High-frequency power supplies, laser devices

Abstract

To provide a power supply device that can enhance the operation frequency of a load which operates intermittently.SOLUTION: A high frequency power source 200A comprises: a full-bridge circuit 210; a transformer T1; and a filter 220A. A primary winding W1 of the transformer T1 is connected to the full-bridge circuit 210. The filter 220A includes at least series inductor and is arranged between the full-bridge circuit 210 and the load such that an impedance Z when the load is seen from the full-bridge circuit 210 is inductive at a switching frequency Fsw, a three-dimentional harmonic wave 3Fsw, and a fifth harmonic wave 5Fsw.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a high-frequency power supply.

Background Art

[0002] As an industrial processing tool, laser processing devices are widely used. FIG. 1 is a block diagram of a laser processing device 1r. The laser processing device 1r includes a laser light source 2 such as a CO2 laser, and a laser driving device 4r that supplies AC power to the laser light source 2 and excites it. The laser driving device 4r includes a DC power supply 6 and a high-frequency power supply 8. The DC power supply 6 is a constant voltage source, and its output DC voltage V is stabilized to a target value by feedback control using PID (Proportional-Integral-Differential) control or PI control. DC is stabilized to the target value.

[0003] The high-frequency power supply 8 receives the DC voltage V DC and converts the DC power into a desired high-frequency power. The AC power is supplied to the laser light source 2 which is the load.

[0004] FIG. 2 is an equivalent circuit diagram of the high-frequency power supply 8 and the laser light source 2. The high-frequency power supply 8 includes a full-bridge circuit (H-bridge circuit) 20 and a transformer T1. The full-bridge circuit 20 includes a leg including a high-side transistor MH1 and a low-side transistor ML1, and a leg including a high-side transistor MH2 and a low-side transistor ML2. The primary winding of the transformer T1 is connected to the full-bridge circuit 20.

[0005] The laser light source 2 includes a laser resonator 24 and inductors L1, L2. The laser resonator 24 includes a pair of opposing discharge electrodes, and the pair of discharge electrodes forms a capacitance. Inductors L1, L2 are inserted between the secondary winding of the transformer T1 and the laser resonator 24. By the inductors L1, L2, the resonance frequency of the load 22 is adjusted to match the switching frequency of the high-frequency power supply 8.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 1997-129953 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The inventors of the present invention have investigated the high-frequency power supply 8 and laser light source 2 shown in Figure 2 and have come to recognize the following problems.

[0008] Figure 3 is the equivalent circuit diagram of the full-bridge circuit 20 of Figure 2. Figure 3 shows one leg including the high-side transistor MH1 and the low-side transistor ML1. A high voltage is applied to the gate of the high-side transistor MH1, making it ON, and a low voltage is applied to the gate of the low-side transistor ML1, making it OFF. In this state, the output voltage Vout of the full-bridge circuit 20 is high (Vcc), and the drain current Ids of the high-side transistor MH1 is supplied to the load 22.

[0009] As described above, the resonant frequency of the load 22 is designed to match the switching frequency of the high-frequency power supply 8. However, the transformer T1 and wiring contain parasitic capacitance, and due to the influence of this parasitic capacitance, the impedance of the load 22 may become capacitive. When the load impedance is capacitive, the displacement current (time-varying component) di / dt, i.e., the AC component, flowing through the high-side transistor MH1 increases.

[0010] The high-side transistor MH1 and the low-side transistor ML1 have parasitic capacitances between the gate and source, and between the gate and drain. The time-varying component of the current Ids charges the gate capacitance of the low-side transistor ML1 via its gate-drain capacitance Cgd. As a result, the gate-source voltage Vgs of the low-side transistor ML1 rises, and when it exceeds the threshold voltage, the low-side transistor ML1 turns on (this is called gate misfiring). As a result, the high-side transistor MH1 and the low-side transistor ML1 turn on simultaneously, and a through-current flows. In particular, in applications requiring high capacity and high-frequency switching, such as laser power supplies, SiC devices capable of high-speed operation are used as power transistors in inverters. When SiC devices are switched in the MHz band, gate misfiring may occur depending on parameters such as the gate-drain parasitic capacitance Cgd.

[0011] Figure 4 is an operating waveform diagram of the full-bridge circuit 20 of Figure 2. The upper part of Figure 4 shows the output voltage Vout, and the lower part shows the gate voltage Vgs of the low-side transistor ML1. From time t0 to t1 is the low-output period, when the high-side transistor MH1 is off and the low-side transistor ML1 is on. During the low-output period, the gate voltage Vgs of the low-side transistor ML1 is a high voltage.

[0012] At time t1, the device transitions from the low-output period to the high-output period. During the high-output period, the high-side transistor MH1 is on and the low-side transistor ML1 is off. At time t1, a low (0V) gate voltage Vgs is applied to the gate of the low-side transistor ML1. At time t2, if a gate misfire occurs, the gate voltage Vgs oscillates. If the gate voltage Vgs exceeds the allowable voltage (withstand voltage) of the negative gate of the transistor, it will negatively affect the reliability of the transistor. In particular, SiC devices have a low withstand voltage on the negative side, so it is necessary to suppress the application of negative voltage.

[0013] This disclosure is made in the present circumstances, and one exemplary objective of a certain aspect thereof is to provide a high-frequency power supply capable of suppressing false firing of transistors. [Means for solving the problem]

[0014] A high-frequency power supply in one aspect of the present disclosure comprises a full-bridge circuit, a transformer whose primary winding is connected to the full-bridge circuit, and a filter circuit positioned between the full-bridge circuit and the load, including at least a series inductor, such that the impedance seen from the full-bridge circuit to the load is inductive at the switching frequency and the third and fifth harmonics.

[0015] Furthermore, any combination of the above components, or in which components or expressions are mutually substituted among methods, apparatus, systems, etc., are also valid embodiments of the present invention. [Effects of the Invention]

[0016] According to one aspect of this disclosure, misfires of transistors can be suppressed. [Brief explanation of the drawing]

[0017] [Figure 1] This is a block diagram of a laser processing machine. [Figure 2] This is an equivalent circuit diagram of a high-frequency power supply and a laser light source. [Figure 3] Figure 2 is the equivalent circuit diagram of the inverter. [Figure 4] Figure 2 shows the operating waveform of the inverter. [Figure 5] This is a block diagram of the laser device according to Embodiment 1. [Figure 6] Figures 6(a) to 6(d) are circuit diagrams showing example filter configurations. [Figure 7] This is a Smith chart showing the impedance Zin as seen from a full-bridge circuit over a load. [Figure 8] This is a block diagram of the laser device according to Embodiment 2. [Figure 9] Figs. 9(a) to 9(d) are circuit diagrams showing configuration examples of the filter. [Figure 10] There is a diagram showing a laser processing apparatus including a laser device.

Embodiments for Carrying Out the Invention

[0018] The outline of some exemplary embodiments of the present disclosure will be described. This outline is for the purpose of providing a basic understanding of the embodiments as a prelude to the detailed description to follow, and simplifies and describes some concepts of one or more embodiments. It does not limit the scope of the invention or the disclosure. This outline is not an all-inclusive outline of all possible embodiments, and is not intended to identify important elements of all embodiments or to draw lines around the scope of some or all aspects. For convenience, "one embodiment" may be used to refer to one embodiment (example or modification) or a plurality of embodiments (examples or modifications) disclosed in this specification.

[0019] A high-frequency power supply according to one embodiment includes a full-bridge circuit, a transformer whose primary winding is connected to the full-bridge circuit, and a filter circuit including at least a series inductor, which is arranged between the full-bridge circuit and a load such that the impedance seen from the full-bridge circuit to the load is inductive at the switching frequency and the third and fifth harmonics.

[0020] According to this configuration, since the load impedance of the full-bridge circuit is inductive at the fundamental wave and harmonic frequencies, the time differential component of the drain current of the high-side transistor is suppressed. Thereby, charging of the gate capacitance through the gate-drain capacitance of the low-side transistor can be suppressed, and gate false arcing of the low-side transistor can be prevented.

[0021] In one embodiment, the filter circuit may be provided between the secondary winding of the transformer and the load.

[0022] In one embodiment, the filter circuit may be provided between the full-bridge circuit and the primary winding of the transformer.

[0023] In one embodiment, the filter circuit may be an LC filter.

[0024] In one embodiment, the filter circuit may be a T-type filter.

[0025] In one embodiment, the filter circuit may be a π-type filter.

[0026] In one embodiment, the filter circuit may include only a series inductor.

[0027] In one embodiment, the load may include a laser resonator.

[0028] In one embodiment, the full-bridge circuit may be composed of SiC transistors.

[0029] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Furthermore, the embodiments are illustrative and not limiting to the disclosure and invention, and not all features or combinations thereof described in the embodiments are necessarily essential to the disclosure and invention.

[0030] In this specification, "member A connected to member B" includes not only cases where member A and member B are directly connected physically, but also cases where member A and member B are indirectly connected via other members that do not substantially affect their electrical connection or impair the functions or effects produced by their combination.

[0031] Similarly, "the state in which member C is connected (provided) between member A and member B" includes not only cases where member A and member C, or member B and member C, are directly connected, but also cases where they are indirectly connected via other members that do not substantially affect their electrical connection state or impair the function or effect produced by their combination.

[0032] In this specification, the symbols attached to electrical signals such as voltage signals and current signals, or to circuit elements such as resistors, capacitors, and inductors, shall represent the respective voltage values, current values, or circuit constants (resistance values, capacitance values, and inductance) as needed.

[0033] Figure 5 is a block diagram of a laser device 100A according to Embodiment 1. The laser device 100A comprises a laser light source 110 and a high-frequency power supply 200A. The laser light source 110 is, for example, a CO2 laser and includes a laser resonator 112 and inductors L1 and L2. The inductances of inductors L1 and L2 are adjusted so that the impedance of the laser light source 110, including inductors L1 and L2 and the laser resonator 112, is a real number at the switching frequency Fsw of the high-frequency power supply 200A. In other words, the resonant frequency f0 of the laser light source 110 matches the switching frequency Fsw of the high-frequency power supply 200A.

[0034] A DC voltage Vdc is supplied to the high-frequency power supply 200A from a power supply circuit (not shown). The output of the high-frequency power supply 200A is connected to the laser light source 110. The high-frequency power supply 200A intermittently supplies an AC drive voltage to the laser light source 110 in response to the excitation signal. That is, the high-frequency power supply 200A is active during the period when the excitation signal instructs excitation (for example, high), and supplies the AC drive voltage Vdc to the laser light source 110. DRV The high-frequency power supply 200A is inactive during the period when the excitation signal instructs it to stop (e.g., low), and the power supply to the laser light source 110 is stopped. The switching frequency Fsw of the high-frequency power supply 200A is 1MHz or higher. The output power of the high-frequency power supply 200A is 1kW or higher.

[0035] The 200A high-frequency power supply includes a full-bridge circuit 210, a transformer T1, and a filter 220A.

[0036] The full-bridge circuit 210 includes high-side transistors MH1 and MH2, and low-side transistors ML1 and ML2. These transistors MH1, MH2, ML1, and ML2 can be made of SiC, which enables high-speed switching. The transformer T1 includes a primary winding W1 and a secondary winding W2. The primary winding W1 is connected to the full-bridge circuit 210.

[0037] Filter 220A is connected between the secondary winding W2 of transformer T1 and the laser light source 110. Filter 220A includes at least a series inductor. The circuit configuration and circuit constants of filter 220A are designed such that the impedance Zin, viewed from the full-bridge circuit 210 towards the load 114, is inductive at the switching frequency Fsw and the third harmonic 3Fsw and fifth harmonic 5Fsw.

[0038] Figures 6(a) to 6(d) are circuit diagrams showing example configurations of filter 220A. As mentioned above, filter 220 includes a series inductor L3. Filter 220A in Figure 6(a) is an LC filter and includes a shunt capacitor C3 in addition to the series inductor L3. Filter 220A in Figure 6(b) is a π-type filter and includes two shunt capacitors C3 and C4 in addition to the series inductor L3. Filter 220A in Figure 6(c) is a T-type filter and includes two series inductors L3 and L4 and a shunt capacitor C3. Filter 220A in Figure 6(d) includes only the series inductor L3.

[0039] In Figures 6(a) to (d), filter 220A is connected in series with inductor L1 in Figure 5, but it may also be connected in series with inductor L2. Alternatively, the filters 220A in Figures 6(a) to (d) may be connected in series with inductors L1 and L2, respectively.

[0040] The above describes the configuration of the laser device 100A.

[0041] Figure 7 is a Smith chart showing the impedance Zin as seen from the full-bridge circuit 210 to the load 114 side. At all switching frequencies Fsw (fundamental, 3rd harmonic 3Fsw, and 5th harmonic 5Fsw), the imaginary part of the impedance Zin is positive, i.e., it is inductive.

[0042] The operation of the high-frequency power supply 200A is explained below. Because the impedance viewed from the full-bridge circuit 210 towards the load 114 becomes inductive, it operates in current-lag mode, enabling soft switching. This reduces the time-varying component dIds / dt of the drain current Ids of the high-side transistor MH1. As a result, charging of the gate capacitance of the low-side transistor ML via the gate-drain capacitance Cgd of the low-side transistor ML1 is suppressed, thereby preventing an increase in the gate voltage Vgs. This suppresses misfiring of the gate of the low-side transistor ML1.

[0043] By suppressing gate misfires of the low-side transistor ML1, through-current can be prevented. Furthermore, oscillations in the gate voltage Vgs caused by gate misfires can be suppressed, which in turn prevents the gate-source voltage from exceeding the breakdown voltage, thereby improving reliability.

[0044] Figure 8 is a block diagram of the laser device 100B according to Embodiment 2. The laser device 100B comprises a laser light source 110 and a high-frequency power supply 200B.

[0045] Filter 220B is inserted between the full-bridge circuit 210 and the primary winding W1 of transformer T1. The rest of the configuration is the same as in Figure 5.

[0046] Figures 9(a) to 9(d) are circuit diagrams showing example configurations of filter 220B. The filters 220B in Figures 9(a) to 9(c) are LC type, π type, and T type, respectively. While the filter 220A in Figures 6(a) to 6(c) was configured to ground, the shunt capacitor of the filter 220B in Figures 9(a) to 9(c) is connected in a floating manner.

[0047] The same effects as in Embodiment 1 can be obtained with the high-frequency power supply 200B according to Embodiment 2.

[0048] (Application) Next, the applications of the laser device 100 will be explained. Figure 10 shows a laser processing apparatus 300 equipped with the laser device 100. The laser processing apparatus 300 irradiates the object 302 with laser pulses 304 to process the object 302. The type of object 302 is not particularly limited, and the types of processing are exemplified by drilling and cutting, but are not limited to these.

[0049] The laser processing apparatus 300 comprises a laser device 100, an optical system 310, a control device 320, and a stage 330. The object 302 is placed on the stage 330 and fixed as necessary. The stage 330 positions the object 302 according to the position control signal S2 from the control device 320 and scans the relative positions of the object 302 and the laser pulse 304. The stage 330 may be 1-axis, 2-axis (XY), or 3-axis (XYZ).

[0050] The laser device 100 oscillates in response to a trigger signal (excitation signal) S1 from the control device 320, generating a laser pulse 306. The optical system 310 irradiates the target object 302 with the laser pulse 306. The configuration of the optical system 310 is not particularly limited and may include a group of mirrors to guide the beam to the target object 302, lenses and apertures for beam shaping, etc.

[0051] The control device 320 comprehensively controls the laser processing device 300. Specifically, the control device 320 intermittently outputs a trigger signal S1 to the laser device 100. The control device 320 also generates a position control signal S2 to control the stage 330 according to the data (recipe) describing the processing.

[0052] The present invention has been described above based on several embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing steps, and that such modifications also fall within the scope of the present invention. Such modifications will be described below.

[0053] (Variation 1) In the high-frequency power supply 200A shown in Figure 5, the filter 220A and inductors L1 and L2 may be configured as a single unit.

[0054] (Modification 2) The applications of the high-frequency power supply 200 are not limited to laser devices. For example, a full-bridge circuit operating at a switching frequency of 1 MHz or higher (Fsw) can be used in ion implantation devices and other applications.

[0055] (Variation 3) In this embodiment, the full-bridge circuit 210 is made of SiC, but it is not limited to that and may be made of other power transistors.

[0056] The embodiments only illustrate one aspect of the principle and application of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, without departing from the spirit of the present invention as defined in the claims. [Explanation of Symbols]

[0057] 100 laser devices 200 High frequency power supply 210 Full-bridge circuit 220 NN T1 Transformer W1 Primary winding W2 Secondary winding MH High-Side Transistor ML Low-Side Transistor 110 Laser light source 112 Laser resonators 114 load

Claims

1. A high-frequency power supply that supplies an AC voltage to a laser light source, Full bridge circuit and A transformer whose primary winding is connected to the full-bridge circuit, A filter circuit comprising at least a series inductor and positioned between the full bridge circuit and the laser light source, Equipped with, The aforementioned laser light source is A laser resonator including a pair of discharge electrodes that form capacitance, Two inductors are connected to one and the other of the discharge electrodes to adjust the resonant frequency, Includes, When the aforementioned filter circuit is not provided, the impedance seen from the full-bridge circuit towards the laser light source is capacitive. A high-frequency power supply characterized in that the circuit configuration and circuit constants of the filter circuit are designed such that the impedance seen from the full-bridge circuit to the laser light source side is inductive at the switching frequency and the third and fifth harmonics.

2. The high-frequency power supply according to claim 1, characterized in that the filter circuit is provided between the secondary winding of the transformer and the laser light source.

3. The high-frequency power supply according to claim 1, characterized in that the filter circuit is provided between the full-bridge circuit and the primary winding of the transformer.

4. The high-frequency power supply according to any one of claims 1 to 3, characterized in that the filter circuit is an LC filter.

5. The high-frequency power supply according to any one of claims 1 to 3, characterized in that the filter circuit is a T-type filter.

6. The high-frequency power supply according to any one of claims 1 to 3, characterized in that the filter circuit is a π-type filter.

7. The high-frequency power supply according to any one of claims 1 to 3, characterized in that the filter circuit includes only the series inductor.

8. The high-frequency power supply according to any one of claims 1 to 7, characterized in that the full-bridge circuit is composed of SiC transistors.

9. A laser light source and A high-frequency power supply according to any one of claims 1 to 8 that supplies an AC voltage to the laser light source, A laser device characterized by being equipped with the following features.

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