JPH082191B2 - Motor drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit for a DC brushless motor used in, for example, a video tape recorder (VTR).

[Background of the Invention]

For example, a flat permanent magnet having a plurality of magnetic poles magnetized in the circumferential direction is used as a rotor, and the change in the magnetic field direction due to the rotation of the rotor is detected to switch the current flowing through the armature coil to generate a torque. A so-called DC brushless motor that is obtained is used as a drive motor for a VTR or the like. In recent years, devices such as portable VTRs have become smaller and smaller.
Along with the weight reduction, there is a demand for smaller and lighter motors of this type.

FIG. 1 is a circuit diagram showing a conventional example of a motor drive circuit for a three-phase DC brushless motor, where 1 is a rotor of the three-phase DC brushless motor, and 2, 3 and 4 are stator coils of the three-phase DC brushless motor. , 5,6,7,8,9,10 are transistors, 11 is a DC voltage source, 12 is a rotor rotational position detection circuit, and 13 is a switching control circuit.

FIG. 2 is an operation explanatory view of a three-phase DC brushless motor, in which FIG. 2A is a development view of a rotor, FIG. 2B is a magnetic flux distribution diagram by magnetic poles of the rotor, and FIGS. ),
(E) and (f) are explanatory views showing the relative positional relationship between the rotor and the stator coil over time, the parts corresponding to those in FIG. , The figure (b)
As shown in FIG.
As is well known, the direction of the drive current flowing through the stator coil in (f) is represented by-mark and x-mark.

FIG. 3 is a characteristic diagram showing the relationship between the drive current and torque for each stator coil. FIGS. 3B and 3C show the stator coil 2 of FIG. , (E) show the same for the stator coil 3, and FIGS. 6 (f) and (g) show the same for the stator coil 4. FIG. 7 (a) shows the change over time in the magnetic flux density due to the magnetic poles of the rotor. Further, FIG. 6H shows the change over time in the total torque generated in the rotor.

In addition, t ₁ , t ₂ , t ₃ , t _{4 in} FIG. ₃ are stator coils 2, 3, 4,
Shows the time when the rotor 1 is in the relative position with respect to the rotor shown in FIGS. 2 (c), (d), (e), and (f), respectively, and FIG. 3 (a) shows the stator coil by the rotation of the rotor 1. 2 shows the change over time in the magnetic flux density φ _{0 received} by the stator coil 3,
The changes over time in the magnetic flux density of 4 are delayed by 120 ° and 240 ° in electrical angle, respectively. Further, in FIG. 2, for convenience of explanation, the rotor 1'is fixed and the stator coils 2, 3, 4
Are shown to be rotating. The stator coil
The magnetic flux density received by 2,3,4 is actually the portion where the drive current that causes torque in the rotor 1'flows (that is, in each of the stator coils 2, 3 in FIGS. , 4, the sign of the direction of the current, the vertical part of the paper surface marked with ×)
The magnetic flux density that is received by.

The operation of the motor drive circuit will be described below with reference to FIGS.

Now, at time t ₁ , when the stator coils 2, 3 and 4 are located at the positions shown in FIG. 2 (c), the switching control circuit 13 detects the transistor 7 based on the signal from the rotor rotation detection circuit 12. , 9 are turned on and the transistors 5, 6, 8 and 10 are turned off. For this reason, constant drive currents I ₂ and I ₃ flow in the stator coils ₂ and _{3 in the} direction shown in FIG.
Drive current does not flow into the.

Accordingly, the torque T ₂ which is proportional to the product of the magnetic flux density phi ₁ of the driving current I ₂ and the rotor 1 of the stator coil 2 is generated in the rotor 1 and the drive current I ₃ of the stator coil 3 and the magnetic flux of the rotor 1 Torque T ₃ proportional to the density φ ₁ is generated in the rotor 1, and the rotor 1 rotates leftward in FIG. Since the magnetic flux density phi ₁ according to the rotor 1 in which forms a distribution of sinusoidal, the rotation of the rotor 1, the torque T ₂ by the driving current I ₂ of the stator coil 2 is gradually increased, the drive current of the stator coil 3 I ₃ torque T ₃ by decreases gradually.

Rotor 1 rotates 60 ° in electrical angle, stator coils 2,3,4
2 reaches the position shown in FIG. 2 (d) and the torque T ₂ becomes maximum at time t ₂ , the switching control circuit 13 turns on the transistor 8 that was off and turns off the transistor 9 that was on. . To this end, the stator coils 2 and 4 have a structure shown in FIG.
The constant drive currents I ₂ and I ₄ flow in the direction shown by, and the drive current stops flowing in the stator coil 3.

Accordingly, the torque T ₄ generated in the rotor 1 and magnetic flux density phi ₁ of the driving current I ₄ and the rotor 1 of the stator coil 4, a rotor 1 Aimatsu the torque T ₂ are rotated further in Figure 2 left. Times of Day
In the rotation of the rotor 1 after t ₂ , the torque T ₂ gradually decreases,
The torque T ₂ gradually increases.

Rotor 1 rotates 60 ° in electrical angle, stator coils 2,3,4
2 reaches the position shown in FIG. 2 (e) and the torque T ₄ becomes maximum at time t ₃ , the switching control circuit 13 turns on the transistor 6 that was off and turns off the transistor 7 that was on. . For this, the energization of the stator coil 2 is interrupted, the second view driving in the direction indicated in (e) current I _3, I ₄ flows in the stator coils 3, 4, Yotsute to the drive current I ₃ Torque T ₃ is generated in the rotor 1. The rotor 1 rotates due to the torques T ₃ and T _4, and the torque T ₃ gradually increases and the torque T ₄ gradually decreases with this rotation.

Rotor 1 rotates 60 ° in electrical angle, stator coils 2,3,4
2 reaches the position shown in FIG. 2 (f) and the torque T ₃ becomes maximum at time t ₄ , the switching control circuit 13 turns on the transistor 10 that was off and turns off the transistor 8 that was on. . For this reason, the energization of the stator coil 4 is cut off and the driving current I is applied to the stator coils 2 and 3 in the direction shown in FIG. 2 (f).
₂ and I ₃ flow, and torque is applied to the rotor 1 by this drive current I ₂ .
T ₂ occurs. The rotor 1 is rotated by the torques T ₂ and T ₃ ,
With this rotation, the torque T ₂ gradually increases and the torque T ₃ gradually decreases.

In this way, the transistors 5 to 10 are controlled to be turned on and off to set the energization period of the stator coils 2, 3 and 4 and the direction of the drive current so that the torque for rotating the rotor 1 in a certain direction is generated. It

In this way, the torques T ₁ , T ₂ , T ₃ change depending on the positions where the armature coils 2, 3, 4 and the magnetic poles of the rotor 1 face each other, so the total torque T ₀ (obtained in the rotor 1 T ₀ ( T ₀ = T ₁ + T ₂ + T ₃ )
Is not always constant and includes torque ripples as shown in FIG. 3 (h). For this torque ripple,
The rotor 1 does not rotate at a constant speed.

Conventionally, in order to remove this torque ripple, an attempt was made to intermittently rotate the rotor 1 at a time interval shorter than the cycle of the torque ripple, but it was not possible to rotate the rotor 1 at a constant speed sufficiently. Further, although the rotor 1 has been increased in weight and the uneven rotation has been eliminated by providing a flywheel or the like, with the recent reduction in size and weight of motors, such means cannot be used.

[Object of the Invention]

An object of the present invention is to provide a motor drive circuit capable of suppressing the occurrence of torque ripple and rotating a motor at an extremely constant speed, except for the above-mentioned drawbacks of the prior art.

[Outline of Invention]

To achieve this object, the present invention detects a signal representing a torque ripple from a back electromotive force induced in each stator coil, increases or decreases the current supplied to each stator coil by the signal, and increases the torque ripple. The feature is that it is designed to suppress.

Example of Invention

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

FIG. 4 is a block diagram showing a first embodiment of the motor drive circuit according to the present invention, in which 15, 16, 17 are transistors and 18
Is a current source that can change the output current, 19 and 20 are differential amplifiers, 2
1 is a correction signal generating circuit, 22 is a current detector, 23 is a constant voltage source, 24 is a wave detector, and 25 is a control signal input terminal for setting the rotation speed of the rotor. Are given the same symbols. Although not shown, the base terminals of the transistors 5, 6, 7, 15, 16, and 17 are connected to a switching control circuit such as the switching control circuit 13 shown in FIG.
These transistors are turned on / off in synchronization with the switching position of the magnetic field direction as the rotor rotates. In this embodiment, the transistors 5, 6 and 7 are driven to saturate to control ON / OFF, and the transistors 8, 9 and 10 are driven to saturate to operate as a current source.

 Next, the operation of this embodiment will be described.

A switching control circuit (not shown) turns on / off the transistors 5 to 10 and the transistors 15 to 17 in a predetermined order to supply current to the stator coils 2, 3 and 4 to rotate the rotor.

When the rotor rotates, a counter electromotive force is generated in the stator coils 2, 3 and 4 according to the change in the magnetic flux from the rotor that they receive. These back electromotive forces correspond very well to the torque produced in the rotor by each stator coil 2, 3, 4. Here, if the transistors 5, 6 and 7 operate in the non-saturated region, as shown in FIG. 5, a substantially sinusoidal back electromotive force e ₁ shown by a solid line is applied to one end x of the stator coil 2. Similarly, a substantially sinusoidal counter electromotive force e ₂ indicated by a broken line and a substantially sinusoidal counter electromotive force e ₃ indicated by a one-dot chain line are generated at the ends y and z of the stator coils 3 and 4, respectively.

However, in this embodiment, the transistors 5, 6, 7 operate in the saturation region, and the transistors 8, 9, 10 are driven in a non-saturation state,
Moreover, since the other ends of the stator coils 2, 3 and 4 are connected to each other, assuming that the transistor 7 is on now, during this period τ ₁ , the counter electromotive force generated at one end x of the stator coil 2 is generated. The electric power e ₁ is fixed to the power supply voltage E ₀ of the DC voltage source 11 as shown by the solid line in FIG. This is the fifth
Since the counter electromotive force e ₁ shown in the figure is raised to the power supply voltage E ₀ during the period τ ₁ , the counter electromotive forces e ₂ and e ₃ generated at the ends y and z of the stator coils 3 and 4 are also caused by this. , The power supply voltage E ₀ and the counter electromotive force e ₁ shown in FIG. 5 are raised.

Similarly, when the transistor 6 is turned on and the counter electromotive force e ₂ generated at one end y of the stator coil 3 is fixed to the power source voltage E ₀ , the counter electromotive force generated at one end x, z of the stator coils 2 and 4 is generated. Power e ₁ , e
₃ is pulled up, and when the transistor 5 is turned on and the counter electromotive force e ₃ generated at one end z of the stator coil 4 is fixed at the power supply voltage E ₀ , the reverse electromotive force e ₃ generated at one end x, y of the stator coils 2 and 3 is reversed. Electromotive force
e ₁ and e ₂ are raised.

Therefore, the maximum value of each back electromotive force e ₁ , e ₂ , e ₃ generated at one end x, y, z of the stator coils 2, 3, 4 is the power source as shown in FIG. 6 (a). The waveform is equal to the voltage E ₀ and has two minimum values between two maximum values.

These back electromotive forces e ₁ , e ₂ , e ₃ are supplied to the detector 24. The detector 24 sequentially detects the lowest level of the back electromotive forces e ₁ , e ₂ , e ₃ and outputs _a ripple-shaped detection voltage e _a shown in FIG. 6 (b). This detected voltage e _a is the combined torque generated in the rotor 1 (Fig. 1) shown in Fig. 3 (h).
It is in the opposite phase to the torque ripple of T ₀ .

The detector 24 sequentially detects the highest level and the lowest level of the back electromotive forces e ₁ , e ₂ , and e ₃ , and further takes the difference between the detected back electromotive forces. by construction, even if non-saturation operation of transistor 5, 6, 7, a counter electromotive force e _1, e _2, e ₃ from the detection output voltage e _a as shown in FIG. 6 (b) shown in FIG. 5 Obtainable.

This detection output voltage e _a is supplied to the variable gain amplifier 21. The variable gain amplifier 21 further includes a current detector 22
Reference voltage from the voltage e _s and a constant voltage source 23 from is applied. The current detector 22 is composed of a resistor having a minute resistance value, detects the drive current I _X which is the sum of the drive currents flowing in the stator coils 2, 3 and 4, and outputs a voltage e _s proportional to this current I _X. appear. The stator coils 2, 3, 4 have internal resistance, and in practice, the back electromotive force e ₁ , e ₂ , e generated at one end x, y, z of each stator coil 2, 3, 4 is _The voltage drop due to the drive current of these internal resistances is included in 3 and, therefore, the detection output voltage e _a also includes this voltage drop. By applying these voltages, the variable gain amplifier 21 removes the voltage drop due to the internal resistance of the stator coils 2, 3, 4 from the detection output voltage e _a , and amplifies the voltage with a predetermined amplification factor. Correction voltage e _T for correcting the above torque ripple
Occurs.

This correction voltage e _T is supplied to the differential amplifier 20, and the input terminal
It is combined with a control voltage e _c which defines the rotational speed of the rotor 1 from 25. The output voltage e _M of the differential amplifier 20 is supplied to the differential amplifier 19, and the voltage e _s from the current detector 22 is combined. The output voltage e _I of the differential amplifier 19 becomes the control voltage of the current source 18,
The current of the current source 18 changes according to the output voltage e _I.

On the other hand, the transistors 15, 16 and 17 are on / off controlled by the switching control circuit 13 shown in FIG. 1 similarly to the transistors 8, 9 and 10 shown in FIG.
Alternatively, when 17 is turned on, a current is supplied as a base current from the current source 18 to the base of the transistor 8, 9 or 10 connected to the collector of the turned on transistor.

Now, when the transistors 7 and 16 are turned on, a base current flows from the current source 18 to the transistor 9, and a collector current obtained by multiplying the base current by a current amplification factor h _FE is used as a drive current from the transistor 7 to the stator coils 2 and 3. Flow to. Similarly, when the transistors 15 and 17 are on,
A base current is supplied from the current source 18 to the transistor 8 or 10, and a collector current corresponding to this base current flows as a drive current through a predetermined stator coil.

The differential amplifier 19 is configured so that the gain is sufficiently high, and the voltage drop e _s generated in the current detector 22 is reduced by the differential amplifier 20.
Feedback control is performed so that the output voltage becomes equal to the output voltage e _M. Due to such feedback control, variations in h _FE of the transistors 8, 9 and 10 are absorbed.

With the above configuration, the collector currents of the transistors 8, 9 and 10 change according to the correction voltage e _T output by the variable gain amplifier 21. In this case, the correction voltage e _T has a phase opposite to that of the torque ripple (FIG. 3 (h)), so that the collector currents of the transistors 8, 9, 10 (that is, the stator coil 2,
(Driving currents flowing in 3 and 4) are shown in series on the same time axis, as shown in FIG. 7 (a). The driving current I _X thus represented is equal to each stator coil 2 Ripple having a phase opposite to that of the torque ripple T ₀ (FIG. 7 (b)) that occurs when a constant drive current is applied to the drive current
Due to the interaction between I _X and the magnetic flux density φ ₀ (FIG. 3 (a)) of the rotor 1, a constant torque T _X is generated in the rotor 1 as shown in FIG. 7 (b). Therefore, rotor 1
Will rotate smoothly.

In this embodiment, as described above, the counter electromotive forces e ₁ , e
₂ and e ₃ are caused by changes in the magnetic flux density received by the stator coils 2, 3 and 4, and correspond very well to the torque generated in the rotor, so that almost accurate torque ripple correction can be realized. That is, how the magnetic flux density received by each stator coil 2, 3, 4 changes, and, for example, there is a relative difference in the magnetic flux density received by the stator coils 2, 3, 4 and the torque ripple generated in the rotor is irregular. Even if it is, the back electromotive force e ₁ , e ₂ ,
Since e ₃ changes according to it, such torque ripple can be sufficiently suppressed.

In FIG. 4, the control voltage e _c from the input terminal 25
When the control voltage e _c is increased or decreased, the voltage drop e _s of the current detector 22 becomes equal to the output voltage e _M of the differential amplifier 20 when the control voltage e _c is increased or decreased. The current source 18 is controlled so that the stator coils 2, 3,
The current flowing through 4 increases or decreases and the rotor speed changes.

FIG. 8 is a circuit diagram showing a specific example of FIG. 4, and the portions corresponding to FIG. 4 are designated by the same reference numerals.

In FIG. 8, the detector 24 is composed of diodes 26, 27 and 28, and the current detector 22 is composed of a resistor 29 having a minute resistance value.

The variable gain amplifier 21 includes a variable gain amplification section including transistors 30, 31, 32, 33, 34, a resistor 35 and a constant voltage source 36, and a current adjustment including transistors 37, 38, 39, a resistor 40 and a constant current source 41. And a detection output voltage compensating unit including a transistor 42 and a resistor 43.

The differential amplifier 20 includes transistors 44, 45, 46, 47, 48 and resistors.
It is composed of 49 and a constant current source 50.

The differential amplifier 19 is composed of transistors 51, 52, 53, 54, 55, 56 and a constant current source 57.

Current source 18 consists of transistor 58, transistor 56
Together with this, it constitutes a current mirror circuit. A current proportional to the output current of the differential amplifier 19 (collector current of the transistor 56) is obtained from the transistor 58.

Incidentally, 59 and 60 are constant voltage power supplies. 61, 62, 63 are internal resistances of the stator coils 2, 3, 4 respectively.

 Next, the operation of this specific example will be described.

By the counter electromotive force of the stator coils 2, 3 and 4, each coil 2,
The voltage generated at one end x, y, z of 3,4 is the diode of the detector 24.
Detected by 26, 27 and 28, a detected output voltage e _a having ripples as shown in FIG. 6 (b) is obtained. However, this detected output voltage e _a is the internal resistance 61,6 of the stator coils 2, 3, 4
It includes the voltage drop due to 2,63.

The total current _IX flowing through the stator coils 2, 3, 4 is detected as the voltage across the resistor 29.

In the variable gain amplifier 21, the transistor 39 has its collector terminal and base terminal connected to each other and is diode-connected, and its collector terminal has a constant voltage source 59 via a current source 41.
Further, its emitter terminal is connected to the resistor 29 of the current detector 22. The transistor 38 forms an emitter-grounded amplifier together with the emitter resistor 40, the base terminal of which is connected to the base of the transistor 39 and the collector terminal of which is connected to the collector terminal of a diode-connected pnp transistor. The emitter terminal of the transistor 37 is connected to the constant voltage source 59, and the base terminal is connected to the base terminal of the pnp transistor 42. Therefore, the transistors 37 and 42 form a current mirror circuit.
The emitter terminal of the transistor 42 is connected to the constant voltage source 59, and the collector terminal is connected to the detector 24 via the resistor 43.

The current of the current source 41 is small enough to be ignored as compared with the drive current _IX flowing through the resistor 29, and the resistance value of the resistor 29 is
R ₂₉ , the resistance value of the resistor 40 is R ₄₀ , the resistance value of the resistor 43 is R ₄₃ , and the resistance values of the internal resistances 61, 62, 63 of the stator coils 2, 3, 4 are equal to these resistances. When the value is r, these resistance values are By setting so as to satisfy the above condition, a voltage drop equal to the voltage drop generated in the internal resistances 61, 62, 63 of the stator coils 2, 3, 4 occurs in the resistor 43. That is, since the current of the current source 41 is negligible, emitter voltage of the transistor 39 is equal to the voltage drop across R ₂₉ · I _X of the resistor 29 by the driving current I _X, was but connexion, emitter voltage of the transistor 38 also R ₂₉ · Equal to I _X. As a result, the current flowing in the emitter resistance 40 of the transistor 38, that is, the collector current of the transistors 38 and 37 is Becomes Since the transistors 37, 42 form a current mirror circuit, the collector currents of the transistors 37, 42 are equal, and therefore the voltage drop of the resistor 43 caused by the collector current of the transistor 42 flowing is: From the above equation (1), this voltage drop becomes 2r · _IX . The drive current _IX flowing through the resistor 29 of the current detector 22 is generated by turning on one of the transistors 5, 6, 7
When the base current is supplied to any one of 8, 9 and 10, any two of the stator coils 2, 3 and 4 become in series,
The drive current flowing through these two stator coils,
As described above, the counter electromotive forces e ₁ , e ₂ , e ₃ generated at one end x, y or z of the stator coils 2, 3, 4 are the drive currents generated in the internal resistance of these two stator coils. Voltage drop due to I _X 2r
-Includes I _X.

The voltage drop 2r ・_IX generated in the resistor 43 is the voltage drop 2r due to the internal resistors 61, 62, 63 included in the detection output voltage e _a of the detector 24.
・ Offset I _X. As a result, in the collector of the transistor 42, the voltage corresponding to only the back electromotive force generated in the stator coils 2, 3, 4 is obtained by removing the voltage drop due to the internal resistors 61, 62, 63 from the detection output voltage e _a. Is obtained.

The collector voltage of transistor 42 is npn transistor 3
It is supplied to the base of the npn transistor 30 which forms a differential amplifier together with 1, and the base of the transistor 31 is
The voltage of the constant voltage source 23 is applied. The emitter terminals of the transistors 30 and 31 are both connected to the collector terminal of the pnp transistor 34. The transistor 34 forms a constant current source, the base terminal of which is connected to the base terminal of the transistor 37, and forms a current mirror circuit with the transistor 37. The collector terminal of the transistor 30 is
The collector terminal of the npn transistor 32 and the collector terminal of the transistor 31 are connected to the collector terminal of the diode-connected npn transistor 33.
Base terminals 32 and 33 are connected to each other to form a current mirror circuit. Further, a load resistor 35 and a constant voltage source 36 are connected in series between the collector of the transistor 32 and the emitter.

In such a configuration, the difference voltage between the voltage applied to the base of the transistor 30 and the voltage of the constant voltage source 23 applied to the base of the transistor 31 is amplified by the gain determined by the load resistor 35, and the correction voltage e _T Is supplied to the differential amplifier 20. At this time, the collector current of the transistor 34 is equal to the collector current of the transistor 37, and as shown in the equation (2), the voltage drop that occurs in the resistor 29 of the current detector 22,
Therefore, it is proportional to the drive current I _X.

Therefore, the gain of the variable gain amplifier 21 depends on the drive current I _X
The gain is controlled accordingly. This gain control is based on the drive current
Even if I _X increases or decreases, the rotor rotates with a constant torque. That is, when the drive current I _X changes,
Torque generated in the rotor, Ritsupuru also changes, but in constant gain due to the resistance 35 of the constant resistance value, can not be corrected this changing Torukuritsupuru correction voltage e _T, for this, the driving current I _X The gain is changed accordingly, and the correction voltage e _T is adjusted so that the torque ripple can be removed.

The constant voltage source 36 is the transistor 45 of the differential amplifier 20.
The operating point of is matched with the operating point of the transistor 44.

The obtained correction voltage e _T is applied to the base of one pnp transistor 45 forming a differential pair of the differential amplifier 20, and the other p
The control voltage e _c is applied to the base of the np transistor 44 from the input terminal 25. The emitter terminals of the transistors 44 and 45 are both connected to the constant voltage source 60 via the constant current source 50,
The collector terminal of the transistor 44 is connected to the collector terminal of the diode-connected npn transistor 46, the collector terminal of the transistor 45 is connected to the collector terminal of the npn transistor 47, and the base terminals of the transistors 46 and 47 are connected to each other. Connected to each other to form a current mirror circuit. Further, the collector terminal of the transistor 47 is connected to the base terminal of a diode-connected npn transistor 48, and the emitter terminal of the transistor 48 is connected to a load resistor 49.

Therefore, the control voltage e _c applied to the base of the transistor 44 and the correction voltage e _T applied to the base of the transistor 45.
A combined voltage of and is generated in the load resistance 49 and is supplied to the differential amplifier 19 as the output voltage e _M.

In the differential amplifier 19, the output voltage e _M of the differential amplifier 20 is applied to the bases of the pair of pnp transistors 51 of the differential pair, and the current detector 22 is applied to the base of the other pnp transistor 52.
The voltage e _s generated in the resistor 29 of is applied. The emitter terminals of the transistors 51 and 52 are both connected to the constant voltage source 60 via the constant current source 57, the collector terminal of the transistor 51 is the diode-connected npn transistor 53 collector terminal, and the transistor 52 collector terminal is npn The collector terminals of the transistor 54 are connected to each other, and the base terminals of the transistors 53 and 54 are connected to each other to form a current mirror circuit. In addition, the transistor 54
The base terminal of the npn transistor 55 is connected to the collector terminal of, and the collector terminal of this transistor 55 is a diode-connected type whose emitter terminal is connected to the constant voltage source 60.
It is connected to the collector terminal of the pnp transistor 56.

In such a configuration, the difference voltage between the voltages e _M and e _s applied to the respective bases of the transistors 51 and 52 is the transistor 55.
Is applied to the base of the transistor 55, and a collector current corresponding to the base voltage flows through the transistor 55.

The current source 18 comprises a pnp transistor 58, the base terminal of which is connected to the base terminal of the transistor 56, forming a current mirror circuit with the transistor 56. The emitter terminal of the transistor 58 is connected to the constant voltage source 60, and the collector terminal is connected to the emitter terminals of the transistors 15, 16 and 17.

Therefore, the collector current of the transistor 58 is equal to the collector current of the transistor 56, that is, the collector current of the transistor 55. Therefore, the collector current of the transistor 58 changes according to the difference voltage between the output power e _M of the differential amplifier 20 supplied to the differential amplifier 19 and the voltage e _s generated in the resistor 29 of the current detector 22. .

The current of current source 18 is
Alternatively, it is supplied through 17 to the base of the transistor 8, 9 or 10. Transistor 8, 9 or 10 has a collector current that is h _FE times its base current, and this collector current flows to two of stator coils 2, 3 and 4 as drive current I _X , and It flows through the resistor 29 of the current detector 22.

Incidentally, when the h _FE of the transistor 8, 9 are different, since the collector current generated in the transistor 8,9,10 different, supply each switched base current to the transistor 8, 9, 10, the drive current I _X also changes. At the same time, the voltage e _s generated in the resistor 29 of the current detector 22 also changes, so the base voltage of the transistor 55 of the differential amplifier 19 also changes, its collector current also changes, and the output current of the current source 18 also changes. . As a result, as the output voltage e _M of the driving current I _X be varied across resistor 29 voltage e _s and the differential amplifier 20 become equal, the driving current I _X is set. Therefore, even if there are variations in h _FE among the transistors 8, 9 and 10, the drive current I _X is kept constant.

As described above, in this embodiment, when controlling the torque ripple generated in the rotor by the drive current, the counter electromotive force generated in the stator coil is detected to obtain the correction signal, and the drive current is changed by the correction signal. It was made to change. When obtaining such a correction signal, in this embodiment, it is possible to eliminate the effects of the internal resistance of the stator coil, the undesired increase and decrease of the drive current, the variation of the current amplification factor h _FE of the transistor that operates in an unsaturated state, Therefore, the obtained correction signal corresponds to only the above-mentioned counter electromotive force. Since the counter electromotive force and the torque ripple generated in the rotor are both generated by the magnetic flux generated by the rotor, the two correspond very well in terms of period, waveform, phase, etc. Therefore, the torque ripple generated in the rotor can be almost completely removed by the correction signal, and the rotation of the motor can be made very smooth.

Next, a second embodiment of the present invention for a single-phase DC brushless motor will be described with reference to FIGS.

9A and 9B are explanatory views of the rotating operation of the single-phase DC brushless motor. FIG. 9A is a development view of the rotor, and FIG.
Is a distribution diagram of magnetic flux density due to the magnetic poles of the rotor.
(D) is an explanatory view showing the relative positional relationship of the stator coil with respect to the rotor over time, and is shown respectively corresponding to FIG. 2.

FIG. 10 is a characteristic diagram of a single-phase DC brushless motor using a conventional motor drive circuit.

FIG. 11 is a block diagram showing this embodiment.
Reference numeral 6 is a stator coil, and 67, 68, 69, 70, 71 are switching control circuits, and the parts corresponding to those in FIG.
Further, FIG. 12 is a waveform diagram showing the drive current and the torque in this embodiment.

In the single-phase DC brushless motor, the rotor 1'is
As shown in FIG. 9 (a), N poles and S poles in a size region are alternately arranged, and N poles and S poles in a small region are arranged at every other boundary of these magnetic poles. . Fig. 9 (a)
Then, when the arrangement order of the magnetic poles is viewed from left to right in the drawing, there is an N pole of a small area and then an S pole of a small area between the S pole of the large area and the N pole of the next large area. . For this reason, the magnetic flux distribution due to the rotor 1'is, as shown in FIG. 9 (b), the magnetic flux reversal region at the boundary between the S pole of the large region and the N pole of the next large region, and Magnetic flux distortion occurs due to the N pole and the S pole.

The stator coils 65 and 66 are arranged coaxially with the rotor 1 ′ at an angular interval of 180 °, but when the electrical angle with respect to the rotor 1 ′ is taken as a reference, these stator coils 65 and 66 have an electrical angle of 180 °. 9 (c) and 9 (d), the stator coils 65, 66 are shown in close proximity while maintaining the mutual electrical angular spacing for ease of explanation.

In FIG. 9, the rotor 1 ′ is assumed to rotate from right to left on the paper surface. However, for convenience of explanation, the stator coils 65 and 66 are rotated from left to right on the paper surface as in FIG. 2. It shall be moved toward.

When the stator coil 65 moves in this way, a portion that produces a torque in the rotor 1'by energizing this stator coil (that is, there is a portion perpendicular to the paper surface,
Hereinafter, the magnetic flux received by p ₁ and p ₂ will be referred to as the torque generating portion. The magnetic flux received by the torque generating portion p ₁ is shown in FIG. 10 (a).
Changes as a chain line phi ₁₁ of the magnetic flux which the torque generating moiety p ₂ receives varies as also the two-dot chain line phi _12. Therefore, the magnetic flux that the stator coil 65 receives to generate torque in the rotor 1'is the sum of these magnetic fluxes φ ₁ and φ ₂ , and changes as shown by the solid line φ _{1 in} FIG. 10 (a). To do.

On the other hand, since the stator coil 66 has an electrical angle of 180 ° with respect to the stator coil 65, the magnetic flux similarly received by the stator coil 66 is as shown in FIG. 10 (b). The magnetic flux φ ₁ received by the coil 65 is 180 ° phase-shifted φ
It becomes ₂ .

On the other hand, the stator coils 65 and 66 are alternately energized each time they move 180 ° in electrical angle. In the conventional motor drive circuit, the drive current flowing through the stator coils 65 and 66 has a constant magnitude. FIG. 10 (c) shows the drive current flowing through the stator coil 65, and FIG. 10 (d) shows the drive current flowing through the stator coil 66.

Therefore, at time t ₁ when the stator coils 65 and 66 are at the positions shown in FIG. 9C, a constant drive current I _{0 is} applied to the stator coil 65.
When the stator coil 66 is de-energized, a torque proportional to the product of the drive current I ₀ and the magnetic flux φ ₁ is applied to the rotor 1 ′.
, The rotor 1'rotates, and the stator coil 6
5,66 move. Then, at time t when the stator coils 65 and 66 move 180 ° in electrical angle and reach the position shown in FIG. 9 (d).
_{At 2} , the stator coil 65 is de-energized and the stator coil 66
A constant drive current I ₀ is started to flow through. Then, a torque proportional to the product of the drive current I ₀ of the stator coil 66 and the magnetic flux φ ₂ is generated in the rotor 1 ′, and the rotor 1 ′ further rotates to move the stator coils 65 and 66 relatively.

In this way, by switching the energization every time the stator coils 65, 66 move 180 degrees in electrical angle, torque is continuously generated and the rotor 1'continues to rotate.

In this case, as is clear from FIGS. 10 (a) to 10 (d), during the energization period of the stator coils 65 and 66, the magnetic flux distortion is caused by the N pole and the S pole in the small area of the rotor 1 ', respectively. This is the period during which the generated magnetic flux is received. This is to generate the torque in the flat portion of the magnetic fluxes φ ₁ and φ ₂ by the rotor 1 ′, and as a result, the torque ▲ T ^′ ₀ ▼ generated in the rotor 1 ′ is shown in FIG. As shown in (e).

However, even if the N and S poles in a small area are provided in this way, the magnetic fluxes φ ₁ and φ ₂ received by the stator coils 65 and 66 are
As shown in FIGS. 10 (a) and 10 (b), since there is no flat portion and the drive current I ₀ flowing through the stator coils 65 and 66 is constant, the torque ▲ T generated in the rotor 1 ' ^′ ₀ ▼
Causes torque ripple as shown in FIG. 10 (e).

In this embodiment, the torque ripple of the single-phase DC brushless motor is removed.

In FIG. 11, each time the stator coils 65 and 66 move by an electrical angle of 180 °, the switching control circuit 71 alternately turns on and off the transistors 69 and 70 as described above. Now, when the transistor 69 is turned on, the transistor 70 is turned off, and the current from the current source 18 is supplied as the base current to the transistor 67 that operates in a non-saturated state. The base current h _FE (current amplification factor of the transistor 67) Double the driving current flows through the stator coil 65, the transistor 67, and the current detector 22.

When the stator coils 65 and 66 move by an electrical angle of 180 °, the transistor 69 is turned off and the transistor 70 is turned on, so that the current of the current source 18 is supplied to the transistor 68 which operates in a non-saturated state as a base current. Therefore, the drive current flows through the stator coil 66.

As the stator coils 65 and 66 move, a back electromotive force due to the magnetic flux φ ₁ (Fig. 10 (a)) is generated in the stator coil 65, and this back electromotive force changes similarly to this magnetic flux φ _1. To do. Similarly, in the stator coil 66, the magnetic flux φ ₂ (tenth
A counter electromotive force is generated according to the diagram (b), and the counter electromotive force changes similarly to the magnetic flux φ ₂ . Therefore, the stator coil
At one end R of 65, the counter electromotive force generated in the stator coil 65 is
A voltage ▲ e ^′ ₁ ▼ is generated by adding a voltage drop due to the internal resistance of the stator coil 65, and one end S of the stator coil 66 is generated.
Is a voltage ▲ e ^′ that is the counter electromotive force generated in the stator coil 66 plus a voltage drop due to the internal resistance of the stator coil 66.
₂ ▼ occurs.

These voltages ▲ e ^′ ₁ ▼, ▲ e ^′ ₂ ▼ are detected by the detector 24
Then, the detection is performed in the same manner as in the previous embodiment shown in FIG. 4 to obtain the detection output voltage ▲ e ^' _a ▼. In this case, Fig. 10 (a),
As is apparent from (b), there is a period when the counter electromotive force generated in the stator coil 65 having a waveform corresponding to the magnetic flux φ ₁ is lower than the counter electromotive force generated in the stator coil 66 having a waveform corresponding to the magnetic flux φ _2. The period during which the stator coil 65 is energized, and the period in which the high and low levels of the respective back electromotive forces are opposite, is the period during which the stator coil 66 is energized. Therefore, the component due to the back electromotive force included in the detected output voltage ▲ e ^' _a ▼ has a waveform corresponding to the torque ripple generated in the rotor.

The operations of the variable gain amplifier 21 and the differential amplifiers 20 and 19 described below are similar to those of the previous embodiment, and the output voltage of the differential amplifier 19
The current source 18 is controlled by e ^′ _I ▼, and the stator coil 6
Drive current ▲ I _^'X ▼ is flowing to 5,66, as shown in Figure 12 (a), varies depending on Torukuritsupuru occurring rotor, upon applying a constant drive current to the stator coils 65 and 66 In addition, as shown by the broken line in FIG. 12 (b), the torque ▲ T ^′ ₀ ▼ having a ripple was generated, but as shown by the solid line in FIG. 12 (b), the torque ripple was removed. constant torque ▲ T _^'X ▼ will be obtained.

Although the embodiments have been described above for the three-phase and single-phase DC brushless motors, it goes without saying that the present invention can be applied to DC brushless motors of any number of phases.

〔The invention's effect〕

As described above, according to the present invention, the drive current flowing in the stator coil can be changed so as to reliably cancel the change in the magnetic flux received by the stator coil. A torque that is proportional to the product of x and x can always be made constant, torque ripple can be sufficiently suppressed, and the rotation of the motor can be made smoother. It is possible to provide the motor drive circuit of.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional motor drive circuit, FIG. 2 is an operation explanatory diagram of a three-phase DC brushless motor, and FIG. 3 is a diagram showing the drive current and torque for each stator coil in FIG. FIG. 4 is a characteristic diagram showing the relationship, FIG. 4 is a block diagram showing the first embodiment of the motor drive circuit according to the present invention, FIG. 5 is a waveform diagram showing the counter electromotive force generated in each stator coil of FIG. 4, and FIG. FIG. 7 is a diagram for explaining the operation of the detector shown in FIG. 4, FIG. 7 is a characteristic diagram showing the relationship between drive current and torque shown in FIG. 4, and FIG. 8 is a circuit diagram showing one specific example of FIG. FIG. 9 is a diagram for explaining the operation of the single-phase DC brushless motor, FIG. 10 is a characteristic diagram showing the relationship between the drive current and torque of the single-phase DC motor by the conventional motor drive circuit, and FIG. 11 is the motor drive circuit according to the present invention. FIG. 12 is a block diagram showing the second embodiment of the present invention, and FIG. 12 is a characteristic diagram showing the relationship between the drive current and the torque. . 2,3,4 …… stator coil, 18 …… current source, 19,20 …… differential amplifier, 21 …… variable gain amplifier, 22 …… current detector, 24
...... Detector, 65,66 …… Stator coil.

Claims (1)

[Claims] 1. A motor drive circuit for switching and controlling drive currents to a plurality of stator coils in synchronism with rotation of a rotor, wherein a counter electromotive force is generated in the stator coils as the rotor rotates. Of the voltage generated by the first means, the second means for detecting a voltage drop occurring in the stator coil, and the voltage generated by the first means. Third means for correcting the voltage drop detected by the second detecting means to generate a correction signal having a waveform corresponding to the torque ripple generated in the rotor; and changing the drive current according to the correction signal. The motor drive circuit is configured so as to suppress the torque ripple generated in the rotor due to the fluctuation of the rotating magnetic flux with respect to the stator coil.