JP3386786B2 - 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 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, reference numeral 1 is an AC power source. Reference numeral 2 denotes a voltage doubler rectifier circuit that converts the AC voltage of the AC power supply 1 into a DC voltage, and includes diodes 2a to 2b and capacitors 2c to.
2d is 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 to the respective transistors in parallel and in opposite directions.

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.

[0012]

However, in the conventional configuration 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 motor, which suppresses a decrease in efficiency at low rotation speeds.

[0014]

In order to achieve this object, an operation control device for a DC motor according to the present invention comprises a rectifying section for converting an AC input voltage into two kinds of high and low DC voltages, and a plurality of semiconductor switches. Inverter circuit with bridge connection,
A DC motor driven by the inverter circuit, before
The rotation position of the DC motor rotor is detected and rotated.
Position detection circuit for generating rolling pulse, and the position detection circuit
A rotation number detection circuit which counts the rotation pulse, and the rotational speed command circuit for instructing a rotational speed of said DC motor, said rotary
With the rotation speed command signal of the rotation speed command circuit and the rotation speed detection circuit
Duty to match the detected actual speed
A duty setting circuit that outputs a value and a low DC voltage of the rectification unit is selected when the command rotation speed of the rotation speed command circuit is low, and a high DC voltage of the rectification unit is selected when the command rotation speed of the rotation speed command circuit is high. It has a configuration of a rectification unit switching circuit that selects a voltage.

In another configuration, a switching limiting circuit is configured to perform switching when the rectifier switching circuit selects a high DC voltage and the rotation speed of the DC motor is below a certain rotation speed. Have

[0016]

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.

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

[0018]

EXAMPLE 1 An example 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, diodes 14a-14d are provided.
Are connected in a bridge configuration, the input of which is connected to the AC power supply 1. The + side of the output is the capacitor 14
It is connected to e and is supplied to the inverter circuit 3 as + power supply. 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 it is rotating at a low speed, the rectification unit switching circuit 13 rectifies the rectification unit 1
4 has been switched to a lower voltage. That is, relay 14
g is OFF, and the rectifier circuit operates as a normal bridge rectifier circuit. In other words, the output is about 140V (A
C input is 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 when switching is performed, the current 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, 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 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 way 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 rectifying 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) to supply power 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 an operation control device for a DC motor 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 reference numerals. 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 a 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 is a detailed circuit of the back electromotive voltage detection circuit 17.

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.

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

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 it is rotating at a low speed, the rectification unit switching circuit 13 rectifies the rectification unit 1
4 has been switched to a lower voltage. That is, relay 14
g is OFF, and the rectifier circuit operates as a normal bridge rectifier circuit. In other words, the output is about 140V (A
C input is 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 when switching is performed, acceleration is performed at once, and overcurrent protection (not shown) is applied to stop the operation. 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, the case where the rotation speed commanded by the rotation speed command circuit 7 becomes low speed rotation again will be described. 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 rotation speed, 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, the rectifying unit 14 is switched in order to prevent a large deceleration, 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. 4 and 5.

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 component of the counter 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 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 kinds 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.

[0063]

As described above, according to the present invention, since a plurality of power supplies can be supplied to the inverter circuit, the voltage can be lowered at a low rotation speed, and the ON ratio of the chopping duty can be increased. It is possible to suppress a decrease in efficiency.

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 section 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.

[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 Compositing circuit 12 drive circuit 13 Rectifier switching circuit 14 Rectifier 15 Switching limit circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-105583 (JP, A) JP-A-4-156291 (JP, A) JP-A-4-161090 (JP, A) JP-A-2- 79775 (JP, A) JP 58-54884 (JP, A) JP 61-170292 (JP, A) JP 56-150991 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 6/06 H02M 7/06 H02M 7/5387

Claims (2)

(57) [Claims] 1. A rectification unit for converting an AC input voltage into two types of high and low DC voltages, an inverter circuit in which a plurality of semiconductor switches are bridge-connected, a DC motor driven by the inverter circuit, and a DC motor of the DC motor. Rotor times
Position detection that detects rotation position and generates rotation pulse
Counts the rotation pulses of the output circuit and the position detection circuit
That a rotational speed detecting circuit, a rotation speed command circuit for instructing a rotational speed of the DC motor, the rotation speed instruction of the rotation speed command circuit
Signal and the actual speed detected by the speed detection circuit
The duty setting that outputs the duty value so that
A constant circuit and a rectifier that selects a low DC voltage of the rectification unit when the command rotation speed of the rotation speed command circuit is low, and selects a high DC voltage of the rectification unit when the command rotation speed of the rotation speed command circuit is high. An operation control device for a DC motor, which includes a part switching circuit. In claim 1 in which the rotational speed of the DC motor and a switching limiting circuit which is adapted to switch when below a certain rotational speed when wherein rectifier unit switching circuit selects the high DC voltage The operation control device of the DC motor described .