JP2008167584A - High-voltage applying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-voltage applying device applying a high voltage of a triangular wave, having steep rise and gradual fall, using a switching element with relatively small rated capacity in a circuit structure, and handling rush current and short-circuit current separately. <P>SOLUTION: This high-voltage applying device applies a high voltage, having steep rise and gradual fall, to a capacitive load using an inverter with the switching element. The values of a voltage component guided to an oscillating circuit are varied depending on the rush current or the short-circuit current. In addition, the oscillating circuit stops only for the short-circuit current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high voltage application device that applies a high voltage that is applied to a capacitive load and rises steeply and falls slowly.

  A plasma generating power supply device is known for generating ozone. As this type of power supply device, patent applications have been filed for the devices disclosed in Patent Literature 1 and Patent Literature 2.

  That is, in the apparatus disclosed in Patent Document 1, an alternating voltage is supplied by an inverter having a switching element. At this time, an inductor that resonates with a capacitive load is provided, and a high voltage generated by the resonance is applied. And is improving power factor.

  In the device disclosed in Patent Document 2, the rise and rise of the applied high voltage are generated by intermittently generating one cycle of the sine wave that has generated resonance by using the inductance of the transformer. A high voltage with a rapid fall and a narrow pulse width is generated.

Technologies such as Patent Document 1 and Patent Document 2 as described above have been disclosed. For example, streamer discharge or glow discharge is performed in removing nitrogen oxide (NO _x ) or sulfur oxide (SO _x ) in combustion exhaust gas. In this case, it has been found that nitrogen oxides and sulfur oxides can be removed by applying a high voltage with a particularly steep rise.
JP-A-11-288796 JP 2000-278962 A

  Unlike the Patent Document 1 and Patent Document 2 that consider the background art, the present invention applies a so-called triangular wave-shaped high voltage with a steep rise and a gradual fall so that the rated capacity of the circuit configuration can be reduced. An object is to enable use of a relatively small switching element. And in order to be able to deal with the inrush current supplied to the capacitive load separately from the fault current that occurs at the time of a short circuit, etc., it is also possible to reduce the rated capacity of the switching element used from this aspect. Yes.

FIG. 1 shows an overall configuration of an embodiment of the present invention.
Reference numeral 1 in the figure denotes a capacitive load, which is a dielectric barrier discharge reactor (DBD Load) that discharges and excites gas to generate plasma, and 2 is a DC voltage supply circuit having a rectifier circuit and a smoothing circuit. Reference numeral 3 denotes a switching circuit which constitutes an inverter using a plurality of switching elements SWi, 4 is a current limiting inductance, and 5 is a pulse transformer.

  6 is a current detector, 7 is an amplifier circuit, which obtains a proportional voltage component proportional to the detected DC current component and an integrated voltage component obtained by integrating the DC current component with a predetermined time constant, 8 Is an OR circuit for extracting the larger component of the proportional voltage component and the integral voltage component.

  Further, reference numeral 9 denotes an oscillation circuit that oscillates a rectangular wave with a duty ratio of 50%, for example, with a set period. Depending on the magnitude of the output of the OR circuit 8, the rectangular wave with a duty ratio of 50% is, for example, 25%. Is set to output a rectangular wave with a duty ratio of 0% (that is, oscillation stop) when the output of the OR circuit 8 exceeds the limit and becomes large. It is what.

  Next, reference numeral 10 denotes a short pulse generating circuit which generates a rectangular wave having a predetermined duty ratio of 10%, for example, based on the rising point of the output from the oscillation circuit 9. A gate drive circuit 11 receives the output of the short pulse generation circuit 10 and generates a gate control signal for the switching element SWi.

  In principle, in the switching circuit 3, when the switching elements SW1 and SW4 are turned on, a current is supplied to the pulse transformer 5 from the upper side to the lower side in the figure, and conversely, the switching elements SW2 and SW3 are turned on. When turned on, a current is supplied from the lower side to the upper side of the pulse transformer 5 in the drawing. That is, a positive triangular wave and a negative triangular wave, which are steeply rising and relatively slowly falling, are applied to the capacitive load 1 in accordance with the oscillation frequency of the oscillation circuit 9.

  In other words, since the duty ratio of the rectangular wave from the short pulse generation circuit 10 is a value of 50% or less, the above-described triangular wave having a steep rising and relatively slow falling is applied.

As described above, a triangular wave having a sharp rise and a relatively slow fall is applied to the capacitive load 1, and active species (radicals) such as N, O, and OH are generated by discharge at the rise of the voltage. Thus, nitrogen oxides (NO _x ) and sulfur oxides (SO _x ) in the combustion exhaust gas can be removed.

  However, in this case, since a voltage with a steep rise is applied to the capacitive load 1, the value of the inrush current flowing into the capacitive load 1 becomes sufficiently large, for example, when a short circuit occurs. It becomes difficult to classify with.

  In the case of the present invention, in consideration of this point, in the case of the inrush current, the current value returns to the state of “0” in a short period of time, but in the case of a short circuit, the current detector 6 shown in FIG. By utilizing the fact that the average value of the current component at a predetermined time becomes large, in the case of a short circuit, the oscillation from the oscillation circuit 9 is stopped and the switching elements SW1 to SW4 are prevented from being turned on. I have to.

  In the case of the short circuit, the operations of the amplifier circuit 7, the OR circuit 8, and the oscillation circuit 9 shown in FIG. 1 prevent the switching element SWi from being turned on. Thus, the switching element SWi is normally turned on / off.

  The output from the OR circuit 8 shown in the figure is a proportional voltage component proportional to the direct current component detected by the current detector 6 (the magnitude changes) and the direct current component with a predetermined time constant (CR The output corresponds to the magnitude of the larger voltage component of the integrated voltage component integrated (using a time constant circuit).

  The oscillation circuit 9 normally oscillates a rectangular wave with a duty ratio of 50%. However, when the output of the OR circuit 8 becomes abnormally large, the oscillation circuit 9 has a duty ratio of 0% (that is, the oscillation circuit 9). On the other hand, even if the inrush current is slightly larger than the normal value, a rectangular wave with a duty ratio of 25% is oscillated, and the switching element SWi is kept on / off. ing.

  In the present invention, a high voltage with a steep rise is applied to the capacitive load, but even if a relatively large inrush current generated at that time becomes too large, the operation can be continued normally. In the case of a short circuit, the switching element SWi can correctly stop the on / off operation.

  The high voltage application device of the present invention has a configuration as shown in FIG. 1, but FIG. 2 shows a waveform diagram of each part.

  [1], [2]: The oscillation circuit 9 oscillates two rectangular waves whose phases are shifted. There is actually a predetermined “simultaneous off period” between the “oscillation circuit output signal 1” and the “oscillation circuit output signal 2” shown in the figure, but in the present specification, for the sake of simplicity. Such a case is also called a rectangular wave with a duty ratio of 50%.

  [3], [4]: The short pulse generation circuit 10 generates short pulses that rise in response to the rising timings of the “oscillation circuit output signal 1” and “oscillation circuit output signal 2” shown in the figure. That is, the illustrated “short pulse generation circuit output signal 1” and “short pulse generation circuit output signal 2” are generated.

  [5], [6], [7], [8]: The gate signals applied to the switching elements SW1 to SW4 are “short pulse generation circuit output signal 1” and “short pulse generation circuit output signal 2”. Based on this, it will be as shown in the figure.

  [9]: A positive wave and a negative wave having a sharp rise and a slow fall are applied to the capacitive load via the pulse transformer 5. The peak values of these triangular waves are limited to a predetermined level by the current limiting inductance 4 shown in FIG.

  FIG. 3 shows a high voltage waveform applied to the capacitive load at the timing of turning on / off the switching element.

For example, assuming that the timing when the switching elements SW1 and SW4 are turned on is the time point of the start point in FIG. 3A and the time point when the switching elements SW1 and SW4 are turned off is the time point of the end point in FIG. T (rise) (period (a) in the figure) is T (rise) = T (r · delay) + 5τ (rise)
T (r · delay): Total rise time of PWM switching regulator IC, one-shot IC, photocoupler, and semiconductor switching element SW.
τ (rise): Time constant based on the equivalent capacitance C of the capacitive load 1 and the combined resistance value R _{t of} the switching circuit, current limiting inductance, pulse transformer, wiring, etc. (see “4. Multiplying “605” gives 99% of the peak value, so multiplying by the time constant “5” gives the time to reach the peak value).
Given in.

Further, the peak voltage maintaining time T (peak) (period (b) in the figure) is T (peak) = T (on) −T (rise)
However, T (on): the pulse width set by the short pulse generation circuit (note that the sum of T (peak) and T (rise) is smaller than the fall time T (fall) described later. (On).

Further, assuming that the timing when the switching elements SW1 and SW4 are turned off is the time point of the starting point in FIG. 3C, and the time when the switching elements SW1 and SW4 are turned on is the time point of the end point in FIG. The fall time T (fall) (period (c) in the figure) is T (fall) = T (f · delay) + 5τ (fall)
Where T (f · delay): total of delay time of fall of PWM switching regulator IC, one-shot IC, photocoupler and semiconductor switching element SW.
tau (fall): the equivalent capacitance C of the capacitive load 1, the time constant by the resistance R _B of the capacitive load 1 (also in this case and it is time to reach the zero level by multiplying the "5").

  FIG. 4 shows a principle configuration diagram of the amplifier circuit and the OR circuit shown in FIG. Reference numerals 7 and 8 in the figure correspond to FIG. 1, 7-10 and 7-11 are amplifiers, 7-20 is a time constant circuit having a CR circuit, which corresponds to the integration circuit section, and 7-21 is a resistor. A proportional circuit portion having a circuit, 8-10 and 8-11 are diodes, and 8-2 is a voltage dividing circuit.

  The direct current component detected by the current detector 6, which is supplied to the amplifier circuit 7, is input to the amplifier 7-11 via the proportional circuit unit 7-21 and is output as a proportional voltage component. The detected direct current component is input to the amplifier 7-10 via the integrating circuit unit 7-20 and output as an integrated voltage component.

  Both voltage components are input to an OR circuit 8 constituted by diodes 8-10 and 8-11 and a voltage dividing circuit 8-2, and, as is well known, a component having a larger value is selected and divided. Pressed and output. The divided output is supplied to the oscillation circuit 9 shown in FIG.

  As described above, when a high voltage with a steep rise is applied to the capacitive load 1, a large inrush current flows into the capacitive load 1. In a form corresponding to this inrush current, the direct current component output from the current detector 6 shown in FIG. 1 also instantaneously increases, but the direct current component also decreases as the inrush current settles down. As a result, even when the proportional voltage component and the integrated voltage component corresponding to the inrush current are supplied to the OR circuit 8, the output from the voltage dividing circuit 8-2 shown in FIG. The voltage is such that it only increases.

  On the other hand, if a short circuit occurs in the capacitive load 1, the short circuit current associated with the short circuit is sufficiently large and lasts in time. From this, in the case of a direct current component corresponding to the short-circuit current detected by the current detector 6, the voltage from which the output from the voltage dividing circuit 8-2 in the OR circuit 8 continues beyond a predetermined level. It has become.

FIG. 5 is a diagram for explaining the duty ratio of the rectangular wave output from the oscillation circuit.
The configuration of the oscillation circuit 9 (shown in FIG. 1) and the oscillation frequency of the rectangular wave output from the oscillation circuit 9 will be described later. As shown on the left side of FIG. 5, the duty of the rectangular wave oscillated by the oscillation circuit 9 The ratio is such that the duty ratio is 50% when the voltage supplied from the OR circuit 8 is v ₁ or less in the figure, and the voltage supplied from the OR circuit 8 is v ₂ or v ₂ or more. , The duty ratio is set to 0% (that is, oscillation is stopped). When the voltage supplied from the OR circuit 8 exceeds v ₁ and is smaller than v ₂ , the duty ratio becomes 25%. Has been.

As described above, in the case of the inrush current flowing into the capacitive load 1, the output from the OR circuit 8 is instantaneously described above as shown as “inrush current portion” on the left side of FIG. The voltage v ₁ may be exceeded, but the voltage v ₂ is not reached (designed so as not to reach), but when a short circuit occurs, the “short circuit current portion” is shown on the left side of FIG. and that, the output from the OR circuit 8 exceeds the voltage v _2.

  Therefore, in the case of the present invention, when a short circuit occurs, the oscillation circuit 9 stops oscillating (that is, the duty ratio becomes 0%), and on the other hand, even if the inrush current becomes somewhat large, the oscillation circuit 9 No. 9 is such that a rectangular wave with a duty ratio of 50% temporarily becomes a rectangular wave with a duty ratio of 25%, and oscillation is maintained.

  In the case of the present invention, as described above, since the short pulse generation circuit 10 generates a short pulse having a predetermined duty ratio based on the output from the oscillation circuit 9, the duty ratio of the oscillation circuit 9 is determined as described above. Even if the value changes from 50% to 25%, the duty ratio of the pulse wave supplied to the gate drive circuit 11 shown in the figure does not change. However, when a short circuit occurs, the oscillation circuit 9 stops oscillating and the short pulse generation circuit 10 does not generate a short pulse. As a result, the switching elements SW1 to SW4 in the switching circuit 3 are turned on / off. Stop.

  FIG. 6 is a diagram showing a configuration of an embodiment of a current detector, an amplifier circuit, and an OR circuit used in the present invention.

  “Terminal 5” and “Terminal 6” shown in the current detector 6 are connected between the rectifier circuit in the DC voltage supply circuit 2 shown in FIG. 1 and the switching circuit 3 shown in FIG. Then, it is supplied from the “terminal 3” to the amplifier circuit 7 as the above-described DC current component.

  The amplifier circuit 7 shown in FIG. 6 is divided internally into “terminals 1 to 4” and “terminals 5 to 8”. The “terminals 1 to 4” side corresponds to the amplifier 7-10 side shown in FIG. 4, and the “terminals 5 to 8” side corresponds to the amplifier 7-11 side shown in FIG. The “output terminal 1” on the amplifier 7-10 side and the “output terminal 7” on the amplifier 7-11 side are led to the OR circuit 8.

  FIG. 7 is a diagram showing a configuration of one embodiment of an OR circuit, an oscillation circuit, and a short pulse generation circuit used in the present invention.

  In the oscillation circuit 9, the portion surrounded by the “oscillation frequency setting” shown in the drawing is a portion for setting the oscillation frequency. From the portions shown as “terminal EA” and “terminal EB” in the drawing, Signal 1 "and" Oscillation circuit output signal 2 "are output.

In the oscillation circuit 9, a portion surrounded by “duty ratio” shown in the figure is a circuit section that determines the duty ratio shown in FIG. 5. When the output from the OR circuit 8 is equal to or lower than the voltage v ₁ shown in FIG. 5, the oscillation circuit 9 oscillates a rectangular wave having a duty ratio of 50% of the set frequency. That is, “oscillation circuit output signal 1” and “oscillation circuit output signal 2” shown in FIG. 2 are oscillated.

Needless to say, when the output voltage from the OR circuit 8 exceeds v ₁ and is smaller than v ₂ , a rectangular wave with a duty ratio of 25% is generated, and the output voltage from the OR circuit 8 becomes v ₂ or more. When this happens, the oscillation circuit 9 stops oscillation.

  In the short pulse generation circuit 10, a portion indicated as “pulse width setting” is a portion for setting a duty ratio of a generated short pulse. Then, the output from the oscillation circuit 9 is input to the terminals indicated by “terminal 1A (inverted)” and “terminal 2A (inverted)”, and the output from “terminal 1Q” and “terminal 2Q” The output is guided to the gate drive circuit 11 shown in FIG.

As described above, according to the present invention, for example, in removing nitrogen oxide (NO _x ) and sulfur oxide (SO _x ) in combustion exhaust gas, a method using a low temperature plasma such as streamer discharge or glow discharge is considered. In this case, nitrogen oxides and sulfur oxides can be removed by applying a high voltage with a particularly steep rise.

1 shows an overall configuration of an embodiment of the present invention. The waveform diagram of each part is shown. The high voltage waveform applied to the capacitive load at the timing of turning on / off the switching element is shown. FIG. 2 shows a principle configuration diagram of an amplifier circuit and an OR circuit shown in FIG. 1. It is a figure explaining the duty ratio of the rectangular wave which an oscillation circuit outputs. It is a figure which shows one Example structure of the current detector used for this invention, an amplifier circuit, and OR circuit. It is a figure which shows one Example structure of the OR circuit used in this invention, an oscillation circuit, and a short pulse generation circuit.

Explanation of symbols

1: capacitive load 2: DC voltage supply circuit 3: switching circuit 4: current limiting inductance 5: pulse transformer 6: current detector 7: amplifier circuit 8: OR circuit 9: oscillation circuit 10: short pulse generation circuit 11: Gate drive circuit

Claims (3)

In a high voltage application device that applies a steep and high voltage to a capacitive load,
A switching circuit that supplies a steep rising pulse wave to a capacitive load via a pulse transformer
The switching circuit has a plurality of switching elements that are turned on and off by gate control,
The magnitude of the larger voltage component of the direct current component flowing into the switching circuit, the proportional voltage component proportional to the direct current component, and the integrated voltage component obtained by integrating the direct current component with a predetermined time constant Corresponding to the predetermined duty ratio α%, the duty ratio 0%, and at least an intermediate duty ratio β between the duty ratio α% and the duty ratio 0% (α>β> 0)% An oscillation circuit that is changed to take
Corresponding to the rising of the output of the rectangular wave from the oscillation circuit, a short pulse that generates an on-voltage for a predetermined period is generated, and the switching element is gate-controlled based on the short pulse. A high voltage application device characterized. In a high voltage application device that applies a steep and high voltage to a capacitive load,
A switching circuit that supplies a steep rising pulse wave to a capacitive load via a pulse transformer
In the switching circuit, a plurality of gate-controlled switching elements are ON / OFF controlled by a gate drive circuit,
A DC voltage supply circuit applied to the switching circuit;
A current detector for detecting a DC current supplied from the DC voltage supply circuit unit to the switching circuit;
An OR circuit that extracts a larger component of a voltage component corresponding to the DC current detected by the current detector and an integrated voltage component obtained by integrating the voltage component with a predetermined time constant;
Depending on the output level of the OR circuit, the duty ratio of the oscillating rectangular wave is set to a predetermined duty ratio α%, a duty ratio 0%, and between the duty ratio α% and the duty ratio 0%. An oscillation circuit that is changed so as to be able to take at least an intermediate duty ratio β (α>β> 0)% of
In response to the rising of the rectangular wave output from the oscillation circuit, a short pulse generation circuit that generates an on-voltage for a predetermined short period;
And a gate control circuit that outputs a gate control signal for turning on / off the plurality of switching elements based on an output from the short pulse generation circuit.   The current limiting inductance element for limiting a magnitude of a current component flowing into the capacitive load is inserted in series between the switching circuit and the pulse transformer in the circuit. 2. The high voltage application device according to 2.

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