JP2001218489A - Ac synchronous motor drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC synchronous motor drive circuit which can be constituted at a low cost, with its circuit constitution simple, and besides where the speed control high in stability can be obtained. SOLUTION: An AC synchronous motor drive circuit 50 has a main controller 1 which generates a reference signal corresponding to specified rotational speed, a control means 2 which outputs clock pulses having specified frequency, according to the above reference signal sent from the main controller 1, and a stepping motor driver 3 which outputs a pseudo sine wave current synchronously with the clock pulses, and it drives the above AC synchronous motor 4 by the current outputted by the stepping motor driver 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC synchronous motor driving circuit for driving an AC synchronous motor while controlling its rotation speed.

[0002]

2. Description of the Related Art Conventionally, in various fields, an AC synchronous motor is driven while stabilizing a rotational speed at a predetermined speed.
A C synchronous motor drive circuit is used.

For example, in a copying machine or a laser printer, a laser beam emitted from a light source is turned on / off by a modulation signal at the time of copying or drawing, and the laser beam is rotated by a motor using deflection means. Scanning is performed on the drawing surface to form an image on the drawing surface. Here, if the deflecting means is not always rotating at a predetermined speed,
The drawn content is not drawn at the position where it should be drawn, and high-definition drawing cannot be performed.

Therefore, in the scanning optical apparatus such as the laser printer, an AC synchronous motor drive circuit is used as a drive circuit of a motor for rotating the deflecting means. FIG.
FIG. 1 is a block diagram of a conventional AC synchronous motor drive circuit.

As shown in FIG. 1, a conventional AC synchronous motor drive circuit includes a setting unit such as a personal computer and a controller, and a CP.
U, an inverter circuit, an AC synchronous motor, and an encoder. The setting unit transmits a signal (hereinafter, referred to as a reference signal) corresponding to a predetermined rotation speed of the AC synchronous motor to the CPU. The CPU transmits a predetermined control signal to the inverter circuit based on the reference signal, and the inverter circuit generates an AC current having a frequency corresponding to the received control signal,
Supply to C synchronous motor. The AC synchronous motor is driven by the current supplied from the inverter circuit, and rotates the deflecting means.

[0006] The rotational speed of the AC synchronous motor is detected by an encoder and fed back to the CPU as a detection signal. The CPU changes the frequency of the AC current output from the inverter circuit so that the feedback detection signal has a value corresponding to the predetermined rotation speed, thereby matching the rotation speed of the AC synchronous motor with the predetermined rotation speed. Can be done.

As described above, the conventional motor drive circuit is
In order to fine-tune the frequency of the alternating current supplied to the C synchronous motor, an inverter circuit had to be used. Therefore, in order to finely adjust the speed of the AC synchronous motor, a complicated circuit configuration is required, which leads to an increase in the cost of the apparatus.

[0008]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an AC synchronous motor driving circuit which can be constructed at a low cost without a complicated circuit configuration and can perform precise speed control. The purpose is to do.

[0009]

According to a first aspect of the present invention, there is provided an AC synchronous motor driving circuit comprising: a main controller for generating a reference signal corresponding to a predetermined rotation speed; and the reference signal transmitted from the main controller. Control means for outputting a clock pulse having a predetermined frequency, and a stepping motor driver for outputting a pseudo sine wave current in synchronization with the clock pulse, wherein the pseudo sine wave current output by the stepping motor driver The AC synchronous motor is driven by the control unit.

According to the present invention, a motor drive circuit can be realized at low cost without complicating the circuit configuration. Further, since a stepping motor driver capable of outputting an alternating current having a frequency corresponding to the frequency of the given clock pulse is used, a stable rotation speed can be maintained even in an open loop.

According to the AC synchronous motor drive circuit of the present invention, the rotational speed of the AC synchronous motor is detected,
An encoder for transmitting a detection signal corresponding to a rotation speed to the control unit is further provided. The control unit changes the frequency of a clock pulse output to the stepping motor driver by comparing the reference signal with the detection signal.

According to the second aspect of the present invention, by feeding back the detection signal from the encoder,
With respect to the rotation speed of the AC synchronous motor, control with higher stability can be performed.

According to the AC synchronous motor drive circuit of the third aspect, the stepping motor driver is capable of synchronizing with the clock pulse and having the same frequency and a phase difference of 90 °.
It is desirable to output different types of pseudo sine wave currents.

According to a fourth aspect of the present invention, there is provided a laser beam drawing apparatus, comprising: a deflecting means having a deflecting surface for deflecting an incident laser beam; an AC synchronous motor for rotating the deflecting means; And a control unit for outputting a clock pulse having a predetermined frequency in accordance with the reference signal transmitted from the main controller, and a stepping unit for outputting a pseudo sine wave current in synchronization with the clock pulse. And an AC synchronous motor driving circuit which is configured with a motor driver and drives the AC synchronous motor with a current output by the stepping motor driver.

According to the present laser beam drawing apparatus, since the deflecting means can be always rotated at a predetermined speed, high-definition drawing can be performed on the drawing surface.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a drawing process of a laser beam drawing apparatus to which the present invention is applied will be described. FIG.
FIG. 1 is a diagram illustrating a schematic configuration of a laser beam writing apparatus 100.

The laser beam writing apparatus 100 includes a hologram disk 5, a control unit 9, a piezo driver 10,
AOM driver 11, laser driver 12, light source 13,
Mirrors 14, 15, 16, 18, 19, 22, AOM1
7, a correction optical system 20, collimating lenses 21, 23, aspherical mirrors 24, 25, 26, and a motor drive circuit 50. The control unit 9 has a main controller 1, a CPU 2, a piezo / AOM controller 7, and a laser controller 8. The correction optical system 20 includes a substrate 20
The substrate 20a has a mirror 20b on one surface and a piezo element (not shown) on the surface opposite to the mirror 20b. The surface of the piezo element facing the joint surface with the substrate 20a is fixed by a fixing member such as a frame. The motor drive circuit 50 includes a main controller 1, a CPU 2, a stepping motor driver 3, an AC synchronous motor 4, and an encoder 6.

When the user inputs desired drawing information to the main controller 1, the main controller 1 sends the processing to the CPU 2 and each controller (piezo / AOM controller 7, laser controller 8) provided in the control unit 9. Send the signals needed to do so. That is, the CPU 2, the piezo / AOM controller 7, and the laser controller 8 are controlled by the main controller 1.

The piezo / AOM controller 7 controls an acousto-optic device (AOM) 17 and a correction optical system 20. An acousto-optic element (AOM) 17 is provided on the optical path of the laser beam, and controls on / off of the laser beam.
The correction optical system 20 is provided on the optical path of the laser beam, and corrects a scanning position on the drawing surface 27.

Upon receiving a signal from the main controller 1, the piezo / AOM controller 7 always sends a correction signal to the piezo driver 10 and a modulation signal to the AOM driver 11 according to the drawing state. The piezo driver 10 applies a voltage corresponding to the correction signal to distort the piezo element of the correction optical system 20 by a predetermined amount.
The AOM driver 11 drives the AOM 17 by applying a modulation signal.

When the laser controller 8 receives a signal from the main controller 1, the laser controller 8 transmits a signal for instructing a laser beam output or the like to the laser driver 12, thereby controlling the light source 13 for emitting a laser beam.

The laser beam emitted from the light source 13 is
The light enters the AOM 17 via the mirrors 14, 15 and 16. The AOM 17 modulates the laser beam according to the applied modulation signal. The laser beam modulated by the AOM 17 enters the correction optical system 20 via mirrors 18 and 19. When the voltage is applied to the correction optical system 20, the piezo element is distorted, and the position at which the laser beam reflected by the mirror 19 is incident on the mirror 20b is shifted. As a result, the optical path of the laser beam moves in the direction corresponding to the sub-scanning direction on the drawing surface, and the scanning position on the drawing surface 27 is corrected in the sub-scanning direction.

The laser beam whose optical path has been corrected by the correction optical system 20 enters the hologram disk 5 via a collimator lens 21, a mirror 22, and a collimator lens 23. The collimating lenses 21 and 23 are provided to convert the laser beam into a parallel light beam.

The hologram disk 5 is composed of a plurality of facets sectioned at predetermined angles, and is rotated at a constant speed by an AC synchronous motor 4 controlled by a motor drive circuit 50 described later. Each facet is a diffraction grating that deflects the transmitted laser beam. The laser beam deflected by each facet scans on the drawing surface 27 via the aspheric lenses 24, 25, and 26. In FIG. 2, a straight line L indicates a scanning locus on the drawing surface 27. Note that the laser beam writing apparatus 100
Can perform one scan (main scan) with one facet, and copy or obtain a desired image by moving the drawing surface 27 scanned by the laser beam in a direction (sub-scan direction) orthogonal to the scan direction. Is drawn. The above is the description of the drawing processing using the laser beam drawing apparatus 100.

Next, the motor drive circuit 50 for constantly rotating the hologram disk 5 at a stable and constant speed will be described in detail. FIG. 3 is a block diagram showing the motor drive circuit 50. The motor drive circuit 50 includes a main controller 1, a CPU 2, a stepping motor driver 3,
It includes an AC synchronous motor 4 and an encoder 6 provided in the AC synchronous motor 4.

The stepping motor driver 3 according to the present embodiment, when continuously giving clock pulses having a predetermined frequency, has the same frequency and a 90 ° phase difference.
A type of pseudo-sine wave alternating current is generated. For example, the above output can be obtained by driving the Toshiba TA8435H in the 2W1-2-phase excitation mode. That is, as shown in FIG. 4, when a clock pulse having a predetermined frequency is given, two kinds of pseudo sinusoidal currents (1) and (2) having the same frequency and different phases by approximately 90 ° are generated. Is done.

The main controller 1 includes an AC synchronous motor 4 necessary for rotating the hologram disk 5.
Is input. At the time of drawing, the main controller 1 sends the reference signal to the CPU 2 as shown in FIG. Upon receiving the reference signal, the CPU 2 outputs a clock pulse of a predetermined frequency such that an AC current of a frequency necessary for rotating the AC synchronous motor 4 at a predetermined rotation speed is output from the stepping motor driver 3. To enter.

As shown in FIG. 4, the stepping motor driver 3 responds to a clock pulse from the CPU 2 to
The types of alternating currents (1) and (2) are generated. The AC synchronous motor 4 generates two types of alternating currents (1) and (2).
And the hologram disk 5 is rotated.

The rotational speed of the AC synchronous motor 4 is always detected by an encoder 6 incorporated in the AC synchronous motor 4. The encoder 6 transmits a signal (hereinafter, referred to as a detection signal) corresponding to the detected rotation speed to the CPU 2.

The CPU 2 determines whether the AC represented by the received detection signal
The frequency of the clock pulse output to the stepping motor driver 3 is changed so that the current rotation speed of the synchronous motor 4 matches the predetermined rotation speed.

In the stepping motor driver 3, since the frequency of the applied clock pulse changes, the frequencies of the alternating currents (1) and (2) supplied to the AC synchronous motor 4 also change correspondingly. Thereby, the rotation speed of the AC synchronous motor 4 can be changed.

As shown in FIG. 3, since the motor drive circuit 50 forms a closed loop, the above feedback processing is repeated so that the current rotational speed of the AC synchronous motor 4 becomes a predetermined rotational speed, and the CPU 2 Changes the frequency of the clock pulse. That is, since the AC synchronous motor 4 can be controlled to be stably driven at a predetermined rotation speed, the hologram disk 5 can be rotated at a predetermined speed as a result.

The above is the embodiment of the present invention. The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist. Hereinafter, some modified examples will be described.

In the above embodiment, the AC synchronous motor drive circuit according to the present invention is described as being incorporated in a scanning optical device called a laser drawing device. However, the AC synchronous motor driving circuit according to the present invention can be incorporated in various devices and systems other than the scanning optical device.

As described above, in the present embodiment, the AC synchronous motor 4 is stably driven at a predetermined rotational speed by setting the motor drive circuit 50 in a closed loop state using the stepping motor driver 3 and the encoder 6. Can be. However, the frequency of the alternating current output from the stepping motor driver 3 is uniquely determined from the frequency of the applied clock pulse, and the AC synchronous motor 4 rotates at a synchronous speed determined by the frequency of the supplied alternating current.
Therefore, if the frequency of the clock pulse to be applied to the stepping motor driver 3 is known in advance, the AC synchronous motor 4 can be maintained at a stable speed even when the motor drive circuit 50 is set to an open loop that does not use the encoder 6. And the circuit configuration can be further simplified.

As shown in FIG. 2, the encoder 6 of this embodiment is in a state of being incorporated inside the AC synchronous motor 4. However, it is not always necessary to use the encoder 6 integrated with the AC synchronous motor 4. Also, the encoder 6 may detect the rotation of the hologram disk 5 rotated by the AC synchronous motor 4 instead of detecting the rotation of the AC synchronous motor 4 itself.

Further, in the laser beam writing apparatus 100 of the above embodiment, the hologram disk 5 is rotated by the AC synchronous motor 4 for scanning the laser beam.
The AC synchronous motor drive circuit of the present invention can be applied to a laser beam drawing apparatus that scans a laser beam using a polygon mirror.

[0038]

As described above, the AC synchronous motor driving circuit according to the present invention controls the rotational speed of the AC synchronous motor using an inverter circuit, whereas the AC synchronous motor driving circuit uses a predetermined stepping motor driver. By controlling the rotation speed of the motor, it is possible to reduce the cost without complicating the circuit configuration, and it is possible to precisely control the speed of the AC synchronous motor.

Further, the AC synchronous motor drive circuit of the present invention can be made simpler in circuit configuration by performing so-called open loop control without using an encoder.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a conventional motor drive circuit.

FIG. 2 is a diagram schematically illustrating a configuration of a laser beam drawing apparatus.

FIG. 3 is a block diagram illustrating an AC synchronous motor drive circuit according to the present invention.

FIG. 4 is a diagram illustrating a relationship between a clock pulse and a generated current of a stepping motor driver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main controller 2 CPU 3 Stepping motor driver 4 AC synchronous motor 5 Hologram disk 6 Encoder 13 Light source 17 AOM 20 Correction optical system 27 Drawing surface 50 Motor drive circuit 100 Laser beam drawing device

Continued on the front page F term (reference) 2H045 AA53 AD12 5H575 AA20 BB10 DD06 GG02 GG06 JJ03 JJ13 KK08 LL07 5H576 AA18 BB10 DD01 DD05 DD10 GG02 JJ03 KK06 LL07 5H580 AA10 BB09 BB10 CA10 CA14 FA02 CB03 FA03

Claims (5)

[Claims] 1. An AC synchronous motor driving circuit for driving an AC synchronous motor, comprising: a main controller for generating a reference signal corresponding to a predetermined rotation speed of the AC synchronous motor; and the reference transmitted from the main controller. Control means for outputting a clock pulse having a predetermined frequency in accordance with a signal; and a stepping motor driver for outputting a pseudo sine wave current in synchronization with the clock pulse, wherein the pseudo step output by the stepping motor driver is provided. An AC synchronous motor driving circuit, wherein the AC synchronous motor is driven by a sine wave current. 2. An encoder for detecting a rotation speed of the AC synchronous motor and transmitting a detection signal corresponding to the rotation speed to the control unit, wherein the control unit is configured to control the reference signal, the detection signal, 2. The frequency of the clock pulse output to the stepping motor driver is changed by comparing
2. The AC synchronous motor drive circuit according to 1. 3. The stepping motor driver outputs two kinds of pseudo sinusoidal currents having the same frequency and different phases by 90 ° in synchronization with the clock pulse. 2. The AC synchronous motor drive circuit according to 1. 4. A laser beam drawing apparatus for performing drawing by scanning a laser beam modulated according to drawing data on a drawing surface in a predetermined direction, comprising: a deflecting surface for deflecting an incident laser beam. Deflecting means provided with: an AC synchronous motor for rotating the deflecting means;
A main controller that generates a reference signal corresponding to a predetermined rotation speed of the synchronous motor; a control unit that outputs a clock pulse having a predetermined frequency in accordance with the reference signal transmitted from the main controller; A stepping motor driver for outputting a pseudo sine wave current, and an AC synchronous motor driving circuit for driving the AC synchronous motor with the current output by the stepping motor driver. apparatus. 5. The laser beam drawing apparatus according to claim 4, wherein said deflecting means is a hologram disk.