JP2003319677A - Motor control device - Google Patents

Abstract

(57) [Problem] Generally, a DC brushless fan motor is used as a means for cooling a CPU of a notebook computer or the like, and a low-frequency fan motor is used to control the rotation speed of the fan motor. Although the power supply PWM control method is used, a click sound (click noise) is generated from the fan motor by turning on / off the switching transistor, which is extremely annoying to a user of the device. A switching element is provided in an energizing circuit of a DC fan motor, and the switching element is connected to a low-frequency power source P.
What is claimed is: 1. A fan motor drive device configured to be controlled by a WM control method, wherein a bipolar transistor 2 is used as a switching element and a small-capacity turn-off delay capacitor 3 is provided between its base and collector. When switching off
The click noise (click noise) of the C motor is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan motor used for cooling a CPU (central processing unit) of a notebook personal computer, and more particularly to a motor control device which can be used with a low driving sound.

[0002]

2. Description of the Related Art FIG. 7 is a circuit configuration diagram of a motor drive inside a DC fan motor, and FIG. 8 is a circuit configuration diagram of a conventional DC fan motor control device.

Generally, a notebook personal computer or the like is equipped with a fan motor for cooling the CPU because the CPU, which is a functional component thereof, generates heat. For this fan motor, in terms of power saving, device space, and life,
A magnet has been used for the rotor, and a small brushless DC fan motor having a drive circuit has been used.

FIG. 7 shows a drive circuit for the DC fan motor. The drive circuit of the DC fan motor includes a hall element 21 which is a rotor position detecting element and a motor winding 1
It has a configuration having a driver IC 20 that commutates 9. Reference numeral 22 in the figure is a Hall element bias resistor.

From the viewpoint of noise and power saving, the above DC fan motor is designed to perform rotation speed control such that the rotation speed of the fan is changed according to heat generation of the CPU, and the rotation speed control is low. Frequency power supply PWM control method is adopted. That is, as shown in FIG. 8, the switching element 2 is provided in the power supply line of the DC fan motor, and the switching element 2 is controlled to be turned on / off via the control element 4 by the PWM signal. In the figure, 5 is a circuit resistance and 6 is a base resistance.

[0006]

By the way, in the rotation speed control of the DC fan motor, when the power supply PWM control is performed at a low frequency of about 30 Hz, the DC fan motor emits a clicking sound (clicking sound) and the device is used. There is a problem that people are extremely audible.

The click sound is generated when the switching element 2 is turned on and off, particularly when it is turned off. It is considered that this is because the motor torque ripple becomes large because the current sharply decreases when the switching element is turned off. That is, it is considered that the rotor in the DC fan motor is generated by abrupt movement in the axial direction due to a deviation of the magnet center from the stator when the rotor is off.

For this reason, as shown in FIG. 8, a capacitor 23 having a large capacity of about 10 μF is provided between the DC power supplies of the DC fan motor. However, even in this configuration, the click noise cannot be sufficiently reduced. In addition, there are problems that the cost of the parts used increases and that a large mounting area is required on the printed board for mounting the capacitor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control device having the above-mentioned conventional problems and having a simple structure and capable of reducing a click sound during operation.

[0010]

In order to achieve the above object, the present invention provides a motor control device having a configuration in which a switching element is provided in a current-carrying circuit of a DC motor, and the switching element is controlled by a PWM signal. Use a bipolar transistor or field effect transistor as the switching element, and provide a small capacitor between the base and collector of the bipolar transistor or between the gate and drain of the field effect transistor to reduce the turn-off speed of the switching element. The motor control device is configured to control.

According to the present invention, since the turn-off speed of the switching element provided in the energizing circuit of the DC motor becomes slow, the click sound at the turn-off of the switching element during the control of the DC motor is reduced. It is possible to provide a small-sized and inexpensive motor control device that does not require a large-capacity capacitor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a motor control device comprising a switching element provided in an energizing circuit of a DC motor and a control means for controlling the switching element with a PWM signal. Thus, the motor drive device is configured to control the turn-off speed of the switching element to be slow, and has an effect of reducing the click sound when the switching element is turned off during DC motor control so as not to be audible.

According to a second aspect of the present invention, in the motor control device according to the first aspect, the means for controlling the turn-off speed of the switching element to be slow uses a bipolar transistor as the switching element. It is constructed by inserting a capacitor between the base and collector of the bipolar transistor, and by adding simple parts, click noise at the time of turning off the bipolar transistor during control of a DC motor is reduced so as not to be audible. Have an effect.

According to a third aspect of the present invention, in the motor control device according to the second aspect, a capacitor inserted between the base and collector of the bipolar transistor is provided so that the trailing edge of the ON / OFF conduction waveform is gentle. The addition of the small-capacitance capacitor has the effect of reducing the click sound at the time of turning off the bipolar transistor during DC motor control so as not to be unpleasant to the ear, and at the same time making the device inexpensive.

According to a fourth aspect of the present invention, in the motor control device according to the first aspect, the means for controlling the turn-off speed of the switching element to be slow uses a field effect transistor as the switching element. ,
It is configured by inserting a capacitor between the gate and drain of the field effect transistor, and by adding simple parts, click noise at turn-off of the field effect transistor during DC motor control is reduced so as not to be audible. Has the effect of

According to a fifth aspect of the present invention, in the motor control device according to the fourth aspect, the capacitor inserted between the gate and the drain of the field effect transistor is
This is a small-capacity capacitor that slows down the on / off current waveform.
The click sound at the time of turning off the field effect transistor at the time of controlling the C motor is reduced so as not to be audible, and at the same time, the cost of the device is reduced.

According to a sixth aspect of the present invention, in the motor control device according to any of the first to fifth aspects, the switching element is installed in the GND line of the DC motor, which is an inexpensive NPN bipolar. Transistor and N
A channel field effect transistor can be used, which has the effect of making the device inexpensive.

According to a seventh aspect of the present invention, in the motor control device according to any one of the first to sixth aspects, a switching element is installed inside the DC motor, and a side for controlling the DC motor. This has the effect of reducing the number of parts in.

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a circuit configuration diagram of a motor control device according to Embodiment 1 of the present invention, FIG. 2 (a).
FIG. 2 is an ON / OFF waveform diagram of the switching elements of the energizing circuit in the motor control device of the present invention, and FIG. 2B is an ON / OFF waveform diagram of the switching elements of the energizing circuit in the conventional motor control device.

The motor control device according to the first embodiment is
As shown in FIG. 1, it comprises a bipolar transistor 2 which is a switching element provided in an energizing circuit for a DC fan motor 1 and a control element 4 of the bipolar transistor 2 according to a PWM signal. 0.047 between the base and collector
A turn-off delay capacitor 3 having a small capacity of about μF is connected. In the figure, 5 is a circuit resistance and 6 is a base resistance of the bipolar transistor 2.

Here, in controlling the rotation speed of the fan motor, the bipolar transistor 2 is connected to the power source PWM.
Since the bipolar transistor 2 is controlled and a small capacity capacitor 3 is connected between the base and collector of the bipolar transistor 2, the switching waveform of the bipolar transistor 2 is as shown in FIG. The turn-off becomes slower, that is, the turn-off is delayed.
Note that FIG. 2B shows ON / OFF waveforms of the switching elements in the conventional driving device.

As described above, in the first embodiment, the turn-off of the bipolar transistor 2 is delayed in the power supply PWM control of the rotation speed of the DC motor, so that the click sound during the DC motor control is reduced so as not to be audible. be able to.

(Second Embodiment) FIG. 3 is a circuit configuration diagram of a motor control device according to a second embodiment of the present invention. In FIG. 3, the same components as those in FIG.
The same reference numeral is given.

As shown in FIG. 3, the motor control device of the second embodiment uses a field effect transistor 7 as a switching element, and a small-capacity capacitor 8 is placed between the gate and drain of the field effect transistor 7. 2A, the switching waveform of the field effect transistor 7 has a gradual turn-off, that is, the turn-off is delayed. In the figure, 9 is a circuit resistance and 10 is a gate resistance.

(Third Embodiment) FIG. 4 is a circuit configuration diagram of a motor control device according to a third embodiment of the present invention. In FIG. 4, the same components as those in FIG.
The same reference numeral is given.

In the motor control device of the third embodiment, as shown in FIG. 4, a switching element is installed in the GND line of the DC motor.

Since the bipolar transistor 11 is used as the switching element and the small capacity capacitor 12 is connected between the base and collector of the bipolar transistor 11, as shown in FIG. In the switching waveform of, the turn-off becomes gentle, that is, the turn-off is delayed. In the figure, 13 is a circuit resistance and 14 is a base resistance.

(Fourth Embodiment) FIG. 5 is a circuit configuration diagram of a motor control device according to a fourth embodiment of the present invention. Note that, in FIG. 5, the same components as those in FIG.
The same reference numeral is given.

In the motor control device of the fourth embodiment, as shown in FIG. 5, a switching element is installed in the GND line of the DC motor.

The field effect transistor 15 is used as a switching element.
Since a small-capacity capacitor 16 is connected between the base and the collector of the field effect transistor, the switching waveform of the field effect transistor 15 has a gentle turn-off, that is, a delay in the turn-off, as shown in FIG. In the figure, 17 is a circuit resistance and 18 is a gate resistance.

(Fifth Embodiment) FIG. 6 is a circuit diagram of a motor control device according to a fifth embodiment of the present invention. In FIG. 6, the same components as those in FIG. 1 or FIG. 3 are designated by the same reference numerals.

In the motor control device according to the fifth embodiment, as shown in FIG. 6, the switching element is installed inside the DC motor, that is, in the drive circuit inside the DC motor. Although the bipolar transistor 2 is used as the switching element in FIG. 6, the field effect transistor 7 shown in the second embodiment may be used. Further, although the switching element is installed in the power supply line in FIG. 6, it may be installed in the GND line.

In the first to fifth embodiments, the fan motor for cooling the notebook type personal computer is used, but the fan motor of the present invention may be a cooling fan motor for other electronic equipment.

Further, the motor driving methods of the above-described first to fifth embodiments are single-phase (single-phase) full-wave driving, two-phase half-wave driving, and two-phase half-wave driving.
A DC motor of any one of the three-phase full-wave drive, three-phase half-wave drive and three-phase full-wave drive may be used.

[0036]

As is apparent from the above description, the present invention provides the energizing circuit of the DC motor with the switching element,
In a fan motor drive device configured to perform PWM control of a power supply, a bipolar and a transistor or a field effect transistor are used as a switching element, and a small amount is provided between a base and a collector of the bipolar transistor or between a gate and a drain of the field effect transistor. With a configuration that provides a capacitor for delaying the turn-off of capacitance,
It is possible to reduce a click sound during DC motor control, and to provide a small-sized and inexpensive DC motor control device that does not require a large-capacity capacitor, and has a great effect.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a motor control device according to a first embodiment of the present invention.

FIG. 2A is an ON / OFF waveform diagram of a switching element of an energizing circuit in a motor control device of the present invention. FIG. 2B is an ON / OFF waveform diagram of a switching element of an energizing circuit in a conventional motor control device.

FIG. 3 is a circuit configuration diagram of a motor control device according to a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a motor control device according to a third embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of a motor control device according to a fourth embodiment of the present invention.

FIG. 6 is a circuit configuration diagram of a motor control device according to a fifth embodiment of the present invention.

FIG. 7 is a circuit configuration diagram of a motor drive inside a DC fan motor.

FIG. 8 is a circuit configuration diagram of a conventional DC fan motor control device.

[Explanation of symbols]

1 DC fan motor 2 Bipolar transistor (switching element) 3 capacitor (turn-off delay capacitor) 4 control elements 5 circuit resistance 6 base resistance 7 Field effect transistor 10 Gate resistance

Claims (7)

[Claims] 1. A motor control device comprising a switching element provided in a current-carrying circuit of a DC (direct current) motor and a control means for controlling the switching element with a PWM (pulse width modulation) signal. A motor control device characterized in that control is performed such that a turn-off speed becomes slow. 2. The means for controlling the turn-off speed of the switching element to be slowed down is constituted by using a bipolar transistor as the switching element and inserting a capacitor between the base and collector of the bipolar transistor. The motor control device according to claim 1. 3. The motor control device according to claim 2, wherein the capacitor inserted between the base and collector of the bipolar transistor is a small-capacity capacitor that moderates the fall of the ON / OFF conduction waveform. . 4. The means for controlling the turn-off speed of the switching element to be slowed down is constituted by using a field effect transistor as the switching element and inserting a capacitor between the gate and drain of the field effect transistor. The motor control device according to claim 1, wherein the motor control device is a motor control device. 5. The motor according to claim 4, wherein the capacitor inserted between the gate and the drain of the field effect transistor is a small-capacity capacitor that moderates the fall of the ON / OFF conduction waveform. Control device. 6. The GN of a DC motor is the switching element.
It installs in D line, The 1-5 characterized by the above-mentioned.
The motor control device according to any one of 1. 7. The motor control device according to claim 1, wherein the switching element is installed inside a DC motor.