JP7361666B2 - Power supply device for plasma reactor and control method for power supply device for plasma reactor - Google Patents

Description

The present invention relates to a plasma reactor power supply device that drives a plasma reactor, and a method of controlling the plasma reactor power supply device.

Exhaust gas emitted from an internal combustion engine such as a diesel engine includes CO (carbon monoxide), HC (hydrocarbons), NOx (nitrogen oxides), PM (particulate matter), and the like.

In contrast, a method has been proposed in which PM and the like contained in exhaust gas are removed using a plasma reactor. A plasma reactor includes, for example, a plurality of positive and negative electrode panels. These electrode panels have electrodes built into a dielectric body, and the positive and negative electrode panels have positive and negative electrode panels facing each other alternately at intervals in a direction perpendicular to the flow direction of exhaust gas. It is arranged as follows. When a pulsed high voltage is applied between the positive electrode panel and the negative electrode panel from the plasma reactor power supply device, a dielectric barrier discharge (silent discharge) occurs, and low-temperature plasma ( Non-equilibrium plasma) is generated, and PM and the like in the exhaust gas flowing between the positive and negative electrode panels is oxidized to CO ₂ , H ₂ O, etc. and removed or rendered harmless. Additionally, a plasma reactor may be used to generate ozone from oxygen or air.

A flyback step-up transformer is used for the plasma reactor power supply. For example, in Patent Document 1, the ground potential side of the primary coil of this flyback step-up transformer is grounded via a switching element, while the power source side of this primary coil is directly connected to the positive terminal of a DC power source. Also, the secondary coil of the flyback step-up transformer is connected to the electrode of the plasma reactor. When the switching element is turned on, current flows through the primary coil of the flyback step-up transformer, and energy is stored in the primary coil. After that, when the switching element is turned off, a back electromotive force is generated in the primary coil, which generates a pulse-like high voltage in the secondary coil of the flyback step-up transformer according to the turns ratio with the primary coil. do. Therefore, by repeatedly turning on and off the switching element at a certain period, a pulse-like high voltage is generated in the secondary coil intermittently, and this is applied between the electrodes of the plasma reactor to generate an intermittent discharge. cause to occur.

For example, in the plasma reactor power supply device of Patent Document 2, in addition to grounding the ground potential side (low side) of the primary coil of the flyback step-up transformer via a switching element, the power supply side (high side) of the primary coil is grounded via a switching element. is connected to the positive terminal of the DC power supply via another switching element. Also, the secondary coil of the flyback step-up transformer is connected to the electrode of the plasma reactor. When the two switching elements are turned on, current flows through the primary coil of the flyback step-up transformer, and energy is stored in the primary coil. Then, when the low-side switching element is turned off, a back electromotive force is generated in the primary coil, which generates a pulsed high voltage in the secondary coil of the flyback step-up transformer according to the turns ratio with the primary coil. occurs. Therefore, by repeatedly turning on and off the switching element at a certain period, a pulsed high voltage is generated intermittently in the secondary coil, which is applied between the electrodes of the plasma reactor, causing an intermittent discharge. let

In addition, in the power supply device of Patent Document 2, in order to increase the primary voltage applied to the primary coil of the flyback step-up transformer, a snubber circuit, a diode, a step-up capacitor, etc. connected in parallel with the low-side switching element are provided. The energy remaining after generating a pulsed high voltage in the secondary coil is stored in the boost capacitor. Then, when the low-side switching element is turned on again, the voltage applied to the primary coil is the sum of the voltage of the DC power supply and the voltage of the step-up capacitor, so that it is higher than the voltage of the DC power supply.

JP 2017-150456 Publication Japanese Patent Application Publication No. 2017-118751

However, in the plasma reactor power supply device disclosed in any of the documents, only one pulse-like high voltage is generated in the secondary coil when the low-side switching element is turned on and then turned off. In other words, these plasma reactor power supplies generate one pulse-like high voltage in the secondary coil each time the low-side switching element is turned on and then turned off, and the energy accumulated in the primary coil is used to generate a high voltage pulse. could not be fully utilized for dielectric barrier discharge in plasma reactors, resulting in low energy efficiency.

The present invention has been made in view of the current situation, and it is possible to generate positive and negative alternating discharges multiple times in a plasma reactor by charging the primary coil with energy once, and also to achieve high energy efficiency. The present invention provides a plasma reactor power supply device and a method of controlling the plasma reactor power supply device.

One aspect of the present invention for solving the above problems is to provide a flyback step-up transformer that has a primary coil including a ground side terminal and a power supply side terminal, and a secondary coil that connects a plasma reactor to both ends; a low side switch element connected between the ground side terminal of the coil and the ground potential; a high side switch element connected between the power side terminal of the primary coil and the positive terminal of the DC power supply; A power supply device for a plasma reactor, comprising a switch element and an element control unit that controls on/off of the high side switch element, wherein the element control unit controls the high side switch element when the DC power source and the plasma reactor are connected. Charge control that turns on the side switch element and the low-side switch element to charge energy from the DC power source to the primary coil, and turns off the low-side switch element to charge positive and negative energy to the plasma reactor via the secondary coil. Alternating discharge control in which alternating alternating voltages are applied to generate alternating positive and negative discharges in the plasma reactor, and the above at the same time as turning off the low-side switch element in the alternating discharge control, or immediately after turning off the low-side switch element. High-side off control in which the high-side switch element is turned off during a turn-off tolerance period in which a voltage is generated in the primary coil such that the ground side terminal has a higher potential than the power supply side terminal; Afterwards, the high-side switch element is turned on, and a part of the energy remaining in the secondary coil and the plasma reactor is regenerated into the DC power supply, and the regeneration control is repeatedly executed. Power supply system.

In addition to the flyback step-up transformer, low-side switch element, and high-side switch element, the above-mentioned plasma reactor power supply device can repeatedly perform the above-mentioned charge control, alternating discharge control, high-side off control, and regeneration control. The device includes an element control section configured as follows. Therefore, by charging the primary coil with energy once, alternating positive and negative discharges can be generated in the plasma reactor multiple times. Furthermore, since a part of the energy can be regenerated into the DC power supply, a plasma reactor power supply device with good energy efficiency can be achieved.

Note that as the low-side switch element and the high-side switch element, it is preferable to use a switch element for power control with a high withstand voltage, and for example, a power MOSFET, IGBT, thyristor, GTO, triac, etc. can be used.

Further, the element control section may be configured to be able to repeatedly perform charge control, alternating discharge control, high side off control, and regeneration control, and may be configured entirely by a logic circuit that executes these controls. Alternatively, it may be configured by software processing by a microcomputer and a driver circuit that drives the low-side switching element and the high-side switching element according to instructions from the microcomputer. It also consists of a logic circuit that performs software processing by a microcomputer, a logic circuit that performs predetermined logic processing according to instructions from the microcomputer, and a driver circuit that drives the low-side switch element and high-side switch element according to the instructions of this logic circuit. You may.

Further, examples of the plasma reactor include those used to remove PM from exhaust gas from an internal combustion engine, and those that generate ozone using supplied air and oxygen, as described above.
Examples of the DC power source include, for example, a DC stabilized power source, a battery, and a DC power source consisting of a battery and a DC-DC converter that outputs an output voltage that is boosted or stepped down from the battery voltage.

The above-described power supply device for a plasma reactor includes a snubber capacitor connected in parallel with the primary coil and electrically connected to the ground side terminal and the power supply side terminal of the primary coil. good.

In this plasma reactor power supply device, a snubber capacitor is provided in parallel with the primary coil. This absorbs surge voltage and reduces overvoltage that occurs when the low-side switch element is turned off and high voltage is generated in the secondary coil after energy is charged to the primary coil in charge control, and the low-side switch element and The high side switch element can be protected.

Furthermore, the plasma reactor power supply device according to any one of the above, further comprising: a low-side voltage detection unit that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential; a high-side voltage detection section that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive electrode terminal, and the element control section detects the high-side switch element in the regeneration control. In the charge control after turning on, when the low-side voltage detection section or the high-side voltage detection section detects that the low-side voltage is equal to or lower than a first threshold voltage lower than the output voltage of the DC power supply. The plasma reactor power supply device may be configured to be able to perform soft-on control for turning on the low-side switch element.

The above-described power supply device for a plasma reactor includes at least one of a low-side voltage detection section and a high-side voltage detection section, and the element control section performs charge control such that the low-side voltage at the low-side voltage detection section is equal to or lower than the first threshold voltage. Soft-on control is performed to turn on the low-side switch element when it is detected that the low-side voltage is equal to or lower than the first threshold voltage through the high-side voltage detected by the high-side voltage detection section. That is, the low-side switch element is turned on by soft switching. Thereby, in charge control, when turning on the low-side switch element, switching loss in the low-side switch element can be reduced, and energy efficiency can be further improved.

Furthermore, the plasma reactor power supply device according to any one of the above, further comprising: a low-side voltage detection unit that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential; and a high-side voltage detection section that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive electrode terminal, and the element control section detects the low-side voltage in the regeneration control. soft-on control for turning on the high-side switch element when the high-side voltage detection unit or the high-side voltage detection unit detects that the high-side voltage is equal to or lower than a second threshold voltage lower than the output voltage of the DC power supply; It is preferable to use a plasma reactor power supply device configured to be executable.

The plasma reactor power supply device described above also includes at least one of a low-side voltage detection section and a high-side voltage detection section. In addition, in regeneration control, the element control section detects that the high-side voltage is below the second threshold voltage through the low-side voltage detected by the low-side voltage detection section, or when the high-side voltage is detected by the high-side voltage detection section. When it is detected that the voltage is lower than the second threshold voltage, soft-on control is performed to turn on the high-side switch element. That is, the high side switch element is turned on by soft switching. Thereby, in the soft-on control of regeneration control, when turning on the high-side switch element, switching loss in the high-side switch element can be reduced, and energy efficiency can be further improved.

Another aspect for solving the above problem is a flyback step-up transformer having a primary coil including a grounding side terminal and a power supply side terminal, and a secondary coil connecting a plasma reactor to both ends, and A plasma reactor comprising: a low side switch element connected between the ground side terminal and the ground potential; and a high side switch element connected between the power supply side terminal of the primary coil and the positive terminal of a DC power source. 2. A control method for a power supply device for use in a power supply device, wherein, in a state where the DC power supply and the plasma reactor are connected, the high-side switch element and the low-side switch element are turned on to charge the primary coil from the DC power supply. an alternating discharge step of turning off the low-side switch element and applying an alternating voltage of alternating positive and negative to the plasma reactor via the secondary coil to generate a discharge of alternating positive and negative in the plasma reactor; At the same time as the low-side switch element is turned off in the alternating discharge step, or immediately after the low-side switch element is turned off, a voltage is generated in the primary coil such that the ground side terminal has a higher potential than the power supply side terminal. A high-side off step in which the high-side switch element is turned off within the allowable turn-off period, and after the turn-off allowable period, the high-side switch element is turned on to remove part of the energy remaining in the secondary coil and the plasma reactor. This is a control method for a plasma reactor power supply device, which repeatedly performs a regeneration step of causing the DC power source to regenerate the plasma reactor.

In the above-described method for controlling a power supply device for a plasma reactor, the power supply device for a plasma reactor is equipped with a flyback step-up transformer, a low-side switch element, and a high-side switch element, and the above-described charge step, alternating discharge step, and high-side off step are performed. , and an element control section configured to be able to repeatedly execute the regeneration step. Therefore, with this power supply device, positive and negative alternating discharges can be generated in the plasma reactor multiple times by charging the primary coil with energy once. Furthermore, since a part of the energy can be regenerated into the DC power supply, the plasma reactor power supply device can be controlled with good energy efficiency.

Further, in the above-described method for controlling a power supply device for a plasma reactor, the power supply device for a plasma reactor is electrically connected to the ground side terminal and the power supply side terminal of the primary coil and connected in parallel with the primary coil. This is a method of controlling a power supply device for a plasma reactor equipped with a snubber capacitor.

In this method of controlling a plasma reactor power supply device, a snubber capacitor is provided in parallel with the primary coil in the plasma reactor power supply device. This reduces overvoltage by absorbing the surge voltage that occurs when the low-side switch element is turned off and high voltage is generated in the secondary coil in the alternating discharge step after energy is charged to the primary coil in the charge step. , the low side switch element and the high side switch element can be protected.

Furthermore, in the method for controlling any of the plasma reactor power supply devices described above, the plasma reactor power supply device includes a low-side voltage that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential. a detection unit; and a high-side voltage detection unit that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive terminal of the DC power supply; In the charging step after turning on the side switch element, the low-side voltage detection section or the high-side voltage detection section detects that the low-side voltage is equal to or lower than a first threshold voltage that is lower than the output voltage of the DC power supply. It is preferable that the method for controlling the plasma reactor power supply device includes a soft-on step of turning on the low-side switch element when the low-side switch element is turned on.

In the method for controlling a plasma reactor power supply device described above, the plasma reactor power supply device further includes at least one of a low-side voltage detection section and a high-side voltage detection section. In addition, in the soft-on step of the charge step, when the low-side voltage detection section detects that the low-side voltage is below the first threshold voltage, or when the low-side voltage detects the high-side voltage detected by the high-side voltage detection section, the low-side voltage becomes the first threshold voltage. When it is detected that the voltage is lower than 1 threshold voltage, the low side switch element is turned on. That is, the low-side switch element is turned on by soft switching. Thereby, in the charging step, when the low-side switch element is turned on, switching loss in the low-side switch element can be reduced, and energy efficiency can be further improved.

In addition, in any of the aforementioned plasma reactor power supply device control methods, the plasma reactor power supply device includes a low side voltage that is a voltage of the ground side terminal of the primary coil with respect to the ground potential. The regeneration step includes at least one of a voltage detection unit and a high-side voltage detection unit that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive terminal of the DC power supply, and the regeneration step includes: Software that turns on the high-side switch element when the low-side voltage detection section or the high-side voltage detection section detects that the high-side voltage is equal to or lower than a second threshold voltage lower than the output voltage of the DC power supply. It is preferable to use a control method for a plasma reactor power supply device that includes on-step control.

Also in the above-described method for controlling a plasma reactor power supply device, the plasma reactor power supply device further includes at least one of a low-side voltage detection section and a high-side voltage detection section. In addition, in the soft-on step of the regeneration step, when it is detected that the high-side voltage is below the second threshold voltage through the low-side voltage detected by the low-side voltage detection section, or when the high-side voltage is detected by the high-side voltage detection section When it is detected that the voltage is lower than the second threshold voltage, the high side switch element is turned on. That is, the high side switch element is turned on by soft switching. Thereby, when turning on the high-side switch element in the soft-on step of the regeneration step, switching loss in the high-side switch element can be reduced, and energy efficiency can be further improved.

FIG. 1 is an explanatory diagram showing a schematic configuration of a plasma reactor driven by a plasma reactor power supply device according to an embodiment. FIG. 2 is an explanatory diagram showing a schematic circuit configuration of a plasma reactor power supply device according to an embodiment, which is connected to a battery and a plasma reactor. It is a flowchart of drive control of the power supply device for plasma reactors concerning an embodiment. It is a timing chart which shows the operation|movement of each part when the power supply device for plasma reactors which concerns on embodiment is driven.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a plasma reactor PR, and FIG. 2 shows a schematic configuration of a plasma reactor power supply device 10 according to an embodiment. Further, FIG. 3 shows a flowchart of drive control of the plasma reactor power supply device 10.

<Description of plasma reactor>
First, the plasma reactor PR driven by the plasma reactor power supply device 10 will be explained. The plasma reactor PR is interposed in the middle of the exhaust pipe EX of the engine, for example, in order to remove PM, CO, HC, NOx, etc. contained in the exhaust gas GS discharged from an automobile engine (not shown).

The plasma reactor PR (see FIG. 1) is driven by a plasma reactor power supply device 10 connected to a battery BT (battery voltage Vs=12V (nominal)). In this plasma reactor PR, a positive electrode panel PNp has a rectangular plate-shaped positive discharge electrode Dp built in a rectangular plate-shaped dielectric Dd, and a rectangular plate-shaped negative discharge electrode Dn is built in a rectangular plate-shaped dielectric Dd. It has built-in negative electrode panels PNn, which are alternately stacked in the thickness direction with gaps GP in between. The stacked positive electrode panel PNp and negative electrode panel PNn are arranged such that the gap GP extends in the direction along the flow of the exhaust gas GS (left-right direction in FIG. 1). An example of the material for the positive discharge electrode Dp and the negative discharge electrode Dn is tungsten. In addition, an example of the material of the dielectric Dd is alumina.

In this embodiment, a high-voltage secondary coil output with a sinusoidal waveform that alternates between positive and negative and attenuates is output from the plasma reactor power supply device 10 between the positive discharge electrode Dp and the negative discharge electrode Dn of the plasma reactor PR. Voltage VL2 (see column (j) in FIG. 4) is applied repeatedly (for example, at a frequency of about 100 kHz). When the output voltage VL2 of the plasma reactor power supply device 10 is applied between the discharge electrodes Dp and Dn, a dielectric barrier discharge occurs between the positive electrode panel PNp and the negative electrode panel PNn, and this dielectric barrier discharge causes a low temperature in the gap GP. Plasma is generated. Due to the generation of this low-temperature plasma, PM and the like contained in the exhaust gas GS flowing between the electrode panels PNp and PNn is oxidized (burned) and removed, thereby rendering it harmless.

<Description of power supply device for plasma reactor>
Next, the plasma reactor power supply device 10 that drives the plasma reactor PR will be explained. This power supply device 10 for a plasma reactor includes a flyback step-up transformer 1, a low-side switch element 4 and a high-side switch element 5 for controlling current flow, a snubber capacitor 6, and on/off controls for the low-side switch element 4 and the high-side switch element 5. It includes an element control section 11 for controlling. The element control unit 11 includes a low-side gate driver 12 that turns on and off the low-side switch element 4, a high-side gate driver 13 that turns on and off the high-side switch element 5, a voltage detection unit 14L that detects the low-side voltage Vlds, and a controller 15. There is.

The flyback step-up transformer 1 has a primary coil 2 and a secondary coil 3. The power supply side terminal 2s of the primary coil 2 is connected to the power supply side terminal 10bp via the high side switch element 5. A positive terminal BTP of the battery BT is connected to this power supply side terminal 10bp. On the other hand, the ground side terminal 2e of the primary coil 2 is connected (grounded) to the ground potential GND via the low side switch element 4. One end of the secondary coil 3 on the upper side in FIG. 2 is used as a positive electrode terminal 3p, and is connected to a positive discharge electrode Dp of the plasma reactor PR. On the other hand, the other end of the secondary coil 3 is made into a negative electrode terminal 3n, and is connected to the negative discharge electrode Dn of the plasma reactor PR.

In this embodiment, the primary coil voltage VL1 generated in the primary coil 2 takes a positive value when the power supply side terminal 2s has a high potential with respect to the ground side terminal 2e, and takes a negative value when the opposite occurs. shall be taken. Further, it is assumed that the primary coil current IL1 flowing through the primary coil 2 takes a positive value when flowing from the power supply side terminal 2s toward the grounding side terminal 2e, and takes a negative value when flowing in the opposite direction. Further, the secondary coil output voltage VL2 generated in the secondary coil 3 takes a positive value when the positive terminal 3p has a high potential with respect to the negative terminal 3n, and takes a negative value when the opposite occurs. .

In this embodiment, as shown in FIG. 2, the low-side switch element 4 is, for example, an enhancement type nMOSFET, whose drain terminal D is connected to the ground side terminal 2e of the primary coil 2, and whose source terminal S is connected to the ground potential GND. It is connected to the. On the other hand, the gate terminal G is connected to a low-side gate driver 12, and the low-side switch element 4 is turned on and off by a gate drive signal Slg from the low-side gate driver 12. Note that this low-side switch element 4 has a parasitic diode between its drain and source.

On the other hand, in this embodiment, the high-side switch element 5 is, for example, an enhancement type nMOSFET, as shown in FIG. It is connected to the positive terminal BTP of the battery BT through the power supply side terminal 10bp. On the other hand, the gate terminal G is connected to a high-side gate driver 13, and the high-side switch element 5 is turned on and off by a gate drive signal Shg from the high-side gate driver 13. Note that this high-side switch element 5 also has a parasitic diode between its drain and source.

The snubber capacitor 6 is electrically connected to the ground side terminal 2e and the power supply side terminal 2s of the primary coil 2, and is connected in parallel to the primary coil 2. Note that the snubber capacitor 6 may be composed of a plurality of capacitors connected in series or in parallel.

As described above, the element control section 11 includes the low side gate driver 12, the high side gate driver 13, the voltage detection section 14L, and the controller 15. The low-side gate driver 12 sends out a gate drive signal Slg to turn the low-side switch element 4 on and off according to instructions from the controller 15 . Further, the high-side gate driver 13 sends out a gate drive signal Shg to turn the low-side switch element 4 on and off according to instructions from the controller 15 . The voltage detection unit 14L detects the low-side voltage Vlds generated between the drain and source of the low-side switch element 4, and sends the value to the controller 15.
The controller 15, which will be described below, generates a low-side voltage bottom detection signal Sbd from the detected low-side voltage Vlds, which indicates whether or not this low-side voltage Vlds has become equal to or lower than the first threshold voltage Vth1 (bottom, for example, 20 V or lower). (See column (f) in FIG. 4). This first threshold voltage Vth1 is set to a predetermined value lower than the battery voltage Vs. Further, a second threshold voltage Vth2 to be compared with a high-side voltage Vhds, which will be described later, is set to a predetermined value lower than the battery voltage Vs.

The controller 15 includes a CPU, ROM, RAM, and logic circuit (not shown), and operates according to a predetermined program stored in advance. In driving the plasma reactor PR, this controller 15 functions as a charge control section 16, an alternating discharge control section 17, a high side off control section 18, and a regeneration control section 19, and is capable of executing these controls.

<Control of plasma reactor power supply>
Control of the plasma reactor power supply device 10 for operating the plasma reactor PR will be explained using the flowchart of FIG. 3 and the timing chart of FIG. 4. In this embodiment, under the control of the plasma reactor power supply device 10, a high voltage in the form of positive and negative pulse waves (see column (i) in FIG. 4) is repeatedly applied (for example, at a frequency of 100 kHz) to the plasma reactor PR. Positive and negative dielectric barrier discharges repeatedly occur in the plasma reactor PR.

First, let us consider a state in which the gate drive signal Shg of the high-side gate driver 13 is set to a high level by the controller 15 before time T1 (time T3, which will be described later), and the high-side switch element 5 is turned on ( (See column (a) in Figure 4). As a result, the high side voltage Vhds is set to approximately zero. However, at this point, since the low-side switch element 4 is turned off, the primary coil 2 is not energized.

Thereafter, in a charge step S1 (see FIG. 3), the controller 15 of the element control section 11 is made to function as the charge control section 16. That is, at time T1, the controller 15 sets the gate drive signal Slg of the low-side gate driver 12 to a high level, turning on the low-side switch element 4 (see column (b) in FIG. 4). Then, a primary coil current IL1 flows from the battery BT toward the ground potential GND through the high-side switch element 5, the primary coil 2 of the flyback step-up transformer 1, and the low-side switch element 4 (see column (c) in FIG. 4). ). Note that due to the inductance of the primary coil 2, the primary coil current IL1 becomes a positive current with a triangular wave pattern that increases with time. As a result, energy is charged (stored) in the primary coil 2.

Next, when a predetermined time has elapsed from the time T1 when the low-side switch element 4 was turned on (time T2), the controller 15 is caused to function as the alternating discharge control section 17 in an alternating discharge step S2 (see FIG. 3). That is, the controller 15 causes the gate drive signal Slg of the low-side gate driver 12 to be at a low level, and the low-side switch element 4 is forcibly turned off (see column (b) in FIG. 4). When the low-side switch element 4 is turned off at time T2, the primary coil current IL1 cannot flow. Therefore, immediately after time T2, the primary coil 2 generates a negative high voltage VL1 such that the ground terminal 2e has a higher potential than the power supply terminal 2s (see column (f) in FIG. 4). Therefore, the low-side voltage Vlds applied between the drain and source of the low-side switch element 4 has a large positive waveform (see column (e) in FIG. 4).

Note that the snubber capacitor 6 absorbs the surge voltage generated in the primary coil 2 after time T2 when the low-side switch element 4 is turned off, reduces overvoltage, and protects the low-side switch element and the high-side switch element. .

After time T2, the energy stored in the primary coil 2 is released, and the secondary coil output voltage VL2 is generated in a pulsed manner in the secondary coil 3 of the flyback step-up transformer 1 (Fig. 4(j) ) column).

As a result, in the plasma reactor PR connected to the secondary coil 3, a dielectric barrier discharge (positive electrode discharge) is generated in which the positive discharge electrode Dp side is set to a positive potential. Furthermore, due to the resonance between the capacitive plasma reactor PR and the secondary coil 3 and the resonance between the primary coil 2 and the snubber capacitor 6, as shown in column (j) of FIG. As the secondary coil output voltage VL2, an alternating voltage whose positive and negative values alternate is generated, although it is attenuated. As a result, in the plasma reactor PR, a positive discharge in which the positive discharge electrode Dp side is at a positive potential and, conversely, a negative discharge in which the positive discharge electrode Dp side is at a negative potential are alternately generated. In this embodiment, when the primary coil 2 is charged once from time T1 to time T2, the secondary coil output voltage VL2 changes to the positive side four times and to the negative side four times from time T2 to the next time T1. An example is shown in which a pulse with a waveform that swings three times is generated.

Furthermore, at the same time as the alternating discharge step S2 is started, the high side off step S3 is also executed, and the controller 15 is made to function as the high side off control section 18 (see FIG. 2). That is, in this embodiment, as shown in columns (a) and (b) of FIG. 4, the low-side switch element 4 is forcibly turned off at time T2, and at the same time, the high-side switch element 5 is also turned off.
At time T2, the high side voltage Vhds is 0V. That is, no voltage is applied between the drain and source of the high-side switch element 5 (see column (d) in FIG. 4). Therefore, the high-side switch element 5 is turned off by so-called soft switching, and the high-side switch element 5 can be turned off without causing a large loss.

As can be understood from the column (d) in FIG. 4, during the turn-off tolerance period P5 starting from time T2, a negative high primary coil voltage VL1 is generated in which the ground side terminal 2e has a higher potential than the power supply side terminal 2s. Since the primary coil current IL1 is not flowing, the high side voltage Vhds becomes almost zero. Therefore, the high side off step S3 can also be executed after the start of the alternating discharge step S2. That is, the high-side switch element 5 can also be turned off during this turn-off tolerance period P5 following time T2.

Next, in a regeneration step S4 (see FIG. 3), the controller 15 turns on the high-side switch element 5 after approximately a predetermined period has elapsed since the low-side switch element 4 was turned off at time T2 (time T3). Thereby, even after the turn-off permissible period P5 has elapsed, a period in which alternating positive and negative discharges are generated in the plasma reactor PR is ensured. Then, part of the energy still remaining in the secondary coil 3 and plasma reactor PR, and further in the primary coil 2 and snubber capacitor 6, is regenerated into the battery BT.

Specifically, the high-side switch-on prohibition signal Shoi (see column (i) in FIG. 4) generated within the controller 15 is controlled for a predetermined turn-on prohibition period P3 from time T2 (for example, in this embodiment, after time T2, The high-side switching element 5 is prohibited from turning on during this period P3. Thereby, at least during the turn-on inhibition period P3, alternating positive and negative discharges can be generated in the plasma reactor PR.

On the other hand, during a turn-on permissible period P4 from the end of the turn-on prohibited period P3 until the next time T2, the high-side switch element 5 is allowed to turn on. Therefore, in the present embodiment, at time T3 after the turn-on prohibition period P3 has elapsed and the turn-on permissible period P4 has started, the controller 15 sets the gate drive signal Shg of the high-side gate driver 13 to a high level, and the high-side switch element 5 is turned on (see column (a) in FIG. 4).

As a result, as shown in columns (c), (d), and (f) of FIG. 4, during the period after time T3 and before the next time T1, the primary coil voltage VL1 is set (higher than the battery voltage Vs). During the period from time T4 to T5 when a positive voltage is generated and the high-side voltage Vhds is supposed to take a positive value, a negative primary coil current IL1 flows toward the battery BT. In this way, energy can be regenerated toward the battery BT, and the energy efficiency of the plasma reactor power supply device 10 can be further improved. In addition, by sufficiently reducing the energy remaining in the primary coil 2, etc. in this way, vibrations in the primary coil voltage VL1 caused by the residual energy are suppressed, and the voltage applied to the primary coil 2 at the next time T1 to T2 is suppressed. There is also the advantage that energy charging can be carried out smoothly.
Note that, as shown in column (j) of FIG. 4, due to regeneration, the secondary coil output voltage VL2 generated between times T4 and T5 also becomes very small.

Moreover, in this embodiment, the regeneration step S4 (see FIG. 3) includes a soft-on step S4s in which the controller 15 functions as a soft-on control section 19s. Specifically, at time T3, after the turn-on prohibition period P3 has elapsed, the low-side voltage bottom detection signal Sbd (see column (g) in FIG. 4) obtained by detecting the low-side voltage Vlds by the voltage detection unit 14L becomes high level. The timing of the change from low level to low level is used. Note that this low-side voltage bottom detection signal Sbd is a signal that becomes high level when it is detected that the low-side voltage Vlds is equal to or lower than the first threshold voltage Vth1, which is lower than the battery voltage Vs.

As can be understood from FIGS. 2 and 4(d) and (e) columns, this is done from time T2 when both the low-side switch element 4 and the high-side switch element 5 are turned off. During the period up to T3 (see columns (a) and (b) in FIG. 4), the potential of the source terminal S of the low-side switch element 4 is originally fixed to the ground potential GND, while the potential of the drain terminal D is grounded. It is in a state of being disconnected from the potential GND. Similarly, in the high-side switch element 5, the potential of the source terminal S is originally fixed to the potential of the positive terminal BTP of the battery BT (for example, +12V), while the potential of the drain terminal D is separated from the potential of the positive terminal BTP. It is in a state of failure. Among them, as described above, a primary coil voltage VL1 (see column (f) in FIG. 4) which alternates between positive and negative is generated in the primary coil 2. Therefore, the period in which the positive low-side voltage Vlds is generated and the period in which the positive high-side voltage Vhds is generated are opposite periods.

Therefore, in this embodiment, when the low-side voltage bottom detection signal Sbd (see column (g) in FIG. 4) is at a high level, it not only indicates that the low-side voltage Vlds is equal to or lower than the first threshold voltage Vth1, but also indirectly This shows that the high-side voltage Vhds has a larger positive value than the second threshold voltage Vth2, which is lower than the battery voltage Vs. Conversely, when this signal Sbd is at a low level, it not only indicates that the low side voltage Vlds has a positive value greater than the first threshold voltage Vth1, but also indirectly indicates that the high side voltage Vhds has a positive value greater than the first threshold voltage Vth1. This indicates that the voltage is lower than the threshold voltage Vth2. Therefore, at the timing when the signal Sbd changes from high level to low level (for example, time T3), the high side voltage Vhds changes from a positive value larger than the second threshold voltage Vth2 to a value below the second threshold voltage Vth2. It also shows that the value has been reached.

Then, at time T3, after the turn-on inhibition period P3 has elapsed, the oscillating primary coil voltage VL1 changes from a positive value to a negative value, so that the high side voltage Vhds applied between the drain and source of the high side switch element 5 is the timing when the voltage changes from a positive value to approximately 0, which is equal to or lower than the second threshold voltage Vth2. That is, no voltage is applied between the drain and source of the high-side switch element 5 (see column (d) in FIG. 4). Therefore, the turn-on of the high-side switch element 5 at time T3 is so-called soft switching, and the high-side switch element 5 can be turned on without causing a large loss.

In this way, the controller 15 of the element control section 11 controls the high-side switch element 5 at time T3 when it detects that the high-side voltage Vhds indirectly detected by the voltage detection section 14L is equal to or lower than the second threshold voltage Vth2. It is also configured to be able to perform soft-on control to turn on the power. Thereby, when turning on the high-side switch element 5, switching loss in the high-side switch element 5 can be reduced, and energy efficiency can be further improved.
In the soft-on step S4s of the regeneration step S4, the high-side switch element 5 is turned on when the voltage detection section 14L indirectly detects that the high-side voltage Vhds is equal to or lower than the second threshold voltage Vth2. . That is, the high side switch element 5 is turned on by soft switching. Thereby, in turning on the high-side switch element 5 in the soft-on step S4s of the regeneration step S4, switching loss in the high-side switch element 5 can be reduced, and energy efficiency can be further improved.

In this embodiment, as shown in FIG. 4, the timing at which the low-side voltage bottom detection signal Sbd in the voltage detection section 14L changes from high level to low level is used as time T3.
However, for example, during the turn-on permissible period P4, after the low-side voltage bottom detection signal Sbd changes from a high level to a low level and continues to be at a low level for 1 μs, during the turn-on permissible period P4, , during a period in which it is detected that the high-side voltage Vhds indirectly detected by the voltage detection unit 14L is equal to or lower than the second threshold voltage Vth2 (that is, a period in which the low-side voltage bottom detection signal Sbd is at a low level). A soft-on control may be executed to turn on the high-side switch element 5 by setting an appropriate timing selected from the above as time T3.

After turning on the high side switch element 5 at time T3, the charging step S1 to the regeneration step S4 are repeated from the next time T1 onwards.

Note that when performing the charging step S1 again after performing the regeneration step S4, the low-side switch is turned on within the turn-on permissible period P2 after the cycle securing period P1 has elapsed from the time T1 when the low-side switch element 4 was previously turned on. The element 4 is turned on, a current IL1 is caused to flow through the primary coil 2, and energy charging is started.

Specifically, in the low-side switch-on permission signal Slop (see column (h) in FIG. 4) generated within the controller 15, a predetermined cycle period P1 (for example, 50 μs in this embodiment) is set from the previous time T1. After this, a turn-on tolerance period P2 (for example, 10 μs in this embodiment) is provided to allow the low-side switch element 4 to turn on. Then, at time T1 within the turn-on permissible period P2, the controller 15 sets the gate drive signal Slg of the low-side gate driver 12 to a high level to turn on the low-side switch element 4 (see column (b) in FIG. 4). By doing this, in the plasma reactor PR (see column (j) in FIG. 4), multiple positive and negative alternating discharges (a total of 5 times, 3 positive discharges and 2 negative discharges after time T2) are intermittently generated. The length of the resulting period can be set within a predetermined range (P1+P2, approximately 50 to 60 μs in this embodiment).

Moreover, in this embodiment, the charging step S1 (see FIG. 3) also includes a soft-on step S1s in which the controller 15 functions as a soft-on control section 16s. That is, during the turn-on permissible period P2, the low-side switch element 4 is turned on at the timing (time T1) when the low-side voltage bottom detection signal Sbd changes from low level to high level (see column (b) in FIG. 4).

This time T1 occurs between the drain and source of the low-side switch element 4 because the oscillating primary coil voltage VL1 (see column (f) in FIG. 4) changes from a negative value to a positive value during the turn-on permissible period P2. This is the timing when the low-side voltage Vlds applied to the voltage changes from a positive value to approximately 0, which is equal to or lower than the first threshold voltage Vth1. That is, no large voltage is applied between the drain and source of the low-side switch element 4 (see column (e) in FIG. 4). Therefore, when the low-side switch element 4 is turned on, so-called soft switching is performed, and the low-side switch element 4 can be turned on without causing a large loss.

In this manner, the controller 15 of the element control section 11 performs a soft-on operation that turns on the low-side switch element 4 at time T1 when it is detected that the low-side voltage Vlds detected by the voltage detection section 14L is equal to or lower than the first threshold voltage Vth1. It is configured so that it can also be controlled. Thereby, when turning on the low-side switch element 4, switching loss in the low-side switch element 4 can be reduced, and energy efficiency can be further improved.
Further, in the soft-on step S1s of the charge step S1, the low-side switch element 4 is turned on when the voltage detection section 14L detects that the low-side voltage Vlds is equal to or lower than the first threshold voltage Vth1. That is, the low side switch element 4 is turned on by soft switching. Thereby, when turning on the low-side switch element 4 in the charging step S1, switching loss in the low-side switch element 4 can be reduced, and energy efficiency can be further improved.

In this embodiment, the timing at which the low-side voltage bottom detection signal Sbd in the voltage detection section 14L changes from low level to high level is used as time T1.
However, for example, during the turn-on permissible period P2, after the low-side voltage bottom detection signal Sbd changes from a low level to a high level and continues to be at a high level for 1 μs, during the turn-on permissible period P2. , an appropriate period selected from the period during which it is detected that the low-side voltage Vlds detected by the voltage detection unit 14L is equal to or lower than the first threshold voltage Vth1 (that is, the period during which the low-side voltage bottom detection signal Sbd is at a high level). Soft-on control may be executed to turn on the low-side switch element 4 by setting the timing of 2 to time T1.

As explained above, in the plasma reactor power supply device 10 of this embodiment, in addition to the flyback step-up transformer 1, the low-side switch element 4, and the high-side switch element 5, the above-mentioned charge control, alternating discharge control, The device includes an element control section 11 configured to be able to repeatedly perform high side off control and regeneration control. Therefore, by charging the primary coil 2 with energy once, alternating positive and negative discharge can be caused in the plasma reactor PR multiple times. Furthermore, since a part of the energy can be regenerated to the battery BT, the plasma reactor power supply device 10 can have good energy efficiency.
Further, with this power supply device 10, by charging the primary coil 2 with energy once, it is possible to generate alternating positive and negative discharges multiple times in the plasma reactor PR. Furthermore, since a part of the energy can be regenerated into the battery, the plasma reactor power supply device can be controlled with good energy efficiency.

Although the present invention has been described above based on the embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and can be applied with appropriate modifications without departing from the gist thereof.
For example, in the embodiment, the voltage detection section 14L that detects the low side voltage Vlds is used. However, as shown by the broken line in FIG. 2, a voltage detection unit 14H that detects the high side voltage Vhds is used to obtain a high side voltage bottom detection signal, contrary to the embodiment. In addition to detecting the magnitude of the threshold voltage Vth2, it may also be used to indirectly detect the magnitude of the low-side voltage Vlds and the first threshold voltage Vth1. Further, by using both the voltage detecting section 14L and the voltage detecting section 14H, the voltage detecting section 14L obtains the low side voltage bottom detection signal Sbd in the same way as in the embodiment. At the same time, the magnitude of the high-side voltage Vhds and the second threshold voltage Vth2 may be detected by, for example, obtaining a high-side voltage bottom detection signal by the voltage detecting section 14H.

PR Plasma reactor GND Ground potential BT Battery (DC power supply)
Vs Battery voltage (DC power supply output voltage)
BTP (battery) positive terminal 10 Plasma reactor power supply 1 Flyback step-up transformer 2 (flyback step-up transformer) primary coil 2e (primary coil) ground terminal 2s (primary coil) power supply terminal 3 ( Secondary coil 3p (of flyback step-up transformer) Positive terminal 3n (of secondary coil) Negative terminal VL2 (of secondary coil) Secondary coil output voltage 4 Low-side switch element Vlds Low-side voltage 5 High-side switch element Vhds High-side voltage 6 Snubber capacitor 11 Element control section 14L Voltage detection section (low side voltage detection section)
14H Voltage detection section (high side voltage detection section)
Sbd Low-side voltage bottom detection signal 15 Controller 16 Charge control section 16S Soft-on control section Vth1 First threshold voltage 17 Alternating discharge control section 18 High-side off control section 19 Regeneration control section 19S Soft-on control section Vth2 Second threshold voltage S1 Charge step S1s Soft-on step S2 Alternate discharge step S3 High-side off step S4 Regeneration step S4s Soft-on step P5 Turn-off allowable period T1 to T5 Time

Claims (8)

a primary coil including a ground side terminal and a power side terminal, and
a flyback step-up transformer having a secondary coil connected to both ends of the plasma reactor;
a low side switch element connected between the ground side terminal of the primary coil and ground potential;
a high side switch element connected between the power supply side terminal of the primary coil and the positive terminal of the DC power supply;
A power supply device for a plasma reactor, comprising: an element control unit that controls on/off of the low-side switch element and the high-side switch element,
The element control section is
In a state where the above DC power supply and the above plasma reactor are connected,
Charge control for charging the primary coil with energy from the DC power supply by turning on the high-side switch element and the low-side switch element;
Alternating discharge control in which the low-side switch element is turned off and an alternating voltage that alternates between positive and negative is applied to the plasma reactor via the secondary coil to generate a discharge that alternates between positive and negative in the plasma reactor;
At the same time as the low-side switch element is turned off in the alternating discharge control, or immediately after the low-side switch element is turned off, a voltage is generated in the primary coil such that the ground side terminal has a higher potential than the power supply side terminal. high-side off control for turning off the high-side switch element within a turn-off tolerance period;
regeneration control that turns on the high-side switch element after the turn-off tolerance period and regenerates a portion of the energy remaining in the secondary coil and the plasma reactor to the DC power supply;
A power supply device for a plasma reactor that is configured to be able to run repeatedly. The plasma reactor power supply device according to claim 1,
A power supply device for a plasma reactor, comprising a snubber capacitor connected in parallel to the primary coil and electrically connected to the ground side terminal and the power supply side terminal of the primary coil. A power supply device for a plasma reactor according to claim 1 or claim 2,
a low-side voltage detection unit that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential;
comprising at least one of a high-side voltage detection unit that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive terminal of the DC power supply;
The element control section includes:
In the charge control after turning on the high side switch element in the regeneration control,
Soft-on control that turns on the low-side switch element when the low-side voltage detection section or the high-side voltage detection section detects that the low-side voltage is equal to or lower than a first threshold voltage lower than the output voltage of the DC power supply. of,
A power supply device for a plasma reactor configured to be executable. A power supply device for a plasma reactor according to any one of claims 1 to 3,
a low-side voltage detection unit that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential;
comprising at least one of a high-side voltage detection unit that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive terminal of the DC power supply;
The element control section includes:
In the regeneration control, when the low-side voltage detection section or the high-side voltage detection section detects that the high-side voltage is equal to or lower than a second threshold voltage lower than the output voltage of the DC power supply, the high-side switch Soft-on control that turns on the element,
A power supply device for a plasma reactor configured to be executable. a primary coil including a ground side terminal and a power side terminal, and
a flyback step-up transformer having a secondary coil connected to both ends of the plasma reactor;
a low side switch element connected between the ground side terminal of the primary coil and ground potential;
A method for controlling a power supply device for a plasma reactor, comprising: a high side switch element connected between the power supply side terminal of the primary coil and a positive terminal of a DC power supply,
In a state where the above DC power supply and the above plasma reactor are connected,
a charging step of charging the primary coil with energy from the DC power supply by turning on the high-side switch element and the low-side switch element;
an alternating discharge step of turning off the low-side switch element, applying an alternating voltage of alternating positive and negative to the plasma reactor via the secondary coil, and generating a discharge of alternating positive and negative in the plasma reactor;
A voltage is generated in the primary coil at the same time as the low-side switch element is turned off in the alternating discharge step, or immediately after the low-side switch element is turned off, such that the ground side terminal has a higher potential than the power supply side terminal. a high-side off step of turning off the high-side switch element within a turn-off tolerance period;
After the turn-off tolerance period, a regeneration step of turning on the high side switch element and regenerating a part of the energy remaining in the secondary coil and the plasma reactor to the DC power supply;
A control method for a plasma reactor power supply that repeatedly performs the following steps. A method for controlling a plasma reactor power supply device according to claim 5,
The plasma reactor power supply device includes:
A method for controlling a plasma reactor power supply device comprising a snubber capacitor connected in parallel with the primary coil and electrically connected to the ground side terminal and the power supply side terminal of the primary coil. A method for controlling a plasma reactor power supply device according to claim 5 or 6, comprising:
The plasma reactor power supply device includes:
a low-side voltage detection unit that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential;
comprising at least one of a high-side voltage detection unit that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive terminal of the DC power supply;
The charging step after turning on the high side switch element in the regeneration step includes:
A soft-on step of turning on the low-side switch element when the low-side voltage detection section or the high-side voltage detection section detects that the low-side voltage is equal to or lower than a first threshold voltage lower than the output voltage of the DC power supply. including,
A method of controlling a power supply device for a plasma reactor. A method for controlling a power supply device for a plasma reactor according to any one of claims 5 to 7, comprising:
The plasma reactor power supply device includes:
a low-side voltage detection unit that detects a low-side voltage that is a voltage of the ground-side terminal of the primary coil with respect to the ground potential;
comprising at least one of a high-side voltage detection unit that detects a high-side voltage that is a voltage of the power supply side terminal of the primary coil with respect to the positive terminal of the DC power supply;
The regeneration step includes:
Software that turns on the high-side switch element when the low-side voltage detection section or the high-side voltage detection section detects that the high-side voltage is equal to or lower than a second threshold voltage lower than the output voltage of the DC power supply. A method of controlling a power supply device for a plasma reactor including on-step.

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