JP2000358392A - Brushless motor driving apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the rotating speed of a motor by shortening the idle period, when the supply voltage is raised. SOLUTION: A Hall element 45 is installed to detect rotating position of a rotor and a current is caused to flow in the bidirectional direction in motor coils L1, L2, by a switch section 10 consisting of first to fourth transistors 11-14 full-bridge connected between the positive terminal +V and a negative terminal GND of a DC power supply to rotate the rotor. At that time, the first and the fourth transistor 11, 14 and the second and the third transistor 12, 13 are turned on alternately by a drive IC 20. During the alternate on period of these transistors, a stationary period is set according to the period, in which counter electromotive force is generated in the motor coils L1, L2 to prevent a through-current. By making a stationary period nearly inversely proportional to the supply voltage, the ratio of the stationary period to the rotation cycle is reduced, to cause the rotating speed of the motor to increase accompanying the increase of the supply voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving device for rotating a rotor by passing a current bidirectionally through a motor coil.

[0002]

2. Description of the Related Art Generally, electronic devices and control devices are susceptible to heat, and need to be cooled when they generate heat. At this time, since the cooling power is insufficient in the natural cooling, forcibly cooling with a fan such as an axial fan, a transverse fan, a centrifugal fan or the like has been conventionally performed in order to ensure normal operation of the device. The DC brushless motor is suitable for driving such a device cooling fan because of its excellent characteristics of high reliability and long life.

FIG. 3 shows a schematic configuration of a conventional DC brushless motor driving device. As shown in FIG. 3, four switching transistors connected in full bridge are connected between a positive terminal + V and a negative terminal GND of a DC power supply. A switch unit 1 including Q1 to Q4 is provided.

At this time, PNP transistors Q1, Q
2 are connected to the positive terminal + V, the emitters of the NPN transistors Q3 and Q4 are both connected to the negative terminal GND, and the collectors of the transistors Q1 and Q3 and the collectors of the transistors Q2 and Q4 are connected.

Between a connection point P1 between the collectors of the transistors Q1 and Q3 and a connection point P2 between the collectors of the transistors Q2 and Q4, a DC brushless motor (not shown) is wound around the rotor. Both ends of the two-phase motor coils L1 and L2 connected in series are respectively connected.

The switch unit 1 is controlled by the drive IC 2 and the drive circuit 3 shown in FIG. 3, and an ON control signal is supplied from the drive circuit 3 to the base of each of the transistors Q1 to Q4 according to the output of the drive IC 2. The output is performed, and the transistors Q1 to Q4 are turned on and off. At this time,
An ON control signal is output from the drive circuit 3 so that the transistors Q1 and Q4 are simultaneously turned on and the transistors Q2 and Q3 are simultaneously turned on.

By the way, as shown in FIG.
2, two output terminals of a Hall element H for magnetically detecting the rotational position of the rotor with respect to the stator and outputting a detection signal are connected. One end of the Hall element H is connected to a current limiting resistor R1.
To the positive terminal + V of the DC power supply, and the other end to the negative terminal GND.
Connected to each other. Then, based on the detection signal output from the Hall element H to the driving IC 2, the driving I
The timing of phase switching is detected by C2, and a driving signal is output from the driving IC 2 to the drive circuit 3 at the timing of phase switching.

As shown in FIG. 3, a driving IC is provided between a positive terminal + V of a DC power supply and a power supply terminal of the driving IC 2.
2 is provided between the resistor R2 and the negative terminal GND.
An R4 series circuit is provided. Further, a charging / discharging circuit 4 composed of a series circuit of a resistor R5 and a capacitor C1 is connected in parallel to a series circuit of the two voltage dividing resistors R3 and R4, and a connection point P3 of the two voltage dividing resistors R3 and R4, a resistor R5 and a resistor R5. The connection point P4 of the capacitor C1 is connected to the input terminal of the driving IC2.

The driving IC 2 has a built-in discharge transistor which operates at the timing of phase switching and discharges the capacitor C1, and also has a built-in comparator for comparing the voltages at the connection points P3 and P4. Therefore, while the voltage at the connection point P4 is lower than the voltage at the connection point P3 due to the discharge of the capacitor C1, a pause command signal is output to the drive circuit 3 so as to turn off all the transistors Q1 to Q4 for a certain time. Thus, all the transistors Q1 to Q
By providing a constant pause time (for example, several hundred μs) in which transistor 4 is turned off, excessive through current is prevented from flowing due to simultaneous turning on of transistors Q1 and Q3 (or transistors Q2 and Q4), and transistors Q1 and Q3 (Or the transistors Q2 and Q4) are prevented from being destroyed.

Therefore, all the transistors Q1 to Q4 of the switch unit 1 are turned off for a certain pause time at the timing of the phase switching, and thereafter, for example, the transistors Q1 and Q4 are turned off.
After Q4 is turned on, a current flows through the motor coils L1 and L2 in the direction of the solid line arrow in FIG. 3, and all the transistors Q1 to Q4 are again turned off for a certain pause time, and then the transistors Q2 and Q3 are turned on. The motor coils L1, L
2, a current flows in the direction of the dashed arrow in FIG. 3, and by repeating such an operation, an alternating magnetic field generated in the motor coils L1 and L2 and a magnetic field formed by the motor magnet are repelled. Acts to rotate the motor.

[0011]

However, in the case of the above-described drive device, for example, when the power supply voltage is increased, the rotation cycle of the rotor is reduced, but the idle time is constant regardless of the power supply voltage. , The ratio of the idle time to the rotation cycle gradually increases, and as a result, there is a disadvantage that the rotation speed of the motor does not increase so much even if the power supply voltage is increased.

An object of the present invention is to shorten the idle period when the power supply voltage is increased so that the motor speed can be smoothly increased.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a rotational position detecting unit for detecting a rotational position of a rotor with respect to a stator and outputting a detection signal, and positive and negative terminals of a DC power supply. One set of the switching elements and four sets of the remaining switching elements, which are composed of four switching elements connected in a full bridge therebetween and disposed on opposite sides of the bridge, are alternately turned on and bidirectionally connected to the motor coil. A switch unit for passing a current, and a pause setting for setting a pause time for turning off all of the switching elements between turning on of the one set of switching elements and turning on of the remaining one set of switching elements. A pause time setting unit that generates a signal, and a control terminal of each switching element that is turned on at a predetermined timing by the detection signal and the pause setting signal. A control unit that outputs a signal to turn on the set of switching elements and the remaining set of switching elements alternately with the pause time interposed therebetween, wherein the pause time generates a back electromotive force of the motor coil. It is characterized in that it is set according to time.

According to this structure, the generation time of the back electromotive force of the motor is substantially inversely proportional to the power supply voltage. Therefore, the pause time set by the pause time setting unit can be varied substantially in inverse proportion to the power supply voltage. Will be possible.

Therefore, when the power supply voltage is increased, the pause time by the pause time setting unit is shortened, the ratio of the pause time to the rotation cycle of the rotor is reduced, and the motor speed increases with the rise of the power supply voltage. On the other hand, when the power supply voltage is reduced, the pause time increases, the ratio of the pause time to the rotation cycle of the rotor increases, and the motor rotation speed decreases with a decrease in the power supply voltage.

Here, it is desirable to use a Hall element for the rotational position detecting section for detecting the rotational position of the rotor in the brushless motor. However, a non-contact sensor other than the Hall element may be used. Further, it is preferable to use a transistor as a switching element included in the switch portion.

Further, according to the present invention, the pause time setting section may include:
A charge / discharge circuit including a time constant resistor and a capacitor, and the capacitor of the charge / discharge circuit is forcibly discharged while the back electromotive force of the motor coil is generated, so that the output voltage of the charge / discharge circuit is reduced to a reference value or less. And a comparison circuit that compares the output voltage of the charge / discharge circuit with a predetermined reference value and outputs the pause setting signal when the output voltage of the charge / discharge circuit is equal to or less than the reference value. It is characterized by being.

With this arrangement, the charge / discharge circuit is forcibly discharged by the reduction circuit while the back electromotive force of the motor coil is generated, and the output voltage of the charge / discharge circuit is reduced to a reference value or less. The pause setting signal is output for substantially the same time as the back electromotive force generation time of the motor coil, which is almost in inverse proportion to the time, and the pause time proportional to the back electromotive force generation time of the motor coil can be set.

Further, the present invention is characterized in that the reduction circuit comprises a series circuit of a diode connected to both ends of the motor coil and the capacitor of the charging / discharging circuit and switching means.

With this configuration, while the back electromotive force is generated in the motor coil, the switching means operates and the capacitor of the charge / discharge circuit is forcibly discharged, so that the back electromotive force of the motor coil is substantially inversely proportional to the power supply voltage. It is possible to reduce the output voltage of the charge / discharge circuit to a reference value or less for substantially the same time as the generation time. Here, it is preferable to use a transistor as the switching means.

[0021]

1 and 2 show an embodiment in which the present invention is applied to a DC brushless motor used for driving a forced cooling fan of an electronic device, a control device, and the like.
This will be described with reference to FIG. 1 is a connection diagram, and FIG. 2 is a timing chart for explaining the operation.

As shown in FIG. 1, the positive terminal of the DC power supply + V
A switch unit 10 including four switching transistors 11 to 14 connected in full bridge is provided between the negative terminal GND and the negative terminal GND.

At this time, the emitters of the PNP first and second transistors 11 and 12 are both connected to the positive terminal + V,
The emitters of the NPN third and fourth transistors 13 and 14 are both connected to the negative terminal GND, and the collectors of the first and third transistors 11, 13 and the collectors of the second and fourth transistors 12, 14 are connected. ing. In addition, 1
5, 16, 17, and 18 are bias resistors of the transistors 11 to 14, respectively.

The first and third transistors 11, 13
Is connected between the connection point A between the collectors of the first and second transistors and the connection point B between the collectors of the second and fourth transistors 12 and 14.
Both ends of two-phase motor coils L1 and L2 wound around a rotor of a brushless motor (not shown) and connected in series are respectively connected.

Each of the transistors 1 of these switch units 10
1 to 14 are controlled by a drive IC 20 and fifth and sixth PNP drive transistors 21 and 22.
That is, the fifth and sixth transistors 21 and 22 are alternately turned on by a low-level (hereinafter, L) on-control signal alternately output from the two output terminals of the driving IC 20.

When the fifth transistor 21 is turned on, the base of the first transistor 11 becomes L and the first transistor 11 is turned on. At the same time, the base of the fourth transistor 14 is set to a high level (hereinafter referred to as H
), And the fourth transistor 14 is turned on.

On the other hand, when the sixth transistor 22 is turned on, the base of the second transistor 12 becomes L and the second transistor 12 is turned on. At the same time, the base of the third transistor 13 becomes H via the resistor 25 and the second transistor 12 becomes H. The three transistors 13 are turned on.

As described above, the full bridge-connected first
Among the fourth to fourth transistors 11 to 14, one set of the first and fourth transistors 11 and 14 arranged on the opposite sides of the bridge are simultaneously turned on, and the remaining one set of the second and third transistors 12 and 13 Are turned on at the same time, a current flows in both directions through the motor coils L1 and L2 connected in series, and a single-phase bipolar driving of the brushless motor is realized.

Reference numerals 27 and 28 denote bias resistors of the fifth and sixth transistors 21 and 22, and 29 denotes a current limiting resistor provided between the positive terminal + V of the DC power supply and the power supply terminal of the driving IC 20. .

Reference numerals 30, 31 denote current limiting resistors and capacitors for lock protection circuits provided in series between the power supply terminal of the driving IC 20 and the negative terminal GND of the DC power supply. Drive IC at the connection point
The output terminal Ro of the charging circuit of the capacitor 31 built in 20 is connected. Further, the drive IC 20 has a built-in discharge circuit for the capacitor 31 and a switching transistor for giving a discharge command, and the discharge circuit and the transistor are connected to the output terminal Ro.

When the lock state of the motor is detected, the lock protection circuit temporarily stops the flow of current to the motor coils L1 and L2, and thereafter, at a constant duty corresponding to the terminal voltage of the capacitor 31, the motor coil L1 , L2 are intermittently controlled to protect the motor coils L1 and L2 from rising above the allowable temperature.

The switch section 10 is provided with a snubber circuit 35. As shown in FIG. 1, the snubber circuit 35 has a diode whose cathode and anode are connected to the point A and the negative terminal GND of the DC power supply. 36, a diode 37 having a cathode and an anode connected to the point B and the negative terminal GND, a capacitor 38 having both ends connected to the point A and the base of the third transistor 13, and a point B and a fourth terminal.
It comprises a capacitor 39 having both ends connected to the base of the transistor 14.

Then, based on the phase switching timing detected by the Hall element described later, the motor coil L
1, when the current direction to L2 switches, the motor coil L
1, a back electromotive force called a kickback voltage higher than the power supply voltage is generated in L2 in order to flow a current in the same direction.

For example, the first and fourth transistors 11, 1
When a current flows through the motor coils L1 and L2 in the direction of the solid line arrow in FIG. 1 by turning on the switch 4, a kickback voltage is generated in the motor coils L1 and L2 when the current direction is switched. DC power supply negative terminal GND, diode 36, motor coils L1, L
2. Snubber power is consumed through the path of the fourth transistor 14.

On the other hand, the second and third transistors 12 and 13
When a current flows through the motor coils L1 and L2 in the direction of the dashed arrow in FIG. 1 due to turning on, a kickback voltage is generated in the motor coils L2 and L1 when the current direction is switched. Is the negative terminal GN
D, the diode 37, the motor coils L2 and L1, and the snubber power are consumed through the path of the third transistor 13.

By the way, in order to consume the snubber power, the off timing of the third transistor 13 is later than that of the second transistor 12, and the fourth transistor 1 is turned off.
The lowering of the base voltage of the third and fourth transistors 13 and 14 is delayed by the capacitors 38 and 39 so that the turn-off timing of the transistor 4 is later than that of the first transistor 11.

Further, the anode of the diode 40 is connected to the point A, the emitter of the PNP-type seventh transistor 41 is connected to the cathode of the diode 40, and the collector of the seventh transistor 41 is connected to the collector of the sixth transistor 22. Have been. On the other hand, a diode 42
Is connected to the cathode of the diode 42, the emitter of the PNP-type eighth transistor 43 is connected to the cathode of the diode 42, and the collector of the eighth transistor 43 is connected to the collector of the fifth transistor 21. The base of 43 is connected to the positive terminal + V of the DC power supply.

If a kickback voltage is generated at points A and B during the phase switching, the seventh transistor 41 is turned on by the kickback voltage, for example, and the diode 4 is turned on.
A current due to the kickback voltage flows to the base of the third transistor 13 via the zero, the seventh transistor 41, and the resistor 25. As a result, the third transistor 13 is turned on, and the current due to the kickback voltage flows to the negative terminal GND of the DC power supply via the third transistor 13 in the on state, so that the kickback voltage is suppressed.

Similarly, when the eighth transistor 43 is turned on by the kickback voltage, a current due to the kickback voltage flows to the base of the fourth transistor 14 via the diode 42, the eighth transistor 43, and the resistor 24, and the fourth transistor 14 is turned on. It turns on and the kickback voltage is suppressed. At this time, the voltages at the points A and B are suppressed to a voltage just before the seventh and eighth transistors 41 and 43 are turned on (for example, a voltage higher than the power supply voltage by about 1.4 V).

Further, as shown in FIG.
Are connected to both output terminals of a Hall element (HE; Hall Element) 45 as a rotation position detection unit that magnetically detects a rotation position of the rotor with respect to the stator and outputs a detection signal.
One end of the Hall element 45 is connected to the positive terminal + V of the DC power supply via the current limiting resistor 46, and the other end is connected to the negative terminal GND. Then, the driving element I
C20 based on the detection signal output to C20.
, The timing of the phase switching is detected, and at this timing of the phase switching, the L ON control signal is output to the bases of the fifth and sixth transistors 21 and 22 from both output terminals of the driving IC 20.

Further, as shown in FIG.
A series circuit of three voltage dividing resistors 47, 48, and 49 is provided between the power supply terminal of the DC power supply and the negative terminal GND of the DC power supply. Further, a charging / discharging circuit 52 composed of a series circuit of a time constant resistor 50 and a capacitor 51 is connected in parallel to the series circuit of each of the voltage dividing resistors 47 to 49, and a connection point C between the resistor 50 and the capacitor 51 of the charging / discharging circuit 52. And a connection point D between the voltage dividing resistors 47 and 48 are connected to two input terminals of the driving IC 20.

Further, as shown in FIG. 1, the collector of an NPN-type ninth transistor 56 is connected to a point C via a current limiting resistor 55, and the base of the ninth transistor 56 is connected to the voltage dividing resistor 48. Connected to the connection point with the
Two diodes 5 are connected to the emitter of the transistor 56.
7 and 58 are connected, and these diodes 5
The cathodes 7 and 58 are connected to points A and B, respectively.

At this time, the resistor 55 and the ninth transistor 5
6 and both diodes 57 and 58, a reduction circuit 59 is configured.
While the kickback voltage (back electromotive force) is generated in L2, the capacitor 51 of the charge / discharge circuit 52 is forcibly discharged,
The voltage at the point C, which is the output voltage of the charging / discharging circuit 52, is reduced to be lower than the voltage at the point D, which is the reference value.

The driving IC 20 has a built-in comparison circuit for comparing the voltages at the points C and D, and when the voltage at the point C is lower than the voltage at the point D due to the discharge of the capacitor 51. , Fifth and sixth transistors 21 for driving,
A stop command signal is output to the switch 22 to turn off the first to fourth transistors 11 to 14.

This prevents an excessive through current from flowing due to, for example, the simultaneous turning on of the first and third transistors 11 and 13 or the simultaneous turning on of the second and fourth transistors 12 and 14. The destruction of the transistors 11 to 14 is prevented.

Here, the charging / discharging circuit 52, the reducing circuit 59, and the comparison circuit of the driving IC 20 constitute a pause time setting section, and the function of the pause time setting section causes the switching section 10 to switch the phase of the switch section 10 at the timing of phase switching. The first to fourth transistors 11 to 14 are turned off for a predetermined pause time.

By the way, for example, the motor coils L1, L2
When a kickback voltage (back electromotive force) is generated so that a current flows in the direction indicated by the solid line arrow in FIG. 1, as shown in FIG.
While the ninth transistor 56 is on and the kickback voltage is generated, the ninth transistor 56 and the diode 5
7, the discharge current of the capacitor 51 of the charging / discharging circuit 52 flows through the path of the point A and the motor coils L1 and L2, and the voltage at the point C becomes lower than the voltage at the point D which is a reference value.

When the kickback voltage disappears,
As shown in FIG. 2, the ninth transistor 56 is turned off, and thereafter, the capacitor 51 is charged with the time constant determined by the time constant resistor 50 and the capacitor 51, the voltage at the point C rises, and the voltage at the point C eventually becomes the point D. Voltage. The time constant at this time is set to be smaller than the time constant of the resistor R5 and the capacitor C1 shown in FIG.

Therefore, as shown in FIG. 2, the T time from when the ninth transistor 56 is turned on until the ninth transistor 56 is turned off due to the disappearance of the kickback voltage, and the time when the capacitor 51 is turned off after the ninth transistor 56 is turned off. The total time including the time t until the voltage at the point C exceeds the voltage at the point D due to charging is a pause time, and the pause time corresponding to this (T + t) time is determined by the drive IC 20 to the fifth and sixth transistors 21. , 22 will be output a pause command signal.

Since the generation time of the kickback voltage is substantially inversely proportional to the power supply voltage, the pause time becomes shorter when the power supply voltage is increased, and the ratio of the pause time to the rotation cycle of the rotor becomes smaller. Conversely, when the power supply voltage is lowered, the pause time increases, and thus the pause time can be changed almost in inverse proportion to the power supply voltage, especially when the power supply voltage is raised to increase the motor speed. The number of revolutions rises smoothly.

Then, for example, the first and fourth transistors 1
After the first and fourth transistors 11 and 14 are turned on and a current flows through the motor coils L1 and L2 in the directions indicated by solid arrows in FIG. 1, the first to fourth transistors 11 to 14 are temporarily turned off, and then the second and third transistors 12 and 14 are turned off. , 13 are turned on and the motor coil L
2, a current flows in the direction of the dashed arrow in FIG. 1, and the first to fourth transistors 11 to 14 are turned off once again.
1, the alternating magnetic field generated in L2 and the magnetic field formed by the motor magnet repel, whereby a rotational force acts on the rotor to rotate the motor.

As described above, the driving IC 20 outputs the ON control signal of L to the bases of the fifth and sixth transistors 21 and 22 at a predetermined timing, and outputs the first and fourth transistors 11 and 14 and the second and fourth transistors 11 and 14. It functions as a control unit that turns on the third transistors 12 and 13 alternately with a pause between them.

Therefore, according to the above-described embodiment, the pause time can be varied almost in inverse proportion to the power supply voltage by the pause time setting unit including the charge / discharge circuit 52, the reduction circuit 59, and the comparison circuit of the driving IC 20. As a result, the pause time becomes shorter when the power supply voltage is increased, and the ratio of the pause time to the rotation cycle of the rotor can be reduced. As a result, the motor speed can be smoothly increased as the power supply voltage increases. become.

In the above-described embodiment, the reduction circuit 59 for forcibly discharging the charge / discharge circuit 52 to reduce the output voltage of the charge / discharge circuit 52 to a reference value or less includes the resistor 55, the ninth transistor 56, and the diode. Although the configuration is made up of 57 and 58, the present invention is not particularly limited to this configuration. In other words, if the capacitor 51 of the charge / discharge circuit 52 can be forcibly discharged while the kickback voltage is generated in the motor coils L1 and L2. However, any configuration may be used.

Further, the rotational position detecting section is not limited to the above-described Hall element 45, and a non-contact type sensor other than the Hall element or another contact type sensor may be used.

Further, the switching elements constituting the switch section 10 and the switching means of the reduction circuit 59 are not limited to the PNP-type or NPN-type transistors described above, but may be field-effect transistors. Of course.

In the above-described embodiment, the case where the present invention is applied to a DC brushless motor for driving a fan has been described. However, it goes without saying that the present invention can be applied to a brushless motor used for other purposes. In any case, an effect equivalent to that of the above-described embodiment can be obtained.

The present invention is not limited to the above embodiment, and various changes other than those described above can be made without departing from the gist of the present invention.

[0059]

As described above, according to the first aspect of the present invention, the pause time is set in accordance with the generation time of the back electromotive force of the motor coil, so that the pause time is almost inversely proportional to the power supply voltage. Can reduce the idle time when the power supply voltage is increased, reducing the ratio of the idle time to the rotor rotation cycle, and smoothly increasing the motor rotation speed as the power supply voltage increases. Becomes possible,
A brushless motor having good characteristics can be provided.

According to the second aspect of the present invention, the pause time setting section can output the pause setting signal for substantially the same time as the back electromotive force generation time of the motor coil, which is substantially inversely proportional to the power supply voltage. In addition, it is possible to set the pause time in accordance with the generation time of the back electromotive force of the motor coil.

According to the third aspect of the present invention, the output voltage of the charge / discharge circuit is reduced to the reference value or less for substantially the same time as the back electromotive force generation time of the motor coil which is substantially inversely proportional to the power supply voltage. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a connection diagram of one embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the embodiment of the present invention;

FIG. 3 is a connection diagram of a conventional example.

[Explanation of symbols]

 L1, L2 Motor coil 10 Switch section 11-14 First to fourth transistor 20 Driving IC 45 Hall element (rotational position detecting section) 50 Time constant resistance 51 Capacitor 52 Charge / discharge circuit 59 Reduction circuit

Claims (3)

[Claims] 1. A rotating position detecting section for detecting a rotating position of a rotor with respect to a stator and outputting a detection signal, and four switching elements connected in a full bridge between positive and negative terminals of a DC power supply, facing the bridge. One set of the switching elements and the remaining one
A switch unit in which a set of the switching elements are alternately turned on to allow a current to flow bidirectionally to the motor coil; and between the on of the one set of switching elements and the on of the remaining one set of switching elements. A pause time setting unit for generating a pause setting signal for setting a pause time for turning off the switching element, and controlling the control terminal of each switching element to turn on at a predetermined timing by the detection signal and the pause setting signal. A control unit that outputs a signal to turn on the set of switching elements and the remaining set of switching elements alternately with the pause time interposed therebetween, wherein the pause time generates a back electromotive force of the motor coil. A brushless motor drive device set according to time. 2. The method according to claim 2, wherein the pause time setting unit forcibly discharges the capacitor of the charge / discharge circuit while the back electromotive force of the motor coil is generated. A reduction circuit for reducing the output voltage of the charge / discharge circuit to a reference value or less, and comparing the output voltage of the charge / discharge circuit with a predetermined reference value, and comparing the output voltage of the charge / discharge circuit with the reference value or less. 2. The brushless motor driving device according to claim 1, further comprising a comparison circuit that outputs the pause setting signal. 3. The brushless motor according to claim 2, wherein said reduction circuit comprises a series circuit of a diode and switching means connected at both ends to said motor coil and said capacitor of said charging / discharging circuit. Drive.