 11 is finished when the discharge current becomes almost zero after the discharge time t and the thyristor 10 returns to the off state as shown in FIG. Then, after a lapse of a predetermined time from the power supply on the primary side of the center-tap type single-phase full-wave rectifier circuit, the power supply on the primary side of the center-tap type single-phase full-wave rectifier circuit is turned on again. turned on and capacitor C10
Will start charging.

As described above, in the conventional laser power supply circuit, by utilizing the change in the resistance value of the thyristor 10 in the on-off state, the capacitor C10 is charged / discharged and the laser excitation lamp 11 is discharged. ,
Pumping light is generated by the laser excitation lamp 11.

[0011]

FIG. 6 is a graph showing the charging current of the capacitor C2 in the laser power supply circuit shown in FIG. In FIG. 6, the vertical axis represents the charging current and the horizontal axis represents the charging time, and the charging current changes according to the change in the insulation resistance of the capacitor C10.

In the conventional laser power supply circuit described above, the current flowing through the primary side of the center-tap type single-phase full-wave rectifier circuit fluctuates in accordance with the change in impedance on the secondary side. When C10 is charged, the charging current changes according to the change in the apparent impedance of the capacitor C10 as shown in FIG.

In the conventional laser power supply circuit described above, the discharge time t shown in FIG. 5 fluctuates due to variations in charging energy due to temperature changes in the capacitor C10 and impedance variations due to temperature changes in the laser excitation lamp 11. Occurs. Therefore, the discharge current to the laser-excited lamp may not become zero even after a lapse of a predetermined time after the power supply on the primary side of the center tap type single-phase full-wave rectifier circuit is turned off. Power is supplied to the primary side of the center tap type single-phase full-wave rectifier circuit with the thyristor 10 in the on state (hereinafter, referred to as a continuous discharge state). Such a situation also occurs due to a malfunction of the sequence control in the power supply on the primary side of the center tap type single-phase full-wave rectifier circuit.

As described above, the conventional laser power supply circuit in which the current flowing through the primary side of the center tap type single-phase full-wave rectifier circuit fluctuates according to the change in impedance on the secondary side is continuous. When the discharge state occurs, a direct current corresponding to the change in the impedance on the secondary side is applied to the thyristor 10.
Since it will flow to the laser excitation lamp 11 via
There is a problem that the power supply circuit and the laser excitation lamp are damaged.

An object of the present invention is to keep the current flowing through the primary side of the single-phase full-wave rectifier circuit constant, thereby preventing damage to the power supply circuit and the laser excitation lamp in the continuous discharge state. It is to provide a power supply circuit for use.

[0016]

A laser power supply circuit of the present invention comprises a single-phase full-wave rectifier circuit, and supplies a direct current to a laser excitation lamp connected to the secondary side of the single-phase full-wave rectifier circuit. In the laser power supply circuit, a resonance circuit composed of a choke coil connected in series to the power supply line and a capacitor connected in parallel is provided on the primary side of the single-phase full-wave rectification circuit. Is the resonance condition ωL
= 1 / (ωc), and the current flowing through the primary side of the single-phase full-wave rectifier circuit is constant.

In this case, the single-phase full-wave rectifier circuit may be a center tap type single-phase full-wave rectifier circuit.

Further, the single-phase full-wave rectifier circuit may be a single-phase full-wave rectifier circuit in which four rectifying elements are connected in a bridge shape.

[0019]

In the conventional laser power supply circuit, the current flowing through the primary side of the single-phase full-wave rectifier circuit fluctuates according to the change in the impedance on the secondary side. A direct current corresponding to the change in impedance on the secondary side had flown to the laser excitation lamp 11.

In the laser power supply circuit of the present invention configured as described above, the resonant circuit provided on the primary side of the single-phase full-wave rectifier circuit causes the current flowing through the primary side to have the impedance Z on the secondary side. Is always constant irrespective of the change in the discharge current, so that even in the case of falling into the continuous discharge state, only a constant amount of current depending on the choke coil of the resonance circuit flows to the secondary side. Therefore, in the present invention, when a continuous discharge state occurs, a direct current corresponding to the change in impedance on the secondary side does not flow into the laser excitation lamp 11 and damage the power supply circuit or the laser excitation lamp.

[0021]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a schematic configuration of a laser power supply circuit according to the first embodiment of the present invention.

The laser power supply circuit of this embodiment is provided with a center-tap type single-phase full-wave rectification circuit that uses a rectifying element with two transformers T1 to change the entire cycle to a current in the same direction. A constant current circuit in which a current flowing through the primary side is made constant by providing a resonance circuit on the primary side of the center tap type single-phase full-wave rectifier circuit. The structure is as follows.

Center tap type single-phase full-wave rectifier circuit 1
The second side has a circuit configuration in which a choke coil L1 is inserted in series in the power supply line and a capacitor C1 is inserted in parallel. On the secondary side of the center tap type single-phase full-wave rectifier circuit, a choke coil L2, a thyristor and a choke coil L3 are connected in series, and a capacitor C1 is connected in parallel. In this laser power supply circuit, the laser excitation lamp 2 is inserted in the output stage of the circuit on the secondary side.

In the laser power source circuit, the choke coil L1 and the capacitor C1 form a resonance circuit. In this resonant circuit, as will be described later, the current flowing through the primary side of the center-tap type single-phase full-wave rectifier circuit becomes constant regardless of the change in the impedance on the secondary side. In addition,
The magnitude of the current flowing through the primary side of the center tap type single-phase full-wave rectifier circuit is determined by the choke coil L1 of the resonance circuit.
The size is set in advance so as not to damage the components of the power supply circuit, the laser excitation lamp, and the like.

Further, in the above laser power supply circuit, the power supply on the primary side of the center tap type single-phase full-wave rectifier circuit is sequence-controlled in accordance with the preset charging time and discharging time of the capacitor. There is.

Next, the operation of the laser power supply circuit of this embodiment will be described.

First, the formula of the constant current circuit in the laser power supply circuit of this embodiment will be described.

The impedance on the secondary side of the transformer T1 of this laser power supply circuit is

[0030]

[Outside 1] And the impedance seen from the primary side of the transformer T1

[0031]

[Outside 2] Then, the combined impedance seen from terminals a and b

[0032]

[Outside 3] Is

[0033]

[Equation 1] Given in.

The current flowing through the terminals a and b and the applied voltage are respectively

[0035]

[Outside 4] Then

[0036]

[Outside 5] Is

[0037]

[Equation 2] Therefore, the current I flowing through the primary side of the transformer T1 is given by the following equation.

[0038]

(Equation 3) Here, if a resonance condition of ωL = 1 / (ωc) is given, ω
^{Since 2} Lc = 1, the above equation 1 is

[0039]

[Equation 4] Becomes

That is, as can be seen from the above equation 2, in the laser power supply circuit of this embodiment, the current I flowing through the primary side of the transformer T1 is set to the secondary side by setting the above resonance condition in the resonance circuit. The constant current depends on the choke coil L1 of the resonance circuit, regardless of the impedance Z of.

As described above, in the laser power supply circuit of this embodiment, the current I flowing through the primary side of the transformer T1 becomes a constant current regardless of the impedance Z on the secondary side, charging of the capacitor C2 and laser excitation. The discharge to the lamp 2 is performed as follows.

Center tap type single-phase full-wave rectifier circuit 1
When power is supplied to the next side, the DC current rectified by the center tap type single-phase full-wave rectifier circuit flows into the capacitor C2 via the choke coil L2, and the capacitor C2 is charged. At this time, since the thyristor 1 is in the off state, no current flows into the laser excitation lamp 11.

FIG. 2 is a graph showing the charging current of the capacitor C2 in the laser power supply circuit shown in FIG.
In FIG. 2, the vertical axis represents the charging current, the horizontal axis represents the charging time, and the charging current is always constant from the start of charging to the end of charging.

When the capacitor C2 is charged, the current flowing to the primary side of the center tap type single-phase full-wave rectifier circuit by the resonance circuit is constant regardless of the change in the apparent impedance of the capacitor C2. As shown in FIG. 2, charging is always performed with a constant amount of charging current.

Center tap type single-phase full-wave rectifier circuit 1
When a predetermined time has passed since the power was supplied to the secondary side,
The power supply on the primary side of the center tap type single-phase full-wave rectifier circuit is turned off, and the charging of the above-mentioned capacitor C2 is completed. When charging of the capacitor C2 is completed, a predetermined gate current flows through the thyristor 1 to turn on the thyristor 1, the energy stored in the capacitor C2 is discharged to the laser excitation lamp 2 at once, and pumping light is emitted from the laser excitation lamp 2. Is emitted.

When the discharge current from the capacitor C2 to the laser excitation lamp becomes almost zero, the thyristor returns to the off state and the discharge to the laser excitation lamp 11 ends.
Then, after a lapse of a predetermined time from the power supply on the primary side of the center-tap single-phase full-wave rectifier circuit being turned off, the power supply on the primary side of the center-tap single-phase full-wave rectifier circuit is turned on again. Then, the charging of the capacitor C1 is started.

When the discharge current to the laser-excited lamp does not become zero within a predetermined time after the power supply on the primary side of the center tap type single-phase full-wave rectifier circuit is turned off. (That is, when the thyristor is not turned off), the laser power supply circuit described above also falls into the continuous discharge state as in the conventional laser power supply circuit.

When a continuous discharge state occurs, in the laser power supply circuit of this embodiment, the charging current shown in FIG. 2 is supplied to the laser excitation lamp 2 via the thyristor 1 and the choke coil L3.
Flows to. At this time, the current flowing through the primary side of the center-tap type single-phase full-wave rectifier circuit is constant regardless of the change in the impedance on the secondary side, and the magnitude of the current depends on the components of the power supply circuit or Since the size is set in advance so as not to damage the laser excitation lamp, etc., even if the impedance on the secondary side changes, the power supply circuit components, the laser excitation lamp, etc. may be damaged. Absent.

As described above, in the laser power supply circuit of this embodiment, the constant current circuit is formed by providing the resonance circuit on the primary side of the center tap type single-phase full-wave rectification circuit, and the continuous discharge state is achieved. It prevents damage to the power supply circuit and laser excitation lamp in the event of a fall.

Next, another embodiment of the present invention will be described.

FIG. 3 is a circuit diagram showing a schematic configuration of a laser power supply circuit according to the second embodiment of the present invention.

The laser power supply circuit of this embodiment is provided with a single-phase full-wave rectifier circuit in which four rectifying elements are connected in a bridge shape instead of the center tap type single-phase full-wave rectifier circuit. It has the same structure as the laser power supply circuit of the first embodiment. The same components as those of the laser power supply circuit of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

Also in the laser power supply circuit of this embodiment, like the laser power supply circuit of the first embodiment, the resonance circuit is set to a predetermined resonance condition to flow to the primary side of the full-wave rectification circuit. The current can be constant regardless of the apparent change in impedance on the secondary side of the full-wave rectifier circuit. Therefore, the charging current for the capacitor C2 provided on the secondary side of the full-wave rectifier circuit is also the first
As in the case of the laser power supply circuit of the above embodiment, it becomes as shown in FIG.

As described above, also in the laser power supply circuit of this embodiment, the resonance circuit is provided on the primary side of the center tap type single-phase full-wave rectification circuit, and the constant current circuit is formed by this resonance circuit. Therefore, similarly to the laser power supply circuit of the first embodiment, it is possible to prevent damage to the power supply circuit, the laser excitation lamp, and the like when the continuous discharge state occurs.

[0055]

Since the laser power supply circuit of the present invention is constructed as described above, it has the following effects.

(1) Due to the resonance circuit provided on the primary side of the single-phase full-wave rectifier circuit, the current flowing on the primary side is always constant regardless of the change in the impedance Z on the secondary side, so continuous discharge is performed. Even if it falls into a state, only a constant amount of current flows to the secondary side. Therefore, it is possible to prevent damage to the power supply circuit and the laser excitation lamp when the continuous discharge state occurs.

(2) Since it is possible to form a constant current circuit in which the magnitude of the current flowing on the primary side of the single-phase full-wave rectifier circuit depends on the choke coil L of the resonance circuit, there is an effect that the circuit design is simplified. .

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a laser power supply circuit according to a first embodiment of the present invention.

FIG. 2 is a graph showing a charging current of a capacitor C2 in the laser power supply circuit shown in FIG.

FIG. 3 is a circuit diagram showing a schematic configuration of a laser power supply circuit according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a schematic configuration of a conventional laser power supply circuit.

FIG. 5 shows a condenser C10 to a laser excitation lamp 11
It is a wave form diagram of the discharge current discharged to.

6 is a graph showing a charging current of a capacitor C2 in the laser power supply circuit shown in FIG.

[Explanation of symbols]

 1 Thyristor 2 Laser excitation lamp L1, L2, L3 Choke coil C1, C2 Capacitor T1 Transformer

Claims (3)

[Claims] 1. A laser power supply circuit comprising a single-phase full-wave rectification circuit, which supplies a direct current to a laser excitation lamp connected to the secondary side of the single-phase full-wave rectification circuit, A resonance circuit including a choke coil connected in series to a power line and a capacitor connected in parallel is provided on the primary side of the circuit, and the resonance circuit has a resonance condition of ωL = 1 / (ωc). The power supply circuit for laser is characterized in that the current flowing through the primary side of the single-phase full-wave rectification circuit is made constant. 2. The laser power supply circuit according to claim 1, wherein the single-phase full-wave rectifier circuit is a center tap type single-phase full-wave rectifier circuit. 3. The laser power supply circuit according to claim 1, wherein the single-phase full-wave rectifier circuit is a single-phase full-wave rectifier circuit in which four rectifying elements are connected in a bridge shape. Power supply circuit.