JPS61218386A - Motor controller - Google Patents

Abstract

PURPOSE:To reduce a noise at phase switching time by setting the rising and falling characteristics of a switching signal for switching the phase to a motor coil in response to the rotating speed of a motor to the desired value. CONSTITUTION:Rotor position detection signals from Hall elements P1-P3 are supplied through amplifiers 1-3 to a matrix circuit 4. The circuit 4 outputs a switching signal for switching the phase on the basis of the position detection signal. Diodes D1-D3 respectively generate voltages proportional to the counterelectromotive voltages of motor coils L1-L3. The voltages are altered in response to the rotating speed of the motor, and the amplification factors of the amplifiers 1-3 are controlled by the voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a motor control device that includes a detection element that detects the rotational position of a motor, and an amplifier that amplifies a position detection signal obtained from the detection element.

[Background technology]

Taking the drive of a three-phase DC motor as an example, the rotational position of the rotor is detected by a magneto-electric conversion element (for example, a Hall element), and the motor coil is energized based on the position detection signal.
In other words, there are motor control devices that perform phase switching.It is known among those skilled in the art that noise is generated during the phase switching in this type of motor control device.The above noise is caused by the relative rotation of the motor. Therefore, it becomes large and may resonate with the cabinet of electronic equipment, which is of particular concern in electronic equipment and appliances that are used during the day, such as office automation equipment.

Furthermore, smoothness of rotation may be lost during phase switching. Furthermore, the above-mentioned problems often occur in home appliances such as VTRs, which are frequently switched between standard mode, double-speed mode, etc. layered. As a result, at the time of phase switching, 1! flows through each motor coil! It has become clear that the larger the flow change di/dt, the louder the noise.

As a countermeasure against this, for example, as shown in "Motor Drive Electronics" (February 20, 1981, published by Ohmsha, pp. 41-42), it is possible to reduce the above current value even if a capacitor is used in the drive circuit. I can do it.

However, with this method, it is not possible to make the current value correspond to the rotational speed of the motor, and since a capacitor is used, a large space is required, which is an obstacle to reducing the size and weight of electronic equipment. Shortcomings have become clear, such as the difficulty in implementing semiconductor integrated circuits for control devices.

[Purpose of the invention]

An object of the present invention is to reduce the number of motor control devices that can reduce noise and rotation unevenness during phase switching of motor coils.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the Invention] A brief summary of typical inventions disclosed in this application is as follows.

In other words, focusing on the fact that the motor's back electromotive force is proportional to the motor's rotation speed, by detecting the above-mentioned back electromotive force, the motor's rotation speed is detected, and the gain of the Hall amplifier is inversely proportional to this detected output. By configuring it to [Embodiment] Hereinafter, an embodiment of a motor control device to which the present invention is applied will be described with reference to FIGS. 1 to 3. Incidentally, FIG. 1 shows a circuit diagram of the above-mentioned control device constructed from a semiconductor integrated circuit, and FIG. 2 is a waveform diagram for explaining the circuit operation.

The feature of this embodiment is that the back electromotive force of the motor coil is detected by a resistor Ra, etc., and the detection signal is used to detect a transistor Q.
A is driven to control the gain of the Hall amplifier. That is, the gain is lowered when the back electromotive force is positive (at high speeds), and the gain is increased when the back electromotive force is small (at low speeds), so that the rise and fall of the position detection signal can be controlled.

With this configuration, even if the rotational speed changes, di/dt at the time of phase switching can be kept almost constant, making it possible to reduce the occurrence of noise. This will be explained in detail below.

P, , P, , P are position detection elements that magnetically detect the rotational position of a rotor (not shown) that constitutes a part of the motor. In this embodiment, a so-called Hall element is used. Note that the motor is a direct current direct drive motor, and the motor coils L, , L, , L are fixed to the stator.

], 2. Reference numeral 3 denotes an amplifier according to the present invention, and since each amplifier has the same circuit configuration, amplifier 1 will be described in detail. When the rotor rotates, the Hall elements P1 to P,
Accordingly, the position detection signals u, v, as shown in Fig. 2 are obtained.
w is obtained and supplied to amplifiers 1-3, respectively. The position detection signal U is transmitted through a differential pair of transistors Q + +
Ql is supplied to each base. Transistors Q,,Qt
performs an amplification operation, but the degree of amplification is controlled by current control by a transistor Qa provided as a control circuit. Note that the resistors R, , R, are load resistances, and the transistor Q8 operates as a foot current circuit. .

□The amplified position detection signal U' is sent to the next stage transistor Q4. QIl, but at this time transistor Q
, , Qs have the same level, the output currents of the transistors Qa and Q7 forming the current mirror circuit will be the same. On the other hand, if the base voltages of transistors Q, , Q, are different, then transistor Q = =
One of the output currents of Qy becomes large and the other becomes small.

The circuit operation as described above is performed for amplifiers 1 to 3, and output signals VI, V! with different phases, respectively. .

(2) is supplied to the matrix circuit 4. The matrix circuit 4 generates switching signals Uv, Vv, Vv, etc. for phase switching as shown in FIG.
This is to obtain Wv. By the way, the position detection signals u and v are shown by the blank line and the imaginary one-dot line.

The switching signal U is shown by a solid line and a virtual dotted line as well as W.
v, vv, and Wv correspond to each other.

As shown in the figure, the voltage levels of the switching signal Uv-Wv are a reference middle level M, a high level H, a low level LKf, a high level H and a low level L (
7) The pressure level is controlled by a control signal Vc, which will be described later, or an output signal Vs of the frequency generator 11, etc., and the rotational speed of the motor is controlled in accordance with the level change.

By the way, the switching signals Uv-Wv are output from the output circuit 6. with the illustrated phase relationship. 7.8, but the above output circuit 6
8 are configured in the form of push-pull amplifiers, and when the switching signals Uv, V, . On the other hand, when the switching signal Uv-Wv is at a low level, the power supply side of the corresponding output circuits 6 to 8 is inactive, and the grounding side is active.

Further, when the switching signal Uv-Wv is at the middle level M, the corresponding output circuits 6 to 8 are inoperative.

Here, regarding the first 60 degrees, as shown in Fig. 2, the switching signal Uv is at the low level, H1vv is at the low level L, and Wv is at the middle level M, so the current I to the motor coils L, ~L, , flows. During the next 60'', the motor coil L,
~L, current I.

flows, and during the next 60° the motor coil L.

A current l flows to ~L. Below, 180°~360°
Until then, currents I4 to I6 flow as shown in FIGS. 1 and 2, and the motor continues to rotate.

While the motor continues to rotate, the voltage appearing from terminal No. 8 to No. 10 also appears at point A via diodes D and D3. Further, this voltage (18) is proportional to the back electromotive force of the motor coils L, -L8. On the other hand, output circuit 6
Since the ground side of .about.8 is grounded via the resistor Ra, the above-mentioned currents 1 and 6 flow through K, so that a voltage 2b corresponding to the amount of current is obtained at one end of the resistor Ra.

As already mentioned, the back electromotive force expressed as voltage ■8 is
Changes in proportion to the motor rotation speed.

Therefore, the voltage level of the detection signal Vo obtained from the comparator A1 is inversely proportional to the voltage ■8. What should be noted here is that
The detection signal Vo is supplied to the base of the transistor Qa via the resistor Rb to control the amplification degree of the amplifier composed of the transistors Q, . . . Qt.

g fTx That is, when the rotational speed of the motor increases and the voltage level of the back electromotive voltage (8) increases, the level of the output signal vo decreases, causing the amplification degree of the amplifier to decrease. As a result, the level change of the output signal U' becomes small,
The level change of the output signal (■) also becomes smaller.

When the rotational speed of the motor decreases, the level of the detection signal vo rises, contrary to the circuit operation described above, and the amplification degree of the amplifier increases. However, 2. The increase in the amplification degree is controlled to a desired amplification degree. be done. As a result, the switching signal Uv
-Wv, the rise and fall characteristics shown by the solid line in FIG. 3 change as shown by the dotted line. In the figure, A shown as a meditative line shows a waveform at low speed, and B shown as a broken line shows a waveform at high speed.

That is, di/dt at the time of phase switching is made small, and the supply and cutoff of currents I, to I6 become smooth. Therefore, during phase switching, noise that tends to occur from the motor is reduced, and rotational unevenness is also reduced. Furthermore, since the positive input of the differential amplifier A is connected to Vb, the following effects can also be obtained. That is, as the load on the motor increases, Vb increases, and as a result, the output Vn of the differential amplifier A becomes large, and the gains of the 7:C rehole amplifiers 1 and 2.3 are controlled to be large. In other words, appropriate feedback is provided even for changes in load.

The frequency generator (hereinafter referred to as FG) 11 controls the rotational speed of the motor, and its structure etc. can be found in [Home Video Technology] (published on July 1, 1980, published by Japan Broadcasting System, Inc.). It is laid out in detail in the board association, p127).

The output signal ■s of the FGII is a frequency signal proportional to the rotational speed of the motor, and this is rectified (by the rectifier 12).
and supplies it to the comparator 13.

On the other hand, the control signal v is sent to the comparator 13 via the comparator 14.
c is supplied, the control circuit 5 is operated by the control signal Vf corresponding to the voltage difference between the two, and the switching signal U
Control the voltage level of v-Wv. Therefore, the motor is controlled at a constant speed and at the same time is controlled to a desired rotational speed by setting the level of the control signal VC. [Effects] (1) The phase to the motor coil is controlled in accordance with the rotational speed of the motor. The rise and fall characteristics of the switching signal that performs switching are set to the desired values, so that the supply and cutoff of current to the motor coil becomes smooth and noise at the time of phase switching can be reduced. can.

Although the invention made by the present inventor has been specifically explained based on examples above, the present invention is not limited to the above-mentioned examples, and it should be noted that various changes can be made without departing from the gist of the invention. Even 1[i.

Output signal V of comparator A. The rotational speed of the motor can be controlled using this.

The motor is not limited to a three-phase motor, and may also be applied to control a multi-phase motor.

[Field of Application] In the above discussion, the invention made by the present inventor was mainly applied to motor control, which is the field of application that formed the background of the invention, but the application is not limited to this, for example, office automation Mation equipment, VTR
, tape recorders, record players, and other electronic devices that use motors.

[Brief explanation of the drawing]

FIG. 1 shows a circuit diagram showing an embodiment of a motor control device to which the present invention is applied, FIG. shows a waveform diagram showing the control of the rising and falling characteristics of the switching signal.P, ~P3...Inside the Hall system, u, v, w...Rotational position detection signal, Uv, V,, Wv...・Switching signal,■
. ...Detection signal, Va...Back electromotive force, L1~Ls・
...Motor coil, A...Comparator, Qa...Transistor, 1-3...Amplifier, 4...Matrix circuit, 5...Control circuit, 6-8...Output circuit.

Claims (1)

[Claims] 1. In a motor control device equipped with a detection element that detects the rotational position of the motor and an amplifier that amplifies the position detection signal obtained from the detection element, the back electromotive force generated from each motor coil when switching the phase of a plurality of motor coils. a control circuit that controls the gain of the amplifier based on the detection signal obtained from the detection circuit and sets rise and fall characteristics of the switching signal that determines the phase switching to a desired value. A motor control device characterized by being provided with.