JPH04236191A - Speed change-over device for brushless motor - Google Patents

Abstract

PURPOSE:To provide a device for changing over the rotating speed of a cooling fan motor by a control signal. CONSTITUTION:In a speed controller for a brushless motor having a Hall element for detecting the rotor position of the motor, a plurality of phases of coils and a drive circuit for changing over the energization of the coils in response to a Hall signal, rotating speed of the motor is changing over by changing over the resistance value of a speed regulating resistor by means of a switch.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed switching device for a DC brushless motor.

0002

BACKGROUND OF THE INVENTION DC brushless motors have no brushes or commutators and are highly reliable, so they are used in various consumer and industrial equipment. For example, if such a DC brushless motor is used in a fan motor, it will have low noise and no brushes or commutator even when rotating at high speed.
A long-life and highly reliable motor can be realized.

However, when such a DC brushless motor is used as a fan motor, speed switching has not been performed in the past.

0004

[Problems to be Solved by the Invention] However, in recent years, when using a DC brushless motor as a cooling fan motor, when the equipment to be cooled is operating, the cooling fan motor rotates at high speed and has a large air volume. Requests have been made to change the speed of the cooling fan motor so that it rotates at a lower speed and produces less noise when the target equipment is on standby. Conventionally, two methods have been used: controlling the rotation speed by configuring a frequency generator (hereinafter referred to as FG) and controlling the rotation speed by rectifying the induced voltage generated in a plurality of coils. However, when controlling the speed and switching the speed using a method using FG, a multi-pole magnetized rotor magnet and an FG board with an FG pattern formed on the board are required as a frequency generator. The speed control circuit and switching circuit are also complicated and expensive, as they require a high gain amplifier circuit to detect a weak FG signal. In addition, controlling the speed by detecting the induced voltage generated in the motor coil and switching the speed is inexpensive, but the induced voltage generated in the motor coil is extremely high when switching the current. Therefore, there was a problem that it caused malfunction.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a speed switching device for a DC brushless motor that has a simple configuration and is inexpensive.

[0006]

[Means for Solving the Problems] A first invention to achieve this object includes a position detection element for detecting the rotational position of a rotor of a DC brushless motor, and a plurality of motor coils, as shown in FIG. , a DC brushless motor configured with a drive circuit device that rotationally drives the motor by switching the energization path to the coil according to the output of the position detection element;
A reference voltage source 14 is provided between the lines of the terminal A and the second terminal B of the terminal A and the two input terminals of the error detection circuit corresponding to these terminals, and the voltage between the second terminal B and the grounded third terminal C is provided. An output transistor is provided between the first terminal A and the third terminal C, a current distribution transistor is provided between the first terminal A and the third terminal C, and a current proportional to the load current flowing to the second terminal B is connected to the first terminal A. The error detection circuit detects the difference between the voltage generated between the first and second terminals and the voltage generated between the terminals of the reference voltage source 14. a control device configured to detect the current distribution and to apply the output signal to the control input terminal of the current distribution and output transistor;
A resistor 18 is provided between the first terminal A and the second terminal B, a resistor 20 is provided in parallel with the first resistor 18 via a switching transistor 19, and the control input terminal of the switching transistor is switched. In the switching device that switches the current and switches the current flowing through the resistor 13, a drive circuit device in which a drive transistor for the DC brushless motor and a plurality of motor coils are connected between the power source and the second terminal B is provided. while connected, between the power supply terminal and the first terminal A, a resistor 13 having a resistance value multiplied by a shunt ratio (K) with respect to the coil resistance of the motor,
A control circuit device that operates so that the voltage across the driving device becomes equal to the sum of the voltage across the reference voltage source 14 and the voltage across the resistor 13; and a switching circuit device that switches the value of the current flowing through the resistor 13. It consists of:

[0007] A second invention also provides a position detection element for detecting the rotational position of a rotor of a DC brushless motor as shown in FIG. A DC brushless motor consisting of a drive circuit device that rotates the motor by switching the energization path to the motor, and two inputs: a first terminal A, a second terminal B, and an error detection circuit corresponding to each terminal. A resistor 21 is provided between the terminal lines, and the second terminal B and the third terminal C are grounded.
an output transistor is provided between the first terminal A and the third terminal C, a current distribution transistor is provided between the first terminal A and the third terminal C, and a current proportional to the load current flowing to the second terminal B is connected to the first terminal B. A, and the difference between the voltage generated between the first and second terminals and the voltage generated between the terminals of the resistor 21 is detected by an error detection circuit. a control device configured to detect the output signal and apply the output signal to the control input terminal of the current distribution and output transistor, and a reference current transistor provided between the fourth terminal D and the fifth terminal E, and the fifth terminal A resistor 18 is provided between E and the third terminal C, a resistor 20 is provided in parallel with this resistor 18 via a switching transistor 19, and the control input terminal of the reference current transistor is connected to the fifth terminal. E
A reference voltage source is provided to apply a constant voltage between the fourth terminal D of the reference current transistor and the third terminal C, and the control input terminal of the switching transistor is switched to provide a constant voltage between the fourth terminal D of the reference current transistor and the third terminal C. In the switching device that switches the current between the terminals C and the voltage between the terminals of the resistor 21, a drive transistor for the DC brushless motor and a plurality of motor coils are connected between the power source and the second terminal B. A resistor 13 having a resistance value multiplied by a shunt ratio (K) with respect to the coil resistance of the motor is connected between the power supply terminal and the first terminal A to which the connected drive circuit device is connected.
a control circuit device that connects the drive device and operates so that the voltage across the drive device becomes equal to the sum of the voltages across the resistor 13 and the voltage across the resistor 21; and a switching circuit device that switches the current flowing through the resistor 21. It consists of:

[0008]

[Operation] According to the present invention, the voltage drop caused by the load current flowing through the motor coil and the voltage drop across the resistor 13 are set to be equal to each other.
This is a speed control method that keeps the rotational speed of the motor constant, and the rotational speed of the motor is changed by switching the voltage between the terminals of the resistor 13 using the switching transistor, and the speed of a DC brushless motor can be changed with a simple configuration. It can be performed.

[0009]

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.
This will be explained with reference to.

FIG. 1 shows a first embodiment in which the speed switching device of the present invention is used in a drive device and a control device for a half-wave DC brushless motor. 3, 4, and 5 are motor coils; 6, 7, and 8 are drive transistors that supply current to the coils and drive the motor; 9, 10, and 11 detect the magnetic flux of the rotor magnet to determine the rotational position of the rotor. The Hall element 12 for detection is a current divider that switches energization to the drive transistor in accordance with the output signal of the Hall element. The common connection point of the coils is connected to the output transistor 1 via the second terminal B.
7 collector. Further, a current mirror circuit is configured by the output transistor 17 and the current distribution transistor 16, and the collector of the current distribution transistor is connected to the first
It is connected to terminal A of , and connected to power supply 1 via resistor 13 . Further, a reference voltage source 14 is connected to the first terminal A, the other end of the reference voltage source 14 is connected to the + side input terminal of the error amplifier 15, and the - side input terminal of the error amplifier 15 is connected to the second terminal B. connected to. The output of the error amplifier 15 is connected to the bases of the current mirror-connected output transistor 17 and current distribution transistor 16. Also, the part surrounded by the broken line is the speed switching device, and the resistor 18
is connected between the first terminal A and the second terminal B, and the emitter of the switching transistor 19 is connected to the first terminal A.
The collector of is connected to the second terminal B via a resistor 20, and a switching signal is input to the base of the switching transistor 19.

The operation of the above configuration will be explained. The configuration other than the broken line part is a DC brushless motor drive device using a conventional three-phase half-wave drive system and its speed control device, and Hall elements 9, 10, and 11 sense the magnetic flux of the rotor magnet 2, A signal responsive to the magnetic flux is input to the current distributor 12. In the current distributor 12, the Hall element 9
, 10 and 11, the coil to be energized is determined, and the energization of the drive transistors 6, 7, and 8 is switched by the output of the coil to rotate the motor. At this time, drive coil Lu
, Lv, and Lw are Ea, the coil resistance is Rm, and the saturation voltage of the drive transistor is Vsat, then the voltage Vo generated between the power supply 1 and the second terminal B is as follows.

0012

[Math 1]

[0013] However, Vsat is a value so small that it can be ignored compared to the other two terms on the right side.

Next, the speed control device will be explained. When the rotational speed of the DC brushless motor changes due to changes in the load, the induced voltage Ea generated in the motor changes, and therefore the voltage Vo also changes according to the above (Equation 1). The output is transmitted to the output transistor 17, and the output current I
Control m. Here, the (-) side input terminal of the error amplifier 15 is connected to the second terminal to which the collector of the output transistor 12 is connected.
By connecting to terminal B of the error amplifier 15, negative current feedback is applied and both input terminals of the error amplifier 15 operate at the same voltage. Here, the voltage value of the reference voltage source 14 is Vref, the resistance value of the resistor 13 is Rt, and Ik, Im, Iu, Iv, Iw, I
Let s be the current flowing at each arrow position. Here, the current Ik is configured so that a current of 1/K of (Im+Is) always flows through a current distribution circuit connected with a current mirror, and the voltage Vin to the (+) side input terminal of the power supply
(+) is

[0015]

[Math 2]

[0016] Here, the first and third terms on the right side of (Equation 2) take constant values, and the second term on the right side changes in proportion to the motor current Im. On the other hand, the power supply Vo from the power supply (+) terminal to the (-) side input terminal of the error amplifier is (
From number 1)

[0017]

[Math 3]

Since both input terminals of the error amplifier 15 are subjected to negative feedback and operate to have the same voltage,

[0019]

[Math 4]

0020

[0021]

[Math 5]

The following relationship is obtained. Therefore, the induced voltage Ea of the DC brushless motor is

[0023]

[Math 6]

It is expressed as follows. From this, now adjust the resistance Rt,

[0025]

[Math 7]

If you select 0026,

[0027]

[Math. 8]

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,

[0029]

[Math. 9]

[0030] Therefore, the rotation speed N of the DC brushless motor is

[0031]

[Math. 10]

The DC brushless motor is not affected by the load torque and has a constant rotation speed.

Next, the speed switching device indicated by the broken line will be explained. Here, the resistance value of the resistor 18 is R1, the resistance value of the resistor 20 is R2, and the saturation voltage of the switching transistor 19 is Vsat1. Switching transistor 19
When the base signal of is OFF, the current value Is is

00
34]

[Math. 11]

It is expressed as follows. Furthermore, when the base signal of the switching transistor 19 is ON, Is is

00
36]

[Math. 12]

It is expressed as follows. From this, by turning the base signal of the switching transistor OFF or ON, the current value Is can be changed to the resistance value R1 or the resistance value R1.
2, and the rotation speed of the motor is changed according to (Equation 8). The above is the operating principle of the DC brushless motor speed switching device shown in FIG.

Next, FIG. 2 shows a second embodiment in which the speed switching device of the present invention is applied to a half-wave drive type DC brushless motor, and 2 is a rotor magnet having 2n (n is an integer) magnetic poles; 3, 4, 5 are motor coils, 6, 7
, 8 is a driving transistor that supplies current to the coil and drives the motor; 9, 10, and 11 are Hall elements that sense the magnetic flux of the rotor magnet and detect the rotational position of the rotor; and 12 is driven according to the output signal of the Hall element. This is a current divider that switches energization to transistors. A common connection point of the coils is connected to a second terminal B, and an output transistor 17
connected to the collector. Further, the output transistor 17 and the current distribution transistor 16 constitute a current mirror circuit, and the collector of the current distribution transistor 16 is connected to the first terminal A and connected to the power supply 1 via the resistor 13. Further, a resistor 21 is connected to the first terminal A, and a resistor 21 is connected to the first terminal A.
The other end of 1 is connected to the + side input terminal of the error amplifier 15,
A negative input terminal of the error amplifier 15 is connected to the second terminal B. The output of the error amplifier 15 is connected to the bases of the current mirror-connected output transistor 17 and the current distribution transistor 16, and is connected to the terminal D of the resistor 14.
is connected to the collector of the reference current transistor 22,
The base of the reference current transistor 22 is connected to the reference voltage source 14.
It is connected to the. The part surrounded by the broken line is the speed switching device, and the emitter terminal 5 of the reference current transistor 22 is connected to a resistor 18 whose other end is grounded and a resistor 20 whose other end is connected to the collector of the switching transistor 19.
connected to. The third emitter of the switching transistor 19 is connected to the terminal C, and a switching signal is input to the base of the switching transistor 19.

The operation of the above configuration will be explained. The configuration other than the broken line part is a DC brushless motor drive device using a conventional three-phase half-wave drive system and its speed control device, and Hall elements 9, 10, and 11 sense the magnetic flux of the rotor magnet 2, A signal responsive to the magnetic flux is input to the current distributor 12. In the current distributor 12, the Hall element 9
, 10, 11 is determined, and the output of the coil is used to switch the energization of the drive transistors 6, 7, 8 to rotationally drive the motor. At this time, drive coil Lu
, Lv, Lw is Ea, the coil resistance is Rm, and the saturation voltage of the drive transistor is Vsat, then the voltage Vo generated between the power supply 1 and the second terminal B is
teeth,

[0040]

[Math. 13]

[0041] However, Vsat is a value so small that it can be ignored compared to the other two terms on the right side.

Next, the speed control device 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 13). The output is transmitted to the output transistor 17, and the output current Im
control. By connecting the (-) side input terminal of the error amplifier 15 to the second terminal B to which the collector of the output transistor 17 is connected, negative current feedback is applied and both input terminals of the error amplifier 15 operate at the same voltage. do. Here, the voltage between the terminals of the resistor 21 is V1, the resistance value of the resistor 13 is Rt, and Ik, Im, Iu, Iv, Iw, and I1 are currents flowing at the arrow positions, respectively. Here the current Ik
is configured so that a current of 1/K of Im always flows through a current distribution circuit connected with a current mirror, and the voltage Vin (+) to the (+) side input terminal of the power supply is:

0
043]

[Math. 14]

[0044] However, if I1 is small enough to be ignored compared to Ik,

[0045]

[Math. 15]

[0046] Here, the first term on the right side of (Equation 15) takes a constant value, and the second term on the right side is the motor current Im.
changes in proportion to. On the other hand, the power supply Vo from the power supply (+) terminal to the (-) side input terminal of the error amplifier is (Equation 13)
Than,

[0047]

[Math. 16]

Since both input terminals of the error amplifier are subjected to negative feedback and operate to have the same voltage,

[0049]

[Math. 17]

[0050]

[0051]

[Math. 18]

The following relationship is obtained. Therefore, the induced voltage Ea of the DC brushless motor is

[0053]

[Math. 19]

It is expressed as follows. From this, now adjust the resistance Rt,

[0055]

[Math. 20]

If you select 0056,

[0057]

[Math. 21]

The DC brushless motor is driven so that its induced voltage Ea is always the voltage V1. In other words, the rotation speed of the DC brushless motor is N
, if the power generation constant is Ka,

[0059]

[Math. 22]

[0060] Therefore, the rotation speed N of the DC brushless motor is

[0061]

[Math. 23]

The DC brushless motor is not affected by the load torque and has a constant rotation speed.

Next, the operation of the speed switching device indicated by the broken line will be explained. Here, the voltage value of the reference voltage source 14 is Vref, the resistance value of the resistor 18 is R2, and the resistance value of the resistor 20 is R3.
shall be. V1, which determines the rotational speed, is determined by the current value I1 flowing through the resistor 21 if the resistance value of the resistor 21 is constant. When the base signal of the switching transistor 19 is OFF, I1 is

[0064]

[Math. 24]

It is expressed as follows. Further, when the base signal of the switching transistor 19 is ON, I1 is

00
66]

[Math. 25]

It is expressed as follows. From this, by turning the base signal of the switching transistor 19 OFF or ON, the current value I1 can be changed to the resistance value R2 or the resistance value R.
In other words, the value of voltage V1 is changed, and the rotational speed of the motor is changed. The above is the operating principle of the DC brushless motor speed switching device shown in FIG.

[0068]

As is clear from the above description, according to the present invention, by switching the control speed of the DC brushless motor using the speed switching device of the present invention, the DC brushless motor can be switched to a cooling fan motor. When the equipment to be cooled is in operation, the cooling fan motor rotates at high speed and generates a large amount of air, and when the equipment to be cooled is on standby, it rotates at low speed and produces low noise. It is possible to provide a speed switching device for a DC brushless motor having the following configuration.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a speed switching device for a half-wave drive DC brushless motor according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a speed switching device for a half-wave DC brushless motor according to a second embodiment of the present invention.

[Explanation of symbols]

1 DC power supply 2 Motor rotor 3, 4, 5 coil 6, 7, 8 Drive transistor 9, 10, 11 Hall element 12 Current divider 13, 18, 20, 21 Resistance 14 Reference voltage source 15 Error amplifier 16 Current distribution transistor 17 Output transistor 19 Switching transistor 22 Reference current transistor

Claims (2)

[Claims] 1. Means for detecting the rotational position of a rotor of a DC brushless motor, a plurality of motor coils, and driving the motor by switching the current supply path to the motor coils according to the output of the position detecting means. a DC brushless motor comprising a drive circuit device equipped with a plurality of drive transistors for rotation; and two inputs of an error detection circuit corresponding to a first terminal A and a second terminal B of the DC brushless motor. A reference voltage source is provided between the terminal lines, an output transistor is provided between the second terminal B and a grounded third terminal C, and an output transistor is provided between the first terminal A and the third terminal C. A current distribution transistor is provided, the current is configured such that a current proportional to the load current flowing through the second terminal B flows through the first terminal A, and the voltage generated between the first and second terminals and the a control device configured to detect a difference between a reference voltage of a reference voltage source and a reference voltage using an error detection circuit, and apply the output signal to a control input terminal of the current distribution and output transistor; A first resistor is provided in between, a second resistor is provided in parallel with the first resistor via a switching transistor, and the control input terminal of the switching transistor is switched so that the current flows to the first terminal A. In the switching device for switching between the power supply terminal and the first terminal B, a drive circuit device to which the drive transistor and motor coil of the DC brushless motor are connected is connected between the power supply terminal and the second terminal B; Terminal A
A third resistor is connected between the two terminals, and the voltage across the drive circuit device becomes equal to the sum of the reference voltage and the voltage across the third resistor, and the third resistor is connected by switching the switching transistor. A speed switching device for a DC brushless motor configured to switch the voltage between the terminals of a resistor. 2. A means for detecting the rotational position of a rotor of a DC brushless motor, a plurality of motor coils, and driving the motor by switching a current supply path to the motor coil according to the output of the position detecting means. A DC brushless motor configured with a drive circuit device equipped with a plurality of drive transistors for rotation, and two inputs of an error detection circuit corresponding to a first terminal A and a second terminal B of this DC brushless motor. A first resistor is provided between the terminal lines, an output transistor is provided between the second terminal B and a grounded third terminal C, and the output transistor is provided between the first terminal A and the third terminal C. a current distribution transistor is provided at the second terminal B, the current is configured such that a current proportional to the load current flowing through the second terminal B flows through the first terminal, and the voltage generated between the first and second terminals and the a control device configured to detect a difference in voltage between terminals of a first resistor with an error detection circuit and apply the output signal to a control input terminal of the current distribution and output transistor;
A reference current transistor is provided between the fourth terminal D and the fifth terminal E, a second resistor is provided between the fifth terminal E and the third terminal C, and a reference current transistor is provided in parallel with the second resistor. A third resistor is provided through a switching transistor, and a control input terminal of the reference current transistor is connected to the fifth terminal E.
A reference voltage source is provided to apply a constant voltage between the terminal C and the third terminal C, the control input terminal of the switching transistor is switched, the current of the reference current transistor is switched, and the terminal of the first resistor is switched. a switching device for switching a voltage between the power supply and the second terminal B;
A drive circuit device is connected between the DC brushless motor drive transistor and the motor coil, and a fourth resistor is connected between the power supply terminal and the first terminal A. The voltage across the device becomes equal to the sum of the voltage between the terminals of the first resistor and the voltage between the terminals of the fourth resistor, and the voltage between the terminals of the first resistor increases due to switching of the switching transistor. A speed switching device for a DC brushless motor configured to switch.