JP2015142394A - motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device in which a calculation load to determine a rotor position is small.SOLUTION: A microcomputer calculates the time between edges 96G and 96H of a sensor input as an electric angle 180° time Tc for which the rotor rotates by 180° in electric angle. The sensor input is a rectangular signal obtained by digitalization of a sinusoidal signal based on variation of magnetic field due to the rotation of the rotor of the motor. The microcomputer divides the calculated electric angle 180° time Tc by a predetermined number of a power of 2 to obtain a time to calculate the thus-obtained time as a unit electric angle time Tu for which the rotor rotates at a unit electric angle which is beforehand obtained by dividing the electric angle 180° by the predetermined number, and starts to count every unit electric angle time Tu from the time when a new edge occurs in the sensor input. The angle obtained by multiplying the count value by the unit electric angle is set as the rotation position of the rotor based on the time at which the new edge occurs in the sensor input.

Description

  The present invention relates to a motor control device, and more particularly to a motor control device for a DC brushless motor using a PWM control method.

  In general, there is a DC brushless motor (hereinafter referred to as “motor”) such as a blower motor that blows air from a vehicle air conditioner. In such a motor control device, a so-called rotating magnetic field is generated in each phase of the stator by applying a rectangular wave voltage rectified to each phase of the stator of the motor by turning on and off the semiconductor element, and is configured by a permanent magnet. The rotor of the motor is rotating.

  In order to generate a rotating magnetic field capable of rotating the rotor, it is necessary to grasp the position of the south pole or the north pole of the permanent magnet constituting the rotor (hereinafter referred to as “rotor position”). In a DC brushless motor, for example, a magnetic field of a rotor is detected by a Hall sensor using a Hall element that is a semiconductor, and a voltage corresponding to the polarity and strength of the magnetic field is output as a signal.

  FIG. 7 shows an example of a schematic analog waveform 92U, 92V, 92W of the voltage output from the Hall sensor provided in each phase of the motor, and a digital waveform 94U obtained by obtaining the analog waveforms 92U, 92V, 92W through a circuit such as a comparator. It is a figure which shows an example of the outline of 94V, 94W. In the digital waveforms 94U, 94V, 94W, voltage changes are shown as edges 96A, 96B, 96C, 96D, 96E, 96F. By detecting these edges 96A, 96B, 96C, 96D, 96E, and 96F, the position of the rotor can be grasped as an electrical angle shown on the horizontal axis of FIG.

  However, in order to rotate the motor smoothly, it is necessary to grasp the position of the rotor between the edges. In Patent Document 1, the angular velocity of the rotor between the edges of the digital waveform is calculated, and the position of the rotor between the edges is calculated using the calculated angular velocity. Specifically, the amount of change in the electrical angle from the edge detected immediately before is calculated by multiplying the elapsed time from the time when the edge occurred immediately before by the calculated angular velocity, and the amount of change in the calculated electrical angle is calculated. Is added to the electrical angle of the edge detected immediately before to calculate the rotor position.

JP 2011-10401 A

  However, the technique described in Patent Document 1 requires calculations related to division and guard processing to calculate the angular velocity of the rotor, and this calculation has a problem that a load is high in a low-performance microcomputer.

  The present invention has been made in view of the above, and an object of the present invention is to provide a motor control device with a small calculation load related to the calculation of the rotor position.

  In order to achieve the above object, the motor control device according to claim 1 detects a magnetic field that changes as the rotor of the motor rotates, and outputs a signal corresponding to the detected change in the magnetic field. And a signal conversion unit that converts a signal output from the magnetic field detection unit into a rectangular wave signal having an edge for each predetermined electrical angle, and a time between edges of the rectangular wave signal converted by the signal conversion unit. It is expressed by a predetermined bit, and from a time between edges of the rectangular wave signal expressed by the predetermined bit, a predetermined number of the number of bits of the predetermined bit and a power of 2 in decimal notation A unit which is a time for which the rotor rotates a unit electrical angle obtained by subtracting the predetermined electrical angle by the predetermined number by extracting a number of higher bits corresponding to the difference from the power Calculate electrical angle time When a new edge is generated in the rectangular wave signal, the counting is started every unit electrical angle time, and the counted value is multiplied by the unit electrical angle, whereby a new signal is added to the rectangular wave signal. And a controller that calculates the rotational position of the rotor with reference to the occurrence of an edge.

  The motor control device according to claim 1, wherein a time obtained by dividing a time between edges of a rectangular wave signal, which is a time required for the rotor to advance by a predetermined electrical angle, by a power of two, is obtained. Is calculated as a unit electrical angle time that is advanced by a unit electrical angle.

  In a Neumann computer that performs arithmetic processing in binary numbers, division processing using an arbitrary decimal number as a divisor has a high load on the computer. However, if the divisor is a power of 2, it can be divided by excluding the number of digits corresponding to the power of the divisor from the dividend expressed in binary, and the above-mentioned unit electrical angle time can be easily obtained even in a low-performance microcomputer. It can be calculated. In other words, by calculating the unit electrical angle time by light-loading processing in a Neumann computer that extracts higher bits from the time between edges expressed by predetermined bits, the load of calculation related to the calculation of the rotor position Can be reduced.

  The motor control device according to claim 2 is the motor control device according to claim 1, wherein the control unit is configured to increase or decrease a level of the rectangular wave signal when a new edge occurs in the rectangular wave signal. In accordance with the calculation of the electrical angle of the position of the rotor when the edge occurs, and by adding the rotational position of the rotor based on when the new edge occurs to the calculated electrical angle, The position of the rotor is calculated.

  According to the motor control device of the second aspect, the position of the rotor when the edge is generated is calculated depending on whether or not the signal on the rectangular wave is at the high level, and the rotor position and the new position when the edge is generated are newly calculated. By adding the rotational position of the rotor with respect to when the edge occurs, the position of the rotor can be calculated with a slight calculation load.

  A motor control device according to a third aspect is the motor control device according to the first or second aspect, wherein the predetermined electrical angle is 180 degrees.

  According to the motor control device of the third aspect, the position of the rotor is calculated by using a signal on a rectangular wave having an edge at every general electrical angle of 180 degrees as a signal indicating the position of the rotor of the DC brushless motor. can do.

  A motor control device according to a fourth aspect is the motor control device according to any one of the first to third aspects, wherein the predetermined number is 256 corresponding to a power of 2 in decimal.

  According to the motor control device of the fourth aspect, 0.703 degrees obtained in advance by multiplying the electrical angle of 180 degrees by 256 can be used as the unit electrical angle, and the accuracy of the rotor position calculation can be maintained. In addition to this, it is possible to suppress the calculation load of the rotor position calculation.

It is a block diagram which shows the outline of an example of a structure of the motor control apparatus which concerns on embodiment of this invention. In the motor control device according to the embodiment of the present invention, a sensor input, which is a waveform obtained by digitizing a signal output from the Hall sensor, is counted by a 16-bit timer, whereby an electrical angle that is a time between edges of the sensor input is obtained. It is the schematic which shows an example at the time of counting 180 degree | times. It is a conceptual diagram of calculation of unit electrical angle time in the motor control apparatus according to the embodiment of the present invention. It is a conceptual diagram which shows an example which calculates the position of the rotor between the edges of a sensor input in the motor control apparatus which concerns on embodiment of this invention by making unit electrical angle time into a compare match value. It is a flowchart which shows an example of the process of the calculation of the position of a rotor in the motor control apparatus which concerns on embodiment of this invention. In the motor control apparatus according to the embodiment of the present invention, the sensor input, which is a waveform obtained by digitizing the signal output from the Hall sensor, is counted by a 16-bit timer, so that the electrical angle 360 is changed from the edge of the electrical angle of 0 degrees. It is the schematic which shows an example at the time of counting time to an edge. It is a figure which shows an example of the outline of the analog waveform of the voltage which the Hall sensor with which a motor is provided in each phase outputs, and the outline of the digital waveform which obtained the analog waveform via circuits, such as a comparator.

  FIG. 1 is a block diagram showing an outline of an example of the configuration of a motor control device 10 according to the present embodiment. As an example, the motor control device 10 shown in FIG. 1 controls a motor 16 that is a kind of so-called blower motor used for blowing air from an in-vehicle air conditioner. The motor 16 shown in FIG. 1 is a three-phase six-pole DC brushless motor as an example.

  The rotor 24 of the motor 16 is composed of three S-pole and N-pole permanent magnets. The magnetic field of the rotor 24 is detected by the hall sensor 52. The hall sensor 52 may detect the magnetic field of a sensor magnet fixed coaxially with the rotor shaft.

  The hall sensor 52 is a sensor for detecting the position of the rotor 24 by detecting a magnetic field formed by the rotor 24 or the sensor magnet. The hall sensor 52 includes three hall elements corresponding to U, V, and W phases. The Hall sensor 52 outputs the change in the magnetic field generated by the rotation of the rotor 24 as a signal of a change in voltage of an analog waveform that approximates the sine wave shown in FIG.

  The signal output from the hall sensor 52 is input to the microcomputer 40 which is a control circuit. The microcomputer 40 is an integrated circuit, and the power supplied from the power source 80 is controlled by the standby circuit 60.

  The analog waveform signal input from the hall sensor 52 to the microcomputer 40 is input to the hall sensor edge detection unit 66 provided with a circuit for converting an analog signal such as a comparator into a digital signal in the microcomputer 40. The hall sensor edge detector 66 converts the input analog waveforms 92U, 92V, and 92W into the digital waveforms 94U, 94V, and 94W shown in FIG. 7, and the edges 96A, 96B, and 96C are converted from the digital waveforms 94U, 94V, and 94W. , 96D, 96E, and 96F are detected.

  Information on the digital waveforms 94U, 94V, 94W and the edges 96A, 96B, 96C, 96D, 96E, 96F is input to the motor position estimating unit 64, and the position of the rotor 24 is calculated. The calculated position information of the rotor 24 is input to the energization control unit 68.

  Further, a signal for instructing the rotational speed of the motor 16 (rotor 24) is input to the command value calculation unit 62 of the microcomputer 40 via the air conditioner ECU 78 which is an electronic control unit of the in-vehicle air conditioner. A command related to the rotational speed of the motor 16 is extracted from the signal input from the air conditioner ECU 78 and input to the energization control unit 68.

  The energization control unit 68 determines the drive duty value based on the position of the rotor 24 calculated by the motor position estimation unit 64 and the rotational speed of the rotor 24 instructed by the air conditioner ECU 78. The energization control unit 68 performs PWM control that generates a PWM signal that is a pulse signal corresponding to the drive duty value and outputs the PWM signal to the voltage supply unit 50.

  The voltage supply unit 50 includes a three-phase (U-phase, V-phase, W-phase) inverter. As shown in FIG. 2, the voltage supply unit 50 includes three N-channel field effect transistors (MOSFETs) 74U, 74V, and 74W (hereinafter referred to as “FETs 74U, 74V, and 74W”), each serving as an upper stage switching element. Includes three N-channel field effect transistors (MOSFETs) 76U, 76V, and 76W (hereinafter referred to as “FETs 76U, 76V, and 76W”) as lower-stage switching elements. The FETs 74U, 74V, and 74W and the FETs 76U, 76V, and 76W are collectively referred to as “FET74” and “FET76” when they do not need to be distinguished from each other, and “U” when they need to be distinguished from each other. , “V”, “W” are attached with symbols.

  Of FET 74 and FET 76, the source of FET 74U and the drain of FET 76U are connected to the terminal of coil 30U, the source of FET 74V and the drain of FET 76V are connected to the terminal of coil 30V, the source of FET 74W and the source of FET 76W. The drain is connected to the terminal of the coil 30W.

  The gates of the FET 74 and FET 76 are connected to the energization control unit 68, and a PWM signal is input. The FET 74 and FET 76 are turned on when an H level PWM signal is input to the gate, and current flows from the drain to the source. Further, when an L level PWM signal is input to the gate, the transistor is turned off and no current flows from the drain to the source.

  Further, the motor control device 10 of the present embodiment includes a power source 80, a noise prevention coil 82, smoothing capacitors 84A and 84B, and the like. The power source 80, the noise prevention coil 82, and the smoothing capacitors 84A and 84B constitute a substantially DC power source.

  Next, calculation of the position of the rotor 24 in the motor control device 10 according to the embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the Hall sensor 52 includes three Hall elements respectively corresponding to the U phase, the V phase, and the W phase of the motor 16. Therefore, the description using FIGS. For each of the phase and the W phase. However, since the calculation of the position of the rotor 24 is the same for all of the U phase, the V phase, and the W phase, in the following description using FIGS. 2 to 4, matters common to the U phase, the V phase, and the W phase will be described. .

  FIG. 2 shows the sensor input of the motor control device 10 according to the present embodiment by counting the sensor input, which is a waveform obtained by digitizing the signal output from the Hall sensor 52, using the timer C which is a 16-bit timer. It is the schematic which shows an example at the time of counting the electrical angle 180 degree | times time Tc which is the time between edges. In the sensor input, an edge is generated for each predetermined electrical angle (for example, electrical angle of 180 degrees). In the present embodiment, assuming that the predetermined electrical angle is, for example, 180 degrees, a rectangular wave is obtained as follows. The electrical angle 180 degree time Tc, which is the time between the edges of the signal, is counted.

  The timer C is, for example, a timer built in the microcomputer 40, and calculates the time by counting the base clock of the microcomputer 40 every 16 bits and integrating the count value. In FIG. 2, as an example, with the generation of the sensor input edge 96G, the timer C counts the base clock of the microcomputer 40 every 16 bits to obtain a count C value, and accumulates the count C value. Then, the electrical angle 180 degree time Tc is calculated from the input timer value which is an integrated value of the count C value until the edge 96H of the sensor input occurs.

  The calculated electrical angle 180 degree time Tc is divided by a predetermined number to calculate a unit electrical angle time Tu that is a time to advance (rotate) by a predetermined electrical angle. The predetermined electrical angle can be set arbitrarily, but is set to about 1 degree as an example. This is because the degree of accuracy for detecting the position of the rotor 24 is reasonable if it is about 1 degree. The predetermined number needs to be a power of two. This is because if the microcomputer 40 is a Neumann computer, division processing with a power of 2 as a divisor is easy.

  In the present embodiment, as an example, a time obtained by dividing the electrical angle 180 degree time Tc by 256 = 2 to the 8th power is 0.703 degrees as a predetermined electrical angle, and the time required to advance the 0.703 degrees is obtained. The unit electrical angle time Tu is assumed. If the calculation load of the microcomputer 40 does not matter so much, the predetermined number is, for example, 1024 = 2 to the 10th power or 512 = 2 to the 9th power, and the predetermined electrical angle is 0.176 degrees or 0.352, respectively. By setting the degree, the calculation accuracy of the position of the rotor 24 may be increased. If it is desired to reduce the calculation load of the microcomputer 40, the predetermined electrical angle may be set to, for example, 128 = 2 to the seventh power, and the predetermined electrical angle may be set to 1.41 degrees.

  FIG. 3 is a conceptual diagram of calculation of the unit electrical angle time Tu in the motor control device according to the present embodiment. In this embodiment, as shown in FIG. 3A, the electrical angle 180 degree time Tc is expressed by 16 bits, and as shown in FIG. 3B, the upper 8 bits are used as the unit electrical angle time Tu. Extract.

  If the microcomputer 40 is a Neumann system, internal processing is performed in binary. Therefore, the electrical angle 180 degree time Tc is expressed by, for example, a 16-digit binary number, and the upper 8 digits are extracted, in other words, the lower 8 digits are discarded, resulting in a decimal electrical angle of 180 degrees. This is the same as dividing the time Tc by the decimal number 256.

  In the calculation in the microcomputer 40, division is a process with a high load, but the process of extracting the upper 16 bits of 16 bits has a light load on the microcomputer 40 which is a Neumann computer. Therefore, with the arithmetic processing shown in FIG. 3, the unit electrical angle time Tu can be calculated even if the performance of the microcomputer 40 is not so high. If the predetermined number is set to 128, 512, or 1024 other than 256, the lower 7 bits, 9 bits, or 10 bits of 16 bits are rounded down to obtain the upper 9 bits, 7 bits of 16 bits. Alternatively, 6 bits are extracted. Such extraction is synonymous with dividing the decimal electrical angle 180 degree time Tc by the decimal number 128, 512 or 1024.

  The electrical angle 180 degree time Tc may be expressed by bits other than 16 bits, such as 24 bits or 32 bits. As described above, if the predetermined number is also a power of 2 other than 256, the process of calculating the unit electrical angle time Tu is as follows.

  For example, from the electrical angle of 180 degrees expressed by a predetermined bit other than 16 bits, a number of upper bits corresponding to the difference between the number of bits of the predetermined bit and a predetermined number of powers that is a power of 2 By extracting, the unit electrical angle time Tu can be calculated.

  FIG. 4 is a conceptual diagram showing an example of calculating the time between the sensor input edges using the unit electrical angle time Tu as a compare match value in the motor control device according to the present embodiment. In many cases, a processor such as the microcomputer 40 includes an 8-bit counter in addition to a 16-bit counter. Therefore, the 8-bit counter is a counter A that is a compare timer, and the compare match value of the counter A is set to a unit electrical angle. The time Tu, that is, the time for the rotor 24 to advance by 0.703 degrees in electrical angle is set. The counter A counts the base clock of the microcomputer 40 every 8 bits, and integrates the count value every 8 bits up to the compare match value.

  In this embodiment, an 8-bit counter is used as counter B which is a free-run counter. The counter B accumulates, as a timer value, the number of times that the counter A has counted up to the compare match value after a new edge, for example, an edge with an electrical angle of 0 degrees, is generated in the sensor input.

  As described above, the compare match value is the time for the rotor 24 to advance by 1/256 of the electrical angle of 180 degrees. Therefore, if the rotation speed of the rotor 24 does not change, and if the timer value is counted from 0 when an edge with an electrical angle of 0 degrees occurs in the sensor input, the sensor input when the timer value is counted to 255 This coincides with the timing at which an edge having an electrical angle of 180 degrees occurs.

Therefore, in the present embodiment, the rotational position of the rotor 24 based on when an edge occurs in the sensor input is obtained by multiplying the timer value of the counter B (counter B value) at an arbitrary timing by 0.703 degrees. The electrical angle obtained in this way is calculated by the following equation (1).

Rotation position of rotor with reference to edge generation
= Counter B value × 0.703 (1)

FIG. 4 shows a case where the rotational position of the rotor 24 is calculated based on the occurrence of an edge at an electrical angle of 0 degrees, but the rotational position of the rotor 24 is also based on the occurrence of an edge at an electrical angle of 180 degrees. It can be calculated in the same manner as described above.

  In addition, the position of the rotor 24 is obtained by adding an electrical angle indicating the position of the rotor when the edge is generated to the rotational position of the rotor 24 based on the edge generation time calculated using the above formula (1). Can be obtained.

  As shown in FIG. 2, the sensor input is a rectangular wave signal having an edge at every electrical angle of 180 degrees, and the level of the signal changes at every electrical angle of 180 degrees. For example, if the sensor input is at a high level between an electrical angle of 0 degrees and an electrical angle of 180 degrees, the sensor input is at a low level between an electrical angle of 180 degrees and an electrical angle of 360 degrees. Note that the electrical angle indicated on the horizontal axis in FIG. 2 is for convenience in order to make it easy to understand that an edge is generated every 180 degrees in the sensor input.

  In the present embodiment, the position of the rotor 24 when a new edge occurs is calculated depending on whether the sensor input when the new edge occurs is high level or low level. However, as shown in FIG. 2, an edge is generated at an electrical angle of 180 degrees in the sensor input, but the edge position with respect to the electrical angle indicating the absolute position of the rotor 24 is U phase, V phase, W phase. Further, it can be changed depending on the installation position of the Hall element of the Hall sensor 52.

  For example, if the relationship between the sensor input, which is a signal on a rectangular wave, and the electrical angle indicating the absolute position of the rotor 24 is as shown in FIG. 7, when a new edge occurs in the sensor input, The electrical angle of the rotor is as follows. If the digital waveform (sensor input) when a new edge occurs in the U phase is at a high level, the electrical angle of the rotor 24 when a new edge is detected is 210 degrees. If the digital waveform (sensor input) when a new edge occurs in the V phase is at a high level, the electrical angle of the rotor 24 when a new edge is detected is 330 degrees. Furthermore, if the digital waveform (sensor input) when a new edge occurs in the W phase is at a high level, the electrical angle of the rotor 24 when a new edge is detected is 90 degrees.

  In the present embodiment, the electrical angle of the rotor 24 when a new edge occurs in the sensor input is calculated as described above. Then, a value obtained by adding the calculated value of the above formula (1) to the electrical angle of the rotor 24 when a new edge occurs is set as the position of the rotor 24.

  Note that a 16-bit counter can be used as the counter A or the counter B. However, if the 8-bit counter is used as the counter A, the calculation accuracy of the position of the rotor 24 becomes higher.

  FIG. 5 is a flowchart showing an example of a process for calculating the position of the rotor 24 in the motor control apparatus 10 according to the present embodiment. In step 500, it is determined whether the base clock of the microcomputer 40 is input to the timer C shown in FIG. 2. If the determination is affirmative, the count C value is counted in step 502. If the determination in step 500 is negative, the processing in step 502 is skipped.

  In step 504, it is determined whether or not the edge 96G or 96H as shown in FIG. 2 is generated in the sensor input. If the determination is affirmative, the count C value from the edge 96G to the edge 96H of the sensor input is determined. The electrical angle 180 degrees time Tc is calculated using the integrated value as an input timer value. In step 508, the upper 8 bits of the input timer value that is the electrical angle 180 degrees time Tc are extracted as the compare value of the counter A.

  In step 510, the value of counter A is cleared, in step 512, the value of counter B is cleared, and in step 514, the count C value of timer C is cleared. If the determination at step 504 is negative, the processing at steps 506 to 514 is skipped.

  In step 516, it is determined whether the base clock of the microcomputer 40 is input to the counter A shown in FIG. 4. If the determination is affirmative, the counter A value is counted in step 518. If the determination in step 516 is negative, the process in step 518 is skipped.

  In step 520, it is determined whether or not the counter A has reached the compare match value. If the determination is affirmative, the counter B value is accumulated in step 522. In step 524, it is determined whether the counter B value has reached 256. If the determination is affirmative, the counter B value is cleared in step 526. This is processing when the rotation speed of the motor fluctuates and the counter B value overflows.

  If the determination at step 520 is negative, the processing at steps 522 to 526 is skipped. If the determination at step 524 is negative, the counter B value has not overflowed, so the processing at step 526 is skipped.

  In step 528, it is determined whether or not the timing is arbitrary. If the determination is affirmative, the counter B value at the monitored arbitrary timing is extracted, and the procedure returns to step 500. A value obtained by multiplying the counter B value extracted in step 530 by a predetermined electrical angle of 0.703 degrees is the rotational position of the rotor 24 with reference to the time of edge generation at the sensor input.

  As described above, according to the present embodiment, for example, the time until the rotor 24 advances from the electrical angle of 0 degree to the electrical angle of 180 degrees is calculated as the electrical angle of 180 degrees time Tc. Further, the time obtained by dividing the electrical angle 180 degree time Tc by a predetermined number that is a power of 2 is converted into a unit electrical angle obtained by the rotor 24 dividing the electrical angle 180 degrees by the predetermined number. The unit electrical angle time to advance. Furthermore, the counter 24 is counted every time the unit electrical angle time is reached, and an angle obtained by multiplying the count electrical value by the unit electrical angle is set as the rotational position of the rotor 24 with respect to the time when the edge is generated. It is possible to reduce the calculation load related to the calculation of the position.

  Note that the timer C shown in FIG. 2 counted the time from the electrical angle edge of 0 ° to the electrical angle of 180 ° and the time from the electrical angle of 180 ° to the electrical angle of 360 °. However, as shown in FIG. 6, the time from electrical angle 0 degree to electrical angle 360 may be counted. When the upper 8 bits of the time from the electrical angle 0 degrees to the electrical angle 360 degrees are extracted, the predetermined electrical angle that is a unit for calculating the position of the rotor 24 is 360 / 256≈1.41 degrees.

  In the case of FIG. 6, the value obtained by multiplying the counter B value shown in FIG. 4 by the electrical angle of 1.41 degrees is the rotational position of the rotor 24 with reference to the edge occurrence.

DESCRIPTION OF SYMBOLS 10 ... Motor control apparatus, 16 ... Motor, 24 ... Rotor, 30 (30U, 30V, 30W) ... Coil, 40 ... Microcomputer, 50 ... Voltage supply part, 52 ... Hall sensor, 60 ... Standby circuit, 62 ... Command value calculation 64, motor position estimation unit, 66 ... Hall sensor edge detection unit, 68 ... energization control unit, 74 (74U, 74V, 74W) ... FET, 76 (76U, 76V, 76W) ... FET, 78 ... air conditioner ECU, 80 ... Power source, 82 ... Noise prevention coil, 84A, 84B ... Smoothing capacitor, 92U, 92V, 92W ... Analog waveform, 94U, 94V, 94W ... Digital waveform (sensor input), 96A, 96B, 96C, 96D, 96E, 96F , 96G, 96H ... Edge, Tc ... Electrical angle 180 degree time, Tu ... Unit electrical angle time

Claims (4)

A magnetic field detector that detects a magnetic field that changes with the rotation of the rotor of the motor and outputs a signal according to the detected change in the magnetic field;
A signal converter that converts the signal output from the magnetic field detector into a rectangular wave signal having an edge for each predetermined electrical angle;
The time between the edges of the rectangular wave signal converted by the signal conversion unit is expressed by a predetermined bit, and the time between the edges of the rectangular wave signal expressed by the predetermined bit is By extracting the number of upper bits corresponding to the difference between the number of bits and a predetermined number that is a power of 2 in decimal notation, the predetermined electrical angle is subtracted by the predetermined number The unit electrical angle time, which is the time for which the rotor rotates, is calculated from the unit electrical angle obtained in advance, and counting is started every unit electrical angle time when a new edge occurs in the rectangular wave signal. And a controller that calculates the rotational position of the rotor based on when a new edge occurs in the rectangular wave signal by multiplying the counted value by the unit electrical angle;
A motor control device comprising:   The control unit calculates the electrical angle of the position of the rotor when the edge occurs according to the level of the level of the rectangular wave signal when a new edge occurs in the rectangular wave signal, The motor control device according to claim 1, wherein the position of the rotor is calculated by adding the rotational position of the rotor with reference to the time when the new edge is generated in the calculated electrical angle.   The motor control device according to claim 1, wherein the predetermined electrical angle is 180 degrees.   The motor control device according to any one of claims 1 to 3, wherein the predetermined number is 256 corresponding to a power of 2 in decimal notation.