JPH05260784A - Driving device for brushless motor - Google Patents

Abstract

PURPOSE:To provide a low-cost driver of brushless motor for controlling the number of revolutions by simple circuit constitution. CONSTITUTION:The title apparatus has an inverter 2 connected with a plural- phase armature winding 1a for driving a brushless motor 1 composed of the plural-phase armature winding 1a and a permanent magnet rotor 1b by supplying the brushless motor with DC current and also has a control circuit 5 for successively switching the switching transistor of the inverter 2 by a drive signal 42 on the basis of the position of the permanent-magnet rotor 1b. Further, the apparatus is equipped with a current detector 30 for detecting DC current flowing to the inverter 2, a speed control circuit 8 for indicating the value of DC current to be supplied to the brushless motor 1, a comparator 31 for comparing a DC current value detected by the current detector 30 with that indicated by the speed control circuit 8 and a power-application controller 32 for switching the application of DC current to the brushless motor 1 by controlling the power application to the drive signal on the basis at a comparison result by the comparator 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving device.

[0002]

2. Description of the Related Art In recent years, brushless motors have been increasingly used for various drive motors because of their long life, high reliability and maintenance-free operation. The brushless motor is characterized in that the applied voltage and the number of revolutions are substantially proportional to each other. Therefore, the speed can be controlled by controlling the applied voltage.

Conventionally, as a method of performing voltage control, P
AM (pulse Amplitude Modulate) method, PWM (Puls
e Width Modulate) method is used. Hereinafter, each method will be described with reference to the drawings.

FIG. 2 shows the structure of a drive circuit for a brushless motor using the PAM method. In FIG. 2, the brushless motor 1 has an armature winding 1a in which three phases are connected.
And a permanent magnet rotor 1b. The inverter 2 has 6
It consists of individual switching transistors. Converter 3
Rectifies the AC power supply 4 and converts it into direct current. The voltage control unit 20 converts the current from the converter 3 into a predetermined voltage according to an instruction (voltage control signal 44) from the control circuit 5,
Supply to the inverter 2.

The control circuit 5 comprises an energization switching circuit 6, a position detection circuit 7, and a speed control circuit 8. The position detection circuit 7 is a permanent magnet rotor 1 output from a position / speed detector 9 connected to the brushless motor 1.
A rotor position signal 40 indicating the rotational position of b is input. The speed control circuit 8 inputs the speed signal 41 output from the position / speed detection device 9 and indicating the speed of the permanent magnet rotor 1b. The position detection circuit 7 determines the energized position from the rotor position signal 40, and the inverter 2 via the energization switching circuit 6.
The drive signal 42 for driving the switching transistor is output. The speed control circuit 8 compares the speed signal 41 with the rotation speed command signal 43 given from the outside, and sends the voltage control signal 44 to the voltage control unit 20 according to the comparison result.
Is output.

In the drive circuit of the PAM system, when the detected rotation speed is lower than the rotation speed command value indicated by the rotation speed command signal 43, the voltage control unit 20 raises the voltage, and when it is high, the voltage is lowered to lower the voltage. The rotation speed of 1 is controlled. That is, the PAM method controls the rotation speed by changing the DC power supply voltage.

FIG. 3 shows the structure of a brushless motor using the PWM method. Since the basic configuration in FIG. 3 is the same as that of the PAM system shown in FIG. 2, the same parts are designated by the same reference numerals and the description thereof will be omitted.

In the PWM system, the speed control circuit 8 controls the energization time width in one cycle of the carrier frequency. The speed control circuit 8 issues a command to increase the energization time width (on width) when the detected rotation speed is lower than the rotation speed command value and to decrease the conduction time field (on width) when the detected rotation speed is higher than the PWM on width control circuit 21. Output to. The PWMon control circuit 21 generates a carrier frequency and controls the on width according to a command from the speed control circuit 8.

In the PWM drive circuit, the peak value of the applied voltage is a value determined by the DC voltage obtained from the converter 3, and the rotation speed control is performed by adjusting the average voltage from the ratio of the on time and the off time of the energization section. It is carried out.

[0010]

As described above, in the PAM method used in the conventional driving device, the voltage control unit 20 is used.
Thus, the rotation speed control is performed by changing the DC power supply voltage from the converter 3. Therefore, a large-capacity transistor, a reactor, a capacitor, etc. are required to configure the voltage control unit 20.

Further, in the PWM system, the rotation speed is controlled by adjusting the average voltage from the ratio of the on time and the off time of the energization section. For this reason, it is necessary to provide a high-speed timer and perform high-speed calculation for on / off control of the PWMon width control circuit 21 and the transistor, and thus a high-performance CPU or peripheral circuit is required.

As described above, the conventional PAM method and PWM
In the drive circuit using the method, there is a problem that the circuit for controlling the voltage is expensive and the cost becomes high.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an inexpensive brushless motor drive device for controlling the rotation speed with a simple circuit configuration.

[0014]

DISCLOSURE OF THE INVENTION The present invention is connected to an armature winding for driving a brushless motor comprising a plurality of phase armature windings and a permanent magnet rotor by supplying a direct current to the brushless motor. In a drive device of a brushless motor having a plurality of driving switching transistor groups and a control circuit that sequentially switches the driving switching transistors based on the position of the permanent magnet rotor by a driving signal, Current detection means for detecting a flowing direct current value, speed control means for instructing a direct current value to be supplied to the brushless motor, direct current value detected by the current detection means and the speed control means Comparing means for comparing the direct current value and the comparison result by the comparing means, The energization of DC current to the brushless motor by controlling the energization of the drive signal on / o
energization control means for turning off the electric current, the energization control means turning off energization while the current value detected by the current detection means by the comparison means exceeds the current value instructed by the speed control means. The rotation speed of the brushless motor is controlled by.

[0015]

According to this structure, the energization is turned off when a current larger than the command current value from the control circuit flows, and the command current value is lowered when the detected rotation speed is higher than the command rotation speed. If it is low, the rotation speed of the brushless motor is controlled by increasing the command current value.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of a brushless motor driving device according to the embodiment. Since the basic configuration of the drive device shown in FIG. 1 is the same as that of the PWM system shown in FIG. 3, the same parts are designated by the same reference numerals and the description thereof will be omitted. The configurations of the brushless motor 1, the inverter 2, the converter 3, the AC power source 4, and the position / speed detector 9 shown in FIG. 1 are the same as the configurations of the drive device based on the PWM method.

In the drive device of the embodiment, the current detector 30 and the current detector 30 are provided between the converter 3 and the inverter 2.
And a speed control circuit 8 are provided with a comparator 31, and an energization switching circuit 6 and an inverter 2 are provided with an energization controller 32.

The current detector 30 detects a direct current flowing from the converter 3 to the inverter 2 and outputs a current detection signal 35 corresponding to the current value to the comparator 31. Comparator 31
Is a current command signal 36 output from the speed control circuit 8.
And the current detection signal 35 from the current detector 30 are compared, and the energization off signal 35 or the energization on signal 38 is output to the energization controller 32 according to the comparison result. The energization controller 32 uses the energization off signal 35 or the energization on signal 38.
According to the above, the energization of the drive signal 42 from the energization switching circuit 6 is controlled.

The position detection circuit 7 inputs the position detection signal 40 from the position / speed detector 9 to determine the phase to be energized,
Drive signal 4 to transistor by energization switching circuit 6
2 is output. The speed control circuit 8 includes a position / speed detector 9
The speed signal 41 from is compared with the rotation speed command signal 43, and the current command signal 36 is output to the comparator 31 according to the comparison result.

The current detection signal 35 detected by the DC current detector 30 is compared with the current command signal 36 by the comparator 31. As a result of the comparison, when the current detection signal 35 is large, the comparison device 31 outputs the energization off signal 38 to the energization controller 32. In this case, the energization controller 3
No. 2 turns off the power even if the drive signal 45 is on. As a result, no current flows and the detected current value is the current command signal 3
When the number is 6 or less, the energization on signal 37 is output from the comparator 31, and the energization controller 32 energizes. By repeating this, the current can be maintained at the value of the current command signal 36 by controlling the on / off of energization.

Next, a method of controlling the rotation speed will be described.
In order to increase the rotation speed from the current rotation speed, the current command signal 36 is raised to slightly increase the amount of current flowing to the brushless motor 1. Then, since the generated torque of the brushless motor 1 increases, the brushless motor 1 accelerates.

When the rotational speed of the brushless motor 1 increases, the generated induced voltage becomes large and the current becomes difficult to flow. However, as described above, in the configuration of the present invention, energization is continued until the value of the current command signal 36 is reached. .. As a result, the energization time becomes long and the average voltage rises, so the rotation speed also rises. When the rotation speed reaches the command value, the current command signal 36 is lowered so as to maintain the rotation speed indicated by the rotation speed command signal 43, and when the rotation speed has settled down, the current command signal 3
The value of 6 may be determined.

On the contrary, when the number of rotations is reduced, the current command signal 36 can be slightly reduced to achieve the same effect. In the present invention, the average voltage is controlled in this way to realize the rotation speed control.

In this way, the energization of the drive signal 42 is turned off when a current larger than the value indicated by the current command signal 36 flows, and the detected rotation speed is the rotation speed command signal 43.
When the rotation speed is higher than the command rotation speed, the rotation speed of the brushless motor 1 is controlled by lowering the value of the current command signal 36 and raising the value of the command current signal 36 when the rotation speed is lower. Therefore, an inexpensive driving device can be realized because a voltage control unit that requires a large capacity transistor, a reactor, a capacitor, and the like, and a high-performance CPU or a peripheral circuit are not required.

Although the sensor type connected to the rotary shaft is used as the speed / position detector 9 in the above embodiment,
A sensorless type configuration for detecting the position of the permanent magnet rotor 1b from the terminal voltage and line current of the sensorless motor 1 may be used. In addition, the energization switching circuit 6, the position detection circuit 7,
The speed control circuit 8, the comparison device 31, and the energization control device 32 are
It is possible to use a part of the internal function of the one-chip microcomputer, or it may be configured as an external circuit.

[0026]

As described above, according to the present invention, the energization is turned off when a current larger than the command current value from the control circuit flows, and the command is issued when the detected rotation speed is higher than the command rotation speed. Since the rotation speed of the brushless motor is controlled by decreasing the current value and increasing the command current value when the current value is low, an inexpensive brushless motor drive device that controls the rotation speed with a simple circuit configuration is provided. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a drive device for a brushless motor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a drive circuit of a brushless motor using a PAM method.

FIG. 3 is a block diagram showing a circuit configuration of a drive circuit of a brushless motor using a PWM method.

[Explanation of symbols]

1 ... Brushless motor, 2 ... Inverter, 3 ... Converter, 4 ... AC power supply, 5 ... Control circuit, 6 ... Energization switching circuit, 7 ... Position detection circuit, 8 ... Speed control circuit, 9 ... Position /
Speed detection circuit, 30 ... Current detector, 31 ... Comparator, 32
… Energization controller.

Claims (1)

[Claims] 1. A plurality of driving switching transistors connected to the armature winding for driving a brushless motor including a plurality of phase armature windings and a permanent magnet rotor by supplying a direct current. In a brushless motor drive device having a group and a control circuit that sequentially switches the drive switching transistors based on the position of the permanent magnet rotor by a drive signal, a current for detecting a DC current value flowing to the drive switching transistor group. Detection means, speed control means for instructing a direct current value to be supplied to the brushless motor, and comparison for comparing the direct current value detected by the current detection means with the direct current value instructed by the speed control means. Means, and controlling the energization of the drive signal based on the comparison result by the comparison means. Drive device for a brushless motor, characterized by comprising a energizing control means for on / off energization of the direct current to the brushless motor by Rukoto.