JPH07118938B2 - Motor speed controller - Google Patents

Description

TECHNICAL FIELD The present invention relates to a speed control device for a brushless motor.

2. Description of the Related Art In recent years, drive motors for audio equipment, video equipment, etc. have long lifespans, high reliability, and thin shapes.
A so-called brushless motor having an electronic switch using a transistor has been increasingly used instead of a conventional DC motor having a mechanical switch mechanism such as a brush and a commutator. Further, in the speed control device for the brushless motor, feedback is applied to the drive current of the motor in order to suppress uneven rotation and uneven torque due to variations in the current amplification factor (h _FE ) of the drive transistor. As a conventional technique of the speed control device which has performed such current feedback, for example, Hiroshi Yamada, "Basics and Applications of Precision Small Motors" (published on July 1, 1975), Travel Electronic Publishing Company, 23
There is something like that shown on page 4.

Hereinafter, an example of the above-described conventional motor speed control device will be described with reference to the drawings.

FIG. 4 is a circuit connection diagram of a conventional motor speed control device. In FIG. 4, 1 and 2 are positive and negative power supply lines of the power source, and 3 to 6 are motor drive coils. One end of each of the drive coils 3 to 6 is connected to the negative side power supply line 2, and the other end of each of the drive coils 3 to 6 is connected to the collectors of the drive transistors 7 to 10 and the cathodes of the diodes 11 to 14. ing. The anode sides of the diodes 11 to 14 are commonly connected and connected to the emitter of the transistor 15. Reference numerals 16 and 17 denote Hall elements for detecting the position of the permanent magnet rotor (not shown). One output terminal of the Hall element 16 is connected to the base of the drive transistor 7, and the output terminal is 18
The other output terminal that outputs signals having a phase difference of 0 degrees is connected to the base of the drive transistor 8. The emitters of the drive transistors 7 and 8 are commonly connected and are also connected to the positive side feed line 1 via a resistor 18. One output terminal of the hall element 17 is connected to the base of the drive transistor 9, and the output terminal is 18
The other output terminal that outputs signals having a 0 ° phase difference is connected to the base of the drive transistor 10. The emitters of the drive transistors 9 and 10 are commonly connected and also connected to the positive side feed line 1 via a resistor 19. One input terminal of each of the Hall elements 16 and 17 is connected to the positive side feed line 1, and the other input terminal of each of the Hall elements 16 and 17 is connected to the transistor 22 via resistors 20 and 21, respectively.
Connected to the collector. The emitter of the transistor 22 is connected to the negative side feed line 2, and the base is connected to the positive side feed line 1 via a resistor 26 and the collector of the transistor 15. A capacitor 23 and a series circuit of a resistor 24 and a capacitor 25 are connected between the collector and the base of the transistor 22. The base of the transistor 15 is connected to the positive feed line 1 via a resistor 27, and a variable resistor 31 and a resistor 32 are connected.
Is connected to the negative side feed line 2 via a direct circuit, and is connected to the emitter via a series circuit of a resistor 28 and a resistor 29.
A thermistor 30 is connected to both ends of the resistor 29 for temperature compensation. A capacitor 33 is connected between the base and emitter of the transistor 15.

The operation of the motor speed control device configured as described above will be described below.

The motor shown in FIG. 4 has two Hall elements 1 as described above.
It is a four-phase unidirectional brushless motor using 6,17 and four drive coils 3-6. That is, the drive coils 3 are spatially arranged at different positions by 90 degrees.
~ 6, the Hall element according to the circuit of the permanent magnet rotor
Currents controlled by 16 and 17 flow sequentially to generate a rotating magnetic field. In this case, the current flowing through the drive coils 3 to 6 is proportional to the current flowing through the Hall elements 16 and 17. The motor torque is controlled by setting the current flowing through the Hall element to a value proportional to the speed error.

That is, although the drive transistors 7 to 10 are sequentially switched, there is a period during which no current flows in the drive coils 3 to 6 due to the switching, so that the back electromotive force generated in the drive coils 3 to 6 during the energization suspension period. By rectifying the voltage with the diodes 11 to 14, smoothing it, comparing it with the reference voltage, and amplifying it, a current proportional to the speed error is passed through the transistor 22, and the current passed through the Hall elements 16 and 17 is controlled to drive the drive transistor 7 through. The rotation speed is kept constant by controlling the power supply amount of 10.

Here, the current transmitted to the drive coils 3 to 6 is a speed error signal, and the resistors 20 and 21 and the Hall element 1 respond to the voltage difference between the collector of the transistor 22 and the positive side feed line 1.
It is substantially determined by the input resistances of 6,17, the base-emitter voltage of the drive transistors 7-10, and the resistors 18,19.
That is, feedback is performed to the drive current so that the motor torque is controlled by the speed error signal without variations in each phase.

Problems to be Solved by the Invention However, in the above configuration, since the resistors 18 to 19 are connected to the emitters of the driving transistors 7 to 10,
The voltage drop reduces the maximum voltage that can be applied to the drive coils 3 to 6. That is, there is a problem that the maximum torque of the motor is reduced. Therefore, it is impossible to insert the resistors 18 to 19 in a motor having no torque margin with respect to the power supply voltage, and it is extremely difficult to suppress rotation unevenness and torque unevenness due to characteristic variations of the driving transistors 7 to 10. there were. In addition, the resistance 18 ~
19 is often required high power, therefore lower price,
It was also disadvantageous in terms of space saving.

In view of the above problems, the present invention eliminates the emitter resistance of the drive transistor, which is a cause of the decrease in the maximum torque of the motor, which is also disadvantageous in cost reduction and space saving, and is excellent in rotation unevenness and torque unevenness. A speed control device for a motor having control characteristics is provided.

Means for Solving the Problems In order to solve the above problems, the motor speed control device of the present invention is a motor drive coil of a plurality of phases, one end of each of which is connected to one power supply line, and the drive coil. A plurality of drive transistors connected to the other end of each, a position detector that obtains a signal according to the position of the mover, and a switching of the energization state to the drive transistors in response to the signal of the position detector. An energization switching circuit, a speed detection device for obtaining a signal according to the speed of the motor, an error amplification circuit for amplifying an error between a voltage corresponding to an output signal of the speed detection device and a reference voltage, and an output of the error amplification circuit. To the drive transistor, the error signal transmission means comprising drive output combining means for combining the outputs of the plurality of drive transistors, The output of the drive output synthesizing means is connected to the input of the error signal transmitting means.

With the above-described configuration, the present invention can transmit the electric power corresponding to the speed error signal to the drive coil without the variation between the phases, and the emitter resistance of the drive transistor is not required, so that the maximum torque is not reduced and the accuracy is high. Speed control is possible.

Embodiment Hereinafter, a motor speed control device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a rotation configuration diagram of a motor speed control device according to an embodiment of the present invention. In FIG. 1, reference numeral 40 is a positive side power supply line of a power source, and 41, 42 and 43 are motor drive coils.
One end of each of the drive coils 41, 42 and 43 is connected to the feed line 40, and the other end thereof is connected to the collectors of the drive transistors 44, 45 and 46, the connection points of which are a, Let b and c. Capacitors 47, 48 and 49 are connected between the connection points a, b and c and the ground, respectively, and a capacitor 50 is connected between the feed line 40 and the ground. The drive transistor 4
The emitters of 4,45 and 46 are grounded, respectively, and the bases thereof are grounded via resistors 51,52 and 53, respectively. 54, 55 and 56 are position detectors for detecting the position of a mover, for example, a permanent magnet rotor (not shown), which are composed of, for example, Hall elements, and their input terminals are respectively connected between the power supply terminal 57 and the ground. The output terminals of the current switching circuit 58 are connected in parallel, and the output terminals of the current switching circuit 58 are connected to the drive transistors 44, 45 and 4 respectively.
Connected to the base of 6. The connection points a, b and c are connected to the inverting input terminals of inverting amplifiers 62, 63 and 64 via resistors 59, 60 and 61, respectively. The non-inverting input terminals of the inverting amplifiers 62, 63 and 64 are resistors 65 and 66, respectively.
And 67, and the output terminal is connected to the inverting input terminal through resistors 68, 69, and 70, respectively, and is commonly connected. Let the common connection point be d. A voltage dividing circuit composed of resistors 71 and 72 is connected between the feeding line 40 and the point d. Let the partial pressure point be e. A capacitor 73 is connected between the feed line 40 and the voltage dividing point e. The partial pressure point e
Is connected to the inverting input terminal of the error amplifier 74 via the resistor 75, and the output terminal of the error amplifier 74 is connected to the inverting input terminal via the parallel circuit of the resistor 76 and the capacitor 77.

A reference voltage generating circuit 78 is connected to the non-inverting input terminal of the output terminal amplifier 79. The amplifier 79
The output terminal of is connected to the base of a transistor 81 whose collector is grounded, and the emitter of the transistor 81 is connected to the feed line 40 through the constant current source 80 and to the base of the transistor 83. The emitter of the transistor 83 is grounded via a resistor 84 and is connected to the inverting input terminal of the amplifier 79, and the collector is connected to the feed line 40 via a resistor 82 and the non-inverting of an amplifier 85. It is connected to the input terminal. The amplifier
The output terminal of 85 is connected to the inverting input terminal to form a voltage follower. The output point of the voltage follower is f
And The output point f is connected to the non-inverting input terminal of the error amplifier 74 and also to the non-inverting input terminal of the amplifier 88 via the resistor 89. The output terminal of the error amplifier 74 is connected to the feed line 40 via a voltage divider circuit of resistors 87 and 86. The voltage dividing point of the voltage dividing circuit is connected to the inverting input terminal of the amplifier 88. The amplifier 88
The output of is connected to the current switching circuit 58. Further, the connection points a, b and c are connected to one ends of resistors 90, 91 and 92, respectively, and the other ends of the resistors 90, 91 and 92 are commonly connected and connected to a non-inverting input terminal of the amplifier 88. Has been done.

The operation of the motor speed control device configured as described above will be described below with reference to FIGS. 1, 2, and 3.

First, FIG. 2 is a signal waveform diagram of each point in FIG.
Va, Vb and Vc are voltages generated at points a, b and c, respectively, and V _B44 , V _B45 and V _B46 are drive transistors 4 respectively.
It is the base voltage of 4,45 and 46, and Vd represents the composite signal at the output common connection point d of the inverting amplifiers 62, 63 and 64.

First, the position of the NS magnetized permanent magnet rotor is detected by the position detector.
54, 55, and 56, and the position detector signal is processed in the current switching circuit 58 to obtain the signal of FIG.
As indicated by V _B44 , V _B45, and V _B46 , a conduction switching signal that sequentially switches during an electrical conduction period of 120 ° in electrical angle and a 240 ° rest period is applied to the bases of the drive transistors 44, 45, and 46.
The motor is rotated by sequentially energizing the drive coil according to the energization switching signal. Along with the rotation, the drive coils 41, 42 and 43 generate a sinusoidal back electromotive force centered on the voltage of the power supply line 40, which is shown in FIGS. 2A, 2B, 2C and 2C. The shaded portion is the energization period, and the other periods are the energization suspension periods, and the counter electromotive voltage itself is generated. The counter electromotive voltages Va, Vb, and Vc have a phase difference of 120 degrees with each other.

The counter electromotive voltage Va is inverted and amplified by the inverting amplifier circuit composed of the inverting amplifier 62 and the resistors 59, 68, and 65 with the voltage of the feeding line 40 (Vcc) as a reference. Vb and Vc are also Vc
It is inverted and amplified based on c. However, inverting amplifiers 62, 63 for inverting and amplifying the counter electromotive voltages Va, Vb and Vc, and
Each of the 64 outputs is connected in common. At this time, if the respective outputs of the inverting amplifiers 62, 63 and 64 are configured so that only the suction side and not the sweep side are provided as the current supply capability to the load, the common output d of the inverting amplifiers 62, 63 and 64 is An output waveform is obtained by inverting and amplifying the highest voltage of the back electromotive forces Va, Vb, and Vc with reference to Vcc. As shown in Fig. 2 Vd, the state is 120 electrical cycles,
It has a ripple waveform corresponding to the magnitude of the back electromotive force. That is, this signal becomes a signal of a lower voltage level with respect to Vcc when the motor speed increases and the back electromotive voltage generated in each drive coil increases. Conversely, if the speed decreases, the signal level increases. Therefore, the voltage Vd at point d in FIG. 1 changes according to the speed of the motor. The voltage Vd
Is divided by resistors 71 and 72 and capacitor 73, smoothed, and converted into a DC voltage, that is, speed voltage Ve. On the other hand, the output voltage V _REF of the reference voltage generation circuit 78 is converted to the Vcc reference voltage Vf via the reference level conversion circuit 93. The error amplifier 74 amplifies an error between the speed voltage Ve and the reference voltage Vf and outputs an error voltage Vg. This is shown in FIG. The error voltage Vg is input to the current switching circuit 58 via the amplifier 88 forming a buffer. The current switching circuit 58 controls the timings of energization and suspension of the drive transistors 44, 45 and 46 based on the signals from the position detectors 54, 55 and 56 and responds to the magnitude of the signal from the amplifier 88. Signal to drive transistors 44, 45 and 46
It is configured so that it can be supplied to the base of. The collector outputs of the drive transistors 44, 45 and 46 are resistor 9
A negative feedback loop is formed with respect to the input of the amplifier 88 via 0, 91 and 92, so that the amount of power supply to the drive coil can be controlled according to the error voltage Vg without variations between phases. That is, in FIG. 1, resistors 86, 87, 89
The value of -92 was as _{R 86, R 87, R 89} ~R 92 respectively, prior to the amplifier 88
If the virtual ground between both inputs of is established and its input terminal voltage is V ₁ , In the above equation, Rs = R ₈₇ = R ₈₉ Then, Here, Va, Vb, and Vc are sinusoidal waves having a phase difference of 120 degrees and an amplitude around the center of Vcc as shown in FIG. 2, so that each composite waveform is an internal impedance of the drive coil.
Letting Za and the same current Ia, Va + Vb + Vc = 3Vcc−IaZa (5).

From equations (4) and (5) From equations (3) and (6) As shown by the equation (8), the current Ia supplied to the drive coil is proportional to the difference between the error voltage Vg and the reference voltage Vf. That is, the conduction current Ia is equal to the error voltage Va regardless of the variation of the drive transistors 44, 45 and 46.
Controlled according to g. This state is shown in FIG.

In FIG. 3, the broken line Ia indicates a negative current, and in actual operation, only the current from the collector to the emitter of the drive transistor exists. Therefore, the current during this period becomes zero.

As described above, according to this embodiment, the drive transistor
For the collector outputs of 44, 45 and 46, by providing a negative feedback loop to the input of the amplifier 88 via the resistors 90, 91 and 92, the current according to the error voltage Vg without reducing the maximum torque. The drive coils 41, 42 and 4
3 can be supplied with no phase difference, and excellent control characteristics can be obtained.

EFFECTS OF THE INVENTION As described above, the present invention has the error signal transmitting means for transmitting the output of the error amplifier circuit to the drive transistor, and the error signal transmitting means synthesizes the respective outputs of the drive transistor. By providing a negative feedback loop at each output of the drive transistor and the input of the error signal transmission means via the drive output synthesizing means, the control characteristics and the maximum torque are improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a motor speed control device in an embodiment of the present invention, FIGS. 2 and 3 are signal waveform diagrams of respective points in FIG. 1, and FIG. 4 is a conventional motor speed control. It is a circuit connection diagram. 40 …… Feed line, 41,42,43 …… Motor drive coil, 44,4
5,46 …… Drive transistor, 54,55,56 …… Position detector,
58: current switching circuit, 100: speed detection device, 110: error amplification circuit, 120: error signal transmission means, 121: drive output composition means.

Claims (2)

[Claims] 1. A plurality of phase motor drive coils each having one end connected to one power supply line, a plurality of drive transistors connected to the other end of each drive coil, and a plurality of drive transistors depending on the position of a mover. A position detector for obtaining a signal, a conduction switching circuit for sequentially switching the conduction state to the drive transistor in response to a signal from the position detector, a speed detector for obtaining a signal according to the speed of the motor, and the speed An error amplification circuit that amplifies an error between the voltage corresponding to the output signal of the detector and the reference voltage, and an error signal transmission unit that transmits the output of the error amplification circuit to the drive transistor are provided. A drive output combining means for combining the voltages at the other ends of the plurality of motor drive coils connected to the outputs of the plurality of drive transistors,
A motor speed control device in which an output of the drive output synthesizing means is connected to an input of the error signal transmitting means. 2. The drive output synthesizing means comprises a plurality of resistors each having one end connected to the other end of each of the motor drive coils of a plurality of phases connected to each output of the plurality of drive transistors, The other ends of the plurality of resistors are all common and form the output of the drive output synthesizing means, and the error signal transmitting means includes an amplifier for outputting a signal supplied to the inputs of the plurality of motion transistors, and the drive output synthesizing means. The motor speed control device according to claim 1, wherein the speed control device is a motor.