JPH09163786A - Motor control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the components of a motor from being damaged by correctly recognizing the state of the motor by forcibly functioning burn up prevention means by discriminant signals from the number of revolutions discriminant means. SOLUTION: A burn up prevention circuit detects the loss of magnetic pole switching in a detection signal of rotation position detecting means during rotation control, and performs feeding with an intermittent current having a constant duty ratio to phase coils L1 and L2 thereby preventing the burning up of coil L1 and L2. The number of revolutions discriminant means 26 detects the number of revolutions of a rotor based on the magnetic pole switching of detecting signals from the rotation position detecting means, and judges that the number of revolutions dropped below a specified value lower than the number of revolutions during ordinary rotating state. And by this discriminant signal of this number of revolutions discriminant means 26, the burn up prevention means is forcibly functioned. By doing this, rotating state of a rotor can be correctly recognized even in a vibrating state, and the rotation control can be performed without giving damages to the portions of the motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for controlling a motor, and more particularly to a control circuit for a fan motor used for cooling the inside of a copying machine or the like.

[0002]

2. Description of the Related Art In OA equipment such as copying machines, a cooling fan motor is installed in order to prevent damage to the equipment due to overheating due to the extremely high temperature inside the equipment. This kind of fan motor is equipped with various functions to prevent damage to the fan motor, reduce power consumption, and prolong the life of the fan motor. There is a control function to prevent the physical damage.

For example, FIG. 5 shows a conventional fan motor control circuit having this function. That is, two-phase drive coils L1, L wound around the stator core of the fan motor
2 is a motor drive I as one of the drive control means
It is connected to the output terminals 5 and 10 of the CDIC and the other end is the power supply voltage V
It is connected to cc through a backflow prevention diode D1. Further, in the motor driving ICDIC, a hall element HE for detecting the switching of the magnetic poles of the permanent magnet rotor as a rotational position detecting means to detect the rotational position of the rotor is connected to the hall element input terminals 1 and 2. The output currents to the driving coils L1 and L2 are switched according to the detection signal.

In the motor driving ICDIC, a capacitor C is connected to a capacitor input terminal 3 as shown in FIG. 7, a charging circuit 30 for charging the capacitor C, and a terminal voltage of the capacitor C having a preset upper limit. Discharge circuit 31 for discharging the capacitor C1 when the threshold value is reached
And a transistor Tr connected between these two circuits
And has a constant output current to the coils L1 and L2.
The intermittent current of the tee ratio is used to operate as a burnout prevention means for preventing burnout of the coil.

The operation of this ICDIC will be described with reference to the waveform chart of FIG. A square wave signal corresponding to the switching of the magnetic pole based on the detection signal from the Hall element HE is input to the base of the transistor Tr. For example, when a high signal is input, the transistor Tr is turned on, and the capacitor C turns the transistor Tr on. Be discharged through. When the low signal is input, the transistor Tr is turned off and the capacitor C1 is charged by the charging circuit 30. This charge and discharge is
As described above, since the switching is performed based on the detection signal from the Hall element HE, in the rotating state, the magnetic poles of the permanent magnet rotor are frequently switched, and at the same time, the transistor Tr is also turned on / off and charging / discharging is frequently switched. As a result, the terminal voltage of the capacitor C becomes low level (period A in FIG. 6).

However, if the rotation is blocked and the locked state is caused for some reason, the switching of the magnetic poles of the permanent magnet rotor cannot be detected. At this time, the transistor Tr
Turns off, the capacitor C continues to be charged, and the terminal voltage of the capacitor C rises (period B in FIG. 6). When the terminal voltage of the capacitor C reaches the preset upper limit threshold value, this is detected by the charging circuit 30 and the like, and the charging operation by the charging circuit 30 is stopped. At the same time, the discharging circuit 31 is activated and the capacitor C Is started (period C in FIG. 6). After that, when the terminal voltage of the capacitor is discharged to a preset lower limit threshold value, this is detected by the discharge circuit 31, etc., and the discharge operation by the discharge circuit 31 is stopped, and at the same time, the charge circuit 30 is activated and charged again. The action is taken. As described above, the charging / discharging control means for controlling the charging and discharging is provided in each of the charging circuit 30 and the discharging circuit 31. Then, as long as the locked state continues, the operation of discharging the capacitor to the lower threshold value and charging to the upper threshold value is repeated. At this time, the output current to the coil is energized only when the capacitor is charged, that is, only during the period B, and the output current to the coil is intermittently supplied in the locked state.
As a result, overheating is prevented. In this way, the drive ICDIC and the coil are prevented from being burnt in the locked state, and thermal deformation of the housing and the impeller is prevented (protection function). When the lock state is avoided, the rotation state is automatically restored.

[0007]

In the above motor drive circuit, since the Hall element HE does not detect the switching of the magnetic poles in the locked state where the rotor is completely stopped, the protective function as described above is used. It is possible to prevent the circuit from being damaged due to the operation of the coil and the current continuously flowing through the coil. However, even if the rotor is locked, if the restraining force that prevents its rotation is weak, the rotor will not be in a completely locked state and the boundary of the magnetic poles of the permanent magnet rotor will face the hall element HE. In this case, the permanent magnet rotor may be in a so-called vibration state in which the permanent magnet rotor repeatedly moves in the forward and reverse directions. In this case, the permanent magnet rotor does not rotate, but the Hall element HE repeatedly detects switching of the magnetic poles, so the motor drive ICDIC to which the detection signal from the Hall element HE is input is recognized as being in a rotating state, The current continues to be supplied as in the period A of FIG. However, since the motor is not rotating, the electric energy of the current supplied to the coil is not consumed as the rotational energy and becomes thermal energy, and the temperature of the coil continues to rise. As a result, burnout of the drive ICDIC and coil,
In addition, thermal deformation of the housing, impeller, etc. may occur, making it impossible to control the motor.

The present invention has been made in view of the above problems, and an object of the present invention is to correctly recognize the state of the motor regardless of the rotating state and damage the components of the motor. (EN) Provided is a motor control circuit capable of controlling rotation without giving a voltage.

[0009]

In order to solve the above-mentioned problems, the motor control circuit of the present invention detects a rotational position of the rotor by detecting switching of magnetic poles in a permanent magnet rotor of the motor. Drive control means for switching the current supplied to each phase coil of the motor according to the switching of the magnetic pole to the detection signal of the rotational position detection means during rotation control, and the magnetic pole for the detection signal of the rotational position detection means during rotation control. Of the magnetic pole of the detection signal from the rotational position detecting means, which detects that the switching current has disappeared and uses the current supplied to each phase coil as an intermittent current with a constant duty ratio to prevent the coil from burning. A rotational speed determination unit that detects the rotational speed of the rotor based on the switching and determines that the rotational speed has dropped to a specified value lower than the rotational speed in the normal rotational state, The discrimination signal of the rotational speed determining means comprising a feature that it has to forcibly function 該焼 loss prevention means.

The burnout prevention means includes a capacitor,
A charging circuit for charging the capacitor, a discharging circuit for discharging the charged capacitor, a transistor for charging / discharging the capacitor based on switching of magnetic poles of a detection signal from the rotational position detecting means, and a capacitor for the capacitor. Charging / discharging control means for activating the discharge circuit when the terminal voltage reaches the upper threshold value and operating the charging circuit when the terminal voltage of the capacitor reaches the lower threshold value, The drive control means is configured to supply a current to each phase coil until the terminal voltage of the capacitor reaches the upper threshold value, and the determination signal of the rotation speed determination means is generated by the transistor. You may make it function so that charging / discharging of this capacitor may be suppressed.

Further, the rotational speed discriminating means generates a square wave signal as a triangular wave signal based on the switching of the magnetic poles of the detection signal from the rotational position detecting means, and a peak value of the triangular wave signal. It comprises a peak hold circuit for holding and a comparison circuit for comparing the peak value of the triangular wave signal with a preset reference value to determine the level of the peak value, and the output signal of the comparison circuit serves as the determination signal. You may do it.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a motor control circuit according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a fan motor control circuit used for cooling the inside of a copying machine or the like. In addition, in the embodiment, the same or corresponding portions as those in the related art are designated by the same reference numerals.

FIG. 1 shows a drive circuit of a two-phase brushless DC motor as a fan motor, which is for driving a motor through a resistor R1 and a backflow prevention diode D1 to a positive power supply terminal tv which supplies a DC voltage Vcc as an operating voltage. Coils L1, L2
One end of each is connected, and the other end is for motor drive I
It is connected to the output terminals 5 and 10 of the CDIC. The permanent magnet rotor of the motor is rotated by passing a current through the coils L1 and L2 for excitation.

The driving ICDIC is provided with Hall element input terminals 1 and 2 and is connected with a Hall element HE for detecting the switching of the magnetic pole of a permanent magnet at the rotational position of the rotor. The current flowing through the coils L1 and L2 is controlled according to this detection signal. The power supply input terminal 14 of the driving ICDIC is connected to the positive power supply terminal tv via the resistor R2.

Diodes D2 and D3 are connected to the other ends of the coils L1 and L2, respectively.
2, D3 are connected to the Zener diode ZD, and the Zener diode ZD is connected to the base of the transistor Tr1. The collector side of the transistor Tr1 is connected to the connection point N between the resistor R6 and the capacitor C1 which are connected in series, and one end of the resistor R6 is connected to the positive power supply terminal tv and the capacitor C1.
Is grounded. The triangular wave generating circuit 22 is configured by these, and the induction current of the coil generated when the coils L1 and L2 are alternately turned on and off is converted into a square wave signal by the Zener diode ZD, and the transistor Tr1 is switched by the square wave signal. , The capacitor C1 is charged and discharged as the transistor Tr1 is turned on and off.
A triangular wave signal is generated at the connection point N between R6 and the capacitor C1.

This triangular wave signal is supplied to the peak hold circuit 2
3 is input. The peak hold circuit 23 comprises a comparator CO1, a diode D4 and a capacitor C2, and holds and outputs the peak value of the triangular wave signal. Further, the peak value of the triangular wave signal is input to the smoothing circuit 24 including the resistor R7 and the capacitor C3, smoothed, and then input to the comparison circuit 25 of the next stage. In the comparison circuit 25, the smoothed signal from the smoothing circuit 24 and the voltage obtained by dividing the DC voltage Vcc by the resistors R8 and R9, that is, the reference voltage Vref are compared.
CO2, a high level signal is output when the smoothed signal from the smoothing circuit 24 is higher than the reference voltage Vref,
If it is low, a low level signal is output. Switching between the high and low level signals is performed by outputting a low level signal when the rotation speed of the rotor is high and a high level signal when the rotation speed is low. The output terminal of the comparator CO2 is connected to the capacitor input terminal 3 of the motor driving ICDIC. Therefore, the triangular wave generation circuit 22, the peak hold circuit 23, the smoothing circuit 24, and the comparison circuit 25 form a rotation speed determination circuit 26 that determines the rotation speed.

The operation of the above motor drive circuit will be described. When the power is turned on, an initial current flows through the coils L1 and L2, and when the permanent magnet rotor rotates, the Hall element HE outputs a detection signal according to the magnetic pole of this rotor, and the magnetic pole is cut in the drive ICDIC according to this signal. Replacement is detected. Then, according to the switching of the magnetic poles, the coil L
The transistor (not shown) connected to 1 and L2 is alternately turned on and off to alternately excite the drive coils L1 and L2, thereby continuously rotating the rotor.

When rotating the rotor, the coils L1 and L2
Diodes D1 and D2 are connected to prevent short circuit. The back electromotive force of each of the coils L1 and L2 is sent to the triangular wave generating circuit 22 and converted into a triangular wave signal, and the peak value of the triangular wave signal is held by the peak hold circuit 23 and smoothed by the smoothing circuit 24. This peak value is compared with the reference voltage Vref in the comparison circuit 25, and the signal output according to this magnitude is input to the input terminal 3 of the driving ICDIC.
Is input to When the triangular wave satisfies the normal rotation speed, the peak value falls within the reference level k as shown in FIG. At this time, the output signal from the output point Q of the comparison circuit 25 (hereinafter referred to as the determination signal) is a low signal.
However, when the number of rotations decreases, switching of the magnetic pole of the rotor with respect to the Hall element HE becomes slower, so that the waveform level of the triangular wave signal becomes large and the discrimination signal becomes a high signal as shown in FIG. 3B. In this way, the determination signal changes depending on the rotation speed, and it is possible to determine that the rotation speed has dropped below a specified value lower than the rotation speed in the normal rotation state.

On the other hand, the driving ICDIC has a charging circuit 30 and a discharging circuit 31, as shown in FIG. 2, and the collector of a transistor Tr is connected to a connection point R between them. Further, the output signal from the rotational speed discrimination circuit 26 is input to the input terminal 3 of the ICDIC. Transistor T
A signal based on the detection signal of the Hall element HE is input to the base of r. A capacitor C is connected to the input terminal 3.

Next, the circuit operation in the normal rotation state, the lock state and the vibration state will be described with reference to FIGS. 2 and 4. In FIG. 2, in the normal rotation state, a square wave signal corresponding to the switching of the magnetic pole is input to the base of the transistor Tr as in the conventional case, and the charging / discharging of the capacitor C is repeated by turning on / off the transistor Tr.
Since the magnetic poles of the permanent magnet rotor are frequently switched, the terminal voltage of the capacitor C becomes low level (period A in FIG. 4).

In the locked state, the switching of the magnetic pole is not detected, the transistor Tr is turned off, and the capacitor C is charged by the charging circuit 30. On the other hand, since the rotor is not rotating, a high signal is output as a discrimination signal from the rotation number discriminating circuit 26, which also contributes to the charging of the capacitor C and forcibly causes the terminal voltage to reach the upper threshold value. Act on. Therefore, since the capacitor C is charged from both sides, the terminal voltage of the capacitor C rapidly rises and is charged to the upper limit threshold value as in the period D of the waveform diagram of FIG. After that, when the upper limit threshold value is reached, the discharge circuit 31 operates and discharges to the lower limit threshold value. At the time of this discharge, since the high signal is continuously output as the determination signal, it takes more time than the time of charging until the terminal voltage reaches the lower limit threshold value, and the terminal voltage is discharged as in period E of FIG. . While current is passed through the coils L1 and L2 during the charging period D, current is stopped through the coils L1 and L2 during the period E. As a result, the output currents to the coils L1 and L2 are used as an intermittent current with a constant duty ratio to form a burnout prevention means for preventing burnout of the coils. Therefore, current is intermittently supplied to the locked state, and overheating of the circuit and the like is prevented.

In the vibrating state, since the boundary line of the magnetic poles of the permanent magnet rotor moves in the forward and reverse directions with respect to the hall element HE, the Hall element appears to be rotating even though it is not rotating. Although recognized by the detection signal from the HE, the discrimination signal at this time outputs a high signal because the rotor is not rotating. Since the transistor Tr is turned on / off according to the switching of the magnetic poles, it tries to supply the output current to the coils L1 and L2 in a rotating state. However, as the determination signal, a high signal indicating a decrease in the number of revolutions is output, so that the capacitor C is charged to the upper threshold value as in the period D of FIG. That is, the determination signal acts so as to force the terminal voltage of the capacitor to reach the upper limit threshold value. When the upper limit threshold value is reached, the discharge circuit 31 is activated and the lower limit threshold value is discharged. At this time,
Since the output currents to the coils L1 and L2 are stopped, the rotor cannot vibrate and is stopped. When the lower limit threshold is reached, charging is started again, so that the output current to the coils L1 and L2 is started and the rotor also tries to rotate. Further, when the terminal voltage of the capacitor reaches the upper limit threshold value due to the high signal of the determination signal, the output current to the coils L1 and L2 is stopped and the operation of the rotor is stopped in the same manner as described above. In this way, since the output current to the coil is stopped except when the capacitor C is charged as in the locked state,
Even in a vibrating state, the output current to the coil flows intermittently, and the circuit is prevented from overheating.

Even in the state where the motor is abnormally rotated and a load is applied, that is, in the locked state and the oscillated state, the current is intermittently supplied to the drive coils L1 and L2, thereby damaging the circuit or the like. Is prevented.

In the above-described embodiment, the charge / discharge control means is provided in the discharge circuit 31 to operate the discharge circuit 31 when the terminal voltage of the capacitor C reaches the upper limit threshold. The charging circuit 30 is provided with means for operating the charging circuit 30 when the lower limit threshold value is reached.
It may be provided separately from the charging circuit 30.

[0025]

Since the motor control circuit of the present invention has the above-mentioned configuration, it has the following effects. That is,
Since the burnout prevention means is forced to function by the determination signal from the rotation speed determination means, the rotation position detection means can correctly recognize the rotation state of the rotor even if it is in a vibration state. The rotation can be controlled without damaging each part of the motor.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a motor control circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a driving IC according to an embodiment.

FIG. 3 is a waveform diagram showing a triangular wave signal of the motor control circuit according to the embodiment.

FIG. 4 is a waveform diagram showing the relationship between the terminal voltage of the capacitor and the output current to the coil in the motor control circuit according to the embodiment.

FIG. 5 is a circuit diagram showing a motor control circuit according to a conventional technique.

FIG. 6 is a waveform diagram showing a relationship between a terminal voltage of a capacitor and an output current to a coil in a motor control circuit according to a conventional technique.

FIG. 7 is a circuit diagram showing a driving IC according to a conventional technique.

[Explanation of symbols]

 HE Hall element L1, L2 coil DIC drive IC Tr transistor C capacitor 22 triangular wave generation circuit 23 peak hold circuit 25 comparison circuit 26 rotation discrimination circuit 30 charging circuit 31 discharging circuit

Claims (3)

[Claims] 1. A rotation position detecting means for detecting a rotation position of a rotor by detecting a change of a magnetic pole in a permanent magnet rotor of a motor, and a detection signal of the rotation position detecting means during rotation control based on the change of the magnetic pole. Drive control means for switching the output current to each phase coil of the motor and the output signal to each phase coil is detected by detecting that the magnetic pole is no longer switched in the detection signal of the rotation position detection means during rotation control. Burnout prevention means for preventing coil burnout as an intermittent current of the duty ratio of the rotor, and the rotation speed of the rotor is detected based on the switching of the magnetic poles of the detection signal from the rotation position detection means, and the rotation speed is the normal rotation state. And a rotational speed discriminating means for discriminating that the rotational speed discriminating means has discriminated that it has fallen below a prescribed value lower than the rotational speed. Motor control circuit, characterized in that so as to ability. 2. The burnout prevention means includes a capacitor, a charging circuit for charging the capacitor, a discharging circuit for discharging the charged capacitor, and a switching of magnetic poles of a detection signal from the rotational position detecting means. A transistor for charging / discharging a capacitor based on the charging circuit, and a charging circuit for activating the discharging circuit when the terminal voltage of the capacitor reaches an upper threshold value and the charging circuit when the terminal voltage of the capacitor reaches a lower threshold value. Charging / discharging control means for operating the driving control means, and the driving control means is configured to supply a current to each phase coil until the terminal voltage of the capacitor reaches an upper limit threshold value. 2. The motor control circuit according to claim 1, wherein the determination signal of the rotation speed determination means functions to suppress charging and discharging of the capacitor by the transistor. 3. The rotation speed discrimination means generates a square wave signal as a triangle wave signal based on switching of magnetic poles of a detection signal from the rotation position detection means, and a peak value of the triangle wave signal. It comprises a peak hold circuit for holding and a comparison circuit for comparing the peak value held by the peak hold circuit with a preset reference value, and the output signal of the comparison circuit is the discrimination signal. Claim 1 which becomes
Motor control circuit as described.