JP2015061350A - Smoothing circuit for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smoothing circuit for a vehicle capable of eliminating the need for discharging process of capacitors during collision of the vehicle.SOLUTION: A smoothing circuit for a vehicle having a plurality of capacitors 21a, 21b, and 21 connected in series includes interruption means for interrupting the connection between the adjacent capacitors of the capacitors 21a, 21b, and 21c during collision of the vehicle. The interruption means includes, for example, a relay 22a for interrupting the connection between the capacitor 21a and the capacitor 21b, a relay 22b for interrupting the connection between the capacitor 21b and the capacitor 21c, and a relay control section 23 that controls the interruptions performed by the relays 22a and 22b during the collision of the vehicle.

Description

  The present invention relates to a smoothing circuit for a vehicle including a plurality of capacitors (capacitors).

  Conventionally, a smoothing circuit including a plurality of capacitors connected in parallel is known (see, for example, Patent Document 1). This smoothing circuit has means for switching the connection of a plurality of capacitors from a parallel connection to a series connection so that the voltage of the capacitor decreases when the occurrence of an accident is detected.

JP 2010-246316 A

  However, in the above-described conventional technology, it is necessary to discharge each capacitor at the time of a vehicle collision. Accordingly, an object of the present invention is to provide a smoothing circuit for a vehicle that can eliminate the discharge process of a capacitor in the event of a vehicle collision.

To achieve the above objective,
A smoothing circuit for a vehicle in which a plurality of capacitors are connected in series,
A smoothing circuit for a vehicle is provided, comprising a dividing means for dividing the connection between the capacitors at the time of a vehicle collision.

  According to one aspect, it is possible to dispense with capacitor discharge processing at the time of a vehicle collision.

The figure which showed the example of 1 structure of the power conversion system which concerns on embodiment

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

  FIG. 1 is a diagram illustrating a configuration example of a power conversion system 100 according to an embodiment. The power conversion system 100 is a system mounted on an electric vehicle. Specific examples of the electric vehicle include a hybrid vehicle and an electric vehicle. The power conversion system 100 includes a battery 10, a relay 11, a motor 30, and an inverter 20.

  The battery 10 is an example of a DC power source that can supply the inverter 20 with high-voltage DC power for the inverter 20 to rotationally drive the motor 30. The battery 10 is a power storage device having, for example, a positive electrode 10 a connected to the positive electrode bus 27 of the inverter 20 and a negative electrode 10 b connected to the negative electrode bus 28 of the inverter 20. Specific examples of the battery 10 include secondary batteries such as a lithium ion battery and a nickel metal hydride battery.

  The power conversion system 100 includes a converter between the battery 10 and the inverter 20 that boosts the DC voltage of the battery 10 and supplies the boosted DC voltage to the inverter 20 and steps down the DC voltage of the inverter 20 and supplies it to the battery 10. It's okay. Further, the converter may be replaced with the illustrated battery 10.

  The relay 11 is an example of a cutoff unit that can cut off the connection between the battery 10 and the inverter 20. The relay 11 is means for cutting off the power supply path 12 connecting the positive electrode 10 a of the battery 10 and the positive electrode bus 27 of the inverter 20 to separate the battery 10 and the inverter 20. Relay 11 may be a means for separating battery 10 and inverter 20 by blocking power supply path 13 connecting negative electrode 10b of battery 10 and negative electrode bus 28 of inverter 20.

  The motor 30 is, for example, a three-phase motor that is rotationally driven by three-phase AC power supplied from the inverter 20. The motor 30 is used, for example, as a travel drive source of the vehicle, but may be used for other purposes (for example, a generator that generates power using engine power). The electric power (for example, regenerative electric power) generated by the motor 30 is charged into the battery 10 via the inverter 20, for example.

  The inverter 20 is a power conversion device that converts power between the battery 10 and the motor 30. The inverter 20 converts the DC power supplied from the battery 10 into AC power, and supplies the converted AC power to the motor 30 to rotate the motor 30. Conversely, the inverter 20 charges the battery 10 by converting the AC power generated by the motor 30 into DC power and supplying the converted DC power to the battery 10.

  The inverter 20 includes an inverter circuit 26, an inverter control unit 25, and a smoothing circuit 24.

  The inverter circuit 26 is a circuit that converts DC power supplied from the battery 10 into AC power supplied to the motor 30, and converts AC power supplied from the motor 30 into DC power supplied to the battery 10. The inverter circuit 26 is provided between the positive electrode bus 27 and the negative electrode bus 28.

  The inverter circuit 26 has six inverter elements 26a to 26f. Each of the six inverter elements 26a to 26f is a semiconductor switching element that can be turned on / off. Specific examples of the semiconductor switching element include transistors such as IGBTs and MOSFETs.

  The inverter control unit 25 is an example of a control unit that controls the power conversion operation of the inverter circuit 26. The inverter control unit 25 is a control circuit having a drive unit that PWM-drives on / off operations of the six inverter elements 26a to 26f, for example.

  When the inverter control unit 25 causes the inverter circuit 26 to perform a power conversion operation, a ripple current whose current value greatly fluctuates flows in the positive electrode bus 27 as the inverter elements 26 a to 26 f are turned on and off. The ripple current is a factor that causes a decrease in the life of the battery 10 or a noise source that affects electronic devices around the inverter 20.

  In order to reduce the ripple current, the inverter 20 includes a smoothing circuit 24 including an input filter capacitor that suppresses fluctuations in the ripple current. The input filter capacitor of the smoothing circuit 24 smoothes the DC voltage between the positive electrode bus 27 and the negative electrode bus 28.

  By the way, there is a case where the power conversion operation of the inverter 20 stops due to some reason such as a vehicle collision (for example, the inverter control unit 25 stops the power conversion operation of the inverter 20). In such a case, if the capacitor configured in the smoothing circuit 24 remains charged, even if the battery 10 and the inverter 20 are disconnected by the relay 11, a voltage substantially equal to the battery 10 is generated in the inverter 20. It remains between point A and point B.

  However, even if the power conversion operation of the inverter 20 suddenly stops due to a vehicle collision or the like, a high voltage higher than a voltage value that may affect the human body is not charged in the capacitor configured in the smoothing circuit 24. As such, some measures are necessary.

  Therefore, the smoothing circuit 24 of the present embodiment includes a plurality of capacitors connected in series and a dividing unit that divides the connection between the plurality of capacitors when an abnormal event such as a collision of the host vehicle occurs. . By such a dividing means, even if the power conversion operation of the inverter 20 is stopped, a high voltage equal to or higher than a predetermined voltage value is prevented from remaining in the capacitor in the inverter 20 without performing discharge processing of each capacitor. it can.

  For example, the DC voltage of x volts between the positive electrode bus 27 and the negative electrode bus 28 is smoothed by an input filter capacitor configured by connecting n capacitors having the same capacitance (capacitance) in series. Suppose that Further, the minimum value of the high voltage that is not allowed to remain in the capacitor in the inverter 20 when any abnormal event such as a collision of the host vehicle occurs is set to a volt.

  The dividing means of the smoothing circuit 24 disconnects the connection between the n capacitors when the occurrence of an abnormal event such as a collision is detected. When the connection between the n capacitors is disconnected, the voltage between the electrodes of the individual capacitors is (x / n) volts, even if no discharge treatment is applied.

  Therefore, n capacitors each having a capacity equal to or smaller than a predetermined value so as to satisfy “(x / n) <a” are connected in series, and the connection between the capacitors is disconnected, so that there is no discharge treatment. Thus, it is possible to eliminate a capacitor in which a high voltage equal to or higher than the voltage value a remains. Thus, since the discharge process of each capacitor can be made unnecessary, for example, various controls and circuits for discharging each capacitor can be omitted, and the increase in size, weight, and cost of the inverter 20 can be suppressed.

  FIG. 1 shows relays 22a, 22b as dividing means for dividing the connection between adjacent capacitors among three capacitors 21a, 21b, 21c connected in series when an abnormal event such as a collision of the host vehicle occurs. The relay control unit 23 is illustrated.

  One electrode on the high potential side of the capacitor 21a is connected to the positive electrode bus 27 at a point A, and the other electrode on the low potential side of the capacitor 21a is connected to one electrode on the high potential side of the capacitor 21b via a relay 22a. It is connected. One electrode on the high potential side of the capacitor 21c is connected to the other electrode on the low potential side of the capacitor 21b via the relay 22b, and the other electrode on the low potential side of the capacitor 21c is connected to the negative electrode bus 28 at the point B. It is connected.

  The relay 22a is an example of a blocking unit that can block the connection between the adjacent capacitor 21a and the capacitor 21b. The relay 22a is means for separating the capacitor 21a and the capacitor 21b by blocking a path connecting the low potential side electrode of the capacitor 21a and the high potential side electrode of the capacitor 21b. The relay 22a is inserted in a path connecting the capacitor 21a and the capacitor 21b.

  The relay 22b is an example of a blocking unit that can block the connection between the adjacent capacitor 21b and the capacitor 21c. The relay 22b is means for separating the capacitor 21b and the capacitor 21c by blocking a path connecting the low potential side electrode of the capacitor 21b and the high potential side electrode of the capacitor 21c. The relay 22b is inserted in a path connecting the capacitor 21b and the capacitor 21c.

  The type of the relays 22a and 22b is, for example, normally open (open when not energized).

  The relay control unit 23 is, for example, a control circuit that outputs a signal for closing all the contacts of the relays 22a and 22b when the operation of the inverter 20 is started. The capacitor 21a and the capacitor 21b are connected in series by closing the contact of the relay 22a, and the capacitor 21b and the capacitor 21c are connected in series by closing the contact of the relay 22b. Capacitors 21a, 21b, and 21c are connected in series in this order, whereby an input filter capacitor is formed between positive electrode bus 27 and negative electrode bus 28.

  A signal output from the relay control unit 23 to the relays 22a and 22b when an abnormal event such as a collision occurs and the voltage of the capacitor in the inverter 20 is not allowed to exceed a predetermined value. Is cut off. For example, when the occurrence of an abnormal event such as a collision is detected, the relay control unit 23 stops outputting signals to the relays 22a and 22b. Further, for example, when the occurrence of an abnormal event such as a collision is detected, the path through which signals output from the relay control unit 23 to the relays 22a and 22b pass is blocked.

  When the signals output from the relay control unit 23 to the relays 22a and 22b are cut off, the contacts of the relays 22a and 22b are opened. When the contacts of the relays 22a and 22b are opened, the capacitors 21a, 21b, and 21c are disconnected one by one.

  The voltage of each separated capacitor is 1/3 of the voltage between AB when the capacitors are connected in series even if the discharge treatment is not performed. As described above, even when the discharge process is not performed, it is possible to simply create a state where the voltages of the capacitors 21a, 21b, and 21c are equal to or lower than a predetermined voltage value (for example, a voltage value that is harmless to the human body).

  Even if the signal generation from the relay control unit 23 is disabled due to the occurrence of an abnormal event such as a collision, the connection between the capacitors is automatically disconnected if the relays 22a and 22b are normally open. So the high voltage will never remain charged.

  As mentioned above, although the smoothing circuit for vehicles was demonstrated by the embodiment, this invention is not limited to the said embodiment. Various modifications and improvements, such as combinations and substitutions with part or all of other example embodiments, are possible within the scope of the present invention.

  For example, “when an abnormal event such as a collision occurs” may include a meaning when an abnormal event such as a collision may occur. The occurrence of an abnormal event is detected by, for example, a sensor that predicts the occurrence of the abnormal event or the occurrence thereof. The occurrence of the collision is detected by, for example, a radar or a camera.

  Further, the smoothing circuit may be built in the inverter or disposed outside the inverter. Further, the smoothing circuit may be a circuit that smoothes a DC voltage input / output to / from the converter, and may be built in the converter or disposed outside the converter.

  Further, the capacitances of the plurality of capacitors may be equal to or different from each other. Further, the number of capacitors connected in series may be two, or four or more.

  In addition, although an example in which a normally open type relay is used for separation between capacitors has been shown, a semiconductor switch such as a transistor may be used as long as it has a function of disconnecting connections between capacitors.

DESCRIPTION OF SYMBOLS 10 Battery 11 Relay 12, 13 Power supply path 20 Inverter 21a, 21b, 21c Capacitor 22a, 22b Relay (example of a dividing means)
23 Relay control unit (example of dividing means)
24 Smoothing circuit (example of vehicle smoothing circuit)
25 Inverter control unit 26 Inverter circuits 26a, 26b, 26c, 26d, 26e, 26f Inverter element 27 Positive bus 28 Negative bus 30 Motor 100 Power conversion system

Claims (1)

A smoothing circuit for a vehicle in which a plurality of capacitors are connected in series,
A smoothing circuit for a vehicle, comprising a dividing means for dividing the connection between the capacitors at the time of a vehicle collision.

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