JP3898254B2 - Motor control device and air conditioner using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device that combines a converter circuit that rectifies an AC power supply voltage into a desired DC voltage and an inverter circuit that converts a DC voltage output from the converter circuit into an AC voltage and energizes the motor. The present invention also relates to an air conditioner using a motor controlled by the motor control device as a power source.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 6-105563 discloses a motor control device that controls the operation of a motor by combining a motor drive circuit with a power supply circuit having a rectifier circuit that rectifies an AC power supply voltage and converts it into a DC voltage. . This device is equipped with a power factor improvement type converter circuit using a step-up chopper circuit that controls the harmonic component of the power supply current and controls the DC voltage, and an inverter circuit that drives the motor. The motor speed is controlled by PWM (Pulse Width Modulation) control using an inverter circuit, and the inverter circuit's current flow rate is controlled to 100% when the load is high. (Pulse Amplitude Modulation) control controls the speed of the motor by controlling the DC voltage.
[0003]
[Problems to be solved by the invention]
In the conventional system, two types of control, PWM control by an inverter circuit and PAM control by a converter circuit, are separately performed in order to realize motor speed control. For this reason, the control circuit (microcomputer) needs to perform at least two different calculations from the speed deviation, and requires two output ports for outputting control signals. Therefore, only one output port is used. It could not be implemented with a control circuit that could not be performed or a control circuit with a slow operation speed.
[0004]
One object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and to stably control the inverter circuit and the converter circuit by the control signal output from one PWM output port, and to control the motor smoothly. To provide an apparatus.
[0005]
Another object of the present invention is to provide an air conditioner using a motor that is operated and controlled by a motor control device configured using an inexpensive control circuit (such as a microcomputer or a hybrid IC) having a small number of output ports.
[0006]
[Means for Solving the Problems]
The above object is to convert a DC voltage received from the converter circuit into an AC voltage by converting a DC circuit received from the converter circuit having a rectifier circuit that converts an AC power supply voltage into a DC voltage and a chopper circuit that controls the magnitude of the DC voltage. An inverter circuit that outputs to a motor, a converter control circuit that controls a switching operation of the chopper circuit, an inverter control circuit that controls a switching operation of the inverter circuit and drives a motor, the converter control circuit, and the inverter control circuit And a control circuit that generates a control signal to be controlled. The control circuit includes a single output port that outputs a control signal for controlling the converter control circuit and a control signal for controlling the inverter control circuit. And the one output port is connected to the converter control circuit and an inverter. A switching circuit for distributing control signal output from the selectively coupled to the output port to the motor control circuit, the set of the signal level defined circuits was interposed between the output port and the switching circuit only, the switching circuit When the duty ratio of the inverter circuit calculated by the control circuit is less than 100%, the control circuit is switched to PWM control of the inverter circuit, and the duty ratio of the inverter circuit calculated by the control circuit is 100. in the case of more than% switches the control circuit to PAM control of the converter circuit, while the duty ratio to 100%, so as to control the output voltage of the converter circuit, is achieved.
[0007]
Further, by providing an integration circuit between the switching circuit and the converter control circuit, fluctuations in the control signal at the time of switching are reduced, thereby realizing smooth switching control.
[0008]
In addition, an air conditioner that is inexpensive and excellent in controllability is realized by using a compressor or a blower that uses a motor controlled by such a motor control device as a power source.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a motor control device according to the present invention will be described with reference to FIGS.
[0010]
FIG. 1 shows the configuration of a motor control device, which is a converter circuit 2 that controls the waveform shaping of an input current from an AC power source 1 and the magnitude of a DC voltage using a rectifier circuit 2a, a boost chopper circuit 2b, and a smoothing capacitor 2c. And an inverter circuit 3 that converts the DC voltage into an AC voltage having a desired pulse width and supplies it to the brushless DC motor 4, and a control circuit that performs control processing of the brushless DC motor 4 in accordance with a speed command (one-chip microcomputer or Hybrid IC) 5, a switching circuit 6 for selectively transmitting a control signal in the form of a PWM signal output from the PWM output port 505 of the control circuit 5 to the converter control circuit 7 and the inverter control circuit 8, and the control The level of the control signal in the form of the PWM signal output from the PWM output port 505 of the circuit 5 is transmitted to the transmission system and the peripheral circuit. A signal level defining circuit 9 that regulates to a prescribed level so as not to be affected by fluctuations, and is connected to a subsequent stage of the switching circuit 6 to convert the control signal (digital signal) into a control signal in the form of an analog signal, and this analog signal An integrating circuit 10 is provided for suppressing the rapid fluctuation of the control signal in the form and supplying it to the converter control circuit 7.
[0011]
The converter circuit 2 rectifies an AC voltage supplied from the AC power source 1 by a rectifier circuit 2a and boosts the voltage by a boost chopper circuit 2b composed of a reactor, a diode, and a transistor. The boosting chopper circuit 2b is configured to boost the DC voltage by forcing the input current to flow to the DC output side by turning off the transistor after passing current through the reactor by turning on the transistor to store energy. Operate. The smoothing capacitor 2c smoothes the voltage supplied from the boost chopper circuit 2b to obtain a stable DC voltage. The step-up chopper circuit 2b has a function of improving the power factor of input power by controlling the ON / OFF time ratio of the transistor in a sine wave shape and controlling the DC voltage to an arbitrary magnitude.
[0012]
The inverter circuit 3 for energizing the brushless DC motor 4 performs pulse width modulation on a DC voltage of an arbitrary magnitude supplied from the smoothing capacitor 2c of the converter circuit 2, and converts the AC voltage having an arbitrary amplitude and frequency into The brushless DC motor 4 is supplied to control the operation of the motor 4.
[0013]
The control circuit 5 outputs a converter start / stop signal to the converter control circuit 7 according to conditions, and controls the operation / stop of the converter circuit 2. Further, the PWM output port 505 switches and outputs an inverter conduction ratio signal to be supplied to the inverter control circuit 8 and a corrected DC voltage control signal to be supplied to the converter control circuit 7 according to operating conditions. The converter control circuit 7 and the inverter control circuit 8 are controlled so as to control the speed of the brushless DC motor 4 so that the rotation speed matches the speed command value.
[0014]
Details of the control circuit 5 will be described with reference to FIG.
[0015]
FIG. 2 shows functional blocks of the control circuit 5. The control circuit 5 is constituted by a one-chip microcomputer, and calculates a speed deviation based on a speed detection unit 501 that detects the rotational position and speed of the rotor of the brushless DC motor 4 and a rotational speed detection signal and a speed command value. And a speed control unit 502 that outputs a speed deviation signal and calculates a conduction rate of the inverter circuit 3 and outputs an inverter conduction rate signal, and an inverter conduction rate signal output from the speed control unit 502. The DC voltage command value is calculated, and the DC voltage control unit 503 further calculates a corrected DC voltage from the DC voltage and the DC voltage command value. The inverter is based on the speed deviation signal, the inverter duty ratio signal, and the corrected DC voltage value. A switching determination unit 504 for determining which control signal of the duty ratio signal or the corrected DC voltage value is output from the PWM output port 505; According to the judgment result of the example decision unit 504, and a switching unit 506 to output a control signal to one of the inverter duty ratio signal and said corrected DC voltage signal from the PWM output port 505.
[0016]
The speed detector 501 calculates the magnetic pole position of the rotor based on the induced voltage of the brushless DC motor 4 and generates a position detection signal to be supplied to the inverter control circuit 8. Further, speed calculation is performed based on the calculated position detection signal, and a speed detection signal to be supplied to the speed control unit 502 and the switching determination unit 504 is generated.
[0017]
The speed control unit 502 calculates a speed deviation based on the speed detection signal from the speed detection unit 501 and an external speed command, and calculates an inverter duty ratio command value so that the speed deviation becomes zero. A speed deviation signal supplied to the switching determination unit 504 and an inverter conduction rate signal supplied to the DC voltage control unit 503 and the inverter control circuit 8 are generated.
[0018]
The DC voltage control unit 503 receives the inverter conduction rate signal supplied from the speed control unit 502 and the DC voltage value signal obtained by detecting the voltage of the smoothing capacitor 2c in the converter circuit 2, and the inverter conduction The DC voltage command value is increased / decreased by a predetermined width from the value of the rate signal, a corrected DC voltage value based on the DC voltage value and the DC voltage command value is calculated and supplied to the switching determination unit 504 and the converter control circuit 7 A voltage value signal is generated.
[0019]
The switching determination unit 504 determines which of the inverter duty ratio signal and the corrected DC voltage value signal is output from the PWM output port 505 based on the speed deviation, the inverter duty ratio, and the corrected DC voltage value. When the duty ratio is less than 100%, the inverter duty ratio signal from the speed controller 502 is output from the PWM output port 505, and when the duty ratio is 100% or more, the corrected DC voltage value signal from the DC voltage controller 503 is output. The switching unit 506 is controlled to output from the PWM output port 505.
[0020]
The switching circuit 6 switches so that the control signal output from the PWM output port 505 of the control circuit 5 is distributed to the inverter control circuit 8 and the converter control circuit 7 according to the determination result in the switching determination unit 504.
[0021]
The switching process of the switching circuit 6 will be described. First, the case where the inverter conduction ratio calculated by the control circuit 5 is less than 100% will be described. When the inverter flow rate is less than 100%, the control circuit 5 outputs the inverter flow rate signal as a control signal from the PWM output port 505 and supplies it to the switching circuit 6 through the signal level defining circuit 9. Then, the switching circuit 6 outputs the inverter conduction ratio signal to the inverter control circuit 8 and switches the DC voltage value of the smoothing capacitor 2 c in the converter circuit 2 to the converter control circuit 7.
[0022]
When the inverter conduction ratio is 100% or more, the control circuit 5 outputs the corrected DC voltage value signal Ed ′ from the PWM output port 505 and supplies it to the switching circuit 6 through the signal level defining circuit 9. Then, the switching circuit 6 switches to supply the corrected DC voltage value signal Ed ′ to the converter control circuit 7 through the integration circuit 10 and outputs a maximum conduction ratio (100%) signal to the inverter control circuit 8. Switch to do. As a result, the inverter circuit 3 keeps the conduction rate at 100%.
[0023]
A control signal in the form of a PWM signal distributed to the converter control circuit 7 side is input from the switching circuit 6 to the integration circuit 10. The integration circuit 10 converts a control signal (digital signal) in the form of a PWM signal into a control signal in the form of an analog signal and suppresses a sudden change in the control signal supplied to the converter control circuit 7 immediately after switching.
[0024]
The converter control circuit 7 controls the operation of the converter circuit 2 according to the converter start / stop signal from the control circuit 5, and controls the control signal (command value) supplied from the switching circuit 6 via the integration circuit 10. Based on this, the transistor in the converter circuit 2 is driven to control the input current of the converter circuit 2 in a sine wave shape, and the DC voltage to be output is controlled along with the improvement of the power factor of the input from the AC power source 1. The converter start / stop signal is generated by calculation based on the detected values of voltage and current in the control circuit 5, and when the input power is a predetermined value (for example, 350 w) or more, the converter start signal is output to control the converter. If it is less than a predetermined value (for example, 300 w), a converter stop signal is output to stop converter control. By providing hysteresis in this way, the converter operation is stabilized.
[0025]
The inverter control circuit 8 generates a drive signal based on the position detection signal from the speed detection unit 501 and the inverter conduction ratio signal distributed from the switching circuit 6, and controls the transistor of the inverter circuit 3 to perform brushless DC. The speed control of the motor 4 is performed.
[0026]
The signal level defining circuit 9 generates defined high level and low level control signals in synchronization with a control signal in the form of a PWM signal output from the PWM output port 505. The signal level defining circuit 9 shifts to the maximum DC voltage set in the control circuit 5 when the signal level used for calculation in the control circuit 5 and the signal level from the PWM output port 505 are shifted during DC voltage control. Therefore, this is a signal stabilization circuit for satisfactorily controlling the DC voltage without being influenced by the peripheral circuit.
[0027]
FIG. 3 illustrates a circuit configuration of the signal level defining circuit 9. 3A, an analog switch is used to generate a two-level control signal by a switching operation synchronized with a control signal in the form of a PWM signal output from the PWM output port 505 of the control circuit 5. FIG. This method can regulate the supplied voltage level even when the voltage level of the PWM signal output from the PWM output port 505 is shifted, and generates an inverted signal by inverting the high level and the low level of the control signal. Also has the advantage of being easy.
[0028]
FIG. 3B shows an example in which an inexpensive circuit element including only a resistor is used without using an expensive circuit element such as an analog switch.
[0029]
In addition, the signal level defining circuit 9 may be a circuit that regulates the signal level used for calculation inside the microcomputer (for example, high level voltage: 5 V, low level voltage: 0 V).
[0030]
As shown in FIG. 4, the integration circuit 10 is a typical integration circuit composed of a resistor and a capacitor. By providing the integration circuit 10 at the subsequent stage of the switching circuit 6, the PWM signal ( (Digital signal) is converted into an analog signal and functions to suppress a sudden change in the signal level supplied to the converter control circuit 7 when the switching circuit 6 is switched.
[0031]
5A shows a part of the circuit configuration and the DC voltage waveform when the integration circuit 10 is provided in the front stage of the switching circuit 6, and FIG. 5B shows a part of the circuit configuration when the integration circuit 10 is provided in the rear stage. A DC voltage waveform is shown. In the circuit configuration of FIG. 5A, the DC voltage waveform varies greatly immediately after switching. However, as shown in FIG. 5B, when the integrating circuit 10 is provided in the subsequent stage of the switching circuit 6, the electrostatic capacity inside the circuit suppresses a rapid change in the control signal before and after switching. The fluctuation of the DC voltage immediately after switching becomes small, and switching between PWM control and PAM control can be performed smoothly.
[0032]
FIG. 6 is a flowchart showing an example of the speed control process executed in the control circuit 5 of FIG. 2 in the PAM control, and shows the calculation procedure of the DC voltage command value Ed * and the corrected DC voltage value Ed ′. Yes. In process 511, the control circuit 5 calculates a speed deviation from a speed command and a speed detection value given from the outside. In process 512, the control circuit 5 calculates an inverter duty ratio so that the speed deviation becomes 0, and process 513. Then, it is determined whether or not the inverter conduction ratio is 100% or more. If 100% or more, the process proceeds to step 514 to determine whether or not the motor 4 is being accelerated. If the motor 4 is being accelerated, the direct current voltage command value Ed * is increased by 1 V in step 516 and the process proceeds to step 519 to proceed to the corrected DC voltage value Ed. 'Calculate'. When not accelerating, the process proceeds to the process 519 through the process 517, and the correction DC voltage value Ed ′ is calculated using the DC voltage command value Ed * as it is. Here, accelerating means that the deviation is positive, and decelerating means that the deviation is negative.
[0033]
On the other hand, when the calculated value of the inverter duty ratio is less than 100% in the PAM control, it is determined whether or not the motor 4 is decelerating in processing 515, and when it is decelerating, the DC voltage command value Ed * is abbreviated in processing 518. Decrease by 1V and proceed to processing 519. If the vehicle is not decelerating, correction processing is performed in processing 519 using the DC voltage command value Ed * as it is. 1V in the processings 516 and 518 is an example of a constant representing a calculation method. In reality, it is preferable to set this constant according to the speed deviation in order to improve control responsiveness.
[0034]
In process 519, a corrected DC voltage value Ed ′ is calculated from the DC voltage command value Ed * and the DC voltage value Ed. In process 520, the corrected DC voltage value Ed ′ is supplied to the converter control circuit 8 as a corrected DC voltage value signal. To output. 1.55 V in the process 519 is a constant used in this example, and is a reference voltage value set according to the control system.
[0035]
Here, the DC voltage value Ed is corrected. In the converter control circuit 7 used in this embodiment, the reference voltage Vr corresponding to the DC voltage command value is a fixed value, and the setting of the DC voltage is based on the detection resistance. Since the pressure ratio is changed, it is difficult to change the DC voltage according to the DC voltage command value created according to the rotation speed of the motor 4. For this reason, the control circuit 5 corrects the DC voltage value in accordance with the DC voltage command value and then outputs it to the converter control circuit 7. This correction is set so that a value equal to the reference voltage value Vr (1.55 V) inside the converter control circuit 7 is output when the DC voltage value matches the DC voltage command value. Thereby, it becomes possible to control the DC voltage corresponding to the DC voltage command value.
[0036]
In this way, the DC voltage control is performed by a method in which the DC voltage command value Ed * is increased or decreased by a predetermined width in accordance with the inverter duty ratio. There is no need to perform the operation, the arithmetic processing steps can be reduced, and speed control can be easily performed. The DC voltage command value Ed * has an upper limit value and a lower limit value, the maximum DC voltage command value is set to 350V, the minimum DC voltage command value is set to 150V, and PWM control is performed below 150V.
[0037]
The motor control operation will be described with reference to FIG. FIG. 7 is a graph in which the horizontal axis represents the motor rotation speed (rotational speed) and the vertical axis represents the DC voltage output from the converter circuit 2 and the conduction ratio of the inverter circuit 3, and the motor rotation when the load is constant. It is the figure which showed the DC voltage with respect to a number, and a conduction rate.
[0038]
In the low rotation speed region such as when the motor 4 is started, PWM control is performed with the inverter conduction rate calculated by the speed control unit 502, and the minimum voltage command value (DC voltage command value 150V) is output to the converter control circuit 7. is doing. When the input power becomes 350 W or more, the control circuit 5 outputs a converter operation start signal to the converter control circuit 7 to operate the converter circuit 2. When the rotational speed of the motor 4 is increased, the voltage is low in the state of the DC voltage controlled to the minimum voltage command value, so that the conduction rate of the inverter circuit 3 reaches 100% and the rotational speed of the motor 4 is increased. Can no longer be raised. For this purpose, switching to PAM control is performed using the switching circuit 6. The switching circuit 6 is controlled by the switching signal from the control circuit 5 to supply the corrected DC voltage value Ed ′ (control signal) to the converter control circuit 7 and to the inverter control circuit 8 with a conduction rate of 100%. Switch to supply command signal. Then, as described above, the control circuit 5 determines whether the vehicle is accelerating or decelerating based on the speed deviation, is accelerating, and the inverter duty ratio in the control circuit 5 is 100% or more. In this case, the DC voltage command value Ed * is increased by 1 V to calculate the corrected DC voltage value Ed ′ and output from the PWM output port 505 as a control signal. After switching to the PAM control in this way, the speed control of the motor 4 is performed so as to obtain the command value according to the flowchart of FIG. 6 as described above. In addition, in order to protect the motor control device, in this embodiment, an upper limit value (350 V) of the DC voltage is set. This upper limit value is preferably set according to the configuration of the motor control device. Thus, by changing the DC voltage in accordance with the increase in the rotational speed, the speed control of the motor 4 is performed while keeping the conduction rate of the inverter circuit 3 at 100%.
[0039]
Next, a case where the motor 4 is decelerated during PAM control will be described. When the rotational speed of the motor 4 in the high speed rotation state is lowered by the deceleration command by the PAM control, the inverter flow rate calculated by the control circuit 5 decreases and becomes less than 100%. Then, it is determined whether the vehicle is accelerating or decelerating from the speed deviation. If the vehicle is decelerating, the DC voltage command value Ed * is lowered by about 1 V to calculate the corrected DC voltage value Ed ′, The switching circuit 6 supplies a corrected DC voltage value Ed ′ that decreases approximately 1 V to the converter control circuit 7, and the converter circuit 2 decreases the DC voltage. In this way, the control process according to the flowchart of FIG. 6 is repeated until the DC voltage reaches 145 V (when hysteresis is set to 5 V). When the DC voltage reaches 145 V, the switching circuit 6 switches to supply the DC voltage lower limit value to the converter control circuit 7 and supplies the inverter conduction ratio signal to the inverter control circuit 8 to start PWM control. Further, when the input power becomes 300 W or less, the control circuit 5 supplies a converter stop signal to the converter control circuit 7 and stops the operation of the converter circuit 2. The switching voltage 150V is an example, and it is preferable to set a value suitable for the supplied AC power supply and to provide hysteresis for the switching voltage value.
[0040]
By performing the control process as described above, in the PAM control, the conduction rate of the inverter circuit 3 is maintained at 100%, and the output voltage of the converter circuit 2 is controlled to a DC voltage having a magnitude required by the motor 4. Can do.
[0041]
According to the control method described above, the DC voltage command value is calculated based on the inverter duty ratio calculated inside the control circuit 5, and the inverter duty ratio signal and the corrected DC voltage signal are respectively converted by the switching circuit 6 into the inverter. The control circuit 8 and the converter control circuit 7 can be switched and supplied. Therefore, it becomes possible to control the inverter circuit 3 and the converter circuit 2 by using one PWM output port 505 of the control circuit 5 to control the operation of the brushless DC motor 4. Further, by providing the signal level defining circuit 9 for defining the output level of the signal output in the form of the PWM signal from the PWM output port 505 of the control circuit 5 and the integrating circuit 10 at the subsequent stage of the switching circuit 6, The difference between the internally calculated value and the signal level supplied to the converter control circuit 7 is suppressed, and a sudden change in the signal supplied to the converter control circuit 7 can be suppressed when switching between PWM control and PAM control. Since the switching of the types of control can be performed smoothly, good motor speed control can be performed.
[0042]
By constructing an air conditioner using a compressor or blower powered by the brushless DC motor 4 that is energized and operated by such a motor control device, an air conditioner that is inexpensive and has excellent controllability is realized. can do.
[0043]
【The invention's effect】
According to the present invention, a control signal output from one output port of a control circuit such as an inexpensive one-chip microcomputer or hybrid IC with a small number of output ports is distributed to an inverter control circuit and a converter control circuit by a switching circuit, The converter circuit is controlled, a signal level defining circuit is provided in front of the switching circuit, and an integrating circuit is provided in the subsequent stage of the switching circuit, thereby smoothly switching the control signals for the two control systems and performing good motor speed control. Can make it possible.
[0044]
In addition, an air conditioner that is inexpensive and excellent in controllability can be realized by configuring an air conditioner using a compressor or a blower that uses a motor controlled by the motor control device as a power source.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a motor control device according to the present invention.
FIG. 2 is a functional block diagram of a control circuit in the motor control device according to the present invention shown in FIG. 1;
3 is a circuit configuration diagram of a signal level defining circuit in the motor control device according to the present invention shown in FIG. 1; FIG.
4 is a circuit configuration diagram of an integration circuit in the motor control device according to the present invention shown in FIG. 1; FIG.
FIG. 5 is an explanatory diagram for explaining the effect of an integrating circuit in the motor control device according to the present invention shown in FIG. 1;
6 is a flowchart of a speed control process performed by a control circuit in the motor control device according to the present invention shown in FIG. 1;
7 is an explanatory diagram of a motor control operation of the motor control device according to the present invention shown in FIG. 1; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter circuit 2a Rectifier circuit 2b Boost chopper circuit 2c Smoothing capacitor 3 Inverter circuit 4 Brushless DC motor 5 Control circuit (one-chip microcomputer)
6 switching circuit 7 converter control circuit 8 inverter control circuit 9 signal level defining circuit 10 integrating circuit 505 PWM output port

Claims (12)

A converter circuit including a rectifier circuit that converts an AC power supply voltage into a DC voltage and a chopper circuit that controls the magnitude of the DC voltage, and converts the DC voltage received from the converter circuit into an AC voltage and outputs the AC voltage to the motor An inverter circuit; a converter control circuit that controls a switching operation of the chopper circuit; an inverter control circuit that controls the switching operation of the inverter circuit to drive a motor; and a control signal that controls the converter control circuit and the inverter control circuit A motor control device including a control circuit for generating
The control circuit includes one output port that outputs a control signal for controlling the converter control circuit and a control signal for controlling the inverter control circuit,
The one output port is selectively connected to the converter control circuit, the inverter control circuit, a switching circuit for distributing a control signal output from the output port, and a signal level interposed between the output port and the switching circuit set and provisions circuits,
The switching circuit switches the control circuit to PWM control of the inverter circuit when the conduction rate of the inverter circuit calculated by the control circuit is less than 100%, and the switching circuit of the inverter circuit calculated by the control circuit is switched. When the flow rate is 100% or more, the control circuit is switched to PAM control of the converter circuit, and the output voltage of the converter circuit is controlled with the conduction rate kept at 100%. Control device.   2. The motor control device according to claim 1, wherein the output port is a port capable of outputting a pulse signal. The motor control device according to claim 1, further comprising a circuit that suppresses fluctuation of the control signal at the time of switching in the switching circuit . The motor control device according to claim 1, further comprising a circuit that suppresses fluctuation of the DC voltage at the time of switching in the switching circuit. 2. The motor control device according to claim 1, wherein a digital / analog converter is provided at a subsequent stage of the switching circuit . 2. The motor control device according to claim 1, wherein an integration circuit including a capacitor is provided in a subsequent stage of the control signal switching circuit . 2. The motor control device according to claim 1 , wherein the signal level defining circuit includes a switching element that outputs a predetermined voltage in response to a control signal output from an output port of the control circuit . 2. The motor control device according to claim 1, wherein the control circuit is a microcomputer that selectively outputs a control signal for the converter control circuit and a control signal for the inverter control circuit from one output port. 2. The motor control device according to claim 1, wherein the control circuit is a hybrid IC that selectively outputs a control signal for the converter control circuit and a control signal for the inverter control circuit from one output port. An air conditioner comprising a compressor having a power source as a motor whose operation is controlled by the motor control device according to claim 1. An air conditioner comprising a blower using a motor controlled by the motor control device according to claim 1 as a power source. The motor control circuit according to claim 1,
The control signal for controlling the converter control circuit is a digital signal, and a digital / analog converter for converting the digital signal into an analog signal and inputting the analog signal to the converter control circuit is provided in the preceding stage of the converter control circuit. A motor control device.

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