JP2018139491A - Dc motor driving device and ceiling embedded ventilation device comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which a method of preventing step-out of a DC motor by detecting a voltage applied to the DC motor, a motor current and a revolution speed signal so as to calculate a phase difference and correct a revolution speed needs high-speed and complicated computation and thus requires a microcomputer causing, when incorporated in a driving device, increased cost and size of a control board.SOLUTION: A method comprises monitoring a DC voltage value in a pre-stage generating a three-phase AC voltage for driving a DC motor and, when the DC voltage value is at or below a preset threshold, directly reducing an instructed revolution speed of the DC motor and simultaneously using a brake function to restart in the same state as the power-on state, thereby recovering from the step-out of the DC motor and continuing normal rotation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC motor driving apparatus that drives with a constant motor current so as not to fluctuate greatly, and detects a step-out of the DC motor and returns it to a stable rotation.

  Conventionally, this type of DC motor can be prevented from stepping out by detecting the load voltage or load current of the DC motor, performing a comparison operation, and changing the frequency of the output voltage or output voltage to prevent step-out. It is known (see, for example, Patent Document 1).

  Hereinafter, this type of DC motor driving device described in Patent Document 1 will be described with reference to FIG.

  As shown in FIG. 4, the conventional DC motor driving apparatus converts the AC voltage of the commercial power source into DC by a rectifying diode 101 and a DC smoothing capacitor 102.

  The DC-converted voltage is converted into AC by the inverter 104 driven by the drive circuit 110, and the AC voltage is applied to the armature coils 105, 106, 107 to rotate the motor.

  Further, in order to calculate the difference between the rotational speed command from the inverter 104 and the actual rotational speed of the motor, the DC power voltage detector 103 detects the voltage converted into direct current. Similarly, the current values of the armature coils 105, 106 and 107 are detected by the current detectors 108 and 109. From the detected voltage value, current value, and induced voltage detected from each armature coil, the microcomputer 111 calculates the change rate of the phase difference of the induced voltage.

  Then, the difference between the rotation speed command and the actual rotation speed of the motor is calculated from the change rate of the calculated phase difference, the difference in rotation speed obtained from the final calculation result is corrected, and the actual rotation speed matches the command rotation speed. This prevents the DC motor from stepping out or stabilizes rotation.

Japanese Patent Laid-Open No. 11-55994

  With regard to such conventional DC motor step-out prevention and rotation stabilization methods, it is necessary to collect voltage and current phase differences or DC motor rotation speed as information, and high-speed and complicated calculations are required. Therefore, a microcomputer is essential.

  Therefore, the microcomputer must be incorporated in the drive device, but when the microcomputer is incorporated in the drive device, the size of the control board increases.

  The cost of the drive device becomes high due to the cost of the microcomputer itself and the development cost of software for operating the microcomputer.

  With the demand for product miniaturization and cost reduction, DC motor drive devices incorporated in products are also required to be compact and cost-effective.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide a DC motor drive device that prevents step-out without using a microcomputer and saves space and is inexpensive.

  In order to solve this problem, the present invention provides a three-phase DC motor, drive means for converting a DC voltage into a three-phase AC voltage and applying the same to the DC motor to drive the DC motor, and the DC motor. Rotational speed indicating means for instructing the DC motor driving means with voltage, operating voltage generating means for operating voltage of the DC motor driving means, and changing the DC voltage to the DC motor driving means to output current Constant current output means for maintaining the constant current supply, output voltage detection means for detecting the output voltage of the constant current output means, and a lower limit for generating a reference voltage value for determining a rotational speed abnormality of the DC motor A reference voltage generating means, an output voltage drop diagnosing means for comparing and calculating the output voltage of the constant current output means and the lower limit reference voltage, diagnosing a drop in the output voltage and outputting the output voltage drop state to the outside; First switch means that operates in accordance with the output of the output voltage drop diagnosis means, and the first switch means is inserted between the rotation speed instruction means and the DC motor drive means, and during the rotation of the DC motor When the output voltage drop diagnostic means determines that the output voltage has dropped, the DC motor is restarted by opening the first switch means.

  In such a configuration, the output voltage drop diagnosing means determines that an abnormality in the rotational speed of the DC motor has occurred when the input voltage to the driving means falls below a predetermined lower limit reference voltage value.

  When this rotation speed abnormality is detected, the first switch means opens the rotation speed instruction means, sets the rotation speed command to zero, returns to the same state as when the power is turned on, and restarts.

  Thereby, it can return to a normal state from rotation speed abnormality.

The figure which shows the structure of the drive device of the DC motor of Embodiment 1 of this invention The figure which shows the structure of the drive device of the DC motor of Embodiment 2 of this invention The figure which shows the structure of the drive device of the DC motor of Embodiment 3 of this invention Simplified diagram showing conventional configuration

  The invention according to claim 1 of the present invention includes a three-phase DC motor, drive means for converting a DC voltage into a three-phase AC voltage and applying the same to the DC motor to drive the DC motor, and the rotational speed of the DC motor. Rotation speed indicating means for instructing the driving means with voltage, operating voltage generating means for operating voltage of the driving means, and changing the DC voltage to the DC motor driving means to maintain the output current constant and supply Constant current output means, output voltage detection means for detecting an output voltage of the constant current output means, lower limit reference voltage generation means for generating a reference voltage value for determining a rotational speed abnormality of the DC motor, The output voltage of the constant current output means and the lower limit reference voltage are compared and calculated, the output voltage drop diagnosis means for diagnosing output voltage drop and outputting the output voltage drop state to the outside, and the output of the output voltage drop diagnosis means Action First and second switch means, wherein the first switch means is inserted between the rotation speed indicating means and the drive means, and the second switch means is a brake function terminal of the drive means. Inserted between the operating voltage generating means, and when the output voltage drop diagnostic means determines that the output voltage is reduced during rotation of the DC motor, the first switch means is opened, and the second switch The DC motor is restarted by short-circuiting the means.

  In such a configuration, when the rotational speed of the DC motor driving means is significantly decreased due to some abnormality, the input voltage to the DC motor is significantly decreased. Therefore, it is possible to detect a significant decrease in the rotational speed of the DC motor by providing the output voltage reducing means. When a decrease in the rotational speed is detected, the switch means forcibly sets the rotational speed command to the DC motor to zero, and simultaneously brakes the DC motor to make the rotational speed of the DC motor zero and restart the system. Thus, the DC motor can be returned to normal rotation.

  Further, the rotation speed instruction means may be provided with a time constant circuit for increasing the voltage to be instructed only at the time of activation for a predetermined time, and the voltage of the rotation speed instruction means may be gradually increased simultaneously with energization.

  With this configuration, even a sensorless drive system that does not use a microcomputer can be started from a low rotational speed at the time of startup.

  The third switch means is configured to short-circuit the plus side of the time constant circuit and the zero potential, and the output voltage drop diagnostic means outputs an output voltage. When it is determined that the voltage has dropped, the time constant circuit may be forcibly discharged.

  With this configuration, even in a drive system that does not use a microcomputer, the same operation as when the power is turned on can be performed even when restarting after detecting a decrease in output voltage.

  Further, by incorporating the DC motor driving device of the present invention into a ventilation device, a ventilation device that realizes stable rotation at a low cost and at a low cost can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the DC motor driving device of the first embodiment includes a constant current circuit 1, a motor driver 2, a sensorless DC motor 3, a VSP voltage generation circuit 4, a low voltage generation circuit 5, A voltage detection circuit 6, a reference voltage circuit 7, a comparator 8, two transistors 9, and a transistor 10 are included.

The constant current circuit 1 is a constant current output unit that converts a commercial AC power supply voltage into a DC constant current output. The motor driver 2 is a driving unit that converts the constant current output of the constant current circuit 1 into a three-phase alternating current. The sensorless DC motor 3 is a DC motor that applies the three-phase AC output of the motor driver 2. The VSP voltage generation circuit 4 is a rotation speed instruction means for changing the rotation speed of the sensorless DC motor 3 by arbitrarily applying a voltage from the outside to the motor driver 2 to vary the three-phase AC output generated by the motor driver 2. . The low voltage generation circuit 5 is an operation voltage generation unit that generates an operation voltage of the motor driver 2. The voltage detection circuit 6 detects the output voltage of the constant current circuit 1.
Output voltage detection means. The reference voltage circuit 7 is a lower limit reference voltage generating means for generating a lower limit reference voltage of the output voltage of the constant current circuit 1. The comparator 8 is an output voltage drop diagnosis unit that compares and determines the output of the voltage detection circuit 6 and the output of the reference voltage circuit 7.

  The transistor 9 is a first switch means that is inserted between the motor driver 2 and the VSP voltage generation circuit 4 and interlocks with the output of the comparator 8. The transistor 9 is turned on in a steady state. The transistor 10 is a second switch means that is inserted between the brake function terminal of the motor driver 2 and the low voltage generation circuit 5 and interlocks with the output of the comparator 8.

  The low voltage generation circuit 5 is connected to a brake function terminal built in the motor driver 2 in addition to being connected to the power supply terminal of the motor driver 2. However, a transistor 10 is inserted between the brake function terminal and the low voltage generation circuit 5 and is normally turned off.

  In general, the motor driver 2 incorporates an inverter circuit composed of 2 stages × 3 semiconductor elements, and the inverter circuit converts direct current into three-phase alternating current. A rotating magnetic field is generated by the three-phase alternating current and applied to a sensorless DC motor to rotate the rotor magnet.

  Regarding the generation of the three-phase alternating current, since the sensorless DC motor does not have a magnetic pole sensor that obtains rotor position information, the magnetic pole position is estimated to generate the three-phase alternating current. In this method of estimating the magnetic pole position and rotating the motor, if the load changes suddenly and the motor speed changes abruptly, the estimation of the magnetic pole position may not catch up with the actual rotation. The rotation may be stabilized when the rotation difference from the rotation is greatly deviated and unstable. This is called step-out and is known as a phenomenon unique to sensorless motors.

  Here, the motor control method and power supply circuit characteristics of the present invention will be described. In the present embodiment, the output of the VSP voltage generation circuit 4 and the rotation speed of the motor are fixed, and the motor current is kept constant. In this way, a constant air volume is always output and the torque is not greatly changed.

  The output voltage of the constant current circuit 1 varies depending on the power required by the load. For example, considering the case where the present invention is applied to a ventilation fan, the load is lightest when there is nothing that blocks the opening of the ventilation fan, and the load is heavy when all the openings are blocked. When the load is light, the power required for the sensorless DC motor 3 can be reduced, and the input voltage to the motor driver 2 becomes low. On the other hand, when the load is heavy, the power required for the sensorless DC motor 3 increases, and the input voltage to the motor driver 2 increases.

  Here, when the sensorless DC motor 3 is temporarily in a restrained state due to foreign matter biting into the blades, the rotation speed changes rapidly, so that the estimation of the magnetic pole cannot catch up and step out occurs. When the step-out occurs, the rotation of the motor is significantly reduced and the rotation is irregular, so that the load is very light and the input voltage to the motor driver 2 is greatly reduced. That is, the step-out can be detected by monitoring the input voltage to the motor driver 2.

  After detecting the step-out, it is necessary to return to the normal state. In this embodiment, a restart is applied as a method of returning to the normal state. As a method of restarting, first, the transistor 9 is opened by the output of the comparator 8 when the input voltage to the motor driver 2 becomes lower than the reference voltage. Then, the output of the VSP voltage generation circuit 4 is set to zero, and the rotational speed command to the motor driver 2 is set to zero.

However, the blades continue to rotate due to inertia even when the rotational speed command is zero.
Therefore, the rotation of the blade is forcibly stopped using the brake function of the motor driver 2. That is, by applying a low voltage to the brake terminal of the motor driver 2 by the transistor 10 to enable the brake function of the motor driver 2 to the motor driver 2, the AC output of the motor driver 2 changes to DC and is fixed. The child magnet is attracted to the fixed magnetic field, and the sensorless DC motor 3 appears to be braked.

  By the above operation, when the step-out is detected, the state returns to the same state as when the power is turned on, so that it can be started in the same manner as when the power is turned on.

  As a brake function, there is a method of stopping the rotation of the rotor magnet by a magnetic force by outputting a direct current instead of a three-phase alternating current as an output of the motor driver 2, but any kind of blade function can be stopped. It doesn't matter how.

  Moreover, although the transistor is used this time as the switch means, even if a semiconductor element or a relay is used, there is no difference in the effect.

  By the above method, the sensorless DC motor 3 can be returned from the step-out and stably rotated without using a microcomputer.

(Embodiment 2)
As shown in FIG. 2, the DC motor drive device of the second embodiment is a time constant circuit between the VSP voltage generation circuit 4 and the motor driver 2 with respect to the DC motor drive device of the first embodiment. The resistor 11 and the capacitor 12 are inserted.

  Here, the operation at the time of starting of the sensorless DC motor 3 will be described.

  Although the induced voltage generated by the rotation of the rotor magnet is used for estimation of the magnetic pole position, the induced voltage is zero and the magnetic pole position cannot be estimated because the rotor is not rotating at startup.

  Therefore, in order to start without estimating the magnetic pole position at startup, a process specific to startup is required.

  As a process peculiar to start-up, first, the rotor magnet is brought close to the stator magnet in order to perform the start-up operation smoothly. Accordingly, since the rotor magnetic pole is close when the stator is energized, the stator can easily follow the rotating magnetic field.

  As a method of bringing the rotor magnet closer to the stator magnet, a direct current is passed through the stator winding to attract the rotor magnet to the stator magnet.

  Next, since step-out occurs when it is rotated at a high speed at the time of startup, it is necessary to rotate at a low speed at the time of startup. Therefore, the sensorless DC motor 3 is forcibly rotated by a three-phase AC output of a low rotation command unique to startup provided separately from the output of the VSP voltage generation circuit 4.

  When the induced voltage can be detected by the low rotation command, the magnetic pole can be estimated by the induced voltage, so that the normal rotation operation is switched from the three-phase AC output unique to the start-up to the rotation speed of the output voltage value of the VSP voltage generation circuit 4. Migrate to

  The startup is successful only after this series of operations can be performed normally.

  However, when switching from the three-phase output unique to the startup to the VSP voltage generation circuit 4, if the command rotational speed difference is large, a step-out occurs.

  Therefore, the resistor 11 and the capacitor 12 are given a time constant by the resistor 11 and the capacitor 12 at the start-up, and the output of the VSP voltage generator 4 is gradually increased after energization.

  As a result, the output voltage of the VSP voltage generation circuit 4 can be lowered at the timing of switching from the three-phase output unique to the start-up to the output of the VSP voltage generation circuit 4, so that the rotational speed difference between them can be reduced.

  Even after the rotation command of the sensorless DC motor 3 is switched to the output of the VSP voltage generation circuit 4, the output of the VSP voltage generation circuit 4 rises to a specified value due to charging of the time constant circuit, so that the sensorless DC motor 3 Reach speed.

  By this method, the sensorless DC motor 3 can be stably started without using a microcomputer.

  Note that the operations of the transistors 9 and 10 are the same as those in the first embodiment, and the return method after the step-out is the same.

(Embodiment 3)
As shown in FIG. 3, the DC motor drive device of the third embodiment has both ends of the capacitor 12 of the time constant circuit as shown in FIG. 3 compared to the DC motor drive device of the second embodiment. A transistor 13 as a third switch means for short-circuiting is added.

  As described in the first embodiment, at the time of step-out, the transistor 9 is opened by the output of the comparator 8 when the input voltage to the motor driver 2 falls below the reference voltage.

  Then, the VSP voltage generation circuit 4 and the motor driver 2 are disconnected. However, since the electric charge remains in the capacitor 12 as it is, the VSP voltage input to the motor driver 2 actually hardly decreases.

  Therefore, the transistor 13 short-circuits both ends of the capacitor 12 in conjunction with the output of the comparator 8. In this way, the capacitor 12 is discharged.

  Thereby, at the time of step-out detection, the output voltage of the VSP voltage generation circuit 4 can be made zero at the same time that the VSP voltage generation circuit 4 and the motor driver 2 are disconnected. Therefore, it is possible to start up in the same state as when the power is turned on at the time of restart.

  In this way, in this embodiment, without using a microcomputer, the input voltage to the motor driver is monitored to detect step-out, and at the time of detection, the motor state is restarted with the same state as when the power is turned on. Can be restored to normal rotation from step-out, thus reducing costs and downsizing, and products that require space saving for local installation, for example, ceiling-mounted ventilation fans Can be applied to.

DESCRIPTION OF SYMBOLS 1 Constant current circuit 2 Motor driver 3 Sensorless DC motor 4 VSP voltage generation circuit 5 Low voltage generation circuit 6 Voltage detection circuit 7 Reference voltage circuit 8 Comparator 9 Transistor 10 Transistor 11 Resistance 12 Capacitor 13 Transistor

Claims (4)

A three-phase DC motor;
Drive means for converting a DC voltage into a three-phase AC voltage and applying the DC voltage to the DC motor to drive the DC motor;
A rotation speed instruction means for instructing the DC motor drive means with a voltage to the rotation speed of the DC motor;
An operating voltage generating means to be an operating voltage of the DC motor driving means;
Constant current output means for supplying a constant output current by changing a DC voltage to the DC motor drive means;
Output voltage detection means for detecting the output voltage of the constant current output means;
Lower limit reference voltage generating means for generating a reference voltage value for determining a rotational speed abnormality of the DC motor;
Output voltage drop diagnosis means for comparing and calculating the output voltage of the constant current output means and the lower limit reference voltage, diagnosing a drop in the output voltage, and outputting the output voltage drop state to the outside,
First switch means that operates at the output of the output voltage drop diagnostic means,
The first switch means is inserted between the rotation speed instruction means and the drive means,
DC motor drive characterized by restarting the DC motor by opening the first switch means when the output voltage drop diagnostic means determines that the output voltage is reduced during rotation of the DC motor apparatus. The rotation speed instruction means includes a time constant circuit for increasing a voltage to be instructed only at the start-up for a predetermined time,
2. The DC motor driving apparatus according to claim 1, wherein the voltage of the rotation speed instruction means is gradually increased simultaneously with energization. Comprising a third switch means operating with the output voltage drop diagnostic means;
The third switch means is configured to short-circuit the positive potential and the zero potential of the time constant circuit,
3. The DC motor drive apparatus according to claim 2, wherein the time constant circuit is forcibly discharged when the output voltage drop diagnosis means determines that the output voltage has dropped. A ceiling-embedded ventilator equipped with the DC motor drive device according to any one of claims 1 to 3.

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