JPH02303391A - Controller for dc brushless motor - Google Patents

Abstract

PURPOSE:To protect a motor against heating by providing a PWM signal generator which includes a comparator; a full-ON detecting circuit; a duty factor signal generating circuit; and a duty factor selecting circuit which receives a PWM signal, a full-ON detection signal and a duty factor signal to selectively produce a PWM signal. CONSTITUTION:A torque signal 4 fed from an adder 11 is compared with a triangular wave signal 5 in a comparator 81 to produce a PWM wave signal 6. In a duty factor signal generating circuit 83, a magnetic pole signal (a) is converted into a unilateral signal (b) at an absolute value circuit 83a thus producing a duty factor signal (c) from a comparator 83b. An AND gate 84b receives the PWM signal 6 from the comparator 81, an output from a full-ON detection circuit 82, and the duty factor signal (c) and produces a PWM signal (e) upon detection of full-ON state. By such arrangement, the motor can be protected against heating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a DC brushless motor, and particularly to a control device for controlling the conduction angle of a power switch transistor of this tgjJa.

[Conventional technology 1 PC brushless electric II used in aerospace equipment (
Electric motors (hereinafter referred to as electric motors) are designed to have as little output margin as possible in order to be smaller and lighter.

Therefore, on the control device yl side as well, the electric current e shown in FIG.
In the characteristic diagram A-8, control is performed so as to obtain a drooping characteristic that utilizes the unique characteristics of the electric motor.

In that case, the power switch transistor of the wattage control device is in a full-on state between A-8 in Figure 6.
), the reactive current flowing through the motor increases, and the motor generates more heat.

A conventional control device for a DC brushless motor is shown in FIG. The speed command and the speed feedback signal obtained from the resolver 2 via the speed detection circuit 6a are calculated by the adder 9, and the error signal is sent from the resolver 2 to the magnetic pole detection circuit 6.
The current command value is calculated by multiplying the magnetic pole signal obtained through b by the multiplication factor X threshold 10. The current command value is calculated by the VK current feedback signal adder 11 from the current detection circuit 3 and becomes a torque signal. As shown in FIG.
The conduction of the transistor of the power switching circuit 5 is controlled via the No. 8 amplifier circuit 4. This allows the electric motor
i degrees and torque are controlled by PWM signals, in this case the controlled electrical angle is 180°. In the characteristic diagram of electric ea shown in Fig. 6, as the torque of the electric motor increases, it approaches the ARH line and the torque signal
The result is as shown in Figure (A), and the PWM signal (2) becomes as shown in (B), so that the power switch transistor is controlled to be fully on. Therefore, as shown in (c), due to the difference between the applied voltage Vu-v of the motor all and the induced voltage, an invalid part (shaded part) is generated in the electric motor 111J as shown in (d), which increases the heat generation of the motor. It becomes.

[Problems to be Solved by the Invention] The present invention provides a DC brushless motor in which reactive current does not increase and heat generation in the motor does not increase even if the torque signal of the motor increases and the power switch transistor becomes fully on. The purpose is to provide a control device.

[Measures Pi to solve the problem] The pulse width modulation signal generation circuit compares the torque signal obtained by calculating the speed feedback signal, magnetic pole detection signal, and current feedback signal with respect to the speed command with the triangular wave signal. a comparator that generates a pulse-width modulation signal using a pulse width modulation signal, a full-on detection circuit that detects the full-on state of the power switch transistor by comparing the torque signal with a predetermined reference value, and a full-on detection circuit that compares the magnetic pole detection signal with a predetermined reference value. A conduction angle signal generation circuit that generates a conduction angle signal of a predetermined electrical angle, a pulse width modulation signal, a full-on detection signal from the full-on detection circuit, and a conduction angle signal from the conduction angle signal generation circuit are input, and the full-on signal is generated. The present invention includes a conduction angle selection circuit that selects and outputs either a pulse width modulated signal with no conduction angle or with a limited conduction angle depending on the presence or absence of the conduction angle.

[Embodiment] The present invention differs from the conventional control device described above in that it generates a pulse width modulated signal [! Only the configuration of J road is different, as shown in Figure 1~ below.
An embodiment will be described with reference to FIG.

The pulse width modulation signal generation circuit 80 includes a comparator 81 , a full-on detection circuit 82 , a conduction angle signal generation circuit 83 , and a conduction angle selection circuit 84 . The full-on detection circuit 82 includes a rectifier circuit 82a, a smoothing circuit 82b, and a comparator 82c, and detects whether the power switch transistor is in the full-on state from the magnitude of the torque signal. The conduction angle signal generation circuit 83 includes an absolute value circuit 83a and a comparator 83b, and generates a signal at a predetermined conduction angle, for example, 120°. Further, the conduction angle selection circuit 84 includes an AND circuit 84a,
84b, and an OR circuit 84c, and includes a comparator 81.84b and an OR circuit 84c. A pulse width modulation signal with a limited conduction angle or a pulse width modulation signal with a limited conduction angle is generated manually from the full-on detection circuit 82 and the conduction angle signal generation circuit 83, depending on whether a full-on state is detected.
generates an unlimited pulse width modulated signal.

To explain the operation, based on the speed command, the torque signal (■) from the adder 11 is compared with the triangular wave signal (■) in the comparator 81, and the WM wave signal (Figures 5 and 8) is generated. . In the full-on detection circuit 82, as shown in FIG. 3, the torque signal is rectified by a rectifier circuit 82b and smoothed by a smoothing circuit 82b to obtain a torque DC voltage signal f representing the magnitude of torque, that is, torque peak voltage. . This torque peak voltage signal f is determined by the comparator 82c to a predetermined reference value Re f 2. For example, it is compared with a voltage slightly higher than the peak voltage of the triangular wave signal (2) of the triangular wave oscillator 7, and when the torque peak voltage signal f exceeds the peak voltage of the triangular wave signal (2), a full-on state is detected and an output signal is output.

As shown in FIG. 2, the conduction angle signal generation circuit 83 converts the magnetic pole signal ■ from the magnetic pole detection circuit 6b into a unidirectional amplitude signal ■ in an absolute value circuit 83a, and converts this into a signal ■ with a unidirectional amplitude using a comparator 83b. The electrical angle is a predetermined angle compared to the value Refl,
For example, a conduction angle signal of 120° is generated.

In the conduction angle selection circuit 84, the AND circuit 84a receives the PWM wave signal from the comparator 81 and the full-on detection circuit 82.
Since the output signal of is inverted and input, the AND circuit 84a
A PWM wave signal is output only when a full-on state is not detected.

In addition, the PWM wave signal (■) from the comparator 81, the output of the full-on detection circuit 82, and the conduction angle signal C from the conduction angle signal generation circuit 83 are input to the AND circuit 84b, so that when a full-on state is detected, conduction occurs. A PWM signal whose angle is limited to 120° is used. As a result, OR circuit 84c
When the full-on state is not detected, the PWM wave signal ■ is output, and when the full-on state is detected, the PWM wave signal is output from the base current amplifier circuit 4 to the power switch circuit 5.
In this case, the conduction of the power switch transistor is controlled. Therefore, when a full-on state is detected, motor 1
The relationship between the voltage ■u applied to , the induced voltage, and the current 1u is invalid as shown in Figure 5 (c) and (d)! There is almost no li current, and the output of the electric motor 1 can be controlled without waste.

[Effects of the Invention] Since the peak voltage of the triangular wave signal and the peak voltage of the torque signal are compared to detect the full-on state of the power switch transistor, a complicated circuit is not required as a detection circuit. Since the conduction angle of the PWM wave signal that controls the power switch transistor is limited based on this, a control device that can suppress heat generation due to reactive current of the motor can be obtained even in the case of a design that does not have sufficient margin for the output characteristics of the motor. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the control device of the present invention, and FIG.
Figures 5 to 5 are waveform diagrams for explaining the operation, Figure 6 is a diagram showing the characteristics of the electric motor, Figure 7 is a block diagram of a conventional control device, and Figures 8 to 9 are for explaining the operation. FIG. In the figure, 1. Electric motor, 2. Resolver, 3. Current detection circuit, 4. Base current amplification circuit, 5° power switch circuit, 6a, speed detection circuit, 6b. magnetic pole detection circuit, 7. Triangular wave oscillator, 80. Pulse width modulation signal generation circuit, 81. Comparator, 82. Full-on detection circuit, 83. Conduction angle signal generation circuit, 84° conduction angle selection circuit. 3rd rIA Figure 4 Figure 8 Electrical assembly Figure 9

Claims (1)

[Claims] The speed command and the speed feedback signal are calculated by an adder, the error signal and the magnetic pole detection signal are calculated by a multiplier to obtain a current command value, and this current command value and the current feedback signal are calculated by the adder. This torque signal is calculated to generate a torque signal, and this torque signal is compared with a triangular wave signal in a pulse width modulation signal generation circuit including a comparator to generate a pulse width modulation signal, and the conduction of the power switch transistor is controlled by this pulse width modulation signal. In a control device that controls the speed and torque of a DC brushless motor, the pulse width modulation signal generation circuit compares the torque signal with a predetermined reference value and the power switch transistor. a full-on detection circuit that detects a full-on state; a conduction angle signal generation circuit that compares the magnetic pole detection signal with a predetermined reference value and generates a conduction angle signal of a predetermined conduction angle; the pulse width modulation signal, the full-on detection A full-on detection signal from the circuit and a conduction angle signal from the conduction angle signal generation circuit are input, and depending on the presence or absence of the full-on signal, a pulse with either an unrestricted conduction angle or a pulse with a restricted conduction angle is generated. A control device for a DC brushless motor, comprising a conduction angle selection circuit that selects and outputs a width modulation signal.