JP6331480B2 - Inverter device and plasma generator - Google Patents

Description

  The present invention relates to an inverter device that switches an input voltage, passes an exciting current through an exciting winding on a primary side of a step-up transformer, and outputs an AC voltage from an output winding on a secondary side, and a plasma generator using the inverter device .

An inverter device is used to supply an alternating high voltage to various discharge devices such as a discharge tube for a large plasma display and a plasma generator.
For example, atmospheric pressure plasma is applied as one means of surface treatment to improve the value of various industrial products such as surface modification of a material to be treated and removal of contaminants. When adhesion, printing, coating, or the like is applied to a resin or the like, pretreatment with atmospheric pressure plasma improves wettability, which can be easily and reliably performed.

A high voltage is required to generate the atmospheric pressure plasma. As a power supply device therefor, there is a device that generates a high voltage by boosting a direct current obtained by full-wave rectification and smoothing of an alternating current from a commercial power supply, or a voltage in which a pulsating current is superimposed on a direct current component.
In order to obtain a required output voltage Vout from the input voltage Vin, a step-up ratio n of several tens to several hundreds is required.

In order to realize this, there is an N-fold rectifier circuit such as a Cockcroft-Walton circuit. However, since this circuit is performed by charging and discharging with a capacitor, an instantaneous single-shot output can be extracted, but it is difficult to continuously extract output power.
Therefore, in order to obtain a stable high voltage output, in general, the input voltage is switched and an exciting current is intermittently passed through the primary exciting winding of the transformer to generate an alternating high voltage on the secondary output winding. An inverter device is used.
However, in order to obtain a high voltage with a high step-up ratio as described above, a large transformer having a large turn ratio between the excitation winding and the output winding must be used.

A general definition for determining a transformer is expressed as follows. That is, the number of turns Np of the excitation winding, the current Ip flowing through the excitation winding, and the number of turns Nout of the output winding are obtained by the following equations.
Np = Vin ・ Ton / Ae ・ B
Ip = Nout / Iout / Np
Nout = Vout ・ Np ・ Ton / Vin
Where Ton: duty ratio (sec) Ae: effective area of the core (cm ² )
B: Magnetic flux density (gauss) Vin: Input voltage (V)
Vout: Output voltage (V) Iout: Output current (A)

  As can be seen from these definitions, the number of turns Np of the excitation winding is restricted by the relationship with the magnetic flux density B of the transformer or the effective cross-sectional area Ae, which is inversely proportional. It is necessary that the number Np of excitation windings be as small a positive integer as possible. However, if the number of turns is small, the magnetic flux density B of the core is increased, the loss is increased, the magnetic saturation is advanced, and the function as a transformer is lost. On the other hand, if the number of turns is too large, the winding length increases, and the loss due to the current flowing therethrough increases.

  From the BH curve of the ferrite core shown in FIG. 11, the magnetic flux density B of the core changes substantially in proportion to the magnetic field strength H only in a specific range indicated by ΔB, and the magnetic field strength H is indicated by ΔH. When the range is exceeded, magnetic saturation occurs. Therefore, it functions as a transformer only in this range. In the BH curve, the area (hatched portion) of the portion surrounded by the path when the magnetic field strength H increases and decreases is generally referred to as hysteresis loss (iron loss).

For this reason, the number of turns Np of the exciting winding is limited to a specific range, and the output that can be drawn from the transformer depends on the balance between the number of turns Np of the exciting winding and the magnetic flux density B of the core. Is limited to a specific range.
If the magnetic flux density B can be taken out sufficiently and sufficiently, the transformer characteristics do not deteriorate. However, in reality, the core material (for example, ferrite 0.2 to 0.3 tesla, silicon steel plate 1 tesla: there is amorphous 1 tesla, permalloy, etc. depending on the frequency to be used), the magnetic flux is insufficient.

In order to solve such a problem, the present inventor has previously proposed a high-voltage inverter device described in Patent Document 1.
As shown in FIG. 12, the high-voltage inverter device has separate cores with completely different magnetic paths, and constitutes a step-up transformer by a plurality of transformers T1 and T2 having the same characteristics.
Then, the input voltage Vin is switched by the switching element Qsw which is controlled to be turned on / off by the control circuit IC, and the exciting windings Np1 and Np2 of the transformers T1 and T2 are simultaneously excited by exciting current. The output windings Nout and Nout (sub) of the plurality of transformers T1 and T2 are connected in series to output the output voltage Vout at both ends from the output terminal OUT.

FIG. 13 is a timing chart showing voltage and current waveforms of each part generated when the switching element Qsw is periodically turned on and off.
Here, Vgs is the drive voltage (gate-source voltage) of the switching element Qsw, VNp1 and VNp2 are the voltages of the excitation windings Np1 and Np2, and Ids is the current flowing between the drain and source of the switching element Qsw, that is, the excitation winding. A combined current Vds of exciting currents flowing through Np1 and Np2 is a drain-source voltage of the switching element Qsw.
When the switching element Qsw is turned off, an output voltage VNout is generated in the output winding Nout of the transformer T1, and an output voltage VNout (sub) is generated in the output winding Nout (sub) of the transformer T2. Are in sync. An output voltage Vout on which the two voltage waveforms are superimposed is output from the output terminal OUT.

  In this way, an excitation current is simultaneously supplied to the excitation windings Np1 and Np2 of the plurality of transformers T1 and T2, and the voltages generated in the output windings Nout and Nout (sub) at the time of turn-off are accumulated and boosted. Accordingly, no bias magnetism occurs in the excitation winding of each transformer, and the number of turns of the output winding can be increased as a whole transformer, so that a high voltage with a high boost ratio can be obtained continuously, stably and safely. be able to.

However, in this high voltage inverter device, the alternating output voltage is mainly in the positive direction.
The period during which the switching element Qsw is ON, that is, the period in which the excitation current is simultaneously applied to the excitation windings Np1 and Np2 of each transformer is a period in which excitation energy is stored in each transformer, and no output voltage is generated.
For this reason, it is necessary to obtain a sufficiently large amount of electric power at a high voltage such as a peak value of 10 kV or higher, which is necessary when continuously generating an atmospheric pressure plasma discharge for performing surface modification treatment stably. Had the problem of being difficult.

  The present invention has been made to solve the above-described problems, so that high-voltage and high-energy power can be efficiently obtained without increasing the size of the inverter device and without causing a shortage of the magnetic flux density of the transformer. The purpose is to do.

  In order to achieve the above object, the inverter device according to the present invention switches the input voltage to flow an exciting current through the exciting winding on the primary side of the step-up transformer, and generates an AC voltage from the output winding on the secondary side of the step-up transformer. In the inverter device for output, the step-up transformer is constituted by a first transformer group and a second transformer group, and each of the first and second transformer groups includes a plurality of individual transformers having the same number and the same characteristics. The excitation windings of the plurality of transformers are connected in parallel to be excited simultaneously.

The output windings of the plurality of transformers of the first and second transformer groups are all connected in series or in parallel, and the output windings of the transformer groups connected in series or in parallel to each other. The midpoints connecting the one ends to each other are grounded, and the other ends are individually connected to a pair of output terminals that output an output voltage to the load, and the transformers of the first and second transformer groups are connected in series or Switch elements are connected between both ends of the output windings connected in parallel .
Furthermore, the control flow of the first exciting current only to the first transformer group of each transformer excitation windings, control flow of the second exciting current only to the transformer magnetizing winding of the second transformer group And a switching control means for repeatedly performing the switching at a predetermined cycle, and each output winding of the first transformer group and each output winding of the second transformer group with respect to the middle point. alternately Ru to generate voltages of opposite polarity Te.
At that time, the switching control means turns on the switch element connected between both ends of the output winding of the first transformer group during the period in which the first excitation current flows, and the second excitation current is supplied to the switching element. During the flow period, the switch element connected between both ends of the output winding of the second transformer group is turned on.

  According to the present invention, it is possible to efficiently obtain high-power electric power at a high voltage without increasing the size of the inverter device and without causing a shortage of the magnetic flux density of the transformer.

1 is a circuit diagram of a first embodiment of an inverter device according to the present invention. FIG. It is a figure which shows the structural example in case the load 2 in FIG. 1 is a discharge part which generate | occur | produces a plasma discharge. It is a wave form diagram of two switching signals Sp1 and Sp2 which the control circuit 15 in FIG. 1 outputs. FIG. 3 is a waveform diagram showing an example of voltages + Vout and −Vout generated by first and second transformer groups of the inverter device of FIG. 1 and an output voltage Vout voltage waveform generated by them. It is a wave form diagram which simplifies and compares the output voltage waveform of the conventional inverter apparatus and the inverter apparatus by this invention. It is a circuit diagram of 2nd Embodiment of the inverter apparatus by this invention. It is a circuit diagram of 3rd Embodiment of the inverter apparatus by this invention. It is a circuit diagram of 4th Embodiment of the inverter apparatus by this invention. It is a circuit diagram of 5th Embodiment of the inverter apparatus by this invention. It is a circuit diagram of 6th Embodiment of the inverter apparatus by this invention. It is a diagram which shows the example of the BH curve of the core of a common transformer. It is a circuit diagram which shows the structural example of the high voltage inverter apparatus proposed previously. FIG. 13 is a timing chart showing changes in voltage waveforms at various parts during operation of the high-voltage inverter device shown in FIG. 12.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
[First Embodiment]
First, a first embodiment of an inverter device according to the present invention will be described in detail, but it is almost common to other embodiments.
FIG. 1 is a circuit diagram showing the configuration of the inverter device of the first embodiment. This inverter device 1 switches the input voltage Vin input between the input terminals 11a and 11b, passes an exciting current through the exciting winding on the primary side of the step-up transformer 10, and outputs the secondary side of the step-up transformer 10 This is an inverter device that outputs an AC voltage from a winding.

The step-up transformer 10 is composed of a first transformer group 10A and a second transformer group 10B, and each of the first and second transformer groups 10A, 10B has the same number of identical characteristics. A plurality of transformers T1, T2 and T3, T4 are used.
The excitation windings Np1 and Np2 of the plurality of transformers T1 and T2 of the first transformer group 10A are connected in parallel, and the transformers T1 and T2 are excited simultaneously by flowing the first excitation current ia. . Further, the excitation windings Np3 and Np4 of the plurality of transformers T3 and T4 of the second transformer group 10B are also connected in parallel so that the second excitation current ib flows in the direction opposite to the first excitation current ia. The transformers T3 and T4 are excited simultaneously.

On the other hand, the output windings Ns1 and Ns2 and Ns3 and Ns4 of the plurality of transformers T1, T2 and T3, T4 of the first and second transformer groups 10A and 10B are connected in series. In each of the transformer groups 10A and 10B, the middle point m, which connects the adjacent ends of the series circuit of the output windings Ns1 and Ns2 and the series circuit of the output windings Ns3 and Ns4, is connected to the ground GND and grounded. Then, an end point a which is the other end of the series circuit of the output windings Ns1 and Ns2 of the first transformer group 10A is connected to the output terminal 12a, and the series of the output windings Ns3 and Ns4 of the second transformer group 10B . The end point b which is the other end is connected to the output terminal 12b. The output terminals 12 a and 12 b are a pair of output terminals that output an output voltage to the load 2.

In this case, one output terminal 12a is a negative output terminal that outputs a negative output voltage -Vout with respect to the middle point m connected to the ground GND. The other output terminal 12b is also a positive output terminal that outputs a positive output voltage + Vout with respect to the middle point m.
The voltage between the one output terminal 12a and the other output terminal 12b is output to the load 2 as the output voltage Vout.

When the inverter device 1 is a power supply unit of a plasma generator, the load 2 is a discharge unit having a discharge electrode 21 and a counter electrode 22 as shown in FIG. 2, for example, and has a load capacity Co. Plasma discharge is generated by applying an output voltage Vout between the discharge electrode 21 and the counter electrode 22. The current that flows when the load 2 is connected to the output terminals 12a and 12b is indicated by Io in FIG.
The discharge part (load 2) shown in FIG. 2 is interposed between a plurality (15 in the illustrated example) of discharge electrodes 21, a counter electrode 22 opposed thereto, and the discharge electrode 21 and the counter electrode 22. It is comprised with the dielectric material 23. FIG.

  In this example, the discharge electrode 21 is formed in a round bar shape around a metal wire 21a having good conductivity such as copper or aluminum and covered with a dielectric (insulator) 21b. A plurality of discharge electrodes 21 are arranged in a plane parallel to the facing surface 22a of the flat counter electrode 22 so that the outer peripheries of the electrodes adjacent to each other in the left-right direction in FIG. It is arranged extending in various directions. The diameter (φ) of each discharge electrode 21 is, for example, about 8 mm. The metal wires 21a of the discharge electrodes 21 are connected so as to be electrically connected to each other.

The counter electrode 22 is a flat electrode made of a metal having good conductivity such as copper or aluminum, and also serves as a heat sink. A dielectric 23 such as a silicon-based sheet is attached to a surface 22 a of the counter electrode 22 facing the discharge electrode 21. In FIG. 2, a gap is provided between the counter electrode 22 and the dielectric 23 for easy understanding, but in actuality, the counter electrode 22 and the dielectric 23 are in close contact by adhesion or the like.
Although the gap is also shown between the discharge electrode 21 and the dielectric 23, in practice, it is sufficient if there is a gap that allows a sheet material such as printing paper to be surface-modified to pass through.

The output voltage Vout having an effective value of 6 KV or more is output from the output terminals 12a and 12b of the inverter device 1 between the discharge electrodes 21 and the counter electrode 22 of the discharge unit which is the load 2 configured as described above. 25 applied.
Accordingly, a dielectric barrier discharge is generated in the atmospheric pressure between each discharge electrode 21 and the counter electrode 22 by a creeping discharge or silent discharge, which is a kind of atmospheric pressure plasma discharge, or a combined discharge of creeping discharge and silent discharge. Can be made. Even if the voltage applied between the discharge electrode 21 and the counter electrode 22 is reversed between positive and negative, there is almost no difference in the effect.

A radical generated on the surface of the discharge portion (load 2) by the dielectric barrier discharge described above by transporting and passing the sheet material along the dielectric 23 as indicated by the dashed-dotted arrow F. The reforming proceeds by touching active species such as ions and ions.
It progresses by the fact that groups such as various hydrophilic functional groups formed by the components in the air and the components contained in the sheet material itself are formed on the surface of the sheet material by plasma and the surface energy is increased. To do.

For example, when an ultraviolet curable varnish is coated on a printed matter on which resin toner is printed by an electrophotographic image forming apparatus, the varnish of the resin toner printing portion is repelled by the wax component contained in the resin toner. There is. However, when surface treatment with atmospheric pressure plasma is performed, wettability is improved, so that uniform varnish coating is possible and the added value of the printed matter is improved.
However, the structure of the discharge part of the plasma generator according to the present invention is not limited to the above-described structure, and various modifications can be made. Further, the present invention can be applied to an apparatus that generates plasma by corona discharge or an apparatus that generates plasma discharge in a low-pressure atmosphere in which some gas is contained.

  By the way, in the inverter device 1 shown in FIG. 1, the excitation windings Np1 and Np2 of the transformers T1 and T2 of the first transformer group 10A are connected in parallel between the input terminals 11a and 11b to which the input voltage Vin is input. The switching element Q1 is connected in series to the circuit. Similarly, between the input terminals 11a and 11b, a switching element Q2 is connected in series to a circuit in which the excitation windings Np3 and Np4 of the transformers T3 and T4 of the second transformer group 10B are connected in parallel.

Therefore, the first switching element Q1 is provided in series with the path through which the first excitation current ia flows by the input voltage Vin in the excitation windings Np1 and Np2 of the transformers T1 and T2 of the first transformer group 10A. Further, a second switching element Q2 is provided in series with the path through which the second excitation current ib flows by the input voltage Vin in the excitation windings Np3 and Np4 of the transformers T3 and T4 of the second transformer group 10B.
Rectangular switching signals Sp1 and Sp2 output from the control circuit 15 are applied to the gates of the switching elements Q1 and Q2, respectively, so that the switching elements Q1 and Q2 are alternately turned on and off.
The two switching elements Q1, Q2 and the control circuit 15 constitute a switching control means.

The switching control means controls the first excitation current ia to flow only through the excitation windings Np1, Np2 of the transformers T1, T2 of the first transformer group 10A for a predetermined period, and the transformers T3 of the second transformer group 10B. , T4, and the control of flowing the second excitation current ib only through the excitation windings Np3 and Np4 for a predetermined period are repeated at a predetermined cycle.
Therefore, during the period in which the first excitation current ia flows through the excitation windings Np1 and Np2 of the transformers T1 and T2 of the first transformer group 10A, the excitation windings of the transformers T3 and T4 of the second transformer group 10B. The second excitation current ib does not flow through Np3 and Np4 .
The excitation windings of the transformers T3 and T4 of the second transformer group 10B are passed during a period in which the first excitation current ia does not flow through the excitation windings Np1 and Np2 of the transformers T1 and T2 of the first transformer group 10A. A second excitation current ib is passed through Np3 and Np4 in the opposite direction to the first excitation current ia.

During the period in which the first excitation current ia is flowing through the excitation windings Np1 and Np2 of the transformers T1 and T2 of the first transformer group 10A, electromagnetic energy is accumulated in the transformers T1 and T2. Then, during the period when the excitation current ia is turned off, a high voltage is induced in each output winding Ns1, Ns2 by resonance due to the inductance, stray capacitance, and load capacitance Co.
Electromagnetic energy is accumulated in each of the transformers T3 and T4 during the period in which the second excitation current ib is flowing through the excitation windings Np3 and Np4 of the transformers T3 and T4 of the second transformer group 10B. Then, during the period when the excitation current ib is turned off, a high voltage is induced in each output winding Ns3, Ns4 by resonance due to the inductance, stray capacitance, and load capacitance Co.

In this case, the time axes of the output voltage waveforms generated in the output windings of the plurality of transformers T1 and T2 and T3 and T4 in the first and second transformer groups 10A and 10B are synchronized. desirable.
The switching elements Q1 and Q2 use MOS field effect transistors (MOSFETs) in this embodiment, but may use insulated gate bipolar transistors (IGBTs) or the like.
The control circuit 15 includes an oscillating circuit that operates by the input voltage Vin and generates two switching signals Sp1 and Sp2 for controlling on / off of the switching elements Q1 and Q2.

As shown in FIG. 3, the two switching signals Sp1 and Sp2 are rectangular wave pulses having the same period T, but the periods tq1 and tq2 during which they become high level are equal and the phase is shifted by more than ½ period. ing. That is,
tq1 = tq2 ≦ 0.5T
These conditions are essential. If it deviates from this condition, the balance of the energy stored in the excitation inductance is lost, and it deviates from resonance. In addition, the positive and negative output voltages are different.

The switching element Q1 is turned on during the period tq1 when the switching signal Sp1 is at a high level, and the first excitation current ia flows through the excitation windings Np1, Np2 of the transformers T1, T2 of the first transformer group 10A.
The switching element Q2 is turned on during the period tq2 when the switching signal Sp2 is at a high level, and the second excitation current ib flows through the excitation windings Np3 and Np4 of the transformers T3 and T4 of the second transformer group 10B.

  Then, the switching element Q1 is turned off, and the output windings Ns1, Ns2 are supplied to the output windings Ns1, Ns2 during a period in which the first excitation current ia does not flow through the excitation windings Np1, Np2 of the transformers T1, T2 of the first transformer group 10A. A negative output voltage is generated with respect to the midpoint m. Similarly, when the switching element Q2 is turned off and the second excitation current ib does not flow through the excitation windings Np3 and Np4 of the transformers T3 and T4 of the second transformer group 10B, the output windings Ns3 and Ns4 A positive output voltage is generated with respect to the midpoint m.

That is, the middle point m grounded to the output windings Ns1, Ns2 of the transformers T1, T2 of the first transformer group 10A and the output windings Ns3, Ns4 of the transformers T3, T4 of the second transformer group 10B. Are alternately generated with voltages of opposite polarity.
The relationship between the winding start and winding direction of each excitation winding and output winding in each transformer T1, T2 of the first transformer group 10A and each transformer T3, T4 of the second transformer group 10B, and the direction in which the excitation current flows As a result, the voltage generated in each output winding has the same polarity with respect to the midpoint m, and the opposite polarity.

  In this embodiment, the directions of the first excitation current ia flowing through the excitation windings Np1 and Np2 and the second excitation current ib flowing through the excitation windings Np3 and Np4 are reversed. As a result, each transformer is set so that the voltage generated in the output windings Ns1 and Ns2 has a negative polarity with respect to the midpoint m, and the voltage generated in the output windings Ns3 and Ns4 has a positive polarity with respect to the midpoint m. The winding direction of the excitation winding and the output winding is set.

Here, when tq1 and tq2 in FIG. 3 are tq1 = tq2 = 0.45T, the output voltage −Vout of the first transformer group 10A, the output voltage + Vout of the second transformer group 10B, and the output terminals 12a, The voltage waveform of the output voltage Vout between 12b is shown in FIG. (B) shows the output voltage -Vout (broken line waveform) of the first transformer group 10A and the output voltage + Vout (solid line waveform) of the second transformer group 10B . (A) is between the output terminals 12a and 12b. The waveform of the output voltage Vout is shown.
The output voltage Vout has a waveform in which the waveforms of the output voltages −Vout and + Vout of the transformer groups 10A and 10B are superimposed. Therefore, the transformers groups 10A, be an output voltage -Vout and + Vout waveform close to the pulsating flow of the half-wave of each order of negative or peak value was biased toward the positive -8KV or + 8KV of 10B, the output voltage between the output terminals Vout is a substantially continuous AC waveform having a peak value of about ± 12 KV .

FIG. 5 is a waveform diagram for simplifying and comparing the output voltage waveforms of the conventional inverter device and the inverter device according to the present invention.
(A) shows the example of a waveform of the output voltage Vout by the inverter apparatus described in patent document 1 demonstrated by FIG.12 and FIG.13. In this case, in the switching cycle T (frequency f) of the switching element Qsw, the primary-side ON time of all the transformers, that is, the time for passing the excitation current is a period in which excitation energy is stored in the transformer, and no output voltage is generated. .
Therefore, a positive output voltage (+ Vpeak) is generated only during the primary side OFF time of all transformers. Therefore, the ratio of the time when there is no output voltage within one cycle increases, and it is difficult to obtain sufficient power.

  (B) shows a waveform example of the output voltage Vout by the inverter device shown in FIG. Also in this case, the first exciting current ia is applied to the exciting windings Np1, Np2 of the transformers T1, T2 during the primary side ON time tq1 of the first transformer group 10A in the switching period T of the switching elements Q1, Q2. Shed. During that period, no output voltage is generated in the output windings Ns1, Ns2 of the transformers T1, T2. However, during that period, the exciting currents of the transformers T3 and T4 of the second transformer group 10B are turned off, so that the output windings Ns3 and Ns4 have a positive output voltage on the end point b side with respect to the middle point m ( + Vpeak) occurs.

Further, during the primary side ON time tq2 of the second transformer group 10B, the second exciting current ib is supplied to the exciting windings Np3 and Np4 of the transformers T3 and T4. During that period, no output voltage is generated in the output windings Ns3 and Ns4 of the transformers T3 and T4. However, since the exciting currents of the transformers T1 and T2 of the first transformer group 10A are turned off during that period, the output windings Ns1 and Ns2 have a negative output voltage on the end point a side with respect to the middle point m ( -Vpeak) occurs.
Accordingly, the ratio of the time when there is no output voltage within one cycle is extremely small, and the output power supplied to the load is proportional to the area of the halftone dot portion of the alternating waveform shown in FIG. According to the inverter device, double and positive power can be obtained.

  In the embodiment shown in FIG. 1, the polarity of one of the transformers T1 and T2 of the first transformer group 10A and the transformers T3 and T4 of the second transformer group 10B is reversed, or the transformers T1, T2 and T3 , T4 may be alternately supplied with exciting currents in the same direction. In that case, it is possible to obtain an output voltage waveform such as a full-wave rectified waveform only on the positive side or only on the negative side as shown in FIG. 5C.

  In the embodiment of FIG. 1, the step-up transformer 10 is configured by first and second transformer groups 10A and 10B each composed of two transformers, and outputs positive and negative voltage waveforms as in the push-pull method. Like to do. Therefore, the number of turns Ns of the output winding of each transformer is ½. This can solve the problems of insufficient magnetic flux density and a large window frame area for winding the output winding.

The number of transformers in each transformer group is not limited to two and may be two or more. However, the number of transformers in each transformer group needs to be the same. Therefore, the number of transformers constituting the step-up transformer 10 is an even number of four or more, such as four, six, and eight.
When the number of the transformers is n, the output inductance Ls of the step-up transformer 10 is obtained by the following equation.
Ls = AL · (Ns / 2) · (Ns / 2) · n (H)
Here, AL is an induction coefficient of each transformer, AL = μ · Ae / L,
μ is the magnetic permeability of the core, L is the magnetic path length, and Ae is the effective area.

And when n = 4 as in the embodiment described above,
Ls = AL / Ns / Ns (H)
Thus, it becomes the same value as the output inductance Ls of the step-up transformer when obtaining an output voltage having a positive or negative voltage waveform.
When the exciting current of each transformer group is turned off, the output inductance Ls and the combined capacitance of the capacitance Cs and the load capacitance Co distributed or parasitic between the output windings of the transformer group. Parallel resonance occurs on the secondary side. As a result, an output voltage (+ −Vout) alternated with a high voltage is output between the output terminals.
The same applies to other embodiments described below.

[Second Embodiment]
FIG. 6 shows a second embodiment of the inverter device according to the present invention.
In the circuit diagrams of FIGS. 6 to 10 showing the following embodiments, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and only different points will be described. Although there is a difference between the inverter device and the step-up transformer of each embodiment, for convenience, the inverter device 1 and the step-up transformer 10 are all used.

  The inverter device 1 of the second embodiment shown in FIG. 6 is different from the first embodiment shown in FIG. 1 in that the output windings Ns1 and Ns2 of the transformers T1 and T2 of the first transformer group 10A, The only difference is that the output windings Ns3 and Ns4 of the transformers T3 and T4 of the second transformer group 10B are connected in parallel to each other.

In this case, the inverter device 1 of the second embodiment has a peak value of the negative output voltage −Vout by the first transformer group 10A and the second transformer group 10B as compared with the inverter device 1 of the first embodiment. The peak value of the positive output voltage + Vout due to becomes small. Therefore, the effective value of the alternating output voltage Vout is about ½, but the value of the load current Io is about twice, so that the output power is the same.

Therefore, when a large current is required even with the same power, the output windings of a plurality of transformers constituting each transformer group may be connected in parallel to each other.
In the other embodiments, as in this embodiment, the output windings Ns1 and Ns2 of the transformers T1 and T2 constituting the first and second transformer groups 10A and 10B and the transformers T3 and T4 The output windings Ns3 and Ns4 may be connected in parallel to each other.

[Third Embodiment]
A third embodiment of the inverter device according to the present invention is shown in FIG.
In the inverter device 1 of the third embodiment, the output windings Ns1 to Ns4 of the transformers T1 to T4 of the first and second transformer groups 10A and 10B are all connected in series, and the middle point m is connected to the ground GND. The end point a connected to the output terminal 12a is connected to the ground GND.

The first excitation current ia and the second excitation current ib flowing through the excitation windings Np1 to Np4 of the transformers T1 to T4 of the first and second transformer groups 10A and 10B are converted into the first embodiment shown in FIG. Control in the same way as the form. As a result, in the series circuit of the output windings Ns1 and Ns2 of the transformers T1 and T2 in the first transformer group 10A, a voltage having a positive peak waveform is generated on the middle point m side with respect to the end point a on the ground side. In the series circuit of the output windings Ns3 and Ns4 of the transformers T3 and T4 in the second transformer group 10B, a voltage having a positive peak waveform that is shifted from the middle point m toward the end point b by ½ period is generated.

Therefore, as shown in FIG. 5C, the voltage of the positive peak waveform by the first transformer group 10A and the voltage of the positive peak waveform by the second transformer group 10B within one switching period T. Occur in about 1/2 cycle. Therefore, the output voltage Vout between the output terminals 12a and 12b becomes a pulsating voltage waveform such as a positive full-wave rectified waveform. As a result, a load current Io flows in the direction of the arrow in FIG.
In this case, the amplitude of the output voltage Vout is ½ compared to the alternating voltage waveform having positive and negative peaks shown in FIG. 5B according to the first embodiment, but in FIG. The output power proportional to the area of the halftone dot portion of the waveform shown is equivalent to that in the first embodiment.

The first exciting current ia and the second exciting current ib are passed in the direction opposite to the direction shown in FIG. 7, or the exciting windings Np1 to Np4 or the output windings Ns1 to Ns4 of the transformers T1 to T4 are wound. If the direction is reversed, the polarity of the output voltage Vout can be made negative.
In that case, in the series circuit of the output windings Ns1 and Ns2 of the transformers T1 and T2 in the first transformer group 10A, a voltage having a negative peak waveform is generated on the middle point m side with respect to the end point a on the ground side. . In the series circuit of the output windings Ns3 and Ns4 of the transformers T3 and T4 in the second transformer group 10B, a voltage having a negative peak waveform that is shifted by 1/2 cycle toward the end point b with respect to the middle point m is generated.

Therefore, the negative peak waveform voltage generated by the first transformer group 10A and the second transformer group 10B within one cycle T of switching as if the waveform shown in FIG. 5C is inverted to the negative side. Thus, a negative peak waveform voltage due to is generated about every half cycle. Therefore, the output voltage Vout between the output terminals 12a and 12b has a pulsating voltage waveform such as a negative full-wave rectified waveform, and the load current Io flows in the direction opposite to that shown in FIG.
Alternatively, even if the end point b on the output terminal 12b side is connected to the ground instead of the end point a on the output terminal 12a side in FIG. 7, the output voltage Vout is like a negative full-wave rectified waveform as described above. It becomes a pulsating voltage waveform.

[Fourth Embodiment]
A fourth embodiment of the inverter device according to the present invention is shown in FIG.
As shown in FIG. 8, the inverter device 1 according to the fourth embodiment changes the direction of the first excitation current ia flowing through the excitation windings Np1 and Np2 of the transformers T1 and T2 of the first transformer group 10A . The direction is opposite to that in the previous embodiments. Therefore, the direction of the first excitation current ia is the same as the second excitation current ib flowing through the excitation windings Np3 and Np4 of the transformers T3 and T4 of the second transformer group 10B.
Similarly to the third embodiment described above, the output windings Ns1 to Ns4 of the transformers T1 to T4 of the first and second transformer groups 10A and 10B are all connected in series, and the middle point m is grounded. The end point a connected to the output terminal 12a is connected to the ground GND without being connected to the GND.

As a result, during the period when the first exciting current ia is OFF, the series circuit of the output windings Ns1 and Ns2 of the transformers T1 and T2 of the first transformer group 10A is centered with respect to the end point a on the ground GND side. A negative peak waveform voltage is generated on the point m side. Further, during the period in which the second excitation current ib is OFF, the series of output windings Ns3 and Ns4 of the transformers T3 and T4 of the second transformer group 10B is set to 1 on the end b side with respect to the middle point m. / Voltage with a positive peak waveform shifted by two cycles is generated.
In this case, the relationship between the winding start and the winding direction of the excitation winding and the output winding in each of the transformers T1 and T2 of the first transformer group 10A and each of the transformers T3 and T4 of the second transformer group 10B is as described above. The same as in the case of form.

According to the fourth embodiment, the voltage of the negative peak waveform by the first transformer group 10A and the positive peak waveform of the second transformer group 10B with respect to the ground GND within one cycle T of switching. The voltage is generated every half cycle. Therefore, the output voltage Vout between the output terminals 12a and 12b has a waveform that alternates between positive and negative as shown in FIG. 5B, but the load current Io flowing through the load 2 is alternately inverted.
Even in this case, the output voltage ± Vout of the AC high voltage similar to that of the inverter device 1 of the first embodiment shown in FIG. 1 can be supplied to the load 2.
If the end point b on the output terminal 12b side is connected to the ground instead of the end point a on the output terminal 12a side in FIG. 8, the same output voltage ± Vout can be obtained.
Alternatively, the output voltage ± Vout having the same waveform can be obtained by simply connecting the midpoint m to the ground and connecting the end points a and b to the load 2.

In the third embodiment shown in FIG. 7 in which the directions of the first excitation current ia and the second excitation current ib are opposite, the polarities of the transformers T1 and T2 of the first transformer group 10A are reversed. If it becomes, it becomes the same as that of 4th Embodiment.
That is, even if the first exciting current ia flows in the direction shown in FIG. 7, when it is turned off, the series point of the output windings Ns3 and Ns4 of the transformers T3 and T4 is connected to the ground GND. What is necessary is just to reverse the winding start and winding direction of an excitation winding or an output winding so that the voltage of a negative peak waveform may be generated on the m side. Also in this case, the waveform of the output voltage Vout is as shown in FIG.

[Fifth Embodiment]
FIG. 9 shows a fifth embodiment of the inverter device according to the present invention.
The basic configuration of the inverter device 1 of the fifth embodiment is the same as that of the inverter device 1 of the first embodiment shown in FIG. However, an improvement is made to reduce the influence of the demagnetization occurring in that case.

  In the inverter device 1 that supplies the output voltage having positive and negative voltage waveforms to the load 2 as in the first embodiment shown in FIG. 1, the magnetic flux change of the transformer should occur by the same amount on the positive side and the negative side. Has a phenomenon that is biased in either direction, which is called biased magnetization. This is presumably because the load current value slightly changes depending on the electrode structure of the load 2 when a positive waveform voltage is applied and when a negative waveform voltage is applied.

Further, in the inverter device 1 of the first embodiment shown in FIG. 1, as shown in FIG. 4B, a period during which a high voltage having a negative peak waveform is output by the first transformer group 10A. In addition, the second transformer group 10B also outputs a negative voltage whose peak value is about half. During the period when the voltage of the positive peak waveform is output by the second transformer group 10B, the first transformer group 10A also outputs a positive voltage whose peak value is about half.
For this reason, energy is stored in the first and second transformer groups 10A and 10B during the period in which the excitation current flows through each transformer, and the output voltage generated in the output winding when the excitation current is turned off is generated. Decrease (the crest value becomes smaller).

The inverter device 1 of the fifth embodiment shown in FIG. 9 is provided with means for improving these points.
Therefore, switching elements S1 and S2 are connected between both ends of the output windings Ns1 and Ns2 connected in series and between both ends of the output windings Ns3 and Ns4 of the first and second transformer groups 10A and 10B, respectively. ing.

The control circuit 15 turns on the switch element S1 during the period in which the switching element Q1 is turned on and flows the first excitation current ia, and switches the switch element S1 in the on state while the switching element Q2 is turned on and flows in the second excitation current ib. The element S2 is turned on.
That is, the control circuit 15 outputs the gate pulse P1 or P2 to turn on the switch element S1 or S2 in synchronization with the timing at which the switching element Q1 or Q2 is turned on by the switching signals Sp1 and Sp2, respectively.

In this embodiment, each of the switch elements S1 and S2 is a three-terminal semiconductor switch element such as a thyristor or SCR, and when the gate pulses P1 and P2 applied to the gate are at a high level, a forward direction is applied between the anode and the cathode. When a voltage is applied, it conducts in its forward direction. Therefore, a current is allowed to flow only in a predetermined direction that is the forward direction.
When the gate pulses P1 and P2 become low level, when the forward voltage between the anode and the cathode disappears, it turns off and remains as it is.

When the first exciting current ia is turned off, the inverter device 1 is negative on the end point a side with respect to the middle point m generated in the output windings Ns1 and Ns2 of the transformers T1 and T2 of the first transformer group 10A. A current is passed through the load 2 by the waveform voltage as shown by a broken line arrow in FIG. At this time, since the switch element S2 conducts in the direction in which the current flows, the load current passes through the switch element S2 and does not pass through the output windings Ns3 and Ns4 of the transformers T3 and T4.

When the second exciting current ib is turned off, a positive waveform voltage is applied to the end point b side with respect to the middle point m generated in the output windings Ns3 and Ns4 of the transformers T3 and T4 of the second transformer group 10B. , A current is passed through the load 2 as indicated by a thin solid arrow in FIG. At this time, since the switch element S1 conducts in the direction in which the current flows, the load current passes through the switch element S1 and does not pass through the output windings Ns1, Ns2 of the transformers T1, T2.

As described above, of the first and second transformer groups 10A and 10B, one that does not need to generate the output voltage, that is, the series circuit of the output windings of the transformer that stores the energy by passing the exciting current. The both ends are made conductive so that no unnecessary voltage is generated in the output winding.
Thereby, the loss of stored energy is eliminated, and when the excitation current of each transformer in the transformer group is turned off, a voltage having a large peak value can be output to the output winding. In addition, this can also reduce the influence of bias.
If a three-terminal semiconductor switch element such as a thyristor or SCR is used as the switch elements S1 and S2, the switch elements S1 and S2 can be brought into a conductive state in which a current flows only in a predetermined direction, instead of being completely short-circuited in the on state. Therefore, it is preferable.

Instead of the switch elements S1 and S2, a commutation diode is provided between the positive and negative output windings, and a coupling capacitor for preventing a short circuit between the output windings is inserted, so that a positive or negative AC output is provided. Only the voltage may be output.
Instead of the coupling capacitor, a rectifier diode may be provided to output an output voltage including a positive or negative alternating current pulsation and a positive or negative direct current, respectively.

[Sixth Embodiment]
A sixth embodiment of the inverter device according to the present invention is shown in FIG.
The configuration of the inverter device 1 of the sixth embodiment is almost the same as that of the inverter device 1 of the first embodiment shown in FIG. The difference from the first embodiment is that an inductor CH is connected between the positive input terminal 11b and the common connection point d of the excitation windings Np1 to Np4 of the transformers T1 to T4 constituting the step-up transformer 10. Only the interpolated points. The inductance of the inductor CH is set to 1 to 100 times the primary inductance Lp of each transformer T1 to T4. Thereby, the d point on the input side of each of the transformers T1 to T4 is floated in an alternating manner.

Transformer magnetism tends to be biased to either positive or negative, but tends to occur due to changes in load, mounting pattern, or a slight bias in the characteristics of the transformer. Therefore, the input voltage Vin (alternating current, direct current, or pulsating current) is not directly applied to the excitation windings Np1 to Np4 of the transformers T1 to T4, but is applied through the inductor CH.
As a result, both ends of the exciting winding of the transformer that does not pass the exciting current are in a floating state, so that power feedback that is clamped to the input voltage in both ON and OFF is avoided. That is, the bias magnetic force of the transformer is avoided.

The same effect can be obtained even if a capacitor is inserted instead of the inductor CH.
Further, the input voltage of the transformer may be a positive and negative power source to obtain a positive or negative output, and may be a single composite type that eliminates bias magnetism.

[Supplementary explanation]
Although the inverter device according to the present invention is a two-stone converter, such a converter uses the first and third quadrants of the BH curve, and the iron loss is doubled. In general, when output is performed in such a state, the magnetic flux density used is insufficient and power cannot be obtained. However, in this invention, in order to avoid the shortage of the magnetic flux density used, the transformer magnetic path is divided into at least two, and in order to obtain a high output of high voltage according to the specifications of the equipment used, A simple circuit with two transformers makes it possible to increase the number of transformers by two.
In addition, since either the positive or negative voltage waveform is output by the transformer of one group configuration and the peak value of the output voltage is the same, when the step-up transformer is configured of two groups, The number of turns Ns of the output winding can be halved.

Even in the same switching period, the generation period of the output voltage is halved and the rest time is almost eliminated, so that the discharge energy can be extracted up to twice as much.
Therefore, it is possible to efficiently obtain high-power electric power at a high voltage without causing the inverter device to be too large and without causing a shortage of the magnetic flux density of the transformer.
Therefore, the plasma generator that applies the output voltage of the inverter device according to the present invention to the discharge unit having the discharge electrode and the counter electrode can generate plasma continuously and efficiently.
According to the surface reforming apparatus that modifies the surface of the sheet material by the plasma generated by the plasma generating apparatus, the surface modification can be performed efficiently and uniformly in a short time.

The inverter device according to the present invention is not only a plasma generator and a surface modification device using the same, but also a semiconductor wafer bonding device, an image processing device, a coating device, a lighting device such as a fluorescent lamp , an air cleaner, and a crane neck discharge device. It can be used as a high-voltage power supply device that supplies an alternating high voltage to various devices such as a discharge lamp for a backlight of a liquid crystal TV and a sterilization device.

As mentioned above, although each embodiment of this invention has been described, the specific configuration of each part of the embodiment, the content of processing, and the like are not limited to those described therein.
Moreover, this invention is not limited to each embodiment mentioned above, It cannot be overemphasized that it is not limited at all except having the technical feature described in each claim of a claim.
Furthermore, the configuration examples, operation examples, modification examples, and the like of each embodiment described above may be modified or added as appropriate, or some of them may be deleted, and any combination may be implemented as long as they do not contradict each other. Of course, it is possible.

1: Inverter device 2: Load (discharge unit) 10: Step-up transformer
10A: first transformer group 10B: second transformer group 11a, 11b: input terminals 12a, 12b: output terminal 15: control circuit 21: discharge electrode
21a: Metal wire 21b: Dielectric (insulator) 22: Counter electrode
22a: Counter electrode 22 facing surface 23: Dielectric 24, 25: Feed lines T1 to T4: Transformers Np1 to Np4: Excitation windings Ns1 to Ns4: Output windings Q1, Q2: Switching elements Sp1, Sp2: Switching signal S1 , S2: Switch element P1, P2: Gate pulse CH: Inductor
Vin: Input voltage Vout: Output voltage

JP 2012-186984 A

Claims (6)

In an inverter device that switches an input voltage to flow an excitation current through an excitation winding on the primary side of the step-up transformer and outputs an AC voltage from an output winding on the secondary side of the step-up transformer.
The step-up transformer is composed of a first transformer group and a second transformer group,
Each of the first and second transformer groups is composed of a plurality of individual transformers having the same number and the same characteristics, and the excitation windings of the plurality of transformers are connected in parallel to be excited simultaneously. ,
The output windings of the plurality of transformers of the first and second transformer groups are all connected in series or in parallel to each other, and the first and second transformer groups are connected in series or in parallel to each other. Connect the middle point of each end of the output winding to each other, and connect each other end individually to a pair of output terminals that output the output voltage to the load.
A switch element is connected between both ends of the output windings connected in series or in parallel with each other in each transformer of the first and second transformer groups,
Control for flowing the first excitation current only to the excitation winding of each transformer of the first transformer group, and control for flowing the second excitation current only to the excitation winding of each transformer of the second transformer group Switching control means for repeatedly performing the alternating operation at a predetermined cycle is provided, and each output winding of the first transformer group and each output winding of the second transformer group are reversed with respect to the middle point. Alternately generate polar voltages ,
The switching control means turns on a switch element connected between both ends of the output winding of the first transformer group during a period in which the first excitation current flows, and a period in which the second excitation current flows. An inverter device characterized in that a switch element connected between both ends of the output winding of the second transformer group is turned on . 2. The inverter device according to claim 1 , wherein each of the switch elements is a three-terminal semiconductor switch element that allows a current to flow only in a predetermined direction when the switch element is in an ON state. The switching control means includes: a first switching element provided in series with a path through which the first excitation current flows in the excitation winding of each transformer of the first transformer group by the input voltage; and the second transformer A second switching element provided in series with a path through which the second excitation current flows through the excitation winding of each transformer of the group by the input voltage, and the first switching element and the second switching element are set in a predetermined manner. The inverter device according to claim 1 , further comprising a control circuit that controls to alternately turn on one and turn off the other in a cycle. In the inverter apparatus as described in any one of Claim 1 to 3 ,
The input voltage is applied to the excitation winding of each transformer through an inductor having an inductance greater than the inductance of the excitation winding of each transformer of each of the first and second transformer groups. Inverter device. The first, the second in the transformer group, any one of claims 1 to 4 in which the time axis of the output voltage waveform generated to the plurality of respective output windings of the transformers is characterized in that synchronized The inverter device according to one item. An inverter device according to any one of claims 1 to 5 , and a discharge unit having a discharge electrode and a counter electrode to which the output voltage is applied as the load of the inverter device, the discharge electrode and the counter electrode, A plasma generator characterized by generating plasma discharge between the two.

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