JPS6329519B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless motor drive circuit developed to reduce torque ripple and obtain large drive torque.

Conventionally, the drive circuit of a brushless motor that uses magnetic pole detection elements such as Hall elements to flow current to the stator windings is as shown in Figure 1, which uses magnetic pole detection elements H ₁ , H ₂ , H ₃ .
The generated voltage is controlled by a switch drive unit consisting of differential amplifiers G ₁ , G ₂ , G ₃ , diodes, and transistors.
It consists of a drive circuit that applies voltage to stator windings W ₁ , W ₂ , and W ₃ via C ₁ , C ₂ , and C ₃ . In this drive circuit, the current waveforms flowing through each winding are not aligned, and there are windings to which current is not supplied depending on the phase. As a result, torque ripple occurs, and there is a drawback that the torque ripple is large, for example, about 28%. Further, the above drive circuit has the disadvantage that sufficient starting torque cannot be obtained.

SUMMARY OF THE INVENTION In view of the above drawbacks, an object of the present invention is to provide a drive circuit for a brushless motor that reduces torque ripple and has a large drive torque.

A feature of the present invention is that a constant current source controlled by the rotation speed is provided in the drive circuit and one side contact of a switching part connected to each phase of the stator winding to switch connections. and a first current divider that distributes the current evenly to the two phases when the two phases are electrically connected by the switching section, and between the other side contact of the switching section and the constant current device. A second current divider is provided which receives current equally from the two phases when the two phases are electrically connected by the switching section.

The present invention will be explained below with reference to illustrated embodiments. Describing the principle configuration of the drive circuit in Fig. 2, the motor body includes a multi-pole magnetized rotor (not shown),
Star-connected three-phase stator windings W ₁ , W ₂ ,
W ₃ and magnetic pole detection elements H ₁ , H ₂ , H ₃ such as Hall elements provided corresponding to each phase of the winding. The magnetic pole detection elements are arranged at positions having a relationship of 2nπ, 2nπ+2/3π, and 2nπ+4/3π with respect to each other, where n is an arbitrary integer in electrical angle. The three-phase stator windings are arranged at positions corresponding to each magnetic pole detecting element so that a rotating magnetic field can be obtained by detecting the magnetic pole by the magnetic pole detecting element.

Next, the configuration of the drive circuit is the three-phase stator winding described above.
It is connected to W ₁ , W ₂ , W ₃ and switching parts S ₁ , S ₂ , S ₃ , and this switching part is connected to the above magnetic pole detection element.
Switch drive unit C ₁ connected to H ₁ , H ₂ , H ₃ ,
Corresponds to C ₂ and C ₃ respectively. The switching section is provided with an H side and an L side, and the H side or L side of the switching section is connected to a first current divider _B1 , and this first current divider _B1 is connected to a constant current device A. is connected to the power supply +VCC. The L side or H side of the above switching section is a second current divider.
_B2 , and the other side of the second current divider _B2 is grounded to the low potential side. The switching section is configured to perform a switch operation in which the magnetic pole detection element closes to the H side when it detects, for example, an N pole, and closes to the L side when it detects an S pole.

To explain the operation of the above drive circuit, since the magnetic pole detection elements H ₁ , H ₂ , and H ₃ are arranged sequentially shifted by 2/3π electrical angle, the multi-pole magnetized rotor Outputs a, b, and c of 1 are output and input to switch drive units C ₁ , C ₂ , and C ₃ .
In the waveforms a, b, and c above, the solid line and the dashed-dotted line indicate the difference in the sensitive poles. The output of the switch drive unit switches the switching units S ₁ , S ₂ , and S ₃ . The relationship between the magnetic pole detecting element and the switching section is as described above.When the magnetic pole detecting element detects the N pole, the switching section closes to the H side, and when it detects the S pole, it closes to the L side. Each of the electrical angles, such as d, e, and f, can be switched every 180 degrees. As for the switching state, since the magnetic pole detection elements are arranged to be shifted by 2/3π as described above, all three switching parts do not switch to the H side or the L side.

The relationship between the switching sections S ₁ , S ₂ , S ₃ and the first and second current distributors B ₁ and B ₂ is as follows. That is, when there are two switching sections switched to the H side as shown in FIG. 2, the current supply value _I0 of the constant current device A is transferred to the switching section _S2 via the first current distributor _B1 . , S ₃ respectively by supplying two currents of I ₀ /2. second current divider
B ₂ is the switching part S ₁ 1 which is switched to the L side
Since the current values flowing from the other two switching parts S ₂ and S ₃ are connected to only one switch, the current values I ₀ /2 and I
_0/2 , that is, the sum of the currents flowing in the two phases divided by the first current divider _B1 , which is the current _I0 . If only one switching section is switched to the H side, the first current divider
The current supply value I ₀ of the constant current device A flows through B ₁ as it is, and the second current divider B ₂ allows current to flow in increments of I ₀ /2 from the other two switching parts switched to the L side. It is affected by That is, since a back electromotive force is applied to each of the stator windings, the apparent impedance of each phase is different, so the current value of the sum of each winding is forcibly determined using the current dividers B ₁ and B ₂ . is controlled to the current supply value I ₀ in accordance with the polarity detected by the magnetic pole detection element.

As a result of the above, the windings W ₁ , W ₂ , W ₃ of each phase have a third
Step-like currents such as g, h, and i in Figure A will flow. Therefore, the torque waveform obtained in each phase
TW ₁ , TW ₂ , and TW ₃ are as shown in j, k, and l in Fig. 3 (b), and their total sum is as shown in m in Fig. 3 (b), and a large torque with little torque ripple is obtained.

FIG. 4A shows an embodiment of a drive circuit constructed according to the above principle, in which magnetic pole detection elements H ₁ , H ₂ , and H ₃ are connected to differential amplifiers G ₁ , G ₂ , and G _{3 ,} respectively. The output of the differential amplifier is connected to one end of each of two sets of diodes D ₁ to _{D 6} of switch drive units C ₁ , C ₂ , and C ₃ . Each of the two sets of diodes D ₁ to D ₆ is connected such that one side is on the high potential side and the other is on the low potential side. The other ends of each of the diodes _D1 to _D6 are connected to the bases of transistors _Tr11 , _Tr12 , _Tr13 , _Tr14 , _Tr15 , and _Tr16 . The collector of each transistor is the transistor of switching section S ₁ , S ₂ , S ₃
They are connected to the bases of Tr ₁ , Tr ₂ , Tr ₃ , Tr ₄ , Tr ₅ , and Tr ₆ , respectively. Each transistor is Tr ₁₁ , Tr ₁₃ ,
NPN type transistors are installed in Tr ₁₅ , Tr ₂ , Tr ₄ , and Tr ₆ ,
Transistors Tr ₁₂ , Tr ₁₄ , Tr ₁₆ , Tr ₁ , Tr ₃ , Tr ₅
PNP type transistors are used in

One end of the stator winding W ₁ is connected to the collectors of the transistors Tr ₁ and _{Tr 2} ;
One end of the stator winding W ₂ is connected to the collector of Tr ₄ ,
One end of the stator winding W ₃ is connected to the collectors of the transistors Tr ₅ and Tr ₆ , respectively, and the other ends of the stator windings are connected together to form a star connection. The emitters of the above transistors Tr ₁ , Tr ₃ and Tr ₅ are connected to the positive power supply +VCC, and the above transistors
The emitters of Tr ₂ , Tr ₄ , and Tr ₆ are connected to the emitter of another NPN type transistor Tr ₇ , and the base of the transistor Tr ₇ is connected to the control input signal V _IN such as the rotation speed.
connected to the terminal. A resistor _R1 is connected between the emitter of the transistor _Tr7 and the low potential side, and a resistor and a diode are connected between the collector and the positive power supply +VCC.
A series circuit of D ₇ and a resistor is connected. In addition, a PNP transistor is connected to the low potential side of diode _D7 .
The bases of Tr ₈ and Tr ₉ are connected and the transistor
The emitters of Tr ₈ and Tr ₉ are connected to the positive power supply +VCC via a resistor. A series circuit of a resistance diode _D8 is connected between the collector of the transistor _Tr9 and the low potential side, and the base of an NPN transistor _Tr10 is connected to the collector. A resistor is connected between the collector of the transistor Tr ₈ and the emitters of the transistors Tr ₁₂ , Tr ₁₄ and Tr ₁₆ , respectively.
R ₂ , R ₃ , and R ₄ are connected. transistor
The collector of Tr ₁₀ and the transistors Tr ₁₁ , Tr ₁₃ ,
Resistors R ₅ , R ₆ , and R ₇ are connected between the emitters of the transistor Tr ₁₅ , and a resistor is connected between the emitter of the transistor Tr ₁₀ and the low potential side. The constant current device A includes the transistors Tr ₈ , Tr ₉ , Tr ₁₀ and a diode.
It consists of D ₈ and the resistors connected to them.

FIG _. 4B is a _drive circuit _{diagram that is} exactly _{the same} as FIG.
It is composed of R ₅ , R ₆ , and R ₇ . The second current divider B ₂ includes the transistors Tr ₁₂ , Tr ₂ , Tr ₁₄ ,
It consists of Tr ₄ , Tr ₁₆ , Tr ₆ and resistors R ₂ , R ₃ , and R ₄ .

In FIG. 4 above, the switching parts S ₁ , S ₂ ,
When comparing S ₃ with FIGS. 2 and 3 d, e, and f, when transistors Tr ₁ , Tr ₃ , and Tr ₅ are turned on, it is switched to the H side, and transistors Tr ₂ , When Tr ₄ and Tr ₆ are turned on, it means that they have switched to the L side. In this way transistor Tr ₁
Tr ₆ is connected to each magnetic pole detection element as one side contact and other side contact of each of switching parts S ₁ , S ₂ and S ₃ .
It is switched by detecting the polarity of H ₁ , H ₂ , and H ₃ .

The constant current device A compares and amplifies the winding current detected value by the resistor _R1 and the control input signal _VIN by the transistor _Tr7 , thereby obtaining a constant current value i0 by the transistor _Tr8 , and also obtains a constant current value _i0 by the transistor Tr8. A constant current value i ₀ is also obtained by the transistor Tr ₁₀ connected to the transistor Tr ₉ in a phase-inverted manner. and these constant current values
i ₀ is a signal from the switch drive units C ₁ , C ₂ , C ₃ , and the transistors Tr ₂ , Tr ₄ , Tr ₆ of the L side switching unit corresponding to the transistor Tr ₈ and the transistor
Among the transistors Tr ₁ , Tr ₃ , and Tr ₅ of the H side switching section corresponding to Tr ₉ and Tr ₁₀ , the emitter current is of the ON transistor, and since the impedance of each current path is the same, the ON
The emitter current flowing to the transistors that are on is equal to the constant current value _i0 divided by the number of transistors that are on on the H side and L side, respectively. Therefore, the current value I ₀ or I ₀ /2 flowing to each stator winding is equal to the emitter current of the ON transistor on the H side or L side multiplied by the current amplification factor of that transistor. It is proportional to the constant current value i ₀ or i ₀ /2 of Tr ₈ or Tr ₉ or Tr ₁₀ , and the winding current of I ₀ or I ₀ /2 flows respectively, so the steps are shown as g, h, and i in Fig. 3. current flows to each stator winding.

The current divider B ₁ is composed of resistors R ₅ , R ₆ , R ₇ , collectors and emitters of transistors Tr ₁₁ , Tr ₁₃ and Tr ₁₅ and bases and emitters of transistors Tr ₁ , Tr ₃ and Tr ₅ . Current divider B ₂ is a resistor
R ₂ , R ₃ , R ₄ , collector-emitter of transistors Tr ₁₂ , Tr ₁₄ , Tr ₁₆ and transistors Tr ₂ , Tr ₄ ,
Consists of Tr ₆ base emitter.

Due to the above configuration and its effect, the current values of each stator winding W ₁ , W ₂ , W ₃ are as shown in g, h, i in Fig. 3.
Since the torque waveform becomes step-like as shown in FIG. 3, j, k, and l in FIG. 3, the total torque waveform becomes as shown in FIG. 3 m. Therefore, the torque ripple was reduced to about 14.5%, compared to about 28% in the conventional example, and a sufficiently large driving torque was obtained.

Since the present invention is configured as described above, the constant current distributed by the constant current device and the current divider in accordance with the polarity of the rotor always flows through each stator winding under control of the switching section, so that the torque ripple is reduced. A drive circuit for a brushless motor can be obtained which has excellent effects such as a sufficiently large drive torque with little torque and the ability to reduce the size of the motor body.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a drive circuit of a conventional brushless motor, Figure 2 is a diagram of the principle configuration of a drive circuit of a brushless motor according to the present invention, Figure 3 is a voltage/current/torque waveform diagram of each part of the same circuit, and Figure 4. is a circuit diagram of one embodiment of the same as above. A... Constant current device, B ₁ ... First current distributor, B ₂
...Second current divider, _C1 , _C2 , _C3 ...Switch driving section, _S1 , _S2 , _S3 ...Switching section, D...Diode, _H1 , _H2 , _H3 ...Magnetic pole detection element, Tr ₁ , Tr ₃ ,
Tr ₅ ...H side switching section transistor (one side contact), Tr ₂ , Tr ₄ , Tr ₆ ...L side switching section transistor (other side contact), W ₁ , W ₂ , W ₃ ... Stator winding .

Claims (1)

[Claims] 1. A multi-pole magnetized rotor, a star-connected stator winding, a magnetic pole detection element provided corresponding to each phase of the winding, and a connection corresponding to each phase of the winding. a switching unit that switches the connection as well as a switching unit; and three switching drive units that switch the switching unit between a contact on one side and a contact on the other side in accordance with the polarity detected by the magnetic pole detection element.
A constant current device that supplies a constant current to these three switching drive units, and a constant current device that is provided between this constant current device and one side contact of the three switching drive units, and that allows the switching unit to connect the windings to one side. a first current divider that distributes the constant current and the constant current equally divided into two phases to the two phases when the phase is energized and when the two phases are energized; a contact on the other side of the three switching parts; a second current divider that is provided between the constant current device and receives the sum of constant currents of the two phases distributed by the first current divider and the constant current; A brushless motor drive circuit characterized by controlling the current flowing through the motor in a stepped manner.