JP2012005153A - Discharge circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge circuit for securely detecting occurrence of spark discharge.SOLUTION: In a waveform conversion circuit Mw, convergence time of a spark discharge signal is delayed by a delay operation by a circuit incorporated inside. When the spark discharge signal is recognized by a signal generating circuit COM, output of a PWM signal is regulated based on the spark discharge signal. In concrete explanation, the signal generating circuit COM permits the output of the PWM signal when the spark discharge signal is not input (voltage value of an input port P3 is High), and does not permit the output of the PWM signal when the spark signal is input (voltage value of the input port P3 is Low). In this processing, the generation period of the spark discharge signal is prolonged and the signal is easily detected in the signal generating circuit COM. Thus, the output of the PWM signal is securely regulated.

Description

  The present invention relates to a discharge circuit that removes particulates (hereinafter referred to as exhaust particulates) contained in exhaust gas of an internal combustion engine, and is particularly suitable for use in detecting the occurrence of spark discharge.

  Since a diesel engine compresses and burns a large amount of air together with fuel, exhaust gas contains exhaust particulates such as nitrogen oxides (so-called NOx) and soot (so-called particulates). Of these, particulates adversely affect the respiratory system of the human body, so the vehicle is equipped with a DPF (Diesel particulate filter) to reduce emissions of the particulates.

For example, in JP 2008-051037 A (Patent Document 1), DPF (Diesel particulate)
An exhaust gas treatment device applicable to filter) is introduced. The exhaust gas processing apparatus includes an exhaust pipe for introducing exhaust gas, an electrostatic agglomeration part (discharge part in claims) for charging particulates in the exhaust gas, and a honeycomb filter for adsorbing charged particulates And a heater for purifying the particulate adsorbed on the honeycomb filter by heat treatment.

  When the exhaust gas is supplied from the internal combustion engine, the exhaust gas processing apparatus charges the particulates in the exhaust gas by the electrostatic agglomeration portion to form the particulate clusters. Thereafter, the particulates are guided to the honeycomb filter and adsorbed on the surface of the filter. Thereafter, the particulate adsorbed on the filter is purified by the heat generated by the heater, and the exhaust gas that has passed through the DPF is reduced in the particulate content by this series of processes.

JP 2008-051037 A

  However, according to the technique of Patent Document 1, spark discharge may be generated in the internal structure of the DPF from the discharge electrode provided in the DPF. In this case, since the discharge current flows through the path of the spark discharge without passing through the substance in the exhaust gas, the particulates in the exhaust gas are not charged and the adsorption effect on the filter surface is reduced. For this reason, in the above-described DPF, when spark discharge occurs in the discharge electrode portion, there arises a problem that the purification action is remarkably lowered with the reduction of the adsorption effect.

  Even if it is attempted to detect a spark discharge using a shunt resistor, the generation period of the spark discharge is set to several microseconds (see FIG. 2a), so that it is very difficult to detect the spark discharge. FIG. 5 shows a DPF discharge circuit for detecting a discharge current. The discharge circuit 10 includes a battery power source Vb, a transformer TL, a rectifier circuit Dk, a smoothing capacitor Co, a discharge unit LD, a shunt resistor Ins1, a voltage dividing resistor Ins2, a current detection amplifier AMPs, a voltage detection amplifier AMPd, and a signal generation circuit COM. And a drive circuit DRV and a switching circuit Sw. In the discharge circuit 10, when the transformer TL is driven according to the operation of the switching circuit, charges are accumulated in the smoothing capacitor Co through the rectifier circuit Dk, and the discharge electrode of the discharge unit LD is caused by the output voltage of the smoothing capacitor. It will be discharged. At this time, a current detection signal is sent to the signal generation circuit COM by the shunt resistor Ins1 and the current detection amplifier AMPs, and a voltage detection signal is sent by the voltage dividing resistor Ins2 and the voltage detection amplifier AMPd. The signal generating circuit COM outputs a PWM signal based on the current detection signal and the voltage detection signal, and the drive circuit DRV drives the power transistors Tra and Trb based on the PWM signal.

  Here, when a spark discharge is generated in the discharge unit LD, the generation period of the spark discharge is set to several microseconds. Therefore, the waveform of the current detection signal input to the signal generation circuit COM is also very short, about several microseconds. It becomes a waveform. Furthermore, since the upper limit value of the waveform of the current detection signal is limited by the current detection amplifier AMPs, the pulse waveform is very short. When the signal generation circuit COM is constituted by a microcomputer or the like, such a current detection signal is processed as high-frequency noise, and it is hardly recognized that a spark discharge is generated. For this reason, in the discharge circuit 10 in the figure, there is a problem that the spark discharge cannot be detected even though the spark discharge is actually generated. Further, when such spark discharge is continuously generated, the filter unit is damaged and the power consumption of the battery is increased.

  In view of the above problems, an object of the present invention is to provide a discharge circuit that can reliably detect the occurrence of spark discharge.

In order to solve the above problems, the present invention has the following discharge circuit configuration. That is, a battery that supplies a DC voltage, a transformer that outputs a boosted voltage boosted with respect to the DC voltage, a switching circuit that drives the transformer according to an input control signal, and a smoothing that is smoothed with respect to the boosted voltage A smoothing capacitor that outputs a voltage; a discharge unit that applies the smoothing voltage to a discharge electrode to charge exhaust particulates in exhaust gas; and a current that is detected during discharge of the discharge electrode, and the value of the current is a current detection signal In a discharge circuit comprising a current detection circuit to be output as, and a control circuit that outputs the control signal based on at least the current detection signal and controls the switching circuit,
A waveform conversion circuit that detects the occurrence of a spark discharge according to the magnitude of the current detection signal and delays the convergence time of the spark discharge signal formed based on the current detection signal is provided.

  Preferably, the waveform conversion circuit outputs an internal signal in response to an input of a current detection signal corresponding to the spark discharge and a gate circuit that detects the occurrence of the spark discharge according to the magnitude of the current detection signal. An attenuation circuit that slowly attenuates the output value of the internal signal and a spark discharge notification circuit that outputs the spark discharge signal according to the internal signal are provided.

  In addition to the above-described configuration, the waveform conversion circuit includes a gate circuit that detects the occurrence of the spark discharge according to the magnitude of the current detection signal, and a first that corresponds to an input of a current detection signal corresponding to the spark discharge. An attenuation circuit that slowly attenuates the output value of the first internal signal, an internal signal conversion circuit that outputs a second internal signal based on the first internal signal, and the spark discharge A spark discharge notification circuit that outputs a signal in accordance with the second internal signal may be provided.

  In this case, more preferably, the internal signal conversion circuit includes a signal lengthening circuit that makes the output period of the second internal signal longer than the output period of the first internal signal.

  More preferably, a safety circuit is further provided for stopping the operation of the switching circuit during a period in which the spark discharge signal is output.

  More preferably, the control circuit is connected to the spark discharge notification circuit, and stops the output of the control signal according to the input of the spark discharge signal, and after the stop, Output is resumed.

  According to the discharge circuit of the present invention, when a spark discharge occurs, the convergence time of the current detection signal corresponding to the spark discharge is delayed, so that the generation of the spark discharge is surely recognized by a signal generation circuit composed of a microcomputer or other IC circuit. can do.

  In addition, since the drive circuit or the signal generation circuit can reliably recognize the occurrence of the spark discharge, it is possible to reliably stop the operation of the discharge unit during the spark discharge. In addition to this, by adding a process for resuming the operation of the discharge section after the spark discharge, the discharge circuit according to the present invention can temporarily stop the operation of the discharge section when a spark discharge occurs. By carrying out such a series of operations, in the discharge circuit, the adsorption action on the filter surface can be maintained, and the exhaust gas purification action can be suitably maintained.

1 is a diagram showing a configuration of a discharge circuit according to Embodiment 1. FIG. The figure which shows a discharge current and other waveforms. FIG. 6 is a diagram illustrating a configuration of a discharge circuit according to a second embodiment. FIG. 6 is a diagram illustrating a configuration of a discharge circuit according to a third embodiment. The figure which shows the structure of the discharge circuit which concerns on a prior art example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to Examples 1 to 3 and drawings corresponding to these Examples.

  FIG. 1 shows the configuration of a discharge circuit mounted on a vehicle. As shown in the figure, the discharge circuit 101 according to the present embodiment includes an in-vehicle battery Vb, a transformer TL, a switching circuit Sw, an output side rectifier circuit Dk, a smoothing capacitor Co, a discharge unit LD, a current detection circuit Ins1, a voltage detection circuit Ins2, and a current. It comprises a detection amplifier AMPs, a voltage detection amplifier AMPd, a waveform conversion circuit Mw, a signal generation circuit COM, and a drive circuit DRV.

  The in-vehicle battery Vb is mounted on an automobile driven by a diesel internal combustion engine, and supplies a DC voltage of 12V to 24V.

  The switching circuit Sw includes power transistors Tra and Trb, and drives the above-described transformer TL. Specifically, the power transistors Tra and Trb are alternately switched on / off. At this time, the path through which the battery current flows is “primary coil L1a → power transistor Tra → ground” or “secondary coil”. It is switched to any of “L1b → power transistor Trb → ground”.

  The transformer TL includes primary side coils L1a and L1b, a secondary side coil L2, and an iron core (including a ferrite core and the like) inserted through these coils. The anode terminal of the vehicle-mounted battery Vb is connected to the middle point of the primary coil. On the other hand, the power transistors constituting the switching circuit Sw are connected to the ends of the primary transformer. As shown in the figure, the input terminal of the output side rectifier circuit Dk is connected to the secondary coil L2. The transformer TL causes a change in magnetic flux in accordance with the switching operation of the switching circuit Sw, thereby boosting the DC voltage applied from the in-vehicle battery Vb, and outputting the boosted voltage by this operation.

  In the output side rectifier circuit Dk, capacitors Ca to Cd and diodes Da to Dd are wired in a grid pattern, and charges due to the boosted voltage are supplied to the smoothing capacitor Co.

  The smoothing capacitor Co first accumulates the supplied charge, thereby smoothing the boosted voltage by the transformer TL and outputting the smoothed voltage generated thereby. The smoothing voltage is about −15 kV, and is applied to the discharge electrode built in the subsequent discharge unit.

As described in the prior art, the discharge part LD according to the present embodiment is a DPE (Diesel) that purifies exhaust gas from a diesel internal combustion engine.
particulate filter). The discharge part LD is composed of a discharge electrode, a filter, and a heater. The discharge electrode is applied with a smooth voltage from the smoothing capacitor Co, and generates cations from molecules in the exhaust gas. When exhaust gas is supplied, the discharge electrode moves cations between the electrodes, collides the particulates (exhaust particulates in the claims) with the cations, and charges the particulates in the exhaust gas. Let When such a particulate is guided to the filter, the particulate is adsorbed on the filter surface in the filter, and the particulate disappears due to the combustion effect of the heater, thereby purifying the exhaust gas.

  The current detection circuit Ins1 detects a current generated when the discharge electrode is discharged (hereinafter referred to as a discharge current), and outputs a current detection signal proportional to the current value of the discharge current. In the present embodiment, a shunt resistor Rs is used, and the shunt resistor Rs is interposed in the low side line Lb. The current detection signal output from the shunt resistor Rs has a current value on the order of several amperes when a spark discharge occurs. In a normal discharge state such as a corona discharge, 1/10 to 1 at the time of the spark discharge. The current value is relatively small so as to be about / 100. The current detection circuit is not limited to the shunt resistor Rs as long as the circuit configuration detects the discharge current described above.

  As the high side line La, it is preferable to use a conductive cable made of carbon. As a result, the resistance value on the input side is adjusted to reduce noise. In order to provide a noise reduction function, a resistance element may be inserted in the high side line instead of the carbon conductive cable.

  An input terminal of the current detection amplifier AMPs is connected to the current detection circuit Ins1 and receives a current detection signal. The current detection amplifiers AMPs amplify and output the value of the input current detection signal within the range of the power supply voltage. The current detection signal also indicates a normal discharge state such as corona discharge and a short-circuit state such as spark discharge. However, when the current detection amplifier AMPs limits the output value to the power supply voltage Vk (V), the output of the current detection amplifier AMPs has an extremely short pulse waveform of about several microseconds at the time of spark discharge. The For this reason, it is difficult for the signal generation circuit COM at the subsequent stage to detect a spark signal based on the output signal from the current detection amplifier AMPs. In this embodiment, it is assumed that the power supply voltages Vk and Vj are stably supplied by a regulator (not shown), the power supply voltage Vk is 12 (V), and the power supply voltage Vj is 5 (V).

  The voltage detection circuit Ins2 is a voltage dividing resistor including resistors Rd1 and Rd2, and a voltage value at the middle point is output as a voltage detection signal. The input terminal of the voltage detection amplifier AMPd is connected to the voltage detection circuit Ins2 and receives a voltage detection signal. Even in the voltage detection amplifier AMPd, the value of the input voltage detection signal is amplified and output within the range of the power supply voltage.

  As shown in the figure, the waveform conversion circuit Mw according to this embodiment includes a gate circuit Mw1, an attenuation circuit Mw2, an internal signal conversion circuit Mw3, and a spark discharge notification circuit Mw4. The waveform conversion circuit Mw has a function of detecting the occurrence of spark discharge according to the magnitude of the current detection signal and delaying the convergence time of the spark discharge signal formed based on the current detection signal. Hereinafter, details of the waveform conversion circuit Mw will be described.

  The gate circuit Mw1 includes a Zener diode Zd, and the cathode of the Zener diode Zd is arranged in the direction of the current detection circuit Ins1. The Zener diode Zd uses an element having an appropriate Zener breakdown value, thereby allowing a current detection signal when a spark discharge is generated to pass and preventing a current detection signal from being normally discharged. For this reason, when a spark discharge occurs, the gate circuit Mw1 causes the current detection signal to pass through the Zener diode Zd, and drives the subsequent circuits Mw2 to Mw4. On the other hand, when the spark discharge does not occur, the gate circuit Mw1 does not pass the current detection signal, so that the subsequent circuits Mw2 to Mw4 are not driven. As described above, the gate circuit Mw1 has a function of detecting the occurrence of spark discharge according to the magnitude of the current detection signal. The gate circuit Mw1 according to the present embodiment is further provided with a diode D1. The diode D1 has a cathode disposed on the output side of the gate circuit Mw1.

  The attenuation circuit Mw2 has a function of outputting a first internal signal in response to an input of a current detection signal corresponding to spark discharge, and slowly attenuating the output value of the first internal signal. In the attenuation circuit Mw2 according to this embodiment, the capacitor C1 and the voltage dividing resistors R1 and R2 are connected in parallel, and the midpoint of the voltage dividing resistor is connected to the input portion of the internal signal conversion circuit Mw3. When the current detection signal is input from the gate circuit Mw1 to the attenuation circuit Mw2, the capacitor C1 is charged accordingly. As shown in FIG. 2A, the current detection signal is superimposed with a high-frequency waveform having a high amplitude during spark discharge. For this reason, the diode D1 described above is provided in the gate circuit Mw1, thereby preventing the backflow of accumulated charges in the capacitor C1. The attenuation circuit Mw2 outputs the first internal signal from the middle point of the voltage dividing resistor. The first internal signal slowly attenuates through the resistor after the capacitor C1 is charged.

  The internal signal conversion circuit Mw3 converts the voltage value of the first internal signal into an appropriate value based on the first internal signal applied to the input unit, and then converts the second internal signal from the output unit. Output. The internal signal conversion circuit Mw3 according to this embodiment is connected to a transistor T1 having an input portion as a base terminal, a transistor T2 that adjusts a passing current according to a collector voltage of the transistor T1, and an output side of the transistor T2. The voltage dividing resistors R7 and R8 are the main constituent elements. Among the constituent elements, the transistor T1 provided in the input section gradually attenuates the input first internal signal, and the collector voltage of the transistor T1 gradually attenuates accordingly. More specifically, as shown in FIG. 2B, the collector voltage falls in response to the generation of the first internal signal, and the saturated state is maintained when the first internal signal is greater than a certain value. Flow a large amount of through current. Thereafter, when the first internal signal is further attenuated, the collector voltage is also attenuated accordingly, and finally no passing current flows. In this embodiment, when the spark discharge occurrence period t1 is 5 to 10 (μsec), the collector voltage drop period t2 in the transistor T1 is set to 100 to 150 by appropriately setting each resistance value and capacitor capacity. (Msec) is set. Among these, the saturation period Tk of the transistor T1 is set to 5 to 10 (msec).

  Thus, when the collector voltage of the transistor T1 fluctuates, in the transistor T2, the base voltage decreases according to the collector voltage decrease period t2, and a passing current flows based on the power supply voltage Vk. At this time, the second internal signal is output by the passing current at the midpoint of the voltage dividing resistors R7 and R8. That is, in the internal signal conversion circuit Mw3 according to the present embodiment, the voltage value of the input first internal signal is converted into a second internal signal based on the power supply voltage Vk.

  The internal signal conversion circuit Mw3 preferably includes a signal lengthening circuit that makes the output period of the second internal signal longer than the output period of the first internal signal, as in this embodiment. More specifically, the signal extension circuit Mw3a according to the present embodiment includes a capacitor C2 and voltage dividing resistors R4 and R5 connected in parallel thereto. Among these, the middle point of the voltage dividing resistors R4 and R5 is connected to the middle point of the transistor T2, and the power supply voltage Vk is applied to the contact point between the resistor R4 and the capacitor C2. When the signal extension circuit Mw3a is incorporated in the internal signal conversion circuit Mw3, when the collector voltage of the other transistor T1 decreases, the voltage value of the base voltage of the transistor T2 is longer than the collector voltage decrease period t2. Will be reduced. For this reason, the passing time of the passing current in the transistor T2 is extended accordingly, and the output period of the second internal signal is also extended.

  The spark discharge notification circuit Mw4 is a circuit that generates a spark discharge signal based on the current detection signal. Specifically, the spark discharge notification circuit Mw4 outputs the spark discharge signal based on the second internal signal. The spark discharge notification circuit Mw4 in the present embodiment is composed of a resistor R12 and a transistor T3, and the voltage value is a logic level low state (hereinafter simply referred to as a low state) according to the output period of the second internal signal. Output a spark discharge signal. The spark discharge signal is delayed in the convergence time of the signal in proportion to the value of the signal. Here, when the signal extension circuit Mw3a is incorporated in the internal signal conversion circuit Mw3, the collector voltage of the transistor T3 is the resistance value when the collector voltage drop period t2 in the transistor T1 is 100 to 150 (μsec). And by setting the capacitor capacity appropriately, the decrease period t3 is set to be 200 to 300 (msec) (see FIG. 2c).

  The signal generation circuit (control circuit in claims) COM is a microcomputer for generating PWM signals in this embodiment. The signal generation circuit COM includes a CPU, an AD conversion circuit, a memory circuit, a clock circuit, and the like, and outputs PWM signals from the output ports P4 and P5 based on the signal values input to the AD ports P1 and P2 and the input port P3. (Control signal in claims) is output. More specifically, the memory circuit stores duty ratio information of a PWM signal to be output corresponding to the detection signal and the detection voltage. When the current detection signal and the voltage detection signal are input to the AD ports P1 and P2, the signal generation circuit COM extracts appropriate duty information from the memory circuit based on the input signal, and PWM based on this information Generate and output a signal. At this time, the drive circuit DRV amplifies the input PWM signal and drives the power transistors Tra and Trb. The drive circuit DRV amplifies the signal waveform based on the power supply voltage Vk.

  In the signal generation circuit COM, the input port P3 is connected to the output part of the spark discharge notification circuit Mw4, and a spark discharge signal is input to the input port P3 via the signal line Le. In the case of the present embodiment, when the spark discharge is not generated, the waveform conversion circuit Mw is not driven to the input port P3, so that a signal that becomes a logic level high state (hereinafter simply referred to as a high state) is applied. The On the other hand, when a spark discharge occurs, the waveform conversion circuit Mw is driven, so that a spark discharge signal whose voltage value is in a low state is applied. As described above, since the generation period of the spark discharge signal applied to the input port P3 is secured at least several tens (msec) or more, the signal generation circuit COM can recognize the spark discharge signal as a normal input signal. It becomes.

  The signal generation circuit COM performs output regulation of the PWM signal based on the spark discharge signal. Specifically, when the spark discharge signal is not input (the voltage value of the input port P3 is High), the signal generation circuit COM permits the output of the PWM signal and the spark signal is input ( The voltage value of the input port P3 is Low), and the output of the PWM signal is not permitted. In the signal generation circuit COM, since the generation period of the spark discharge signal is extended, the detection of the signal is facilitated, and the processing related to the output regulation of the PWM signal is reliably performed.

  As described above, according to the discharge circuit 101 according to the present embodiment, when a spark discharge occurs, the convergence timing of the current detection signal corresponding to the spark discharge is delayed, so that the signal control circuit COM including a microcomputer and other IC circuits sparks. It is possible to reliably recognize the occurrence of discharge.

  In addition, since the signal generation circuit can reliably recognize the occurrence of the spark discharge, it is possible to reliably stop the operation of the discharge unit LD during the spark discharge. In addition to this, by adding a process for resuming the operation of the discharge section after the spark discharge, the discharge circuit according to the present invention can temporarily stop the operation of the discharge section when a spark discharge occurs. By carrying out such a series of operations, in the discharge circuit, the adsorption action on the filter surface can be maintained, and the exhaust gas purification action can be suitably maintained.

  Furthermore, according to the discharge circuit 101 according to the present embodiment, since the occurrence of the spark discharge is reliably recognized by the signal generation circuit COM, the occurrence state of the spark discharge is not continued, and the life of the filter unit is increased. The power consumption of the battery can be reduced.

  FIG. 3 shows a modification of the discharge circuit according to the first embodiment. In addition, about the same structure part already demonstrated in Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the discharge circuit 102 according to this embodiment, a safety circuit for stopping the operation of the switching circuit is added. The safety circuit includes a spark discharge signal detection circuit Mw3b and a signal cut-off circuit SFC, and forcibly stops the operation of the switching circuit Sw according to the generation period of the spark discharge signal.

  In the case of the present embodiment, the spark discharge signal detection circuit Mw3b is incorporated in the internal signal conversion circuit Mw3. The spark signal detection circuit Mw3b includes a transistor T4 and resistors R9, R10, and R11, and a midpoint of the voltage dividing resistors R9 and R10 is connected to a base portion of the transistor T4. A predetermined potential is always applied to the collector of the transistor T4, and the signal cutoff circuit SFC is connected via the signal line Lf. The resistor R9 is connected to the output terminal of the transistor T2, and is wired so that a part of the passing current of the transistor T2 flows as the base current of the transistor T4.

  In the spark discharge signal detection circuit Mw3b, when the passing current is output from the transistor T2, the collector voltage of the transistor T4 decreases, and when the passing current stops from the transistor T2, the collector voltage of the transistor T4 increases. Thus, when the collector voltage of the transistor T4 is switched according to the passing current of the transistor T2, the period during which the collector voltage decreases substantially matches the output period of the second internal signal. For this reason, the period during which the collector voltage decreases is at least several tens (msec) or more, and is set to about 200 to 300 (msec) when the signal lengthening circuit Mw3a of this embodiment is incorporated.

  The signal cut-off circuit SFC detects the voltage value at the terminal a, cuts off the power supply to the drive circuit DRV when the applied voltage at the terminal a decreases, and predetermined when the applied voltage at the terminal a returns (increases). After a time, the power supply to the drive circuit DRV is resumed. That is, a time lag of a predetermined time is provided until the supply of the power supply voltage is resumed after the applied voltage at the terminal a is restored. Here, the voltage applied to the terminal a is controlled by the collector voltage of the transistor T4. That is, the signal cutoff circuit SFC outputs the passing current from the transistor T2 while the spark discharge signal is output from the spark discharge notification circuit Mw4, so that the applied voltage at the terminal a decreases, and the drive circuit DRV Stop signal output. On the other hand, when the output of the spark discharge signal stops, the applied voltage at the terminal a is restored (increased), and the signal output of the drive circuit DRV is restarted after a predetermined time has elapsed. The voltage signal applied to the terminal a of the signal cut-off circuit SFC is at least several tens (msec) or more corresponding to the period during which the spark discharge signal is generated. For this reason, the signal cut-off circuit SFC configured by an IC circuit, a transistor, or the like can recognize the fluctuation of the voltage signal, and the operation process whether or not to supply the power supply voltage Vk is reliably performed. It becomes.

  When a spark discharge occurs, the discharge circuit 102 having such a configuration outputs a spark discharge signal from the waveform conversion circuit Mw for a long period of time according to the magnitude of the discharge current. Then, during the period in which the spark discharge signal is output, the power supply to the drive circuit DRV is forcibly cut off by the safety circuit, and thereby the discharge operation in the discharge part LD is cut off temporarily. During the power-off period, signal processing based on the spark discharge signal is performed by the signal generation circuit COM. Examples of such signal processing include determination processing for determining whether or not the output of the PWM signal may be resumed. Such a process is performed within the time lag period described above, and the process related to restarting the output of the PWM signal is completed by the time the drive circuit DRV returns, and immediately after the drive circuit DRV returns, the signal generation circuit COM A signal can be output.

  That is, the discharge circuit 102 according to the present embodiment immediately stops driving of the drive circuit DRV based on the spark discharge signal output from the waveform conversion circuit Mw, and the signal generation circuit COM within the stop period of the drive circuit DRV. Complete signal processing. For this reason, when the power supply to the drive circuit DRV is resumed, the PWM signal correctly processed by the signal generation circuit COM is output.

  FIG. 4 shows a modification of the discharge circuit according to the first embodiment. Even in the present embodiment, the same components described above are denoted by the same reference numerals, and description thereof is omitted.

  As shown in the figure, the waveform conversion circuit Mw includes a gate circuit Mw1, an attenuation circuit Mw2, and a spark discharge notification circuit Mw4. That is, the waveform conversion circuit Mw according to the present embodiment has a configuration in which the internal signal conversion circuit Mw3 is omitted from the waveform conversion circuit Mw according to the first embodiment.

  When a spark discharge occurs, the waveform conversion circuit Mw according to the present embodiment detects the occurrence of the spark discharge by the gate circuit Mw1, and causes the attenuation circuit Mw2 to output an internal signal. As described above, the output period of the internal signal is prolonged according to the magnitude of the spark discharge, and thereby the generation period of the spark discharge signal output from the spark discharge notification circuit Mw4 is also prolonged.

  Even in the discharge circuit according to the present embodiment, since the signal prolonging action by the waveform conversion circuit Mw functions within a certain range, the effect of prolonging the generation period of the spark discharge signal can be expected. Therefore, the effect described in Example 1 is produced in that range. In the discharge circuit according to the present embodiment, the internal signal conversion circuit Mw provided in the first embodiment is omitted, so that the circuit configuration can be simplified.

  Although the embodiment according to the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical idea described in the claims. It is. For example, although the above-described embodiment is described as an apparatus used for a DPF for a vehicle, the present invention can be applied as a DPF apparatus for a diesel engine used in various fields. Specifically, the DPF according to the present invention can also be used in diesel engines for power generation equipment / construction machinery / ships and the like.

101 Discharge circuit Vb Battery TL Transformer Sw Switching circuit Co Smoothing capacitor LD Discharge part Ins1 Current detection circuit COM Signal generation circuit (control circuit)
Mw Waveform conversion circuit Mw1 Gate circuit Mw2 Attenuation circuit Mw3 Internal signal conversion circuit Mw4 Spark discharge notification circuit

Claims (6)

A battery that supplies a DC voltage, a transformer that outputs a boosted voltage boosted with respect to the DC voltage, a switching circuit that drives the transformer according to an input control signal, and a smoothed voltage that is smoothed with respect to the boosted voltage. A smoothing capacitor to be output; a discharge unit that applies the smoothing voltage to the discharge electrode to charge the exhaust particulates in the exhaust gas; and a current that is generated when the discharge electrode is discharged, and outputs the value of the current as a current detection signal In a discharge circuit comprising: a current detection circuit for controlling the switching circuit by outputting the control signal based on at least the current detection signal;
Discharge characterized by comprising a waveform conversion circuit that detects the occurrence of a spark discharge according to the magnitude of the current detection signal and delays the convergence time of the spark discharge signal formed based on the current detection signal. circuit.   The waveform conversion circuit outputs an internal signal in response to an input of a current detection signal corresponding to the spark discharge and a gate circuit that detects the occurrence of the spark discharge according to the magnitude of the current detection signal. The discharge circuit according to claim 1, further comprising: an attenuation circuit that slowly attenuates an output value of the spark discharge signal; and a spark discharge notification circuit that outputs the spark discharge signal according to the internal signal.   The waveform conversion circuit outputs a first internal signal in response to an input of a current detection signal corresponding to the spark discharge and a gate circuit that detects the occurrence of the spark discharge according to the magnitude of the current detection signal. An attenuation circuit for slowly attenuating the output value of the first internal signal; an internal signal conversion circuit for outputting a second internal signal based on the first internal signal; and the spark discharge signal for the second internal signal. The discharge circuit according to claim 1, further comprising a spark discharge notification circuit that outputs in response to an internal signal.   4. The internal signal conversion circuit includes a signal lengthening circuit that makes an output period of the second internal signal longer than an output period of the first internal signal. Discharge circuit.   5. The discharge circuit according to claim 1, further comprising a safety circuit that stops the operation of the switching circuit during a period in which the spark discharge signal is output.   The said control circuit stops the output of the said control signal according to the input of the said spark discharge signal, and restarts the output of the said control signal after the stop. Discharge circuit.

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