JPS6181191A - Brushless motor drive circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Q Ming's Technical Field] The present invention relates to a brushless motor drive circuit that rotationally drives a DC motor based on a magnetic detection signal obtained from a non-contact magnetic detection element.

[Technical Background of the Invention] Conventionally, DC motors include brushed motors having a mechanical commutation mechanism and brushless motors using electronic switches. Although the brushed motor is relatively low cost, it improves the reliability of the commutating R structure, and
It has the disadvantage of generating noise. For this reason, recently, the use of brushless motors, which are high in cost but have high reliability and low noise, has been expanding.

FIG. 3 is a circuit diagram showing an example of a conventional brushless motor drive circuit. The Hall element 1.2.3 detects magnetic changes in the rotor magnet (not shown) without contact, and outputs the obtained detection signal to the comparators 4, 5.6. The detection signals input to the comparators 4 and 56 are shaped here and then input to the current switching circuit (logic circuit) 7.

The current switching circuit 7 determines a status coil (hereinafter simply referred to as a coil) to which a current flows based on the input detection signal, and sends a signal instructing to cut off current to each coil to the drivers 8 to 1.
3 to the base of one of the transistors 14-1. One of the transistors 14, 16, and 18 that controls the current cutoff of the coil is activated by the current cutoff instruction signal.
Apply current to the center O of the wiring coils 20, 21, and 22,
One of the transistors 15.17.1 conducts current from the center O of the Y-connected coil 20.21.22 to GND. By sequentially performing such operations based on the detection signals of Hall elements 1 to 3, the rotor of the motor rotates at I
l! Continue.

In FIG. 4(A), the Hall element 1.2.3 is connected to the coil 20.
21. Glide phase of the rotating magnetic field formed in 22.

Comparator 4, when dealing with ■phase and W phase,
5.6 shows the input waveform (magnetic change detection signal). FIG. 4(B) is a waveform diagram of the current cutoff signal outputted via the drivers 8 to 13 by the current switching circuit 7 which receives the detection signal shown in FIG. 4(A). Here, the numbers on the left correspond to the numbers on the driver. Figure 4 (C) is the fourth
Turn on and off transistors 14 to 19 based on the output signal waveform shown in Figure (B)
, 22 are shown. Incidentally, the coils 20°21.22 correspond to the U phase, ■ phase, and W phase, respectively. In the end, the comparator 4°5. shown in FIG. 4(A).
6 input waveform (U, V, W phase magnetic change detection signal waveform)
As shown in Fig. 4(C), a current with approximately the same waveform as the
A rotating magnetic field is generated in the coils 20, 21° 22 by flowing into the coils 2° 21 and 22 corresponding to the ■ and W phases,
The rotation of the rotor of a motor (not shown) is continued.

[Problems in background technology] By the way, the torque T of a DC motor is the magnetic flux density B.

When the armature current I and the effective length of the armature conductor are set to 1, it is thought that it occurs according to the BIf side.
It has something to do with TiBIQ. Considering this relationship, B, 1
．． i! If both are uniform, the generated torque will also be uniform, but the magnetic flux density B generated in the status coil by the field magnet has a sinusoidal waveform as shown in FIG. 5 due to the relationship between magnetization and magnetic path. Therefore, as shown in FIG. 5, even if the current I is constant, the torque T changes as the magnetic flux density B changes. In addition, the effective length of the amateur conductor shall be constant. Therefore, when a DC brushless motor is applied to something that requires very strict conditions for rotational unevenness and torque unevenness, the torque unevenness becomes a problem and it is necessary to reduce it.

Conventionally, as a countermeasure to reduce this torque unevenness, instead of saturation magnetization of the magnets that make up the main magnetic field, special magnetization, such as comb-shaped magnetization, or shifting the switching timing of each coil phase has been used. However, there has been no method for reducing the torque unevenness while maintaining the general magnetization and switching timing without using such a special method.

[Objective of the Invention] The object of the present invention is to solve the above-mentioned disadvantages 1. In view of the above, it is an object of the present invention to provide a brushless motor drive circuit that can reduce torque unevenness without special magnetization or shifting the timing of current switching to each phase of the stator coil.

[Summary of the Invention] The present invention generates an energization instruction signal that instructs energization to a stator coil in a certain sequence in a method of Nrc rotation of a motor based on a magnetic detection signal obtained from a non-contact magnetic detection element. In the brushless motor drive circuit, the brushless motor drive circuit is composed of a logic circuit that causes the magnetic detection signal or the energization instruction to be activated, and an additional impedance added to the impedance of the stator coil is provided, and an additional impedance is provided to be added to the impedance of the stator coil. An impedance control signal is generated that is delayed by a certain period of time from the signal, and this control signal is used to apply a current change to the stator coil that cancels the torque ripple occurring between the stator coil and the motor. The above object is achieved by using the R4 configuration that turns on and off the additional impedance.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings, in which the same parts as those of the conventional example are given the same reference numerals. FIG. 1 is a circuit diagram showing an embodiment of the brushless motor drive circuit of the present invention. After the magnetic change detection signal detected by the Hall element 1.2.3 is waveform-shaped by the comparators 4 and 5.6,
The current is input to the current switching circuit 7. The current switching circuit 7 determines the stator coil through which the current flows based on the input magnetic change detection signal, and based on this, the current switching circuit 7 determines the stator coil through which the current flows.
,: Outputs a de-energization instruction signal that instructs de-energization of the coil. Energization cutoff instruction signals output from drivers 8-13 are applied to the bases of transistors 14-19.

A driving voltage VCC is applied to the collectors of the transistors 14, 16 and 18, the emitter of the transistor 14 and the collector of the transistor 15 are connected to one end of the coil 20, and the emitter of the transistor 16 and the collector of the transistor 17 are connected to one end of the coil 21. connected, transistor 1
The emitter of transistor 8 and the collector of transistor 19 are connected to coil 2.
Also, the transistors 15,
The emitters of 17 and 19 are grounded via an additional impedance 55.

On the other hand, each energization cutoff instruction signal outputted from the drivers 8 to 13 is transmitted to the capacitor 23 and the resistor 24. Capacitor 25 and resistor 26. Capacitor 27 and resistor 28. 2 capacitors and 30 resistors. Capacitor 31 and resistor 32. The output signals of these differentiating circuits are inputted to a differentiating circuit composed of a capacitor 33 and a resistor 34, and the output signals of these differentiating circuits are connected to diodes 35 and 36.
, 37°, 38.39.40 and a resistor 50, respectively. The output signal output from this OR circuit is input to a waveform shaping circuit 51, where the waveform is shaped, and then delayed by a delay circuit 52 for a certain period of time.Then, the duty is determined by a mono multivibrator 53, and the control transistor 54 base. This control transistor 54 is connected in parallel to the additional impedance 55.

Next, the operation of this embodiment will be explained. Hall element 1,
The magnetic change detection signal of the rotor magnet detected by 2.3 is waveform-shaped by a comparator 4.5.6 and then input to the current switching circuit 7. The current switching circuit 7 outputs a current cutoff instruction signal to the coils 20, 21 and 22 to each of the drivers 8 to 13 based on the manually inputted magnetic change detection signal. Figure 2 shows this driver 8
13 shows the output waveform of the above-mentioned energization cutoff instruction signal. Here, the numbers 8 to 13 on the left side indicate the driver numbers. Driver 8.10.12
As shown in the figure, the output signals of transistors 14, 16, and 18 are at a high level with a 120 degree shift, so
They are turned on with a shift of 0i, and a current flows through the coils 20, 21, and 22 to the Y-connection center 0 of these coils with a phase difference of 120 degrees. Also, driver 9.11
The output signal of ゜13 is also <1201f as shown in Fig. 2.
Since the transistors turn on at different times, the transistor]5°17.
19 are turned on in order with a phase difference of 120 degrees, respectively, to control the current from the Y-connected coil hinter 0 to flow through the coils 20, 21, and 22 to GND. As a result, a rotating magnetic field is generated in the coils 20.degree. 21.22, and the rotor of the motor (not shown) continues to rotate due to this rotating magnetic field.

On the other hand, the output signals of the drivers 8 to 13 shown in FIG. Capacitor 25 and resistor 2
6. capacitor 27 and resistor 28 capacitor 29 and resistor 30. Capacitor 31 and resistor 32. capacitor 33
and a resistor 34, and this differential signal is logically summed by an OR circuit composed of diodes 35 to 4o and a resistor 5o. Therefore, the output signal of the OR circuit becomes a pulse that captures the rising edge of the signals output from the drivers 8 to 13, and this is waveform-shaped by the waveform shaping circuit 51 to become as shown in (51) in FIG. The output of this waveform shaping circuit 51 is then delayed by a delay circuit 52 for a certain period of time, and then passes through a mono multivibrator 53 that gives a predetermined duty, so that the output has a certain delay time as shown in FIG. 2 (53). It becomes a pulse signal with a constant duty. Since the control transistor 54 is turned on and off by the output pulse of the mono-multivibrator 53, the G
The NDM current flows either through the additional impedance 55 or through the control transistor 54. Therefore, when the control transistor 54 is on, the current flowing through either of the coils 20, 21, 22 becomes large, and conversely, when the transistor 54 is off, the current flowing through either of the coils 20, 21, 22 becomes large. The current flowing through these coils 20.21.2-2 changes so that it becomes smaller. The waveform shown in the lower part 1c of FIG. 2 shows the change waveform of the current flowing through this coil, and this current change appropriately sets the delay time of the delay circuit 52 and the duty given by the mono-multivibrator 53. This is intended to counteract ripples in torque generated due to changes in magnetic flux density. Therefore, the torque generated between the motor rotor and the coils 20, 21, 22 is approximately constant.

According to this embodiment, an additional impedance 55 is added to the impedance created by the stator coils 20.2122, and this impedance 55 is turned on and off by the control transistor 54, so that the stator coils 20.21.
The current flowing through 22 can be changed so as to cancel out the change in magnetic flux density, and torque unevenness can be significantly reduced while a constant driving voltage VCC is applied. Furthermore, since the switching timing of the special magnetizing current switching circuit 7 for the rotor is not shifted, the torque unevenness can be reduced easily and at low cost.

[Effects of the Invention] As described above, according to the brushless motor drive circuit of the present invention, an additional impedance is provided to the impedance of the stator coil, and this additional impedance is turned on and off by a control signal generated from a magnetic detection signal or a coil pass/cut signal. By changing the current flowing through the stator coil to compensate for changes in magnetic flux density, torque unevenness can be reduced without shifting the timing of current switching to each phase of the special magnetized Yaschita coil. There is an effect that can reduce the

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the brushless motor drive circuit of the present invention, Fig. 2 is an operation waveform timing diagram of the circuit shown in Fig. 1, and Fig. 3 is an example of a conventional brushless motor drive circuit. Circuit diagram showing. Figure 4 is an operation waveform timing diagram of the circuit shown in Figure 3.
FIG. 5 is a waveform diagram showing the relationship among magnetic flux density, current, and torque of the brushless motor driven by the circuit shown in FIG. 3. 1.2,3...-Hall element 7.-Current switching circuit 1
4 to 19...-Transistors 20, 21, 22...-Stator coil 51...-Waveform shaping circuit 52...-Delay circuit 53...Mono multivibrator 54--Control transistor 55...Additional impedance agent Patent attorney Shi Nori Chika Kensuke Figure 1 Figure 2

Claims (1)

[Claims] A non-contact magnetic detection element that detects magnetic changes in the rotor magnet, and a current cutoff instruction signal that instructs to cut off current to the stator coil in a certain sequence in the direction of continuing rotation of the rotor based on this magnetic change detection signal. an additional impedance added to the impedance created by the stator coil; a control signal generation circuit that receives the magnetic change detection signal or the current cutoff instruction signal and generates a control signal that is generated at a timing delayed by a certain time from the input signal and has a certain duty; A brushless motor drive circuit comprising an additional impedance on/off circuit that turns on and off an additional impedance.