JPH1028393A - Controller for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate high precision control with suppressed noise fluctuation at a low cost. SOLUTION: A noise-reducing capacitor C, whose one end is connected to the connection point of the input terminals of position detectors Hu, Hv and Hw, and a bias resistor r1 on a Vcc power voltage side and whose other end is connected to the ground potential, is provided and the noise fluctuation is suppressed by the stored charge effect of the capacitor C, even if noises produced by the switching of current application to driving coils or external noises are applied to the power supply lines of the position detectors Hu, Hv and Hw, and further, by connecting the capacitor C to the bias resistor r1 in series, the charge of the capacitor C can be quickly discharged, so that a small capacity capacitor can be employed for the capacitor C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for a brushless motor.

[0002]

2. Description of the Related Art FIG. 4 shows a schematic configuration of a brushless motor, which comprises a stator X,
It includes a rotor Y and three position detectors Hu, Hv, Hw. The stator X is energized back and forth in the positive and negative directions.
The rotor Y has a plurality of magnetic poles Z arranged opposite to the drive coils Lu, Lv, Lw. Further, the position detector Hu,
Hv and Hw are arranged at positions shifted by 120 ° in electrical angle and include, for example, three Hall elements.

[0003] As a system for driving this brushless motor, a so-called hard switching energizing system (3-phase 120 °) is used.
FIG. 5 shows a drive circuit section of a brushless motor adopting the hard switching energization method.

In FIG. 1, Hall elements Hu, Hv, Hw as position detectors are connected in parallel, and Vc
Hall elements Hu and H connected in parallel with the c power supply voltage.
A bias resistor r1 on the power supply voltage side is provided between the input terminals v and Hw of the power supply voltage side, and a bias resistor r1 on the power supply voltage side is provided between the ground voltage side input terminals of the Hall elements Hu, Hv and Hw connected in parallel. The bias resistors r2 on the ground voltage side are connected in series. These bias resistors r1 and r2 are
For adjusting the input sensitivity.

The Hall elements Hu, Hv, Hw generate three-phase sinusoidal output signals (voltage waveforms) in accordance with the rotation of the rotor Y facing the three-phase drive coils Lu, Lv, Lw. , This output signal is supplied to an amplifier (differential amplifier) R,
The signal is applied to the signal synthesis circuit SM via S and T. The signal synthesizing circuit SM is digitally constituted by a logic circuit, detects a zero-cross point at which the output signals of the amplifiers R, S, and T become 0 V, and outputs a three-phase 120 ° switching waveform signal (rectangular wave pulse). Power element (switching element group) Q
31 to Q36 constitute a final stage driver, and a current flows through the three-phase driving coils Lu, Lv, Lw by the three-phase 120 ° switching waveform signal from the signal combining circuit SM, and as a result, the rotor Y Rotate. At this time, the current flowing through the drive coils Lu, Lv, Lw is the current detection resistor R
s.

[0006] Any one of the Hall elements Hu, Hv, Hw (in the drawing, the Hall element H
For example, a comparator (for forming an FG signal) P as a converter is connected to the output terminal of u).
6A, an FG signal (speed detection signal) as shown in FIG. 6A is obtained, and the FG signal is converted into a FG signal by a predetermined circuit (not shown) as shown in FIG. Is compared with a predetermined threshold voltage Vs so that FV
The conversion is performed, and the speed command voltage VCTL is obtained.

A control amplifier (control comparator) shown in FIG.
A41 extracts the difference between the obtained speed command voltage VCTL and the reference voltage VREF as a current command voltage, and the current feedback amplifier A42 outputs the difference between the current command voltage and the voltage of the current detection resistor Rs. . Then, the signal synthesis circuit SM is controlled by the output signal of the current feedback amplifier A42 to change the output signal voltage. The filter capacitors Cu, Cv and Cw are connected to the drive coils Lu and L, respectively.
This is a capacitor provided to reduce mechanical noise and electrical noise generated due to a sudden change in current when the current is switched between v and Lw.

That is, in the circuit shown in FIG. 5, the amplifiers R, S, T, the signal combining circuit SM, the power element Q31
To Q36, a current detection resistor Rs, a comparator P, a control amplifier A41, a current feedback amplifier A42, etc., and the drive circuit 1 is configured to control the energization of the drive coils Lu, Lv, Lw.

[0009]

However, the above apparatus has the following problems. That is, in the above-described device, noise is generated when the energization of the drive coils Lu, Lv, Lw is switched, and this noise is generated by the Hall elements Hu, Hv, Hw
Therefore, there is a problem that the control of the subsequent stage cannot be performed with high accuracy because the power line is used. Such a problem may be caused not only by the noise caused by the switching of the energization of the drive coils Lu, Lv, and Lw but also by external noise.

In particular, the FG based on the Hall element output
In the case of obtaining a signal, the FG signal is disturbed due to the noise and an unnecessary concave portion appears as shown by the pulse on the left side of FIG. There is a problem that VCTL becomes extremely inaccurate.

[0011] The filter capacitor C shown in FIG.
With u, Cv, and Cw, it is impossible to suppress the noise fluctuation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device for a brushless motor which can perform high-precision control at a low cost while suppressing noise fluctuation.

[0013]

According to a first aspect of the present invention, there is provided a brushless motor control device comprising: a stator having an m-phase driving coil energized in a reciprocating manner in positive and negative directions; Element, n position detectors for obtaining an m-phase output signal corresponding to the rotation of the rotor, and a drive circuit for controlling the energization of the drive coil based on each output signal of the n position detectors Wherein the n position detectors are connected via a bias resistor between a power supply voltage and a ground voltage, and an input terminal of the position detector and a power supply voltage side. One end is connected to the bias resistor, and the other end is connected to the ground voltage, and a noise reducing capacitor is provided.

According to another aspect of the present invention, there is provided a control device for a brushless motor connected to an output terminal of at least one of the n position detectors. And a converter for generating a pulse signal.

According to the control device for a brushless motor of the present invention having such a configuration, even if noise or extraneous noise due to, for example, switching of the energization of the drive coil rides on the power line of the position detector, the input of the position detector can be reduced. One end is connected between the terminal and the bias resistor on the power supply voltage side, and a capacitor for noise reduction is provided, the other end of which is connected to the ground voltage.
Noise fluctuation is suppressed. At this time, since the noise reduction capacitor is connected in series with the bias resistor, the capacitor discharges quickly, and thus the capacitor that suppresses noise fluctuation can be a small-capacity capacitor.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram illustrating a main part of a control device of a brushless motor according to an embodiment of the present invention. The control device of the brushless motor of this embodiment
4 and 5 is different from the prior art shown in FIGS. 4 and 5 in that the input terminals of the Hall elements Hu, Hv, Hw as position detectors connected in parallel between the bias resistors r1 and r2 and the power supply voltage side of the Vcc power supply voltage side. One point is connected to the bias resistor r1, and the other end is provided with a noise reducing capacitor C connected to the ground voltage.

As described above, since the control circuit of the brushless motor of this embodiment is configured, the Hall elements Hu,
For example, drive coils Lu and L are connected to power supply lines of Hv and Hw.
Even if noise due to the switching of the currents v and Lw or external noise is present, noise fluctuation is suppressed by the accumulated charge effect of the noise reduction capacitor C. Therefore, in the case where the control of the subsequent stage is performed based on the outputs of the Hall elements Hu, Hv, and Hw, the control of the subsequent stage can be performed with high accuracy, and the output of the Hall element Hu can be controlled. , It is possible to obtain a high-precision FG signal.

In this embodiment, as described above, since the noise reducing capacitor C is connected in series with the bias resistor r1 on the Vcc power supply voltage side, the discharging by the capacitor C is fast. Can be a so-called chip capacitor having a small capacity (1 μF or less in the present embodiment), and cost reduction can be achieved.

FIG. 2 is a circuit diagram showing a main part of a control device of a brushless motor according to another embodiment of the present invention.
This shows an embodiment in the case where the Hall elements Hu, Hv, Hw are connected in series.

That is, in this embodiment, the Hall elements Hu, Hv, Hw are connected in series, and the noise reducing capacitor C is similar to the above embodiment in that the other end is connected to the ground voltage. However, one end is connected between the power supply voltage side input terminal of the Hall element Hu and the bias resistor r1 on the Vcc power supply voltage side.

It is needless to say that the same effect as in the above embodiment can be obtained even with this configuration.

In each of the embodiments shown in FIGS. 1 and 2, the comparator P for forming the FG signal is replaced by the Hall element Hu.
Is connected to the output terminal of the Hall element H.
Even if it is connected to v or the output terminal of the Hall element Hw, it is possible to obtain the same high-precision FG signal as when it is connected to the output terminal of the Hall element Hu.

FIG. 3 is a circuit diagram showing a main part of a control device for a brushless motor according to still another embodiment of the present invention, which is a modification of the embodiment shown in FIG.

That is, in the embodiment shown in FIG. 3A, the output terminal of the hall element Hv at the middle stage in the figure among the hall elements Hu, Hv, Hw connected in series is connected to the comparison terminal for forming the FG signal. The device P is connected, and the noise reducing capacitor C is the same as the above-described embodiments in that the other end is connected to the ground voltage. It is connected between the power supply voltage side input terminal of the element Hv.

Therefore, when an FG signal is obtained based on the output of the Hall element Hv, a high-precision FG signal can be obtained as in the previous embodiments, but the Hall elements Hu, Hv, In the case where the control at the subsequent stage is performed based on the output of Hw, the above-described noise is added to the output of the Hall element Hu (no noise is added to the output of the Hall elements Hv and Hw). The accuracy of the control at the subsequent stage is somewhat reduced as compared with

In the embodiment shown in FIG. 3B, the output terminal of the lower one of the Hall elements Hu, Hv, Hw connected in series is connected to the output terminal of the comparison element for forming the FG signal. The device P is connected, and the noise reducing capacitor C is the same as the above embodiments in that the other end is connected to the ground voltage. It is connected between the power supply voltage side input terminal of the element Hw.

Therefore, when an FG signal is obtained based on the output of the Hall element Hw, a high-precision FG signal can be obtained as in the previous embodiments, but the Hall elements Hu, Hv, In the case where the control at the subsequent stage is performed based on the output of Hw, since the above-described noise is added to the outputs of the Hall elements Hu and Hv (no noise is added to the output of the Hall element Hw), FIG. As compared with the embodiment shown in FIG. 1, the accuracy of the control at the subsequent stage is slightly reduced.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say, for example, in the above-described embodiment, an application to a configuration in which an FG signal is obtained from a Hall element output for one phase is described. Similarly, the present invention can be applied to a configuration in which an FG signal is obtained.

The apparatus of the present invention is disclosed in, for example,
As in the brushless motor position detecting device described in Japanese Patent Application Publication No. 11782, the position detecting magnetic pole is magnetized at a position shifted by about 30 electrical degrees from the magnetic center of the magnetic pole Z, and this magnetic field is applied to the same Hall element as described above. Hu, Hv, H
w, and can be similarly applied to the case where a PG signal (position detection signal) is obtained by a predetermined circuit that processes the outputs of these Hall elements Hu, Hv, Hw. And a highly accurate PG signal can be obtained.

Further, it goes without saying that the device of the present invention can be applied to brushless motors other than three-phase.

[0031]

As described above, the control device of the brushless motor according to the present invention is capable of controlling the input of the position detector even if the power supply line of the position detector receives, for example, noise due to switching of the drive coil or external noise. One end is connected between the terminal and the bias resistor on the power supply voltage side, and a noise reducing capacitor is provided, the other end of which is connected to the ground voltage. Since the capacitor for noise reduction is connected in series with the bias resistor as described above, the discharge by the capacitor is accelerated, and the capacitor is configured to be a small-capacity capacitor.
High-precision control can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a main part of a control device of a brushless motor according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a main part of a control device of a brushless motor according to another embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating a main part of a control device of a brushless motor according to still another embodiment of the present invention.

FIG. 4 is an exploded perspective view illustrating a schematic configuration of a brushless motor.

FIG. 5 is a configuration diagram showing a drive circuit section of a brushless motor employing a hard switching energization method.

6A and 6B are waveform diagrams showing FG signals, wherein FIG. 6A is a waveform diagram not affected by noise, and FIG. 6B is a waveform diagram affected by noise.

[Explanation of symbols]

 Reference Signs List 1 Drive circuit C Noise reducing capacitor Hu, Hv, Hw Position detector Lu, Lv, Lw Drive coil P converter r1 Bias resistance on power supply voltage side r2 Bias resistance on ground voltage side Vcc Power supply voltage X Stator Y Rotor Z magnetic pole

Claims (2)

[Claims] 1. A stator having an m-phase drive coil reciprocally energized in positive and negative directions, a rotor having magnetic poles, and n number of position detectors for obtaining m-phase output signals corresponding to the rotation of the rotor. A brushless motor control device comprising: a motor; and a drive circuit that controls energization of the drive coil based on each output signal of the n position detectors. Between the input terminal of the position detector and the bias resistor on the power supply voltage side, and the other end is connected to the ground voltage. A brushless motor control device comprising a capacitor for use in a motor. 2. The brushless motor according to claim 1, further comprising a converter connected to an output terminal of at least one of the n position detectors to form a pulse signal. Control device.