JPH0715356Y2 - Brushless motor speed controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to control of a brushless motor, and particularly to speed control.

(B) Conventional Technology As a conventional speed control device for a brushless motor, there is a speed control device described in JP-A-58-175985. In this publication, a semiconductor electric motor (brushless motor), a semiconductor electric motor drive circuit (switching circuit), a rotational position detection sensor (position detector), a signal processing circuit, a frequency-voltage (F-V) converter (smoothing circuit), a voltage. Those with a control device were described.

In such a configuration, the signal processing circuit switches the ON / OFF state of the transistor of the semiconductor motor drive circuit based on the output of the rotational position detection sensor to maintain the rotation of the semiconductor motor. Furthermore, the output of the rotational position detection sensor is converted into a voltage level by an FV converter, and when this voltage level becomes low, it is determined that the semiconductor motor has become overloaded or locked and the rotational speed of this motor has decreased. However, the voltage control device reduces the voltage applied to the semiconductor motor to perform overload protection.

(C) Problems to be solved by the invention Although the semiconductor motor (brushless motor) control device as described above controls the voltage applied to the brushless motor based on the output of a single position detector, This is merely to prevent damage due to overload, and cannot perform stable speed control. That is, when the output of the position detector is directly smoothed by using a smoothing circuit, the output voltage of the smoothing circuit has little fluctuation with respect to changes in the rotation speed of the motor, and stable speed control is difficult, and the V- F
Similarly, it is difficult to perform stable speed control in a converter, and it is necessary to stabilize VF conversion in order to perform stable speed control, which hinders miniaturization of the controller, for example, integral molding. It was

In view of such problems, the present invention provides a speed control device capable of performing stable speed control with a simple circuit.

(D) Means for Solving the Problems A speed control device for a brushless motor according to the present invention includes a rotor having a plurality of magnetic poles on the circumference and a single position for magnetically detecting the rotational position of the rotor. A detector; a stator winding that applies a magnetic field to the rotor by energization; a switching circuit that converts the output of the position detector into a rectangular wave and then switches the energization of the stator winding based on the rectangular wave; A power supply circuit that changes the voltage applied to the stator winding, and a square wave that changes the ratio of the H-level voltage maintenance time and the L-level voltage maintenance time based on the rectangular wave obtained from the output of the position detector A waveform shaping circuit for smoothing the output voltage of the waveform shaping circuit, and a differential amplifier for comparing the output voltage of the smoothing circuit with a set voltage. It controls the power supply circuit.

(E) Action The controller of the brushless motor configured in this way is
The output of a single position detector is commonly used for switching the energization of the stator winding and for speed control, thereby achieving downsizing of the control device. Further, since the output of the position detector is shaped and smoothed after the waveform is shaped, an output voltage corresponding to the motor's time constant can be obtained and stable speed control can be performed.

(F) Embodiment An embodiment of the present invention will be described below with reference to the drawings.
(1) is a single-phase brushless motor, which internally has a rotor having a plurality of magnetic poles on the circumference, a single-phase stator winding, and an H level of the output voltage every time the rotor rotates 180 degrees. It has a position detector (2) whose voltage L level voltage changes.
(3) is a switching circuit, which has four switching transistors (4) to (7) connected in a single-phase bridge and further has two driving transistors.
When an H level voltage is applied from the comparator (8) to the switching circuit (3), the transistors (4) and (7)
Turns on, and transistors (5) and (6) turn off. When the L level voltage is applied, the transistors (5) and (6) are turned on and the transistors (4) and (7) are turned off.

The comparator (8) switches the output to the HL level voltage each time the output of the position detector (2) switches.

Reference numeral (9) denotes a waveform shaping circuit, which is a square wave having a different ratio (duty) between the maintenance time of the H level voltage and the maintenance time of the L level voltage according to the output period of the comparator (8), that is, the rotation speed of the brushless motor. Is output. This circuit configuration is composed of, for example, a timer element, and outputs an H level voltage for a certain period of time from when an H level signal is applied, and then outputs an L level voltage until the next H level signal is applied. Therefore, when the rotation speed of the brushless motor is low, the cycle of the H level voltage applied to the waveform shaping circuit (9) becomes long, and the time during which the L level voltage is output becomes long. That is, a square wave with a low duty of the H level voltage is output. Further, when the rotation speed of the brushless motor is high, the cycle of the H level voltage applied to the waveform shaping circuit (9) becomes short, and the time during which the L level voltage is output becomes short. That is, the output of the square wave has a large duty of the H level voltage.

A smoothing circuit (10) is composed of a smoothing capacitor (11) and resistors (12) and (13). This smoothing circuit (1
0) applies an output voltage corresponding to the duty obtained by smoothing the square wave output from the waveform shaping circuit (9) to the input at one end of the differential amplifier (14). A reference voltage that determines the rotation speed of the brushless motor (1) is applied to the input of the other end of the differential amplifier (14). The reference voltage and the smoothing circuit (1
The difference from the output voltage of 0) is amplified and output. The reference voltage can be changed by adjusting the variable resistor (20).

(15) is a power supply circuit, which is composed of a protection diode and a transistor (16) which operates by the output of the differential amplifier (14). This power circuit (15) is a switching circuit (3)
Is supplying power to. Reference numeral (17) is a resistor for detecting a current supplied to the switching circuit (3). When a current more than a predetermined value flows through the resistor (17), the transistor (1
8) turns ON. Therefore, the transistor (16) is off
It becomes a state. When the current flowing through the resistor (17) falls below a predetermined value, the transistor (16) is turned on again to supply power to the switching circuit (3). Thereafter, this ON-OFF is repeated to prevent a current exceeding a certain level from flowing into the switching circuit (3). (19) is a capacitor,
The power supplied to the switching circuit (3) is stabilized.

Incidentally, (21) is a capacitor, which stabilizes the DC power given from the outside, and (22) is a Zener diode, which supplies a constant voltage to the variable resistor (20).

In the controller of the brushless motor configured as described above, the switching circuit (3) switches the energization of the stator winding based on the signal output from the position detector (2) in accordance with the rotational position of the rotor. Therefore, the rotation of the rotor is maintained.

Further, the waveform shaping circuit operates according to the output change of the position detector, and outputs a square wave with a duty matched with the output cycle of the position detector. The rotation speed of the brushless motor can be controlled by comparing the voltage level obtained by smoothing this output with the voltage set by the variable resistor (20). In this way, the duty of the square wave output from the waveform shaping circuit changes according to the rotation speed of the brushless motor, so the voltage level that smooths this output changes according to the rotation speed of the brushless motor, and stable speed control can be performed. It

Furthermore, the power supply circuit that controls the power supply to the switching circuit is also commonly used to control the power supply during an overcurrent.
The control device is being downsized.

(G) Effect of the device The speed control device for a brushless motor of the present invention has a rotor having a plurality of magnetic poles on the circumference, a single position detector for magnetically detecting the rotational position of the rotor, and an energization. A stator winding that gives a magnetic field of the rotor, a switching circuit that converts the output of the position detector into a rectangular wave and then switches the energization of the stator winding based on this rectangular wave, and the stator winding A power supply circuit that changes the applied voltage; and a waveform shaping circuit that outputs a square wave in which the ratio of the H-level voltage maintenance time and the L-level voltage maintenance time changes based on the rectangular wave obtained from the output of the position detector. A smoothing circuit that smoothes the output voltage of the waveform shaping circuit and a differential amplifier that compares the output voltage of the smoothing circuit with a set voltage are provided, and the power supply circuit is controlled by the output of the differential amplifier. So fixed with a single position detector The energization switching of the subsidiary winding and the speed control of the brushless motor can be performed, and the size of the device can be reduced.

Further, by shaping the waveform of the output of the position detector, the output of the smoothing circuit can be reliably changed according to the rotation speed of the brushless motor, and stable speed control can be performed.

[Brief description of drawings]

The drawing is an electric circuit diagram of an apparatus showing an embodiment of the present invention. (1) …… Brushless motor, (2) …… Position detector,
(3) …… Switching circuit, (9) …… Wave shaping circuit, (10) …… Smoothing circuit, (15) …… Power supply circuit.

Claims (1)

[Scope of utility model registration request] 1. A rotor having a plurality of magnetic poles on its circumference, a single position detector for magnetically detecting the rotational position of the rotor, and a stator winding for applying a magnetic field to the rotor when energized. A switching circuit that converts the output of the position detector into a rectangular wave and then switches the energization of the stator winding based on this rectangular wave; a power supply circuit that changes the voltage applied to the stator winding; A waveform shaping circuit that outputs a square wave in which the ratio of the maintenance time of the H level voltage and the maintenance time of the L level voltage changes based on the rectangular wave obtained from the output of the detector, and the output voltage of this waveform shaping circuit is smoothed. A speed control device for a brushless motor, comprising: a smoothing circuit; and a differential amplifier for comparing the output voltage of the smoothing circuit with a set voltage, wherein the power supply circuit is controlled by the output of the differential amplifier. .