JPH0614581A - Operation controller for dc motor - Google Patents

Abstract

PURPOSE:To provide an operation controller for controlling the number of revolution of a DC motor through PWM control in which ON duty of chopping is prevented from lowering at the time of low r.p.m. and thereby lowering of efficiency is suppressed at low r.p.m. while enhancing the reliability of circuit components. CONSTITUTION:A commutating section switching circuit 13 selects a low voltage conversion circuit, i.e., a commutation circuit 13, in a commutating section 14 for low r.p.m. of a DC motor 4 while selects a high voltage conversion circuit, i.e., a double voltage commutation circuit, in the commutating section 14 for high r.p.m. of the DC motor 4. Since ON duty of chopping can be increased even for low r.p.m., lowering of efficiency can be suppressed at the time of low r.p.m. while furthermore reliability of circuit components can be enhanced by providing a switching limit circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor operation control device for controlling the number of revolutions using PWM control of a DC motor.

[0002]

2. Description of the Related Art In recent years, DC motors are highly efficient and
The range of applications is expanding due to the ease of controlling the rotation speed.

A conventional operation control method for a DC motor will be described below. Generally, the control of the rotation speed of the DC motor is
This is done by controlling the voltage applied to the electric motor.
In recent years, PWM control has been widely used as a method of changing this voltage. For example, the number of revolutions can be controlled by turning on / off the semiconductor switch on one side of the inverter circuit at a chopping frequency higher than the drive frequency. At this time, the voltage is adjusted by the on-off ratio of the chopping duty.

As an example of this method, for example, JP-A-63 / 1988
There is a method disclosed in Japanese Patent No. 234893. Hereinafter, such a conventional DC motor operation control device will be described with reference to the drawings.

FIG. 6 is a block diagram of a conventional DC motor operation controller. In FIG. 6, 1 is an AC power supply. Reference numeral 2 is a voltage doubler rectifier circuit that converts the AC voltage of the AC power supply 1 into a DC voltage, and has a configuration in which diodes 2a to 2b and capacitors 2c to 2d are connected.

Reference numeral 3 is an inverter circuit, in which semiconductor switches (transistors) 3a to 3f are connected in a three-phase bridge, and diodes 3g to 3l are connected in parallel and in opposite directions to the respective transistors.

A DC motor 4 is driven by the output of the inverter circuit 3. A position detection circuit 5 detects a rotational position of a rotor (not shown) of the DC motor 4 and generates a rotation pulse, and detects a position from a counter electromotive voltage of the DC motor 4.

Reference numeral 6 is a commutation circuit for producing a signal for commutating the semiconductor switches 3a to 3f of the inverter circuit 3 from the output of the position detection circuit 5. Reference numeral 7 denotes a rotation speed command circuit, which generates a rotation speed command signal for the DC motor 4. Reference numeral 8 denotes a rotation speed detection circuit, which is the position detection circuit 5
The rotation pulse of is counted for a certain period (for example, 0.5 seconds).

Reference numeral 9 denotes a duty setting circuit, which is adapted to match the rotation speed command signal of the rotation speed command circuit 7 and the actual rotation speed detected by the rotation speed detection circuit 8 so that they coincide with each other. Output the duty value. Reference numeral 10 is a chopping signal generation circuit, which produces a waveform having a different on / off ratio at a constant frequency in accordance with the duty value in order to make the rotation speed of the DC motor 4 variable.

Reference numeral 11 is a combining circuit for combining the output of the commutation circuit 6 and the output of the chopping signal generating circuit 10, and chops only one side arm of the inverter circuit 3. 12 is according to the output of the synthesis circuit 11,
A drive circuit for operating the semiconductor switches 3a to 3f of the inverter circuit 3.

[0011]

However, in the conventional structure as described above, the rotation speed is controlled only by changing the on / off ratio of the chopping duty, so that the chopping duty is controlled at a low rotation speed. There is a problem that the efficiency is lowered due to the decrease of the ON ratio.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an operation control device for a DC electric motor, which suppresses a decrease in efficiency at low rotation speeds.

[0013]

To achieve this object, a DC motor operation control apparatus according to the present invention includes a rectifier circuit for converting an AC input voltage into a plurality of DC voltages, a plurality of semiconductor switches and diodes. A bridge-connected inverter circuit, a DC motor that operates by the inverter circuit, a position detection circuit that detects the position of the rotor of the DC motor, and the operation of the semiconductor switch of the inverter circuit based on the output of the position detection circuit. A commutation circuit that determines
A chopping signal generation circuit that generates a signal for performing chopping that makes the rotation speed of the DC motor variable;
A combination circuit that combines the output of the commutation circuit and the output of the chopping signal generation circuit, a drive circuit that turns on / off a semiconductor switch of the inverter circuit by the output of the combination circuit, and a rotation speed of the DC motor When the rotation speed is low, select a low DC voltage conversion of the rectification unit,
A rectifying section switching circuit that selects high DC voltage conversion of the rectifying section when the DC motor has a high rotational speed, and a rotating speed of the DC motor when the rectifying section switching circuit selects a high DC voltage. Has a configuration of a switching limiting circuit that prohibits switching when the rotational speed is equal to or higher than a certain number of revolutions.

In another configuration, the back electromotive force detection circuit for detecting the back electromotive force voltage generated from the DC motor and the back electromotive force detection circuit when the rectifying section switching circuit selects a high DC voltage. It has a configuration of a switching limiting circuit that prohibits switching when the output voltage is equal to or higher than a certain voltage.

[0015]

With this configuration, the rectifier switching circuit selects the low DC voltage conversion of the rectifier when the rotation speed of the DC motor is low, and when the rotation speed of the DC motor is high. Select a high DC voltage conversion of the rectifier. As a result, the on ratio of the chopping duty can be increased even at a low rotation speed, so that the efficiency reduction at a low rotation speed can be suppressed.

In order to prevent switching from a high speed to a low speed at a certain speed or more, reverse current from the DC motor side can be prevented at the time of switching and the reliability of the circuit is remarkably improved. To do.

In another configuration, a switching limiting circuit for prohibiting switching when the counter electromotive voltage generated from the DC motor is equal to or higher than a certain voltage is provided to prevent switching when the counter electromotive voltage is higher than the power supply voltage. Backflow of current from the DC motor side can be prevented, and the reliability of the circuit is significantly improved.

[0018]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an operation control device for a DC motor according to an embodiment of the present invention.

In FIG. 1, the same components as those in the block diagram of the conventional DC motor operation control device shown in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 13 is a rectifying section switching circuit, which outputs a signal so as to generate a high voltage in the rectifying section 14 when the command rotational speed of the rotational speed command circuit 7 is equal to or higher than a preset rotational speed, and preset. When the rotation speed is lower than the specified speed, a signal is output so as to generate a low voltage in the rectification unit.

Reference numeral 14 is a rectifying unit, which converts an AC input voltage into a plurality of DC voltages (140 V and 280 V at AC100 V input in this embodiment) by the rectifying unit switching circuit 13.

Reference numeral 15 denotes a switching limiting circuit, which prevents the rectifier switching circuit 13 from switching a high voltage to a low voltage when the output of the rotation speed detection circuit 8 is higher than a preset rotation speed. .

A detailed circuit of the rectifying section 14 is shown in FIG.
In FIG. 2, the diodes 14a to 14d are connected in a bridge configuration, and their inputs are connected to the AC power supply 1. The + side of the output is connected to the capacitor 14e and is supplied to the inverter circuit 3 as + power source. The negative side of the output is connected to the capacitor 14f and is supplied to the inverter circuit 3 as a negative power source.

The relay 14g has a diode 14c and 1
It is connected between the connection point of 4d and the connection point of capacitors 14e and 14f.

Next, the operation of the embodiment will be described with reference to FIGS. First, the operation when the rotation speed commanded by the rotation speed command circuit 7 is a low speed rotation will be described.
Since the rotation speed is low, the rectification unit switching circuit 13 switches the rectification unit 14 to a low voltage. That is, the relay 14g is OFF, and the rectifier circuit operates as a normal bridge rectifier circuit. In other words, the output is about 140V
(AC input 100V).

Next, the operation when the rotation speed commanded by the rotation speed command circuit 7 becomes a high speed rotation will be described.
Since high-speed rotation is not possible with the current voltage, the relay 14g is turned on by the rectifier switching circuit 13. At this time, the rectifier circuit operates as a voltage doubler rectifier circuit, so that the output becomes about 280V.

If the PWM duty remains low at this switching time, the speed is accelerated at once, so overcurrent protection (not shown) is applied and the operation stops. In order to prevent this, at the same time when the rectifying unit 14 is switched, the duty setting circuit 9 generates a duty that is about 1/2 of that before switching. This operation prevents a large acceleration before and after switching.

Next, a description will be given of the case where the rotation speed commanded by the rotation speed command circuit 7 becomes low speed rotation again. Since the rotation speed is low, the rectifying unit switching circuit 13 tries to switch the rectifying unit 14 to the low voltage side. However, since the rotation speed detected by the rotation speed detection circuit 8 is still high, the switching restriction circuit 15 restricts the switching.

Therefore, the duty becomes smaller and smaller due to the control of the rotation speed, and the rotation speed gradually decreases. Then, the rotation speed decreases, and the switching limiting circuit 15
When the number of revolutions set in advance is reached, the rectifying unit can be switched.

Also at this time, in the same manner as before, the rectifying unit 14 is switched to prevent a large deceleration, and at the same time, the duty setting circuit 9 generates a duty about twice that before the switching, thereby performing a large deceleration before and after the switching. Prevent.

Therefore, when the rotation speed commanded by the rotation speed command unit 7 is a low rotation speed, a low DC voltage is output from the rectification unit 14, and when the rotation speed commanded is a high rotation speed, a high DC voltage is output. Becomes

As described above, according to this embodiment, the rectifying unit 1
The output voltage of No. 4 is a plurality of DC voltages (in the case of the present embodiment, it is 140V when AC100V is input by the rectifier switching circuit 13).
And 280 V) and the power is supplied to the inverter circuit 3, the voltage can be reduced at a low rotation speed and the ON ratio of the chopping duty can be increased, so that the efficiency reduction at a low rotation speed can be suppressed. .

Further, a switching limiting circuit 15 is provided to prevent the rectification unit switching circuit 13 from switching a high voltage to a low voltage when the output of the rotation speed detection circuit 8 is higher than a preset rotation speed. Therefore, especially when switching from the high speed rotation side to the low speed rotation side,
In order to prevent switching unless the current rotational speed is lower than a predetermined rotational speed, switching is performed when the counter electromotive voltage of the DC motor 4 is sufficiently lower than the power supply voltage to be switched next, so that counter electromotive voltage <power supply voltage. However, the current does not flow backward, the diodes 3g to 3l are not damaged, and the reliability of the circuit is significantly improved.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of a DC motor operation control apparatus according to the second embodiment of the present invention.

In FIG. 3, the same components as those in the block diagram of the operation control device for the DC motor in the embodiment shown in FIG. 1 and the block diagram of the operation control device for the conventional DC motor shown in FIG. 6 have the same numbers. Is attached and the description is omitted.

Reference numeral 16 denotes a switching limiting circuit, which prevents the rectifier switching circuit 13 from switching the high voltage to the low voltage when the counter electromotive voltage generated in the DC motor 4 is higher than a preset voltage. To do.

Reference numeral 17 is a counter electromotive voltage detection circuit for detecting the counter electromotive voltage generated in the DC motor 4, and here, it is detected from one of the three phase outputs.

The counter electromotive voltage detection circuit 17 will be described in more detail with reference to FIG. FIG. 4 shows the back electromotive force detection circuit 17
It is a detailed circuit of.

In FIG. 4, 17a is an OR gate, which is a U-phase (upper) commutation signal Su and a U-phase (lower) commutation signal Sx.
Is input in negative logic.

Reference numeral 17b is an AND gate, to which the output of the OR gate 17a and the chopping signal Sch are input.

An analog switch 17c receives the U-phase output voltage Vu as an input, and its ON / OFF control is performed by the output of the AND gate 17b.

Reference numeral 17d is a sample hold circuit, which holds the output of the analog switch 17c. The output Sout of the sample hold circuit 17d is output to the switching limiting circuit 16 as the output of the back electromotive force detection circuit.

Next, the operation of the embodiment will be described with reference to FIGS. 2, 3 and 4. First, the operation when the rotation speed commanded by the rotation speed command circuit 7 is a low speed rotation will be described. Since the rotation speed is low, the rectification unit switching circuit 13 switches the rectification unit 14 to a low voltage. That is, the relay 14g is OFF, and the rectifier circuit operates as a normal bridge rectifier circuit. That is, the output is about 1
It is 40V (AC input 100V).

Next, the operation when the rotation speed commanded by the rotation speed command circuit 7 becomes a high speed rotation will be described.
Since high-speed rotation is not possible with the current voltage, the relay 14g is turned on by the rectifier switching circuit 13. At this time, the rectifier circuit operates as a voltage doubler rectifier circuit, so that the output becomes about 280V.

If the PWM duty remains low at the time of this switching, it is accelerated at once, so overcurrent protection (not shown) is applied and it stops. In order to prevent this, at the same time when the rectifying unit 14 is switched, the duty setting circuit 9 generates a duty that is about 1/2 of that before switching. This operation prevents a large acceleration before and after switching.

Next, description will be made regarding the case where the rotation speed commanded by the rotation speed command circuit 7 becomes low speed rotation again. Since the rotation speed is low, the rectifying unit switching circuit 13 tries to switch the rectifying unit 14 to the low voltage side. However, since the voltage detected by the back electromotive voltage detection circuit 17 is still high, the switching restriction circuit 16 restricts the switching so that the switching is not performed.

Therefore, the duty becomes smaller and smaller due to the control of the number of revolutions, and the back electromotive force gradually decreases. Then, when the back electromotive voltage decreases and reaches the voltage preset in the switching limiting circuit 15, the rectifying unit can be switched.

Also at this time, as before, in order to prevent a large deceleration, the rectifying unit 14 is switched, and at the same time, the duty setting circuit 9 generates a duty approximately twice that before the switching so that a large deceleration is performed before and after the switching. Prevent.

Next, a more detailed operation of the counter electromotive voltage detection circuit 17 will be described with reference to FIGS.

FIG. 5 is a timing chart showing an example of each input / output signal of the counter electromotive voltage detection circuit 17.

The U-phase (upper) commutation signal Su, the U-phase (lower) commutation signal Sx, and the chopping signal Sch produce a U-phase output voltage Vu having a waveform as shown in FIG. The portion indicated by a thick line in this waveform is the back electromotive force of the DC motor 4.

Therefore, according to the logics of the OR gate 17a and the AND gate 17b, both the U-phase (upper) commutation signal Su and the U-phase (lower) commutation signal Sx are Low (OFF), and the chopping signal Sch is High. When (ON), the analog switch 17c is turned ON, and the U-phase output voltage Vu
Is sent to the sample hold circuit 17d and the signal is held.

As a result, the output signal Sout can detect only the counter electromotive voltage component of the DC motor 4 in the output waveform as shown in FIG.

As described above, according to this embodiment, the switching limiting circuit 16 and the counter electromotive voltage detection circuit 17 are provided, and when the counter electromotive voltage of the DC motor 4 is higher than the preset voltage, the rectification is performed. Since it is possible to prevent the high voltage from being switched to the low voltage by the section switching circuit 13, especially when switching from the high-speed rotation side to the low-speed rotation side, the current counter-electromotive voltage must be equal to or lower than the predetermined voltage for switching. Therefore, the back electromotive force of the DC motor 4 is switched when it is sufficiently lower than the power supply voltage to be switched next.
The counter electromotive voltage becomes less than the power supply voltage, and the current never flows backward.
The diodes 3g to 3l are not damaged, and the reliability of the circuit is significantly improved.

Further, by providing the analog switch 17c which is turned on / off according to the condition of the commutation signal / chopping signal and the sample hold circuit 17d which holds the voltage, only the counter electromotive voltage component of the DC motor 4 in the output voltage is provided. Since the extraction can be reliably performed, malfunction due to the influence of the output voltage or the like is eliminated.

In this embodiment, the rectifying section is a shared DC power supply circuit, but it may be one having two types of DC voltage conversion or one capable of linear conversion (for example, a chopper). Needless to say, the number of DC voltage conversions may be increased.

[0059]

As described above, according to the present invention, a plurality of power supplies can be supplied to the inverter circuit by providing the rectifier switching circuit for converting the output voltage of the rectifier into a plurality of DC voltages. Since the voltage can be reduced and the on ratio of the chopping duty can be increased, it is possible to suppress the efficiency reduction at low rotation speed.

Further, when the output of the rotation speed detection circuit is higher than the preset rotation speed, by providing the switching limiting circuit which prevents the rectification unit switching circuit from switching the high voltage to the low voltage, Especially when switching from the high-speed rotation side to the low-speed rotation side, if the counter electromotive voltage of the DC motor is sufficiently lower than the power supply voltage to be switched next, in order not to switch unless the current rotation speed is below a predetermined rotation speed. Since the counter electromotive voltage is smaller than the power supply voltage, the current does not flow backward, the circuit components are not damaged, and the reliability of the circuit is significantly improved.

Further, by providing the switching limiting circuit and the counter electromotive voltage detecting circuit, when the counter electromotive voltage of the DC motor is higher than the preset voltage, the rectifying section switching circuit converts the high voltage into the low voltage. Since it is possible to prevent the switching, especially when switching from the high-speed rotation side to the low-speed rotation side, the counter electromotive voltage of the DC motor is When the voltage is sufficiently lower than the power supply voltage that can be switched to, the counter electromotive voltage is less than the power supply voltage, the current does not flow backward, damage to circuit parts is prevented, and the reliability of the circuit is significantly improved. Become.

Further, by providing the analog switch 17c which is turned on / off according to the condition of the commutation signal / chopping signal and the sample hold circuit 17d which holds the voltage, only the counter electromotive voltage component of the DC motor 4 in the output voltage is provided. Since the extraction can be reliably performed, malfunction due to the influence of the output voltage or the like is eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram of an operation control device for a DC motor according to an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of a rectifying unit 14 according to an embodiment.

FIG. 3 is a block diagram of a DC motor operation control device according to a second embodiment of the present invention.

FIG. 4 is a detailed circuit diagram of a counter electromotive voltage detection circuit 17 of the embodiment.

FIG. 5 is a timing chart showing an example of the operation of the counter electromotive voltage detection circuit of the embodiment.

FIG. 6 is a block diagram of a conventional DC motor operation control device.

[Explanation of symbols]

 3 Inverter Circuit 4 DC Motor 6 Commutation Circuit 10 Chopping Signal Generation Circuit 11 Combining Circuit 12 Drive Circuit 13 Rectifier Switching Circuit 14 Rectifier 15 Switching Limit Circuit

Claims (3)

[Claims] 1. A rectifying unit for converting an AC input voltage into a plurality of DC voltages, an inverter circuit in which a plurality of semiconductor switches and diodes are bridge-connected, a DC motor operated by the inverter circuit, and a rotation of the DC motor. A position detection circuit that detects the position of the child, a commutation circuit that determines the operation of the semiconductor switch of the inverter circuit based on the output of the position detection circuit, and chopping that makes the rotation speed of the DC motor variable. Signal generating circuit, a combining circuit that combines the output of the commutation circuit and the output of the chopping signal generating circuit, and the semiconductor switch of the inverter circuit is turned on / off by the output of the combining circuit. When the rotation speed of the drive circuit and the electric motor is low, select the low DC voltage conversion of the rectification unit. A rectifying section switching circuit that selects high DC voltage conversion of the rectifying section when the rotational speed of the DC electric motor is high, and a rotation of the DC electric motor when the rectifying section switching circuit selects a high DC voltage. A DC motor operation control device having a switching limiting circuit that prohibits switching when the number of rotations is a certain number or more. 2. A rectifying unit for converting an AC input voltage into a plurality of DC voltages, an inverter circuit in which a plurality of semiconductor switches and diodes are bridge-connected, a DC motor operated by the inverter circuit, and a rotation of the DC motor. A position detection circuit that detects the position of the child, a commutation circuit that determines the operation of the semiconductor switch of the inverter circuit based on the output of the position detection circuit, and chopping that makes the rotation speed of the DC motor variable. Signal generating circuit, a combining circuit that combines the output of the commutation circuit and the output of the chopping signal generating circuit, and the semiconductor switch of the inverter circuit is turned on / off by the output of the combining circuit. When the rotation speed of the drive circuit and the electric motor is low, select the low DC voltage conversion of the rectification unit. A rectifier switching circuit that selects high DC voltage conversion of the rectifier when the rotational speed of the DC motor is a high rotational speed; a counter electromotive voltage detection circuit that detects a counter electromotive voltage generated from the DC motor; A DC motor operation control device comprising a switching limiting circuit for prohibiting switching when the output voltage of the back electromotive force detection circuit is equal to or higher than a certain voltage when the rectifier switching circuit selects a high DC voltage. 3. An analog switch for turning on / off an output voltage by logic combination of an output of the commutation circuit and an output of the chopping signal generating circuit by a counter electromotive voltage detection circuit, and a sample for holding an output of the analog switch. The operation control device for the DC motor according to claim 2, comprising a hold circuit.