JP6602573B2 - Power supply for plasma reactor - Google Patents

Description

  The present invention relates to a power supply device for a plasma reactor that generates a voltage applied to the plasma reactor.

  Exhaust gas discharged from an engine, particularly a diesel engine, includes CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxide), PM (particulate matter), and the like.

  As a technique for removing PM contained in exhaust gas, a technique for removing PM contained in exhaust gas using a plasma reactor has been proposed. The plasma reactor includes a plurality of electrode panels. The electrode panel has, for example, a configuration in which an electrode is built in a dielectric, and the plurality of electrode panels are arranged to face each other with a gap in a direction orthogonal to the flow direction of the exhaust gas. When a pulse voltage is applied between the electrodes from the power supply device for the plasma reactor, dielectric barrier discharge occurs, low temperature plasma (non-equilibrium plasma) is generated between the electrode panels, and PM in the exhaust gas flowing between the electrode panels is Removed by oxidation.

  A high voltage of several kV is applied between the electrodes. This high voltage is generated by, for example, a flyback type step-up transformer built in the plasma reactor power supply device. A DC power source is connected to the primary side (primary coil) of the flyback type step-up transformer. When the voltage generated by the DC power supply is input to the primary side of the flyback type step-up transformer, a secondary voltage higher than the primary voltage is generated on the secondary side (secondary coil) due to mutual induction. Then, the secondary voltage is applied between the electrodes of the plasma reactor.

JP 2002-129949 A

  When the secondary side (output side) of the flyback type step-up transformer is opened due to a disconnection failure, inconveniences such as the need to consume energy stored in the primary coil of the flyback type step-up transformer on the primary side are prevented. In order to prevent a high voltage output from being applied to the open portion, it is desirable to stop energization from the DC power source to the primary coil of the flyback type step-up transformer thereafter.

  An object of the present invention is to provide a plasma reactor power supply device capable of stopping energization from a DC power supply to a primary coil of a flyback type step-up transformer when a disconnection failure occurs on the output side.

  In order to achieve the above object, a plasma reactor power supply apparatus according to the present invention is a plasma reactor power supply apparatus that generates a voltage to be applied to a plasma reactor, and includes a DC power supply, a flyback step-up transformer, A switching element that is turned on / off to switch energization / cutoff from the power source to the primary coil of the flyback type step-up transformer, a snubber capacitor connected in parallel with the switching element, and a voltage across the snubber capacitor are divided. A voltage dividing circuit, and an energization cutoff means for turning off the switching element and interrupting energization from the DC power source to the primary coil of the flyback type step-up transformer when the divided value by the voltage dividing circuit exceeds a predetermined value. Including.

  According to this configuration, when a disconnection failure occurs on the secondary side of the flyback type step-up transformer, that is, on the output side of the plasma reactor power supply device, the energy stored in the primary coil is not consumed by the discharge in the plasma reactor. Therefore, it is absorbed by the snubber capacitor connected in parallel with the switching element. This increases the voltage across the snubber capacitor. A voltage dividing circuit that divides the voltage between both ends of the snubber capacitor is provided. When the voltage between both ends of the snubber capacitor rises, the divided value by the voltage dividing circuit rises accordingly. Therefore, it can be determined that a disconnection failure has occurred on the output side when the divided voltage value by the voltage dividing circuit exceeds a predetermined value. When the divided voltage value by the voltage dividing circuit exceeds a predetermined value, the switching element is turned off and the energization from the DC power source to the primary coil of the flyback type step-up transformer is cut off.

  Therefore, when a disconnection failure occurs on the output side, energization from the DC power supply to the primary coil of the flyback step-up transformer can be stopped.

  In addition, the structure which provides the sensor which detects the voltage or electric current under a high voltage on the output side, and detects the disconnection failure on the output side based on the detected value of the sensor can be considered. However, since a sensor capable of detecting a voltage under a high voltage or a steep pulse current is expensive, the use of this configuration greatly increases the cost of the plasma reactor power supply device. On the other hand, in the configuration using the divided voltage value of the voltage across the snubber capacitor, which is a relatively low voltage, an expensive sensor is unnecessary, and the cost increase of the plasma reactor power supply device can be suppressed.

  The snubber capacitor may be composed of a single capacitor or may be composed of a series circuit of a plurality of capacitors.

  The voltage dividing circuit may include a circuit in which a plurality of resistors are connected in series.

  Further, when the snubber capacitor is configured by a series circuit of a plurality of capacitors, the voltage dividing circuit has a configuration in which a series circuit of a Zener diode and a resistor is connected in parallel to one of the plurality of capacitors. Also good.

  According to the present invention, energization from the DC power source to the primary coil of the flyback type step-up transformer can be stopped when a disconnection failure occurs on the output side. Further, an expensive sensor that can be used under a high voltage is unnecessary, and the cost increase of the plasma reactor power supply device can be suppressed.

It is sectional drawing which shows the structure of PM removal apparatus schematically. 1 is a circuit diagram illustrating a schematic configuration of a power supply device for a plasma reactor according to an embodiment of the present invention. It is a circuit diagram which shows schematic structure of the power supply apparatus 5 for plasma reactors where the snubber circuit and voltage dividing circuit of another structure were employ | adopted. It is a circuit diagram which shows the structure by which the energy consumption circuit was added to the power supply device for plasma reactors shown by FIG. It is a circuit diagram which shows the structure by which the energy consumption circuit was added to the power supply device for plasma reactors shown by FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<PM removal device>

  FIG. 1 is a cross-sectional view schematically showing the configuration of the PM removal device 1.

  The PM removal device 1 is a device for removing PM contained in exhaust gas discharged from an automobile engine (not shown), for example, and is interposed in the middle of an exhaust pipe 2 such as an exhaust pipe. The PM removal device 1 includes a flow tube 3, a plasma reactor 4, and a plasma reactor power supply device 5.

  The flow pipe 3 has a tubular shape (cylindrical shape) having an exhaust gas inlet 11 and an exhaust gas outlet 12 at one end and the other end, respectively. The exhaust gas inlet 11 is connected to the engine side portion 2A of the exhaust pipe 2, and the exhaust gas outlet 12 is connected to the portion 2B of the exhaust pipe 2 opposite to the engine side. The exhaust gas discharged from the engine flows through the engine side portion 2A of the exhaust pipe 2, flows into the flow pipe 3 from the exhaust gas inlet 11, flows through the flow pipe 3, and the engine in the exhaust pipe 2 from the exhaust gas outlet 12 It flows out to the part 2B on the opposite side.

  The plasma reactor 4 is disposed in the flow pipe 3. The plasma reactor 4 includes a plurality of electrode panels 21.

The electrode panel 21 has a rectangular plate shape and has a configuration in which the electrode 23 is built in the dielectric 22, in other words, a configuration in which the electrode 23 is sandwiched between the dielectrics 22 from both sides. An example of the material of the dielectric 22 is Al ₂ O ₃ (alumina). An example of the material of the electrode 23 is tungsten. The electrode panel 21 extends in the flow direction of the exhaust gas in the flow pipe 3 (the direction from the exhaust gas inlet 11 toward the exhaust gas outlet 12), and is arranged in parallel at equal intervals in a direction orthogonal to the flow direction of the exhaust gas. .

  A positive wiring 24 and a negative wiring 25 are alternately connected to the electrode 23 in order from one end side in the stacking direction of the dielectric 22. The plus wiring 24 and the minus wiring 25 are electrically connected to the plus terminal and the minus terminal of the plasma reactor power supply device 5, respectively.

<Power supply for plasma reactor>

  FIG. 2 is a circuit diagram showing a schematic configuration of the plasma reactor power supply device 5 according to one embodiment of the present invention.

  The plasma reactor power supply device 5 includes a DC power supply 31, a booster circuit 32, an input filter circuit 33, a snubber circuit 34, a voltage divider circuit 35, a failure detection circuit 36, a control circuit 37, and a gate drive circuit 38.

  The DC power source 31 is, for example, an in-vehicle battery that outputs a DC voltage of 12V.

  The booster circuit 32 includes a flyback boost transformer 41 and a switching element 42. A switching element 42 is connected to the primary coil 43 of the flyback step-up transformer 41, and a series circuit of the switching element 42 and the primary coil 43 is connected to the DC power supply 31 via the input filter circuit 33. Specifically, the switching element 42 is, for example, an IGBT (Insulated Gate Bipolar Transistor), the collector of which is connected to one end of the primary coil 43 of the flyback type step-up transformer 41, and the emitter of which is grounded. ing. The other end of the primary coil 43 is connected to the plus terminal of the DC power supply 31 via the input filter circuit 33.

  One end and the other end of the secondary coil 44 of the flyback step-up transformer 41 are electrically connected to the plus terminal and the minus terminal of the plasma reactor power supply device 5, respectively. Thereby, one end of the secondary coil 44 is connected to the electrode 23 of the plasma reactor 4 via the plus terminal and the plus wire 24, and the other end of the secondary coil 44 is connected to the electrode 23 via the minus terminal and the minus wire 25. It is connected to the.

  The input filter circuit 33 includes a capacitor for stabilizing the output voltage of the DC power supply 31.

  The snubber circuit 34 includes a capacitor 51 and is provided in parallel with the switching element 42. In other words, the capacitor 51 has one end electrically connected to the collector of the switching element 42 and the other end electrically connected to the emitter of the switching element 42, that is, grounded.

  The voltage dividing circuit 35 is a resistor series circuit in which two voltage dividing resistors 61 and 62 are connected in series. One end of the voltage dividing circuit 35 is electrically connected to the collector of the switching element 42, and the other end is electrically connected to the emitter of the switching element 42, that is, grounded. Thereby, the voltage dividing circuit 35 is connected in parallel with the switching element 42 and is connected in parallel with the snubber circuit 34.

  The failure detection circuit 36 is electrically connected to the connection point 63 of the voltage dividing resistors 61 and 62 of the voltage dividing circuit 35. Failure detection circuit 36 includes, for example, a comparator. The potential at the connection point 63 is input to the positive input terminal of the comparator. On the other hand, a predetermined voltage is input to the negative input terminal of the comparator. When the potential at the connection point 63 is equal to or lower than a predetermined voltage, a low level signal is output from the output terminal of the comparator. When the potential at the connection point 63 exceeds (exceeds) the predetermined voltage, a high level signal is output from the output terminal of the comparator. Is output.

  The control circuit 37 is an IC circuit. An output signal from the comparator of the failure detection circuit 36 is input to the control circuit 37 as a detection signal. When the detection signal is a low level signal, the control circuit 37 controls the gate voltage input from the gate drive circuit 38 to the gate of the switching element 42 by a normal operation. When a high level signal is input from the failure detection circuit 36 to the control circuit 37, the control circuit 37 stops normal operation. Since the normal operation is stopped, the switching element 42 is kept off thereafter. Further, in response to the input of the high level signal from the failure detection circuit 36, the control circuit 37 generates a disconnection failure on the output side of the plasma reactor power supply 5 (secondary side of the flyback step-up transformer 41). A disconnection failure occurrence signal is output. The disconnection failure occurrence signal output from the control circuit 37 is input to, for example, a meter ECU (Electronic Control Unit) mounted on the vehicle. The meter ECU turns on a warning light provided on the meter panel of the vehicle in response to the input of the disconnection failure occurrence signal.

  During normal operation of the control circuit 37, on / off of the switching element 42 is repeated at a constant cycle by controlling the gate voltage. When the switching element 42 is turned on, a current flows through the primary coil 43 of the flyback step-up transformer 41 and energy is accumulated in the primary coil 43. Thereafter, when the switching element 42 is turned off, the energy accumulated in the primary coil 43 is released, an electromotive force is generated in the primary coil 43, and the secondary coil 44 of the flyback step-up transformer 41 is in accordance with the turn ratio. A secondary voltage is generated. By repeating ON / OFF of the switching element 42, a secondary voltage is generated in a pulsed manner, and a secondary voltage (output voltage of the plasma reactor power supply device 5) that changes in a pulse waveform is generated between the electrodes 23 of the plasma reactor 4. To be applied. When the output voltage of the plasma reactor power supply 5 is applied between the electrodes 23, a dielectric barrier discharge is generated between the electrode panels 21 (see FIG. 1), and plasma is generated by the dielectric barrier discharge. Due to the generation of plasma, PM contained in the exhaust gas flowing between the electrode panels 21 is oxidized (burned) and removed.

  Further, when the switching element 42 is turned off, the capacitor 51 of the snubber circuit 34 is charged by a part of the energy released from the primary coil 43. By charging the capacitor 51, a transient high voltage (surge voltage) generated when the switching element 42 is turned off is suppressed from being applied to the switching element 42, and the switching element 42 is prevented from being destroyed by the high voltage. The

<Effect>

  When a disconnection failure occurs on the output side of the plasma reactor power supply device 5, the energy accumulated in the primary coil 43 of the flyback type step-up transformer 41 is not consumed by the discharge in the plasma reactor 4, so that it is in parallel with the switching element 42. It is absorbed by the capacitor 51 of the connected snubber circuit 34. As a result, the voltage across the capacitor 51 increases. When the voltage across the capacitor 51 increases, the potential at the connection point 63 of the voltage dividing resistors 61 and 62 of the voltage dividing circuit 35 increases accordingly. When the potential at the connection point 63 exceeds a predetermined voltage, the failure detection circuit 36 outputs a high level signal (high level detection signal). In response to the output of the high level signal, the normal operation by the control circuit 37 is stopped, and thereafter, the switching element 42 is kept off and the DC power source 31 to the primary coil 43 of the flyback type step-up transformer 41. Is turned off.

  Therefore, when a disconnection failure occurs on the output side of the plasma reactor power supply device 5, energization from the DC power supply 31 to the primary coil 43 of the flyback type step-up transformer 41 can be stopped.

<Other configuration of power supply for plasma reactor>

  FIG. 3 is a circuit diagram showing a schematic configuration of the plasma reactor power supply device 5 in which the snubber circuit 71 and the voltage dividing circuit 72 having different configurations are employed. In FIG. 3, parts corresponding to the parts shown in FIG. 2 are denoted by the same reference numerals as those parts. In the following description, the description of the parts with the same reference numerals is omitted.

  As shown in FIG. 3, the plasma reactor power supply 5 may employ a snubber circuit 71 and a voltage dividing circuit 72 instead of the snubber circuit 34 and the voltage dividing circuit 35 shown in FIG. 2.

  The snubber circuit 71 is constituted by a series circuit of two capacitors 73 and 74 and is provided in parallel with the switching element 42. Specifically, the two capacitors 73 and 74 are connected in series. One end of the series circuit of the capacitors 73 and 74 is electrically connected to the collector of the switching element 42, and the other end is electrically connected to the emitter of the switching element 42, that is, grounded. Thereby, the series circuit of the capacitors 73 and 74 is connected in parallel with the switching element 42.

  The voltage dividing circuit 72 is configured by a series circuit in which one end of a resistor 76 is connected to the anode of the Zener diode 75. The cathode of the Zener diode 75 is electrically connected to the connection point of the capacitors 73 and 74 of the snubber circuit 71. The other end of the resistor 76 is electrically connected to the emitter of the switching element 42, that is, grounded. Thereby, the voltage dividing circuit 72 is connected in parallel with the capacitor 73. The potential at the connection point 77 between the Zener diode 75 and the resistor 76 is input to the failure detection circuit 36.

  When a disconnection failure occurs on the output side of the plasma reactor power supply device 5, the energy accumulated in the primary coil 43 of the flyback type step-up transformer 41 is not consumed by the discharge in the plasma reactor 4, so that it is in parallel with the switching element 42. It is absorbed by the capacitors 73 and 74 of the connected snubber circuit 71. As a result, the voltage across the capacitor 73 increases. When the voltage between both ends of the capacitor 73 rises above the Zener voltage of the Zener diode 75, the Zener diode 75 is activated and a current flows through the resistor 76, whereby the potential (resistance) of the connection point 77 between the Zener diode 75 and the resistor 76 is increased. 76 voltage). When the potential at the connection point 77 exceeds a predetermined voltage, a high level signal is output from the failure detection circuit 36. In response to the output of the high level signal, the normal operation by the control circuit 37 is stopped, and thereafter, the switching element 42 is kept off and the DC power source 31 to the primary coil 43 of the flyback type step-up transformer 41. Is turned off.

  With this configuration as well, energization from the DC power source 31 to the primary coil 43 of the flyback step-up transformer 41 can be stopped when a disconnection failure occurs on the output side of the plasma reactor power supply device 5.

<Energy consumption circuit>

  FIG. 4 is a circuit diagram showing a configuration in which an energy consuming circuit 81 is added to the plasma reactor power supply device 5 shown in FIG.

  An energy consuming circuit 81 for consuming energy stored in the capacitor 51 of the snubber circuit 34 may be added to the plasma reactor power supply device 5 shown in FIG.

  The energy consuming circuit 81 is configured by a series circuit of a switching element 82 and a resistor 83. The switching element 82 is, for example, an IGBT. One end of the resistor 83 is electrically connected to the collector of the switching element 82. The other end of the resistor 83 is electrically connected to the collector of the switching element 42. The emitter of the switching element 82 is grounded.

  A detection signal of the failure detection circuit 36 (comparator) is input to the gate of the switching element 82.

  When a disconnection failure occurs on the output side of the plasma reactor power supply 5, the energy accumulated in the primary coil 43 of the flyback step-up transformer 41 is absorbed by the capacitor 51 of the snubber circuit 34. As the voltage between both ends of the capacitor 51 rises, the potential at the connection point 63 of the voltage dividing resistors 61 and 62 of the voltage dividing circuit 35 rises, and when the potential exceeds a predetermined voltage, the failure detection circuit 36 sets the high level. Detection signal is output. In response to the output of the detection signal, the normal operation by the control circuit 37 is stopped. Further, when a high-level detection signal is input to the gate of the switching element 82, the switching element 82 of the energy consumption circuit 81 is turned on, and the charge accumulated in the capacitor 51 flows through the energy consumption circuit 81. As a result, the energy stored in the capacitor 51 is converted into Joule heat by the resistor 83 of the energy consumption circuit 81 and consumed. Thereby, the energy accumulated in the capacitor 51 can be quickly lost. After the energy stored in the capacitor 51 is sufficiently lost, the switching element 82 is turned off.

  As shown in FIG. 5, the energy consuming circuit 81 may be added to the plasma reactor power supply device 5 in which the snubber circuit 71 and the voltage dividing circuit 72 are employed.

<Modification>

  As mentioned above, although embodiment of this invention was described, this invention can also be implemented with another form.

  For example, the switching elements 42 and 82 are not limited to IGBTs but may be MOSFETs.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

4 Plasma reactor 5 Power supply device for plasma reactor 31 DC power supply (DC power supply)
34 Snubber circuit (Snubber capacitor)
35 Voltage divider circuit 36 Fault detection circuit (energization interruption means)
37 Control circuit (energization interruption means)
38 Gate drive circuit (energization interruption means)
41 Flyback Step-up Transformer 42 Switching Element 43 Primary Coil 44 Secondary Coil 51 Capacitor (Snubber Capacitor)
71 Snubber circuit 72 Voltage divider circuit 73 Capacitor (Snubber capacitor)
74 Capacitor (Snubber Capacitor)

Claims (1)

A power supply device for a plasma reactor that generates a voltage applied to the plasma reactor,
DC power supply,
A flyback step-up transformer,
A switching element that is turned on / off to switch energization / cutoff from the DC power supply to the primary coil of the flyback step-up transformer;
A snubber capacitor connected in parallel with the switching element;
A voltage dividing circuit for dividing the voltage across the snubber capacitor;
An energization cut-off means for turning off the switching element to cut off energization from the DC power supply to the primary coil of the flyback step-up transformer when the divided voltage value by the voltage dividing circuit exceeds a predetermined value;
Is constituted by a series circuit of a resistor and a second switching element, by turning on the second switching element when the divided voltage value exceeds the predetermined value, the energy that consumes the energy stored in the snubber capacitor A power supply device for a plasma reactor, including a consumption circuit.

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