JPH03145989A - Motor drive - Google Patents

Abstract

PURPOSE:To suppress ripple in source current by performing time difference PWM control of power conduction interval for each phase motor coil for the interval where two-phase excitation is carried out. CONSTITUTION:Since power conduction signal G4, for example, for the first and fourth phase motor coils 161, 164 subjected to two-phase excitation is formed on the basis of a second basic wave VR a time difference is provided between a power conduction signal G1 and the power conduction signal G4 so that they are brought into unmatched state. On the other hand, since power conduction signals G2, G4 for a third phase motor coil 163, for which a power conduction signal G3 is obtained based on the first basic wave Vs, and for the second and fourth phase motor coils 162, 164 subjected to two-phase excitation are formed based on the second basic wave VR, a timer difference is provided between the power conduction signal G3 and the power conduction signal G2, G4 so that they are brought into unmatched state. By such arrangement, ripple in the source current, i.e., driving current and regenerative current, can be suppressed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a motor drive device that performs PWM control on a multi-phase motor coil that is excited to have a two-phase excitation period. Regarding.

(Prior Art) An example of a conventional drive device for, for example, a four-phase variable reluctance motor is shown in FIG. That is, 1 is an AC power supply, 2 is a DC power supply circuit that obtains DC power from this AC power supply 1, and 3 is a smoothing capacitor of this DC power supply circuit 2. 41 to 44
are the 1st to 4th phase motor coils, 5+, 6+ to 5
4.64 indicates these first to fourth phase motor coils 4.
1 to 44 are transistors for controlling power on/off.

FIGS. 10(a) to (d) show excitation period signals SE to SE4 that determine the excitation periods of the first to fourth phase motor coils 4□ to 44. This is a 180 degree excitation type with a phase difference. This 10th
As is clear from the figure, each phase's motor coil 4. to 4
4 has a two-phase excitation period. The motor coils 41 to 44 of each phase are subjected to PWM control during each excitation period, thereby controlling the speed of the variable reluctance motor so that it reaches a set speed.

That is, when performing PWM control of the motor coils 41 to 44 of each phase, the fundamental wave Vs consisting of a triangular wave as shown in FIG. The energization period of the coils 41 to 44 is determined. In this case, for example, the first phase and second phase motor coils 4. and 42, during the two-phase excitation period,
As shown in FIGS. 11(b) and (C), the energization signals (gate signals) G and G2 are applied to each transistor 56I and 52.62, so that as shown in FIGS.
Excitation currents I and 12 flow as shown in e), and therefore the drive current, which is the power supply current, as a whole becomes (I + 12) as shown in FIG. 11(f).

(Problem to be solved by the invention) Conventionally, when performing PWM control, the first
phase and two-phase motor coils4. and an excitation current I of 4□,
As is clear from I2 and I2, the energization periods of the two-phase excitation motor coils coincide (overlap), so the ripples of the drive current and regenerative current, which are power supply currents, become large, and therefore,
There was a problem that the heat loss of the power supply line became large, and the heat generation of the smoothing capacitor 3 also became large, which shortened the life of the capacitor 3.

The present invention has been made in view of the above circumstances, and its purpose is to reduce ripples in the power supply current even in a configuration in which PWM control is performed on a multi-phase motor coil that is excited to have a two-phase excitation period. The object of the present invention is to provide a motor driving device that can be used.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a motor drive device that performs PWM control on a plurality of phases of motor coils that are excited during two-phase excitation periods. The present invention is characterized in that a control means is provided for controlling the energization period of each phase motor coil under PWM control during the phase excitation period so that these periods are in a mismatched state.

(Function) According to the motor drive device of the present invention, the energization period of each phase motor coil during the two-phase excitation period does not overlap, so that when one is in the drive mode, the other is in the regeneration mode. , the ripple in the power supply current becomes smaller.

(Example) Hereinafter, a first example of the present invention will be described with reference to FIGS. 1 to 3.

First, the overall configuration will be described according to FIG.

AC power supply 10 is connected to an input terminal of DC power supply circuit 11 . This DC power supply circuit 11 rectifies an AC power supply voltage, boosts it as necessary, and outputs it as a DC voltage to a power supply line 12.13 connected to an output terminal.
A smoothing capacitor 14 is connected between the power supply lines 12 and 13.
is connected.

A motor, for example, a variable reluctance motor 15, has a stator having a plurality of four-phase motor coils 16r to 164.
and the first to fourth phase motor coils 16. according to the same rotation of the rotor. This is a well-known configuration in which torque is generated in the rotor by energizing the rotors 1 to 164. In these motor coils 16, 164, each terminal is connected to a current detection resistor 17. to 174 and NPN type transistors 18 to 184 as switching elements are connected to the power supply line 12 in series, respectively, and the other terminal of each is connected to the power supply line 13 through one NPN type transistor □ to 194 as switching elements, respectively.
It is connected to the. These transistors 181, 19
．． 184 and 194 are the corresponding motor coils 16, respectively.
．． to 164 excitation currents, each base of which is connected to each output terminal of the drive circuit 20 and receives energization signals (gate signals) G+ to G4 as described later.
is now given. Note that the diode 21.
．． 22+ to 214, 22. is the transistor 1g,,1
9. This is to ensure a circuit that allows a delay current (regenerative current) to flow when the circuits 184, 194 are turned off.

The variable reluctance motor 15 is provided with first and second optical rotary encoders 23 and 24. The first rotary encoder 23 corresponds to a rotational position detection means for detecting the rotational position of the rotor, and outputs two-phase magnetic pole signals SP, A and B, having a phase difference of 90 degrees in electrical angle, corresponding to the magnetic poles of the rotor. . Further, the second rotary encoder 24 is for detecting the rotational speed of the rotor.
A pulse train signal SR corresponding to the rotation speed is output. The output terminal of the second rotary encoder 24 is connected to the input terminal of the F/Ve conversion circuit 25, so that the pulse train signal SR is converted into a voltage signal Sv. Historically, the output terminal of this F/V conversion circuit 25 is connected to the negative (-) input terminal of a subtracter 26, which receives the speed command signal v8 from an external NC machine at the positive (+) input terminal. has been done. This constitutes a speed feedback system, and the subtracter 26 outputs a speed deviation signal ΔV corresponding to the deviation between the commanded speed and the actual speed. The output terminal of this scorer 26 is connected to the input terminal of a PID (proportional/integral/derivative) compensation circuit 27, and the speed deviation signal ΔV is converted into a current command signal ΔV with improved responsiveness and stability. is output as The output terminal of this PID compensation circuit 27 is connected to each positive input terminal of subtracters 281 to 284 for each phase.

On the other hand, current detection resistors 17 . connected in series with the motor coils 161 to 164 of each phase. The detection terminals for 1 to 174 are connected to subtracters 281 to 281 through isolation circuit 29.
84, and thereby the subtracters 281 to 284 output the actual current detection signals Sl, to S
t, and the current command signal I8 are compared. These subtractors 281 to 284 generate a current deviation signal Δ! between the actual current and the command current. 1 to ΔI4, and each output terminal is connected to PWM (pulse width modulation') Lr! via PI (proportional/integral) compensation circuits 301 to 304. l road 31 to 3
14 input terminals 1a.

Now, PWM circuit 31. 314 constitutes the control means 34 together with the first and second fundamental wave generation circuits 32 and 33. The first fundamental wave generation circuit 32 is a triangular wave,
One of the sawtooth waves, for example, the first fundamental wave Vs (
(see FIG. 3(a)), and its output terminal is the input terminal of the second fundamental wave generation circuit 33 and the PWM circuit 31 for the first and third phases. and 31. are connected to each input terminal 1b. Moreover, the second fundamental wave generation circuit 33
is to invert the first fundamental wave VS and output the second fundamental wave VR (see Fig. 3(b)), and its output terminal is connected to the PWM circuits 312 and 314 for the second and fourth phases. are connected to each input terminal 1b. In this case, PWM circuit 31. As is well known, 314 to 314 are current deviation signals Δ
11 to ΔI4, the larger the value, the wider the pulse width. It is connected.

An input terminal of the excitation period control circuit 35 is connected to an output terminal of an excitation period determination circuit 36, and an input terminal of the excitation period determination circuit 36 is connected to the first rotary encoder 23.
output terminal is connected.

Here, the excitation period determination circuit 36 selects the magnetic pole signal S from the first rotary encoder 23 from FIGS.
An excitation period signal SE as shown in d).

These excitation period signals S
E to S E 4 have a phase difference of 90 degrees and are of a 180 degree excitation type. Then, the excitation period signal S E from this excitation period determination circuit 36 is
, is given to the excitation period control circuit 35, the excitation period control circuit 35 passes the corresponding PWM signals P to P4 only during the period when each excitation period signal SEL to SE exists (high level period). In response to this, the drive circuit 20 outputs energization signals (gate signals) G+ to G4. 1st to 4th phase motor coil 1
6 to 164, the transistors 18+, 19+ to 184.194 are turned on by the energization signals G+ to G4, so that a pulse-modulated excitation current flows.

Next, the operation of this embodiment will be explained with reference to FIGS. 2 and 3.

Assuming that the variable reluctance motor 15 is now rotating, the excitation period determining circuit 36 determines the magnetic pole signals S in FIG. The first phase and the second phase as shown in (b)
In addition to outputting phase excitation period signals SE1 and SE2, the third and fourth phase excitation period signals as shown in FIGS. 2(c) and (d) are obtained by inverting these excitation period signals SE and SF3. Outputs SE and SF4. Also, a PWM circuit 31 for the first phase and the third phase. and 31 are the first fundamental wave v5 as shown in FIG. 3(a) from the first fundamental waveform generation circuit 32 and the subtracters 281 and 28. A PWM signal P having a pulse width based on the magnitude of the level signal is compared with the level signal corresponding to the current deviation signal Δ11 and ΔI given through the PI compensation circuits 301 and 30°.
I and P, and PW for the 2nd phase and 4th tllll.
The M circuits 312 and 314 are the second fundamental wave part upper circuit 33
PI compensation circuits 302 and 304 from the second fundamental wave Va and subtractors 282 and 284 as shown in FIG.
A PWM signal signal and 2P4 having a pulse width based on the magnitude of the level signal are output by comparing the level signals corresponding to the current deviation signals Δ12 and Δ14 given through the .

Historically, the excitation period control circuit 35 receives the first phase excitation period signal SE.

The PWM signal type 1 is applied while the 2nd phase excitation period signal SE2 is applied, the PWM signal type 2 is applied while the 2nd phase excitation period signal SE2 is applied, and the 3rd phase excitation period signal SE is applied. While the fourth phase excitation period signal sE4 is being applied, the PWM signal P4 is output. The PWM signals P to P4 outputted from the excitation period control circuit 35 are outputted as energization signals G to G4 from the drive circuit 2o to the transistors 181゜19.
1 to 184,194 bases, so the first
Phase to fourth phase motor coils 16. 〜164 PWM
Control takes place.

Now, according to FIG. 3, the first phase and second phase motor coils 16. The period of two-phase excitation of 16□ and 16□ will be described. The first Aikawa PWM circuit 311 compares the first fundamental wave Vs and the level signal VL corresponding to the current deviation signal Δl, as shown in FIG. ), the PWM signal type 1 is outputted as the energization signal G1 via the excitation period control circuit 35 and the drive circuit 20. In addition, the PWM circuit 31□ for the second phase is shown in Fig. 3 (b
), the second fundamental wave vR and the current deviation signal Δ■
3 (d).
), the PWM signal G2 is inputted, and this passes through the excitation period control circuit 35 and the drive circuit 20 to generate the energization signal G2.
is output as Therefore, transistors 181, 19
1 and 182 and 192 are turned on, respectively, and excitation currents 11 and 12 flow through the first and second phase motor coils 16 I and 162 as shown in FIGS. 3(e) and 3(f). As described above, since the energization signals G1 and G2 are formed from the first fundamental wave Vs and the second fundamental wave vR obtained by inverting the first fundamental wave Vs, there is a time difference between the two so that they are in a mismatched state.

Therefore, both motor coils 16. and excitation current 1 of 16□
．． and I2 also flow with a time difference so as not to overlap, and the drive current (Il+12), which is the power supply current, is
Excitation current as shown in figure (g)! , and I2 are not duplicated.

In this case, for example, when the first phase motor coil 161 is in the drive mode where the excitation current II is supplied, the second phase motor coil 162 has the transistors 182 and 192 turned off and the regenerative current flows through the diodes 21□ and 222. The second phase motor coil 16
When □ is in the drive mode where excitation current ■2 is supplied, the first phase motor coil 16. are transistors 18+, 19
+ is turned off and the regenerative current flows through the diode 21. ．． 22, the regeneration mode is established.

The above description has been made regarding the motor coils 161° and 16□ which are excited in two phases, but the same applies to the other phases. That is, the first phase motor coil 16. Since the energization signal G4 for the fourth phase motor coil 164, which is two-phase excited, is formed based on the second fundamental wave vR, the time difference is set so that the energization signal G and the energization signal G4 are in a mismatched state. Become what you have. Also, the first fundamental wave V.

The energization signals G2 and G4 for the 3rd phase motor coil 163 from which the energization signal G3 is obtained based on the energization signal G3 and the 2nd and 4th phase motor coils 162 and 164 for which the 2-phase excitation is performed are based on the second fundamental wave vR. Therefore, the time difference is set to H so that the energization signal G3 and the energization signals G2 and G4 are in a mismatched state.

In this way, in this embodiment, the first phase and third phase motor coils 16□ and 16. energization signals G and G are formed based on the first fundamental wave v5, and together with these, the second and fourth phase motor coils 162 are energized for two-phase excitation.
and 164, the energizing signals G2 and G4 are the fundamental wave V5.
The second fundamental wave vR is formed based on the inverted second fundamental wave vR.

Therefore, the energization periods of the motor coils of each phase that are two-phase excitation do not overlap, and the ripples of the drive current and regenerative current, which are power supply currents, are made smaller than in the past. Not only can heat loss be reduced, but also the heat generation of the smoothing capacitor 14 can be reduced, thereby preventing the life of the smoothing capacitor 14 from being shortened.

FIGS. 4 and 5 show a second embodiment of the present invention, and the same parts as in the first embodiment are designated by the same reference numerals, and only those parts will be described below.

That is, in this embodiment, instead of the four-phase variable reluctance motor 15, a three-phase variable reluctance motor 15 is used as the motor.
', and the stator has first to third phase motor coils 16. 16 to 16. Then, the first rotary encoder 23 outputs excitation signals S of three phases A, B, and C having a phase difference of 120 degrees in electrical angle, and in response to this, the excitation period determining circuit 36 outputs excitation signals S as shown in FIG. As shown in (a) to (C), first to third phase excitation period signals SE, to SE, are output.

These excitation period signals SE, to SE, have a phase difference of 120 degrees and are of a 180 degree excitation method. Control means 34' replacing the control means 34
are three PWM circuits 311 to 31. of the first to third phases. It also includes a selection circuit 37. In this selection circuit 37, the input terminals 1a and I
b is connected to the output terminals of the fundamental wave generation circuits 32 and 33, and output terminals Oa to Oc are connected to the PWM circuits 31. ~313
The three input terminals IC are connected to the three output terminals of the excitation intercostal space determination circuit 36.

As is clear from Fig. 5, three-phase reluctan smoke 1
5', the two-phase excitation period and the one-phase excitation period in each phase motor coil 161 to 163 occur alternately every 60 degrees, and the selection circuit 37 accordingly selects the first fundamental wave v5. and the second fundamental wave ■3 to the PWM circuit 31. 31 s to 31 s. That is, the selection circuit 37 is supplied with excitation period signals SE to SE1' from the excitation period determination circuit 36, and the selection circuit 37 performs the selection operation as follows based on these signals. Now, consider the first phase excitation period signal S E + as a reference.

First phase excitation period signal SE, electrical angle from 0 degrees to 3
In the first cycle up to 60 degrees, the first fundamental wave V is applied to the first phase PWM circuit 31□. Then 120
At this time, the second phase excitation period signal SE, becomes high level, and in particular, the second fundamental wave vIl is applied to the second phase PWM circuit 31□. Further, at 240 degrees, the third phase excitation period signal SE becomes high level, and at this time, the first fundamental wave vs is applied to the PWM circuit 313 of the third phase. Then, the first phase excitation period signal S E
When + becomes high level at 360 degrees and becomes low for 2 cycles, the second fundamental wave VR is transferred to the PWM circuit for the first phase.
1. give to After that, the second phase excitation period signal SE2
When it becomes 2 cycles low, the first fundamental wave v5 is given to the PWM circuit 312 for the second phase, and the excitation period signal SE of the third phase is
, when is the second cycle, the second fundamental wave vR is changed to the third cycle.
The signal is then applied to Aikawa's PWM circuit 313, and the same operation is repeated. That is, the selection circuit 37 selects the fundamental wave V for one cycle of the first phase excitation period signal SE.
, , V (for example, VS), and 120
The fundamental wave VB for one cycle of the second phase excitation period signal SE2 having a degree phase difference.

vR (for example, VR), and furthermore, the fundamental wave V is assigned for one cycle of the third phase excitation period signal SE,' which has a phase difference of 120 degrees from the second phase excitation period signal
One of S*''H (for example, Vs) is assigned, and thereafter, a selection operation is performed such that fundamental waves Vs and vR are alternately assigned to one cycle of each phase.

Therefore, in this embodiment as well, during the two-phase excitation period, the 3H difference control is performed so that the energization periods of the motor coils of each phase are in a mismatched state, and the same effects and effects as in the previous embodiment are achieved. is obtained.

6 to 8 show a third embodiment of the present invention, and only the parts different from the first embodiment will be explained below. In contrast to the signal forming section which is constructed using hardware, it is constructed using software using a microcomputer 38 as a control means.

That is, the calculation unit 39 receives the speed command signal v8 and the current loss detection signals Sl, S1. are A/Di conversion circuits 40 and 41
, a pulse train signal S++ is also applied, and a system clock signal SCK from a system clock generation circuit 42 is also applied. Further, signals are exchanged between the calculation unit 39 and the timing counter 43, and the timing counter 43 receives the system clock signal S (K) from the system clock generation circuit 42. Here, the timing counter 43 is composed of, for example, a ring counter, and when a start signal is given, it counts the system clock signal SCK shown in FIG. 7(a), and the count value becomes n/2 ( However, "n" is a value corresponding to one cycle of the fundamental wave V), and outputs a timing pulse TP as shown in FIG. 7(b), which alternately repeats high level (H) and low level (L). The arithmetic unit 39 operates as described later and outputs a signal to the PWM signal generator 44 from the system clock generator 42. system clock signal S
CKs can also be given. In this case, PWM
The signal generating section 44 has first to fourth phase counters 451 to 454, and these are, for example, down counters, and when data is preset, they start counting down. The inside is designed to output a noise level signal.

The operation of this third embodiment will be explained with reference to the time chart of FIG. 7 and the flow chart of FIG. 8. Now, when the microcomputer 38 starts operating, the arithmetic unit 39 first performs a normal initialization operation, ``initialization'' processing step S1, and then ``timing counter start'' output step S2. In this output step S2, the arithmetic unit 39 gives a start signal to the timing counter 43, so the timing counter 43 counts the system clock signal SCK as shown in FIG.
) outputs a timing pulse TP as shown in FIG. next,
The calculation unit 39 performs the input step S of “pulse train reading”;
Here, the pulse train signal SR is read and stored in the RAM, and the processing step S4 of "actual speed calculation" is reached.

In this processing step S4, the calculation unit 39 calculates the actual speed from the period of the pulse train signal S11, for example, and stores it in the RAM, and then proceeds to the manual step S of "reading the speed command" to read the speed command signal v1. and store it in RAM,
Next, the process moves to step S6 of "speed deviation calculation". In this processing step S6, the three calculation units calculate a current deviation signal 1'' from the command speed and the actual speed, and calculate the RA.
Store it in M, and perform the next "actual current reading" manual step S.
7, the actual current detection signals Sl to S14 are read and stored in the RAM, and then the process moves to step S8 of "current deviation calculation (pulse width data)". In this processing step S8, the calculation unit 39 calculates the current deviation signal Δ■1
.DELTA.I4 is calculated, and based on this, pulse width data "m" for each phase (where n≧m≧O) is determined and stored in the RAM. After that, the calculation unit 39 determines whether rL-+H? ”, and here it is determined whether the timing pulse T of the timing pulse 43 has risen from the low level (L) to the high level (H), and for example, “N
When it is judged as “O”, judgment step S of “H→L?”
Move to IG. Then, the three calculation units determine that the timing pulse TP is at a high level (H) in this judgment step SIO.
), it is determined whether or not it has fallen to a low level (L), and when it is determined that, for example, rNOJ, the process returns to the determination step S9.

Here, the timing pulse T of the timing counter 43
, rises from low level (L) to high level (H), calculation unit 39 determines whether rL-H? " is determined as "YESJ" in the judgment step S9, and the output step S1 of "preset pulse width data to the 1st phase and 3rd Aikawa counter" is performed.
1, and the first and third phases are set to 0 counter 45. and 4
5. The pulse width data rmJ of the first phase and the third phase are preset.

As a result, as shown in FIG. 7(c), the first phase counter 45. is preset with numerical data rmJ and counts down, and outputs a high-level (H) PWM signal Pl during this down-count. The same applies to the third phase counter 45), which outputs a high level (H) PWM signal P during down-counting. After that, first phase and third phase counters 451 and 45. When it finishes counting down, its PWM signal and 1P.

output is stopped. Note that the three calculation units are in the processing step S.
, the process returns to input step S of "pulse train reading". Also, the timing pulse TP of the timing counter 43 changes from high level (H) to low level rLJ.
When the voltage falls, the calculation unit 39 performs a judgment step S of "H→L?". Then, the output step SI2 is "YESJ" and "preset pulse width data to the counters for the second and fourth phases". Here, the second and fourth phase counters 452 and 454 Preset the phase pulse width data rmJ. As a result, Figure 7 (
As shown in d), the second phase counter 452 is preset with numerical data rmJ and counts down, and also outputs a high level (H) PWM signal signal during this down counting. The same applies to the fourth phase counter 454, and during down-counting, the PWM is at a high level (H).
Signal signal type 4 power. After that, when the second and fourth phase counters 452 and 454 finish counting down,
The output of the PWM signal and 2P4 is stopped. still,
After the calculation unit 39 passes through processing steps S and 2, it returns to the manual step S3 of "reading a pulse train."

The PWM signals P to P4 in this third embodiment are given to the excitation period control circuit 35 in FIG. be able to.

The three-phase variable reluctance motor 15' in the second embodiment can also be controlled in the same manner as in the third embodiment using a microcomputer as a control means.

In addition, the present invention is not limited only to the embodiments described above and shown in the drawings, and may be modified as appropriate without departing from the gist, for example, the motor may be applied not only to a variable reluctance morph but also to a stepping motor. Of course, it can be carried out as well.

[Effects of the Invention] As explained above, the motor drive device of the present invention has a period in which a plurality of phase motor coils are excited in two phases, and performs PWM.
Even if the smoothing capacitor of the DC power supply circuit is controlled, the ripple of the power supply current can be reduced, and therefore the heat loss of the power supply line can be reduced, and the heat generation of the smoothing capacitor of the DC power supply circuit can be reduced. This has the excellent effect of preventing shortening of the life of the capacitor.

[Brief explanation of the drawing]

1 to 3 show the first embodiment of the present invention, and the first embodiment
2 is an excitation period signal waveform diagram for explaining the operation, FIG. 3 is a signal waveform diagram of each part for explaining the operation, and FIGS. 4 and 5 are diagrams of the present invention. 1 and 2 showing the second embodiment, and FIGS. 6 to 8 show the third embodiment of the present invention, and FIG. 6 is the electrical configuration of the main part. 7 are time charts for explaining the action, FIG. 8 is a flowchart for explaining the action, and FIGS. 9, 10, and 11 are conventional examples. and a diagram equivalent to Figure 3. In the drawing, 11 is a DC power supply circuit, 12 and 13 are power lines, 14 is a smoothing capacitor, 15 and 15' are variable reluctance motors (motors), and 161 to 164 are first
Phase to fourth phase motor coils, 181 to 184 and 1
9+ to 194 are transistors, 20 is a drive circuit, 31
．． 314 to 314 are PWM circuits, 32 is a first fundamental wave generation circuit, 33 is a second fundamental wave generation circuit, 34 and 34' are control means, 35 is an excitation period control circuit, 36 is an excitation period determination circuit, and 37 is a A selection circuit, 38 is a microcomputer (
3 is a calculation section, and 44 is a PWM signal signal section.

Claims (1)

[Claims] In a motor drive device that performs PWM control on a plurality of phase motor coils that are excited to have one- and two-phase excitation periods, the energization period of each phase motor coil is controlled by PWM control during the two-phase excitation period. A motor drive device characterized in that a control means is provided for controlling the time difference so that these are in a mismatched state.