JP2006230049A - Motor control device and motor current detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device that can exactly detect a motor current by an inexpensive constitution and perform stable motor rotation control. <P>SOLUTION: The motor control device 1 comprises: an inverter 20 that includes a plurality of switching elements, converts an inputted DC voltage to an AC voltage and feeds the drive voltage to a brushless DC motor 80; a motor current detection part 63 that detects a motor current value from a current flowing to the inverter 20; and a PWM waveform generation part 70 that generates a PWM signal for controlling the operation of each switching element of the inverter 20 on the basis of an estimated rotor position. When a pattern of the PWM signal becomes short in the timing of motor current detection in the motor current detection part 63, the PWM waveform generation part 70 changes the pattern of the PWM signal by making a carrier frequency multiplied by n (n is an integer of two or larger) for securing the timing of the motor current detection longer than a prescribed time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor control device and a motor current detection device, and more particularly to a motor control device that drives a three-phase motor such as a brushless DC motor at an arbitrary number of rotations and a motor current detection device that detects the motor current.

  In recent years, in an apparatus for driving a motor such as a compressor in an air conditioner, there is an increasing need for reducing power consumption from the viewpoint of protecting the global environment. Among them, as one of the power saving techniques, an inverter that drives a highly efficient motor such as a brushless DC motor at an arbitrary frequency is widely used. Furthermore, as a driving technique, a sine wave driving technique that is more efficient and can reduce noise is attracting attention as compared with the rectangular wave driving that is driven by a rectangular wave current.

  When driving a motor such as a compressor in an air conditioner, it is difficult to attach a sensor that detects the position of the rotor of the motor, so a position sensorless sine wave that drives while estimating the position of the rotor by some method Driving techniques have also been invented. Further, as a method for estimating the position of the rotor, there is a method for estimating the rotor induced voltage.

  For example, Patent Document 1 is known as a motor driving device that detects a phase current with an inexpensive configuration in position sensorless sine wave driving based on estimation of an induced voltage. According to the motor drive apparatus of the same document, an inverter, a current detection unit that detects an inverter bus current, an induced voltage estimation unit that estimates a motor induced voltage from an output voltage value of the inverter and a current value by the current detection unit, were estimated. A rotor position speed detector for estimating the rotor position of the motor based on the induced voltage estimation value, a PWM signal generator for generating a PWM signal for controlling the inverter based on the estimated rotor position information, and a PWM signal generator; A duty correction unit that corrects the duty of the generated PWM signal is provided, and the duty correction unit changes the PWM signal during a period in which the current detection unit detects the inverter bus current with the duty of the PWM signal generated by the PWM signal generation unit. The duty is corrected so as not to be generated.

JP 2003-189670 A

  However, in the technique of this document, when the PWM duty is corrected, the duty is corrected so that the three-phase applied voltage does not change in units of two carrier periods. Since it becomes large, there exists a problem that stable motor rotation control cannot be performed.

  The present invention has been made in view of the above problems, and a motor control device capable of accurately detecting a motor current with an inexpensive configuration and capable of performing stable motor rotation control, and a motor for detecting the motor current An object is to provide a current detection device.

  In order to solve the above-described problems and achieve the object, the present invention includes an inverter that includes a plurality of switching elements, converts an input DC voltage into an AC voltage, and supplies the drive voltage to a three-phase motor. Motor current detection means for detecting a motor current value from the current flowing through the inverter, and rotor position estimation means for estimating the rotor position of the three-phase motor based on the motor current value detected by the motor current detection means And PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the estimated rotor position, wherein the PWM signal generating means is the motor current detecting means. In the case of the PWM signal pattern in which the motor current detection timing at the time becomes short, the motor current detection timing of a predetermined time or more is ensured. Ku, the carrier frequency n (where, n is an integer of 2 or more) and times, and, and changing the pattern of the PWM signal.

  Further, the present invention provides a motor current detection device that detects a motor current from a direct current flowing in an inverter that drives a three-phase motor, generates a PWM signal that controls the operation of each switching element of the inverter, and the motor current PWM signal generating means for outputting the sample timing signal, and motor current detecting means for detecting a motor current value from the current flowing through the inverter based on the sample timing signal, the PWM signal generating means, In the case of the PWM signal pattern in which the motor current detection timing in the motor current detection means becomes short, the carrier frequency is set to n (where n is an integer of 2 or more) in order to ensure the motor current detection timing of a predetermined time or more. ) And the PWM signal pattern is changed and the sample is changed. And changes the timing signals.

  According to the present invention, in the case of a PWM signal pattern in which the motor current detection timing in the motor current detection means is shortened, the PWM signal generation means has a carrier frequency to ensure a motor current detection timing of a predetermined time or more. Is multiplied by n (where n is an integer greater than or equal to 2), and the pattern of the PWM signal is changed, so that the output value of the three-phase voltage in the basic carrier cycle unit is not changed, Motor controller capable of accurately sampling motor current from flowing current, accurately detecting motor current with an inexpensive configuration, and capable of performing stable motor rotation control, and motor for detecting the motor current There is an effect that it is possible to provide a current detection device.

  The best mode of a motor control device and a motor current detection device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  FIG. 1 is a block diagram illustrating a configuration example of a motor control device 1 according to the present embodiment. As shown in FIG. 1, the motor drive device 1 includes a DC power supply 10, an inverter 20 that supplies a drive voltage to the brushless DC motor 80, a DC voltage detection circuit 30 that detects a voltage applied to the inverter 20, and an inverter 20. A DC current detection circuit 40 that detects a current flowing through the inverter 20, an inverter drive circuit 50 that drives the inverter 20, a control circuit 60 that controls the inverter drive circuit 50, and a brushless DC motor 80 are provided.

  The brushless DC motor 80 includes a stator 81 to which a three-phase winding is attached, and a rotor 82 to which a magnet is attached. Unconnected ends of the U-phase winding, V-phase winding, and W-phase winding of stator 81 are connected to the U-phase terminal, V-phase terminal, and W-phase terminal of inverter 20, respectively.

  The inverter 20 includes a half-bridge circuit composed of a pair of switching elements for three phases for the U-phase, V-phase, and W-phase, and a free-wheeling diode is connected in parallel to each switching element. A DC voltage output from the DC power supply 10 is applied to the half bridge circuit. A gate drive signal is input from the inverter drive circuit 50 to the control terminal (gate terminal) of each switching element. The DC voltage applied to the inverter 20 is converted into a three-phase AC voltage by the switching operation of the switching element in the inverter 20, thereby driving the brushless DC motor 80.

  The DC voltage detection circuit 30 is connected to the connection point of the voltage dividing resistors Rh and Rl, detects the applied voltage applied to the inverter 20, and outputs it to the control circuit 60. The DC current detection circuit 40 is connected between both ends of the shunt resistor R, detects the current flowing through the inverter 20, and outputs it to the control circuit 60.

  The control circuit 60 includes a microcomputer, a DSP, and the like, and includes a CPU, a non-volatile memory in which a control program is stored, a volatile memory in which temporary data is stored, an input / output port, an A / D converter, and the like. I have. In FIG. 1, the control circuit 60 is shown by functional blocks. The control circuit 60 includes A / D ports 61 and 62, a motor current detection unit 63, a three-phase to two-phase conversion unit 64, a position / speed error estimation unit 65, an absolute coordinate conversion unit 66, and a speed control unit. 67, a two-phase to three-phase converter 68, a current controller 69, a PWM waveform generator 70, and a PWM output port 71.

The DC voltage detected by the DC voltage detection circuit 30 is A / D converted by the A / D port 61 and input to the PWM waveform generation unit 70 as a voltage value Vdc. The motor current detection unit 63 receives the current value A / D converted from the DC current detection circuit 40 via the A / D port 62, and in accordance with the sample timing signal input from the PWM waveform generation unit 70, The phase current value is detected, the remaining one-phase current value is calculated by the following equation (1), and the three-phase (U-phase, V-phase, Z-phase) current values i _u , i _v , i _w of the motor are 3 Output to the phase-2 phase converter 64.

The three-phase to two-phase conversion unit 64 performs coordinate conversion on the absolute coordinates to the three-phase current values i _u , i _v , i _w input from the motor current detection unit 63 to obtain two-phase current values (iα, iβ ) Is output to the position / speed error estimation unit 65. Here, the two-phase current values (iα, iβ) can be calculated by the following equation (2).

  The position / velocity error estimation unit 65 is based on the two-phase current values (iα, iβ) input from the three-phase to two-phase conversion unit 64 and the actual motor rotation speed (ω (n)) and the actual motor angle (θ (N)) is calculated, and the actual motor speed (ω (n)) is output to the speed controller 67 and the actual motor angle (θ (n)) is output to the absolute coordinate converter 66. Here, the actual motor speed (ω (n)) and the actual motor angle (θ (n)) can be calculated as follows. First, Iγ and Iδ in an arbitrary γδ coordinate system are calculated from the two-phase current values (iα, iβ) in the absolute coordinate system using the following equation (3).

  Next, model currents Imγ (n) and Imδ (n) are calculated using a model formula of the motor current shown in the following formula (4).

  Then, based on the model currents Imγ (n), Imδ (n), iγ, iδ, the following formula (5) is used to calculate the speed error (ΔIδ (n)) and the position error (ΔIγ (n)), respectively. calculate.

  Further, the following equation (6) is used to calculate the motor actual rotational speed (ω (n)) based on the speed error (ΔIδ (n)), and the position error (ΔIγ (n)), motor actual The actual motor angle (θ (n)) is calculated based on the rotation speed (ω (n)).

The speed controller 67 compares the target rotational speed given from the outside with the actual motor rotational speed (ω (n)) input from the position / speed error estimating section 65 to calculate the torque current value (iq ^* ). Further, based on the torque current value (iq ^* ), the excitation current (id ^* ) is calculated using the following equation (7). The speed control unit 67 outputs the calculated torque current value (iq ^* ) and the excitation current (id ^* ) to the current control unit 69.

The current control unit 69 converts the torque current value (iq ^* ) and the excitation current (id ^* ) input from the speed control unit 67 into voltage values, and the torque voltage value (Vq ^* ) and the excitation voltage (Vd ^* ). Is output to the absolute coordinate conversion unit 66. Here, the torque voltage value (Vq ^* ) and the excitation voltage (Vd ^* ) can be calculated by the following equation (8) in the dq coordinate system.

The absolute coordinate conversion unit 66 includes a torque voltage value (Vq ^* ) input from the current control unit 69, an excitation voltage (Vd ^* ), and a motor actual angle (θ (n) input from the position / speed error estimation unit 65. ) To calculate voltages (Vα, Vβ) on the αβ coordinates and output them to the two-phase / three-phase converter 68.

  Specifically, the voltages Vα and Vβ on the αβ coordinates are calculated by the following method. First, an absolute value and an output angle are calculated. Using the following equation (9), the absolute value (Vo) of the voltage of the following equation and the phase (θvo) between the d-axis and the voltage vector on the rotation coordinate axis are calculated.

  Here, since the UVW phase voltage as the final output does not exceed the DC voltage, the upper limit value of Vo is determined using the following equation (10), and the output voltage (Va) is calculated.

  Next, absolute coordinate transformation is performed. From the rotor position angle (θ (n)) and the voltage phase (θvo) on the rotation coordinate axis, the voltage phase (θv) with respect to the α axis is calculated using the following equation (11).

  Further, the voltage (Vα, Vβ) on the αβ coordinate axis is calculated from the output voltage (Va) and the voltage phase (θv) using the following equation (12).

The two-phase / three-phase modulation unit 68 is a three-phase voltage (V _U , V _V , V _W ) based on the two-phase modulation method based on the voltages Vα, Vβ on the αβ coordinates input from the absolute coordinate conversion unit 66. Is calculated and output to the PWM waveform generator 70.

The PWM waveform generation unit 70 is based on the three-phase voltages (V _U , V _V , V _W ) input from the two-phase / three-phase modulation unit 68, for example, a PWM signal (V _PWM ). Here, U-phase PWM duty (U_PWM) = (V _U / Vdc) × 100, V-phase PWM duty (V_PWM) = (V _V / Vdc) × 100, W-phase PWM duty (W_PWM) = (V _W / Vdc) ) × 100.

In the case of a pattern of a PWM signal (V _PWM ) in which the motor current detection timing becomes shorter from the input DC current in the motor current detection unit 63, the PWM waveform generation unit 70 performs PWM correction processing described later, The carrier frequency is increased by n (where n is an integer of 2 or more), and the pattern of the PWM signal is changed.

The PWM waveform generation unit 70 outputs a PWM signal (V _PWM ) to the PWM output port 71. The PWM output port 71 converts the input PWM signal (V _PWM ) into positive and negative energization signals (Up, Un, Vp, Vn, Wp, Wn) for each phase and outputs them to the inverter drive circuit 50. The inverter drive circuit 50 operates each switching element of the inverter 20 according to energization signals (Up, Un, Vp, Vn, Wp, Wn) that are input.

The PWM correction processing of the PWM waveform generation unit 70 will be described in detail with reference to FIGS. 2 and 3 are diagrams showing three-phase voltage (V _U , V _V , V _W ) waveforms during sine wave driving. 2 and 3, the horizontal axis indicates the output angle, and the vertical axis indicates the output voltage.

  In FIG. 2, in a section where the difference between the maximum voltage and the intermediate voltage indicated by C is small, that is, in a section where the duty difference between the maximum phase (= maximum duty phase) and the intermediate phase (= intermediate duty phase) of the PWM signal is small, Sampling time for sampling the motor current from the current cannot be obtained sufficiently. In the section C, the same voltage conversion process described later is performed on the PWM signal. Also, in a section where the intermediate voltage and the minimum voltage indicated by B are small, that is, a section where the duty difference between the intermediate phase and the minimum phase (= minimum duty phase) of the PWM signal is small, the sampling time for sampling the motor current from the direct current Can't get enough. In the section B, a one-phase low voltage conversion process described later is performed on the PWM signal.

  In FIG. 3, in a section where the two-phase voltage indicated by A is small, that is, a section where the two-phase duty of the PWM signal is small, a sufficient sampling time for sampling the motor current from the direct current cannot be obtained. In the section A, a two-phase low voltage conversion process described later is performed on the PWM signal.

  FIG. 4 is a flowchart for explaining the PWM correction processing in the PWM waveform generation unit 70. In the figure, MAX_DUTY indicates the duty value of the maximum phase of the PWM signal, MID_DUTY indicates the duty value of the intermediate phase of the PWM signal, and MIN_DUTY indicates the duty value of the minimum phase of the PWM signal. Note that which phase is the maximum phase, intermediate phase, and minimum phase differs depending on the output angle.

  In FIG. 4, the PWM waveform generation unit 70 rearranges the three-phase PWM duties (U_PWM, V_PWM, W_PWM) in descending order, and sets MAX_DUTY, MID_DUTY, MIN_DUTY in descending order (step S1). The PWM waveform generation unit 70 determines whether or not MID_DUTY−MIN_DUTY <time X necessary for current detection (step S2). Here, in the present embodiment, X is a time required for A / D conversion, for example, X = 5 μsec. The value of X varies depending on the performance of the microcomputer and the delay time of the switching element. When the MID_DUTY−MIN_DUTY <time X required for current detection (“Yes” in step S2), the PWM waveform generation unit 70 determines whether MAX_DUTY <time X required for current detection ( Step S3), if MAX_DUTY <time X required for current detection (“Yes” in step S3), two-phase low voltage conversion processing is executed (step S5), and MAX_DUTY <time required for current detection If it is not X (“No” in step S3), a one-phase low voltage conversion process is executed (step S6).

  On the other hand, if the PWM waveform generation unit 70 does not satisfy MID_DUTY−MIN_DUTY <time X required for current detection (“No” in step S2), MAX_DUTY−MID_DUTY <2X (twice the time X required for current detection). (Step S4). If MAX_DUTY-MID_DUTY <2X (“Yes” in step S4), the same voltage conversion process is executed (step S7), and MAX_DUTY-MID_DUTY. If not <2X (“No” in step S3), the PWM correction process is not executed.

  The two-phase low voltage conversion process will be described with reference to FIG. FIG. 5 shows the relationship between the PWM duty and each phase voltage in one carrier cycle. In the PWM waveform generation unit 70, for example, when a calculation result that outputs a PWM waveform as shown in FIG. 5 (before conversion) is made, the current detectable period is shortened. Sampling time for sampling cannot be sufficiently obtained.

  Therefore, the PWM waveform generation unit 70 converts the PWM waveform shown in FIG. 5 (before conversion) into, for example, the PWM waveform shown in FIG. 5 (after conversion) in order to ensure the motor current detectable time. That is, in the two-phase low voltage conversion process, the PWM waveform generation unit 70 adds a predetermined value (α) to the duty of each phase, doubles the carrier frequency, and sets the maximum phase to the first half. The PWM waveform is converted so that the intermediate phase is arranged in the second half and the minimum phase is arranged evenly in the front-rear direction. In the example shown in FIG. 5 (after conversion), a predetermined value (α) is added to the duty of the UVW phase, the carrier frequency is doubled, the U phase that is the maximum phase is set to the first half, and the intermediate phase Are arranged in the latter half and the W phase, which is the smallest phase, is arranged evenly in the front and rear. Here, the minimum duty phase is distributed evenly in the front-rear direction, but the distribution ratio may be changed.

  The one-phase low-voltage conversion process will be described with reference to FIG. FIG. 6 shows the relationship between the PWM duty and each phase voltage in one carrier cycle. In the PWM waveform generation unit 70, for example, when a calculation result is output that outputs a PWM waveform as shown in FIG. 6 (before conversion), the current detectable period is shortened. Sampling time for sampling cannot be sufficiently obtained.

  Therefore, the PWM waveform generation unit 70 converts the PWM waveform shown in FIG. 6 (before conversion) into, for example, a PWM waveform shown in FIG. 6 (after conversion) in order to ensure the motor current detectable time. That is, in the one-phase low-voltage conversion process, the PWM waveform generation unit 70 adds a predetermined value (α) to the duty of each phase, and doubles the carrier frequency, and makes the maximum phase equal to the front and rear. Further, PWM waveform conversion is performed such that the intermediate phase is arranged in the second half and the minimum phase is arranged in the first half. In the example shown in FIG. 6 (after conversion), a predetermined value (α) is added to the duty of each phase, and the carrier frequency is doubled, and the U phase, which is the maximum phase, is equally distributed between the front and rear. The V phase, which is a phase, is arranged in the second half, and the W phase, which is the minimum phase, is arranged in the first half. Here, the maximum phase is distributed evenly before and after, but the distribution ratio may be changed.

  With reference to FIG. 7, the same voltage conversion process will be described. FIG. 7 shows the relationship between the PWM duty and each phase voltage in one carrier cycle. In the PWM waveform generation unit 70, for example, when a calculation result that outputs a PWM waveform as shown in FIG. 7 (before conversion) is made, the current detectable period is shortened. Sampling time for sampling cannot be sufficiently obtained.

  Therefore, the PWM waveform generation unit 70 converts the PWM waveform shown in FIG. 7 (before conversion) into, for example, the PWM waveform shown in FIG. 7 (after conversion) in order to ensure the motor current detectable time. That is, in the same voltage conversion process, the PWM waveform generation unit 70 converts the PWM waveform such that the carrier frequency is doubled and the maximum phase is concentrated in the first half and the intermediate phase is concentrated in the second half. . In the example shown in FIG. 7 (after conversion), the carrier frequency is doubled, and the maximum phase U phase is concentrated in the first half and the intermediate phase V phase is concentrated in the second half. The PWM waveform generator 70 outputs these converted PWM waveforms to the PWM output port 71.

  The motor current detection timing will be described with reference to FIGS. The PWM waveform generation unit 70 performs the motor current control when the PWM correction process is not performed and when the PWM correction process is performed (two-phase low voltage conversion process, one-phase low voltage conversion process, and same voltage conversion process). Switch the detection timing. The PWM waveform generation unit 70 outputs a detection timing sample timing signal as described below to the motor current detection unit 63, and the motor current detection unit 63 detects the motor current in accordance with the sample timing signal.

  FIG. 8 is a diagram for explaining the motor current detection timing when the PWM correction process is not executed. In FIG. 8, when the PWM correction process is not executed, the positive current of the maximum phase is detected at the rising timing of the maximum phase, and the negative current of the minimum phase is detected at the rising of the intermediate phase.

  FIG. 9 is a diagram for explaining the motor current detection timing at the time of two-phase low voltage conversion. In FIG. 9, at the time of two-phase low voltage conversion, the negative current of the intermediate phase is detected at the rising edge of the minimum phase of the first half carrier, and the negative current of the maximum phase is detected at the rising edge of the intermediate phase of the second half carrier.

  FIG. 10 is a diagram for explaining the motor current detection timing at the time of the one-phase low voltage conversion. In FIG. 10, at the time of one-phase low voltage conversion, the positive current of the intermediate phase is detected at the rising edge of the maximum phase of the first half carrier, and the negative current of the minimum phase is detected at the rising edge of the intermediate phase of the second half carrier. .

  FIG. 11 is a diagram for explaining the motor current detection timing at the time of conversion at the same voltage. At the same voltage conversion time, the positive current of the maximum phase is detected at the rising edge of the maximum phase of the first half carrier, and the positive current of the intermediate phase is detected at the rising edge of the intermediate phase of the second half carrier.

  As described above, according to the motor control device 1 of the present embodiment, the PWM waveform generation unit 70 is predetermined in the case of a PWM signal pattern in which the motor current detection timing in the motor current detection unit 63 becomes short. Since the carrier frequency is increased by n (where n is an integer equal to or greater than 2) and the pattern of the PWM signal is changed in order to ensure a motor current detection timing of time or more, 3 in basic carrier cycle units. The motor current can be accurately sampled from the current flowing through the inverter 20 (shunt resistor R) without changing the output value of the phase voltage, and the sine wave drive of the brushless DC motor 80 is sensorless and low cost. In addition to being able to be realized by the configuration and method, stable motor rotation control by low noise and field weakening effect can be performed.

  In the above embodiment, the triangular wave is used as the carrier. However, the present invention is not limited to this, and for example, a sawtooth wave may be used. Further, the case where the carrier frequency is doubled has been described as an example, but the present invention is not limited to this, and may be three times or more. The motor current detection device of the present invention is not limited to a brushless DC motor, and can be applied to, for example, motor current detection of an induction motor.

  INDUSTRIAL APPLICABILITY The motor control device and the motor current detection device according to the present invention are useful for a motor control device and a motor current detection device that use a brushless DC motor, and are low noise and low in air conditioners, refrigerators, washing machines, cleaners, and ventilation fans. It can be widely used for products that require power consumption and space saving.

It is a block diagram which shows the structural example of the motor control apparatus 1 which concerns on a present Example. It is the figure which showed the three-phase voltage ( _VU , _VV , _VW ) waveform at the time of a sine wave drive. It is the figure which showed the three-phase voltage ( _VU , _VV , _VW ) waveform at the time of a sine wave drive. It is a flowchart for demonstrating the PWM correction process in a PWM waveform generation part. It is a figure for demonstrating the conversion process at the time of 2 phase low voltage. It is a figure for demonstrating the conversion process at the time of 1 phase low voltage. It is a figure for demonstrating the conversion process at the time of the same voltage. It is a figure for demonstrating the motor current detection timing in the case of not performing a PWM correction process. It is a figure for demonstrating the motor current detection timing at the time of 2 phase low voltage conversion. It is a figure for demonstrating the motor current detection timing at the time of 1 phase low voltage conversion. It is a figure for demonstrating the motor current detection timing at the time of the same voltage conversion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor drive device 10 DC power supply 20 Inverter 30 DC current detection circuit 40 DC voltage detection circuit 50 Inverter drive circuit 60 Control circuit 61, 62 A / D port 63 Motor current detection part 64 3 phase-2 phase conversion part 65 Position and speed Error estimation unit 66 Absolute coordinate conversion unit 67 Speed control unit 68 Two-phase to three-phase conversion unit 69 Current control unit 70 PWM waveform generation unit 71 PWM output port 80 Brushless DC motor

Claims (9)

An inverter that includes a plurality of switching elements, converts an input DC voltage into an AC voltage, and supplies the drive voltage to a three-phase motor;
Motor current detection means for detecting a motor current value from the current flowing through the inverter;
Rotor position estimating means for estimating the rotor position of the three-phase motor based on the motor current value detected by the motor current detecting means;
PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the estimated rotor position;
With
In the case of the PWM signal pattern in which the motor current detection timing in the motor current detection means is short, the PWM signal generation means sets the carrier frequency to n ( However, n is an integer of 2 or more), and the PWM signal pattern is changed.   When the difference between the duty value of the intermediate phase and the duty value of the minimum phase is smaller than the first threshold value and the duty value of the maximum phase is smaller than the first threshold value, the PWM signal generating means A predetermined value is added to the value and the carrier frequency is doubled, the maximum phase is arranged in the first half carrier, the intermediate phase is arranged in the second half carrier, and the minimum phase is arranged in the first half carrier and the second half carrier. The motor control device according to claim 1, wherein the motor control device is divided and arranged.   When the difference between the duty value of the intermediate phase and the duty value of the minimum phase is smaller than the first threshold value and the duty value of the maximum phase is not smaller than the first threshold value, the PWM signal generating means A predetermined value is added to the duty value and the carrier frequency is doubled, and the maximum phase is divided into the first half carrier and the second half carrier, the intermediate phase is arranged in the second half carrier, and the minimum phase is set. The motor control device according to claim 1, wherein the motor control device is arranged on the first half carrier.   The PWM signal generating means is configured such that the difference between the duty value of the intermediate phase and the duty value of the minimum phase is not smaller than the first threshold value, and the difference between the duty value of the maximum phase and the duty value of the intermediate phase is the first threshold value. 2. The motor control device according to claim 1, wherein when the second threshold value is smaller than the second threshold value, the maximum phase is concentrated on the first half carrier and the intermediate phase is concentrated on the second half carrier. The PWM signal generating means includes
(A) It is determined whether the difference between the duty value of the intermediate phase and the duty value of the minimum phase of the PWM signal is smaller than a first threshold value,
(B) When the difference between the duty value of the intermediate phase and the duty value of the minimum phase is smaller than the first threshold value, it is determined whether the duty value of the maximum phase is smaller than the first threshold value, and the duty of the maximum phase When the value is smaller than the first threshold value, the first correction process is performed. When the maximum phase duty value is not smaller than the first threshold value, the second correction process is performed.
(C) When the difference between the duty value of the intermediate phase and the duty value of the minimum phase is not smaller than the first threshold value, the difference between the duty value of the maximum phase and the duty value of the intermediate phase is larger than the first threshold value. It is determined whether or not it is smaller than the second threshold value, and if the difference between the maximum phase duty value and the intermediate phase duty value is smaller than the second threshold value, a third correction process is executed,
(D) In the first correction process, a predetermined value is added to the duty value of each phase, the carrier frequency is doubled, the maximum phase is arranged in the first half carrier, and the intermediate phase is set in the second half carrier. Arranging, dividing the minimum phase into the first carrier and the second carrier,
(E) In the second correction process, a predetermined value is added to the duty value of each phase, the carrier frequency is doubled, and the maximum phase is divided into the first half carrier and the second half carrier. The intermediate phase is placed on the second half carrier, and the minimum phase is placed on the first half carrier,
(F) The motor control device according to claim 1, wherein, in the third correction process, the maximum phase is concentrated on the first half carrier and the intermediate phase is concentrated on the second half carrier. In a motor current detection device that detects a motor current from a direct current flowing in an inverter that drives a three-phase motor,
PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter and outputting a sample timing signal of the motor current;
Motor current detecting means for detecting a motor current value from a current flowing through the inverter based on the sample timing signal;
With
In the case of the PWM signal pattern in which the motor current detection timing in the motor current detection means is short, the PWM signal generation means sets the carrier frequency to n ( However, n is an integer of 2 or more), and the PWM signal pattern is changed, and the sample timing signal is changed. When the difference between the duty value of the intermediate phase and the duty value of the minimum phase is smaller than the first threshold value and the duty value of the maximum phase is smaller than the first threshold value, the PWM signal generating means A predetermined value is added to the value and the carrier frequency is doubled, the maximum phase is arranged in the first half carrier, the intermediate phase is arranged in the second half carrier, and the minimum phase is arranged in the first half carrier and the second half carrier. Divide and arrange
The motor current detection means detects a negative current in the intermediate phase at the rising edge of the minimum phase of the first half carrier, and detects a negative current in the maximum phase at the rising edge of the intermediate phase of the second half carrier. 6. The motor current detection device according to 6. When the difference between the duty value of the intermediate phase and the duty value of the minimum phase is smaller than the first threshold value and the duty value of the maximum phase is not smaller than the first threshold value, the PWM signal generating means A predetermined value is added to the duty value and the carrier frequency is doubled, the maximum phase is divided into the first half carrier and the second half carrier, the intermediate phase is arranged in the second half carrier, and the minimum phase is Placed in the first half carrier,
The motor current detecting means detects a positive current in the intermediate phase at the rising edge of the maximum phase of the first half carrier, and detects a negative current in the minimum phase at the rising edge of the intermediate phase of the second half carrier. Item 7. The motor current detection device according to Item 6. The PWM signal generation means is such that the difference between the duty value of the intermediate phase and the duty value of the minimum phase is not smaller than the first threshold value, and the difference between the duty value of the maximum phase and the duty value of the intermediate phase is the first threshold value. If it is smaller than the larger second threshold, the maximum phase is concentrated on the first half carrier, the intermediate phase is concentrated on the second half carrier,
The motor current detecting means detects the positive current of the maximum phase at the rising edge of the maximum phase of the first half carrier, and detects the positive current of the intermediate phase at the rising edge of the intermediate phase of the second half carrier. Item 7. The motor current detection device according to Item 6.

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