JP3159524B2 - Operation control device for DC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control device for a DC motor which controls the rotation speed of the DC motor using PWM control.

[0002]

2. Description of the Related Art In recent years, DC motors have high efficiency,
Due to the easiness of rotation speed control, its application range is expanding.

[0003] A conventional operation control method for a DC motor will be described below. Generally, the control of the rotation speed of the DC motor
This is performed by controlling the voltage applied to the electric motor.
In recent years, PWM control has been widely used as a method of changing the voltage. For example, by turning on / off a semiconductor switch on one side of the inverter circuit at a chopping frequency higher than the driving frequency, it is possible to control the rotation speed. At this time, the voltage is adjusted by the ratio of the chopping duty on to off.

An example of this method is disclosed in, for example,
There is a method disclosed in JP-A-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 control device. In FIG. 6, reference numeral 1 denotes an AC power supply. Reference numeral 2 denotes a voltage doubler rectifier circuit for converting an 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 denotes 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 to the respective transistors in parallel and in opposite directions.

A DC motor 4 is driven by the output of the inverter circuit 3. Reference numeral 5 denotes a position detection circuit for detecting a rotational position of a rotor (not shown) of the DC motor 4 and generating a rotation pulse. The position detection circuit 5 detects a position from a back electromotive voltage of the DC motor 4.

Reference numeral 6 denotes a commutation circuit for generating 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, and the position detection circuit 5
Are counted for a certain period (for example, 0.5 seconds).

Reference numeral 9 denotes a duty setting circuit which determines a difference between a rotation speed command signal of the rotation speed command circuit 7 and an actual rotation speed detected by the rotation speed detection circuit 8 so that they match. Outputs the duty value. Reference numeral 10 denotes a chopping signal generation circuit which generates 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 denotes a synthesizing circuit for synthesizing the output of the commutation circuit 6 and the output of the chopping signal generation circuit 10, and chops only one arm of the inverter circuit 3. 12 is based on the output of the synthesis circuit 11
This is a drive circuit for operating the semiconductor switches 3a to 3f of the inverter circuit 3.

[0011]

However, in the above-described conventional configuration, the control of the rotational speed is performed only by changing the on / off ratio of the chopping duty. However, there is a problem that the efficiency decreases due to a decrease in the ON ratio of the LED.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an operation control device for a DC motor which suppresses a decrease in efficiency at a low rotational speed.

[0013]

Means for Solving the Problems] operation control device for a DC motor of the present invention to achieve this object, a rectifier for converting an AC input voltage to the high and low two kinds of a plurality of DC voltages, a plurality of semiconductor An inverter circuit in which a switch and a diode are bridge-connected, a DC motor operated by the inverter circuit, a position detection circuit for detecting a position of a rotor of the DC motor, and an inverter circuit based on an output of the position detection circuit. A commutation circuit that determines the operation of the semiconductor switch, a chopping signal generation circuit that generates a signal for performing chopping that varies the rotation speed of the DC motor, an output of the commutation circuit, and a chopping signal generation circuit. A synthesizing circuit for synthesizing the output and an output of the synthesizing circuit; And Eve circuit, the rotation speed command circuit for instructing a rotational speed of the DC motor, the rotation speed command circuit
When the command speed is low, the DC voltage conversion of the rectifier is selected low, and when the command speed of the speed command circuit is high, the DC voltage conversion of the rectifier is high. Rectifier switching circuit and the rotation speed of the DC motor
And the rectifier switching circuit selects a high voltage and the rotation speed detection circuit
The rectification unit is used when a rotation speed equal to or higher than a fixed rotation speed is detected.
A switching restriction circuit for prohibiting switching by the switching circuit is provided .

In another configuration, the number of rectifying units is four.
Rectifier diode is bridged by two-phase bridge connection
Circuit and the positive and negative electrodes of the bridge circuit in series.
Two connected capacitors and one of the bridge circuits
Switch connected between the input of the
Rectifier switching circuit switches to high voltage.
When switching, turn on the switch and switch the rectification.
When the circuit switches to a lower voltage, turn off the switch.
I am trying to do it .

[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. High DC voltage conversion of the rectifier is selected. As a result, the on-ratio of the chopping duty can be increased even at a low rotation speed, so that a decrease in efficiency at a low rotation speed can be suppressed.

Further, when switching from a high rotation speed to a low rotation speed, the switching cannot be performed at a certain rotation speed or more, so that a reverse current from the DC motor side can be prevented at the time of switching, and the reliability of the circuit is significantly improved. I do.

In another configuration, a switching limiting circuit for inhibiting switching when the back electromotive voltage generated from the DC motor is equal to or higher than a predetermined voltage prevents switching when the back electromotive voltage is higher than the power supply voltage, The backflow of the current from the DC motor 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 a DC motor operation control device according to an embodiment of the present invention.

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

Reference numeral 13 denotes a rectifier switching circuit, which outputs a signal so as to generate a high voltage to the rectifier 14 when the command speed of the speed command circuit 7 is equal to or higher than a preset speed. When the rotation speed is lower than the set rotation speed, a signal is output so as to generate a low voltage in the rectifier.

Reference numeral 14 denotes a rectifier, which converts an AC input voltage into a plurality of DC voltages (140 V and 280 V with AC 100 V input in this embodiment) by a rectifier 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. .

FIG. 2 shows a detailed circuit of the rectifier 14.
2, the diodes 14a to 14d are connected in a bridge configuration, and the input is connected to the AC power supply 1. The positive side of the output is connected to the capacitor 14e and is supplied to the inverter circuit 3 as + power. The negative side of the output is connected to the capacitor 14f and supplied to the inverter circuit 3 as a negative power supply.

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

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

Next, the operation when the rotation speed commanded by the rotation speed command circuit 7 becomes high speed will be described.
Since high-speed rotation is impossible with the current voltage, the relay 14g is turned on by the rectifier switching circuit 13. At this time, since the rectifier circuit operates as a voltage doubler rectifier circuit, the output becomes approximately 280V.

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

Next, the case where the rotation speed commanded by the rotation speed command circuit 7 becomes low speed again will be described. Due to the low speed rotation, the rectifying unit switching circuit 13 attempts to switch the rectifying unit 14 to a lower 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 from being performed.

For this reason, the duty is gradually reduced by controlling the rotation speed, and the rotation speed is gradually reduced. Then, the rotation speed decreases, and the switching restriction circuit 15
When the number of rotations set in advance is reached, the rectification unit can be switched.

At this time, as in the previous case, the rectifier 14 is switched to prevent a large deceleration, and at the same time, the duty setting circuit 9 generates a duty twice as large as before the switching, and performs a large deceleration before and after the switching. To prevent

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

As described above, according to the present embodiment, the rectifying unit 1
The rectifier switching circuit 13 outputs a plurality of DC voltages (140 V at the input of AC 100 V in this embodiment).
280 V) and supplies power to the inverter circuit 3, so that the voltage can be reduced at low rotation speeds and the on-ratio of the chopping duty can be increased, so that a decrease in efficiency at low rotation speeds can be suppressed. .

A switching limiting circuit 15 is provided to prevent 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. Especially when switching from high-speed rotation to low-speed rotation.
In order to prevent switching if the current rotational speed is not lower than a predetermined rotational speed, the switching is performed when the back electromotive voltage of the DC motor 4 is sufficiently lower than the power source voltage to be switched next. The current does not flow backward, and the diodes 3g to 3l are not damaged, so that the reliability of the circuit is remarkably improved.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

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

In FIG. 3, the same reference numerals as those in the block diagram of the DC motor operation control device in the embodiment shown in FIG. 1 and the block diagram of the conventional DC motor operation control device shown in FIG. And the description is omitted.

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

Reference numeral 17 denotes a back electromotive voltage detection circuit which detects a back electromotive voltage generated in the DC motor 4, and here detects the back electromotive voltage from one of three output phases.

The back electromotive voltage detection circuit 17 will be described in more detail with reference to FIG. FIG. 4 shows a back electromotive voltage detection circuit 17.
Is a detailed circuit.

In FIG. 4, reference numeral 17a denotes 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.

An AND gate 17b receives the output of the OR gate 17a and the chopping signal Sch.

Reference numeral 17c denotes an analog switch to which the U-phase output voltage Vu is input, and ON / OFF control is performed by an output of the AND gate 17b.

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

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

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 impossible with the current voltage, the relay 14g is turned on by the rectifier switching circuit 13. At this time, since the rectifier circuit operates as a voltage doubler rectifier circuit, the output becomes approximately 280V.

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

Next, the case where the rotation speed commanded by the rotation speed command circuit 7 becomes low speed again will be described. Due to the low speed rotation, the rectifying unit switching circuit 13 attempts to switch the rectifying unit 14 to a lower 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 from being performed.

Therefore, the duty is gradually reduced by controlling the rotational speed, and the back electromotive voltage is gradually reduced. When the back electromotive voltage decreases and reaches a voltage preset in the switching restriction circuit 15, the switching of the rectifying unit is enabled.

Also at this time, as in the previous case, the rectifier 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, and performs a large deceleration before and after the switching. To prevent

Next, a more detailed operation of the back 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 back electromotive voltage detection circuit 17.

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

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

As a result, the output signal Sout can detect only the component of the back electromotive voltage 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 back electromotive voltage detecting circuit 17 are provided, and when the back electromotive voltage of the DC motor 4 is higher than a preset voltage, the rectification is performed. Since the switching of the high voltage to the low voltage can be prevented by the section switching circuit 13, especially when switching from the high-speed rotation side to the low-speed rotation side, the switching is performed so that the current back electromotive voltage is not lower than a predetermined voltage. Therefore, the switching is performed when the back electromotive voltage of the DC motor 4 is sufficiently lower than the power supply voltage to be switched next.
Back electromotive voltage <power supply voltage, current does not flow back,
The diodes 3g to 3l are not damaged, and the reliability of the circuit is significantly improved.

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

In this embodiment, the rectifying unit is a shared DC power supply circuit. However, the rectifying unit may be one having two types of DC voltage conversion or one capable of linear conversion (for example, a chopper). It goes without saying that the number of DC voltage conversions may be further 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 ON ratio of the chopping duty can be increased by lowering the voltage, it is possible to suppress a decrease in efficiency at a low rotation speed.

When the output of the rotation speed detection circuit is higher than the predetermined rotation speed, a switching limiting circuit is provided to prevent the rectifier switching circuit from switching the high voltage to the low voltage. In particular, when switching from the high-speed rotation side to the low-speed rotation side, when the back electromotive voltage of the DC motor is sufficiently lower than the power supply voltage to be switched next, so that the current rotation speed cannot be switched unless the current rotation speed is equal to or lower than a predetermined rotation speed. Therefore, the back electromotive voltage <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 back electromotive voltage detection circuit, when the back electromotive voltage of the DC motor is higher than a preset voltage, the rectifier switching circuit changes the high voltage to a lower voltage. Since switching can be prevented, especially when switching from the high-speed rotation side to the low-speed rotation side, the back electromotive voltage of the DC motor is changed to the next to prevent the current back electromotive voltage from being switched unless the current back electromotive voltage is equal to or lower than a predetermined voltage. Since the switching is performed when the power supply voltage is sufficiently lower than the power supply voltage, the back electromotive voltage <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. Become.

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

[Brief description of the drawings]

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

FIG. 2 is a detailed circuit diagram of a rectifier 14 according to the 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 back electromotive voltage detection circuit 17 according to the embodiment.

FIG. 5 is a timing chart illustrating an example of the operation of the back electromotive voltage detection circuit according to the embodiment;

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

[Explanation of symbols]

 Reference Signs List 3 inverter circuit 4 DC motor 6 commutation circuit 10 chopping signal generation circuit 11 combining circuit 12 drive circuit 13 rectifying section switching circuit 14 rectifying section 15 switching limiting circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-54884 (JP, A) JP-A-61-170292 (JP, A) JP-A-63-224698 (JP, A) 56091 (JP, A) JP-A-4-312386 (JP, A) JP-A-64-50787 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/06

Claims (2)

(57) [Claims] A rectifier for converting an AC input voltage into a plurality of high and low 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; A position detection circuit for detecting a position of a rotor of the DC motor; a commutation circuit for determining an operation of a semiconductor switch of the inverter circuit based on an output of the position detection circuit; and a variable rotation speed of the DC motor. A chopping signal generating circuit for generating a signal for performing chopping, a synthesizing circuit for synthesizing an output of the commutation circuit and an output of the chopping signal generating circuit, and a semiconductor switch of the inverter circuit by an output of the synthesizing circuit. A drive circuit for turning on / off, and a rotation speed command circuit for commanding the rotation speed of the DC motor.
Road and the command rotation speed of the rotation speed command circuit when the low-speed and select a lower DC voltage conversion of the rectification section, the times
A rectifying unit switching circuit for selecting a high DC voltage conversion of the rectifying unit when a command rotational speed of the rotational speed command circuit is a high rotational speed; and a rotational speed detecting circuit for detecting a rotational speed of the DC motor.
When the rectifying portion cutting exchange example circuit has selected a high voltage
And the rotation speed detection circuit detects a rotation speed equal to or higher than a certain rotation speed.
An operation control device for a DC motor , comprising: a switching restriction circuit for prohibiting switching by the rectification unit switching circuit when the motor is in operation. 2. The rectifying section includes four rectifying diodes in two phases.
Bridge circuit with bridge connection, the bridge circuit
Capacitors connected in series between the positive and negative electrodes of
And one input of the bridge circuit and the capacitor
And a switch connected between the
When the switching circuit switches to a higher voltage, the switch
Switch, and the rectification switching circuit switches to a lower voltage.
Claims wherein the switch is turned off when changing.
2. The operation control device for a DC motor according to claim 1 .