JP4013634B2 - Pulse power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pulse power supply device that combines a pulse generation circuit using a power semiconductor switch and a magnetic pulse compression circuit, and repeatedly generates a large current pulse with a narrow width. The present invention relates to an apparatus for suppressing wear and extending the life.
[0002]
[Prior art]
A pulse power supply device for driving an excimer laser or the like first charges a power capacitor to a predetermined voltage with a charger, and then fires a control switch in response to a trigger command to cause a current pulse from the capacitor to a load such as a laser electrode. Supply. For the control switch, a power semiconductor element such as GTO or IGBT is often used instead of the conventional thyratron. The reason for this is that thyratron has problems such as short life in high-repetition operation, occurrence of misfire, and time-consuming heating of the filament, which cannot be started instantly.
[0003]
On the other hand, in the case of a power semiconductor element, the withstand voltage and pulse current conduction capability of the element alone is inferior to one order of magnitude compared to a thyratron, so normally, boosting with a pulse transformer and magnetic pulse compression using a magnetic switch are used in combination. In many cases, the lack of capability of the element is compensated.
[0004]
FIG. 4 shows an example. The pulse generation circuit 1 initially charges the first stage capacitor C ₀ with the high-voltage charger 2 and supplies a pulse current from the capacitor C ₀ to the pulse transformer T ₂ by turning on the semiconductor switch Q ₁ . The saturable reactor T ₁ reduces the duty of the semiconductor switch Q1.
[0005]
Three-stage magnetic pulse compression circuits 3 _{1 to} 3 ₃ are cascaded on the secondary side of the pulse transformer T _{2. In} the first stage magnetic pulse compression circuit 3 ₁ , the capacitor C ₁ has a high voltage with the pulse current boosted by the pulse transformer PT. It is charged, and supplies the saturable reactor T ₃ at the charging voltage of the capacitor C ₁ is the magnetic pulse compression circuit 3 ₂ pulse current narrow that magnetic pulse compression the next stage by operating magnetic switches. Similarly, magnetic pulse compression with a pulse width is performed by the magnetic pulse compression circuits 3 ₂ and 3 ₃ by high voltage charging of the capacitors C ₂ and C ₃ and magnetic switch operation of the saturable reactors T ₄ and T ₅ .
[0006]
Pulse output of the magnetic pulse compression circuit 3 _3, when supplying a pulse current of narrow and high voltage to a load 4 such as a chamber of the laser head, the peaking capacitor C _P is charged to a predetermined voltage level, the capacitor C _P To a discharge electrode (laser electrode) LH.
[0007]
Each of the saturable reactors T ₁ , T ₃ , T ₄ , and T ₅ is provided with a magnetic reset winding, and a DC bias current is supplied from the magnetic reset circuit 5 to these windings, so that the iron core of the pulse transformer T ₂ is provided. After saturation of the magnetic saturation prevention and saturable reactors T _{3 to} T ₅ , they are saturated to the opposite polarity.
[0008]
Thus, the pulse power supply converts the energy of the voltage and pulse width laser requires a combination of pulse compression circuit according to the step-up circuit and the magnetic switch by pulse transformer T _2, are injected into the laser electrodes .
[0009]
Here, it is said that the main cause of the consumption of the laser electrode is abnormal discharge. In particular, when a voltage having a polarity opposite to that at the time of oscillation is applied to the laser electrode after the laser oscillates, the value is only about 300V. It is said that even if it is an order of magnitude lower than 20-40 kV at the time of oscillation, it is affected.
[0010]
For this reason, for example, Japanese Patent Application Laid-Open No. 11-251675 proposes a method for suppressing the appearance of reverse polarity voltage on the laser electrode. In this method, in order to achieve both the suppression of the laser reverse polarity voltage (here, it is positive because of the negative voltage pulse during laser oscillation) and the time until the magnetization is initialized by the pulse transformer T _2. In addition, as shown in FIG. 4, a circuit in which a resistor or a Zener diode is combined is provided as the diode clamp circuit 6.
[0011]
[Problems to be solved by the invention]
As also described in JP-A 11-251675 JP above, in order to have the initialization of the pulse transformer T ₂ in a short time, it is necessary to increase the clamping voltage of the clamping circuit 6, the high clamping The voltage becomes a residual voltage which is not preferable for the lifetime of the laser electrode.
[0012]
Currently, excimer lasers for use as light sources in lithography apparatuses are required to have a higher repetition frequency for improving productivity. In the proposal period of the above-mentioned Japanese Patent Application Laid-Open No. 11-251675, the pulse repetition frequency was 1 kHz, but now it is going to shift to 4 kHz via 2 kHz. Furthermore, 6-8 kHz is being started at the research and development level.
[0013]
When such high repetition operation is required, the time required for the initialization of the magnetization of the pulse transformer T ₂ is required to be further shortened. The clamp circuit system of JP-A-11-251675 discloses as a result, life of the pulse transformer T Fast Initialization of ₂ and the electrode life balance is difficult.
[0014]
Therefore, as an example of the countermeasure, as shown in FIG. 5, the magnetization state of the pulse transformer T ₂ is reset instead of reducing the clamp voltage by eliminating the resistor or the constant voltage diode in the clamp circuit 6 in the circuit of FIG. as you can hold the voltage needed to a method of interposed reset diode circuit D _L between the connection portion between the one and the capacitor C ₁ of the secondary winding of the pulse transformer T ₂ are considered.
[0015]
A high level pulse current flows through the diode circuit D _L as the load is transferred from the capacitor C _{0 to} C ₁ when a pulse is generated. Further, when the charge is completely transferred to the capacitor C ₁ (the polarity is negative with respect to the ground), a voltage of 20 to 40 kV is applied. This voltage gradually decreases when the load shift from the capacitor C _{1 to} C ₂ starts, and becomes 0 voltage when the load shifts completely to C ₂ .
[0016]
However, diode circuit D _L, since it is a short high voltage 20~40kV is applied, requires a series connection of a number of diodes, yet unlike diode clamp circuit 6, the individual diodes above As described above, when a load is transferred from the capacitor C _{0 to} C ₁ , a large current of several hundred to 3000 A peak flows in a few microseconds, so that a large current carrying capacity is required. Moreover, disadvantageous although not shown, because they require a snubber circuit consisting of a capacitor in order to take a voltage division resistor for each diode, the diode circuit D _L requires a very large space as a whole, in cost It is inferior in practicality.
[0017]
An object of the present invention is to provide a pulse power supply device capable of shortening the initialization time of a pulse transformer for high repetitive operation and extending the life of a laser electrode.
[0018]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention extends the life of the laser electrode by lowering the clamp voltage of the clamp circuit that suppresses the voltage appearing in the reverse polarity after the discharge to the laser electrode. In holding the voltage necessary to reset the magnetization state of the pulse transformer by inserting a reset diode circuit between the secondary winding and the capacitor of the magnetic pulse compression circuit,
By providing a resistor in parallel with the reset diode circuit, the voltage applied to the diode of the reset diode circuit is less than the reverse breakdown voltage of one series of reset diodes even though the capacitor of the magnetic pulse compression circuit has a high charging voltage. Furthermore, a tertiary winding is provided in the pulse transformer, and a diode for regenerating reflected energy from the capacitor of the magnetic pulse compression circuit in the capacitor of the pulse generation circuit in the initial charging direction is provided in the tertiary winding, At the timing when reflected energy returns, the semiconductor switch of the pulse generation circuit is turned off to prevent reverse voltage from being applied to the reset diode circuit through the pulse transformer. And
[0019]
(1) A pulse generation circuit that generates a pulse current through a pulse transformer from a capacitor that is initially charged by turning on a semiconductor switch, and the capacitor is charged with a pulse current that is obtained on the secondary side of the pulse transformer. A magnetic pulse compression circuit that applies a discharge current, which is magnetic pulse compressed from the capacitor in a switch operation, to the laser electrode, and a voltage that is provided in parallel with the laser electrode and that appears in the laser electrode after discharge at the laser electrode is suppressed. A diode clamping circuit, and a reset diode provided between a secondary winding of the pulse transformer and a capacitor of the magnetic pulse compression circuit and holding a voltage necessary for resetting the magnetization state of the pulse transformer In a pulse power supply device comprising a circuit,
The diode clamp circuit is configured to have a low clamp voltage capable of suppressing abnormal discharge of the laser electrode with a voltage appearing in the laser electrode with a reverse polarity after discharge at the laser electrode ,
The reset diode circuit is provided with a resistor in parallel with one series of reset diodes, and the resistor has a resistance value that makes a voltage applied from a capacitor of the magnetic pulse compression circuit equal to or lower than a reverse breakdown voltage of the reset diode. And a configuration with
The pulse transformer is provided with a tertiary winding, and the tertiary winding is provided with a diode for regenerating the reflected energy from the capacitor of the magnetic pulse compression circuit in the capacitor of the pulse generation circuit in the initial charging direction, and It is characterized in that the semiconductor switch of the pulse generation circuit is turned off at the timing when the reflected energy returns .
[0022]
In addition, the present invention prevents the reverse voltage from being applied to the reset diode circuit by the reflected voltage due to the load open by providing a reactor in parallel with the diode clamp circuit in the above configuration. It is characterized by.
[0023]
(2) A reactor is provided in parallel with the diode clamp circuit, and the reactor has an impedance value that reverses the polarity of the reflected voltage generated when the load of the magnetic pulse compression circuit is opened .
[0024]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
FIG. 1 is a circuit diagram showing an embodiment of the present invention. Portions figure differs from FIG. 5, instead of the reset diode circuit D _L, a certain series of diodes Dx, in that a reset diode circuit 7 constituted by a parallel connected resistor Rx thereto. The pulse transformer T ₂ is provided with a tertiary winding, and the tertiary winding is provided with a diode D _RC for regenerating the reflected energy from the capacitor C ₁ in the capacitor C ₀ in the initial charging direction. It is said.
[0025]
In the configuration of the diode circuit 7 in this embodiment, the reason why one diode having a general withstand voltage of 1200 to 2500 V may be connected in series will be described below.
[0026]
As described above, the reverse voltage is applied to the diode Dx after the voltage transition from the capacitor C ₀ to C ₁ is completed when the pulse is generated, and then the saturable reactor T ₃ is saturated and the capacitor C ₁ to C ₂ is saturated. This is the time until the voltage transition ends. This time is usually 1 μsec or less although it depends on the design of the pulse compression circuit.
[0027]
An equivalent circuit at this timing is shown in FIG. Here, ideally, the on-resistance of the switch Q ₁ is 0, and the residual voltage of the capacitor C ₀ is also 0. Here, the exciting inductances of the saturable reactor T ₁ and the pulse transformer T ₂ are values when the core is non-saturated. Therefore, the numerical values are generally high. When actually measured, they are 33 mH and 6 mH, respectively. there were. Here, when the angular frequency with the half period of 1 μs is calculated, it becomes 3.14 MHz, and the excitation impedances of T1 and T2 correspond to 104 kΩ and 18 kΩ, respectively. Therefore, if the resistor Rx is connected in parallel with the diode Dx and the resistor Rx is 300 Ω, the reverse voltage applied to the diode is 40 kV × 300 / (104 kΩ and 18 kΩ in parallel impedance) even if the peak value of the voltage of the capacitor C ₁ is 40 kV. ) = 780V, and it can be seen that one diode of 1200V class is sufficient for the withstand voltage of the diode Dx.
[0028]
Next, the processing method of the energy reflected by the load is different between FIG. 5 and FIG. 1, and the reason will be described. The reflected energy from the load shifts from the capacitor C ₃ → C ₂ → C ₁ , but the polarity of the voltage of each capacitor is opposite to that when supplying energy to the load. That is, in FIGS. 5 and 1, the voltage sequentially shifts in the positive polarity direction at the portion opposite to the ground potential. Here, in the case of FIG. 5, since Q1 is kept in the on state, the reflected C ₁ voltage returns the secondary (high voltage) winding → primary (low voltage) winding of the pulse transformer T _2. through and transferred to the capacitors C ₀ in a loop of the saturable reactor T ₁ → capacitor C ₁ → C _0.
[0029]
That is, the polarity of the capacitor C ₀ voltage is opposite to that of the initial state. When an IGBT is used for the semiconductor switch Q ₁ , the pulse transformer T ₂ is used after the saturable reactor T ₁ is saturated in the upward direction (the pulse transformer T ₂ side) through the antiparallel diode built in the IGBT module. The voltage boosted via the windings is applied to the diode Dx. The capacitor C ₀ voltage that is reflected and charged to the opposite polarity is attenuated by a fraction of the initial positive charge voltage, but the original voltage is still 40 kV on the high-voltage side. 1 is a voltage of several kV, and in one series of diodes Dx having a voltage of 1200 V, they are completely damaged due to overvoltage resistance.
[0030]
In order to prevent this reverse voltage application, a blocking diode may be inserted in series with the semiconductor switch Q _1. However, since a large current flows when a pulse is generated, the loss increases by this element, and the efficiency of the power supply Is not a preferable means.
[0031]
Therefore, in this embodiment, the pulse transformer T ₂ to provide a third winding, and at the timing when the reflected energy returns, keep the off state of the semiconductor switch Q _1. As a result, the voltage of the capacitor C ₁ that has been reflected back returns to the tertiary winding (a positive voltage is induced downward) through the pulse transformer T ₂ → the current flows in the loop of the capacitor C ₀ → diode D _RC. The reflected energy returns to the capacitor C ₀ . The polarity at this time is the same as the initial state. Since the voltage of the regenerated capacitor C ₀ is blocked by the low-voltage side diode D _RC , it is not applied to the winding of the pulse transformer T ₂ , and therefore is not applied to the diode Dx, and the withstand voltage of Dx As a result, one series of 1200V class is sufficient.
[0032]
(Embodiment 2)
FIG. 3 shows an embodiment of the present invention. In FIG. 1, in the event that the load is opened due to a work error or the like, the reflected energy shifts from capacitor C _{3 to} C _{2 to} C ₁ without reversing the voltage polarity. Since the iron core of the pulse transformer T ₂ is already excited with the voltage at the time of pulse generation, the iron core is likely to be saturated when the reflected voltage is applied with the same polarity. If saturation occurs, the excitation impedance of the pulse transformer T ₂ drops sharply, and most of the reflected voltage of the capacitor C ₁ is applied to the diode Dx. To do.
[0033]
In order to prevent this, in this embodiment, a reactor Lp is provided in parallel with the diode clamp circuit 6 so that the polarity of the reflected voltage is always reversed even when the load is open.
[0034]
The impedance value of the reactor Lp, without energy of the capacitor C ₃ is shunted to reactor Lp when the load 4 is connected to the normal, has a minimum value of only migrating to the peaking capacitor Cp, and the load At the time of opening, the saturable reactor T ₄ is saturated in the reverse direction before the voltage of the capacitor C ₃ is inverted by the reactor Lp, and is set to a value that does not return to the capacitor C ₂ .
[0035]
【The invention's effect】
As described above, according to the present invention, the reset diode circuit for shortening the initialization time of the pulse transformer for the high repetitive operation of the apparatus and for reducing the voltage after the discharge of the laser electrode has its reverse breakdown voltage lowered. It is possible to reduce the size and cost. Specifically, the following effects are obtained.
[0036]
(1) Since the resistor is provided in parallel with the reset diode circuit, the diode of the reset diode circuit can have a low reverse breakdown voltage such as one series even though the capacitor of the magnetic pulse compression circuit has a high charging voltage.
[0037]
(2) A tertiary winding is provided in the pulse transformer, and a diode for regenerating reflected energy from the capacitor of the magnetic pulse compression circuit in the capacitor of the pulse generation circuit in the initial charging direction is provided in the tertiary winding, and Since the semiconductor switch of the pulse generation circuit is turned off at the timing when the reflected energy returns, it is possible to prevent a reverse voltage from being applied to the reset diode circuit through the pulse transformer.
[0038]
(3) By providing the reactor in parallel with the diode clamp circuit, it is possible to prevent the reverse voltage from being applied to the reset diode circuit due to the reflected energy due to the open load.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a pulse power supply device showing Embodiment 1 of the present invention.
FIG. 2 is an equivalent circuit diagram of a reset clamp circuit portion in the embodiment.
FIG. 3 is a circuit diagram of a pulse power supply device showing Embodiment 2 of the present invention.
FIG. 4 is a circuit example of a conventional pulse power supply device (part 1).
FIG. 5 is a circuit example of a conventional pulse power supply device (part 2).
[Explanation of symbols]
1 ... pulse generating circuit 2 ... high voltage charger 3 _1, 3 _2, 3 ₃ ... magnetic pulse compression circuit 4 ... load 5 ... magnetic reset circuit 6 ... diode clamp circuit 7 ... reset diode circuit Q1 ... semiconductor switches T _1, T ₃ , T ₄ , T ₅ ... saturable reactor T ₂ ... pulse transformer Rx ... resistors Dx, D _RC ... diode Lp ... reactor

Claims (2)

A pulse generation circuit that generates a pulse current through a pulse transformer by turning on a semiconductor switch from a capacitor that is initially charged, and the capacitor is charged by a pulse current obtained on the secondary side of the pulse transformer, and a magnetic switch operation of a saturable reactor. A magnetic pulse compression circuit that applies a discharge current magnetically compressed from the capacitor to a laser electrode; and a diode clamp that is provided in parallel with the laser electrode and suppresses a voltage appearing in a reverse polarity after the discharge at the laser electrode. A reset diode circuit that is provided between the circuit and the secondary winding of the pulse transformer and the capacitor of the magnetic pulse compression circuit and holds a voltage necessary for resetting the magnetization state of the pulse transformer. In the provided pulse power supply device,
The diode clamp circuit is configured to have a low clamp voltage capable of suppressing abnormal discharge of the laser electrode with a voltage appearing in the laser electrode with a reverse polarity after discharge at the laser electrode ,
The reset diode circuit is provided with a resistor in parallel with one series of reset diodes, and the resistor has a resistance value that makes a voltage applied from a capacitor of the magnetic pulse compression circuit equal to or lower than a reverse breakdown voltage of the reset diode. And a configuration with
The pulse transformer is provided with a tertiary winding, and the tertiary winding is provided with a diode for regenerating the reflected energy from the capacitor of the magnetic pulse compression circuit in the capacitor of the pulse generation circuit in the initial charging direction, and A pulse power supply device characterized in that the semiconductor switch of the pulse generation circuit is turned off at the timing when the reflected energy returns . 2. The pulse power supply device according to claim 1 , wherein a reactor is provided in parallel with the diode clamp circuit, and the reactor has an impedance value that reverses a polarity of a reflected voltage generated when a load of the magnetic pulse compression circuit is opened. .

Images