JP2009159755A - Motor drive circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive circuit in which a motor driver is reliably separated from a motor battery and after the separation of the driver, the motor battery continues to supply power to an auxiliary device. <P>SOLUTION: The motor drive circuit 10 includes a DC-DC converter 18 which reduces the voltage of power from the high-voltage battery 12 to supply the power reduced in voltage to the auxiliary device 16, an inverter circuit 58 which drives a motor 14 and supplies regenerated power to the battery 12, a contactor 22 disposed on a positive power line P2 connecting a positive terminal 12p of the battery 12 to a positive line 20p of the inverter circuit 58, a connection line N2 connecting a ground line 18n of the DC-DC converter 18 to a ground line 20n of the inverter circuit 58, a switching element 24 disposed on a negative power line N1 connecting the connection line N2 to a negative terminal 12n, and a diode 76 arranged in parallel with the switching element 24. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor drive circuit applied to an electric vehicle or the like, and more particularly to a motor drive circuit that supplies electric power from a battery to an auxiliary machine having a lower voltage than a voltage for driving the motor and the motor.

  Recently, electric vehicles and hybrid vehicles using a motor as a drive source have been developed, and some of them have been put into practical use. In order to drive a motor in such a vehicle, a high voltage is used, and a battery for high voltage is mounted in addition to a normal 12V battery, and a DC is connected between different voltage systems for power interchange.・ DC converter is applied.

  In such a vehicle, energy efficiency is improved by using a motor as a generator and charging a battery with a regenerative current during braking or deceleration.

  On the other hand, when such regeneration is performed, the battery may be overcharged. Therefore, the voltage is monitored and the regeneration is stopped before overcharging. Further, the power supply to the driver may be stopped depending on the state of the driver or a peripheral circuit. For this purpose, a contactor that can be opened and closed is provided between the battery and the driver (see, for example, Patent Document 1).

  On the other hand, if the contactor is disconnected and power supply is stopped while power is being supplied from the battery to the driver, an arc may be generated in the contactor, so a semiconductor element is provided in parallel to the contactor. In addition, it has been proposed to prevent the arc by controlling the contactor while passing a current through the semiconductor element (see, for example, Patent Document 2 and Patent Document 3).

Japanese Utility Model Publication No. 62-11301 Japanese Utility Model Publication No. 3-803 Japanese Utility Model Publication No.59-28201

  As described in Patent Document 2 and Patent Document 3, when a semiconductor element is provided for a contactor, generation of an arc in the contactor can be prevented, but it is desirable to provide a flywheel diode to protect the semiconductor element.

  However, if a flywheel diode is provided in parallel to the semiconductor element, even if the contactor is disconnected, a current flows in one direction by the flyhole diode.

  In addition, it is desirable that the power supply can be continued to other auxiliary machines even after the driver is disconnected from the battery. A dedicated 12V battery may be provided for the auxiliary equipment, but coexistence of a high voltage battery for the motor and a 12V battery from the viewpoint of layout space, wiring complexity, weight increase, and cost increase Not desirable. In particular, in the case of a vehicle having a limited layout space such as a motorcycle, it is not preferable to mount two batteries.

  The present invention has been made in consideration of such a problem, and the motor driver can be surely disconnected from the battery, the generation of an arc can be suppressed in the operating portion to be disconnected, and the driver is disconnected. Another object of the present invention is to provide a motor drive circuit that can continue to supply power to the auxiliary machine from the battery for the motor.

  The motor drive circuit according to the present invention has the following features.

  1st characteristic; It is a motor drive circuit which supplies electric power from a battery provided with a 1st pole and a 2nd pole with respect to a motor and an auxiliary machine of voltage lower than the voltage which drives the motor, Comprising: It supplies from the battery A DC / DC converter that steps down the voltage and supplies the auxiliary machine with the driver, and a driver that controls the electric power supplied from the battery to drive the motor and regenerates the electric power generated by the rotation of the motor to the battery A contactor including a mechanical contact provided in a first power supply line connecting the first pole of the battery and the first pole line of the driver; the second pole line of the DC / DC converter; and the driver A connection line connecting the second pole line, and switching means provided on a second power supply line connecting the connection line and the second pole of the battery; The parallel to the switching means, and having a diode which is provided in a direction to allow the discharge direction of the current of the battery.

  Thus, by providing the switching element in the power supply line that connects the connection line and the second electrode of the battery, the motor driver can be reliably disconnected from the battery, and the generation of arcs in the disconnecting contactor is suppressed. be able to.

  2nd characteristic; It has an overvoltage detection means which detects the overvoltage of the said battery and the said driver, The said switching means is switching-controlled by the said overvoltage detection means, It is characterized by the above-mentioned. Thereby, generation | occurrence | production of the overvoltage with respect to a battery and a driver can be prevented.

  Third feature: The switching means is a semiconductor element. The semiconductor element is excellent in controllability, durability, and ease of mounting, and is suitable for switching means in a motor drive circuit.

  Fourth feature: The semiconductor element is mounted on a substrate of the driver. Thereby, it is not necessary to provide a dedicated substrate for the semiconductor element.

  5th characteristic; The said semiconductor element is attached to the heat dissipation means common with the semiconductor element of the inverter circuit which supplies an electric current to the said motor. Thereby, it is not necessary to provide a heat sink dedicated to the semiconductor element.

  According to the motor drive circuit of the present invention, by providing the switching element in the power supply line that connects the connection line and the second pole of the battery, the motor driver can be reliably disconnected from the battery and disconnected. The generation of arc can be suppressed.

  Further, the switching element is provided with a diode in parallel, and power can be continuously supplied from the battery to the auxiliary machine even after the driver is disconnected by the switching element.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a motor drive circuit according to the present invention will be described with reference to FIGS. The motor drive circuit 10 according to the present embodiment is applied to, for example, an electric motorcycle.

  As shown in FIG. 1, a motor drive circuit 10 according to the present embodiment is a circuit that drives a motor 14 with electric power supplied from a battery 12, and an auxiliary machine 16 that has a lower voltage than the voltage that drives the motor 14. Also, power is supplied from the battery 12. The battery 12 is, for example, a lithium ion type secondary battery. In FIG. 1, the power lines are distinguished by thick lines and the signal lines are distinguished by thin lines.

  The motor 14 is for driving a vehicle and drives a tire (not shown). When the vehicle is braked or decelerated, the motor 14 acts as a generator and can recharge the battery 12. Thus, although the motor 14 also has a function as a generator, it is called a motor for convenience. The battery 12 has a voltage specification of 36V, for example, and the motor 14 has a specification of 36V drive. The battery 12 can be charged and discharged at about 37 V with a margin. The motor 14 can be driven with a margin of about 37V.

  The motor drive circuit 10 includes a battery 12, a motor 14, an auxiliary machine 16, a DC / DC converter 18, a power drive unit (driver) 20, a contactor 22, a switching element (switching means) 24, and an overvoltage detection circuit 25. The contactor 22 performs on / off control by a mechanical contact that operates by electromagnetic force. According to the contactor 22, the power drive unit 20 and the battery 12 can be separated from each other, so that the capacity of the battery 12 can be prevented from being reduced by dark current, and the maintainability can be improved.

  The auxiliary machine 16 has, for example, a 12V specification and includes a meter 26, an ECU 28, and a general electrical component 30. A power line is connected to the general electrical component 30 via a switch 32. The meter 26 includes a speedometer, a rotation speed meter of the motor 14, an odometer, and the like. The general electrical component 30 includes a light, an air conditioner, an audio device, and the like. The switch 32 is a small low-priced product with a low withstand voltage, and the DC / DC converter 18 can be turned on / off via the relay 34.

  The auxiliary machine 16 is supplied with electric power from the battery 12 through the DC / DC converter 18 by reducing the voltage to 12V (or about 13V with a margin). In the motor drive circuit 10, the dedicated low voltage battery for the auxiliary machine 16 is not provided, and the high voltage battery 12 is also used. Thereby, effective use of layout space, ease of wiring, weight reduction, and cost reduction can be achieved.

  Each ground line of the auxiliary machine 16 is connected to the DC / DC converter 18, and is connected to the ground line 18 n in the DC / DC converter 18.

  The DC / DC converter 18 includes a relay 34 that is opened and closed by a switch 32 to control on / off, a step-down converter 36 that steps down the voltage supplied from the relay 34 to 12V and supplies the auxiliary device 16, and a 12V voltage. A boost converter 38 that boosts the voltage to 36 V (or about 37 V) and supplies the boosted voltage to the power drive unit 20 and a voltage detection circuit 40 that detects an input voltage of the buck converter 36 are included. The boost converter 38 corresponds to, for example, a kick starter (not shown), and can boost a voltage generated by the kick starter to obtain a voltage at which the ECU 28 and the like can operate stably. According to the kick starter, for example, the vehicle can be started even when the voltage of the battery 12 is low.

  The voltage detection circuit 40 detects electric power generated by the motor 14 in an uncontrolled state when the crankshaft is turned with the switch 32 turned off, and outputs it from the DC / DC converter 18 to output the ECU 28 and the power drive unit. 20 is provided to start power generation control of the motor 14.

  A forward diode 42 is provided between the relay 34 and the step-down converter 36, and a diode 44 is provided between the voltage detection circuit 40 and the input line of the step-down converter 36.

  The battery 12 has a plus terminal (first pole) 12p and a minus terminal (second pole) 12n. The positive terminal 12p is connected to the positive line 18p of the DC / DC converter 18 via the positive power line P1, and to the positive line 20p of the power drive unit 20 via the contactor 22 via the positive power line (first power line) P2. Connected. The positive power lines P1 and P2 may be independently connected to the positive terminal 12p, or may be branched in the middle with a common connection line to the positive terminal 12p.

  The negative terminal 12n of the battery 12 and the power drive unit 20 are connected by a negative power line (second power supply line) N1. The negative power line N1 is connected to the ground line (second pole line) 20n through the switching element 24 in the power drive unit 20.

  The ground line 20n of the power drive unit 20 and the ground line (second pole line) 18n of the DC / DC converter 18 are connected by a connection line N2.

  The power drive unit 20 includes a control circuit 50, a step-down converter 52, a step-up converter 54, a predrive circuit 56, and an inverter circuit 58.

  The step-down converter 52 receives a 12V system power line supplied to the auxiliary machine 16 and steps down a 12V voltage (or a voltage of about 13V) to 5V and supplies it to the control circuit 50. The control circuit 50 is connected to the ECU 28 via a communication line 59, and performs bidirectional communication (for example, CAN communication). The control circuit 50 operates using the supplied 5V voltage as electric power, and controls the contactor 22 open / close control and the pre-drive circuit 56 based on information obtained from the ECU 28. The control circuit 50 and the overvoltage detection circuit 25 are connected by a signal line, and information exchange is possible.

  The step-up converter 54 receives the 12V system power line supplied to the auxiliary machine 16, boosts the voltage of 12V (or about 13V) to 15V, and supplies it to the pre-drive circuit 56. The pre-drive circuit 56 operates using the supplied 15V voltage as power, and controls the inverter circuit 58.

  The inverter circuit 58 includes three switching element pairs 60a, 60b and 60c connected in series between the plus line 20p and the ground line 20n. Each switching element pair 60 a to 60 c has a series connection configuration of an upper arm 62 and a lower arm 64, and each connection line is connected to the motor 14 as a three-phase output. Each of the upper arm 62 and the lower arm 64 is a semiconductor element, and its gate is individually connected to the predrive circuit 56. In the pre-drive circuit 56, these gates are controlled to convert the DC voltage between the plus line 20p and the ground line 20n into a three-phase AC having a desired frequency and supply it to the motor 14, or the motor 14 generates power. The generated power is converted into direct current, and the battery 12 is regenerated and charged.

  The inverter circuit 58 is provided with a driver overvoltage detection circuit 61 that detects an overvoltage in the circuit and supplies a detection result to the control circuit 50.

  The switching element 24 is, for example, a MOS-FET, the gate 70 is connected to the overvoltage detection circuit 25, the drain 72 is connected to the negative power line N1, and the source 74 is connected to the ground line 20n. The overvoltage detection circuit 25 monitors the voltage of the battery 12 and controls the gate of the switching element 24 to turn off the switching element 24 when an overvoltage is detected. A means for controlling the switching element 24 by detecting the temperature of the battery 12 by replacing or coexisting with the overvoltage detection circuit 25 may be provided.

  The switching element 24 is provided with a diode 76 as a parasitic diode in parallel, and is set in a direction that allows current in the discharging direction of the battery 12 (the direction from right to left on the negative power line N1 in FIG. 1). . That is, the cathode side of the diode 76 is connected to the negative power line N1, and the anode side is connected to the ground line 20n. The diode 76 connected in parallel to the switching element 24 may be internal, external, or a combination thereof.

  The switching element 24 is provided in the inverter circuit 58. The switching element 24 is mounted on the substrate of the inverter circuit 58, and it is not necessary to provide a substrate dedicated to the switching element 24.

  As shown in FIG. 2, the switching element 24 is attached to a common heat radiating plate (heat radiating means) 78 together with the switching element pairs 60 a to 60 c. As a result, there is no need to provide a heat sink dedicated to the switching element 24, and a space-saving and simple configuration is obtained. The heat radiating means of the switching element 24 and the switching element pairs 60a to 60c is not limited to the heat radiating plate 78, and may be, for example, a cooling conduit through which cooling water flows or a composite of the radiating plate and the cooling conduit. The switching element 24 and the switching element pairs 60a to 60c may be semiconductor elements such as IGBTs and transistors in addition to the MOS-FETs. The semiconductor element is excellent in controllability, durability, and ease of mounting, and is suitable as a switching means in the motor drive circuit 10.

  Next, the operation of the motor drive circuit 10 configured as described above will be described.

  As shown in FIG. 3, during normal operation of the vehicle, the contactor 22 is kept on by the control circuit 50, and the switching element 24 is kept on by the overvoltage detection circuit 25. As a result, a voltage of 36 V is supplied from the battery 12 to the power drive unit 20, and the motor 14 can be driven by being converted from direct current to three-phase alternating current by the inverter circuit 58. 3, 4, and 5, the main lines for explanation of the power supply lines are indicated by bold lines, the current flowing directions are also shown, and the main lines where no current flows are indicated by broken lines.

  On the other hand, a voltage is stepped down from the battery 12 by the DC / DC converter 18 and supplied to the auxiliary machine 16. Since each ground line of the auxiliary machine 16 is connected to the ground line 20n of the power drive unit 20 via the ground line 18n of the DC / DC converter 18 and the connection line N2, the current of the auxiliary machine 16 is finally switched to the switching element. 24 and the negative power line N1 and flows into the negative terminal 12n of the battery 12. Therefore, the auxiliary machine 16 is supplied with 12V electric power and performs each function.

  Next, as shown in FIG. 4, when the motor 14 acts as a generator during braking or deceleration, the three switching element pairs 60a, 60b and 60c are appropriately turned on / off by the control circuit 50 and the pre-drive circuit 56. The three-phase power supplied from the motor 14 is converted to direct current and flows into the plus terminal 12p via the plus line 20p, the contactor 22 and the plus power line P2, and the battery 12 can be charged. At this time, current flows out from the negative terminal 12n and flows into the motor 14 via the negative power line N1, the switching element 24, and the ground line 20n.

  On the other hand, since the ground line of the auxiliary machine 16 is connected to the ground line 20n via the negative power line N2, as in the case shown in FIG. 3, it flows into the negative terminal 12n via the switching element 24 and the negative power line N1. . Therefore, a current corresponding to the difference between the forward current flowing from the auxiliary machine 16 and the reverse current flowing toward the motor 14 flows through the negative power line N1.

  As shown in FIG. 5, the battery 12 has a limit of charging, and if it is charged excessively, it becomes an overvoltage. Therefore, detection is performed by the overvoltage detection circuit 25, the switching element 24 is turned off, and then the contactor 22 is turned off. To do. Since the current does not flow through the contactor 22 by turning off the switching element 24 before turning off the contactor 22, no arc is generated even when the contactor 22 is turned off.

  In this case, the inverter circuit 58 is stopped, but the DC / DC converter 18 and the auxiliary machine 16 are effective. That is, the electric power supplied from the battery 12 is stepped down by the DC / DC converter 18 and distributed to each auxiliary device 16, and the feedback current of each auxiliary device 16 is supplied from the ground line 18n to the power drive unit 20 via the connection line N2. It flows to the ground line 20n. Here, although the switching element 24 is off, since the diode 76 is provided in parallel, the feedback current of the auxiliary machine 16 flows into the negative terminal 12 n of the battery 12 through the diode 76.

  In this way, even when the battery 12 becomes overvoltage, the switching element 24 is turned off and the inverter circuit 58 is stopped, the auxiliary machine 16 can continue to operate. At this time, the control circuit 50 and the pre-drive circuit 56 of the power drive unit 20 are also effective because power is supplied from the 12V system via the step-down converter 52 and the step-up converter 54.

  When the motor drive circuit 10 is started, the contactor 22 is first turned on, and the switching element 24 is turned on after a minute time. When the motor drive circuit 10 is finished, the switching element 24 is first turned off, and the contactor 22 is turned off after a minute time. Turn off. That is, when the contactor 22 is turned on and off, the switching element 24 is turned off so that no voltage is applied to the contactor 22, thereby preventing an arc from being generated in the contactor 22. Of course, it is sufficient if the contactor 22 is large and capable of interrupting a large current, but it is desirable that the contactor 22 be small from the viewpoint of cost and space utilization. Therefore, the contactor 22 can be reduced in size by using the switching element 24 together as described above.

  The switching element 24 and the contactor 22 are turned off not only when the battery 12 becomes overvoltage, but also when the overvoltage occurs in the inverter circuit 58, the driver overvoltage detection circuit 61 detects the voltage and the control circuit 50, the switching element 24 may be turned off through the overvoltage detection circuit 25, and the contactor 22 may be turned off.

  As described above, according to the motor drive circuit 10 of the present embodiment, the inverter circuit 58 is connected to the battery by providing the switching element 24 on the negative power line N1 that connects the connection line N2 and the negative terminal 12n of the battery 12. 12 can be reliably cut off, and arc generation can be suppressed in the contactor 22 to be cut off.

  In addition, the switching element 24 is provided with a diode 76 in parallel, and the power supply from the battery 12 to the auxiliary machine 16 can be continued even after the inverter circuit 58 is disconnected by the switching element 24.

  The switching element 24 is switching-controlled by the overvoltage detection circuit 25 and the driver overvoltage detection circuit 61, and can prevent the battery 12 and the inverter circuit 58 from generating an overvoltage.

  Of course, such a motor drive circuit 10 can also be applied to a hybrid vehicle or the like. When the motor drive circuit 10 is applied to a hybrid vehicle, the motor 14 functions as an independent travel drive source, and also performs operations such as engine assist and engine start. When the motor drive circuit 10 is applied to a motorcycle hybrid vehicle, the motor 14 may be attached to the left of the crankshaft. In the case of a hybrid vehicle, a kick starter may be used in combination.

  A control procedure at the time of starting the system when the motor drive circuit 10 is applied to a hybrid vehicle will be described with reference to FIG.

  In step S1, the system is started by turning on the switch 32.

  In step S2, the state of the battery 12 is confirmed, and it is confirmed whether the battery 12 is overdischarged. When it is overdischarge, it moves to step S15, and when that is not right, it moves to step S3.

  In step S3, the relay 34 in the DC / DC converter 18 is turned on.

  In step S4, the step-down converter 36 starts output.

  In step S5, the ECU 28, the power drive unit 20 and the like are activated.

  In step S6, a predetermined system check is performed.

  In step S7, when a failure is detected as a result of the system check, a predetermined warning is displayed in step S8, the activation process is interrupted, and if there is no failure, the process proceeds to step S9. The warning display is displayed on the meter 26, for example.

  In step S9, the contactor 22 and the switching element 24 are turned on.

  In step S10, a predetermined starter switch is confirmed. If the starter switch is turned on, the process proceeds to step S12. If the starter switch is turned off, the process proceeds to step S11.

  In step S11, it is confirmed whether the kick starter has been started. When the start by the kick starter is performed, the process proceeds to step S13, and otherwise, the process returns to step S10.

  In step S12, driving of the motor 14 is started.

  In step S13, engine ignition control is started.

  Thereafter, the process proceeds to predetermined traveling control in step S14.

  On the other hand, in step S15, it is confirmed whether the start by the kick starter has been performed. When the start by the kick starter has been performed, the process proceeds to step S16, and in other cases, the process waits.

  In step S16, boost converter 38 starts output.

  In step S17, the ECU 28, the power drive unit 20 and the like are activated.

  In step S18, a predetermined system check is performed.

  In step S19, when a failure is detected as a result of the system check, a predetermined warning display is performed in step S20, the activation process is interrupted, and if there is no failure, the process proceeds to step S21.

  In step S21, engine ignition control is started.

  In step S22, the contactor 22 and the switching element 24 are turned on. Thereafter, the process proceeds to step S14.

  The motor drive circuit according to the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

It is a circuit diagram of a motor drive circuit according to the present embodiment. It is a schematic perspective view of an inverter circuit. It is a circuit diagram which shows the flow of the electric current at the time of normal driving | operation with a motor drive circuit. It is a circuit diagram which shows the flow of the electric current at the time of regeneration in a motor drive circuit. It is a circuit diagram which shows the flow of the electric current at the time of isolation | separation of an inverter circuit in a motor drive circuit. It is a flowchart which shows the control procedure at the time of system starting at the time of applying a motor drive circuit to a hybrid vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Motor drive circuit 12 ... Battery 12n ... Minus terminal (2nd pole) 12p ... Plus terminal (1st pole)
DESCRIPTION OF SYMBOLS 14 ... Motor 16 ... Auxiliary machine 18 ... Converter 18n, 20n ... Ground line 18p, 20p ... Positive line 20 ... Power drive unit 22 ... Contactor 24 ... Switching element 25 ... Overvoltage detection circuit 26 ... Meter 28 ... ECU30 ... General electrical equipment 36 , 52 ... Buck converter 38, 54 ... Boost converter 50 ... Control circuit 56 ... Pre-drive circuit 58 ... Inverter circuit 61 ... Driver overvoltage detection circuit 76 ... Diode 78 ... Heat sink P1, P2 ... Positive power line (first power line)
N1... Negative power line N1 (second power supply line)
N2 ... Connection line

Claims (5)

A motor drive circuit for supplying power from a battery having a first pole and a second pole to a motor and an auxiliary machine having a voltage lower than a voltage for driving the motor,
A DC / DC converter that steps down the voltage supplied from the battery and supplies the voltage to the auxiliary machine;
A driver for controlling power supplied from the battery to drive the motor, and for regenerating power generated by rotation of the motor to the battery;
A contactor comprising a mechanical contact provided on a first power supply line connecting the first pole of the battery and the first pole line of the driver;
A connection line connecting the second pole line of the DC / DC converter and the second pole line of the driver;
Switching means provided in a second power supply line connecting the connection line and the second electrode of the battery;
A diode provided in parallel to the switching means and in a direction allowing a current in the discharge direction of the battery;
A motor drive circuit comprising: The motor drive circuit according to claim 1,
Overvoltage detection means for detecting overvoltage of the battery and the driver;
The motor drive circuit, wherein the switching means is switching-controlled by the overvoltage detection means. In the motor drive circuit according to claim 1 or 2,
The motor driving circuit, wherein the switching means is a semiconductor element. In the motor drive circuit according to claim 2 or 3,
The motor drive circuit, wherein the semiconductor element is mounted on a substrate of the driver. In the motor drive circuit according to any one of claims 3 to 4,
The motor drive circuit according to claim 1, wherein the semiconductor element is attached to a heat radiation means common to a semiconductor element of an inverter circuit that supplies current to the motor.

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