JP2005184888A - Pulse generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize supplying of a high-voltage pulse of, for example, 12 kV having abrupt rise time and a very narrow pulse width at a low DC power supply voltage, for example of, about 12 V with a simple circuit configuration, without using a plurality of semiconductor switches to which a high voltage is applied. <P>SOLUTION: A pulse generator 10 includes a high-voltage pulse generator 14, which converts the capacitive energy stored in a capacitor 20 into inductive energy by the switching operations of first and second semiconductor switches 26 and 28 to be outputted as high-voltage pulses, and a step-up chopper circuit 16 connected to the front stage of the high-voltage pulse generator 14, to supply the energy to the capacitor 20 of the high-voltage pulse generator 14 by a switching operation of the semiconductor switch 54. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention can supply a high voltage pulse having a very short rise time and a very narrow pulse width by releasing electromagnetic energy accumulated in an inductor from a low voltage DC power supply with a simple circuit configuration, and The present invention relates to a pulse generator that takes noise countermeasures into consideration.

  Recently, techniques for deodorization, sterilization, decomposition of harmful gases, etc. have been applied by plasma generated by high voltage pulse discharge, but in order to generate this plasma, the high voltage is extremely narrow. A pulse generator capable of supplying pulses is required.

  As shown in FIG. 7, a conventional pulse generator 100 includes a charging device 102 that generates a DC high voltage substantially equal to the peak value of a high voltage pulse, and a capacitor 104 that is charged with the DC high voltage from the charging device 102. In order to obtain a large withstand voltage, a switch 108 by a semiconductor element 106 such as a plurality of electrostatic induction thyristors (hereinafter referred to as SI thyristors) connected in series, and the capacitor 104 is charged by high-speed switching of the switch 108. And a load 110 to which a high DC voltage is supplied as a high voltage pulse (see, for example, Patent Document 1).

  A gate driving circuit 112 is connected to each semiconductor element 106 in order to turn on these semiconductor elements 106. In addition, a balancer resistor 114 is connected in parallel to the semiconductor element 106 in order to reduce the unbalance of the shared voltage of each semiconductor element 106 due to the impedance variation when each semiconductor element 106 is non-conductive.

  In other words, the pulse generator 100 is connected to a multi-series circuit 116 composed of a plurality of semiconductor elements 106 and balancer resistors 114 in series with the load 110.

  On the other hand, as shown in FIG. 8, the pulse generator 118 according to the proposed example turns on the semiconductor switch 126 to turn on the resistance 136 (resistance value R) from the DC power supply 120 (power supply voltage E) to each magnetic core 128. A current of approximately E / R flows through the primary winding of one turn → the semiconductor switch 126 → the DC power source 120.

  At this time, due to the transformer action of the magnetic core 128, the same magnitude of current also flows through the secondary winding of one turn of each magnetic core 128 via the gate-cathode of each semiconductor element 134. The element 134 is turned on at the same time (see, for example, Non-Patent Document 1).

Thus, since the semiconductor switch 126 and the series-connected semiconductor elements 134 is conductive, the voltage of approximately E is applied to the inductor 138, the current I _L is gradually increased linearly, storing electromagnetic energy in the inductor Is done.

When the current I _L flowing through the inductor 138 increases and the desired electromagnetic energy is accumulated, when the semiconductor switch 126 is turned off, the current flowing path of the inductor tends to be cut off. The induced voltage due to is generated in the reverse polarity.

  As a result, the diode 140 becomes conductive, and the inductor current continues to flow in the path of the inductor 138 → each semiconductor element 134 → the primary winding of each magnetic core 128 → the diode 140 → the inductor 138. At this time, the same current flows through the secondary winding of each magnetic core 128.

  That is, all of the current flowing into the anode of each semiconductor element 134 flows out to the gate, and no current flows to the cathode. This current flows until the charge accumulated in the semiconductor element 134 is released. In this state, a large voltage drop does not occur in the current path, and the time is extremely short. Therefore, the decrease in the inductor current is small, and the decrease in the electromagnetic energy in the inductor is also small.

  Along with the discharge of the electric charge, the semiconductor element 134 shifts to an off state, and a depletion layer is rapidly formed. The inductor current is charged with a small amount of electric capacity thereby, so that the voltage between the anode and the cathode is also steep. Stand up. Thus, the inductor voltage increases rapidly and the current decreases rapidly. In other words, the electromagnetic energy of the inductor is transferred to the anode-cathode capacitance of the semiconductor element 134 as electrostatic energy. Since this voltage is also supplied to the load 142, the electromagnetic energy of the inductor and the electrostatic energy due to the anode-cathode capacitance of the semiconductor element 134 are consumed by the load during this transition process.

  In the pulse generator 118, the DC power source 120 may be at a low voltage, and the semiconductor element 134 is turned on and off only by the secondary current of the magnetic core 128, eliminating the need for a gate drive circuit and simplifying the device. Is possible.

JP 2002-44965 A (FIGS. 3 and 4) IEEJ Plasma Society, No. PST-02-16 (Figure 1)

  However, the conventional pulse generator 100 shown in FIG. 7 has a complicated circuit configuration. Further, a high voltage is applied to all circuit components including the charging device 102. For this reason, it is necessary to perform high voltage insulation such as a large insulation distance. Accordingly, there is a problem that the pulse generator 100 is increased in size and cost.

  In addition, if only a part of the serially connected semiconductor elements 106 are turned on due to a malfunction, the remaining semiconductor elements 106 may be damaged due to application of overvoltage exceeding the rating. There is a problem that the operation of can not be expected.

  Further, since it is necessary to rapidly turn on the semiconductor element 106 in order to generate a pulse (10 kV / μsec or more) that rises extremely steeply, a shift in the application timing of the gate signal to the semiconductor element 106 and each semiconductor element Even if the deviation of the turn-on time of 106 is in the order of 2 ns or 3 ns, there is a problem that the transient voltage balance at the time of turn-on is greatly lost, and a series of semiconductor elements such as an ordinary inverter (about several hundred V / μsec) There are orders of magnitude more difficult than in the case of connection.

  On the other hand, in the pulse generator 118 according to the proposed example shown in FIG. 8, the DC power supply 120 may have a low voltage, and a voltage higher than the withstand voltage is applied to the semiconductor element 134 in the event of a turn-on malfunction. Although there has been no improvement at all in that respect, it is very difficult to prevent the transient voltage balance from being disturbed at the time of turn-off performed rapidly due to variations in the turn-off time of the semiconductor element 134. That is, the problem with the serial connection of a plurality of semiconductor elements still exists.

  Further, since a plurality of magnetic cores are arranged in the series circuit of the diode 140, the semiconductor switch 126 is caused by the physical distance due to this and the presence of inductance due to leakage between the finite primary winding and the secondary winding. It takes time to commutate the inductor current to the diode 140 due to the turn-off of the semiconductor element 134, the increase rate of the turn-off gate current of the semiconductor element 134 is suppressed, and a depletion layer is formed while the current flows to the cathode of the semiconductor element 134. It started to spread (turn-off gain became 1 or more), and there was a risk of becoming unstable at a sharp turn-off.

  The present invention has been made in consideration of such a problem, and without using a plurality of semiconductor switches to which a high voltage is applied, has a simple circuit configuration and a low DC power supply voltage of, for example, about 12V. An object of the present invention is to provide a pulse generator capable of supplying a high voltage pulse of, for example, 12 kV or more having a steep rise time and an extremely narrow pulse width.

  Another object of the present invention is to provide a pulse generator in consideration of noise countermeasures in addition to the above-mentioned matters.

  A pulse generator according to the present invention converts a capacitive energy accumulated in a capacitor into inductive energy by a switching operation and outputs it as a high voltage pulse, and a high voltage pulse generator before the high voltage pulse generator. And one or more step-up chopper circuits connected to supply energy to the capacitor by a switching operation.

  Usually, when a high voltage pulse of, for example, 10 kV to several tens of kV is output from a high voltage pulse generation circuit, several hundreds V is required as an input voltage of the high voltage pulse generation circuit.

  However, in the present invention, the boost chopper circuit is connected to the front stage of the high voltage pulse generation circuit so that energy is supplied to the capacitor of the high voltage pulse generation circuit through the boost chopper circuit. Even if the input voltage is set to a low voltage of, for example, 10 V to several tens of volts, the voltage across the capacitor in the high voltage pulse generating circuit can be set to, for example, about 100 V to several hundreds V. From the high voltage pulse generating circuit, for example, 10 kV to several A high voltage pulse of 10 kV can be output.

  Therefore, in the present invention, when a high voltage pulse is generated, a commercial power supply voltage (100 V or the like) to a general household or a car battery voltage (12 V or the like) can be used, which contributes to the spread of the pulse generator. Can be made.

  In the present invention, the high voltage pulse generation circuit includes a high voltage pulse semiconductor switch that performs the switching operation based on a control signal from an external high voltage pulse gate drive circuit, and the boost chopper The circuit includes a boosting semiconductor switch that performs the switching operation based on a control signal from an external boosting gate drive circuit, and the high-voltage pulse generation circuit and the boosting chopper circuit are individually shielded cases. And at least the high voltage pulse generation circuit and the boost chopper circuit may be connected by a coaxial cable.

  That is, a high voltage pulse gate drive circuit and a boost gate drive circuit, which are noise generation sources, are installed outside the high voltage pulse generation circuit and the boost chopper circuit, respectively. In addition, in order to suppress external noise contamination, the high voltage pulse generation circuit and the boost chopper circuit are housed in separate shield cases. Further, at least the high voltage pulse generation circuit and the boost chopper circuit are connected by a coaxial cable.

  As a result, the noise associated with the switching operation in the high voltage pulse generation circuit does not affect the boost chopper circuit, and the noise associated with the switching operation in the boost chopper circuit affects the high voltage pulse generation circuit. There is no such thing.

  In the above configuration, the output path from the high voltage pulse generation circuit to the load may be shielded by a coaxial cable. By using a coaxial cable, the pressure resistance is improved and long-distance power transmission is possible. Therefore, the load (discharge cell or the like) that is the largest source of noise can be kept away from the high voltage pulse generation circuit and the boost chopper circuit.

  In the present invention, the high voltage pulse generation circuit includes the capacitor, an inductor connected in series between both terminals of the capacitor, a first semiconductor switch, a second semiconductor switch, and the first semiconductor switch. And a diode having a cathode terminal connected to the other end of the inductor connected to the anode terminal of the first semiconductor switch and an anode terminal connected to the gate terminal of the first semiconductor switch.

  In this case, first, the first semiconductor switch is turned on by turning on the second semiconductor switch, the voltage across the capacitor is applied to the inductor, and inductive energy is accumulated in the inductor. Thereafter, when the second semiconductor switch is turned off, the first semiconductor switch is also turned off rapidly, so that a very narrow high voltage pulse that rises very steeply is generated in the inductor.

  Accordingly, a high voltage pulse having a steep rise time and an extremely narrow pulse width can be supplied with a simple circuit configuration without using a plurality of semiconductor switches to which a high voltage is applied.

  Note that a high voltage pulse is generated by the inductor, and a load that receives the supply of the high voltage pulse may be connected in parallel with the inductor or in parallel with the first semiconductor switch.

  Further, the present invention provides another boost chopper circuit connected to the preceding stage when one or more boost chopper circuits are connected between the high voltage pulse generation circuit and a DC power supply. Or a boosting capacitor that stores energy from the DC power source as capacitive energy, and a boosting inductor and a semiconductor switch connected in series between both terminals of the boosting capacitor, and the semiconductor switch The high voltage pulse generator circuit may be connected in parallel with the capacitor.

  In this case, inductive energy is stored in the boosting inductor by turning on the semiconductor switch, and the inductive energy stored in the boosting inductor is converted into a capacitor of the high voltage pulse generating circuit by turning off the semiconductor switch. Alternatively, the voltage may be supplied to a boosting capacitor of another boosting chopper circuit connected to the subsequent stage.

  As described above, according to the pulse generator of the present invention, a simple circuit configuration and a low DC power supply voltage of, for example, about 12 V can be used without using a plurality of semiconductor switches to which a high voltage is applied. For example, a high voltage pulse of 12 kV or more having a steep rise time and an extremely narrow pulse width can be supplied.

  Embodiments of the pulse generator according to the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, the pulse generator 10 according to the present embodiment includes a DC power source 12, a high voltage pulse generator circuit 14, and a booster connected between the DC power source 12 and the high voltage pulse generator circuit 14. And a chopper circuit 16.

  As shown in FIG. 2, the high voltage pulse generation circuit 14 includes a capacitor 20 to which the output voltage of the boost chopper circuit 16 in the previous stage is applied, and a part of the inductor 22 connected in series between both terminals of the capacitor 20. (Primary winding 24), the first semiconductor switch 26 and the second semiconductor switch 28, and a cathode terminal is connected to one end 30 of the primary winding 24 of the inductor 22, and the first semiconductor switch 26 A diode 32 having an anode terminal connected to the gate terminal G and a gate drive circuit 34 for controlling on / off of the second semiconductor switch 28.

  The inductor 22 includes the primary winding 24 and a secondary winding 36 which is not galvanically insulated from the primary winding 24 but is added to the primary winding 24 so as to be polarized. The output voltage Vout is taken out from between one end 38 of the secondary winding 36 and GND (ground).

Accordingly, when the number of turns of the primary winding 24 is N1, the number of turns of the secondary winding 36 is N2, and the voltage across the first semiconductor switch 26 is V _AG , the output voltage Vout is V _AG × (N1 + N2) / N1. In order to make the magnetic coupling between the primary winding 24 and the secondary winding 36 dense and to suppress the generation of leakage magnetic flux, the primary winding 24 and the secondary winding 36 are wound around the magnetic core. It is preferable to attach.

  As the second semiconductor switch 28, a self-extinguishing type or commutation-extinguishing type device can be used. In the first embodiment, a power metal in which an avalanche type diode 40 is built in reverse parallel is used. An oxide semiconductor field effect transistor (hereinafter referred to as a power MOSFET) 42 is used. The gate drive circuit 34 is connected to the gate terminal G and the source terminal S of the power MOSFET 42.

  As the first semiconductor switch 26, a current control type device, a self-extinguishing type device, or a commutation-extinguishing type device can be used. In this first embodiment, the rate of voltage increase (dv at turn-off) (dv) / Dt) is used, and SI thyristor 44 with a high voltage rating is used.

  On the other hand, the step-up chopper circuit 16 includes a step-up capacitor 50 to which the power supply voltage Vin of the DC power supply 12 (see FIG. 1) of the previous stage is applied, and a step-up inductor connected in series between both terminals of the step-up capacitor 50. 52, a semiconductor switch 54, and a gate drive circuit 56 for controlling the semiconductor switch 54 on / off. The semiconductor switch 54 is connected in parallel with the capacitor 20 of the high voltage pulse generation circuit 14.

  As the semiconductor switch 54, a self-extinguishing type or commutation-extinguishing type device can be used. In this embodiment, a power MOSFET 60 in which an avalanche type diode 58 is built in antiparallel is used. The gate drive circuit 56 is connected to the gate terminal G and the source terminal S of the power MOSFET 60.

  It is desirable to connect a diode 62 for preventing a backflow of current between the boost chopper circuit 16 and the high voltage pulse generation circuit 14 in the forward direction.

  In the pulse generator 10 according to this embodiment, as shown in FIG. 1, the circuit portion excluding the gate drive circuit 34 in the high voltage pulse generator 14 is housed in, for example, a metal shield case 64. Of the step-up chopper circuit 16, the circuit portion excluding the gate drive circuit 56 is housed in another shield case 66 made of metal, for example.

  The DC power supply 12 and the step-up chopper circuit 16 are connected by a coaxial cable 68, and the step-up chopper circuit 16 and the high voltage pulse generation circuit 14 are connected by a coaxial cable 70, so that the high voltage pulse generation circuit 14 and the high voltage pulse generation circuit 14 are connected to the high voltage pulse generation circuit 14. A coaxial cable 72 is connected to a load (discharge cell or the like) (not shown) connected to the output side of the voltage pulse generation circuit 14.

  Further, the power sources 74 and 76 of the gate drive circuits 34 and 56 use a power source different from the DC power source 12, and in this embodiment, dry batteries are used. The power supply voltages of the power supplies 74 and 76 were set to 12V, which is the same as the power supply voltage of the DC power supply 12, and the operating voltage was set to 12V.

  Next, the circuit operation of the pulse generator 10 according to this embodiment will be described with reference to the circuit diagram of FIG. 2 and the waveform diagrams of FIGS. 3A to 4E.

  First, at time t0, the control signal Vc1 is supplied between the gate and source of the power MOSFET 60 from the gate drive circuit 56 in the boost chopper circuit 16, and the power MOSFET 60 is turned on from off (see FIG. 3C). When the power MOSFET 60 is turned on, substantially the same voltage as the power supply voltage Vin (for example, 12V) of the DC power supply 12 is applied to the boosting inductor 52, and when the inductance of the boosting inductor 52 is L1, as shown in FIG. The current Ii flowing through the boosting inductor 52 increases linearly with the elapse of time at a gradient (Vi / L1).

  In the period To1 in which the power MOSFET 60 is on, the voltage Vr across the capacitor 20 of the high voltage pulse generation circuit 14 is maintained at 0V due to the rectification action of the diode 62.

The current Ii, current Ip1 at time t1 (= Vin · To1 / L1 ) becomes, the desired electromagnetic energy ^{(= L1 · (Ip1) 2} /2) is obtained, the control signal Vc1 from the gate drive circuit 56 Is stopped and the power MOSFET 60 is turned off (see FIG. 3C).

  When the power MOSFET 60 is turned off at the time t1, the output voltage of the boost chopper circuit 16 (the voltage across the power MOSFET 60) rises sharply due to the induced electromotive force generated in the boost inductor 52.

  At this time, the capacitor 20 of the high voltage pulse generation circuit 14 is rapidly charged until the voltage Vr between both ends reaches a predetermined voltage Vrp (for example, 200 V), and then the voltage value is maintained for a certain time. That is, the inductive energy stored in the boosting inductor 52 moves to the capacitor 20 of the high voltage pulse generation circuit 14 by turning off the power MOSFET 60 during the period To1 during which the power MOSFET 60 is on. It will be stored as capacitive energy.

  After that, at time t2, the control signal Vc2 is supplied from the gate drive circuit 34 between the gate and source of the power MOSFET 42, and the power MOSFET 42 is turned on from off (see FIG. 4E).

  At this time, the first semiconductor switch 26 is turned on by the electric field effect applied between the gate G and the cathode K due to the extremely large impedance of the reverse polarity of the diode 32. Since the rise of the anode current of the first semiconductor switch 26 is suppressed by the inductor 22, a normal turn-on is performed only by the field effect.

In this way, when the second semiconductor switch 28 and the first semiconductor switch 26 are turned on at time t2 (see FIG. 4D), the voltage Vrp across the capacitor 20 (see FIG. 3B) is applied to the inductor 22. When the inductance of the inductor 22 and L2, as shown in FIG. 4A, the current I _L of the inductor 22 increases linearly with time gradient (Vrp / L2).

When the power MOSFET42 is the To2 a period on, the current I _L, the current at the time t3, Ip2 (= Vrp · To2 / L2 ) , and the desired electromagnetic energy ^{(= L2 · (Ip2) 2} /2 Is obtained, the supply of the control signal Vc2 from the gate drive circuit 34 is stopped, and the power MOSFET 42 is turned off (see FIG. 4E).

At this time, if a floating inductance (not shown) other than the inductor 22 existing in the current I _L flow path is large, the power MOSFET 42 is not instantaneously cut off, and the current continues to flow slightly. When there is time, the output capacitance of the power MOSFET 42 is charged, and when the avalanche voltage of the diode 40 is reached, the diode 40 conducts with the avalanche voltage and generates a large loss. For this reason, the stray inductance is reduced as much as possible so that the diode 40 does not reach the avalanche and an almost ideal turn-off is performed.

When the power MOSFET 42 is turned off, the current from the cathode K of the first semiconductor switch 26 is also zero, that is, an open state, so that the current I _L flowing through the inductor 22 is cut off, and the inductor 22 has residual electromagnetic energy. by it to try to generate a reverse induction voltage, the diode 32 acts, the current I _L of the inductor 22, the anode of the gate G → diode 32 the anode a → first semiconductor switch 26 of the first semiconductor switch 26 → Commutates to the cathode path of the diode 32.

  In this case, it is necessary to consider that the stray inductance of the branch circuit in which the diode 32 exists is as low as possible and that commutation is completed in a short time. In the first semiconductor switch 26, electric charges are accumulated by the current that has flown until now, and until the electric charge becomes zero (storage period), the anode-gate of the first semiconductor switch 26 is in a conductive state. In order to maintain, the voltage drop of the said path | route is small.

Accordingly, since the reverse induced voltage V _L of the inductor 22 is suppressed to a sufficiently low value, there is almost no decrease in the current I _L within a short storage period (time T1 in FIG. 4A), but the time T1 is the first time. This is determined by the amount of charge drawn from the gate terminal G of the semiconductor switch 26. Therefore, abruptly flowing a possible large current, reduces the time the turn-off gain apparent as 1 below T1, it is as much as necessary to suppress the reduction of the current I _L in inductor 22.

  At time t4, the extraction of the charge accumulated in the first semiconductor switch 26 is completed, the depletion layer spreads from the cathode side and the gate side to the anode side, and a turn-off operation is started. The depletion layer has an amount determined by the built-in potential, so that the voltage applied to the junction increases, expands as the turn-off progresses, and finally reaches the vicinity of the anode.

Therefore, the electric capacity due to the depletion layer changes from a saturated state (conducting state) where many active charges exist to a small amount of electric capacity determined by the structure. A current due to the electromagnetic energy of the inductor 22 continues to flow from the anode to the gate, and charges the electric capacity of the depletion layer. This charging voltage, that is, the anode-gate voltage V _AG of the first semiconductor switch 26, increases at a relatively slow rate because of a large electric capacity at first, but rapidly increases as the depletion layer expands ( (See FIG. 4B).

When the current I _L becomes zero at the time point t5, as shown in FIGS. 4B and 4C, the voltages V _AG and V _L become maximum and become V _AP and V _LP , respectively. At this time, all the electromagnetic energy of the inductor 22 has shifted to the capacitance of the depletion layer of the first semiconductor switch 26.

Furthermore, this phenomenon are the resonant operation by the inductance and capacitance of the first semiconductor switch 26 of the inductor 22, the current I _L of the inductor 22 is substantially a cosine waveform, the anode of the first semiconductor switch 26 - gate The voltage V _AG has a sine waveform.

  Therefore, the width of the high voltage pulse generated between the inductor 22 and the secondary winding 36 and GND (ground) can be controlled by selecting the inductance value of the inductor 22 whose constant can be freely determined. That is, if the equivalent capacitance of the electric capacitance of the first semiconductor switch 26 is C, the pulse width Tp is

となる。

It becomes.

First charge stored in the capacitance of the depletion layer of the semiconductor switch 26 which is charged to the maximum value V _AP at time t5, due continuation of resonance, in the conducting state in the reverse direction by the inductor 22 and the accumulated charge diode 32 Discharge starts in the path of, and continues until the diode 32 reversely recovers and becomes non-conductive at time t6. If energy remains in the capacitance of the depletion layer of the inductor 22 and the first semiconductor switch 26 at the time t6, the current due to this energy is converted from the capacitor 20 → the diode 40 of the second semiconductor switch 28 → the first semiconductor. It flows through the path of the cathode K → the anode A of the switch 26.

  The time T4 during which the current flows in the capacitor 20 is a regenerative operation, and the energy remaining in the electric capacity of the depletion layer of the inductor 22 and the first semiconductor switch 26 is regenerated, which greatly contributes to the improvement of the operation efficiency. Therefore, it is important to shorten the reverse recovery time of the diode 32 as much as possible and to shorten the time T3.

  The above description is based on the assumption that a linear load such as a resistive load is connected between the secondary winding 36 and GND (ground). However, if the load is nonlinear such as a discharge gap, While the voltage rises, the load impedance suddenly decreases, and the subsequent waveform is different from those shown in FIGS. 4B and 4C. In this case, however, a pulse-like waveform having a narrower pulse width than the waveforms shown in FIGS. Become.

As described above, a high voltage pulse having a voltage Vout of V _AG × (N1 + N2) / N1 is output between one end 38 of the secondary winding 36 and GND.

  Usually, when a high voltage pulse of, for example, 10 kV to several tens of kV is output from the high voltage pulse generation circuit 14, several hundreds V is required as an input voltage of the high voltage pulse generation circuit 14.

  However, in this embodiment, the boost chopper circuit 16 is connected in front of the high voltage pulse generation circuit 14 so that energy is supplied to the capacitor 20 of the high voltage pulse generation circuit 14 through the boost chopper circuit 16. Therefore, even if the input voltage of the boost chopper circuit 16 is set to a low voltage of, for example, 10V to several tens of volts, the voltage across the capacitor 20 in the high voltage pulse generation circuit 14 can be set to, for example, about 100V to several hundreds of volts. The generation circuit 14 can output a high voltage pulse of 10 kV to several tens of kV, for example.

  Therefore, in this embodiment, when a high voltage pulse is generated, a commercial power supply voltage (100 V or the like) to a general household or a car battery voltage (12 V or the like) can be used. Can contribute to popularization.

  In particular, in this embodiment, a high voltage pulse gate drive circuit 34 and a boost gate drive circuit 56, which are noise sources, are provided outside the high voltage pulse generation circuit 14 and the boost chopper circuit 16, respectively. ing. Further, in order to suppress external noise, the high voltage pulse generation circuit 14 (circuit portion excluding the gate drive circuit 34) and the boost chopper circuit 16 (circuit portion excluding the gate drive circuit 56) are individually shielded. Cases 64 and 66 are accommodated. Further, at least the high voltage pulse generation circuit 14 and the boost chopper circuit 16 are connected by a coaxial cable 70.

  As a result, the noise associated with the switching operation in the high voltage pulse generation circuit 14 does not affect the boost chopper circuit 16, and the noise associated with the switching operation in the boost chopper circuit 16 does not affect the high voltage pulse generation circuit 14. It does not affect

  In addition, since the power sources 74 and 76 of the gate drive circuits 34 and 56 are different from the DC power source 12, noise from each gate drive circuit is not mixed into the boost chopper circuit or the like through the DC power source.

  Further, since the output path from the high voltage pulse generation circuit 14 to the load (not shown) is shielded by the coaxial cable 72, the withstand voltage characteristic of the output path is improved and long-distance power transmission is possible. . As a result, the load (discharge cell or the like) which is the largest noise generation source can be kept away from the high voltage pulse generation circuit 14 and the boost chopper circuit 16.

  Further, the operating voltage of the gate drive circuits 34 and 56 is set to 12V, and is set higher than 3.3V and 5V used in a normal logic circuit, so that it is less susceptible to noise. There is.

  Next, two modifications of the pulse generator 10 according to the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 5, the pulse generator 10 a according to the first modification includes an inductor 22, a primary winding 80, and a secondary winding that is magnetically coupled to the primary winding 80. 82 in that the transformer has 82.

In this case, when the number of turns of the primary winding 80 is N1, the number of turns of the secondary winding 82 is N2, and the voltage across the first semiconductor switch 26 is V _AG , the output voltage Vout is V _AG × N2 / N1. It becomes.

  As shown in FIG. 6, the pulse generator 10b according to the second modification includes two or more boost chopper circuits 16a, 16b, 16c,... Between the DC power supply 12 and the high voltage pulse generator circuit 14. The difference is that 16E is connected in cascade. In this case, diodes (not shown) are provided between the boost chopper circuits (between 16a and 16b, between 16b and 16c, and so on) and between the boost chopper circuit 16E at the final stage and the high voltage pulse generation circuit 14. Are preferably connected in the forward direction.

  In this case as well, although not shown in the drawing, portions of the boost chopper circuits 16a, 16b, 16c,..., 16E, except for the gate drive circuit, are housed in individual shield cases, and the gate drive of the high voltage pulse generation circuit 14 is performed. The portion excluding the circuit 34 is housed in a dedicated shield case. Further, the DC power source 12 and the first step-up booster chopper circuit 16a are connected by a coaxial cable, and the booster chopper circuits 16a, 16b, 16c,. The circuit 16E and the high voltage pulse generation circuit 14 are connected by a coaxial cable, and the output path of the high voltage pulse generation circuit 14 is shielded by the coaxial cable.

  In addition, the pulse generator according to the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

It is a block diagram which shows the pulse generator which concerns on this Embodiment. It is a circuit diagram which shows the structure of the pulse generator which concerns on this Embodiment. 3A to 3C are waveform diagrams showing the circuit operation of the pulse generator according to the present embodiment, in particular, the circuit operation of the boost chopper circuit. 4A to 4E are waveform diagrams showing the circuit operation of the pulse generation device according to the present embodiment, in particular, the circuit operation of the high voltage pulse generation circuit. It is a circuit diagram which shows the structure of the pulse generator which concerns on a 1st modification. It is a block diagram which shows the pulse generator which concerns on a 2nd modification. It is a figure which shows the pulse generator which concerns on a prior art. It is a figure which shows the pulse generator which concerns on a proposal example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a, 10b ... Pulse generator 12 ... DC power supply 14 ... High voltage pulse generator circuit 16 ... Boost chopper circuit 20 ... Capacitor 22 ... Inductor 26 ... First semiconductor switch 28 ... Second semiconductor switch 32 ... Diode 50 ... Boosting capacitor 52 ... Boosting inductor 54 ... Semiconductor switch 64, 66 ... Shield case 68, 70, 72 ... Coaxial cable 74, 76 ... Power supply (dry cell)

Claims (6)

  Capacitive energy stored in the capacitor is converted into inductive energy by a switching operation and output as a high voltage pulse, and is connected to the previous stage of the high voltage pulse generation circuit. One or more step-up chopper circuits for supplying energy. The pulse generator according to claim 1, wherein
The high voltage pulse generation circuit includes a high voltage pulse semiconductor switch that performs the switching operation based on a control signal from an external high voltage pulse gate drive circuit,
The step-up chopper circuit includes a step-up semiconductor switch that performs the switching operation based on a control signal from an external step-up gate drive circuit,
The high voltage pulse generation circuit and the boost chopper circuit are housed in separate shield cases, respectively.
At least the high voltage pulse generation circuit and the step-up chopper circuit are connected by a coaxial cable. The pulse generator according to claim 1, wherein
An output path from the high voltage pulse generation circuit to a load is shielded by a coaxial cable. In the pulse generator of any one of Claims 1-3,
The high voltage pulse generation circuit includes:
The capacitor;
An inductor, a first semiconductor switch and a second semiconductor switch connected in series between both terminals of the capacitor;
A diode having a cathode terminal connected to the other end of the inductor connected to the anode terminal of the first semiconductor switch, and an anode terminal connected to the gate terminal of the first semiconductor switch;
Inductive energy is stored in the inductor as the first semiconductor switch is turned on by turning on the second semiconductor switch.
The pulse generator according to claim 1, wherein the high voltage pulse is generated in the inductor when the first semiconductor switch is turned off by turning off the second semiconductor switch. In the pulse generator according to any one of claims 1 to 4,
When one or more boosting chopper circuits are connected between the high voltage pulse generation circuit and a DC power source,
The step-up chopper circuit is
A boosting capacitor for storing energy from another boosting chopper circuit connected to the previous stage or the DC power source as capacitive energy;
A boosting inductor and a semiconductor switch connected in series between both terminals of the boosting capacitor;
The semiconductor switch is connected in parallel with a capacitor of the high voltage pulse generation circuit,
Accumulation of inductive energy in the boost inductor accompanying conduction of the semiconductor switch is performed by turning on the semiconductor switch,
The inductive energy stored in the boost inductor is supplied to a capacitor of the high voltage pulse generation circuit or a boost capacitor of another boost chopper circuit connected to a subsequent stage by turning off the semiconductor switch. Pulse generator. The pulse generator according to claim 5, wherein
The pulse generator according to claim 1, wherein the DC power source is a battery power source of an automobile.

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