JP3279644B2 - 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 which counts rotation pulses of the position detection circuit 5 for a predetermined period (for example, 0.5 seconds).

Reference numeral 9 denotes a duty setting circuit. The duty setting circuit 9 determines a duty cycle between the rotation speed command signal from the rotation speed command circuit 7 and the actual rotation speed detected by the rotation speed detection circuit 8 so that they match. Output the 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 according to the output of the synthesizing circuit 11,
This is a drive circuit for operating the semiconductor switches 3a to 3f of the inverter circuit 3.

[0011]

However, in the prior art as described above, the rotation speed is controlled only by changing the ratio of the chopping duty on to off. However, there is a problem that the efficiency is reduced due to the decrease in the ratio of.

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]

In order to achieve this object, a DC motor operation control device according to the present invention comprises a rectifier for converting an AC input voltage into two types of high and low DC voltages, and a plurality of semiconductor devices. 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 for determining the operation of the semiconductor switch; and a rotation speed finger for instructing the rotation speed of the DC motor.
Control circuit, and a rotation speed detector for detecting the rotation speed of the DC motor.
Output circuit, the rotation speed of the rotation speed command and the rotation speed detection time.
Duty so that the rotational speed detected by the road matches
A duty setting circuit for outputting a duty command; and
A chopping signal generating circuit for generating a signal for chopping Te, a combining circuit for combining the outputs of said chopping signal generating circuit of the commutation circuit, the semiconductor switch of the inverter circuit by the output of the combining circuit a drive circuit for the on / off, before Symbol command rotational speed of the rotating speed command circuit when the low-speed and select a lower DC voltage conversion of the rectification section, the command rotational speed is high rpm of the rotational speed command circuit A rectifying section switching circuit for selecting a high DC voltage conversion of the rectifying section ,
The section switching circuit determines the duty command in advance.
When the duty ratio is smaller than the determined minimum duty value.
Section, select a low DC voltage conversion, and
Command is greater than the predetermined maximum duty value
Sometimes selecting high DC voltage conversion of the rectifier
It is .

Further, when the DC voltage conversion of the rectifying unit is switched, a chopping signal correction circuit for correcting the chopping signal is provided.

[0015]

With this configuration, the rectification switching circuit has
When the rotation speed of the DC motor is low, a low DC voltage conversion of the rectifying unit is selected, and when the rotation speed of the DC motor is high, a high DC voltage conversion of the rectification unit 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, by providing a chopping signal correction circuit, when the DC voltage conversion of the rectifier is switched, the chopping signal is corrected. As a result, a temporary increase in the DC motor input current when switching from a low DC voltage to a high DC voltage can be suppressed, so that it is possible to smoothly switch the rotation speed and downsize components.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first 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 a first embodiment of the present invention.

FIG. 1 is a block diagram of an operation control device for a DC motor, and the same reference numerals are given to the same components as those in the related art, and detailed description thereof will be omitted.

A rectifier switching circuit 13 outputs a rectifier switching signal 'L' to a rectifier 14 to be described later when the duty command of the duty setting circuit 9 is smaller than a predetermined minimum duty value d1. When the duty command is larger than a predetermined maximum duty value d2, a rectifier switching signal 'H' is output to the rectifier 14.

A rectifier 14 converts an AC input voltage into a plurality of DC voltages. FIG. 2 shows a detailed circuit of the rectifier 14.

In FIG. 2, reference numeral 2 denotes a voltage doubler rectifier circuit having the same configuration as that shown in FIG. Reference numeral 15 denotes a rectifier circuit, which includes diodes 15a to 15d and a capacitor 15e. It is needless to say that there are other methods of configuring the rectifier 14, and the circuit shown in FIG. 2 is an example.

Reference numerals 16 and 17 denote an input switch and an output switch, respectively. As shown in Table 1, when the rectifier switching signal is "H", the input switch and the output switch are connected to the contacts 16a and 17a, respectively. Then, rectification is performed by the voltage doubler rectifier circuit 2. When the rectifier switching signal is "L", the input switch and the output switch are connected to the contacts 16b and 17b, respectively, and perform rectification by the rectifier circuit 15.

[0024]

[Table 1]

Next, the operation of the rectifier switching circuit 13 and the rectifier 14 will be described with reference to FIG.

First, in step 101, the duty setting circuit 9 compares a rotation speed command value of the rotation speed command circuit 7 with a rotation speed detection value of the rotation speed detection circuit 8, and determines that the rotation speed detection value is smaller. If so, the process proceeds to step 102, where the duty value is increased.

Next, in step 103, the rectifier switching circuit 13 compares the duty value set in step 102 with the maximum duty value d2, and if the set duty value is d2 or more, the process proceeds to step 104. , D2, the flow returns to step 101. In step 104, the rectification switching circuit 13 outputs a rectification unit switching signal 'H'. In step 105, the voltage doubler rectification circuit 2 of the rectification unit 14 is selected, and the process returns to step 101 again.

Next, if the detected rotation speed is not small in step 101, the process proceeds to step 106, and if the detected rotation speed is large, the process proceeds to step 107 to reduce the duty value. When the rotation detection value is equal to the rotation speed command value in step 106, the process returns to step 101 again.

Next, at step 108, the rectifier switching circuit 13 compares the duty value set at step 107 with the minimum duty value d1, and if the set duty value is equal to or less than d1, proceeds to step 109. The process proceeds, and when it is larger than d1, the process returns to step 101. In step 109, the rectification unit switching circuit 13 outputs a rectification unit switching signal 'L'. In step 110, the rectification circuit 13 of the rectification unit 14 is selected, and the process returns to step 101 again.

Therefore, the rectifier circuit 13 that outputs a low DC voltage is selected when the rotation speed of the DC motor 4 is low, and a high DC voltage is output when the rotation speed of the DC motor 4 is high. The output voltage doubler rectifier circuit 2
Will be 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.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of a DC motor operation control device according to a second embodiment of the present invention.

Numeral 18 denotes a chopping correction circuit. When the duty command of the duty setting circuit 9 is equal to or greater than the maximum duty value d2, the duty command is decreased at a predetermined speed to the minimum duty value d1 to correct the duty command. The chopping signal generating circuit 10 and the rectifying unit switching circuit 1 as a duty command
3 and outputs the corrected duty value to the chopping signal generating circuit 10 and the duty command of the duty setting circuit 9 to the rectifier switching circuit 13 when the corrected duty value becomes d1. It is.

Next, the operation of the chopping signal correction circuit 18 will be described with reference to FIG. First, step 201
And the duty setting circuit 9 is adapted to
The rotation speed command value is compared with the rotation speed detection value of the rotation speed detection circuit 8. If the rotation speed detection value is small, the process proceeds to step 202, and the duty value is increased.

Next, in step 203, the rectifier switching circuit 13 compares the duty value set in step 202 with the maximum duty value d2, and if the set duty value is equal to or more than d2, the process proceeds to step 204. , D2, the flow returns to step 201.

In step 204, the chopping signal correction circuit 18 reduces the set duty value from the maximum duty value d2 at a predetermined predetermined speed, and outputs the chopping signal generation circuit 10 and the rectification as a correction duty command. Output to the section switching circuit 13.

Next, at step 205, the chopping signal correction circuit 18 compares the correction duty value set at step 204 with the minimum duty value, and if the correction duty value is less than d1, proceeds to step 206. When it is larger than d1, the process returns to step 201. In step 206, the rectifying unit switching circuit 13 outputs the rectifying unit switching signal 'H'. In step 207, the voltage doubler rectifying circuit 2 of the rectifying unit 14 is selected, and the process returns to step 201 again.

Next, if the detected rotation speed is not small in step 201, the process proceeds to step 208, and if the detected rotation speed is large, the process proceeds to step 209 to decrease the duty value. When the rotation detection value is equal to the rotation command value in step 208, step 2 is performed again.
Return to 01.

Next, at step 210, the rectifier switching circuit 13 compares the duty value set at step 209 with the minimum duty value d1, and if the set duty value is less than d1, the process proceeds to step 211. , D1 returns to step 201. In step 211, the rectifying unit switching circuit 13 outputs a rectifying unit switching signal 'L'. In step 212, the rectifying circuit 13 of the rectifying unit 14 is selected, and the process returns to step 101 again.

For this reason, the rectifier circuit 13 that outputs a low DC voltage is selected when the rotation speed of the DC motor 4 is low, and a high DC voltage is output when the rotation speed of the DC motor 4 is high. The output voltage doubler rectifier circuit 2
Will be 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, the rectifier circuit 1 of the rectifier 14
3 is switched to the voltage doubler rectifier circuit 2, by temporarily reducing the duty value in the chopping signal correction circuit 18, it is possible to suppress a temporary increase in the input current of the DC motor 4 at the time of switching. In addition, the rotation can be smoothly switched, and the size of parts can be reduced.

Although the rectifier has been described as having two types of DC voltage conversion in this embodiment, it is needless to say that the number of types of DC voltage conversion may be further increased.

[0044]

The present invention as described above, according to the present invention, the rectifier unit switching circuit, selects the low DC voltage converter of the rectifier unit when less than the minimum duty value duty command is predetermined, and decide the duty command beforehand When the duty ratio is larger than the maximum duty value, a high DC voltage conversion of the rectifier is selected. For this reason, the DC voltage supplied from the rectifier to the inverter can be selected from two types, high and low. When the chopping duty is small, by selecting a low voltage of the rectifier, the ON ratio of the chopping duty can be increased. It is possible to suppress a decrease in efficiency at a low rotation speed. Moreover, the load is small
When the rotation speed increases, the duty value decreases.
If the need to reduce
By switching to pressure, the duty value can be increased,
Duty value becomes too small with high DC voltage
A decrease in efficiency can be prevented.

Also, a rectifier 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 for detecting a position of a child, 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 rotation speed command circuit for generating a rotation command signal for the DC motor. A chopping signal generation circuit that generates a signal for performing chopping that varies the rotation speed of the DC motor according to the rotation speed command signal, and combines an output of the commutation circuit and an output of the chopping signal generation circuit. And a driver for turning on / off a semiconductor switch of the inverter circuit by an output of the combining circuit. When the rotational speed command signal has a low rotational speed, the low DC voltage conversion of the rectifier is selected, and when the rotational speed of the rotational speed command signal is a high rotational speed, the high DC voltage conversion of the rectifier is performed. Since the rectifying unit switching circuit to be selected and the chopping signal correcting circuit for correcting the chopping signal when switching the DC voltage conversion of the rectifying unit, the chopping signal correcting circuit includes a DC voltage of the rectifying unit. When switching the conversion, the chopping signal is corrected. As a result, a temporary increase in the DC motor input current when switching from a low DC voltage to a high DC voltage can be suppressed, so that it is possible to smoothly switch the rotation speed and downsize components.

[Brief description of the drawings]

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

FIG. 2 is a detailed circuit diagram of a rectifier of FIG. 1;

FIG. 3 is a flowchart showing the operation of the rectifier switching circuit and the rectifier of FIG. 1;

FIG. 4 is a block diagram of a DC motor operation control device according to a second embodiment of the present invention;

FIG. 5 is a flowchart showing the operation of the rectifier switching circuit and the rectifier of FIG. 4;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 Inverter 4 DC motor 6 Commutation circuit 10 Chopping signal generation circuit 11 Synthesis circuit 12 Drive circuit 13 Rectifier switching circuit 14 Rectifier 18 Chopping signal correction circuit

Continuation of front page (56) References JP-A-4-161090 (JP, A) JP-A-2-79775 (JP, A) Patent 3159524 (JP, B2) (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 detecting circuit for detecting the position of the rotor of the DC motor, a commutation circuit for determining the operation of the semiconductor switches of the inverter circuit based on an output of said position detecting circuit, the DC motor
Rotation speed command circuit for commanding the rotation speed of the DC motor
A rotation speed detection circuit for detecting the rotation speed of the motor;
Rotation speed and the rotation speed detected by the rotation speed detection circuit
Output duty command so that
A setting circuit and a variable speed of the DC motor .
A chopping signal generating circuit for generating a signal for performing chopping according to the duty command; a synthesizing circuit for synthesizing an output of the commutation circuit and an output of the chopping signal generating circuit; and an inverter based on an output of the synthesizing circuit. a drive circuit for turning on / off the semiconductor switch circuit, when the command rotational speed of the front Symbol rotation speed command circuit is in the low rotational speed and select a lower DC voltage conversion of the rectification section, the command rotational speed of the rotational speed command circuit A rectifier switching circuit that selects a high DC voltage conversion of the rectifier when the number of rotations is high , the rectifier switching circuit,
Duty command is a predetermined minimum duty
When the value is smaller than the value, the low DC voltage conversion of the rectifier is performed.
And the duty command is predetermined.
When the duty ratio is larger than the maximum duty value,
Operation control device for DC motors to select DC voltage conversion . 2. The DC motor operation control device according to claim 1, further comprising a chopping signal correction circuit that corrects a chopping signal when the DC voltage of the rectifier is switched.