JPS6130475Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a drive circuit for a brushless motor having star-connected stator windings, and compensates for variations in the current amplification factor of transistors in the power supply section that function to switch the drive current flowing to the windings. This reduces torque ripple and provides stable rotation.

For example, a drive circuit for a three-phase brushless motor to which the present invention is applied will be explained with reference to FIG. Lines W ₁ , W ₂ ,
W ₃ are arranged in a star connection.

On the other hand, the power supply section _S1 that controls the power supply to the winding _W1 connects in series the transistor _Tr1 on the power supply positive side and the transistor _Tr2 on the power supply negative side, and connects the winding _W1 to the connection point of these two transistors. It is formed by connecting one end. Similarly, the transistor Tr ₃ on the power supply positive side and the transistor Tr ₄ on the power supply negative side are connected in series to form a power supply section S ₂ that controls the power supply to the winding W ₂ , and the transistor Tr ₅ on the power supply positive side is connected in series.
A power supply unit S ₃ is formed by connecting the power supply voltage and the power supply negative side transistor Tr ₆ in series to control the power supply to the winding W ₃ .

Then, position detection means H ₁ , H ₂ ,
Hall elements as H ₃ are connected to amplifiers G ₁ , G ₂ , G ₃ respectively to output position signals, and diodes D ₁ ,
D ₂ ,...D ₆ , transistors Tr ₁₁ , Tr ₁₂ ,...Tr ₁₆ are power supply positive side transistors of the power supply section S ₁ , S ₂ , S ₃
Tr ₁ , Tr ₃ , Tr ₅ and transistors Tr ₂ , Tr ₄ , Tr ₆ on the negative side of the power supply are cyclically switched.

Comparison amplifier _A1 , which forms the signal comparison section, has a non-inverting input terminal (+) that receives a speed control signal proportional to the speed error between the motor rotation speed and the reference rotation speed, and a non-inverting input terminal (+) that receives a speed control signal that is proportional to the current value flowing to the winding. It has an inverting input terminal (-) which receives the signal as input, and performs signal comparison.

For this purpose, the inverting input terminal (-) of comparison amplifier _A1
is grounded through the resistor R _E , and all windings W ₁ ,
Connect the line α on the negative side of the power supply to the amplifier _A1 side of the resistor _RE so that the current that has flowed through W ₂ and W ₃ flows through the resistor _RE .

The output of the comparison amplifier A ₁ is a constant current device J ₁ that supplies the base current of the transistors Tr ₁ , Tr ₃ , and Tr ₅ on the positive side of the power supply, and the base current of the transistors Tr ₂ , Tr ₄ , and Tr ₆ on the negative side of the power supply. These transistors _{Tr 1 ,}
Supply and control the base current of Tr ₂ ,...Tr ₆ .

Constant current device _J1 is connected to the emitters of transistors _Tr11 , _Tr13 , and _Tr15 via emitter resistors _R1 , _R3 , and _R5 , respectively. Furthermore, these transistors
The collectors of Tr ₁₁ , Tr ₁₃ and Tr ₁₅ are connected to the bases of transistors Tr ₁ , Tr ₃ and Tr ₅ on the positive side of the power supply, respectively. _The bases _of transistors Tr ₁₁ , _{Tr 13} and Tr ₁₅ are connected to resistors Ra, Rb and
They are connected via Rc and further via diodes D ₁ , D ₃ , and D ₅ .

Note that the cathodes of the diodes D ₁ , D ₃ , and D ₅ are connected to the base sides of the transistors Tr ₁₁ , Tr ₁₃ , and Tr ₁₅ .

Constant current device _J2 is connected to the emitters of transistors _Tr12 , _Tr14 , and _Tr16 via emitter resistors _R2 , _R4 , and _R6 , respectively. Furthermore, these transistors
The collectors of Tr ₁₂ , Tr ₁₄ , and Tr ₁₆ are connected to the bases of transistors Tr ₂ , Tr ₄ , and Tr ₆ on the negative side of the power supply, respectively. _The bases of transistors Tr ₁₂ , Tr ₁₄ , _and Tr _{16 are} connected to resistors Ra,
They are connected via Rb and Rc and further via diodes D ₂ , D ₄ , and D ₆ . Note that the anode sides of the diodes D ₂ , D ₄ , and D ₆ are connected to the base sides of the transistors Tr ₁₂ , Tr ₁₄ , and Tr ₁₆ .

With this circuit configuration, the Hall elements H ₁ ,
Amplifiers G ₁ , G ₂ , by rotor magnetic pole detection of H ₂ , H ₃ ,
The position signal output from G ₃ activates the transistors of the power supply section S ₁ , S ₂ , S ₃ , that is, the transistor on the positive side of the power supply.
Tr ₁ , Tr ₃ , Tr ₅ , transistors on the negative side of the power supply
Tr ₂ , Tr ₄ , Tr ₆ are switched, and the windings W ₁ ,
The connection status of W ₂ and W ₃ is determined, and the respective windings are
The current paths of W ₁ , W ₂ , and W ₃ are determined.

Furthermore, the output of the comparator amplifier A ₁ connects the power supply units S ₁ , S ₂ , S ₃
The base currents of the transistors Tr ₁ , Tr ₂ ,...Tr ₆ are controlled, and the current value flowing through each winding W ₁ , W ₂ , W ₃ is controlled to control the rotational speed of the motor.

I will explain this situation using a graph.

First, in FIG. 2, the horizontal axis represents the electrical angle, and the vertical axis represents the output of the Hall element. The Hall elements are arranged with electrical angle relationships of 2nπ, 2nπ + 2/3, and 2nπ + 4/3, where n is an arbitrary integer, and their output changes change the windings W ₁ , W ₂ , W ₃ A rotating magnetic field is obtained. Therefore, the Hall element _H1 is a Hall element as shown in Figure 2 A.
The output of H ₂ changes as shown in FIG. 2 (b), and the output of the Hall element H ₃ changes as shown in FIG. 2 (c). Note that the solid line waveform and the one-dot chain line waveform in the figure are due to the difference in the sensitive magnetic pole.

Due to this change in the output of the Hall element, the amplifier
A position signal is generated by G ₁ , G ₂ , and G ₃ and sent to the power supply section S ₁ ,
By switching S ₂ and S ₃ and changing the electrical angle, the power feeding relationship to each of the windings W ₁ , W ₂ , and W ₃ as shown in FIG. 3 can be obtained.

Here, the circuit constants are exactly the same for each phase, and the power supply section
If the current amplification factors of the transistors Tr ₁ , Tr _{2 ,} . . . Tr ₆ of S ₁ , S 2 , S ₃ are all the same, then the constant current devices J ₁ and J ₂ will supply the same current.

Furthermore, when the transistors of two power supply parts are connected in parallel to a constant current device, for example, in the section of electrical angle 0 to π/ ₃ in _{FIG .} From transistor Tr ₁₁ , resistor R ₁
The circuit from transistor Tr ₅ to transistor Tr ₁₅ and resistor R ₅ on the power supply section S ₃ side is connected in parallel, and since the impedances of both circuits are equivalent, transistors Tr ₁ and Tr ₅ The base currents flowing in both are equal, and the current supplied to the constant current device _J1 is equally divided into two. Since the current amplification factor of both transistors is also the same, the same drive current flows through the windings W ₁ and W ₃ even if the back electromotive force generated from each winding is different. Furthermore, the sum of the currents flowing through the windings _W1 and _W3 flows through the winding _W2 .

Therefore, the currents I _W1 , I flowing through the windings W ₁ , W ₂ , W ₃
As shown in Figure 4 A, B, and C, _W2 and I _W3 are only shifted by 2/3π in electrical angle, but the current value changes in exactly the same way in a stepwise manner, and the respective windings W ₁ and W The torques T _W1 and T _W2 generated from 2 and _W 3 _show exactly the same waveforms as shown in FIG.

Note that even when the current value is negative, the torque generated at that time acts in the same direction as when the current value is positive, so the torque waveform when the current value is negative is folded back in the positive direction.

When the torques of these three windings are added, the torque ripple is reduced to about 14% as shown in FIG. 5D, and a motor exhibiting stable rotation is obtained.

However, if the current amplification factors of transistors Tr ₁ , Tr ₂ , ...Tr ₆ on the power supply positive side and power supply negative side are all the same, the torque ripple becomes small as described above.If transistors with different current amplification factors are used, e.g. What happens when the current amplification factor of the transistor Tr ₄ is lower than others will be explained below in the electrical angle range from 0 to 1/3π. As is clear from FIG. 3, the transistors Tr ₁ ,
Tr ₄ and Tr ₅ are conductive, and a circuit is formed in which winding W ₁ and W ₃ are connected in parallel, and winding W ₂ is connected in series.

Here, the current amplification factor of the transistor Tr ₄ on the negative power supply side of the power supply section S ₂ is smaller than the current amplification factors of the transistors Tr ₁ and Tr ₅ , so the voltage between the collector and emitter of the transistor Tr ₄ increases, and the winding
The potential at the connection midpoint P of W ₁ , W ₂ , and W ₃ increases. Then, the voltage between the collector and emitter of transistors Tr ₁ and Tr ₅ becomes saturated, and the equivalent circuit becomes the 6th one.
It will look like the figure.

That is, the power supply positive side line β and the three windings W ₁ ,
Windings W ₁ and W ₃ are connected in parallel between the connection midpoint P of W ₂ and W ₃ , and winding W ₂ and the transistor Tr are connected between the connection midpoint P and the negative power supply line α. ₄ are connected in series. If the winding resistance of each winding W ₁ , W ₂ , W ₃ in FIG. 6 is R _W , the winding W ₁ has a resistance R _W and a back electromotive force E ₁ ,
The winding W ₃ consists of a resistance R _W and a back electromotive force E ₃ , and the winding
W ₂ consists of resistance R _W and back electromotive force E ₂ . back emf
E ₁ , E ₂ , and E ₃ show exactly the same waveforms as the outputs of Hall elements H ₁ , H ₂ , and H ₃ , only shifted by 2/3π, as shown in FIGS. 7A, 7B, and 7C.

Then, set the potential of the power supply positive line β to +Vcc,
If the potential of the connection midpoint P is Vo, then the winding at this time
The currents I _W1 and I _W3 flowing through W ₁ and W ₃ are I _W1 = Vcc-Vo-E ₁ /R _W = Vcc-Vo/R
_W −1/R _W E ₁ …(1) I _W3 = Vcc-Vo-E ₃ /R _W = Vcc-Vo/R
_W −1/R _W E ₃ …(2) Since E ₁ ≠ E ₃ , I _W1 and I _W3 are different.

If this state is graphed in electrical angles between 0 and 1/3π, as shown in Figure 8A, the currents I _W1 , I _W2 , I _W3 flowing through each winding W ₁ , W ₂ , W ₃ are expressed in electrical angles. The current I W1 does not always have a constant value between 0 and 1/3π, and the current I _W1 decreases as the electrical angle changes, while the current I _W3 increases on the contrary. Further, the current I _W2 is the sum of I _W1 and I _W3 , and the direction of the current is opposite.

Therefore, the torque generated from each winding is the product of the current value and the torque constant proportional to the back electromotive force, so the torque T _W1 , generated from the windings W ₁ , W ₂ , W _{3 respectively} T _W2 and T _W3 are as shown in Figure 8 (b). The addition of the torques T _W1 , T _W2 , and T _W3 results in a waveform with extremely irregular and large amplitude, resulting in extremely poor torque ripple.

As shown in Figure 9, if n is an integer,
The torque ripple is large in the section from 2n/3π to 2n+1/3π, and becomes small in the section from 2n-1/3π to 2n/3π, and the torque ripple repeats increases and decreases.

In this way, the torque ripple is large and appears with a large period, making the rotation of the motor extremely unstable.

Therefore, in order to eliminate such drawbacks, the present invention suppresses the torque ripple by compensating for variations in the current amplification factors of the transistors of the respective power supply sections S ₁ , S ₂ , and S ₃ .

The gist of this is to compensate for variations in the current amplification factor by changing the base current.
The non-inverting input terminal (+) of A ₂ has windings W ₁ , W ₂ ,
Connect the connection middle point P of W ₃ , and invert the input terminal (+)
is a resistor Rx connected in series between the power supply +Vcc and ground,
The reference voltage obtained by dividing the voltage with Ry, that is, the resistor Rx,
Connect Ry connection point Q. Then, the error signal of comparator A ₂ is applied to constant current device J ₂ , and if the potential at the midpoint of the connection increases, the supply current value of constant current device J ₂ is increased, and the power supply connected to constant current device J ₂ is increased. This compensates for the small current amplification factor of the transistor in the section. In addition, by inverting and applying the error signal of comparator A ₂ to constant current device J ₁ , the connection midpoint P
When the potential increases, the current supplied to the constant current device _J1 is lowered. Then, the base current of the transistor in the power supply unit connected to the constant current device J ₁ side is reduced to compensate for the large current amplification factor of this transistor, and as a whole, the transistors Tr in the power supply unit S ₁ , S ₂ , S ₃ The current amplification factors of _{Tr 1} , Tr ₂ , ...Tr ₆ are made to be apparently the same.

Note that, as described above, it is not necessary to compensate both the constant current devices J ₁ and J ₂ , but only one of them may be compensated.

The main part of this embodiment will be described with reference to FIG. 11. A comparison amplifier _A1 is formed by a transistor _Tr7 ,
The transistor Tr ₈ part forms a constant current device J ₂ , the transistor Tr ₁₀ part forms a constant current device J ₁ , and the emitters of transistors Tr _A and Tr _B are both connected to a constant current device J ₃ . Furthermore, each collector is connected to the power supply +Vcc via resistors R _A and R _B to connect the comparator.
It is set as _A2 . The base of transistor Tr _A is connected to the resistor Rx inserted in series between the power supply +Vcc and ground.
Connect the connection point Q with Ry. The base of the transistor Tr _B is connected to the connection midpoint P of the windings W ₁ , W ₂ , and W ₃ via a resistor Rc, and is grounded via a capacitor C ₁ . The collector of transistor Tr _A is then connected to the emitter of transistor Tr ₈ forming constant current device J ₂ .

In this way, the connection midpoint P of windings W ₁ , W ₂ , W ₃
The change in potential of is smoothed by resistor Rc and capacitor _C1 and input to transistor Tr _B , compared with the reference voltage applied to the base of Tr _A , and the error signal is applied to the emitter of transistor Tr ₈ to set up a constant current device. It's in control. In _other words, the _transistor
The collector current of Tr _A decreases, and the transistor Tr _A
The potential of the collector increases.

Therefore, the collector current of transistor _Tr8 increases. In other words, the supply current value of the constant current device J ₂ increases to compensate for the shortfall in the current amplification factor of the transistor in the power supply section connected to the constant current device J ₂ .

Note that when the transistor Tr ₄ is not involved in power supply, the potential at the connection midpoint P is the same as the potential at the connection point Q, and no error signal is output from the comparator A ₂ .

In this way, two transistors are connected in series between a rotor with magnetic poles, a multi-phase stator winding arranged opposite to the rotor and star-connected, and a power supply positive side and a power supply negative side. and a power supply section in which one end of the winding of each phase is connected to the connection point between the transistors, and a position signal detection unit that generates a signal every predetermined rotation speed of the rotor to control the input section of the power supply section. means, a signal comparing section for comparing a winding current signal of the stator winding with a speed control signal such as a rotation speed, and each of the transistor groups on the power supply positive side and the power supply negative side of the power supply section. A drive circuit for a brushless motor comprising first and second constant current devices respectively connected to an input section and supplying a constant current signal according to an output signal of the signal comparison section, wherein the windings of each phase are provided. A comparator is provided that generates an error signal by comparing the midpoint voltage connected at the other end with a reference voltage, and the error signal of the comparator is applied to at least one of the constant current devices, and in response to the error signal, the The brushless motor drive circuit, which is characterized by controlling the base current of each transistor, can compensate for any variations in the current amplification factors of the transistors Tr ₁ , Tr ₂ ,...Tr ₆ in the power supply section. , it is possible to reduce torque ripple and obtain stable rotation in the same way as when transistors with uniform characteristics are used.

Therefore, complicated work such as selecting transistors to be used can be eliminated.

[Brief explanation of the drawing]

Figure 1 is a drive circuit diagram of a conventional brushless motor, Figure 2 is an output waveform diagram of the Hall element used in the drive circuit of this brushless motor, and Figure 3 is the path of current flowing to the windings due to the rotation of the brushless motor. A circuit diagram showing the changes. Figure 4 is a waveform diagram of the current flowing through each winding. Figure 5 is a waveform diagram of the torque generated from each winding and the total torque. Figure 6 is a diagram of the transistor.
When the current amplification factor of Tr ₄ is small, the current flow to the windings in the electrical angle range of 0 to 1/3 π is shown. Figure 7 is a waveform diagram of the back electromotive force generated from each winding. Figure 8 Figure A is a diagram of the current waveform flowing to each winding in the interval of 0 to 1/3π in electrical angle when the current amplification factor of transistor Tr ₄ is small, and Figure B is a diagram of the electrical angle of 0 when the current amplification factor of transistor Tr ₄ is small. Torque waveform diagram generated from each winding in the section of ~1/3π, Figure 9 shows the transistor Tr ₄
FIG. 10 is a diagram of a torque waveform summarizing the torque generated from each winding when the current amplification factor is small, FIG. 10 is a circuit diagram of the present invention, and FIG. 11 is a circuit diagram of an embodiment thereof. H ₁ , H ₂ , H ₃ ...Position signal detection means, S ₁ , S ₂ ,
S ₃ ... power supply section, W ₁ , W ₂ , W ₃ ... winding, J ₁ , J ₂ ,
J ₃ ... constant current device, A ₁ , A ₂ ... comparator.

Claims (1)

[Scope of utility model registration request] A rotor with magnetic poles, a multi-phase stator winding arranged opposite to the rotor and star-connected, and two wires between the power supply positive side and the power supply negative side.
a power supply section in which several transistors are connected in series and one end of the winding of each phase is connected to the connection point between the transistors; a position signal detecting means for controlling; a signal comparing section for comparing a winding current signal of the stator winding with a speed control signal such as a rotation speed; and a signal comparing section for comparing a winding current signal of the stator winding with a speed control signal such as a rotation speed; In the brushless motor drive circuit, the brushless motor drive circuit comprises first and second constant current devices connected to each input section of the transistor group and supplying a constant current signal according to the output signal of the signal comparison section. A comparator is provided that generates an error signal by comparing the voltage at the other end of the winding of each phase with a reference voltage, and the error signal of the comparator is applied to at least one of the constant current devices, and the error signal is A drive circuit for a brushless motor, characterized in that the base current of each of the transistors is controlled in response to.