JP2016052141A - Motor drive device and power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device which is easily handled and capable of controlling a coil current in simple configuration, and a power module.SOLUTION: The motor drive device controls the coil current that flows to a coil forming a motor, by switching between a power supply mode in which the coil current is increased and an attenuation mode in which the coil current is attenuated. The attenuation mode is formed by combining a first attenuation mode and a second attenuation mode in a predetermined ratio. In the first attenuation mode the coil current is attenuated at a first attenuation rate and in the second attenuation mode, the coil current is attenuated at a second attenuation rate that is smaller than the first attenuation rate. When a power supply voltage value supplied to the coil is equal to or greater than a predetermined value, the combination ratio of the first attenuation mode is made smaller than the time in which the power supply voltage value supplied to the coil is smaller than the predetermined value.SELECTED DRAWING: Figure 1

Description

The present invention relates to a drive device and a power module for driving a motor such as a stepping motor.

Stepping motors are used as a driving force for office automation equipment such as facsimile machines, copiers, and printers, as well as FA machines including machine tools, robots, and semiconductor manufacturing apparatuses. The stepping motor has a stator (stator) and a rotor (rotor), and coils are wound around a plurality of poles of the stator. The stepping motor drive device can move the rotor to an arbitrary position by controlling the current flowing in the coil.

An attenuation rate control circuit for setting a plurality of mixed attenuation factors by combining a first attenuation factor and a second attenuation factor smaller than the first attenuation factor in order to suppress a ripple current flowing in the motor coil; A motor drive device is known that includes a control logic circuit that generates an excitation pattern that attenuates a drive current with an attenuation rate, and a drive current output circuit that outputs a drive current to a stepping motor according to the excitation pattern (Patent Document 1). .

JP 2009-213344 A

According to Patent Document 1, a motor drive device having a function that allows a user of the motor drive device to set the attenuation rate of the drive current in detail according to the specification, application, etc. of the stepping motor is provided. However, in order for the user to set the attenuation rate, a plurality of preliminary experiments must be performed while changing conditions such as the motor speed. In addition, since an external terminal for setting the attenuation factor is provided in the drive device, the structure of the drive device becomes complicated.

In view of the above problems, the present invention provides a motor driving device and a power module capable of controlling the coil current with an easy and simple configuration.

According to one aspect of the present invention, there is provided a motor drive device that controls the coil current by switching between a power supply mode for increasing a coil current flowing in a coil constituting the motor and an attenuation mode for attenuating the coil current. The attenuation mode includes a first attenuation mode for attenuating the coil current with a first attenuation factor and a second attenuation for attenuating the coil current with a second attenuation factor smaller than the first attenuation factor. Mode is combined at a predetermined ratio, and when the power supply voltage value supplied to the coil is greater than or equal to a predetermined value, the first power supply voltage value supplied to the coil is less than the first value. The combination ratio of the attenuation modes is reduced.

The attenuation rate in the present invention means a rate (di / dt) at which the coil current decreases with respect to time.

ADVANTAGE OF THE INVENTION According to this invention, the motor drive device and power module which can control a coil electric current with an easy and simple structure can be provided.

It is a circuit diagram which shows the structure of the motor drive device and power module which concern on embodiment of this invention. It is a wave form diagram showing operation of a motor drive concerning an embodiment of the present invention. It is operation | movement explanatory drawing of the motor drive device which concerns on embodiment of this invention. It is a figure which shows operation | movement of the motor drive device which concerns on embodiment of this invention.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic. Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention have the following structure and arrangement of components. It is not something specific. The embodiment of the present invention can be variously modified within the scope of the claims.

FIG. 1 is a circuit diagram showing a configuration of a motor drive device and a power module according to an embodiment of the present invention. The power module 100 according to this embodiment drives a full bridge circuit including a first power transistor M1, a second power transistor M2, a third power transistor M3, and a fourth power transistor M4, and a full bridge circuit. And a first to third resistors R1, R2, and R3.

Each of the first to fourth power transistors M1, M2, M3, and M4 has a drain terminal (high-voltage side terminal), a source terminal (low-voltage side terminal), and a gate terminal (control terminal). It consists of a power MOSFET having parasitic diodes D1, D2, D3, and D4 that can flow current toward the drain terminal.

In the full bridge circuit, the drain terminals of the second and third power transistors M2 and M3 are connected to the motor power supply. The source terminal of the second power transistor M2 is connected to the drain terminal of the first power transistor M1, and the source terminal of the third power transistor M3 is connected to the drain terminal of the fourth power transistor M4. The source terminals of the first and fourth power transistors M1 and M4 are grounded via the first detection resistor Rs. A connection point between the first and second power transistors M1 and M2 is a first output terminal of the power module 100, and is connected to one end of a coil L1 that is a load. A connection point between the third and fourth power transistors M3 and M4 is a second output terminal of the power module 100 and is connected to the other end of the coil L1. That is, the first to fourth power transistors M1, M2, M3, and M4 are connected in an H shape to form a full bridge circuit.

The motor drive device 10 controls the coil current by switching between a power supply mode for increasing the coil current flowing in the coil L1 constituting the motor and an attenuation mode for attenuating the coil current. In the attenuation mode, a high-speed attenuation mode in which the coil current is attenuated by a first attenuation factor and a low-speed attenuation mode in which the coil current is attenuated by a second attenuation factor smaller than the first attenuation factor are combined at a predetermined ratio. Being done. When the voltage value of the motor power supply is equal to or higher than the predetermined value, the motor driving device 10 makes the combination ratio of the high-speed decay mode smaller than when the voltage value of the motor power supply is less than the predetermined value.

The motor driving device 10 is connected to at least a motor power source, gate terminals of the first to fourth power transistors M1, M2, M3, and M4, and a detection resistor Rs that detects a coil current IL1 flowing through the coil L1. Is done. The motor driving device 10 also includes a control circuit 11 for controlling on / off of each power transistor, and a first and a first that compare a voltage signal based on the voltage value of the motor power supply with the first and second reference values Vref1 and Vref2. 2 comparators CMP1 and CMP2. Note that the second reference value Vref2 is a reference voltage obtained by adding a positive voltage offset Voffset to the first reference value Vref1. In addition, the motor driving device 10 includes a third comparator CMP3 connected to the detection resistor Rs, and each power transistor can perform constant current control with a target current value defined by the third reference value Vref3 as a peak. Turn on and off.

The control circuit 11 is connected to the gate terminals of the first to fourth power transistors M1, M2, M3, and M4 and the output terminals of the first to third comparators CMP1, CMP2, and CMP3. The first input terminal (positive input terminal) of the first comparator CMP1 is connected to the connection point between the first resistor R1 and the second resistor R2, and the second input terminal (negative input terminal) is the first input terminal. 1 reference value Vref1. The first input terminal (positive input terminal) of the second comparator CMP2 is connected to the connection point between the second resistor R2 and the third resistor R3, and the second input terminal (negative input terminal) is the first input terminal. 2 is connected to the reference value Vref2. The first input terminal (positive input terminal) of the third comparator CMP3 is connected to the detection resistor Rs, and the second input terminal (negative input terminal) is connected to the third reference value Vref3. The first to third resistors R1, R2, R3 are connected in series between the motor power supply and the ground point, and divide the voltage value V1 of the motor power supply and output it to the first and second comparators CMP1, CMP2. . Note that the second resistor R2 can be omitted, and the first input terminal of the second comparator CMP2 may be connected to a connection point between the first resistor R1 and the third resistor R3.

Since the motor power supply voltage is generally used in the 12V system, 24V system, and 48V system, the first and second reference values Vref1 and Vref2 are preferably set avoiding these voltage values. The first and second comparators CMP1 and CMP2 are preferably provided with hysteresis in order to prevent malfunction due to power supply voltage fluctuations.

FIG. 2 is a waveform diagram showing the operation of the motor drive device according to the embodiment of the present invention. The solid line in the figure indicates the coil current IL1 flowing through the coil L1, and the broken line indicates the target current value I1 of the coil current IL1 and the current value I2 at the end of the period T3. FIG. 3 is an operation explanatory diagram of the motor drive device according to the embodiment of the present invention, and arrows in the figure indicate a path and direction of current flow. The motor drive device 10 according to the present embodiment includes a current supply mode for increasing the coil current IL1, a first attenuation mode for attenuating the coil current IL1 with a first attenuation factor, and a first attenuation factor for the coil current IL1. The motor is driven in accordance with a second attenuation mode in which attenuation is performed with a smaller second attenuation rate. In addition, when the motor power supply voltage value V1 is greater than or equal to a predetermined value, the motor drive device 10 drives the first attenuation mode during the attenuation mode drive period more than when the motor power supply voltage value V1 is less than the predetermined value. Reduce the proportion of the period.

First, in the period T1, as shown in FIG. 3A, the motor drive device 10 drives the full bridge circuit according to the current supply mode for at least a predetermined minimum time. The second and fourth power transistors M2 and M4 are turned on, the first and third power transistors M1 and M3 are turned off, and the current flows through a path made up of M2, M4 and L1, and the coil current IL1 passes over time. It increases with. The coil current IL1 is converted into a voltage signal VRs indicating the magnitude of the coil current by flowing through the detection resistor Rs, and is output to the first output terminal of the third comparator CMP3. The motor driving according to the current supply mode is continued until a predetermined minimum time has elapsed and the coil current IL1 becomes equal to or higher than the target current value I1.

After the end of the motor driving according to the current supply mode, in period T2, as shown in FIG. 3B, the motor driving device 10 drives the full bridge circuit according to the first attenuation mode (high-speed attenuation mode). At least the second and fourth power transistors M2 and M4 are turned off, and the current flows through a path including M1, M3, and L1, and the coil current IL1 tends to decrease sharply. When the first and third power transistors M1 and M3 are turned off, the coil current IL1 flows through the parasitic diodes of the first and third power transistors M1 and M3, and the first and third power transistors M1 and M3 are When turned on, the coil current IL1 flows through the channels of the first and third power transistors M1 and M3. In the first attenuation mode, the voltage across the coil L1 is clamped by the voltage of the motor power supply, so that the coil current IL1 decreases with a relatively large first attenuation rate over time.

After the motor driving according to the first attenuation mode is completed, in the period T3, as shown in FIG. 3C, the motor driving device 10 drives the full bridge circuit according to the second attenuation mode (slow attenuation mode). The fourth power transistor M4 is turned on, at least the second and third power transistors M2 and M3 are turned off, the current flows through the path formed by M1, M4, and L1, and the coil current IL1 tends to decrease gradually. When the first power transistor M1 is turned off, the coil current IL1 flows through the parasitic diode of the first power transistor M1, and when the first power transistor M1 is turned on, the coil current IL1 is changed to the first power transistor M1. Flowing through the channel. In the second attenuation mode, the voltage across the coil L1 is clamped by the forward voltage of the parasitic diode of the first power transistor M1, so that the coil current IL1 is smaller than the first attenuation factor over time. Decrease with a decay rate of.

FIG. 4 is a diagram illustrating the operation of the motor drive device according to the embodiment of the present invention. The ratio of the period T2 in the figure is the time ratio of the period T2 in the period obtained by adding the periods T1 and T2, and corresponds to the combination ratio in the present invention. When the voltage V1 of the motor power supply is low and the outputs of the first and second comparators CMP1 and CMP2 are both L, the ratio of the period T2 in the driving period of the attenuation mode including the period T2 and the period T3 is 30%. is there. When the voltage value V1 of the motor power supply is high and the output of the first comparator CMP1 is H and the output of the second comparator CMP2 is L, the ratio of the period T2 decreases to 20%. When the voltage value V1 of the motor power supply is higher and the outputs of the first and second comparators CMP1 and CMP2 are both H, the ratio of the period T2 is reduced to 10%. Therefore, the motor drive device 10 according to the present embodiment shortens the drive time according to the first attenuation mode when the voltage value of the motor power supply increases.

The driving device 10 according to the present embodiment controls the current flowing through the coil L1 to a predetermined value by driving the full bridge circuit by repeatedly switching the modes as described above, that is, driving the motor at a constant current. Can do. At this time, a ripple current (I1-I2) is generated in which the target current value I1 defined by the third reference value Vref3 is the peak and the current value at the end of the period T3 is the bottom. When the ratio of the period T2 is fixed, the ripple current increases when the motor power supply voltage is high. The drive device 10 according to the present embodiment can obtain a stable motor performance that is hardly influenced by the motor power supply voltage by reducing the ratio of the drive period of the first attenuation mode when the motor power supply voltage is high. Further, the necessity of conducting a preliminary experiment for setting the attenuation rate is reduced, and it is not necessary to provide an external terminal for setting the attenuation rate in the motor drive device. Therefore, according to the present embodiment, it is possible to provide a motor driving device and a power module that can control the coil current with an easy-to-handle and simple configuration.

The motor driving device 10 may drive the full bridge circuit in accordance with the second attenuation mode as shown in FIG. At this time, the second power transistor M2 is turned on, at least the first and fourth power transistors M1 and M4 are turned off, and a current flows through a path formed by M2, M3, and L1. When the third power transistor M3 is turned off, the current flows through the parasitic diode of the third power transistor M3, and when the third power transistor M3 is turned on, the current flows through the channel of the third power transistor M3. Flowing. Since the voltage between both ends of the coil L1 is clamped by the forward voltage of the parasitic diode of the third power transistor M3, the coil current decreases with an attenuation rate substantially equal to the second attenuation rate over time.

As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description. For example, the motor drive device and the power module may be configured to drive not only a stepping motor but also a three-phase brushless motor. The power transistor may be a discrete element made of a P-channel MOSFET, IGBT, or bipolar transistor, or may be a transistor element formed on the same chip as the driving device. The first to fourth modes are modes in which a current in the same direction flows through the coil L1, but the driving device may drive the full bridge circuit according to another mode in which a current in the opposite direction flows.

DESCRIPTION OF SYMBOLS 10 Motor drive device 11 Control circuit CMP1 1st comparator CMP2 2nd comparator CMP3 3rd comparator L1 Coil M1 1st power transistor M2 2nd power transistor M3 3rd power transistor M4 4th power transistor Rs detection Resistance T1 Current supply mode driving period T2 First attenuation mode driving period T3 Second attenuation mode driving period Vref1 First reference value Vref2 Second reference value Vref3 Third reference value

Claims (5)

A motor driving device for controlling the coil current by switching between a power supply mode for increasing a coil current flowing in a coil constituting the motor and an attenuation mode for attenuating the coil current;
The attenuation mode includes a first attenuation mode for attenuating the coil current with a first attenuation factor, and a second attenuation mode for attenuating the coil current with a second attenuation factor smaller than the first attenuation factor. And are combined at a predetermined ratio,
When the power supply voltage value supplied to the coil is greater than or equal to a predetermined value, the combination ratio of the first attenuation mode is made smaller than when the power supply voltage value supplied to the coil is less than a predetermined value. A motor drive device. 2. The motor driving device according to claim 1, wherein the motor driving device drives the motor according to the first damping mode and the second damping mode after driving the motor according to a current supply mode for increasing the coil current. The motor drive device described in 1. The motor driving apparatus according to claim 1, wherein the motor driving apparatus includes a voltage detection unit that detects the power supply voltage value. The said motor drive device is provided with the control part which changes the said combination ratio according to the output of the said voltage detection part, The motor drive device described in Claim 3 characterized by the above-mentioned. A power module comprising: a plurality of power transistors connected to the coil; and the motor driving device according to any one of claims 1 to 4.

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