JPH04178191A - Speed controller for dc brushless motor - Google Patents

Abstract

PURPOSE:To control a rotational speed by obtaining a reference voltage proportional to the rotational speed of a DC brushless motor from the detection end of a bridge circuit and by comparing the voltage with another reference voltage and controlling a feed control transistor through the difference voltage between said voltages. CONSTITUTION:The output voltage of a constant voltage circuit 14 is divided by a resistance type voltage divider circuit composed of a series connection of resistances 21, 22 so that a reference voltage is obtained as the terminal voltage of the resistance 22. When a DC brushless motor varies in the number of revolutions due to load fluctuation, etc., an induced voltage generated in the motor changes and a voltage generated in a motor actuator also changes and the change is divided by resistances 18, 19 constituting a bridge circuit. Then, the divided voltage is compared with the reference voltage of a reference voltage source by an error amplifier 15 and the output of the amplifier is amplified by a transistor 16 and transmitted to a feed control transistor 17 to control the output current I.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a speed control device for a DC brushless motor.

BACKGROUND OF THE INVENTION DC brushless motors have no brushes or commutators and are highly reliable, so they are used in a variety of consumer and industrial equipment. For example, if such a DC brushless motor is used in a fan motor, it is possible to realize a highly reliable motor with low noise, long life, and no brushes or commutator even when rotating at high speed.

However, when attempting to control such a DC brushless motor, conventional speed control devices of this type
A common method is to configure a frequency generator (hereinafter referred to as FG) to perform rotation speed control, and its circuit configuration will be explained with reference to FIG.

In FIG. 2, an FG pattern 31 formed on a substrate
When a multi-pole magnetized rotor magnet passes through, a signal multiplied by FG is induced. The FG multiplied signal is inputted to the FG amplifier 32 and the Schmitt circuit, and then inputted as a speed signal to the speed discretization circuit 36. The speed discretization circuit 36 also includes an oscillation circuit 35 including a crystal oscillator 34.
A reference signal oscillated by is inputted, compared with the speed signal, and acceleration/deceleration pulses are output. This acceleration/deceleration pulse output is integrated by an error amplifier 37 and input to a drive amplifier 38. On the other hand, the motor drive circuit includes motor coils 45, 46, 47 and the motor coils 45, 46.
six drive transistors 48,4 supplying current to 47;
9.50.51°52.53 and drive transistor 48
~53 bridriver 40 and Hall elements 42, 43, 44 and 42° 4 for detecting the rotational position of the motor
3. The drive transistors 48 to 5 according to the output of 44
It is composed of a Hall element distribution circuit 39 that distributes to three energization signals.

By the way, the method using the FG described above requires a multi-pole magnetized rotor magnet and an FG substrate on which an FG pattern 31 is formed for detecting the FC signal as a frequency generator, and also requires a weak FG. To detect the signal,
The speed control circuit was also complex and expensive, requiring a high gain amplifier circuit. Therefore, the speed control device becomes expensive, and inexpensive fan motors are used without speed control.

Problem to be Solved by the Invention However, recently, office equipment such as computers and copiers that use fan motors are used in quiet offices, so noise becomes a problem, and the fan motors do not rotate at high temperatures. Temperature variable speed function that increases the air volume by increasing the number of fan rotations and reduces the noise generated by the fan by lowering the rotation speed when the temperature is low, and a rotation speed variable speed function that changes the fan rotation speed in stages according to the usage mode of the set. has been requested.

In order to realize such a fan motor, an object of the present invention is to provide a DC brushless fan motor that has a novel DC brushless motor speed control device and that achieves the above additional functions at low cost.

Means for Solving the Problems ξ To achieve the above object, a speed control device for a DC brushless motor according to the present invention includes a position detection means for detecting the rotational position of a rotor of a DC brushless motor, and a plurality of motor coils. and a current divider for distributing current according to the output of the position detecting means, the output of the current divider being connected to its base, its emitter being commonly connected, and its collector being connected to the motor coil, A DC brushless motor comprising a drive circuit device including a plurality of drive transistors that drive and rotate the motor by switching a current path to the motor coil according to the output of the distributor, and the motor coil and the drive circuit device. A bridge circuit including a transistor as one piece, a power supply control transistor inserted between a power supply and the bridge circuit, one terminal of which is connected to the power supply via a constant current source, and the other terminal of which constitutes the bridge circuit. a constant voltage circuit connected to a connection point between the emitters of the drive transistors and the first resistor that are commonly connected in the drive device; and means for generating a reference voltage serving as a speed reference based on the output voltage of the constant voltage circuit. It has a configuration consisting of.

Effect With this configuration, by obtaining a reference voltage proportional to the rotation speed of the DC brushless motor from the detection end of the bridge circuit, this voltage is compared with the reference voltage, and the difference voltage controls the power supply control transistor to control the rotation speed. can do.

Furthermore, by using a reference voltage source with positive temperature characteristics as the reference voltage source, it is possible to control the rotation speed of the DC brushless motor to be low at low temperatures (and high at high temperatures. Transistor S
The relationship between the required air volume of the fan motor and the noise level can be optimally selected by changing the rotational speed of the motor step by step according to the usage mode of the set by using W or the like.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

In Fig. 1, 2 is a rotor magnet having 2n (n is an integer) magnetic square root 4-178191 (3) poles, 3.4.5 is a motor coil, and 6.7.8 is a coil 3, 4.5. a drive transistor that supplies current to each of the transistors and drives the motor; 9.10.
11 is a Hall element that senses the magnetic flux of the rotor magnet and detects the rotational position of the rotor; 12 is a Hall element 9.10
．． Drive transistor 6.7.8 according to the output signal of 11
This is a current distributor that switches the energization to. Further, a portion A surrounded by a broken line is a speed control device, and the coil 3
．． 4.5 common connection point is the power supply control transistor 1
7 collector. Also, 13.18.1
9 is a resistor and is the motor coil 3 of the DC brushless motor.
．． 4.5 and drive transistor 6.7.8 and resistor 13,
18 and 19 constitute a bridge circuit.

Further, 20 is a constant current source, 14 is a constant voltage circuit, and the output voltage of the constant voltage circuit 14 is divided by a resistive voltage divider circuit consisting of a series connection of resistors 21 and 22, and the terminal voltage of the resistor 22 is used as a reference. A voltage Es is obtained.

Further, resistors 18 and 19 of a bridge circuit are connected in series between the collector of the power supply control transistor 17 and one terminal of the power supply, and the divided voltage of the resistor voltage divider circuit is compared with the reference voltage, and its output is transferred to the transistor 16. Furthermore, the output of the transistor 16 is added to the base of the power supply control transistor 17 inserted between the bridge circuit and the DC power supply 1, and when the rotational speed of the DC brushless motor increases due to a decrease in the load torque, the output of the transistor 16 is applied to the bridge circuit. The power supply control transistor 17 is controlled to reduce the supplied current I, and to increase the current I when the rotational speed decreases due to an increase in load torque.

The operation of the above configuration will be explained. The structure other than the broken line part A is a DC brushless motor drive device using a conventional three-phase half-wave drive system, and includes Hall elements 9, 10.1.
1 senses the magnetic flux of the rotor magnet 2 and inputs a signal responsive to the magnetic flux to the current distributor 12. Current divider 1
In step 2-, the coil to be energized is determined in response to the output signal of the Hall element, and the energization of the drive transistor is switched by the output from the coil to rotate the motor. At this time, the induced voltage generated in the drive coils Lu, Lv, and Lw is Ea, the coil resistance is Rm, and the saturation voltage of the drive transistor is Vsa.
t, the voltage Vo generated in the drive device of the DC brushless motor is Vo=Ea+Rm* I +Vs a
t --(1). However, Vsat is the saturation voltage of the transistor (usually about 0.1 to 0.2 V) and is a value so small that it can be ignored compared to the other two terms on the right side.

Next, the operation of the speed control device indicated by the broken line A will be explained. When the rotational speed of the DC brushless motor changes due to changes in load, etc., the induced voltage Ea generated in the motor changes, and therefore the voltage Vo also changes according to the above equation (1), but this change is caused by the resistance 18. 19, and the resulting voltage is compared with a reference voltage of a reference voltage source in an error amplifier 15.
The output is amplified by transistor 16 and transmitted to power supply control transistor 17 to control output current I.

Here, the voltage value of the constant voltage circuit is Vr, the resistance values of the resistors 21.22 of the resistor voltage divider circuit are R2 and R3, and the resistance values of the resistors 13, 18, and 19 forming the bridge circuit are R1. , R゛4. R5, I, Iu.

Iv and Iw are the currents flowing through the arrow positions, V^ and V, respectively.
If B, VC, and VD are the voltage values of each part, the error amplifier 1
The voltage VO to 5 (+) input terminals is Vo=R3*Vr/(R2+R3)+Vc=R3*Vr
/(R2+R3)+I *R1・・・・・・・・・・・・
......(2). Here, the first term on the right side of equation (2) takes a constant value Es, and the second term on the right side changes in proportion to the motor current I.

On the other hand, the voltage vI of the (-) input terminals of the error amplifier 15!
From formula (1), I is Vs = R5 * V^/ (R5 + R6) - (Ea + Rm
*I +R1*I)*R5/ (R5+R6)・
(3) Since both input terminals of the error amplifier 15 are subjected to negative feedback and operate to have equal voltages, VIllI=VB.・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・ (4) becomes Ea+Rrn+kl+R1*I= Es* (R5+R6)/R5+ (R5+R6)* I *R1'R5・・・・・・(5
) relationship is obtained.

Therefore, the induced voltage Ea of the DC brushless motor is Ea=Es* (R5+R6)/R5-1*(Rm*R
5-R6*R1)/R5=46).

From this, now adjust the resistors R5, R6, and R1 to obtain Rm*R5=R6*R1...
If (7) is selected, Ea=Es*(R5+R6)/R5, and the DC brushless motor is driven so that its induced voltage Ea is always a constant voltage.

In other words, the rotation speed of the DC brushless motor is N,
If the power generation constant is Ka, then Ea=Ka*N ・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・ Since (8), the rotation speed N of the DC brushless motor is N=Es *(R5+R6)/R5/Ka −= (9
), and the DC brushless motor is not affected by the load torque and has a constant rotation speed.

The above is the operating principle of the DC brushless motor speed control device shown in FIG.

Here, in a circuit that divides the output voltage of the constant voltage circuit 14 of the speed control device by a resistor 21 and a resistor 22 to obtain a reference voltage for setting the motor rotation speed, the resistor 22 is a thermistor or the like having positive temperature characteristics. If a resistor element of If applied to a motor, the rotation speed of the motor will be increased when the temperature is high to increase the air volume of the fan motor to increase the cooling effect, and when the salt content is low, the rotation speed will be lowered to reduce the amount of air generated from the fan motor. Accordingly, it is possible to realize a fan motor with reduced noise.

Further, in the resistor voltage divider circuit, by using a transistor SW to switch the output voltage, the rotation speed of the fan motor can be switched depending on the mode of use.

Effects of the Invention According to the above explanation, according to the present invention, by controlling the terminal voltage of the DC brushless motor drive device using the speed control device of the present invention, the rotation speed of the fan motor can be controlled with an inexpensive device. It is possible to provide a speed control device for a DC brushless morph with a simple configuration, which can reduce the noise of the fan motor, increase the air volume at high temperatures, and improve performance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a speed control device for a half-wave driven DC brushless motor according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a conventional speed control device for a DC brushless motor. 1...DC power supply, 2...Rotor magnet, 3.4.5...Coil, 6.7.8...
...Drive transistor, 9.10.11, 42.4
3.44...8.・Hall element, 12...Current divider, 13.18゜19.21.22...
Resistor, 14... Constant voltage circuit, 15...
Error amplifier, 16...Transistor, 17...
...Power supply control transistor, 20... Constant current source, 31... FG pattern, 32...
・FG amplifier, 33...Schmitt circuit, 34
...Crystal oscillator, 35...Oscillation circuit,
36... Speed discretization circuit, 37...
・Error amplifier, 38...Drive amplifier, 39...
... Hall element distribution circuit, 40 ... Bridriver, 41 ... Current detection resistor, 45.46
．． 47... Motor coil, 48, 49.50.
...Upper drive transistor, 51, 52.53.
...Lower drive transistor, A...Speed control device. Name of agent: Patent attorney Haruaki Koebi and 2 others
1 1 shi , -1 1 ', , )to' 1 〉 ~! 1'11
-> 4 + 0'''z , -1 1\ 1 inch L +--δ-2--1 1's -11 ≧ 11 ・1-I 1j'1. (-6
1■ -#-Complete 1)j -:I J Company ~Lust~2 Fig. 2/32 33 ~31 $35 Erohe 34 Engineering CC 48, - 5," 53 ~ .45 ~464741 / 37 E wing' 42 43 44

Claims (3)

[Claims] (1) A position detection means for detecting the rotational position of the rotor of a DC brushless motor, a plurality of motor coils, a current distributor for distributing a current according to the output of the position detection means, and a current distributor for distributing a current according to the output of the position detection means. an output is connected to its base, its emitter is connected in common, and its collector is connected to said motor coil to drive and rotate the motor by switching the energization path to the motor coil in accordance with the output of said distributor. A DC brushless motor configured with a drive circuit device including a plurality of drive transistors, a bridge circuit including the motor coil and the drive transistor as one piece, and a power supply control transistor inserted between a power source and the bridge circuit; One terminal is connected to the power supply via a constant current source, and the other terminal is connected to a connection point between the emitters of the drive transistors and the first resistor that are commonly connected in the drive device forming the bridge circuit. comprising a constant voltage circuit and means for generating a reference voltage serving as a speed reference based on the output voltage of the constant voltage circuit, and a reference voltage proportional to the rotational speed of the DC brushless motor is generated from a detection end of the bridge circuit. A speed control device for a DC brushless motor that compares this voltage with a reference voltage and controls the power supply control transistor using the difference voltage to control the rotation speed. (2) Claim (1) characterized in that a reference voltage source having positive temperature characteristics is used as the reference voltage source to control the rotation speed of the DC brushless motor to be low when the temperature is low and high when the temperature is high. The speed control device for the DC brushless motor described above. (3) The speed control device for a DC brushless motor according to claim (1), wherein the rotational speed of the motor is switched in stages by switching the voltage value of the reference voltage source in stages using a transistor SW or the like. .