JP2015107045A - Charge and discharge circuit and motor control device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge and discharge circuit that allows being downsized by using a charging resistor also as a precharging resistor for a smoothing capacitor, and to provide a power conversion device including the charge and discharge circuit.SOLUTION: A charge and discharge circuit 3 includes a power-supply relay 4 controlling power supply to an inverter 12, a precharge circuit 7 precharging a smoothing capacitor 11 before turning on the power-supply relay 4, and a discharge circuit 8 discharging charges stored in the smoothing capacitor 11. The precharge circuit 7 includes a series connection of a precharge relay 5 and a charge and discharge resistor 6, is connected in parallel to a contact point of the power-supply relay 4, and precharges the smoothing capacitor 11 through the charge and discharge resistor 6 by turning on the precharge relay 5 when the power-supply relay 4 is in an off-state. The charge and discharge resistor 6 functions as a resistor for inrush current prevention that limits an inrush current of the smoothing capacitor 11. The charge and discharge resistor 6 prevents the flow of a large inrush current immediately after the power-supply relay 4 is switched to on.

Description

  The present invention relates to a charge / discharge circuit and a motor control device including the charge / discharge circuit, and more particularly to a charge / discharge circuit used for driving and controlling an electric motor mounted on a vehicle and a motor control device including the charge / discharge circuit. .

  Conventionally, a relay is generally used to control power supply from a high voltage battery to an electric motor or the like. For example, in an electric vehicle such as a hybrid vehicle, an electric vehicle, or an electric four-wheel drive vehicle, a power relay is connected between the battery and the inverter in order to control power supply from the high-voltage battery to the inverter that is a load circuit. The battery relay and the inverter are connected and opened by this power relay according to the vehicle control state. In such a case, a large inrush current flows instantaneously to charge a large-capacity smoothing capacitor connected between the power supply line and the earth line from the battery, and the contact of the power supply relay is welded. There is. When this contact is welded, the problem arises that the power relay cannot be switched off and the current cannot be interrupted. Therefore, a power supply device having a precharge circuit that precharges the smoothing capacitor before switching the power relay on is proposed. Has been.

  Further, in such a power supply device, for safety, it is necessary to reliably discharge the power supply line in which the electric charge accumulated in the smoothing capacitor remains when power supply to the inverter is stopped. Conventionally, for such a discharge process, a power supply device is disclosed in which a discharge circuit including a discharge resistor and a discharge relay that is turned on when power supply is stopped is connected in parallel between a power supply line and an earth line ( For example, see Patent Document 1).

JP 2005-73399 A

  In such a power supply device, the precharge circuit includes a precharge resistor (inrush current suppression resistor) for limiting an inrush current, and a precharge relay connected in series to the precharge resistor, The relay is turned on to precharge the smoothing capacitor connected in parallel with the inverter. After the smoothing capacitor is precharged, the power supply relay connected in parallel with the precharge circuit is switched on, and then the battery is connected to the inverter. Then, after the power relay is switched on, the precharge relay is switched off. In addition, the discharge circuit controls on / off of the discharge relay so that only the electric charge remaining in the smoothing capacitor is consumed by the discharge resistor after the power supply relay is switched off and power supply to the inverter is stopped.

  In the conventional configuration described above, the precharge resistor and the discharge resistor do not operate simultaneously, and resistors having comparable resistance values and rated power are used. However, compared with other electronic components that require a large amount of power, the two components have a large heat capacity and are very large, so that the power conversion device (motor control device) including the charge / discharge circuit itself becomes large. In addition, when a small-sized resistor is used, derating (withstand power) is reduced and the thermal reliability of the component is lowered. In addition, the high price of the resistance causes a cost increase.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a charge / discharge circuit capable of reducing the size by using the precharge resistor of the smoothing capacitor as the discharge resistor, and a motor control device including the charge / discharge circuit. It is to provide.

  In order to solve the above-mentioned problem, the invention described in claim 1 is a charge / discharge circuit comprising a DC power source for driving an electric motor and a motor drive circuit that includes a plurality of switching elements and supplies a drive current to the electric motor. A power supply relay for turning on / off connection, and a power supply line connected between the power supply relay and the motor drive circuit and a ground line in series, and a current connected between the power supply line and the ground line A charge / discharge resistor connected in parallel to a smoothing capacitor that absorbs ripple, one end connected to the power line, a discharge switch connected to the ground line, one end connected to the DC power source, and the other end A precharge relay connected between the charge / discharge resistor and the discharge switch, and the charge accumulated in the smoothing capacitor is A discharge circuit that discharges through the charge / discharge resistor by turning on a discharge switch; and the power supply relay is bypassed to connect the DC power supply and the smoothing capacitor by turning on the precharge relay to connect the charge / discharge resistor. And a precharge circuit for precharging the smoothing capacitor.

  According to the above configuration, the charge / discharge resistor and the discharge switch connected in series are connected in parallel to the smoothing capacitor, and the power relay connected between the DC power supply and the motor drive circuit between the charge / discharge resistor and the discharge switch; Since the precharge relay is connected in parallel, the charging current flows from the precharge relay through the charge / discharge resistor at the start of charging of the smoothing capacitor and precharge is performed. When the discharge of the smoothing capacitor is started, the power supply relay is in the off state, and the charge accumulated in the smoothing capacitor is discharged through the charge / discharge resistor by switching the discharge switch to the on state. Thereby, since the precharge resistor can be abolished by using the charge / discharge resistor as a precharge resistor for preventing rush current during charging, the number of components of the large resistor can be reduced. As a result, the charge / discharge circuit can be reduced in size and cost.

  According to a second aspect of the present invention, in the charge / discharge circuit according to the first aspect, the resistance value of the charge / discharge resistor is greater than a ratio of a direct current voltage of the direct current power supply and a charge current for precharging the smoothing capacitor. The gist of the present invention is that it is larger and smaller than the ratio of the charging voltage of the smoothing capacitor and the discharge current flowing through the charge / discharge resistor.

  According to the above configuration, in the charge / discharge circuit, by setting the resistance value of the charge / discharge resistor within a predetermined range, the precharge of the smoothing capacitor can be performed without reducing the derating even when a small-sized resistor is selected. In addition, it is possible to share the functions of two resistors that perform the discharge operation.

  The gist of a third aspect of the present invention is that the motor control device includes the charge / discharge circuit according to the first or second aspect. According to the above configuration, since the motor control device includes the charge / discharge circuit in which the precharge resistance of the smoothing capacitor is also used as the charge / discharge resistance, the motor control device itself can be reduced in size and cost.

  ADVANTAGE OF THE INVENTION According to this invention, the charging / discharging circuit which can use the precharging resistance of a smoothing capacitor also as charging / discharging resistance and can be reduced in size, and a motor control apparatus provided with the same can be provided.

The figure which shows schematic structure of the drive system of the vehicle carrying the motor control apparatus containing the power supply circuit which concerns on one Embodiment of this invention. The figure which shows the circuit structure of the motor control apparatus containing the power supply circuit of FIG. The flowchart which shows the process sequence at the time of charge of the smoothing capacitor performed with a control circuit. The flowchart which shows the process sequence at the time of discharge of the smoothing capacitor performed with a control circuit.

Below, the charge / discharge circuit of the motor control apparatus mounted in the vehicle which concerns on embodiment of this invention is demonstrated based on figures.
FIG. 1 is a diagram showing a schematic configuration of a vehicle drive system equipped with a vehicle motor control device 15 including a power supply circuit 2 according to an embodiment of the present invention. As shown in FIG. 1, a vehicle (in this embodiment, an electric four-wheel drive vehicle) includes a DC power source (hereinafter referred to as a high voltage battery) 13, a vehicle control unit 18, a rear wheel drive unit 20, and DC power. A vehicle motor control device (ECU, hereinafter referred to as a motor control device) 15 that controls the electric motor 1 that is a power conversion device that converts AC power and is used to drive the rear wheels 19 is provided. The rear wheel drive unit 20 includes an electric motor 1, a reduction gear (differential gear) 16, and a clutch 17, and the clutch 17 is installed at the final stage of the reduction gear 16. For example, a three-phase brushless motor is used as the electric motor 1 for the drive source. The electric motor 1 is a permanent magnet type such as an IPM motor having an embedded magnet type rotor in which a permanent magnet is embedded and fixed in a rotor core, and an SPM motor having a surface magnet type rotor in which a permanent magnet is fixed to the surface of the rotor core. A synchronous motor is used.

  The high-voltage battery 13 is a high-voltage (for example, 250 V) DC power source, and is composed of, for example, a rechargeable battery such as nickel hydride or lithium ion that can be charged and discharged, and is disposed, for example, behind a rear seat of a vehicle. . The motor control device 15 boosts the DC voltage received from the high-voltage battery 13 to a higher voltage (for example, 600 V or the like) by the power supply circuit 2 in accordance with the specifications of the inverter 12 that is a motor drive circuit (or remains unboosted) ) And supply to the inverter 12. Further, the motor control device 15 supplies and charges the high-voltage battery 13 with the electric power generated by the electric motor 1 during regenerative braking of the electric motor 1. The motor control device 15 is mounted, for example, under the rear seat of the vehicle.

  The motor control device 15 also includes a control circuit (signal processing circuit) 10 that controls the rear wheel drive unit 20 and the like. The control circuit 10 is connected to an auxiliary power source (hereinafter referred to as a low voltage battery) 14 having a low voltage (for example, 12V), and is connected to the in-vehicle network via a communication line (harness) from a vehicle control unit 18 that controls driving of the vehicle. In response to a command (for example, CAN), the clutch 17 is engaged, and the driving force generated when the electric motor 1 is driven is transmitted to the rear wheel 19. Further, when a higher DC voltage is required, the motor control device 15 boosts the DC voltage of the high voltage battery 13 by a boost converter (not shown), and stabilizes it by the internal smoothing capacitor 11 (see FIG. 2). The power supply circuit 2 to be activated and the inverter 12 are included.

  Next, FIG. 2 is a diagram showing a circuit configuration of the motor control device 15 including the power supply circuit 2 of FIG. As shown in FIG. 2, the power supply circuit 2 includes a charge / discharge circuit 3 and a smoothing capacitor 11. The charge / discharge circuit 3 is connected to the positive and negative output sides of the high-voltage battery 13, and includes a power relay 4 that controls power supply to the inverter 12 and a large-capacity smoothing capacitor 11 before the power relay 4 is turned on. A precharge circuit 7 for precharging and a discharge circuit 8 for discharging the electric charge accumulated in the smoothing capacitor 11 after the power supply relay 4 is turned off to consume power when the inverter 12 is stopped are provided. An inverter 12 is connected in parallel to the smoothing capacitor 11, and the electric motor 1 is connected via the inverter 12. The precharge relay 5 and the power supply relay 4 are controlled by the control circuit 10.

  The precharge circuit 7 is formed by connecting a precharge relay 5 and a charge / discharge resistor (precharge resistor) 6 in series. The precharge circuit 7 is connected in parallel to the contact of the power relay 4 and switches the precharge relay 5 on when the power relay 4 is in an off state, and smoothing the capacitor while limiting the inrush current through the charge / discharge resistor 6. 11 is precharged. The charge / discharge resistor 6 functions as an inrush prevention resistor that limits the inrush current of the smoothing capacitor 11. The charge / discharge resistor 6 prevents a large inrush current from flowing immediately after the power supply relay 4 is switched on, and the smoothing capacitor 11 is precharged via the charge / discharge resistor 6 when the power supply relay 4 is in the off state. Is done.

  The power relay 4 is a power switch that is arranged in the charge / discharge circuit 3 and switches whether the smoothing capacitor 11 and the inverter 12 are connected to the high-voltage battery 13, and has a mechanically movable contact. The power supply relay 4 is turned on (conductive state) when the motor control device 15 is operating, and is turned off (non-conductive state) when stopped. Further, the power supply relay 4 switches on the precharge relay 5 of the precharge circuit 7 in the off state and precharges the smoothing capacitor 11 through the charge / discharge resistor 6. After the smoothing capacitor 11 is precharged, the power supply relay 4 is switched from OFF to ON, and the high voltage battery 13 is directly connected to the inverter 12. Thereafter, the precharge relay 5 is switched off.

  The smoothing capacitor 11 is provided between the power supply line 21 and the earth (ground) line 22. The smoothing capacitor 11 supplies power to the inverter 12 from both the high voltage battery 13 and the power supply relay 4 in the on state. In particular, the smoothing capacitor 11 instantaneously supplies high power to the inverter 12. Specifically, the smoothing capacitor 11 accumulates electric charge, and discharges the accumulated electric charge when the current flowing from the high voltage battery 13 to the inverter 12 is insufficient. Thus, the smoothing capacitor 11 functions as a capacitor that absorbs current ripple and smoothes the power supply voltage for driving the electric motor 1. Further, in the power supply circuit 2 of the present embodiment, after the power supply relay 4 is turned off, the charge accumulated in the smoothing capacitor 11 is discharged through the discharge circuit 8.

  The discharge circuit 8 is formed by connecting a discharge switch (for example, IGBT, MOSFET, etc.) 9 and a charge / discharge resistor 6 in series, and is provided between the power supply line 21 and the earth line 22 in parallel with the smoothing capacitor 11. ing. When the power relay 4 is cut off and the driving of the electric motor 1 is stopped, the electric charge accumulated in the smoothing capacitor 11 is discharged through the charging / discharging resistor 6 by turning on the discharge switch 9, and the smoothing capacitor 11 The voltage Vd decreases rapidly.

  In FIG. 2, the electric motor 1 is a three-phase brushless motor having three-phase windings (U-phase winding, V-phase winding, and W-phase winding, not shown). The high voltage battery 13 is a high voltage DC power source that is connected to the inverter 12 and drives the electric motor 1.

  The inverter 12 includes six switching elements (power transistors such as IGBT, MOSFET, etc.) U1, U2, V1, V2, W1, and W2. Three circuits in which the six switching elements U1, U2, V1, V2, W1, and W2 are connected in series to form upper and lower arms (for example, U1 and U2) are composed of a power supply line 21 and an earth line. 22 in parallel. Each connection point of the switching elements of the upper and lower arms is directly connected to one end of the U-phase winding, the V-phase winding, and the W-phase winding. The other end of the three-phase winding of the electric motor 1 is connected to a common connection point (neutral point, not shown).

  The control circuit 10 controls switching elements U1, U2, V1, V2, W1, and W2 included in the inverter 12. More specifically, the control circuit 10 determines the three-phase drive current (U-phase current, V-phase current, and W-phase current) to be supplied to the electric motor 1 based on the input data (rotation angle and the like). A target value (target current) is determined, and a PWM signal for matching the current (each phase current value) detected by a current sensor (not shown) with the target current is output. The PWM signal of each phase output from the control circuit 10 is supplied to the gate terminals of the switching elements U1, U2, V1, V2, W1, and W2 included in the inverter 12, respectively. Note that a control voltage (for example, 12 V) serving as a power source for the control circuit 10 is supplied from the low voltage battery 14. The low voltage battery 14 may be equipped with an auxiliary battery, or may be supplied with power from the high voltage battery 13 via a DC / DC converter or the like.

  The charge / discharge resistor 6 is used during two operations of precharging and discharging the smoothing capacitor 11, and a charge / discharge current flows. At the start of precharge, a resistance for preventing inrush (high effect when the resistance is high) is required to suppress the inrush current, and at the start of discharge, the charge accumulated in the smoothing capacitor 11 is discharged in a short time. In addition, a resistance for discharging (high effect when the resistance value is low) is required. Here, as the charge / discharge resistor 6, a large resistor having a resistance value R represented by Va / Ic <R <Vd / Id (for example, 500Ω, 50W, enamel resistor, cement resistor, etc.) is used. (However, Vd≈Va, R: resistance value, Va: battery voltage, Ic: charging current, Vd: smoothing capacitor voltage, Id: discharging current)

Next, the charge / discharge operation of the power supply circuit 2 in the present embodiment will be described.
FIG. 3 is a flowchart showing a processing procedure at the time of charging the smoothing capacitor 11 executed by the control circuit 10, and FIG. 4 is a flowchart showing a processing procedure at the time of discharging the smoothing capacitor 11 executed by the control circuit 10.

  The charging / discharging operation of the smoothing capacitor 11 is performed by the control circuit 10 when the vehicle control is stopped, that is, when the motor control device 15 that drives the electric motor 1 is started and stopped. In the present embodiment, a CPU (not shown) in the control circuit 10 reads a program stored in the ROM, and steps S301 to S305 shown in the flowchart of FIG. 3 and steps S401 to S404 shown in the flowchart of FIG. Execute the process. The processing in the flowchart shown below is executed at predetermined time intervals.

  Before the power relay 4 is turned on, the voltage Vd of the smoothing capacitor 11 is precharged. When the power relay 4 is normal, the voltage Vd of the smoothing capacitor 11 is charged up to the battery voltage Va of the high voltage battery 13. The power relay 4 is switched on. On the other hand, when the discharge switch 9 is turned on, the electric charge accumulated in the smoothing capacitor 11 is discharged through the charging / discharging resistor 6, whereby the voltage Vd of the smoothing capacitor 11 rapidly decreases.

  As shown in FIG. 3, the CPU of the control circuit 10 in the motor control device 15 first turns off the discharge switch 9 and switches off the power supply relay 4 (step S301). Subsequently, the precharge relay 5 is switched on (step S302), and the precharge of the smoothing capacitor 11 is started.

  Next, the CPU determines whether or not the voltage Vd of the smoothing capacitor 11 has increased to the battery voltage Va after a predetermined time has elapsed (step S303). The precharge is continued until the voltage Vd reaches the battery voltage Va (step S303: NO). When the precharge is completed (step S303: YES), the power supply relay 4 is switched on (step S304), and the precharge relay 5 Is switched off (step S305), and after precharging is stopped, the flow is exited. Thereafter, the CPU executes a drive process of the inverter 12.

  Next, as shown in FIG. 4, the CPU of the control circuit 10 in the motor control device 15 executes the inverter drive stop process, then switches off the power supply relay 4 (step S <b> 401), and turns on the discharge switch 9. Switching is performed (step S402), the discharge circuit 8 is turned on, and the discharge of the charge accumulated in the smoothing capacitor 11 is started.

  Subsequently, the CPU determines whether or not the voltage Vd of the smoothing capacitor 11 has decreased to 0 after a predetermined time has elapsed (step S403). Discharging is continued until the voltage Vd becomes equal to or lower than the predetermined value (step S403: NO), and when the discharging of the smoothing capacitor 11 is completed (step S403: YES), the discharge switch 9 is switched off (step S404). After stopping the discharge, exit the flow.

  Next, the operation and effect of the charging / discharging circuit 3 according to the present embodiment configured as described above and the motor control device 15 including the same will be described.

  According to the above configuration, the smoothing capacitor 11 is connected in parallel to the inverter 12 in the power supply circuit 2 connected between the high voltage battery (DC power supply) 13 and the inverter (motor drive circuit) 12. The smoothing capacitor 11 limits the inrush current through the charge / discharge resistor 6 by turning on the precharge relay 5 of the precharge circuit 7 before turning on the power supply relay 4 when the discharge switch 9 of the discharge circuit 8 is turned off. While being precharged. The precharge relay 5 and the charge / discharge resistor 6 constituting the precharge circuit 7 are provided in parallel with the power supply relay 4, and the voltage Vd of the smoothing capacitor 11 is precharged to the battery voltage Va by the precharge circuit 7. The

  Further, when the precharge relay 5 of the precharge circuit 7 is in the off state, the charge remaining in the smoothing capacitor 11 is discharged through the charging / discharging resistor 6 by switching the discharge switch 9 of the discharge circuit 8 on, and the smoothing capacitor 11 The voltage Vd decreases rapidly. Further, the charge / discharge resistor 6 can set a resistance value R within a predetermined range as a resistor shared by charge / discharge.

  As a result, the charging / discharging resistor 6 can be used as an inrush preventing precharge resistor that suppresses the inrush current from flowing during charging. Therefore, the precharge resistor is eliminated and charging / discharging is achieved by reducing the number of parts of the large resistor. The circuit 3 can be reduced in size and cost. In addition, by setting the resistance value R of the charge / discharge resistor 6 in the charge / discharge circuit 3 within a predetermined range, the precharge of the smoothing capacitor 11 can be performed without derating even if a small size resistor is selected. In addition, it is possible to share the two functions of discharging with a single resistor. Furthermore, since the motor control device 15 includes the charge / discharge circuit 3 in which the precharge resistor of the smoothing capacitor 11 is also used as the charge / discharge resistor 6, the motor control device 15 itself can be reduced in size and cost.

  As described above, according to the embodiment of the present invention, it is possible to provide a charge / discharge circuit capable of reducing the size by using the precharge resistor of the smoothing capacitor also as the charge / discharge resistor, and a power conversion device including the charge / discharge circuit.

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

  In the above embodiment, the power supply relay 4 and the precharge relay 5 are controlled to be turned on / off by using a normal relay (mechanical type). An on / off operation may be performed using a switch (for example, using a plurality of MOSFETs). Further, a mechanical relay may be used for the discharge switch 9.

  In the above embodiment, the charging / discharging process procedure of the smoothing capacitor 11 has been described assuming that the power supply relay 4 and the precharge relay 5 are normal. However, the present invention is not limited to this, and the power supply relay 4 is included in the charging / discharging process. Alternatively, a process for detecting an open abnormality or a short abnormality of the precharge relay 5 may be executed.

  In the above embodiment, the example in which the present invention is applied to the inverter 12 for driving the rear wheel drive unit 20 of the vehicle has been described. However, the present invention is not limited to this, and the discharge circuit 8 is provided. You may make it apply to inverters, such as an electric power steering device of an electric current, and an electric brake device, or another vehicle-mounted power converter device. Moreover, you may apply to the inverter which drives the motor for driving | running | working of a hybrid vehicle or an electric vehicle.

1: electric motor, 2: power supply circuit, 3: charge / discharge circuit, 4: power supply relay,
5: precharge relay, 6: charge / discharge resistor, 7: precharge circuit, 8: discharge circuit,
9: discharge switch, 10: control circuit, 11: smoothing capacitor,
12: Inverter (motor drive circuit), 13: High voltage battery (DC power supply),
14: Low-voltage battery, 15: Motor control unit (ECU), 16: Reducer, 17: Clutch, 18: Vehicle control unit, 19: Rear wheel, 20: Rear wheel drive unit,
21: Power supply line, 22: Earth (ground) line,
U1, U2, V1, V2, W1, W2: switching element, Vd: smoothing capacitor voltage, Va: battery voltage, R: charge / discharge resistance value

Claims (3)

A power supply relay for turning on / off a connection between a DC power source for driving the electric motor and a motor driving circuit that includes a plurality of switching elements and supplies a driving current to the electric motor;
Connected in series between the power supply line and the ground line between the power relay and the motor drive circuit, and connected in parallel to a smoothing capacitor connected between the power supply line and the ground line to absorb current ripple. A charge / discharge resistor having one end connected to the power supply line and a discharge switch having one end connected to the ground line;
A precharge relay having one end connected to the DC power source and the other end connected between the charge / discharge resistor and the discharge switch;
A discharge circuit for discharging the charge accumulated in the smoothing capacitor through the charge / discharge resistor by turning on the discharge switch; bypassing the power supply relay; turning on the precharge relay to turn on the DC power supply and the smoothing capacitor A charge / discharge circuit comprising: a precharge circuit that connects capacitors and precharges the smoothing capacitor via the charge / discharge resistor. The charge / discharge circuit according to claim 1,
The resistance value of the charge / discharge resistor is greater than a ratio of a DC voltage of the DC power supply and a charge current for precharging the smoothing capacitor, and a discharge current flowing through the charge voltage of the smoothing capacitor and the charge / discharge resistor. Charge / discharge circuit characterized by being smaller than the ratio.   A motor control device comprising the charge / discharge circuit according to claim 1.

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