MOTOR DRIVER

A motor driver includes an inverter, a multiphase pre-driver circuit, a controller and motor relays. The inverter includes pairs of an upper-arm switching element and a lower-arm switching element being connected in series between a ground line and a power supply line, and supplies power to a multiphase motor by converting direct current power of a battery. The multiphase pre-driver circuit drives the upper-arm and lower-arm switching elements. The controller commands the multiphase pre-driver circuit to drive the switching elements, and controls electrical conduction from the inverter to the multiphase motor. The motor relays interrupt a current flowing from the multiphase motor to the inverter during an off state. The multiphase pre-driver circuit includes a charge pump. The motor relays are turned on by an output voltage of the charge pump during an operation of the charge pump in a situation apart from that the controller provides an instruction.

TECHNICAL FIELD

The present disclosure relates to a motor driver.

BACKGROUND

A motor driver may convert a direct-current (DC) power of a battery through an inverter and supply the converted power to a multiphase motor. For example, an electric motor driver may be provided with multiple motor relays, each of which may interrupt a current path connected to a motor winding and a connection node between arms of a corresponding one of phases of the inverter. The motor relays may be driven by a common driver circuit with a reverse connection protective relay.

SUMMARY

The present disclosure describes a motor driver including an inverter, a multiphase pre-driver circuit, a controller, and motor relays.

DETAILED DESCRIPTION

A driver for an auxiliary motor adapted to a vehicle may be designed with a 12-volt battery. However, the auxiliary battery voltage for an electric vehicle may be increased to 24 volts or 48 volts, which exceeds the voltage tolerance of a conventional 12-volt drive circuit. Therefore, in addition to an inverter capable of operating at a high voltage, a driver circuit may be required to drive motor relays, which may pose challenges in terms of downsizing and high integration of a motor drive system.

According to an aspect of the present disclosure, a motor driver includes an inverter, a multiphase pre-driver circuit, a controller, and motor relays. The inverter includes pairs of an upper-arm switching element and a lower-arm switching element. Each of the pairs is provided for a corresponding one of phases and connected in series between a power supply line and a ground line. The power supply line is connected to a battery. The inverter converts DC power of a battery and then supplies the converted power to the multiphase motor.

The multiphase pre-driver circuit is operated by a voltage supplied from the battery to drive the switching elements included in the inverter. The controller provides a drive signal to the multiphase pre-driver to command the multiphase pre-driver to drive the switching elements, and controls the electrical conduction of the multiphase motor from the inverter.

The motor relays are semiconductor switching elements. Each motor relay is connected between an inter-arm connection node and a corresponding one of phase windings of the multiphase motor. The inter-arm node is a connection node located between the upper-arm switching element and the lower-arm switching element provided in each of the pairs provided for the respective phases of the motor. When the motor relay is in an off state, a current flowing from the multiphase motor to the inverter is interrupted.

The multiphase pre-driver circuit includes a charge pump that boosts a voltage of the battery. An output end of the charge pump is connected to the gate of the motor relay provided for each phase of the motor. The motor relay provided for each phase is turned on by an output voltage of the charge pump during an operation of the charge pump in a situation apart from that the controller provides an instruction.

As a result, a driver circuit targeted to the motor relay is not required. Thus, it is possible to drive the motor relay with a simple configuration. For example, in a case where the battery voltage is boosted from 12 volts to 24 volts or 48 volts, it is also possible to drive the motor relay even though a voltage of the charge pump is raised to a high voltage for driving the inverter.

The following describes motor drivers according to multiple embodiments with reference to the drawings. In the multiple embodiments, substantially the same components are denoted by the same reference numerals, and a description of the same components will be omitted. The following first to fourth embodiments are collectively referred to as “present embodiment”. The multiphase motor described in the present embodiment corresponds to a three-phase motor, and the multiphase pre-driver circuit corresponds to a three-phase pre-driver circuit. The motor driver according to the present embodiment converts direct-current (DC) power of a battery and then supplies the converted power to a steering assistive motor in an electric power steering apparatus. The steering assistive motor includes a three-phase brushless motor.

The voltage of the auxiliary battery installed in vehicles has traditionally been 12 volts, but in this embodiment, it is mainly assumed to be 24 volts or 48 volts, which are expected to be adopted in future electric vehicles. “24V/48V” in the drawings and the following description means “24 volts or 48 volts.” However, even when using a 12-volt battery, the configuration according to the present embodiment is basically the same. The present embodiment may be applied not only to electric vehicles but also to engine vehicles.

Specifically, the ECU of the electric power steering apparatus functions as a motor driver. The ECU includes, for example, a microcomputer, a customized integrated circuit, and the like, and has a CPU (not shown), a ROM, a RAM, an I/O, and a bus line connecting these components. The ECU performs required control by executing software processing or hardware processing. The software processing may be implemented by causing the CPU to execute a program. The program may be stored beforehand in a memory device such as a ROM, that is, in a readable non-transitory tangible storage medium. The hardware processing may be implemented by a special purpose electronic circuit.

First Embodiment

FIG.1illustrates the configuration of a motor driver101according to the first embodiment. The motor driver101includes, for example, an inverter60, a three-phase pre-driver circuit40, a microcontroller30, and motor relays71,72,73. The microcontroller30corresponds to a controller. AlthoughFIG.1illustrates the configuration of the motor driver101with a single system, a redundant configuration of two or more systems may be used. For example, in a motor driver with a dual system, the power is supplied from two inverters to a double-winding motor having two sets of windings.

The inverter60is provided between a power supply line Lp and a ground line Lg. The power supply line Lp is connected to a positive electrode of a battery15. The ground line Lg is connected to a negative electrode of the battery15. The inverter60includes upper and lower arm switching elements61to66, which are connected in series between the power supply line Lp and the ground line Lg. The upper and lower arm switching elements61to66are provided for respective three phases. The upper arm switching elements61,62, and63of the U phase, V phase, and W phase and the lower arm switching elements64,65, and66of the U phase, V phase, and W phase are connected in a bridge configuration. In the present embodiment, MOSFETs are used as the switching elements61to66of the inverters60. In the present embodiment, the MOSFET is an n-channel type.

Connection nodes between the upper-arm switching elements and the lower-arm switching elements of phases are defined as inter-arm connection nodes Nu, Nv, Nw, respectively. The inter-arm connection nodes Nu, Nv, and Nw are connected to three-phase windings81,82, and83of the motor80, respectively. The inverter60converts DC power of the battery15and then supplies the converted power to the three-phase windings81,82,83. For example, when the motor80is in a Y-connection, the three-phase windings81,82,83are connected at a neutral node Nm. However, the three-phase windings81,82, and83may also be in delta connection.

An inverter capacitor56is connected to the inverter60in parallel between the power supply line Lp and the ground line Lg, and is charged by the voltage applied to the inverter60. During normal operation of a motor driver101, the inverter capacitor56functions as a smoothing capacitor.

A filter capacitor16and a choke coil (inductor)17are provided on the battery15side of the inverter60. The filter capacitor16and the choke coil17are included in a noise countermeasure LC filter circuit. The filter capacitor16and the inverter capacitor56are, for example, polar aluminum electrolytic capacitors. The choke coil17is provided on the power supply line Lp.

InFIG.1, the reverse connection protective relay52is connected to the power supply line Lp between the choke coil17and the inverter60. The reverse connection protective relay52is connected to a freewheeling diode in parallel that allows current flow from the battery side to the power converter side, and at the same time, interrupts the current flow from the inverter60side to the battery15side when it is turned off. For example, in the reverse connection protective relay52having a MOSFET, a parasitic diode of the MOSFET functions as a freewheeling diode. However, the reverse connection protective relay52may be provided on the ground line Lg.

Additionally, a power supply relay may be provided at the position X shown by a two-dot chain line, that is, on the battery15side of the reverse connection protective relay52. In this situation, the power supply relay is connected to a freewheeling diode in parallel that allows current flow from the inverter60side to the battery15side, and at the same time, interrupts the current flow from the battery15side to the inverter60side when it is turned off.

The motor relays71,72,73are provided in a motor current path between the inter-arm connection nodes Nu, Nv, Nw of corresponding phases and the phase windings81,82,83, respectively. The motor relays71,72,73are MOSFETs being semiconductor switching elements. The parasitic diodes conduct current from the inter-arm connection nodes Nu, Nv, Nw to the three-phase windings81,82,83. The motor relays71,72,73interrupt the current from the motor80side to the inverter60side when the motor relays71,7273are in the off state.

Although not shown, a current sensor for detecting phase current is provided at the inverter60or each phase motor current path. During the normal operation of the motor driver101, the microcomputer (controller)30calculates a drive signal for the inverter60by current feedback control based on the phase current detection value and the motor rotation angle so that the motor80outputs the command torque. The integrated IC may share a part of the function of the controller executed by the microcontroller30. In the case of a dual-system configuration, control information may be mutually communicated between the respective microcomputers of individual systems.

In the following,FIG.2will be referred to in conjunction withFIG.1.FIG.2particularly illustrates the configuration of the three-phase pre-driver circuit40and the drive configuration of the motor relays71,72, and73. The three-phase pre-driver circuit40is operated by the voltage supplied from the battery15, and drives the switching elements61to66of the inverter60. The microcontroller30commands a drive signal to the three-phase pre-driver circuit to control electrical conduction from the inverter60to the three-phase motor80.

The three-phase pre-driver circuit40is supplied by a power supply voltage of 24V/48V from the power supply line Lp located after the choke coil17. InFIG.2, the power supply voltage of 24V/48V is indicated as “PIG”. Further, a power supply voltage of 12V is supplied from the power supply line Lp via a step-down regulator18. If the battery voltage is 12V, the step-down regulator18is not required.

The three-phase pre-driver circuit40includes a charge pump43that boosts the battery voltage. The output voltage of the charge pump43is referred to as a charge pump voltage Vcp. Furthermore, the voltage of 12V provided via the step-down regulator18is referred to as a non-boosted voltage Vnb. The charge pump voltage Vcp is output to the gates of upper arm (high side) switching elements61to63. The non-boosted voltage Vnb is output to the gates of the lower arm (low side) switching elements64to66. In the drawing, “HS” indicates the high side, and “LS” indicates the low side.

While the power supply voltage is being supplied to the three-phase pre-driver circuit40, the charge pump43superimposes the voltage charged in the capacitor Ccp and basically continues to output a constant voltage at all times. When the supply of power supply voltage to the three-phase pre-driver circuit40is interrupt, or when the charge pump voltage Vcp exceeds the upper limit threshold or falls below the lower limit threshold, the logic circuit in the three-phase pre-driver circuit40stops the operation of the charge pump43.

In the present embodiment, the output end of the charge pump43is connected to the gates of the motor relays71,72,73provided for respective phases. For example, in the configuration according to the first embodiment, charge pump voltage paths461,462,463provided for respective phases are branched from a common three-phase charge pump voltage path46connected to the output end of the charge pump43, and are connected to the gates of the motor relays71,72,73provided for the respective phases.

Accordingly, the motor relays71,72,73provided for the respective phases are turned on by the output voltage Vcp of the charge pump43during the operation of the charge pump43, except when there is a command (in other words, an interruption signal described hereinafter) from the microcontroller30. In other words, without adopting a driver circuit dedicated to the motor relays, it is possible to turn on the motor relays71,72,73by adopting the charge pump voltage Vcp required for driving the upper arm switching elements61to63of the inverter60.

In order to intentionally turn off the motor relays71,72,73during the operation of the charge pump43, in the first embodiment, a gate interruption switch47being a MOSFET is provided between the charge pump voltage path46and a ground. The gate interruption switch47and the charge pump voltage path46are common to the three phases. In the first embodiment, when the interruption signal common to the three phases is provided from the microcontroller30, the gate interruption switch47is turned on to ground the charge pump voltage path46. As a result, the gate voltage supplied from the output end of the charge pump43to the motor relays71,72,73is interrupted, and the motor relays71,72,73are simultaneously turned off.

In the normal operation of the three-phase motor80, the electrical conduction of the three-phase windings81,82,83starts at the same time, and also stops at the same time. When the back electromotive force generated by the external force is regenerated from the motor80to the battery15side via the inverter60, it is considered that the regenerative current flows through the three phases at the same timing. In such a case, it is effective to turn off the motor relays71,72, and73using a common three-phase interruption signal.

Furthermore, in the configuration example shown inFIG.1, the output end of the charge pump43is connected to the gate of the reverse-connection protective relay52via another charge pump voltage path45. Similarly, the reverse connection protective relay52can be turned on using the charge pump voltage Vcp without using a dedicated driver circuit. However, in the present embodiment, driving the reverse connection protective relay52is a supplementary matter. InFIG.2, the illustration of the reverse connection protective relay52is omitted.

The following describes advantageous effects in the first embodiment as compared with a motor driver109according to a comparative example with reference toFIG.6. The motor driver109according to the comparative example includes a relay driver circuit49that can commonly drive the motor relays71,72,73and the reverse connection protective relay52based on a drive signal provided from the microcontroller30.

In the comparative example, although the motor relays71,72,73and the reverse connection protective relay52are shared in a driver circuit to achieve miniaturization and high integration, a dedicated driver circuit for the relays is still required. Therefore, the above configuration related to the comparative example has a larger size and an increased cost.

In contrast, in the first embodiment, since the motor relays71,72, and73are driven by the output voltage Vcp of the charge pump43, a driver circuit dedicated to the motor relays is not required. Therefore, the motor relays71,72, and73can be driven with a simple configuration. For example, when the battery voltage is increased from 12 volts to 24 volts or 48 volts, the charge pump voltage Vcp for driving the inverter60is increased, and the motor relays71,72, and73can also be driven.

Second Embodiment

The following describes a second embodiment with reference toFIG.3.FIGS.3to5are referred to the second to fourth embodiments, respectively.FIGS.3to5illustrate drive configuration of the motor relays71,72,73with reference toFIG.2according to the first embodiment. In a motor driver102according to the second embodiment, gate interruption switches471,472,473are provided for the respective phases between the ground and the charge pump voltage paths461,462,463provided for the respective phases.

The gate interruption switches471,472,473are turned on when the interruption signal is provided from the microcontroller30. The gate interruption switches471,472,473turn off the motor relays71,72,73, which are provided for the respective phases, by grounding the charge pump voltage path461,462,463. Based on the interruption signal for each phase provided from the microcontroller30, the gate interruption switch471individually interrupts the gate voltage supplied to the U-phase motor relay71; the gate interruption switch472individually interrupts the gate voltage supplied to the V-phase motor relay72; and the gate interruption switch473individually interrupts the gate voltage supplied to the W-phase motor relay73.

Also in the second embodiment, the microcontroller30outputs the interruption signal for three phases at the same time, in a case where the electrical conduction of the three phases are normally stopped at the same time. On the other hand, for example, when the inverter switching element or the current sensor included in one of the three phases. In the second embodiment, it is possible to individually interrupt the motor relay included in the phase whose drive is to be stopped.

In the motor driver with a redundant dual-system configuration applied to an electric power steering apparatus, when a single phase included in a single system has a fault, it is possible to stop the entire abnormal system and switch to the normal drive system. Therefore, switching from three-phase drive to two-phase drive is mainly useful in the motor driver with a single system configuration.

Third Embodiment

The following describes a third embodiment with reference toFIG.4. In a motor driver103according to the third embodiment, the gate interruption switches471,472,473are provided in the middle of the charge pump voltage paths461,462,463that are provided for the respective phases, respectively. The gate interruption switches471,472,473individually interrupt the motor relays71,72,73provided for the respective phases by interrupting the charge pump voltage paths461,462,463based on the interruption signal for each phase from the microcontroller30. Also in the third embodiment, the same effects as those of the second embodiments can be obtained.

It is also possible to provide a common gate interruption switch47, using the same method as the third embodiment, in the middle of the three-phase common charge pump voltage path46inFIG.1according to the first embodiment.

Fourth Embodiment

The following describes a fourth embodiment with reference toFIG.5. The gate interruption switches of the motor relays71,72,73are not provided in a motor driver104according to the fourth embodiment. Instead, the microcontroller30outputs a signal to stop the operation of the charge pump43. In the circuit of the charge pump43, no residual voltage remains after the operation is stopped. By outputting a stop signal to the charge pump43, the microcontroller30stops the operation of the inverter60and simultaneously turns off the motor relays71,72, and73provided for the respective phases. Even with this configuration, the motor relays71,72, and73can be intentionally turned off.

Other Embodiments

The motor driver according to the present disclosure may not include the reverse connection protective relay. Additionally, it is only necessary to drive the motor relays71,72,73, which are provided for the respective phases, with the charge pump voltage Vcp, and there is no need to drive the reverse connection protective relay with the charge pump voltage Vcp.

The motor relays71,72,73and the gate interruption switches47,471,472,473are not limited to MOSFETs, but may be other semiconductor elements such as bipolar transistors.

The number of phases in the multiphase motor and the multiphase pre-driver circuit may not be limited to three, but may also be two or four or more.

The motor driver according to the present disclosure may be applied to various multiphase motor driver including in-vehicle devices other than electric power steering devices and devices other than devices to be mounted on vehicles.

The present disclosure should not be limited to the embodiment described above. Various other embodiments may be implemented without departing from the scope of the present disclosure.

The controller and the technique according to the present disclosure may be achieved by a dedicated computer provided by constituting a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the controller and the method described in the present disclosure may be realized by a dedicated computer configured as a processor with one or more dedicated hardware logic circuits. Alternatively, the controller and method described in the present disclosure may be realized by one or more dedicated computer, which is configured as a combination of a processor and a memory, which are programmed to perform one or more functions, and a processor which is configured with one or more hardware logic circuits. The computer program may be stored in a computer-readable non-transitory tangible recording medium as an instruction to be executed by a computer.

The present disclosure has been made in accordance with the embodiments. However, the present disclosure is not limited to such embodiments and configurations. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combination and formation, and other combination and formation including one, more than one or less than one element may be made in the present disclosure.