JP2004064903A - Controller for synchronous motor, and apparatus using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synchronous motor controller which detects the information about a motor without using a motor current sensor. <P>SOLUTION: This controller performs first AD conversion and second AD conversion at a fixed time interval by means of an AD converter synchronized with a PWM signal, and reproduces the output current of an inverter circuit, based on the AD-converted first DC current information and the second DC current information, thereby controlling a synchronous motor. At that time, it lowers PWM carrier frequency when the difference of phase voltage is small and the pulse interval is short. Furthermore, in case of pulse interval impossible of detection, it reproduces the output current of the inverter circuit using the motor current detected in the past, too. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device that controls the rotation speed of a permanent magnet synchronous motor to a desired rotation speed, and an air conditioner, a refrigerator, and a vacuum cleaner using the control device.
[0002]
[Prior art]
2. Description of the Related Art A permanent magnet synchronous motor having a permanent magnet rotor and a stator winding is widely used in air conditioners, refrigerators, washing machines, and the like because of its high efficiency. The drive control of the permanent magnet synchronous motor needs to be performed by closely relating the magnetic pole position of the rotor and the phase of the motor current. For the detection of the magnetic pole position of the rotor of a compressor motor such as an air conditioner, a position sensorless drive method of estimating the magnetic pole position of the rotor without using a rotor position detection sensor such as a Hall element and driving the motor is adopted. ing.
[0003]
Also, in order to operate the permanent magnet synchronous motor with high efficiency, a vector control theory is applied to optimize the phase relationship between the motor induced voltage and the motor current based on the position information, and a desired current phase is obtained. The voltage phase is controlled as described above.
[0004]
In Japanese Patent No. 271470, a current detection unit is provided between a forward converter unit and an inverse converter unit of an inverter device, and a signal of a logic circuit that generates a combined signal of terminal voltages of respective phases applied to a motor is provided. A control device that samples and holds and detects a motor current is disclosed.
[0005]
Japanese Patent Application Laid-Open No. 2001-145398 discloses that an instantaneous value of a torque component current and an excitation component current is obtained by detecting a motor current of one phase and using an estimated value of another phase, A method for determining an estimate of the phase of
[0006]
[Problems to be solved by the invention]
In the above-described prior art position sensorless driving method and vector control, motor current information is required, and a motor current sensor is used for that. However, since the motor current sensor is relatively expensive such as a current transformer (CT) using a Hall element, the motor control system also becomes expensive.
[0007]
The method of Japanese Patent No. 272470 has a disadvantage that a sample-and-hold signal is not generated until a signal of a logic circuit is generated. Further, in this method, although the currents of two phases among the three phases can be detected with a time difference, there is no consideration to minimize the detection time difference between the two phases as much as possible. Further, there is no description of a solution for a case where the signal width of the logic circuit becomes short and the sample and hold cannot be performed.
[0008]
In the method disclosed in Japanese Patent Application Laid-Open No. 2001-145398, when a motor current is detected between a forward converter and an inverse converter of an inverter device by using a current detection unit, the relationship between the detection possibility and an estimated value is determined. , And the relationship between the estimated value and the voltage phase is not shown.
[0009]
Further, in the above-described conventional technology, when the PWM frequency of the PWM inverter is lowered, noise of a component caused by the frequency is generated from the motor, so that a frequency of 16 kHz or more may be selected as an inaudible frequency. However, driving at a frequency higher than the audible band in this way increases the switching loss of the inverter and deteriorates the efficiency.
[0010]
[Means for Solving the Problems]
A synchronous motor control device according to the present invention includes an inverter circuit that converts a DC voltage into an AC voltage by a power semiconductor switching element to drive a synchronous motor, a control circuit that performs control processing according to a command speed, and a driver that drives the inverter circuit. And a DC current detector for detecting a DC current flowing through the inverter circuit, wherein the control circuit generates a signal for switching a power semiconductor element, and the detected DC in synchronization with the switching signal. An analog-to-digital conversion (hereinafter, abbreviated as “AD conversion”) analog-to-digital conversion (hereinafter referred to as “AD conversion”). The analog-to-digital conversion is performed a plurality of times at fixed time intervals in synchronization with the switching signal. The synchronous motor is controlled by reproducing the output current of the inverter based on the current information.
[0011]
The synchronous motor control device according to the present invention performs AD conversion on a phase in which no DC current flows, combines the result with an AD conversion result in a phase in which DC flows, and adjusts the offset included in the output of the DC current detection circuit. The voltage has been removed.
[0012]
The synchronous motor control device of the present invention changes the carrier frequency in order to widen the pulse width of the PWM signal to a detectable pulse width, or combines the detected carrier current with the motor current reproduced from the DC current information obtained in the past. Estimate the current output current of the inverter.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a motor control device using a permanent magnet synchronous motor according to the present invention will be described with reference to FIGS.
[0014]
(Example 1)
FIG. 1 is a block diagram of the synchronous motor control device of the present embodiment. In the synchronous motor control device shown in FIG. 1, the voltage of the DC power supply 1 is converted into an AC voltage subjected to pulse width modulation (PWM) and supplied to the U-phase, V-phase, and W-phase stator windings of the synchronous motor 3. An inverter circuit 2 for rotating the synchronous motor 3 in accordance with a speed command signal, a control circuit 4 for controlling the synchronous motor 3 according to a speed command signal, a driver 5 for driving the inverter circuit 2 in accordance with a signal from the control circuit 4, And a resistor 6 for detecting a DC current IDC flowing from the DC power supply 1 to the inverter circuit 2. The control circuit 4 is a one-chip microcomputer or a hybrid IC using the same. As shown in FIG. 1, the inverter circuit 2 is an inverter in which three sets of two series-connected semiconductor switching elements are connected between a positive terminal and a negative terminal of a DC power supply, respectively. Upper arm side is U ⁺ , V ⁺ , W ⁺ And the lower arm side of the negative terminal is U ⁻ , V ⁻ , W ⁻ It is. A power MOSFET or IGBT is used as a semiconductor switching element of the inverter circuit.
[0015]
In the control circuit 4, a DC current detection circuit is formed together with the resistor 6, and an amplifier 7 for amplifying a DC current detection voltage 6a generated in the resistor 6 and an output voltage 7a of the amplifier 7 are AD-activated. An A / D conversion unit 8 having an A / D conversion unit that samples and converts an analog value to a digital value according to the A / D conversion activation time 11a output from the time determination unit 11, and converts the A / D converted value 8a based on the conduction mode information 19a. , A selector 9 for separately outputting zero current information 9a and motor current information 9b, energization mode information 19a, an AD activation time interval Tw output from the AD activation interval setting device 12, and an AD conversion sampling time setting. A starting time determining unit 11 for determining an A / D conversion starting time 11a from an A / D sampling time 13a set by the unit 13; Based on the flow information 9a, the motor current information 9b, and the three-phase motor current estimation value 15a, the motor current reproduction unit 14 that reproduces the motor current and outputs the motor current reproduction value 14a, and the motor current reproduction value 14a are input. And a 3φ / dq coordinate conversion unit 16 for converting the current into a d-axis q-axis current 16a, and an average value by inputting the d-axis q-axis current 16a
A filter 21 for outputting the average 21a of the d-axis current and the q-axis current, a dq / 3φ inverse converter 15 for outputting a three-phase motor current estimated value 15a, a d-axis q-axis current 16a and a motor A motor that generates d-axis q-axis motor applied voltage information 17a to be applied to the motor based on the constant 20a, the command speed, the d-axis current command, and the q-axis current command so that the d-axis q-axis current 16a matches each command. An applied voltage generation unit 17, a coordinate inverse transformation / carrier period determination unit 18 that performs coordinate inverse conversion from the d-axis q-axis motor applied voltage information 17 a and outputs three-phase motor applied voltage information 18 a and carrier cycle data 18 b, Timer information 19b for generating a PWM signal from the phase motor applied voltage information 18a and the carrier cycle data 18b, the AD conversion start time 11a, and the necessary information for reproducing the motor current. A PWM signal generating timer information unit 19 for outputting the mode information 19a, and a PWM signal generator 22 for converting the PWM signal generating timer information 19b to the PWM signal 22a to the driver 5.
[0016]
FIG. 2 is an amplification characteristic diagram of the amplifier 7, and shows a relationship between the DC current IDC and the output voltage 7a of the amplifier 7. DC current IDC is IDC _max , 0, IDC _min , The output of each amplifier is VIDC _max , VIDC0, VIDC _min Is output. While the DC current IDC has a value in a positive / negative range, the AD converter 8 operates only with a positive power supply. Therefore, the amplifier 7 is an amplifier with an offset voltage as shown in FIG. In FIG. 2, VIDC0 is an offset voltage, and is an output of the amplifier 7 when the DC current IDC is 0. Since this offset voltage fluctuates due to temperature and component variations, as shown in FIG. _max And VIDC _min Also fluctuate.
[0017]
For example, when the AD conversion unit 8 includes an AD conversion unit that operates with, for example, a 5V power supply, the amplifier 7 has a DC current of 0 A and a voltage that is half the power supply voltage.
Let 2.5V be the offset voltage. Then, by the method described later, the AD converter is operated even at the timing when the DC current does not flow, and the offset voltage is secured as the third DC current information.
[0018]
FIG. 3 schematically shows the motor applied voltage information 18a and the carrier signal. When a sinusoidal current is supplied to the synchronous motor 3, the output voltage of the inverter needs to be a sinusoidal voltage. For this purpose, as shown in FIG. 3, a carrier signal represented by a triangular wave and a signal wave V represented by a sine wave which is the motor applied voltage information 18a. _u , V _v , V _w At the crossing point, a switching ON / OFF signal, a so-called PWM signal 22a, is generated by the PWM signal generation unit 22, and the six semiconductor switching elements constituting the inverter circuit are switched according to this signal to the synchronous motor 3. Apply a sinusoidal voltage. As a result, the phase voltage applied to the synchronous motor 3 becomes a signal wave V indicated by a sine wave. _u , V _v , V _w Alternately, the phase which becomes maximum and the phase which becomes minimum alternately change every 120 °.
[0019]
FIG. 4 is an enlarged view of the sine wave signal and the carrier signal of FIG. 3 with respect to one cycle of the carrier signal, and shows a relationship between the PWM signal 22a and the DC current IDC. The waveform of the PWM signal 22a is determined for each voltage phase based on the carrier signal and the magnitude of the applied voltage information 18a for each phase. When the PWM signal 22a is Hi, the upper arm of the inverter circuit 2 conducts, and when it is Low, the lower arm conducts.
[0020]
In the PWM signal generation timer information section 19, the signal wave V which is the motor applied voltage information 18a shown in FIG. _u , V _v , V _w Are determined, four types of timer information 19b of time data representing the voltage of each phase and time data representing the carrier signal period are determined. The PWM signal generation unit 22 operates an up / down type timer in accordance with the timer information 19b to generate a signal that is turned on / off when the time data representing the voltage of each phase matches the timer value, and generates a PWM signal. Let it be signal 22a.
[0021]
FIG. 5 shows an energized state in each ON mode of the inverter circuit 2. Information appearing in the DC current IDC flowing through the resistor 6 changes in a time-sharing manner depending on the energization state of the inverter circuit 2. This will be described together with the relationship between the energization modes (1) to (4) shown in FIG.
[0022]
As shown in FIGS. 5 (a) and 4 (4), when the upper arms are all on and the lower arms are all off, or as shown in FIGS. 5 (b) and 4 (3), the upper arm is When all the lower arms are on and all the lower arms are on, no DC current IDC flows. Further, as shown in FIG. 5C and FIG. 4A, when two upper arms are on and one lower arm is on, the DC current IDC has the minimum voltage phase (referred to as k-phase). Motor current information appears. Further, as shown in FIG. 5D and FIG. 4B, when one upper arm is on and two lower arms are on, the DC current IDC has the maximum voltage phase (referred to as i-phase). Motor current information appears. Then, the currents of the maximum voltage phase and the minimum voltage phase can be observed at two points on the rising side and the falling side of the carrier signal. As shown in FIG. 3, the phases are switched every 60 ° of the inverter output frequency.
[0023]
Hereinafter, the DC current IDC1 (1) or IDC1 (2) in the conduction mode of FIG. 4 (1) is referred to as first DC current information, and the DC current IDC2 (1) or IDC2 (2) in the conduction mode of FIG. Will be described as the second DC current information, and the DC current IDC0 (actually, 0 A) in the conduction mode shown in FIGS. 4 (3) and (4) will be described as the third DC current information.
[0024]
In addition, the sign of the output voltage 7a of the amplifier 7 is prefixed with the sign of V to the corresponding DC current shown in FIG. 4, and VIDC1 (1), VIDC2 (1), and VIDC1 (2), respectively. And VIDC2 (2) and VIDC0. This VIDC0 is the offset voltage described with reference to FIG.
[0025]
Similarly, the code of each DC current is prefixed with AD, and the AD conversion value 8a is calculated by ADIDC1 (1), ADIDC1 (2), ADIDC2 (1), ADIDC2 (2), ADIDC0. Represent. In this case, ADIDC0 corresponds to the zero current information 9a in FIG. 1, and the motor current information 9b corresponds to the ADIDC1 (1), ADIDC1 (2), ADIDC2 (1), and ADIDC2 (2), and each of them corresponds to the energization mode information. 19a, separated by the selector 9. The detection timing of these AD conversion values 8a is determined by the AD activation time determination unit 11 according to the energization mode information 19a.
[0026]
In this embodiment, ADIDC0 corresponding to the zero current information 9a is AD-activated at the timing of the peak and valley sides of the triangular wave of the carrier signal. As another implementation method, AD conversion is performed once per cycle at the timing of the valley side or peak side of the carrier signal, or AD conversion is performed while the inverter circuit 2 is stopped, that is, when all six switching elements are off. Is also good.
[0027]
The AD conversion values of this embodiment, ADIDC1 (1), ADIDC1 (2), ADIDC2 (1), and ADIDC2 (2) are, as shown in FIG. Before and after the phase switches from the upper arm on to the lower arm on, ADID1 (1) and ADIDC2 (1) are continuously AD-converted as a first sequence.
[0028]
Similarly, on the falling side of the carrier signal, at time intervals Tw, before and after the voltage intermediate phase switches from lower arm on to upper arm on, ADIDC1 (2) and ADIDC2 (2) are respectively continued as a second sequence. AD conversion. Note that one of the sequences may be used.
[0029]
In this embodiment, as described above, the currents of two phases are detected at the time interval Tw at timings as close as possible, and the three-phase current is calculated using the relationship in which the sum of the motor currents shown in the following equation (1) is zero. Obtain current information for minutes.
[0030]
0 = Iu + Iv + Iw (Equation 1)
Here, Iu, Iv, and Iw are U-phase, V-phase, and W-phase motor currents, respectively. Thus, when the 3φ / dq coordinate conversion unit 16 performs coordinate conversion of the d-axis and q-axis currents of the rotating coordinate system, it is possible to reduce an error caused by a detection phase shift of the motor current.
[0031]
Next, the digital values corresponding to the DC currents IDC1 (1) and IDC2 (1) and the IDC1 (2) and IDC2 (2) are obtained from the AD conversion values obtained at the above timings according to the formula (2). 5) Calculate by equation. Here, the digital value corresponding to each current is represented by adding the sign of _dig to the end of the code of each current.
[0032]
IDC1 (1) _dig = ADIDC1 (1) -ADIDC0 (Expression 2)
IDC2 (1) _dig = ADIDC2 (1) -ADIDC0 (Expression 3)
IDC1 (2) _dig = ADIDC1 (2) -ADIDC0 (Expression 4)
IDC2 (2) _dig = ADIDC2 (2) −ADIDC0 (Expression 5)
The calculation of Expression (5) to Expression (5) is one of the processes executed by the motor current reproduction unit 14 in FIG.
[0033]
When the actual inverter circuit 2 is driven, a dead time is set in the PWM signal so that the upper arm and the lower arm are not turned on at the same time. The ringing phenomenon in which the motor current oscillates at a high frequency occurs due to the wiring inductance and the stray capacitance from 2 to the motor winding. This ringing current also flows through the DC current IDC. Therefore, the time interval Tw of the AD activation and the timing of the AD activation are determined in consideration of the dead time and the ringing time. further,
Even if the A / D conversion is started, a delay time until the start and a finite time are required for the conversion, and it is important to consider the delay and the conversion time.
[0034]
FIG. 6 shows a carrier signal, a three-phase upper-arm side and lower-arm side PWM signal, two types of DC current IDC, and an AD start timing in consideration of the above. In FIG. 6, the carrier signal is a double carrier signal for generating the dead time. When the two carrier signals coincide with the respective voltage levels (maximum phase, intermediate phase, minimum phase), the states of the PWM signals on the upper arm side and the lower arm side of each phase are changed.
[0035]
The timing at which each of the upper and lower arms of the inverter circuit 2 switches with respect to these PWM signals depends on the polarity of the motor current. In the DC current IDC shown in FIG. 6, the direction flowing out to the motor side is defined as positive, the maximum phase current is positive, the minimum phase current is negative, and the intermediate phase current is positive and negative. Represents the case. As shown in FIG. 6, the output switching timing of the inverter follows the PWM signal of the upper arm when the motor current is positive, and follows the PWM signal of the lower arm when the motor current is negative.
[0036]
However, the polarity of the motor current is unknown until the motor current is detected. Therefore, in order to determine the AD start timing, it is necessary to reliably detect whether the polarity of the motor current is positive or negative. For this purpose, in the present embodiment, the following is specifically described.
[0037]
On the rising side of the carrier signal, ADDC1 (1) and ADIDC2 (1) are successively set as a first sequence before and after the transition point of the upper arm PWM signal of the voltage intermediate phase at a time interval Tw, respectively. And perform A / D conversion.
[0038]
On the falling side of the carrier signal, the voltage intermediate phase is subjected to a second sequence of ADIDC1 (2) and ADIDC2 (2) before and after the transition time of the lower arm-on PWM signal with a time interval Tw as a reference. AD conversion is performed continuously.
[0039]
That is, in any of the above sequences, the side that transitions at an earlier point in time for the upper and lower PWM signals of the intermediate phase is selected. However, in practice, the output of the inverter may switch at a late timing according to the motor current polarity, and the DC current may ring after the switching. Therefore, in this embodiment, the time interval Tw is set to the following (Equation 6). ) Was set to be longer than the time shown in the equation. In equation (6), Td is the dead time, T _rig Is the time until the oscillation of the current attenuates. Here, the time T until the current oscillation attenuates _rig Is the time until the voltage from the peak to the valley of the current oscillation becomes 50% or less of the initial value.
[0040]
Tw = Td + T _rig … (Equation 6)
Time T until current oscillation attenuates _rig Is required to be set longer as the cable connecting the synchronous motor 3 and the inverter circuit 2 becomes longer. In the present embodiment, the AD activation time interval Tw can be set together with the dead time time Td by the AD activation interval setting device 12 for each application.
[0041]
Next, details of the AD converter 8 and a method of creating the time interval Tw of the present embodiment will be described with reference to FIGS. FIG. 7 is a block diagram of the configuration of the AD converter 8. The AD conversion unit 8 includes a first AD conversion unit 81 and a second AD conversion unit 82 that can independently perform AD conversion, a first AD conversion result register 83 that stores an AD conversion result, a second AD conversion result register 84, and each AD conversion unit. An AD conversion timer 85 for timing-starting the conversion unit, a first timer register 86, a second timer register 86, and timer register values TDC1 and TDC2 set in the first timer register 86 and the second timer register 86, respectively. Is compared with timer data of an AD start timer 85, and a first comparator 88 and a second comparator 89 for outputting an AD start signal are provided.
[0042]
The timer register values TDC1 and TDC2 are data set as the AD conversion activation time 11a by the AD activation time determination unit 11. The AD conversion value 8a stored in the first AD conversion result register 83 and the second AD conversion result register 84 is transmitted to the selection unit 9.
[0043]
FIG. 8 is a diagram illustrating the operation of the AD converter 8 in FIG. AD start timer 85
In synchronization with the carrier signal for generating the PWM signal, the half cycle of the carrier signal is counted up as one cycle. When the count value matches the timer register values TDC1 and TDC2, an AD start signal is generated at different timings.
[0044]
In the present embodiment, the difference between the timer register values TDC1 and TDC2 is set to the time interval Tw for starting AD. On the rising side of the carrier signal, the timer register value TDC1 is the sampling time delay T of the AD conversion unit from the transition of the upper arm PWM signal of the voltage intermediate phase. _Smpl On the falling side of the carrier signal, the sampling time delay T of the AD conversion unit from the transition point of the lower arm PWM signal of the voltage intermediate phase. _Smpl Only the earlier timing. This T _Smpl Is set by the AD conversion sampling time setting unit 13 shown in FIG. 1 as the AD sampling time 13a.
[0045]
(Example 2)
In this embodiment, one high-speed AD conversion unit having a short AD conversion time is used instead of the two AD conversion units in FIG. 7 of the first embodiment.
[0046]
FIG. 9 shows the AD converter 8 when one high-speed AD conversion unit is used. The third AD conversion unit 8A2 inputs a plurality of analog inputs via a multiplexer 8A1, which is an input signal destination tacking unit. The AD conversion result of the third AD conversion unit 8A2 is stored by the distributor 8A3 from the AD conversion result register A1 to the AD conversion result register A4 according to the order of the AD conversion.
[0047]
When activated, the AD activation scheduler 8A9 repeats AD conversion a predetermined number of times according to a predetermined procedure, and operates the multiplexer 8A1 to determine which channel's analog input is to be connected to the third AD conversion unit, and , And operates the distributor to select a register according to the order of the AD conversion and store the AD conversion result.
[0048]
The AD start scheduler 8A9 in FIG. 9 performs AD conversion up to six times and performs the first
The A / D conversion and the fourth to sixth A / D conversion are performed on the analog input channel ch0 to which the output of the amplifier 7 is connected. In the second and third A / D conversion, not shown, for example, a DC voltage and an inverter circuit Is AD converted from the analog input channels ch1 and ch2, respectively.
[0049]
The AD activation scheduler 8A9 is activated using the first comparator 88, the first timer register 86, and the AD activation timer 85 as in FIG.
[0050]
FIG. 10 is an explanatory diagram of the operation principle of the AD converter 8 in FIG. When the AD start timer 85 matches the first timer register value TDC1, the AD start scheduler 8A9 is started, and the analog input channel is selected in the order of ch0 → ch1 → ch2 → ch0 → ch0 → ch0, and the AD conversion is sequentially repeated. The A / D conversion results are stored in the A / D conversion result registers A1 to A6 in accordance with the order, and the first and fourth A / D conversion results are stored in the ADID1 (1) and ADIDC2 (1) or ADIDC1 ( 2) and ADIDC2 (2) to the selector 9.
[0051]
In this way, the time interval Tw is realized by repeating the AD conversion using the AD conversion time. For example, if the A / D conversion time is 2 μs, three A / D conversion times of 6 μs are required until the fourth A / D conversion is started, which is the time interval Tw. When the fifth AD conversion result is ADIDC2 (1) or ADIDC2 (2), the time interval Tw is 8 μs. If 6 μs is required for the time interval Tw and the AD conversion time is also 6 μs, the setting of the AD activation scheduler 8A9 is changed, and
The AD conversion of ch0 may be performed for the first time and the second time.
[0052]
On the other hand, the first AD activation time point for obtaining ADIDC1 (1) or ADIDC1 (2), that is, the value TDC1 of the first timer register is determined by the transition of the upper arm PWM signal of the voltage intermediate phase on the rising side of the carrier signal. From the time point, the sampling time delay T of the AD conversion unit _Smpl To which the sampling delay of the AD activation scheduler 8A9 is added to T _Smpl 2 and the sampling signal delay T of the AD conversion unit from the transition point of the lower arm PWM signal on the falling side of the carrier signal on the falling side of the carrier signal. _Smpl To which the sampling delay of the AD activation scheduler 8A9 is added to T _Smpl Assume that the timing is earlier by two. This T _Smpl 2 is set using the AD conversion sampling time setting unit 13.
[0053]
In the above, the method of creating the two types of AD conversion intervals Tw and the AD conversion activation timing has been described. However, since the AD conversion is performed within the pulse width proportional to the phase voltage difference, the AD conversion cannot be performed if the pulse width is narrow. In some cases, a direct current cannot be detected.
[0054]
The solid line in FIG. 11 shows the change of each signal and the DC current IDC when the voltage of the voltage intermediate phase and the voltage of the minimum voltage phase are close. Since the signal sampling time cannot take the AD conversion unit time to be zero, it takes a finite value. As shown by the solid line in FIG. 11, the information of the motor current appearing in the DC current IDC has become shorter than the signal sampling time. In this case, the motor current information cannot be detected.
[0055]
If the pulse interval difference between the phases of the PWM signal determined by the phase voltage cannot be detected, the delay time until the power element is turned on and off with respect to the PWM signal is considered for each PWM signal (number 7) Time T expressed by equation _{pwm_min} The following is the case.
[0056]
T _{pwm_min} = T _rig + T _Smpl + (T _{power_off} -T _{power_on} ) (Equation 7)
Here, each sign is a ringing time T until the oscillation of the current is attenuated. _rig , AD converter sampling time delay T _Smpl , Power element ON delay time T _{power_on} , Power device off delay time T _{power_off} Represents However, when the AD converter 8 has the configuration shown in FIGS. 8 and 9, the sampling time delay T _Smpl T including delay of AD start scheduler instead of _Smpl 2 is used.
[0057]
Therefore, the pulse interval difference between the phases is represented by the following equation (7). _{pwm_min} In the following cases, the carrier frequency was lowered and the inter-phase pulse interval difference was widened in the following cases. The broken line in FIG. 11 indicates that the carrier cycle is doubled by equalizing the voltage level of each phase. As shown in FIG. 11, when the carrier period is doubled, the pulse width is increased and the DC current can be easily detected even when the voltage of the voltage intermediate phase and the voltage of the minimum voltage phase are close.
[0058]
(Example 3)
This embodiment is the same as the first and second embodiments except that the motor current is reproduced using the three-phase motor current estimated value 15a. FIG. 12 shows the relationship between the inverter frequency (or the number of rotations of the motor) and the carrier frequency. As shown in FIG. 12, when the inverter frequency is low, the inverter output voltage is also low, and the pulse interval difference of the PWM signal determined by the phase voltage is also short. _{pwm_min} The following voltage phase increases. For this reason, in order to increase the phase region in which the DC current can be detected, the carrier frequency is reduced in the operating range where the inverter frequency is low, and the carrier frequency is increased with the increase in the inverter frequency. The carrier frequency may be continuously increased, or may be switched to steps as shown in FIG.
[0059]
This switching of the carrier frequency is performed by the coordinate inverse transformation / carrier period determination unit 18 shown in FIG. 1 and the carrier period is switched and transmitted to the PWM signal generation timer information unit 19 as carrier period data 18b.
[0060]
12, the carrier frequency is lowered regardless of the voltage phase, and the carrier cycle is changed for each carrier cycle so that the time interval Tw shown in FIG. 4 can be secured. This is shown in FIG. FIG. 13 shows a carrier signal and a signal wave V which is motor applied voltage information 18a. _u , V _v , V _w And the change of the carrier frequency with respect to the voltage phase on the horizontal axis. As shown in FIG. 13, the carrier frequency has a minimum value fc at a phase where any two phase voltages are equal. _min And the carrier frequency is the maximum value fc in the phase where any one phase voltage becomes 0 _max In other phases, the carrier frequency is automatically adjusted so that the phase voltage pulse interval difference becomes the minimum detectable width shown in Expression (7).
[0061]
The automatic adjustment of the carrier frequency is performed by the following procedure in the coordinate inverse transformation / carrier period determination unit 18 in FIG.
1) The carrier frequency is the maximum value fc _max The voltage pulse interval between the maximum phase and the intermediate phase and the pulse interval between the intermediate phase and the minimum phase are obtained under the conditions of
2) The shorter one of the two pulse intervals is selected and compared with the detectable pulse width obtained by Expression (7).
3) As a result of the comparison, if the pulse width is detectable, fc is set as the carrier frequency. _max give. Conversely, if the pulse width is not detectable, the carrier frequency is reduced so that the pulse width becomes the detectable pulse width obtained by Expression (7).
[0062]
4) The resulting carrier frequency is fc _min If lower, fc _min Limit to Where fc _min The reason for the limitation is to avoid a problem that the current ripple of the motor current increases when the carrier frequency is too low.
[0063]
In this embodiment, the period of the PWM signal is set to be longer in a 1/6 period of the output frequency of the inverter so that the difference between any two phase voltages of the output AC voltage of the inverter is longer in a small phase and shorter in a larger phase. Change. In the method shown in FIG. 13, the carrier frequency changes in a 60 ° cycle. For this reason, the frequency spectrum of the noise generated from the motor due to the PWM frequency component does not concentrate on a specific frequency, so that the sound does not become jarring and is quiet.
[0064]
The method of changing the carrier frequency every 60 ° is also effective in terms of noise reduction, so that it can be used not only for the purpose of detecting a motor current from a DC current, but also for other purposes.
[0065]
Although the three-phase inverter has been described in the present embodiment, the cycle of the PWM signal is similarly set to the n-phase (n> 2 integer) PWM control type inverter by changing the cycle of any two phase voltages of the output AC voltage of the inverter. If the difference is changed within 1 / (2n) cycle of the output frequency of the inverter so that the phase is longer in the phase where the difference is small and shorter in the phase where the difference is large, the same effect as the three-phase inverter of the present embodiment is obtained.
[0066]
(Example 4)
In the present embodiment, the pulse interval difference between the phases is represented by T _{pwm_min} In the case of the following phases, it is different from the first to third embodiments in that the past motor current information already detected at the detectable phase is used. The pulse interval difference between the phases is T _{pwm_min} In the following cases, the carrier frequency cannot be changed, or even if the carrier frequency is changed, the carrier frequency is changed to fc in the example shown in FIG. _min In the case where the pulse interval difference between the phases is limited to T _{pwm_min} The following phases exist.
[0067]
In such a case, past motor current information already detected at a detectable phase is used. In order to obtain the three-phase motor current estimated value 15a from the past motor current information, the three-phase / dq coordinate conversion unit 16, the filter 21, and the dq / 3φ inverse conversion unit 15 shown in FIG. That is, the d-axis q-axis current 16a coordinate-converted based on the motor current reproduction value 14a is subjected to digital filter processing and the output 21a is coordinate-inverted to obtain an estimated motor current value 15a.
[0068]
In the motor current reproduction unit 14, one or both of the motor current information IDC1 (1) _dig and IDC2 (1) _dig obtained at a certain sampling time, or one or both of the IDC1 (2) _dig and IDC2 (2) _dig are The pulse interval difference between the phases of the PWM signal is the time T expressed by equation (7). _{pwm_min} If it is below, the value is not used and the value of the phase corresponding to the mode at that time is used from the three-phase motor current estimated value 15a.
[0069]
As a result, there are the following three types of two-phase motor current detection values obtained in a half cycle of a certain carrier signal.
1) A phase using the three-phase motor current estimated value 15a for both phases.
2) Only one phase uses the three-phase motor current estimated value 15a, and the other phases are detected at that time and use the motor current information 9b.
3) Both phases are detected at that time and use the motor current information 9b.
[0070]
Then, the detection modes (1) → 2) → 3) are switched in the phase direction in which the difference between the phase voltages becomes larger around the phase at which any two phase voltages become equal.
[0071]
14 and 15 show operation waveforms in the present embodiment. FIG. 14 shows operation waveforms at the time of start-up and sudden change in load. FIG. 15 shows an actual phase current waveform in a steady state and a phase current waveform reproduced from the DC current IDC. Is one phase of the motor current reproduction value 14a used in the above. In FIG. 15, the Low level period of the pulse signal waveform is a period in which the value of the three-phase motor current estimated value 15 a output from the dq / 3φ inverse converter 15 is used. It can be seen from the main operation waveform of FIG. 15 that the motor control is performed well.
[0072]
(Example 5)
In the present embodiment, instead of the microcomputer, the control circuit 4 of the first to fourth embodiments has a digital signal processor including an output function of a PWM signal and an AD converter capable of starting an AD in synchronization with the PWM signal ( Embodiment 4 is the same as Embodiments 1 to 4, except that a synchronous motor such as a reluctance motor known as a synchronous reluctance motor and an induction motor are used.
[0073]
(Example 6)
FIG. 16 is a schematic diagram of a module 90 in which the inverter circuit 2, the control circuit 4, and the driver 5 (not shown) of the synchronous motor control device shown in the first to fifth embodiments are incorporated in one package. In FIG. 16, the lid on the upper surface is omitted. In the module 90 of this embodiment, the inverter circuit 2, the control circuit 4, and the driver 5 are housed in a substantially rectangular resin mold package having two sets of opposing sides. The control circuit 4 is mounted on another substrate, and is connected to the substrate on which the inverter circuit 2 and the driver 5 are mounted by lead wires.
[0074]
On the bottom surface of the resin mold package, a metal heat radiating plate having good heat conductivity such as an aluminum alloy or a copper alloy is disposed via an electric insulating layer such as a resin or ceramic plate. On one side of the module, an output terminal portion 51 for connecting three cables for connecting the output of the inverter circuit 2 to the synchronous motor 3 is integrally molded with a resin mold package.
[0075]
On the side opposite to the side on which the output terminal portion is arranged, a terminal for inputting the voltage of the DC power supply 1, a terminal for inputting the speed command, and a power supply terminal for the control circuit 4 and the driver 5 are arranged in a line and integrally formed. A notch is provided between the input terminal 52 of the DC power supply, the terminal for inputting the speed command, and the control terminal 53 such as the power supply terminal of the control circuit 4 and the driver 5 as shown in FIG. It is a passage for electric wires connected to the connector provided inside the module. Although the resistor 6 for detecting the direct current is externally attached to the module 90 in FIG. 16, it may be built in the module 90.
[0076]
(Example 7)
FIG. 17 is a schematic diagram of an outdoor unit 100 of an air conditioner including a synchronous motor control device 100a including the control circuit 4 of the present invention as a drive source of a compressor. The air conditioner according to the present embodiment includes an outdoor unit including a compressor that compresses a refrigerant, and an indoor unit that adiabatically expands the compressed refrigerant to absorb heat, or that compresses the refrigerant to generate heat and radiates heat. In this embodiment, the synchronous motor control device 100a is a module of the sixth embodiment.
[0077]
When the synchronous motor control device of the present invention is applied to a permanent magnet synchronous motor that is a driving source of a compressor, control can be performed without using a motor current sensor and a rotor position sensor, thereby realizing an inexpensive and good air conditioner. it can. In this embodiment, the first to fifth embodiments are applied to the operation control of the motor of the compressor. However, the first to fifth embodiments may be applied to a fan motor of an outdoor unit and a fan motor of an indoor unit. Needless to say. Further, instead of the module of the sixth embodiment, a printed wiring board on which individual components are mounted may be used.
[0078]
(Example 8)
FIG. 18 is a schematic diagram of a refrigerator 110 provided with a synchronous motor control device 110a including the control circuit 4 of the present invention as a drive source of a refrigerator compressor. Although not shown in FIG. 18, the refrigerator of the present embodiment includes a refrigerator compartment and a freezer compartment, and further includes a compressor, a condenser, a freezer compartment evaporator, and a refrigerator compartment evaporator. . In this embodiment, the compressor and the permanent magnet synchronous motor are housed in the same case, and the motor has no rotor position sensor. In the refrigerator of the present embodiment, the synchronous motor control device 110a is the module shown in the sixth embodiment.
[0079]
When the synchronous motor control device of the present invention is used as a drive source of a compressor for a refrigerator, a motor current sensor is not required, so that an inexpensive and good refrigerator can be realized. Instead of the module of the sixth embodiment, a printed wiring board on which individual components are mounted may be used.
[0080]
(Example 9)
FIG. 19 is a schematic diagram of a washing machine 120 in which the motor control device of the present invention is applied to a motor control device of a washing machine. The washing machine of the present embodiment includes a substantially cylindrical washing tub and dewatering tub, a stirring blade disposed at the bottom of the washing tub and dewatering tub, an outer tub containing the washing tub and dewatering tub, a stirring blade or a washing tub. A permanent magnet synchronous motor for rotating the tub / dehydration tub. In the washing machine of this embodiment, the synchronous motor control device 120a is the module shown in the sixth embodiment, and the module is arranged above the motor which is hardly wetted by water.
[0081]
When the synchronous motor control device of the present invention is used as a drive source of a washing machine, a motor current sensor is not required, so that an inexpensive and good washing machine can be realized. Instead of the module of the sixth embodiment, a printed wiring board on which individual components are mounted may be used.
[0082]
(Example 10)
FIG. 20 is a schematic diagram of a cleaner 130 provided with the synchronous motor control device 130a of the present invention as a drive source of the cleaner. The vacuum cleaner of the present embodiment includes a vacuum cleaner main body including a blower for sucking dust, a suction port for sucking dust, and a hose or a pipe portion communicating the suction port with the main body, and the blower is driven by a permanent magnet synchronous motor. Drive. In the vacuum cleaner of this embodiment, the module shown in Embodiment 6 was used as the synchronous motor control device 130a.
[0083]
When the control device for a synchronous motor of the present invention is used as a drive source for a vacuum cleaner, an inexpensive and good vacuum cleaner with motor current sensorless drive can be realized. Instead of the module of the sixth embodiment, a printed wiring board on which individual components are mounted may be used.
[0084]
【The invention's effect】
According to the present invention, motor current information is obtained without using an expensive motor current sensor, and a high-quality motor control device can be realized at low cost.
[Brief description of the drawings]
FIG. 1 is a block diagram of a synchronous motor control device according to a first embodiment.
FIG. 2 is a characteristic diagram of the amplifier according to the first embodiment.
FIG. 3 is an explanatory diagram of a relationship between motor applied voltage information and a carrier signal according to the first embodiment.
FIG. 4 is an explanatory diagram of a relationship between a PWM signal and a DC current according to the first embodiment.
FIG. 5 is a diagram illustrating a relationship between each energization mode and a DC current of the inverter circuit according to the first embodiment.
FIG. 6 is an explanatory diagram of DC current detection timing when a dead time is generated in the first embodiment.
FIG. 7 is a configuration diagram of an AD conversion unit according to the first embodiment.
FIG. 8 is an operation explanatory diagram of FIG. 7;
FIG. 9 is a configuration diagram of an AD conversion unit according to the second embodiment.
FIG. 10 is an operation explanatory diagram of FIG. 9;
FIG. 11 is an explanatory diagram when changing the carrier frequency according to the second embodiment.
FIG. 12 is an explanatory diagram of a relationship between a carrier frequency and an inverter frequency according to the third embodiment.
FIG. 13 is an explanatory diagram of a change in a carrier frequency according to the third embodiment.
FIG. 14 is a diagram showing a motor current waveform at the time of driving the motor in the fourth embodiment.
FIG. 15 is an explanatory diagram of an actual motor current and a reproduced motor current waveform in the fourth embodiment.
FIG. 16 is a schematic diagram of a synchronous motor control device module according to a sixth embodiment.
FIG. 17 is a schematic diagram of an air conditioner including a synchronous motor control device according to a seventh embodiment.
FIG. 18 is a schematic diagram of a refrigerator including a synchronous motor control device according to an eighth embodiment.
FIG. 19 is a schematic view of a washing machine including a synchronous motor control device according to a ninth embodiment.
FIG. 20 is a schematic view of a vacuum cleaner provided with the synchronous motor control device according to the tenth embodiment.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 DC power supply 2 inverter circuit 3 synchronous motor 4 control circuit 5 driver 6 resistor 6 a DC current detection voltage 7 amplifier 7 a output voltage 8 AD converter , 8a: AD conversion value, 9: selector, 9a: zero current information, 9b: motor current information, 11: AD activation time determination unit, 11a: AD conversion activation time, 12: AD activation interval setting device, 13: AD Conversion sampling time setting unit, 13a: AD sampling time, 14: motor current reproduction unit, 14a: motor current reproduction value, 15: dq / 3φ inverse conversion unit, 16: 3φ / dq coordinate conversion unit, 16a: d axis q axis Current, 17: Motor applied voltage generator, 17a: d-axis and q-axis motor applied voltage information, 18: Coordinate inverse transformation / carrier cycle determining section, 18a: 3-phase motor applied voltage information, 18b: Carrier cycle data, 19 ... PWM signal generation timer information section, 19a ... energization mode information, 19b ... PWM signal generation timer information, 22 ... PWM signal generation section, 22a ... PWM signal, IDC, IDC1 (1), IDC2 (1), IDC1 (2) , IDC2 (2) ... DC current, fc _max ... Maximum carrier frequency, fc _min ... minimum carrier frequency, U ⁺ , V ⁺ , W ⁺ ... Positive terminal side switching element, U ⁻ , V ⁻ , W ⁻ ... Negative terminal side switching element, Tw ... Time interval, VIDC0 ... Offset voltage.

Claims (16)

A PWM control type inverter circuit for driving a synchronous motor by converting a DC voltage into a three-phase AC voltage by a plurality of power semiconductor switching elements, a control circuit for performing control processing according to a command speed, and a driver for driving the inverter circuit; A synchronous motor control device including a DC current detector that detects a DC current flowing through the inverter circuit,
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal. A first analog-to-digital conversion and a second analog-to-digital conversion are performed at intervals, and the output current of the inverter is reproduced based on the analog-to-digital converted first DC current information and second DC current information. A synchronous motor control device for controlling a synchronous motor by means of a controller. 2. The control device for a synchronous motor according to claim 1, wherein the power semiconductor switching element of a phase having an intermediate voltage in the three-phase AC voltage output by the inverter is switched within the predetermined time interval. 3. Characteristic synchronous motor control device. The control device for a synchronous motor according to claim 1,
The fixed time interval is a dead time period provided for avoiding simultaneous conduction of the two power semiconductor switching element pairs connected in series of the inverter circuit, and a direct current generated when the power semiconductor switching element switches. A control device for a synchronous motor, wherein the time is longer than a sum of a period until a high-frequency vibration of a current is attenuated. The control device for a synchronous motor according to claim 1,
The AD conversion unit includes a plurality of independent analog-to-digital conversion units, and outputs of the DC current detector are respectively connected to the plurality of analog-to-digital conversion units. A control device for a synchronous motor, wherein a unit is activated to perform the first analog-to-digital conversion and the second analog-to-digital conversion. The control device for a synchronous motor according to claim 1,
The AD converter includes one analog-to-digital conversion unit and input signal selection means for connecting a plurality of analog signals including the DC current detection signal to the analog-to-digital conversion unit. Are input to the analog-to-digital conversion unit in a predetermined order, and the DC current detection signal is analog-to-digital converted at least twice at the predetermined time interval. The control device for a synchronous motor according to claim 1,
At a time other than the predetermined time interval, a time when all the power semiconductor switching elements of the inverter circuit connected to the positive terminal side of the DC power supply turn on, or a time when all the power semiconductor switching elements connected between the negative terminals turn on Alternatively, at the time when all of the six switching elements are turned off, analog-digital conversion is performed to obtain third DC current information, and a difference between the first DC current information and the third DC current information is obtained. The synchronous motor is controlled by reproducing an output current of the inverter circuit based on a difference between the second DC current information and the third DC current information and the PWM signal information. Control device. The control device for a synchronous motor according to claim 1,
A control device for a synchronous motor, wherein the cycle of the PWM signal is lengthened when the output frequency of the inverter circuit is low, and the cycle of the PWM signal is shortened when the output frequency of the inverter circuit is high. The control device for a synchronous motor according to claim 1,
The period of the PWM signal is increased in a phase where the difference between any two phase voltages of the three-phase AC voltages output by the inverter circuit is small, and any two phase voltages of the three-phase AC voltages output by the inverter circuit are increased. A synchronous motor control device which shortens the phase in a phase where the difference is large, and changes the length within 1/6 cycle of the output frequency of the inverter circuit. The control device for a synchronous motor according to claim 1,
In a phase in which the difference between any two phase voltages of the three-phase AC voltages output by the inverter circuit is relatively large, the first DC current information and the second DC current information Reproduce the output current,
In a phase in which the difference between any two phase voltages of the three-phase AC voltages output by the inverter circuit is relatively small, the first or second DC current information and the reproduced inverter circuit current obtained before the present time are A synchronous motor control device for controlling the synchronous motor by estimating and reproducing the current output current of the inverter circuit based on the control signal. The control device for a synchronous motor according to claim 1,
In a phase where the difference between any two phase voltages of the three-phase AC voltages output by the inverter circuit is relatively large, the first DC current information or the second DC current information is compared with a reproduced inverter circuit obtained in the past. Reproduce the current output current of the inverter from the current,
In a phase in which the difference between any two phase voltages of the three-phase AC voltages output by the inverter circuit is relatively small, the current output current of the inverter circuit is estimated from the reproduced inverter circuit current obtained in the past to obtain a synchronous motor. Control device for controlling a synchronous motor. A synchronous motor control module including a package, an inverter circuit that converts a DC voltage into a three-phase AC voltage and drives a synchronous motor, a control circuit that performs control processing according to a command speed, and a driver that drives the inverter circuit. ,
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal. A first analog-to-digital conversion and a second analog-to-digital conversion are performed at intervals, and the output current of the inverter is reproduced based on the analog-to-digital converted first DC current information and second DC current information. A synchronous motor control module, characterized in that the synchronous motor is controlled by the control module. In an air conditioner including an outdoor unit including a compressor that compresses a refrigerant and an indoor unit that adiabatically expands the compressed refrigerant,
A synchronous motor control device for driving the compressor, a DC voltage being converted into a three-phase AC voltage to drive the synchronous motor by an inverter circuit; current detection means for detecting a DC current flowing through the inverter circuit; A control circuit that performs control processing according to, and a driver that drives the inverter circuit,
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal,
In synchronization with the PWM signal, a first analog-to-digital conversion and a second analog-to-digital conversion are performed at fixed time intervals, and the first DC current information and the second DC current information obtained by the analog-to-digital conversion are An air conditioner for controlling a synchronous motor by reproducing an output current of the inverter based on the control signal. In a refrigerator including a refrigerator compartment, a freezer compartment, a compressor that compresses a refrigerant, a condenser, a freezer compartment evaporator, and a refrigerator compartment evaporator,
A synchronous motor control device for driving the compressor, a DC voltage being converted into a three-phase AC voltage to drive the synchronous motor by an inverter circuit; current detection means for detecting a DC current flowing through the inverter circuit; A control circuit that performs control processing according to, and a driver that drives the inverter circuit,
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal. A first analog-to-digital conversion and a second analog-to-digital conversion are performed at intervals, and the output current of the inverter is reproduced based on the analog-to-digital converted first DC current information and second DC current information. A refrigerator for controlling a synchronous motor. A washing tub and spin-drying tub, a stirring blade disposed at the bottom of the washing tub and spin-drying tub, an outer tub containing the washing tub and spin-drying tub, and a synchronous motor for rotating the stirring blade or the washing tub and spin-drying tub. In the equipped washing machine,
The synchronous motor control device converts a DC voltage into a three-phase AC voltage and drives the synchronous motor to drive the synchronous motor; a current detecting unit that detects a DC current flowing through the inverter circuit; and a control process according to a command speed. A control circuit, and a driver for driving the inverter circuit;
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal,
In synchronization with the PWM signal, a first analog-to-digital conversion and a second analog-to-digital conversion are performed at fixed time intervals, and the first DC current information and the second DC current information obtained by the analog-to-digital conversion are A washing machine for controlling a synchronous motor by reproducing an output current of the inverter based on the control signal. In a vacuum cleaner having a main body having a blower for sucking dust, a suction port for sucking dust, and a hose or a pipe portion communicating the suction port with the main body,
A control device for a synchronous motor that drives the blower converts a DC voltage to a three-phase AC voltage to drive the synchronous motor, an inverter circuit, a current detection unit that detects a DC current flowing through the inverter circuit, and a command speed. A control circuit that performs control processing, and a driver that drives the inverter circuit;
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal. A first analog-to-digital conversion and a second analog-to-digital conversion are performed at intervals, and the output current of the inverter is reproduced based on the analog-to-digital converted first DC current information and second DC current information. A vacuum cleaner characterized by controlling a synchronous motor. A PWM control type inverter circuit for converting a DC voltage into an n (n> 2 integer) AC voltage by a plurality of power semiconductor switching elements to drive a synchronous motor, a control circuit for performing control processing according to a command speed, In a synchronous motor control device including a driver that drives an inverter circuit and a DC current detector that detects a DC current flowing through the inverter circuit,
The control circuit includes a timer circuit that creates a PWM signal, and an AD converter that converts the detected DC current from analog to digital in synchronization with the PWM signal. Perform analog-digital conversion a plurality of times at intervals, reproduce the output current of the inverter based on the DC-current information obtained by the analog-digital conversion, and control the synchronous motor,
The cycle of the PWM signal is 1 / (2n) cycle of the output of the inverter circuit so that the difference between any two phase voltages of the output AC voltage output from the inverter circuit is long in a small phase and short in a large phase. A control device for a synchronous motor, characterized in that it is changed within the range.

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