JPH0583984A - Operation controller for dc motor - Google Patents

Abstract

PURPOSE:To eliminate circulation current, in PWM rotational speed control of DC motor, by delaying OFF operation of a semiconductor switch in the other arm for a predetermined time through an OFF delay circuit and turning other semiconductor switches ON during that time thereby avoiding a state where all semiconductor switches are turned OFF. CONSTITUTION:A commutation circuit 10 determines the operation of semiconductor switching elements 6a-6f in an inverter circuit 5 based on an output from a position detecting circuit 9 for detecting the position of the rotor of a DC motor 8. A first drive circuit 12 synthesizes outputs from a chopping signal generating circuit 11 for varying the rotational speed of the DC motor 8 and the commutation circuit 10 to produce a chopping signal for turning ON/OFF semiconductor switches 6d-6f in one side arm of the inverter circuit 5. A second drive circuit 14 delays the signal of the commutation circuit 10 through an OFF delay circuit 13 and turns other semiconductor switches 6a-6c ON/OFF thus avoiding a state where all semiconductor switches are turned OFF and eliminating circulation current.

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 electric motor, in which a reflux current generated at the time of switching is eliminated in the rotation speed control using the PWM control of the DC electric 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. There is a method for controlling the rotation speed of the DC motor, for example, as disclosed in JP-A-51-28610. This is to perform on / off control (hereinafter referred to as PWM control) of a semiconductor switch on one side of an inverter circuit at a chopping frequency higher than a drive frequency. In this method, there is a moment when all the semiconductor switches of the inverter circuit are turned off, and the energy of the winding at this time flows back to the smoothing capacitor of the rectifier circuit as a return current.

The operation will be described in more detail with reference to FIG. FIG. 7 is a schematic diagram of the operation of a conventional DC motor operation control device.

In FIG. 7A, 6a and 6f of the semiconductor switches are turned on, and the current is supplied from the DC power source E through the route shown by the solid line and the arrow. Next, when 6f is turned off by PWM control in FIG. 7B, a closed loop as shown by the solid line is formed by the action of the diode in parallel with 6c, and the current continues to flow.

Next, in FIG. 7C, when 6a is turned off by the commutation operation, all the transistors are turned off.
At this time, a closed loop is not formed and the energy stored in the winding flows backward as a return current to the DC power source E through the path shown by the solid line and the arrow.

In order to prevent this return current, for example, the improvement shown in Japanese Patent Laid-Open No. 63-234893 has been made. This limits the timing of switching by commutation operation and prevents all semiconductor switches from turning off by switching only when the semiconductor switch of the other arm is on by PWM control, and the return current is reduced. It was designed to eliminate.

[0008]

However, the conventional structure as described above has the following problems.

In the conventional method, the influence of the return current is eliminated, but the deviation of commutation may become very large depending on the chopping frequency of PWM control and the rotation speed of the DC motor.
The current increases and efficiency drops, and in the worst case, step-out occurs and the DC motor stops.

For example, a DC motor rotor has 4 poles and 6
When rotating at 000 r / min and the chopping frequency of PWM control is 2 kHz, on / off control is performed 3.3 times (2 kHz / 200 Hz / 3) on average in the commutation range to each phase. In this case, if the switching is performed at the moment when it is turned off, a maximum phase delay of about 30 degrees will occur. Due to the influence of this phase delay, the above problems occur.

The present invention solves the above-mentioned conventional problems, and does not cause characteristic deterioration such as current increase and efficiency reduction.
Moreover, it is an object of the present invention to provide an operation control device for a DC motor that can effectively prevent a return current.

[0012]

In order to achieve this object, a DC motor operation control apparatus according to the present invention uses a semiconductor switching of an inverter circuit based on the output of a position detection circuit for detecting the position of the rotor of the DC motor. A commutation circuit that determines the operation of the element, a chopping signal generation circuit that generates a signal for performing chopping to make the rotation speed of the DC motor variable, a first output of the commutation circuit, and a chopping signal generation circuit. A first drive circuit for synthesizing the output of the inverter circuit and turning on / off the semiconductor switch on one arm of the inverter circuit, and an off delay circuit for delaying a signal for turning on / off the second output of the commutation circuit for a certain period of time, It has a configuration of a second drive circuit for turning on / off the semiconductor switch of the other arm of the inverter circuit by the output of the off delay circuit.

[0013]

With this configuration, the operation in which the semiconductor switch on the other arm is turned off is delayed by the off delay circuit for a certain period of time, and the other semiconductor switches are turned on during that time, whereby all the semiconductor switches are turned off. To avoid the return current. At this time, two semiconductor switches are turned on at the same time for a fixed time, but the characteristics are not affected because the time is short. As described above, according to the present invention, the reflux current can be prevented without affecting the characteristics.

[0014]

(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 a first embodiment of the present invention.

In FIG. 1, reference numeral 1 is an AC power source. Reference numeral 2 is a rectifier circuit that converts the AC voltage of the AC power supply 1 into a DC voltage. The diodes 3a to 3d are bridge-connected, and the smoothing capacitor 4 is connected to the output thereof.

Reference numeral 5 denotes an inverter circuit in which semiconductor switches (transistors in this embodiment) 6a to 6f are connected in a three-phase bridge, and each transistor is connected in parallel.
The diodes 7a to 7f are connected in the reverse direction.

Reference numeral 8 is a DC motor, and an inverter circuit 5
Driven by the output of. Reference numeral 9 denotes a position detection circuit for detecting the rotational position of a rotor (not shown) of the DC motor 8, and in this embodiment, the position is detected from the counter electromotive voltage of the DC motor.

Reference numeral 10 is a commutation circuit for producing a signal for commutating the semiconductor switches 6a to 6f of the inverter circuit 5 from the output of the position detection circuit 9. Reference numeral 11 denotes a chopping signal generation circuit that generates a signal for performing PWM control for varying the rotation speed of the DC motor 8, and creates a waveform having a constant frequency and different on / off ratios.

Among the outputs of the commutation circuit 12, a signal 12 commutates the semiconductor switches 6d to 6f of the lower arm (first outputs Sx, Sy, Sz) and an output Sc of the chopping signal generation circuit 11. Semiconductor switch 6 under the AND condition of
It is a first drive circuit that operates d to 6f.

The output 13 of the commutation circuit 10 delays a signal at the time of turning off signals (second outputs Su, Sv, Sw) commutating the semiconductor switches 6a to 6c of the upper arm for a predetermined time. It is an off delay circuit. Reference numeral 14 is a second drive circuit that operates the semiconductor switches 6a to 6c with the output of the off delay circuit 13.

The operation of the operation control device for the DC motor configured as described above will be described with reference to FIGS. 2 and 3.

FIG. 2 is a timing chart of the main part of the first embodiment of the present invention. The semiconductor switches 6a to 6f are turned on / off by the outputs S1, S2, S3 of the position detection circuit 9 and the output Sc of the chopping signal generation circuit 11. The logical formula is as follows.

Su = (S1). (/ S2) Sv = (S2). (/ S3) Sw = (S3). (/ S1) Sx = (/ S1). (S2). (Sc) Sy = ( /S2).(S3).(Sc) Sz = (/ S3). (S1). (Sc) The off timing of each signal Su, Sv, Sw is delayed by a certain time (td), and the semiconductor switches 6a to 6c. To control. The signals Sx, Sy, Sz directly control the semiconductor switches 6d to 6f.

As shown in FIG. 2, since the upper arm semiconductor switch is delayed by a certain time when it is turned off, two of the three semiconductor switches are always on during the period of time td. This section can prevent all semiconductor switches from being turned off, and can prevent a return current.

Next, this operation will be described in more detail. FIG. 3 is a schematic diagram of the operation of the operation control device for the DC motor according to the first embodiment of the present invention.

In FIG. 3 (a), the semiconductor switches 6a and 6f are turned on, and current is supplied from the DC power source E through the route shown by the solid line and the arrow. Next, when 6f is turned off by PWM control in FIG. 3 (b), the closed loop as shown by the solid line is formed by the action of the diode in parallel with 6c, and the current continues to flow.

Next, in FIG. 3C, 6b is turned on by the commutation operation, but 6a is still turned on by the delay operation. At this time, the current shown by the solid line flows. Next, FIG. 3 (d)
Then, the delay operation ends and 6a is turned off. At this time, 6b is already turned on, and a current flows in a closed loop as shown by the solid line. In FIG. 3 (e), 6f is turned on again,
Return to the original state.

As is apparent from this operation, in the present invention, all the semiconductor switches are never turned off, and the closed loop is always formed, so that no return current is generated.

As described above, in this embodiment, based on the output of the position detection circuit 9 for detecting the position of the rotor of the DC motor 8, the semiconductor switching elements 6a to 6a of the inverter circuit 5
A commutation circuit 10 that determines the operation of 6f, a chopping signal generation circuit 11 that generates a signal for performing chopping to make the rotation speed of the DC motor 8 variable, and a first output Sx of the commutation circuit 10. , Sy, Sz and the output Sc of the chopping signal generation circuit 11 are combined to form the inverter circuit 5
Drive circuit 12 for turning on / off the semiconductor switches 6d to 6f on one side of the arm and an off delay circuit for delaying a signal for turning off the second outputs Su, Sv, Sw of the commutation circuit 10 for a certain period of time. 13 and an off delay circuit 13
By providing the second drive circuit 14 for turning on / off the semiconductor switches 6a to 6c on the other arm of the inverter circuit 5 by the output of the above, the state in which all the semiconductor switches are turned off is prevented and the current flows back to the smoothing capacitor 4. The return current can be prevented, the smoothing capacitor 4 can be downsized, and the reliability is improved. Also, since the timing of turning on is not shifted at all, it does not affect the characteristics of the DC motor at all.

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

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

In FIG. 4, 1 is an AC power source, 2 is a rectifier circuit, 3a to 3d are diodes, 4 is a smoothing capacitor, 7
a to 7f are diodes, 8 is a DC motor, 9 is a position detection circuit, 10 is a commutation circuit, 11 is a chopping signal generation circuit, and 12 is a first drive circuit. The above is the same as the configuration in FIG.

Reference numeral 20 denotes an inverter circuit, which is different from FIG. 1 in that low-speed semiconductor switches (transistors in the embodiment) are used for the upper arm semiconductor switches 21a to 21c, and high-speed semiconductor switches (transistors are used in the lower arm). In the embodiment, a MOSFET) is used.

Further, 22 is a third drive circuit, which is different from FIG. 1 and operates the second output of the commutation circuit 10 without OFF delay.

FIG. 5 is a detailed circuit diagram of the third drive circuit, showing the third drive circuit of the semiconductor switch 21a.

In FIG. 5, reference numeral 23 designates a transistor, and the collector and base of the semiconductor switch 21a are respectively emitter and emitter.
The collector is connected. Reference numeral 24 is a resistor which is attached between the emitter and base of the transistor 23. 25
Is a resistor, one end of which is connected to the base of the transistor 23 and the other end of which is connected to the collector of the transistor 26. The semiconductor switch 21a is ON / OFF controlled by a signal input to the base of the transistor 26.

A characteristic feature here is that in a general drive circuit such as this, the potential of the base is pulled to the negative side when the transistor is turned off in order to aim at high-speed operation of the transistor, but this is not done here. As will be described later, this is intended to positively use the storage time of the switching characteristic of the characteristics of the transistor.

Other upper arm semiconductor switches 21b, 2
1c also has a similar circuit.

The operation of the DC motor operation controller constructed as described above will be described below.

The commutation circuit 10 is driven by the output of the position detection circuit 9.
Generates commutation signals Su, Sv, Sw to the low speed semiconductor switches 21a to 21c of the upper arm. At the same time, the commutation signal S to the high speed semiconductor switches 21d to 21f of the lower arm
Generate x, Sy, and Sz.

In the first drive circuit 12, the output Sc of the chopping signal generating circuit 11 and the first outputs Sx, Sy, Sz of the commutation circuit are combined in the same manner as described in the first embodiment to form a high speed semiconductor. Switch 21d-21f on /
Turn off.

The third drive circuit 22 outputs the second outputs Su, Sv, Sw of the commutation circuit 10 as they are, and turns on / off the low-speed semiconductor switches 21a-21c.

Next, a more detailed description will be given with reference to FIG. FIG. 6 is a timing chart in the second embodiment.

Of the output of the commutation circuit 10, Sv turns on at the timing when Su turns off. However, in the actual operation of the semiconductor switch, the low speed semiconductor switch 21b corresponding to Sv is immediately turned on, but the low speed semiconductor switch 21a corresponding to Su is turned off after a delay of a fixed time (tstg).

This is because in the third drive circuit 22,
This is because the base is not pulled to the negative side as described above, and the characteristic of not turning off until the charge accumulated in the base of the low-speed semiconductor switch 21a is discharged is positively utilized.

By doing so, as described in the first embodiment, it is possible to avoid the state where all the semiconductor switches are turned off, and it is possible to prevent the return current flowing back to the smoothing capacitor 4.

As described above, according to the present invention, the six semiconductor switches 21a to 21f and the diodes 7a to 7f are bridge-connected and the one arm operates at high speed and the other arms operate at low speed and the other arm operates at low speed. The inverter circuit 20 using the low-speed semiconductor switches 21a to 21c, the commutation circuit 10 that determines the operation of the semiconductor switch of the inverter circuit 20 based on the output of the position detection circuit 9, and the rotation speed of the DC motor 8 are made variable. Chopping signal generation circuit 11 for generating a signal for performing chopping, and first outputs Sx, S of the commutation circuit 10.
The first drive circuit 12 that turns on / off the high-speed semiconductor switches 21d to 21f of one side arm of the inverter circuit 20 by the combined signal of y and Sz and the output Sc of the chopping signal generation circuit 11, and the second drive circuit of the commutation circuit 10. Output S
By providing the third drive circuit 22 which turns on / off the low speed semiconductor switches 21a to 21c of the other arm of the inverter circuit 20 by u, Sv, and Sw, the characteristics of the semiconductor switch are effectively utilized with a very easy configuration, The return current can be prevented, and the smoothing capacitor 4 can be downsized and its reliability can be improved.

Further, in the second embodiment, the circuit itself can be miniaturized and the cost can be reduced because the configuration is very easy. Further, since the lower arm uses the high-speed semiconductor switch, the chopping frequency can be increased, and by setting it to, for example, 20 kHz, it is possible to remove an unpleasant sound generated by the human during the chopping. At this time, the upper arm may remain the low-speed semiconductor switch. That is, the noise can be reduced without increasing the cost.

[0050]

As described above, according to the present invention, a commutation circuit that determines the operation of the semiconductor switching element of the inverter circuit based on the output of the position detection circuit that detects the position of the rotor of the DC motor, and the DC motor. A chopping signal generating circuit that generates a signal for performing chopping to make the rotation speed variable, a first output of the commutation circuit and an output of the chopping signal generating circuit, and a semiconductor switch of one side arm of the inverter circuit. Drive circuit for turning on / off the switch, an off delay circuit for delaying a signal for turning off the second output of the commutation circuit for a certain time, and a semiconductor switch on the other arm of the inverter circuit by the output of the off delay circuit By providing a second drive circuit for turning on / off the switch, it is possible to prevent the semiconductor switch on the other arm from being turned off by the off delay circuit. Is the time delay, is obtained as By such other semiconductor switch is turned on during, and avoid a situation in which all of the semiconductor switches is turned off, to prevent the return current. At this time, two semiconductor switches are turned on at the same time for a fixed time, but the characteristics are not affected because the time is short. As described above, according to the present invention, it is possible to prevent the return current without affecting the characteristics, so that not only the smoothing capacitor can be downsized, but also the reliability can be improved. The operation control device can be realized.

In another configuration, an inverter circuit using a high-speed semiconductor switch that operates at high speed in one arm and a low-speed semiconductor switch that operates at low speed in the other arm, in which a plurality of semiconductor switches and diodes are bridge-connected A first drive circuit for turning on / off a high speed semiconductor switch on one arm of the inverter circuit by a first output of the commutation circuit, and a low speed semiconductor switch for the other arm of the inverter circuit by a second output of the commutation circuit. By providing the third drive circuit for turning on / off, it is possible to realize the operation control device of the DC motor that can be downsized and reduced in cost and can prevent the return current.

[Brief description of 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. 2 is a timing chart of the main part of the first embodiment of the present invention.

FIG. 3 is a schematic diagram of the operation of the operation control device for the DC motor according to the first embodiment of the present invention. (A) is a schematic diagram when 6a and 6f of the semiconductor switches are turned on. (B) is 6f by PWM control. (C) is a schematic diagram when 6b is turned on by commutation operation (d) is a schematic diagram when 6a is turned off after the delay operation is completed (e) is 6f Schematic when is turned on again

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 detailed circuit diagram of a third drive circuit 22.

FIG. 6 is a timing chart in the second embodiment.

FIG. 7 is a schematic diagram of an operation of a conventional DC motor operation control device. FIG. 7A is a schematic diagram when semiconductor switches 6a and 6f are turned on. FIG. 7B is a schematic diagram when 6f is turned off by PWM control. Schematic diagram when 6a is turned off by commutation operation in (c)

[Explanation of symbols]

 2 Rectifier circuit 5 Inverter circuit 6a to 6f Semiconductor switch 8 DC motor 9 Position detection circuit 10 Commutation circuit 11 Chopping signal generation circuit 12 First drive circuit 13 Off delay circuit 14 Second drive circuit 20 Inverter circuit 21a to 21c Low speed semiconductor switch 21d-21f High-speed semiconductor switch 22 Third drive circuit

Claims (2)

[Claims] 1. A rectifier circuit for converting an AC input into a direct current, 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 rotor position of the DC motor is detected. Position detection circuit, a commutation circuit that determines the operation of the semiconductor switching element of the inverter circuit based on the output of the position detection circuit, and a signal for performing chopping for varying the rotation speed of the DC motor. And a first drive circuit for synthesizing the first output of the commutation circuit and the output of the chopping signal generation circuit to turn on / off the semiconductor switch of one arm of the inverter circuit, An off delay circuit for delaying a signal for turning off the second output of the commutation circuit for a predetermined time; Operation control device for a DC motor and a second drive circuit for turning on / off the semiconductor switches of the other arm of the inverter circuit by the output of the extension circuit. 2. A rectifier circuit for converting AC input into DC, a plurality of semiconductor switches and diodes are bridge-connected, and a high-speed semiconductor switch that operates at high speed on one arm and a low-speed semiconductor switch that operates at low speed on the other arm. The inverter circuit used, the DC motor operated by the inverter circuit, the 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 is determined based on the output of the position detection circuit. Commutation circuit, a chopping signal generation circuit that generates a signal for performing chopping for varying the rotation speed of the DC motor, a first output of the commutation circuit, and an output of the chopping signal generation circuit. And a first dry for turning on / off a high-speed semiconductor switch on one side of the inverter circuit. Circuit and operation control apparatus of a DC motor and a third drive circuit for turning on / off the second low-speed semiconductor switches of the other arm of the inverter circuit by the output of the commutation circuit.