JP2013240214A - Dc motor driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch the direction and speed of rotation of a DC motor immediately, while reducing overshoot.SOLUTION: The DC motor driver is configured so as to release the counter electromotive force of a DC motor generated in a direction opposite from a driving current by a first switch disposed between a power supply configuring a drive circuit for CW rotation and the DC motor and a second switch disposed between the DC motor and the GND, a third switch disposed between the power supply configuring a drive circuit for CCW rotation and the DC motor and a fourth switch disposed between the DC motor and the GND, and control means for adjusting the direction and speed of rotation of the DC motor by intermittent switching of each switch.

Description

  The present invention relates to a DC motor driver.

Non-patent document 1 describes general DC motor rotation direction and speed control. For example, in the circuit shown in FIG. 4, the direction of current input to both terminals 101 and 102 of the DC motor 100 is controlled by selectively opening and closing four switches S100, S200, S300, and S400. 100 is rotated in the CW (clockwise) direction and the CCW (counterclockwise) direction. The switches S100, S200, S300, and S400 are opened and closed by a separately provided control device. When the switches S100 and S400 are closed (ON) and S300 and S200 are opened (OFF), the DC motor 100 is CW. If the switches S100 and S400 are opened (off) and S300 and S200 are closed (on), the DC motor 100 is rotated in the CCW direction.
In addition, the rotational speed of the DC motor 100 is controlled by controlling (PWM control) the open / close times of the four switches S100, S200, S300, and S400 with the pulse width controlled by the IC. The case where the DC motor 100 is rotated in the CW direction will be described as an example. For example, as shown in FIG. 5A, the open / close time of the switch S400 is controlled by the pulse width while the switch S100 is closed. In this case, as shown in FIG. 5B, the DC motor 100 rotates at a low speed (low speed operation) when the interval of periodically closing (turning on) the switch S400 is shortened as shown in FIG. 100 rotates at high speed (high speed operation).

Although the DC motor can control the rotation direction and rotation speed as described above, a counter electromotive force is generated when decelerating, stopping, or reversing the rotation direction. After sufficient electric power discharge time had passed, it was rotated at the specified direction and speed. Therefore, it is difficult to quickly change the direction of rotation and change the speed.
Further, there is a technique described in Patent Document 1 as a countermeasure against the occurrence of such back electromotive force. The technology relates to a back electromotive force detection unit that detects a voltage rising on the inverter input side due to a back electromotive force generated at the time of acceleration / deceleration of the motor, and an output of the back electromotive force detection unit is input to the back electromotive force removal unit by a switching unit. And a back electromotive force removing unit that consumes current as a current flows between power supply input terminals by ON / OFF control of the MOS-FET. The present invention also provides a motor back electromotive force removing device using a MOS-FET that effectively removes the back electromotive force of the motor to prevent the destruction of the switching elements constituting the inverter and protects the motor controller. Is.

JP-A-6-343291

Advanced DC motor technology by Naoshi Mijo Nikkan Kogyo Shimbun

  At the time of switching the rotation direction and rotation speed of the DC motor, a counter electromotive force is generated from the DC motor. Therefore, unless the discharge time of the counter electromotive force is sufficient, the next control cannot be handled. As a result, it has been difficult to employ a DC motor for applications in which the rotation direction and speed are frequently switched. Further, in the example described in Patent Document 1, the back electromotive force detection unit and the like must be provided, and the circuit and control are complicated.

The present invention has been invented in view of the above problems, and an object of the present invention is to provide a DC motor driver capable of switching the rotation direction and speed of the DC motor with agility and less overshoot.
Another object is to provide a DC motor driver whose structure and control are not complicated.

In order to solve the above problems, the invention according to claim 1 of the present application has the following configuration. That is,
A first switch arranged between a power source and a DC motor constituting a drive circuit for CW rotation, and a second switch arranged between the DC motor and GND;
A third switch disposed between the power source and the DC motor constituting a drive circuit for CCW rotation, and a fourth switch disposed between the DC motor and the GND;
Control means for adjusting the rotation direction and rotation speed of the DC motor by intermittently opening and closing each switch,
When changing the rotational direction of the DC motor or decelerating the rotational speed, the other switch disposed between the DC motor and the power source that is open when one switch is closed and the drive current is flowing. A DC motor driver configured to release a counter electromotive force of the DC motor generated in a direction opposite to the drive current by closing the switch.

The invention according to claim 2 is the DC motor driver,
The application of the drive current performed during the CW rotation is controlled by opening and closing a second switch disposed between the DC motor and GND, and the back electromotive force generated by opening and closing the second switch is controlled by the third switch. Escape by opening and closing,
The application of the drive current performed during the CCW rotation is controlled by opening and closing a fourth switch disposed between the DC motor and GND, and the back electromotive force generated by opening and closing the fourth switch is controlled by the first switch. It is configured to escape by opening and closing.

The invention described in claim 3 is the DC motor driver,
The opening or closing of the third switch or the first switch that is driven when the current caused by the back electromotive force is released has passed a minute time since the opening or closing of the second switch or the fourth switch that controls the driving current. It is characterized by being performed later.

The DC motor driver according to the present invention can discharge the back electromotive force of the DC motor in a timely manner, so that it can quickly change the speed and change the rotation direction. In addition, there is an effect that it is possible to minimize the overshoot that occurs when changing the speed or the direction of rotation.
In addition, since the above-described control with less overshoot and quick change of speed and change of rotation direction can be performed only by opening / closing control of the switch, a DC motor driver having a complicated structure and control is provided. Has the effect of being able to.

It is the figure which showed typically the structure of the DC motor driver concerning this invention. It is the figure which showed typically the DC motor driver CW direction operation | movement concerning this invention. It is the figure which showed typically the DC motor driver CCW direction operation | movement concerning this invention. It is the figure which showed typically the rotation direction switching of the conventional general DC motor driver. It is the figure which showed typically the speed control by PWM of the conventional general DC motor driver.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of a DC motor driver 1 according to the present invention including a DC motor 2.
The DC motor driver 1 controls the rotation direction and the rotation speed by supplying controlled electric power to terminals 3 and 4 of the DC motor 2. The DC motor driver 1 is composed of a control means 5 constituted by a one-chip microcomputer, four switches S1, S2, S3, S4 opened and closed by the control means 5, a power source 6 for generating a direct current, and other means. Yes.

The DC motor driver 1 includes a switch S1 (first switch) disposed between the power source 6 and the DC motor 2 and a switch disposed between the DC motor 2 and GND in order to configure a drive circuit for CW rotation. S4 (second switch) is included. Further, in order to configure a drive circuit for CCW rotation, a switch S3 (third switch) disposed between the power source 6 and the DC motor 2 and a switch S2 (fourth switch) disposed between the DC motor 2 and GND. Switch). In the present embodiment, transistors, MOS-FETs, IGBTs, or the like are used for the four switches S1, S2, S3, S4.
A diode D2 is provided in parallel with the switch S4, and a diode D1 is provided in parallel with the switch S2.

  The four switches S1, S2, S3, S4, the diodes D1, D2 and the control means 5 are provided on the same substrate as an example. As the diodes D1 and D2, for example, when the switch is a MOSFET, a built-in diode can be used, and it may not be necessary to add it to the outside.

FIG. 2 is a diagram in which the control of this embodiment is characteristically written. 2A is a diagram for explaining the operation of the DC motor driver 1, and FIG. 2B shows a waveform representing the opening / closing timing of the switches S4 and S3 controlled by the control means 5. FIG.
The drive current for performing the CW rotation flows in the order of the power source 6, the switch S1, the DC motor 2, the switches S4 and GND, and at this time, the switches S3 and S2 are open (off). The drive current flows in a waveform shown in FIG. 2B by opening / closing (ON / OFF) of the switch S4 by PWM control in a state where the switch S1 is closed (ON).
When the switch S4 is switched from on to off, a counter electromotive force is generated in the DC motor 2. This counter electromotive force becomes a resistance when adjusting the speed of the DC motor 2 and controlling the rotation direction, which causes a reduction in control response and causes overshoot.
In the present embodiment, S3 is closed in accordance with the timing when the back electromotive force is generated when S4 is opened, and the back electromotive force of the DC motor 2 is discharged (current flows in the direction of the broken line). That is, the circuit toward GND, the diode D1, the DC motor 2, the switch S3, and the power source 6 is opened, and a current Z1 associated with the counter electromotive force flows.

  Note that the switches S3 and S4 that are alternately switched are not opened and closed simultaneously, and delay times t1 and t2 are provided for each switching as shown in FIG. 2B. The purpose of t1 and t2 is to control with an appropriate time difference so that the switches S3 and S4 are simultaneously closed so that no through current flows from the power source to the GND. As described above, in the control according to the present invention, each time the PWM signal of S4 is OFF, the upper switch S3 is turned on (closed) to release the back electromotive force accumulated in the DC motor.

  As described above, since the counter electromotive force is released every time the PWM signal is turned off, the energy of the counter electromotive force accumulated in the DC motor generated when the rotation direction is changed or the speed is changed is much higher than that of the other case. Therefore, it is possible to change the rotation direction and change the speed instantly. Further, overshoot is reduced.

When CCW rotation is performed, the drive current flows in the order of the power source 6, the switch S3, the DC motor 2, and the switch S2, GND as shown in FIG. At this time, the switch S1 and the switch S4 are open (off). The drive current for CCW rotation flows in the waveform shown in FIG. 3B by opening / closing (ON / OFF) of the switch S2 by PWM control with the switch S3 closed (ON).
When the switch S2 is switched from on to off, a counter electromotive force is generated in the DC motor 2. In the present embodiment, the switch S1 is closed (on) in accordance with the timing at which the switch S2 is opened (off) and back electromotive force is generated, and the back electromotive force of the DC motor 2 is released. That is, the circuit toward GND, the diode D2, the DC motor 2, the switch S1, and the power source 6 is opened, and a current Z2 associated with the counter electromotive force flows.

  Similarly to the case of the CW rotation described above, the switches S1 and S2 are not switched at the same time, but delay times t1 and t2 are provided for each switching as shown in FIG. 3B. The t1 and t2 are for controlling with an appropriate time difference so that the switches S1 and S2 are simultaneously turned ON and no through current flows from the power source 6 to the GND.

The motor driver according to the embodiment described above can obtain the following effects.
Conventionally, a DC motor driver has been required to rotate in accordance with a designated direction and speed after waiting for a sufficient discharge time of the back electromotive force of the DC motor at the time of switching the rotation direction and speed. By releasing the back electromotive force in a timely manner, agile rotation direction and speed switching became possible. Also, since the back electromotive force energy is small at the time of switching, the overshoot is small.
Furthermore, since the back electromotive force can be released only by opening / closing control of each switch by a program or simple sequence control, it is possible to increase the size compared with a conventional motor driver without providing a separate hardware means. It can be formed very compactly.

Claims (3)

A first switch arranged between a power source and a DC motor constituting a drive circuit for CW rotation, and a second switch arranged between the DC motor and GND;
A third switch disposed between the power source and the DC motor constituting a drive circuit for CCW rotation, and a fourth switch disposed between the DC motor and the GND;
Control means for adjusting the rotation direction and rotation speed of the DC motor by intermittently opening and closing each switch,
When changing the rotational direction of the DC motor or decelerating the rotational speed, the other switch disposed between the DC motor and the power source that is open when one switch is closed and the drive current is flowing. A DC motor driver configured to release a counter electromotive force of the DC motor generated in a direction opposite to the drive current by closing the switch. The application of the drive current performed during the CW rotation is controlled by opening and closing a second switch disposed between the DC motor and GND, and the back electromotive force generated by opening and closing the second switch is controlled by the third switch. Escape by opening and closing,
The application of the drive current performed during the CCW rotation is controlled by opening and closing a fourth switch disposed between the DC motor and GND, and the back electromotive force generated by opening and closing the fourth switch is controlled by the first switch. 2. The DC motor driver according to claim 1, wherein the DC motor driver is configured to escape by opening and closing. The opening or closing of the third switch or the first switch that is driven when the current caused by the back electromotive force is released has passed a minute time since the opening or closing of the second switch or the fourth switch that controls the driving current. The DC motor driver according to claim 1, wherein the DC motor driver is performed later.

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