JP2767884B2 - Control device for DC brushless motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a DC brushless motor, and more particularly, to a control device for controlling the conduction angle of a power switch transistor of the motor.

[Prior Art] DC brushless motors (hereinafter referred to as “motors”) used in aerospace equipment are designed to have as small an output as possible to reduce the size and weight. For this reason, also on the control device side, in the characteristic diagram of the electric motor shown in FIG.
During this time, control is performed so as to obtain the drooping characteristic utilizing the characteristic characteristic of the electric motor. In this case, between AB in FIG. 6, the power switch transistor of the control device is in a FULL-ON state, so that the reactive current flowing through the motor increases, and the motor generates a large amount of heat.

The control device of the conventional DC brushless motor is as 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 an adder 9, and the error signal is calculated by the multiplier 10 with the magnetic pole signal obtained from the resolver 2 via the magnetic pole detection circuit 6b. The current command value is obtained. The current command value is calculated by the current feedback signal from the current detection circuit 3 and the adder 11 to become a torque signal. This torque signal is input to a pulse width modulation signal generating circuit 8 and is compared with a triangular wave signal from a triangular wave oscillator 7 in a comparator 8a to become a pulse width modulation signal (hereinafter referred to as a PWM signal) as shown in FIG. Amplifier circuit 4
The conduction of the transistor of the power switching circuit 5 is controlled via the switch. Thus, the speed and torque of the electric motor 1 are controlled by the PWM signal. In this case, the controlled electric angle is 180 °. In the characteristic diagram of the motor shown in FIG. 6, when the torque of the motor 1 increases, the torque signal approaches the line between A and B, and the torque signal increases, as shown in FIG. 9 (a). And the power switch-like transistor is controlled to the full ON state. Therefore, as shown in (c), due to the difference between the applied voltage Vu-v of the motor 1 and the induced voltage, as shown in (d), an invalid portion (shaded portion) occurs in the current Iu, and the heat generation of the motor increases. The cause is.

[Problems to be Solved by the Invention] The present invention relates to a DC brushless motor in which the reactive current does not increase and the heat generation of the motor does not increase even when the torque signal of the motor increases and the power switch transistor is turned on. It is an object to provide a control device.

[Means for Solving the Problems] A pulse width modulation signal generating circuit compares a torque signal obtained by calculating a speed feedback signal, a magnetic pole detection signal, and a current feedback signal with respect to a speed command with a triangular wave signal. A comparator that generates a pulse width modulation signal; a full-on detection circuit that compares the torque signal with a predetermined reference value to detect a full-on state of the power switch transistor; and compares a magnetic pole detection signal with a predetermined reference value. A conduction angle signal generation circuit for generating a conduction angle signal having a predetermined electrical angle, a pulse width modulation signal, a full on detection signal from a full on detection circuit, and a conduction angle signal from the conduction angle signal generation circuit; If there is no signal, the pulse width modulation signal is output as it is, and if there is a full ON signal, the pulse width modulation signal is output only during the conduction angle indicated by the conduction angle signal. A conduction angle selection circuit configured as described above is provided, and conduction of the power switch transistor is controlled by a pulse width modulation signal output from the conduction angle selection circuit.

[Embodiment] The present invention is different from the above-described conventional control device only in the configuration of the pulse width modulation signal generation circuit. Hereinafter, an embodiment will be described with reference to FIGS.

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,
It includes a smoothing circuit 82b and a comparator 82c, and detects whether or not the power switch transistor is in a 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 has a predetermined conduction angle, for example, 120
゜ Generate a conduction angle signal. In addition, the conduction angle selection circuit 84
Includes AND circuits 84a and 84b and an OR circuit 84c,
1, according to whether the full-on state is detected by input from the full-on detection circuit 82 and the conduction angle signal generation circuit 83,
A pulse width modulation signal having a limited conduction angle or a pulse width modulation signal having an unlimited conduction angle is generated.

In operation, the torque signal from the adder 11 based on the speed command is compared with the triangular wave signal by the comparator 81 to generate a PWM wave signal (FIGS. 5 and 8). In the full-on detection circuit 82, as shown in FIG. 3, the torque signal is rectified by the rectification circuit 82a and smoothed by the smoothing circuit 82b to obtain the torque DC voltage signal f representing the magnitude of the torque, that is, the torque peak voltage. Can be The torque peak voltage signal f is compared in the comparator 82c with a predetermined reference value Ref2, for example, a voltage slightly higher than the peak voltage of the triangular wave signal of the triangular wave oscillator 7, and the torque peak voltage signal f exceeds the peak voltage of the triangular wave signal. At this time, the full ON state is detected and an output signal is generated.

The conduction angle signal generation circuit 83 converts the magnetic pole signal from the magnetic pole detection circuit 6b into a signal of one-way amplitude in the absolute value circuit 83a as shown in FIG. Electrical angle is a predetermined angle, for example, 120
A conduction angle signal of ゜ is generated.

In the conduction angle selection circuit 84, the AND circuit 84a includes a comparator.
Since the PWM wave signal and the output signal of the full-on detection circuit 82 are inverted and input from 81, the PWM circuit signal is output from the AND circuit 84a only when the full-on state is not detected. Further, the PWM wave signal from the comparator 81, the output of the full-on detection circuit 82, and the conduction angle signal from the conduction angle signal generation circuit 83 are input to the AND circuit 84b. A PWM signal limited to 120 ゜ is output. As a result, a PWM wave signal is output from the OR circuit 84c when the full ON state is not detected, and a PWM wave signal is output when the full ON state is detected. The power switching transistor 5 is supplied to the power switching circuit 5 through the base current amplifier circuit 4. Is controlled. For this reason, when the full-on state is detected, the relationship between the voltage Vu applied to the motor 1, the induced voltage, and the current Iu is such that the motor 1 has almost no reactive current as shown in FIGS. 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 for detecting the full-on state of the power switch transistor, a complicated circuit is not required as a detection circuit. In addition, since the conduction angle of the PWM wave signal that controls the power switch transistor based on the detection of the full-on state is limited, it is possible to suppress the heat generation due to the reactive current of the motor even in the case of a design where the output characteristics of the motor have no margin. Thus, a control device capable of performing the following operations is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a control device according to the present invention, and FIG.
5 to 5 are waveform diagrams for explaining the operation, FIG. 6 is a diagram showing characteristics of the electric motor, FIG. 7 is a block diagram of a conventional control device, and FIGS. 8 to 9 are diagrams for explaining the operation. FIG. In the drawing, 1 ... 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 …… Triangle 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.

Claims (1)

(57) [Claims] A speed command and a speed feedback signal are calculated by an adder, an error signal and a magnetic pole detection signal are calculated by a multiplier to obtain a current command value, and the current command value and the current feedback signal are calculated by an adder. A pulse width modulation signal including a comparator is compared with a triangular wave signal to generate a pulse width modulation signal, and the pulse width modulation signal controls the conduction of the power switch transistor. A control device for controlling the speed and torque of the DC brushless motor, wherein the pulse width modulation signal generation circuit compares the torque signal with a predetermined reference value, and fully turns on the power switch transistor. A full-on detection circuit for detecting a state, and a conduction angle signal generation for generating a conduction angle signal of a predetermined conduction angle by comparing the magnetic pole detection signal with a predetermined reference value And road, the pulse width modulated signal, full-on detection signal from the full-on detection circuit, and enter the conduction angle signals from the conduction angle signal generating circuit, when the full-on signal is present,
A conduction angle selection circuit configured to output the pulse width modulation signal as it is, and to output the pulse width modulation signal only during a conduction angle indicated by the conduction angle signal when the full-on signal is present; A control device for a DC brushless motor, wherein conduction of a power switch transistor is controlled by a pulse width modulation signal output from an angle selection circuit.