JP2012120436A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely stop discharge when a fault occurs.SOLUTION: In a power converter 200, when a terminal voltage of a capacitor measured by measuring circuits 317, 319 after energizing a switch 325 and starting the discharge of a capacitor 326 by a resistor 324 exceeds a preset voltage decline characteristic, a control circuit 319 stops the discharge of the capacitor 326 by the resistor 324 by cutting off the switch 325. Further, the control circuit 319 is set so as to determine the continuation or stop of the discharge based on comparison between the terminal voltage of the capacitor 326 measured by the measuring circuits 317, 319 and the voltage decline characteristic for two or more times at a predetermined time interval in a period until stopping the discharge of the capacitor 326 by the resistor 324 by cutting off the switch 325.

Description

  The present invention relates to a power converter that supplies a DC power source to a DC power source smoothing capacitor and an inverter via a switch.

An inverter used for driving a motor of a hybrid vehicle has a function of converting DC power supplied from a DC power source into AC power supplied to an AC electric load such as a rotating electrical machine, or AC power generated by the rotating electrical machine. Is converted to DC power for supplying to a DC power source. In order to perform these conversion functions, the inverter is equipped with a power conversion circuit using switching elements, and the power conversion from direct current power to alternating current power or from alternating current power to direct current power is performed by repeatedly switching on and off the switching elements. Do.
This inverter is provided with a large-capacity DC power supply smoothing capacitor that stabilizes voltage fluctuations of the DC power supply during operation. In addition, a disconnector such as a contactor is provided between the battery and the DC power supply smoothing capacitor. When the hybrid vehicle is driven, the contactor is closed (hereinafter referred to as ON) and the capacitor is charged, and then the inverter is connected. To drive the travel motor. On the other hand, when the hybrid vehicle is stopped, the contactor is opened (hereinafter referred to as “off”) to discharge the capacitor via the discharge circuit.
In order to determine the failure of the contactor and discharge circuit in the inverter, the terminal voltage of the capacitor for smoothing the DC power supply after the hybrid vehicle stopped was monitored, and the terminal voltage of the capacitor passed T1 time (40 seconds) after stopping. If it falls below the predetermined value at the time, it is determined that there is no abnormality, and if it falls below the predetermined value after a lapse of T2 time (5 minutes) after stopping, it is determined that there is an abnormality in the discharge circuit. A control device for an electric vehicle is known in which it is determined that there is an abnormality in the contactor if the contactor does not decrease after the T2 time has elapsed (see, for example, Patent Document 1 below).

JP-A-10-257778

  However, in the above-described conventional control device, when the contactor is turned on (closed) for some reason after the discharge of the capacitor by the discharge circuit is started after stopping, a large current continues to flow through the discharge circuit for a long time.

(1) The invention of claim 1 is a power converter for supplying a DC power supply to a DC power supply smoothing capacitor and an inverter through a switch, wherein the resistor discharges the capacitor charge, and the resistor is connected in series. A switch connected to and disconnecting the discharge current flowing from the capacitor to the resistor; a measuring circuit for measuring the terminal voltage of the capacitor; and a control circuit for controlling the switching on and off of the switch. When the capacitor terminal voltage measured by the measurement circuit after starting the discharging of the capacitor by energizing the resistor exceeds the preset voltage drop characteristic, the switch is turned off and the capacitor by the resistor is turned off. In addition, the control circuit cuts off the switch and stops the discharge of the capacitor by the resistor. Characterized in that it is set to perform a plurality of times at a predetermined time interval to continue or determination of stop of the discharge based on a comparison between the terminal voltage and the voltage drop characteristic of the measured condenser by measuring circuit.
(2) The invention according to claim 2 is the power conversion device according to claim 1, wherein the voltage drop characteristic is set according to a discharge characteristic of the capacitor by the resistor.
(3) The invention according to claim 3 is the power converter according to claim 2, wherein the control circuit is based on the terminal voltage of the capacitor before the start of discharge measured by the measurement circuit, the capacitance of the capacitor, and the resistance value of the resistor. The voltage drop characteristic is determined based on an exponential function using a determined time constant, and the continuation or stop of discharge is determined by comparing the voltage drop characteristic with the terminal voltage of the capacitor measured by the measurement circuit. To do.
(4) The invention of claim 4 is the power converter according to claim 3, wherein the control circuit includes a ratio of the terminal voltage of the capacitor measured this time to the terminal voltage of the capacitor previously measured by the measuring circuit, and the capacitor It is characterized in that it is determined whether the discharge is continued or stopped by comparing a coefficient set based on a time constant determined by the capacitance of the resistor and the resistance value of the resistor.
(5) The invention according to claim 5 is the power conversion device according to any one of claims 1 to 4, wherein the control circuit lengthens the time interval according to the elapsed time from the start of discharge. It is characterized by.
(6) The invention according to claim 6 is the power converter according to any one of claims 1 to 5, wherein the control circuit determines that the capacitor terminal voltage exceeds the voltage drop characteristic and discharges the capacitor by the resistor. When the operation is stopped, the discharge is not resumed until the first predetermined time has elapsed.
(7) The invention according to claim 7 is the power conversion device according to claim 6, wherein the control circuit is configured to perform the first predetermined stop when the discharge stop due to the terminal voltage of the capacitor exceeding the voltage drop characteristic is the first time. Waiting for the resumption of discharge until the second predetermined time shorter than the time elapses, and, when the discharge is stopped for the second time or later, waiting for the resumption of discharge until the first predetermined time elapses.
(8) The invention of claim 8 is the power conversion device according to any one of claims 1 to 7, wherein the switch includes a first switch and a second switch connected in series, and the first switch is short-circuited. A detection circuit for detecting the occurrence of a failure is provided, and the control circuit normally starts and stops the discharge by energizing and shutting off the first switch while the second switch is energized. When the occurrence of a short circuit failure in the first switch is detected, the second switch is shut off to stop discharging.
(9) The invention according to claim 9 is the power converter according to any one of claims 1 to 8, wherein the resistor includes a first resistor having a first resistance value and a first resistance value. A second switch having a second resistance value lower than the third resistor, and the switch is connected in series with the first resistor, and a third switch for energizing and interrupting a discharge current flowing from the capacitor to the first resistor; And a fourth switch connected in series with the second resistor to conduct and cut off the discharge current flowing from the capacitor to the second resistor. The control circuit energizes the third switch to When discharging of the capacitor is started and the terminal voltage of the capacitor measured by the measurement circuit falls below a predetermined voltage, in addition to discharging the capacitor by the first resistor, the fourth switch is energized and the capacitor is discharged by the second resistor. Release Characterized in that it starts to.

  According to the present invention, even when the switch is closed (turned on) for some reason during the discharge of the capacitor by the resistor, the discharge of the capacitor by the resistor is surely stopped, and the discharge current continues to flow through the resistor. Can be prevented.

Diagram showing control block of hybrid vehicle Electric circuit diagram of the inverter device The figure which shows the electric circuit structure of the discharge control circuit 300 of the capacitor | condenser 326 for DC power supply smoothing of one Embodiment Timing chart showing operation of each part of discharge control circuit 300 when normal discharge is performed Timing chart showing protection operation of discharge control circuit 300 when contactor 304 is turned on (closed) for some reason during discharge PAD showing protection operation by microcomputer 319 of discharge control circuit 300 PAD showing a modified example of the protection operation shown in FIG. PAD showing another embodiment of protection operation by microcomputer 319 of discharge control circuit 300 Timing chart showing the discharge protection operation when the contactor 304 is in the on (closed) state when receiving the discharge command signal Timing chart showing another embodiment of the discharge protection operation when the contactor 304 is in a closed state at the time of receiving the discharge command signal Discharge circuit diagram of an embodiment in which the second switching element 1101 is connected in series with the switching element 325 to back up the short mode failure of the first switching element 325 Discharge circuit diagram of an embodiment in which the discharge time is shortened by lowering the resistance value of the discharge resistor when the voltage V gradually decreases. The figure which shows the discharge waveform of the discharge circuit shown in FIG. Internal circuit diagram of buffer 323 of discharge control circuit 300 Internal circuit diagram of collector voltage detection circuit 322 of discharge control circuit 300

  An embodiment of the invention in which the present invention is applied to an inverter for driving a motor of a hybrid vehicle will be described. The discharge circuit of the DC power supply smoothing capacitor of the present invention is not limited to an inverter for driving a motor of a hybrid vehicle, but is used in an electric vehicle, a ship, an aircraft, etc. as well as an inverter used in a general electric vehicle. It is also applied to power converters such as inverters and DC-DC converters, all power converters widely used for general industry, or electric power converters for electric motors that drive household solar power generation systems and household appliances Thus, the same effects as those obtained when applied to an inverter according to an embodiment described later can be obtained.

  FIG. 1 is a diagram showing a control block of a hybrid vehicle. 2. Description of the Related Art An electric power conversion device for an electric system mounted on an automobile, particularly an inverter used in an electric system for driving a vehicle, is placed in a severe ambient environment or an operating environment. The vehicle drive inverter converts the DC power supplied from the in-vehicle battery or the in-vehicle power generation device into AC power, and supplies the AC power to the AC motor for driving the vehicle to drive, while the AC generated by the AC motor for driving the vehicle. The power is converted back to DC power, and the DC power is supplied to the in-vehicle battery for charging.

  In FIG. 1, a hybrid electric vehicle (hereinafter referred to as HEV) 110 is one electric vehicle and includes two vehicle driving systems. One of them is an engine system using an engine (ENG) 120 which is an internal combustion engine as a power source. This engine system is mainly used as a drive source for the HEV 110. The other one is an in-vehicle electric system using motor generators (MG1, MG2) 192, 194 as a power source. This in-vehicle electric system is mainly used as a drive source for HEV 110 and a power generation source for HEV 110. The motor generators 192 and 194 are, for example, synchronous machines or induction machines, and operate as both a motor and a generator depending on the operation method, and are therefore referred to as a motor generator in this specification.

  A front wheel axle 114 is rotatably supported at the front portion of the vehicle body, and a pair of front wheels 112 are provided at both ends of the front wheel axle 114. On the other hand, a rear wheel axle (not shown) is rotatably supported at the rear portion of the vehicle body, and a pair of rear wheels (not shown) are provided at both ends of the rear wheel axle. The HEV 110 of this embodiment employs a so-called front wheel drive system in which the main wheel driven by power is the front wheel 112 and the driven wheel to be driven is the rear wheel (not shown). The present invention can also be applied to a rear-wheel drive HEV.

  A front wheel side differential gear (hereinafter referred to as front wheel side DEF) 116 is provided at the center of the front wheel axle 114. The front wheel axle 114 is mechanically connected to the output side of the front wheel side DEF 116. Further, the output shaft of the transmission 118 is mechanically connected to the input side of the front wheel side DEF 116. The front wheel side DEF 116 is a differential power distribution mechanism that distributes the rotational driving force that is shifted and transmitted by the transmission (T / M) 118 to the left and right front wheel axles 114. The output side of the motor generator 192 is mechanically connected to the input side of the transmission 118. Further, the output side of the engine 120 and the output side of the motor generator 194 are mechanically connected to the input side of the motor generator 192 via the power distribution mechanism 122. Motor generators 192 and 194 and power distribution mechanism 122 are housed inside the casing of transmission 118.

  The motor generators 192 and 194 are synchronous machines having permanent magnets on the rotor, and the AC power supplied to the armature windings of the stator is controlled by the inverter devices (INV1, INV2) 140, 142. Drive control of the generators 192 and 194 is performed. A battery (BAT) 136 is electrically connected to the inverter devices 140 and 142, and power is exchanged between the battery 136 and the inverter devices 140 and 142.

  The HEV 110 of this embodiment includes two sets of motor generator units, a first motor generator unit composed of a motor generator 192 and an inverter device 140, and a second motor generator unit composed of a motor generator 194 and an inverter device 142, Use them properly according to the driving conditions. That is, in the case where the vehicle is driven by the power from the engine 120, when assisting the driving torque of the vehicle, the second motor generator unit is operated as a power generation unit by the power of the engine 120, and is obtained by the power generation. The first motor generator unit is operated as an electric unit using electric power. Further, in the same case, when assisting the vehicle speed of the vehicle, the first motor generator unit is generated as a power generation unit by the power of the engine 120, and the second motor generator unit is electrically driven using the electric power obtained by the power generation. Operate as a unit.

  In the HEV 110 of this embodiment, the first motor generator unit is operated as an electric unit using the electric power of the battery 136, and the vehicle can be driven only by the power of the motor generator 192. Furthermore, in the HEV 110 of this embodiment, the battery 136 can be charged by operating the first motor generator unit or the second motor generator unit as a power generator unit by the power of the engine 120 or the power from the wheels.

  The battery 136 is also used as a power source for driving the auxiliary motor (M) 195. Auxiliary machines include, for example, a motor that drives a compressor of an air conditioner or a motor that drives a hydraulic pump for control. DC power is supplied from the battery 136 to the inverter device (INV3) 43, and the inverter device 43 receives AC power. And is supplied to the motor 195. The auxiliary inverter device 43 has the same function as the vehicle driving inverter devices 140 and 142, and controls the phase, frequency, and power of alternating current supplied to the motor 195. For example, the motor 195 generates torque by supplying AC power having a leading phase with respect to the rotation of the rotor of the motor 195. On the other hand, by generating the delayed phase AC power, the motor 195 operates as a generator, and the motor 195 enters a regenerative braking operation. The control function of the inverter device 43 is the same as the control function of the inverter devices 140 and 142. Since the capacity of the motor 195 is smaller than that of the motor generators 192 and 194, the maximum conversion power of the inverter device 43 is smaller than that of the inverter devices 140 and 142. However, the circuit configuration of the inverter device 43 is basically the circuit of the inverter devices 140 and 142. Same as the configuration.

  The capacitor 326 is for direct current power supply smoothing, and a small-capacitance capacitor is connected in parallel or in series to form a large-capacity capacitor module. In this specification, it is represented as a single capacitor. The capacitor 326 is in an electrical close relationship with the inverter devices 140 and 142 and the inverter device 43, and further has a common point that measures against heat generation are necessary. In addition, it is desired to reduce the volume of the apparatus as much as possible. From these points, the power conversion device described in detail below includes the inverter devices 140 and 142, the inverter device 43, and the capacitor 326 in the casing of the power conversion device. With such a configuration, a small and highly reliable device can be realized.

  Further, by incorporating the inverter devices 140 and 142, the inverter device 43, and the capacitor 326 in one housing, there are effects in simplification of wiring and noise countermeasures. Furthermore, the inductance of the connection circuit between the capacitor 326, the inverter devices 140 and 142, and the inverter device 43 can be reduced, whereby the generation of spike voltage can be suppressed, and heat generation can be reduced and heat radiation efficiency can be improved.

  FIG. 2 shows an electric circuit diagram of the inverter device. The electric circuit configuration of the inverter devices 140 and 142 and the inverter device 43 will be described with reference to FIG. Since the inverter devices 140, 142, and 43 all have the same circuit configuration and the same operation and function, the inverter device 140 will be described as a representative here.

  The power conversion device 200 includes an inverter device 140 and a capacitor 326, and the inverter device 140 includes an inverter circuit 144 and a motor controller 170. The inverter circuit 144 includes a plurality of upper and lower arm series circuits 150 (in the example of FIG. 2) including an IGBT (insulated gate bipolar transistor) 328 and a diode 156 that operate as an upper arm, and an IGBT 330 and a diode 166 that operate as a lower arm. Three upper and lower arm series circuits 150), connected to an AC power line (AC bus bar) 186 from the intermediate electrode 169 of each upper and lower arm series circuit 150 via an AC terminal 159, and further to the motor generator 192 via the AC power line 186. Connected. The motor controller 170 includes a driver circuit 174 that drives and controls the inverter circuit 144 and a control circuit 172 that supplies a control signal to the driver circuit 174 via a signal line 176.

  The IGBTs 328 and 330 of the upper arm and the lower arm are switching power semiconductor elements, which are operated by a drive signal from the motor controller 170, and convert DC power supplied from the battery 136 into three-phase AC power. The converted electric power is supplied to the armature winding of the motor generator 192. The inverter circuit 144 is configured by a three-phase bridge circuit, and the upper and lower arm series circuits 150 for three phases are electrically connected in parallel between the DC positive terminal 314 and the DC negative terminal 316, respectively. The terminal 314 and the DC negative terminal 316 are connected to the positive side and the negative side of the battery 136.

  The IGBTs 328 and 330 include collector electrodes 153 and 163, emitter electrodes (signal emitter electrode terminals 155 and 165), and gate electrodes (gate electrode terminals 154 and 164). Diodes 156 and 166 are electrically connected between the collector electrodes 153 and 163 and the emitter electrodes of the IGBTs 328 and 330 as shown in the figure. The diodes 156 and 166 have two electrodes, a cathode electrode and an anode electrode. The cathode electrode is connected to the collector electrode of the IGBTs 328 and 330 so that the direction from the emitter electrode to the collector electrode of the IGBTs 328 and 330 is the forward direction. The anode electrode is electrically connected to the emitter electrodes of the IGBTs 328 and 330, respectively. In this embodiment, an example is shown in which IGBTs 328 and 330 are used as switching power semiconductor elements, but MOSFETs (metal oxide semiconductor field effect transistors) may be used as switching power semiconductor elements. In this case, the diode 156 and the diode 166 are unnecessary.

  Upper and lower arm series circuit 150 is provided for three phases corresponding to each phase winding of the armature winding of motor generator 192. The three upper and lower arm series circuits 150 are connected to the U-phase, V-phase, and W-phase of the motor generator 192 from the intermediate electrode 169 that connects the emitter electrode of the IGBT 328 and the collector electrode 163 of the IGBT 330 via the AC terminal 159. . The upper and lower arm series circuits are electrically connected in parallel. The collector electrode 153 of the IGBT 328 in the upper arm is connected to the positive capacitor electrode 331 of the capacitor 326 via the positive terminal (P terminal) 157, and the emitter electrode of the IGBT 330 in the lower arm is connected to the capacitor 326 via the negative terminal (N terminal) 158. Each is electrically connected (connected by a DC bus bar) to the negative electrode capacitor electrode 332. The intermediate electrode 169 corresponding to the connection portion between the emitter electrode of the IGBT 328 of the upper arm and the collector electrode of the IGBT 330 of the lower arm is electrically connected to the corresponding phase winding of the armature winding of the motor generator 192 via the AC connector 188. Has been.

  Capacitor 326 forms a smoothing circuit that suppresses fluctuations in DC voltage caused by the switching operation of IGBTs 328 and 330. The positive electrode side of the battery 136 is electrically connected to the positive electrode side capacitor electrode 331 of the capacitor 326, and the negative electrode side of the battery 136 is electrically connected to the negative electrode side capacitor electrode 332 of the capacitor 326 via the DC connector 138. Thus, the capacitor 326 is connected to a so-called inverter DC link between the collector electrode 153 of the upper arm IGBT 328 and the positive electrode side of the battery 136 and the emitter electrode of the lower arm IGBT 330 and the negative electrode side of the battery 136. The upper and lower arm series circuit 150 is electrically connected in parallel.

  The motor controller 170 is a circuit that operates the IGBTs 328 and 330, and includes a control circuit 172 that generates a timing signal for controlling the switching timing of the IGBTs 328 and 330 based on input information from other control devices and sensors, and a control And a drive circuit 174 that generates a drive signal for switching the IGBTs 328 and 330 based on the timing signal output from the circuit 172.

  The control circuit 172 includes a microcomputer (hereinafter referred to as a microcomputer) for calculating the switching timing of the IGBTs 328 and 330. The microcomputer includes a target torque value required for the motor generator 192 as input information, a current value supplied from the upper and lower arm series circuit 150 to the armature winding of the motor generator 192, and the rotor of the motor generator 192. The magnetic pole position is input. The target torque value is based on a command signal output from a host controller (not shown), and the current value is detected based on a detection signal output from the current sensor 180. The magnetic pole position is detected based on a detection signal output from a rotating magnetic pole sensor (not shown) provided in the motor generator 192. In this embodiment, the case of detecting AC current values for three phases will be described as an example, but AC current values for two phases may be detected.

  A microcomputer (not shown) built in the control circuit 172 calculates the d and q axis current command values of the motor generator 192 based on the target torque value, and calculates the d and q axis current command values and the detection results. The d and q-axis voltage command values are calculated based on the difference between the d and q-axis current values, and the d and q-axis voltage command values are calculated for the U, V, and W phases based on the detected magnetic pole positions. Convert to voltage command value. Then, a fundamental wave (sine wave) based on the voltage command values of the U phase, V phase, and W phase is compared with a carrier wave (triangular wave) to generate a pulse-like modulated wave, and this modulated wave is PWM (pulse width modulated) ) Output to the driver circuit 174 as a signal.

  When driving the lower arm, the driver circuit 174 amplifies the PWM signal and outputs the amplified PWM signal to the gate electrode of the corresponding lower arm IGBT 330 as a drive signal. When the upper arm is driven, the PWM signal is amplified after shifting the reference potential level of the PWM signal to the reference potential level of the upper arm, and is output as a drive signal to the gate electrode of the corresponding IGBT 328 of the upper arm. To do. As a result, each IGBT 328, 330 performs a switching operation based on the input drive signal.

  The motor controller 170 detects abnormalities such as overcurrent, overvoltage, and overtemperature, and protects the upper and lower arm series circuit 150. For this reason, sensing information is input to the motor controller 170. For example, the information on the current flowing through the emitter electrodes of the IGBTs 328 and 330 is input to the corresponding drive unit (IC) from the signal emitter electrode terminals 155 and 165 of each arm. Thereby, each drive part (IC) detects overcurrent, and when overcurrent is detected, it stops the switching operation of corresponding IGBT328,330, and protects corresponding IGBT328,330 from overcurrent. Further, temperature information of the upper and lower arm series circuit 150 is input to the microcomputer from a temperature sensor (not shown) provided in the upper and lower arm series circuit 150. In addition, information on the voltage on the DC positive side of the upper and lower arm series circuit 150 is input to the microcomputer. The microcomputer performs over-temperature detection and over-voltage detection based on such information, and when an over-temperature or over-voltage is detected, stops the switching operation of all the IGBTs 328 and 330, and the upper and lower arm series circuit 150 or this circuit 150 Protects semiconductor modules including overtemperature and overvoltage.

  The conduction and cut-off operations of the IGBTs 328 and 330 of the upper and lower arms of the inverter circuit 144 are switched in a constant order, and the current of the stator winding of the motor generator 192 at the time of switching flows through a circuit formed by the diodes 156 and 166.

  As shown in FIG. 2, the upper and lower arm series circuit 150 includes a positive terminal (P terminal, positive terminal) 157, a negative terminal (N terminal 158, negative terminal), an AC terminal 159 from the intermediate electrode 169 of the upper and lower arms, and an upper arm. A signal terminal (signal emitter electrode terminal) 155, an upper arm gate electrode terminal 154, a lower arm signal terminal (signal emitter electrode terminal) 165, and a lower arm gate terminal electrode 164. The power conversion device 200 includes a DC connector 138 on the input side and an AC connector 188 on the output side, and is connected to the battery 136 and the motor generator 192 via the connectors 138 and 188. In addition, as a circuit which generates the output of each phase of the three-phase alternating current output to the motor generator, a power conversion device having a circuit configuration in which two upper and lower arm series circuits are connected in parallel to each phase may be used.

  The battery 136 and the DC power supply smoothing capacitor 326 are connected via a contactor 304. The contactor 304 is controlled on (closed) and off (open) by a signal 402. A series circuit of the discharge resistor 324 and the switching element 325 is connected to both ends of the capacitor 326. The discharge control circuit 300 performs on / off control of the switching element 325 so as to turn on and off the discharge current from the capacitor 326 to the discharge resistor 324. In this specification, the discharge resistor 324 is represented as a single resistor. However, the discharge resistor 324 may be a single resistor, or a low-power resistor may be connected in parallel, in series, or directly. A large-capacity discharge resistor may be configured by connecting in parallel.

  FIG. 3 shows an electric circuit configuration of the discharge control circuit 300 of the DC power supply smoothing capacitor 326 according to the embodiment. In FIG. 3, the same components as those shown in FIG. 1 and FIG. The power conversion device 200 is connected to the battery 136 via the contactor 304. The contactor 304 is controlled by a signal 402 from the battery controller 303. Further, the battery controller 303 is controlled by a host vehicle travel controller 302. The host vehicle travel controller 302 also controls the power conversion apparatus 200 via the motor controller 170.

  The discharge control circuit 300 includes a microcomputer 319, a microcomputer power supply 318, photocouplers 313 and 315, a voltage dividing circuit 317, a buffer 323, and a collector voltage detection circuit 322. The microcomputer power supply 318 supplies a power supply voltage of 5 V from the DC power supply (DC link) of the power converter 200 to the microcomputer 319. Further, the microcomputer power supply 318 receives the PRUN signal 320 transmitted from the microcomputer 319. The PRUN signal 320 is a signal indicating that the microcomputer 319 is operating normally. When the microcomputer power supply 318 detects that the microcomputer 319 does not operate normally by the PRUN signal 320, the microcomputer power supply 318 transmits a RESET signal 321 to the microcomputer 319 and resets the microcomputer 319.

  The photocoupler 313 transmits the discharge command signal 314 from the motor controller 170 to the microcomputer 319. The photocoupler 315 transmits an error signal 315 from the microcomputer 319 to the motor controller 170. The voltage dividing circuit 317 converts the high voltage of the DC power supply smoothing capacitor 326 into a voltage range that can be measured by the voltage measurement circuit (AD conversion circuit) of the microcomputer 319. The buffer 323 amplifies the discharge control signal 328 (5 V level) output from the microcomputer 319 to the gate operation level signal (15 V level) of the switching element 325 and supplies it to the gate of the switching element 325. A circuit example of the buffer 323 will be described later.

  The collector voltage detection circuit 322 detects whether the collector voltage of the switching element 325 is a high voltage or a low voltage and transmits it to the microcomputer 319. Here, if the collector voltage is high, the switching element 325 is in an off (cutoff) state, and if the collector voltage is low, the switching element 325 is in an on (energized) state. A circuit example of the collector voltage detection circuit 322 will be described later. The microcomputer 319 receives the discharge command signal 314 from the motor controller 170 via the photocoupler 313 and outputs a discharge control signal 328 for controlling the switching element 325. Further, the microcomputer 319 measures the terminal voltage of the DC power supply smoothing capacitor 326 via the voltage dividing circuit 317, and terminates the discharge when the terminal voltage of the capacitor 326 falls to the final target voltage of the discharge. Furthermore, the microcomputer 319 detects whether the switching element 325 is operating normally by detecting whether the switching element 325 is on or off by the collector voltage detection circuit 322. 316 is output. Note that an LED warning light may be provided in the inverter housing so that it is lit when malfunctioning or when the discharge is not completed.

  FIG. 14 is an internal circuit diagram of the buffer 323 of the discharge control circuit 300. The buffer 323 includes an NMOS inverter gate circuit 1401, a PMOS inverter gate circuit 1402, and a pull-down resistor 1403. The input terminal 1406 is connected to the input of the NMOS inverter gate circuit 1401. The output of the NMOS inverter gate circuit 1401 is connected to the input of the PMOS inverter gate circuit 1402. The output of the PMOS inverter gate circuit 1402 is connected to the output terminal 1407. In both inverter gate circuits, the power supply is connected to a 15V power supply (Vcc15) 1408. Here, the NMOS gate voltage threshold value VGS (th) of the NMOS inverter gate circuit 1401 is about 2.5V.

  Thus, since the inverter 323 is connected in two stages in the buffer 323, the logic of the input and output is the same, but the logic threshold value of the NMOS inverter gate circuit 1401 is about 2.5V. A 5V level signal can be converted to a 15V level signal. The pull-down resistor 1403 is connected between the input of the NMOS inverter gate circuit 1401 and the ground 1409, and makes the input of the NMOS inverter gate circuit 1401 low level even when the input terminal 1406 becomes high impedance. As a result, the buffer 323 outputs a low level and does not enter a discharge state even when the previous stage fails and the input becomes high impedance.

  FIG. 15 is an internal circuit diagram of the collector voltage detection circuit 322 of the discharge control circuit 300. The collector voltage detection circuit 322 includes a high voltage diode 1501, a pull-up resistor 1502, and a buffer 1503. The collector of the switching element 325 is connected to the input terminal 1504. The cathode of the high voltage diode 1501 is connected to the input terminal 1504, and the anode is connected to the input terminal of the buffer 1503. The anode of the high voltage diode 1501 is connected to a 5V power source (Vcc5) 1505 via a pull-up resistor 1502. Further, the output of the buffer 1503 is connected to an output terminal 1505, and the power source of the buffer 1503 is connected to a 5V power source (Vcc5) 1505.

  The collector of the switching element 325 is connected to the positive electrode of the DC power supply smoothing capacitor 326 via the discharge resistor 324. When the switching element 325 is turned off, a high voltage of 300 V or more is normally obtained. At this time, the cathode voltage of the high voltage diode 1501 is 300 V or more, and the anode voltage is 5 V, which is the same as that of the 5 V power source 1506. Therefore, the high voltage diode 1501 is reverse biased and turned off. Then, the input of the buffer 1503 becomes 5V, that is, a high level, and a high level is output to the output terminal 1505. On the other hand, when the switching element 325 is on, the collector of the switching element 325 is about 0 to 1V. At this time, the cathode potential of the high breakdown voltage diode 1501 is 0 to 1 V and the anode potential is 5 V, which is the same as that of the 5 V power source 1506. Therefore, the high breakdown voltage diode 1501 is in a forward bias state and is turned on. Then, the input of the buffer 1503 becomes a high level, and a low level is output to the output terminal 1505.

  FIG. 4 is a timing chart showing the operation of each part of the discharge control circuit 300 when normal discharge is performed. Here, the high level of the discharge command signal 314 corresponds to the discharge. First, at time 405 in FIG. 4, prior to discharging, the vehicle travel controller 302 changes the contactor control signal 402 from a high level to a low level via the battery controller 303. As a result, the contactor 304 is switched from on (closed) to off (open). At the subsequent time 406, when the vehicle travel controller 302 issues a discharge command signal to the motor controller 170, the motor controller 170 changes the discharge command signal 314 to the discharge control circuit 300 from a low level to a high level. Next, when the microcomputer 319 changes the discharge control signal 328 from a low level to a high level at time 407, the switching element 325 is turned on (energized), and the discharge of the DC power supply smoothing capacitor 326 by the resistor 324 is started. From time 408, the voltage of the DC power supply smoothing capacitor 326 begins to drop. When the voltage of the capacitor 326 drops to the discharge target voltage at time 409, the microcomputer 319 changes the discharge control signal 328 from high level to low level at time 410, and stops discharging. Thereafter, at time 411, the motor controller 170 changes the discharge command signal 314 from the high level to the low level to complete the discharge.

  In the timing chart shown in FIG. 4, the discharge command signal 314 is described as being at a low level in the normal state (discharge stop state) and at a high level at the time of discharge. However, in the normal state (discharge stop state), it is a PWM signal having a duty of 25%. Alternatively, the microcomputer 319 may be controlled as a PWM signal with a duty of 75% during discharging, and the switching element 325 may be duty-driven by the microcomputer 319.

  FIG. 5 is a timing chart showing the protection operation of the discharge control circuit 300 when the contactor 304 is turned on (closed) for some reason during the discharge. When the discharge command signal 314 output from the motor controller 170 to the discharge control circuit 300 becomes high level, the microcomputer 319 changes the discharge control signal 328 from low level to high level at time 501 in FIG. 5, and starts discharging. When this discharge start time is T0, the voltage of the DC power supply smoothing capacitor 326 starts to decrease from the initial value V0 from time 504. The microcomputer 319 measures the voltage of the capacitor 326 at time T1, T2,..., Tn-1 at regular intervals as voltages V1, V2,. Compare with the characteristic (indicated by the broken line in FIG. 5) 503. When the contactor 304 is turned on at time Tn, the voltage of the capacitor 326 increases rapidly from Vn and exceeds the voltage drop characteristic 503. The microcomputer 319 determines that the discharge is abnormal because the voltage of the capacitor 326 becomes larger than the voltage drop characteristic 503 in spite of the discharge, and changes the discharge control signal 328 from the high level to the low level at time 509 to stop the discharge. .

  Here, the voltage drop characteristic 503 shown in FIG. 5 is a characteristic curve showing a drop in the capacitor voltage with respect to the discharge time when the DC power supply smoothing capacitor 326 is discharged through the discharge resistor 324. The capacitor voltage decreases exponentially as the length increases. The voltage drop characteristic 503 can be obtained by calculation based on the capacitance C of the capacitor 326 and the resistance value R of the discharge resistor 324. However, the voltage drop characteristic 503 can be calculated in consideration of the internal resistance of the capacitor 326 and the switching element 325, or measured. It is desirable to do.

  FIG. 6 is a PAD showing a protection operation by the microcomputer 319 of the discharge control circuit 300. In step 601, the discharge control circuit 300 starts this protection operation when receiving the discharge command signal 314 from the motor controller 170, and then repeatedly executes the protection operation every predetermined time T while receiving the discharge command signal 314. To do. First, in step 602, a counter i that counts the number of times the protection operation is repeated is reset to zero. Since the protection operation is repeated every T time while the discharge command signal 314 is received, (i · T) becomes the discharge time. In the subsequent step 603, the initial voltage V0 of the DC power supply smoothing capacitor 326 is measured, and then in step 604, the discharge control signal 328 is set to high level to turn on the switching element 325 and start discharging.

In step 605, the processing in steps 606 to 615 is repeated every time T. First, at step 606 after time T, the counter i is incremented, and at step 607, the voltage Vi of the capacitor 326 at time Ti is measured. In step 608, as shown in FIG. 5, whether or not the capacitor voltage Vi at the time Ti exceeds the voltage drop characteristic 503 is determined by the following equation.
Vi> K ^ i · V0 (1)
In the formula (1), “^” represents a power. K is a coefficient K that determines the voltage drop characteristic at time Ti, and is represented by K≈exp (−T / RC) where R is the resistance value of the discharging resistor 324 and C is the capacitance of the capacitor 326. . exp (−T / RC) is a ratio of the capacitor voltage Vi to the initial voltage V0 in the discharge time T when the charge charged in the capacitor having the capacitance C is discharged by the resistor having the resistance value R. That is, assuming that the capacitor voltage at the discharge time Ti when the electric charge charged in the capacitor having the capacitance C is discharged by the resistor having the resistance value R is Videal (Ti), Videal (Ti) ≦ K ^ i · V0.

  In step 608, the actual K is desirably set to K ≧ exp (−T / RC) in consideration of the voltage measurement error of the microcomputer 319. Further, (K ^ i) is not subjected to exponentiation every time, but the previous result (K ^ (i-1)) is stored and the product of K and K can be saved. In addition, here, an example in which it is determined whether or not the capacitor voltage Vi at the time Ti exceeds the voltage drop characteristic 503 by the equation (1) is shown, but the characteristic curve of the voltage drop characteristic 503 as shown by a broken line in FIG. May be stored, and the voltage drop characteristic at the time Ti may be read and compared with the measured value Vi.

  By the way, when the contactor 304 is turned on for some reason during the discharge, the terminal voltage of the battery 136 is applied to both ends of the DC power supply smoothing capacitor 326. Therefore, the capacitor voltage Vi rapidly increases and Vi> K ^ i · V0. If the discriminant (1) is satisfied in step 608, the process proceeds to step 609, where the discharge control signal 328 is set to the low level, the switching element 325 is turned off, and the discharge is stopped (discharge stop). In step 610, the program pauses for a predetermined time Tintv. This pause time is a waiting time until the temperature of the discharge resistor 324 sufficiently decreases. In step 611 after the pause time Tintv has elapsed, the initial state is restored.

  If discriminant (1) is not satisfied in step 608, that is, if the capacitor voltage Vi is equal to or lower than the voltage drop characteristic (K ^ i · V0) at time Ti, it is determined that the contactor 304 remains off, and the discharge is performed. Continue. In this case, the process proceeds to step 612, where it is determined whether or not the capacitor voltage Vi has reached a preset discharge target voltage. If the capacitor voltage Vi has reached the discharge target voltage, the process proceeds to step 613 and the discharge control signal 328 is set to a low level. Then, the switching element 325 is turned off to stop discharging (discharge completion). Thereafter, in step 614, the program is paused for a predetermined time Tintv. This pause time is a waiting time until the temperature of the discharge resistor 324 sufficiently decreases. In step 614 after the pause time Tintv has elapsed, the initial state is restored.

Instead of the discriminant (1) in step 608 in FIG. 6, it is discriminated whether or not the capacitor voltage Vi exceeds the voltage drop characteristic at the time Ti by the discriminant (2) shown in step 701 in FIG. Also good.
Vi / V i-1> K (2)
In the equation (2), Vi is a measured value of the capacitor voltage at time Ti, and Vi-1 is a measured value of the capacitor voltage at time Ti-1. K is a coefficient that determines the voltage drop characteristic at time Ti, and is represented by K≈exp (−T / RC) where R is the resistance value of the discharge resistor 324 and C is the capacitance of the capacitor 326. When the determination result by the expression (2) is affirmed, it is determined that the contactor 304 is turned on for some reason, and the discharge is stopped. In FIG. 7, steps other than step 701 are the same as the processing shown in FIG.

Incidentally, there is an error in voltage measurement by the microcomputer 319, and the influence of the error becomes larger as the measurement voltage is lower. Therefore, a protection operation will be described in which the measurement time interval is lengthened as the capacitor voltage becomes lower, and the change in the capacitor voltage becomes larger than the measurement error. FIG. 8 is a PAD showing another embodiment of the protection operation by the microcomputer 319 of the discharge control circuit 300. In FIG. 8, steps that perform the same processing as the processing shown in FIG. 6 are given the same step numbers, and differences will be mainly described. In the protection operation shown in FIG. 6, the voltage Vi of the DC power supply smoothing capacitor 326 is measured at a constant time interval T, whereas in the protection operation shown in FIG. 8, the voltage increases as the voltage of the capacitor 326 decreases due to discharge. The time interval for measuring is increased. In this protection operation, the measurement time interval Tdelta of the capacitor voltage Vi is
Tdelta = −RC · ln (exp (−Ti / RC) −Verror / V0) (3)
And In the equation (3), ln is a natural logarithm, and Verror is a measurement error.

If the time interval at which the difference between the previous and current capacitor voltage is the measurement error Verror is Tdelta,
Verror = Vi + 1−Vi = V0 (exp (− (Ti + Tdelta) / RC) −exp (−Ti / RC)) (4)
And solving for T delta,
Tdelta = −RC · ln (exp (−Ti / RC) −Verror / V0) (5)
It becomes. Therefore, instead of step 605 in FIG. 6, in step 801 in FIG. 8, the subsequent determination process is repeated regardless of the time, and after step 612, a new step 802 is provided to wait for Tdelta time.

  FIG. 9 is a timing chart showing the discharge protection operation when the contactor 304 is in the on (closed) state when the discharge command signal is received. As the discharge command signal 314 changes from the low level to the high level at the time 405, the discharge control signal 328 is set to the high level at time 407 to start the discharge, but the contactor control signal 402 remains at the high level (ON). And the contactor 304 remains on (closed). As described above, when the contactor 304 is closed during discharging, the voltage of the DC power supply smoothing capacitor 326 does not decrease as in the normal state (time 408) and exceeds the voltage reduction characteristic 503 shown in FIG. The microcomputer 319 returns the discharge control signal 328 from the high level to the low level and stops the discharge.

  Thereafter, after a pause for a time Tintv, the process returns to the process at the time when the discharge command signal 314 was received, but the discharge command signal 314 remains at the high level, and the discharge control signal 328 is again set to the high level to start discharging. . However, since the contactor 304 remains closed, the capacitor voltage does not drop, and the capacitor voltage again exceeds the voltage drop characteristic 503. Therefore, the discharge control signal 328 is returned from the high level to the low level and the discharge is performed in the same manner as the previous time. Cancel. This operation is repeated while the contactor 304 is closed. When the contactor control signal 402 becomes a low level at the time 901 during the pause time Tintv and the contactor 304 is turned off (opened), the capacitor voltage is normally decreased at the time 904 after the pause time Tintv (905), and the discharge occurs. Complete.

  FIG. 10 is a timing chart showing another embodiment of the discharge protection operation when the contactor 304 is in the closed state when the discharge command signal is received. In some automobiles, it is assumed that the contactor control signal 402 is slightly delayed from the discharge command signal 314 even if the system is normal. In such a case, in the discharge protection operation shown in FIG. 9, since the first discharge is stopped due to the abnormality determination, the discharge is stopped normally for the time Tintv, and then the discharge is normally performed by the second discharge. The time from when 314 is issued until the discharge is completed increases to the rest time Tintv or more. However, it is desirable for the discharge circuit to have a short time from when the discharge command signal 314 is issued until the discharge is completed.

  Therefore, in the discharge protection operation shown in FIG. 10, a pause time Tintv0 shorter than the pause time Tintv is set as the pause time in the first discharge. In the discharge protection operation shown in FIG. 10, the discharge command signal 314 changes from low level to high level at time 405, and the discharge control signal 328 also changes from low level to high level at time 407, but the contactor control signal 402 is still high level. The discharge is stopped. However, when the contactor control signal 402 changes from the high level to the low level at the time 409 immediately after that, in the discharge protection operation shown in FIG. 9, at the time 1004 after the pause time Tintv as shown by the broken line in FIG. A discharge control signal 328 is issued to start discharging, and the capacitor voltage decreases as indicated by a broken line 1005. On the other hand, in the discharge protection operation shown in FIG. 10, the discharge control signal 328 is issued at time 1002 after a short pause time Tintv0, the discharge starts and the capacitor voltage decreases as indicated by the solid line 1003. That is, in the discharge protection operation shown in FIG. 10, the second discharge can be started earlier than the discharge protection operation shown in FIG. 9, and the discharge can be completed earlier.

  Actually, the capacitance C of the DC power supply smoothing capacitor 326 is 2000 μF, the resistance value R of the discharge resistor 324 is 400Ω, the coefficient K is 0.9, the initial discharge voltage V0 is 300 V, the target discharge voltage Vgoal is 50 V, and the voltage measurement error. In a system in which Verror is 5 V, for example, the pause time Tintv is 10 seconds and the pause time Tintv0 is 1 second.

  As described above, since the discharge is stopped even if the contactor 304 is closed during the discharge, the current does not continue to flow through the discharge resistor 324, and the discharge circuit can be protected from being damaged.

  When an abnormality occurs such as when the contactor 304 is closed while discharging the charge of the DC power supply smoothing capacitor 326 via the discharge resistor 324, the switching element 325 is turned off to stop the discharge. When a short mode failure occurs in the element 325, it cannot be turned off, and a discharge current continues to flow through the discharge resistor 324. Therefore, as shown in FIG. 11, an embodiment will be described in which a second switching element 1101 is connected in series with the switching element 325 to back up the short mode failure of the first switching element 325. In FIG. 11, only the portion related to this embodiment in the discharge control circuit 300 shown in FIG. 3 is shown. In this embodiment, a MOSFET is connected in series as the second switching element 1101 between the emitter of the switching element 325 of the discharge control circuit 300 shown in FIG. 3 and the ground. Further, the microcomputer 319 outputs a control signal 1103 for turning on and off the second switching element 1101, and controls the second switching element 1101 via the buffer 1102.

  Normally, the control signal 1103 from the microcomputer 319 is output so as to turn on the second switching element 1101. However, if the first switching element 325 cannot be in a short mode failure when the discharge must be stopped, the second switching element 1101 is turned off to stop the discharge. Note that if the first switching element 325 falls into a short mode failure, the microcomputer 319 can detect it by the collector voltage detection circuit 322. If the microcomputer 319 outputs a control signal 328 that turns off the first switching element 325, but the collector voltage detection circuit 322 transmits a low level, the first switching element 325 is in the on state. It turns out that it is in a short mode failure state.

Thus, even if the first switching element 325 falls into a short mode failure, the second
Therefore, even if the contactor 304 is turned on (closed) for some reason during the discharge, it is possible to prevent the current from continuously flowing through the discharge resistor 324 and Can protect from breakage.

In general, when the electric charge charged in the capacitor having the capacitance C is discharged by the discharge resistor R having the resistance value R, the capacitor voltage V decreases with the time constant RC. That is, the initial voltage V0 and the voltage V during discharge with respect to time t are
V = V0exp (-t / RC) (6)
It becomes. Here, the way of decreasing the voltage V becomes more gradual as the voltage V decreases with time. In other words, the lower the voltage V, the lower the time efficiency of the voltage drop and the longer the discharge time.

Therefore, an embodiment will be described in which the discharge time is shortened by lowering the resistance value of the discharge resistor when the voltage V decreases gradually. FIG. 12 shows the discharge circuit of this embodiment. In FIG. 12, only the portion related to this embodiment in the discharge control circuit 300 shown in FIG. 3 is shown. In this embodiment, a second discharge resistor 1301, a second switching element 1202, a second buffer 1203, and a second collector voltage detection circuit 1204 are newly provided for the discharge control circuit 300 shown in FIG. . The operation of these second discharge devices is similar to the operation of the first discharge device comprising the first discharge resistor 324, the first switching element 325, and the first buffer 323, but the first discharge device. The microcomputer 319 is controlled independently from the device. The resistance value R2 of the second discharge resistor 1301 is
R2 = {(Vmax + Vgoal) / 2Vmax} ^ 2 · R1 (7)
It is desirable that the value be lower than the resistance value R1 of the first discharge resistor 324. In the equation (7), Vmax is the maximum discharge voltage.

  FIG. 13 is a diagram showing a discharge waveform of the discharge circuit shown in FIG. First, when the first switching element 325 is turned on and discharge is started only by the first discharge resistor 324, the voltage of the DC power supply smoothing capacitor 326 decreases along the solid line 1301. Then, when the voltage of the capacitor 326 becomes Vsw = (Vmax + Vgoal) / 2, the second switching element 1202 is turned on to start discharging by the second discharge resistor 1301. Thereafter, discharge is performed by the first discharge resistor 324 and the second discharge resistor 1301, and the voltage of the capacitor 326 decreases along the solid line 1302. A broken line 1303 indicates a voltage waveform when only the first discharge resistor 324 is discharged to the end. Comparing the voltage waveforms 1301 and 1302 indicated by solid lines with the voltage waveform 1303 indicated by broken lines, it can be seen that the discharge time is shortened by this embodiment.

If a resistor having the same rated power as that of the first discharge resistor 324 is used for the second discharge resistor 1301, the resistance value R2 of the second discharge resistor 1301 is determined by the two discharge resistors 324 and 1301. Assuming that the maximum power is equal,
Vmax ^ 2 / R1 = {(Vmax + Vgoal) / 2} ^ 2 / R2
∴ R2 = {(Vmax + Vgoal) / 2} · R1 / Vmax ^ 2 (8)
Is obtained. When the maximum discharge voltage Vmax is 600 V, the capacitance C of the capacitor 326 is 2000 μF, and the discharge target voltage Vgoal is 50 V, for example, the resistance value R1 of the first discharge resistor 324 is 400Ω, and the second discharge resistor 1301 The resistance value R2 is 120Ω.

  According to the embodiments shown in FIGS. 12 and 13, the discharge time can be shortened without using a large discharge resistor having a large rated power.

  In addition, in the Example mentioned above and those modifications, all the combinations between Examples or an Example and a modification are possible.

  According to embodiment mentioned above, there can exist the following effects. First, a discharge circuit of the DC power supply smoothing capacitor 136 used in the power converter 200 that supplies the DC power supply of the battery 136 to the DC power supply smoothing capacitor 326 and the inverter device 140 through a contactor (switch) 304. A resistor 324 that discharges the electric charge of the capacitor 326, a switching element 325 that is connected in series with the resistor 324 to turn on and off a discharge current flowing from the capacitor 326 to the resistor 324, and a terminal voltage of the capacitor 326 is measured. Circuits 317 and 319, and a microcomputer 319 that controls energization and interruption of the switch 325. The microcomputer 319 energizes the switching element 325 and starts discharging the capacitor 326 by the resistor 324, and then the measurement circuit 317. , 319 measured by Since the switching element 325 is cut off and the discharge of the capacitor 326 by the resistor 324 is stopped when the terminal voltage of the dencer exceeds a preset voltage drop characteristic, the discharge of the capacitor 316 by the resistor 324 is stopped. Even when the contactor 304 is closed (turned on) for some reason, the discharge of the capacitor 316 by the resistor 324 is reliably stopped, and the discharge current can be prevented from continuing to flow through the resistor 324.

  In addition, according to the above-described embodiment, the voltage drop characteristic is set according to the discharge characteristic of the capacitor 326 by the resistor 324, so that the close (on) failure of the contactor 304 during discharge can be accurately and quickly performed. Can be detected.

  Further, according to the above-described embodiment, the microcomputer 319 determines whether to continue or stop the discharge based on the comparison between the terminal voltage of the capacitor 326 measured by the measurement circuits 317 and 319 and the voltage drop characteristic. Since it is performed at intervals, it is possible to quickly detect a closed (on) failure of the contactor 304 during discharge while reducing the burden on the microcomputer 319.

  According to one embodiment, the microcomputer 319 is based on the terminal voltage of the capacitor 326 before the start of discharge measured by the measurement circuits 317 and 319 and the time constant determined by the capacitance of the capacitor 326 and the resistance value of the resistor 324. Since the voltage drop characteristic is obtained by calculation and the voltage drop characteristic of the calculation result is compared with the terminal voltage of the capacitor 326 measured by the measurement circuits 317 and 319, it is determined whether the discharge is continued or stopped. A closed (on) failure of the contactor 304 can be accurately detected.

  As shown in one embodiment, the ratio of the terminal voltage of the capacitor 326 measured this time to the terminal voltage of the capacitor 326 previously measured by the measurement circuits 317 and 319 by the microcomputer 319, and the capacitance and resistance of the capacitor 326 The continuation or stop of discharge may be determined by comparing with a coefficient set based on a time constant determined by the resistance value of the device 324. Thereby, compared with the case where the voltage drop characteristic is obtained by calculation, it is possible to accurately detect a closed (on) failure of the contactor 304 during discharge while reducing the burden on the microcomputer 319.

  According to one embodiment, the microcomputer 319 increases the time interval for determining whether to continue or stop the discharge according to the elapsed time from the start of the discharge. The voltage at 326 can be accurately measured, and the occurrence of a closed (on) fault of the contactor 304 during discharge can be accurately determined.

  According to one embodiment, when the microcomputer 319 stops the discharge of the capacitor 326 by the resistor 324 because the terminal voltage of the capacitor 326 exceeds the voltage drop characteristic, the discharge is resumed until a predetermined time Tintv elapses. Therefore, the discharge by the resistor 324 whose temperature has already increased due to the discharge can be prevented, and the discharge can be restarted after the resistor 324 is sufficiently cooled.

  According to one embodiment, when the discharge is stopped for the first time by the microcomputer 319 when the terminal voltage of the capacitor 326 exceeds the voltage drop characteristic, the discharge is restarted until a predetermined time Tintv0 shorter than the predetermined time Tintv elapses. When the discharge is stopped for the second time or later, since the restart of the discharge is waited until the predetermined time Tintv elapses, the opening command signal 402 of the contactor 304 sent from the host system is slightly delayed from the discharge start command 314. Even in this case, it is possible to prevent the discharge from being resumed for a long predetermined time Tintv and to shorten the time until the discharge is completed.

  According to one embodiment, the switch is configured by connecting the first switch 325 and the second switch 1101 in series, and the collector voltage detection circuit 322 that detects the occurrence of a short-circuit failure of the first switch 325 is provided. Depending on the microcomputer 319, normally, the first switch 325 is energized and interrupted while the second switch 1101 is energized, and then the discharge is started and stopped. When the occurrence of a short-circuit failure in the first switch 325 is detected, the second switch 1101 is shut off to stop the discharge, so that even if a short-circuit failure occurs in the first switch 325, it is ensured. The discharge can be stopped and the discharge current can be prevented from continuing to flow through the resistor 324.

  According to one embodiment, a resistor for discharging the capacitor 326 includes a first resistor 324 having a first resistance value and a second resistor value having a second resistance value lower than the first resistance value. And a switch for conducting and interrupting the discharge current is connected in series with the first resistor 324 and energized and interrupted for the discharge current flowing from the capacitor 326 to the first resistor 324. And a fourth switch 1202 connected in series with the second resistor 1301 to conduct and cut off the discharge current flowing from the capacitor 326 to the second resistor 1301. The microcomputer 319 energizes the third switch 325 to start discharging the capacitor 326 by the first resistor 324, and is measured by the measurement circuits 317 and 319. When the terminal voltage of the capacitor 326 falls below the predetermined voltage Vsw, in addition to discharging the capacitor 326 by the first resistor 324, the fourth switch 1202 is energized to start discharging the capacitor 326 by the second resistor 1301. Thus, the discharge time of the capacitor 326 can be shortened by using the first resistor 324 and the second resistor 1301 with low power.

Inverter device, 144; Inverter circuit, 200; Power conversion device, 300; Discharge control circuit, 304; Contactor, 317; Voltage divider circuit, 319; Microcomputer, 322; Collector voltage detection circuit, 324, 1301 Discharge resistor, 325, 1101, 1202; switching element, 326; DC power supply smoothing capacitor

Claims (9)

A power converter for supplying DC power to a DC power supply smoothing capacitor and inverter via a switch,
A resistor for discharging the charge of the capacitor;
A switch connected in series with the resistor, for energizing and interrupting a discharge current flowing from the capacitor to the resistor;
A measurement circuit for measuring the terminal voltage of the capacitor;
A control circuit for controlling energization and shut-off of the switch,
The control circuit, when the switch is energized and the capacitor terminal voltage measured by the measurement circuit after starting the discharging of the capacitor by the resistor exceeds a preset voltage drop characteristic And shutting off the switch to stop discharging the capacitor by the resistor,
Further, the control circuit is based on a comparison between the terminal voltage of the capacitor measured by the measurement circuit and the voltage drop characteristic during a period from when the switch is turned off to stop discharging of the capacitor by the resistor. A power conversion apparatus, wherein the determination is made to perform the determination of continuation or stop of discharge a plurality of times at predetermined time intervals. The power conversion device according to claim 1,
The power conversion device, wherein the voltage drop characteristic is set according to a discharge characteristic of the capacitor by the resistor. The power conversion device according to claim 2,
The control circuit has the voltage drop characteristic based on an exponential function using a time constant determined by a terminal voltage of the capacitor before the start of discharge measured by the measurement circuit, a capacity of the capacitor, and a resistance value of the resistor. A power conversion device characterized in that it determines whether the discharge is continued or stopped by comparing the voltage drop characteristic and the terminal voltage of the capacitor measured by the measurement circuit. The power conversion device according to claim 3,
The control circuit is set based on the ratio of the terminal voltage of the capacitor measured this time to the terminal voltage of the capacitor previously measured by the measuring circuit, and the time constant determined by the capacitance of the capacitor and the resistance value of the resistor. A power conversion device characterized by comparing the obtained coefficient to determine whether the discharge is continued or stopped. In the power converter according to any one of claims 1 to 4,
The said control circuit lengthens the said time interval according to the elapsed time after starting discharge, The power converter device characterized by the above-mentioned. In the power converter according to any one of claims 1 to 5,
When the terminal voltage of the capacitor exceeds the voltage drop characteristic and the discharge of the capacitor by the resistor is stopped, the control circuit does not restart the discharge until a first predetermined time elapses. A power converter. The power conversion device according to claim 6, wherein
In the first stop of discharge due to the terminal voltage of the capacitor exceeding the voltage drop characteristic, the control circuit waits for resumption of discharge until a second predetermined time shorter than the first predetermined time elapses. When the discharge is stopped for the second time or later, the power conversion device waits for the discharge to resume until the first predetermined time elapses. In the power converter device according to any one of claims 1 to 7,
The switch has a first switch and a second switch connected in series,
A detection circuit for detecting occurrence of a short-circuit fault in the first switch;
The control circuit normally starts and stops discharging by energizing and shutting off the first switch while the second switch is energized. When the discharge is stopped, the detection circuit causes a short circuit failure of the first switch. In the case where the occurrence of the occurrence is detected, the second switch is cut off to stop the discharge. In the power converter according to any one of claims 1 to 8,
The resistor includes a first resistor having a first resistance value and a second resistor having a second resistance value lower than the first resistance value,
The switch is connected in series to the first resistor and is connected in series to the third switch for conducting and interrupting a discharge current flowing from the capacitor to the first resistor, and to the second resistor. A fourth switch for energizing and interrupting the discharge current flowing from the capacitor to the second resistor;
The control circuit energizes the third switch to start discharging the capacitor by the first resistor, and when the terminal voltage of the capacitor measured by the measurement circuit becomes a predetermined voltage or less, the first circuit In addition to discharging the capacitor by a resistor, the fourth switch is energized to start discharging the capacitor by the second resistor.

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