Motor control device and motor control method

Abstract

To provide a motor control device and a motor control method capable of avoiding current overshoot that occurs during deceleration of a motor.SOLUTION: A motor control device 200 for controlling driving of a three-phase motor M1 includes a first PWM output part 21 for outputting a first PWM signal for driving high-side switches H-FET11A to 11C and low-side switches L-FET12A to 12C installed in each phase of the three-phase motor M1, a second PWM output part 22 for outputting a second PWM signal obtained by shifting the first PWM signal by 180 ° when the three-phase motor M1 is decelerated, and a control part 25 for performing control for opening a window for detecting a zero cross of a BEMF in synchronization with a rising edge of the BEMF generated in an A phase of the three-phase motor M1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a motor control device and a motor control method. [Background technology]

[0002] There is known a three-phase motor that has a function to reduce the rotational speed by shorting the coil ends in response to the induced voltage (hereinafter referred to as "BEMF (back electromotive force)") generated by the motor rotation during deceleration, thereby consuming energy (see, for example, Patent Document 1). In such a three-phase motor, a method is adopted in which a PWM signal (duty signal) with a phase shift of 180° is applied to the motor's drive circuit in order to reduce the rotational speed in a shorter period of time.

[0003] By shifting the phase by 180 degrees, a larger negative torque can be applied to the motor, resulting in faster deceleration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-44938

[0005] [overview] However, in a conventional three-phase motor, applying a PWM signal with a phase shift of 180 degrees causes the current flowing through each phase of the three-phase motor to overshoot and exceed the rated current (e.g., 3 A), which can result in damage to the three-phase motor and its drive circuit.

[0006] The present disclosure has been made to solve these conventional problems, and its purpose is to provide a motor control device and a motor control method that are capable of avoiding current overshoot that occurs when a motor decelerates.

[0007] In order to achieve the above object, a motor control device according to one embodiment of the present disclosure is a motor control device that controls the driving of a three-phase motor, and includes: a first PWM output unit that outputs a first PWM signal that drives a high-side switch and a low-side switch installed in each phase of the three-phase motor; a second PWM output unit that outputs a second PWM signal that is the first PWM signal shifted by 180° when the three-phase motor is decelerated; and a control unit that controls to open a window for detecting the zero crossing of an induced voltage generated in one phase of the three-phase motor in synchronization with the rising edge of the induced voltage.

[0008] A motor control method according to one embodiment of the present disclosure is a motor control method for controlling the driving of a three-phase motor, wherein when the three-phase motor is driven, a first PWM output unit outputs a first PWM signal that drives a high-side switch and a low-side switch installed in each phase of the three-phase motor, and when the three-phase motor is decelerated, a second PWM output unit outputs a second PWM signal that is the first PWM signal shifted by 180°, and a control unit performs control to open a window for detecting the zero crossing of an induced voltage generated in one phase of the three-phase motor in synchronization with a rising edge of the induced voltage. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit diagram showing a three-phase motor and its drive circuit. [Figure 2] FIG. 2 is a block diagram showing the configuration of the motor control device according to the embodiment. [Figure 3] FIG. 3 is a waveform diagram showing the changes in the BEMF (BEMF_A) generated in the A phase, the PWM signal (Duty_A1) of the A phase before the phase is shifted, and the PWM signal (Duty_A2) of the A phase after the phase is shifted by 180°. [Figure 4A] Figure 4A shows the waveforms of each signal when the PWM phase is not shifted. (1) is the digital signal shaped by the comparator from the BEMF analog signal, (2) is the window open signal (0 is window open), (3) is the BEMF zero cross signal, and (4) is the window open edge. [Figure 4B] Figure 4B shows the waveforms of each signal when the PWM phase is shifted by 180°. (1) is the digital signal shaped by the comparator from the BEMF analog signal, (2) is the window open signal (window open at 0), (3) is the BEMF zero cross signal, and (4) is the window open edge. [Figure 5A] FIG. 5A is a waveform diagram showing the sinusoidal voltage generated in each phase when the phase is shifted by 180°. [Figure 5B] FIG. 5B is a waveform diagram showing the A-phase voltage v2 before the phase is shifted, the A-phase voltage v1 after the phase is shifted by 180°, and the BEMF. [Figure 6] FIG. 6 is an explanatory diagram showing the flow of current when the window is closed, showing State 4 during normal driving and State 5 during reverse braking. [Figure 7] FIG. 7 is an explanatory diagram showing the flow of current when the window is open. [Figure 8] FIG. 8 is an explanatory diagram showing current detection in each of periods "1" to "6" in the "Six_state" shown in FIG. 5A.

[0010] [Detailed explanation] An example of a motor control device according to an embodiment will be described in detail below with reference to the drawings. Note that the embodiments described below are comprehensive or specific examples. The numerical values, shapes, materials, components, component installation positions and connection forms, steps, and step orders shown in the following embodiments are merely examples and are not intended to limit the scope of the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts will be described as optional components.

[0011] Fig. 1 is a circuit diagram showing a three-phase motor M1 (hereinafter abbreviated as "motor M1") and its drive circuit 100. Fig. 2 is a block diagram showing the configuration of a motor control device 200 according to an embodiment. The motor control device 200 according to an embodiment (see Fig. 2) uses reverse braking when decelerating the motor M1 (see Fig. 1).

[0012] Specifically, all high-side or low-side power transistors (H-FETs and L-FETs, described later) are turned on, and the phase voltages of the motor M1 are kept constant while the motor M1 is decelerated. Furthermore, by shifting the PWM signal supplied to the motor M1 by 180° during deceleration, a higher negative torque is generated, and the motor M1 is controlled to decelerate faster.

[0013] As shown in Figure 1, motor M1 has three coils LA, LB, and LC, and resistors RA, RB, and RC, and BEMF(A), BEMF(B), and BEMF(C) connected to the coils LA, LB, and LC, respectively. One end of each of coils LA, LB, and LC is connected to one another at neutral point P0. Hereinafter, coil LA of motor M1 will be referred to as "phase A," coil LB as "phase B," and coil LC as "phase C."

[0014] 1 includes a DC power supply E1, a switch element 10, an inverter circuit 16, a multiplexer 14, and a comparator 15. Note that the switch element 10 is not an essential component and may be omitted.

[0015] Inverter circuit 16 includes high-side field effect transistors (FETs) 11A, 11B, and 11C and low-side FETs 12A, 12B, and 12C for phases A, B, and C. Hereinafter, the high-side FETs will be referred to as "H-FETs" and the low-side FETs will be referred to as "L-FETs." Inverter circuit 16 also includes amplifiers 13a, 13b, and 13c.

[0016] The positive terminal of the DC power supply E1 is connected to a voltage supply point P1 in the inverter circuit 16 via a switch element 10.

[0017] One end (drain) of the H-FET 11A is connected to a supply point P1, and the other end (source) is connected to one end (drain) of the L-FET 12A at a connection point SPA. The other end (source) of the L-FET 12A is connected to ground. The connection point SPA is connected to the three-phase motor M1. That is, the H-FET 11A and the L-FET 12A are connected in series, and the connection point SPA is connected to the coil LA via a resistor RA.

[0018] One end (drain) of H-FET11B is connected to supply point P1, and the other end (source) is connected to one end (drain) of L-FET12B at connection point SPB. The other end (source) of L-FET12B is connected to ground. Connection point SPB is connected to the other end of coil LB via resistor RB of three-phase motor M1. In other words, H-FET11B and L-FET12B are connected in series, and connection point SPB is connected to coil LB via resistor RB.

[0019] One end (drain) of the H-FET 11C is connected to a supply point P1, and the other end (source) is connected to one end (drain) of the L-FET 12C at a connection point SPC. The other end (source) of the L-FET 12C is connected to ground. The connection point SPC is connected to the other end of the coil LC of the three-phase motor M1 via a resistor RC. In other words, the H-FET 11C and the L-FET 12C are connected in series, and the connection point SPC is connected to the coil LC via a resistor RC.

[0020] The gates of the H-FETs 11A to 11C and the L-FETs 12A to 12C are connected to a control unit 25 of the motor control device 200 shown in Fig. 2. The driving of the H-FETs 11A to 11C and the L-FETs 12A to 12C is controlled by a PWM signal output from the control unit 25. That is, by PWM controlling the H-FETs 11A to 11C and the L-FETs 12A to 12C, AC signals with phases shifted by 120° are supplied to the coils LA, LB, and LC of the three-phase motor M1, thereby driving the motor M1.

[0021] An amplifier 13a is connected to both ends (between the drain and source) of L-FET 12A shown in FIG. 1. An amplifier 13b is connected to both ends (between the drain and source) of L-FET 12B. An amplifier 13c is connected to both ends (between the drain and source) of L-FET 12C. Each of the amplifiers 13a to 13c detects the current flowing through the L-FETs 12A to 12C. The output terminals of each of the amplifiers 13a to 13c are connected to three input terminals of a multiplexer 14.

[0022] The output terminal of the multiplexer 14 is connected to one input terminal of the comparator 15. The multiplexer 14 switches the output signals of the amplifiers 13a to 13c and supplies them to the comparator 15. A threshold voltage that determines a threshold current is input to the other input terminal of the comparator 15.

[0023] The comparator 15 compares the output voltage of the multiplexer 14 with a threshold voltage. That is, when the current flowing through each of the L-FETs 12A to 12C exceeds the threshold current, the output signal of the comparator 15 switches from "L" to "H." The comparator 15 functions as a current detection unit that determines whether the current flowing through the low-side switches (L-FETs 12A to 12C) of each phase of the motor M1 exceeds a predetermined threshold current.

[0024] 2, the motor control device 200 includes a first PWM output unit 21, a second PWM output unit 22, a multiplexer 23, an A-phase drive signal 24A, a B-phase drive signal 24B, a C-phase drive signal 24C, and a control unit 25. The motor control device 200 controls the driving of the motor M1.

[0025] When driving the motor M1, the first PWM output unit 21 generates a PWM signal (first PWM signal) having a predetermined duty ratio to be supplied to each of the H-FETs 11A to 11C and each of the L-FETs 12A to 12C. That is, the first PWM output unit 21 outputs the first PWM signal to drive the high-side switch and low-side switch provided in each phase of the motor M1.

[0026] When the motor M1 is decelerating, the second PWM output unit 22 generates a PWM signal (second PWM signal) whose phase is shifted by 180° from the PWM signal (first PWM signal) output from the above-described first PWM output unit 21. That is, when the motor M1 is decelerating, the second PWM output unit 22 outputs the second PWM signal obtained by shifting the first PWM signal by 180°.

[0027] FIG. 3 is a waveform diagram showing the changes in the induced voltage generated in phase A (hereinafter referred to as "BEMF"; BEMF_A), the PWM signal of phase A output from the first PWM output unit 21, i.e., the PWM signal (Duty_A1) before the phase is shifted, and the PWM signal of phase A output from the second PWM output unit 22, i.e., the PWM signal (Duty_A2) with the phase shifted by 180°.

[0028] As shown in Figure 3, the positive amplitude of the PWM signal (Duty_A1) before phase shift is synchronized with the positive amplitude of the BEMF (BEMF_A). Therefore, the voltage generated across the A-phase coil LA and resistor RA is the differential voltage between them. On the other hand, the positive amplitude of the PWM signal (Duty_A2) with a phase shift of 180° is synchronized with the negative amplitude of the BEMF (BEMF_A). Therefore, the voltage generated across the A-phase coil LA and resistor RA is the sum of both voltages, with the opposite polarity. Therefore, by shifting the phase of the PWM signal by 180°, a stronger negative torque can be generated in the motor M1, enabling it to decelerate faster.

[0029] 2, the multiplexer 23 selects either the output signal of the first PWM output unit 21 or the output signal of the second PWM output unit 22 and outputs each of the drive signals 24A to 24C. The multiplexer 23 selects the output signal of the first PWM output unit 21 when driving the motor M1, and selects the output signal of the second PWM output unit 22 when decelerating the motor M1.

[0030] The A-phase drive signal 24A is output to the control unit 25 as a PWM signal for driving the A-phase H-FET 11A and L-FET 12A. The B-phase drive signal 24B is output to the control unit 25 as a PWM signal for driving the B-phase H-FET 11B and L-FET 12B. The C-phase drive signal 24C is output to the control unit 25 as a PWM signal for driving the C-phase H-FET 11C and L-FET 12C.

[0031] The control unit 25 converts each of the drive signals 24A to 24C (PWM signals) into gate drive signals and outputs them to the gates of the H-FETs 11A to 11C and the L-FETs 12A to 12C. The control unit 25 detects the rising edge and falling edge of the BEMF (induced voltage). The control unit 25 sets a period for opening the window, as will be described later.

[0032] Figure 4A shows the waveforms of each signal when the PWM phase is not shifted, where (1) is the digital signal shaped by a comparator from the analog BEMF signal, (2) is the window open signal (window open at 0), (3) is the BEMF zero-cross signal, and (4) is the window open edge. Figure 4B shows the waveforms of each signal when the PWM phase is shifted by 180°, where (1) is the digital signal shaped by a comparator from the analog BEMF signal, (2) is the window open signal, (3) is the BEMF zero-cross signal, and (4) is the window open edge.

[0033] In this embodiment, a sensorless motor is used as the motor M1. In order to measure the rotor position and rotational speed, the sensorless motor detects the time when the induced electromotive force (BEMF) generated in the A phase crosses zero. For this purpose, as shown in FIGS. 4A(2) and 4B(2), the window is opened and both the H-FET 11A and L-FET 12A of the A phase are turned off. In other words, while the window is open, both the H-FET 11A and L-FET 12A are turned off.

[0034] 4A(2), the waveform without phase shift opens the window at a time synchronized with the falling edge of the BEMF (a time slightly earlier than the falling edge). As described above, the window refers to turning off both the A-phase H-FET 11A and L-FET 12A when measuring the zero-crossing point of the BEMF during measurement of the rotational position of the motor M1, and the window open refers to this period.

[0035] On the other hand, in the waveform with a phase shift of 180° as shown in FIG. 4B(2), the window opens at a time synchronized with the rising edge of the BEMF (slightly earlier than the rising edge).

[0036] That is, when the first PWM output unit 21 shown in FIG. 2 is selected, the window is opened in the period shown in FIG. 4A(2), and when the second PWM output unit 22 is selected, the window is opened in the period shown in FIG. 4B(2).

[0037] That is, the control unit 25 performs control to open a window for detecting the zero crossing of the BEMF (induced voltage) in synchronization with the rising edge of the BEMF generated in phase A (one phase) of the motor M1. The control unit 25 detects the zero crossing of the BEMF when the window is opened, and detects the speed of the motor M1 based on the time when the BEMF crosses the zero.

[0038] The reason why the window opens in synchronization with the rising edge when the phase is shifted by 180° will be explained below with reference to the waveform diagrams shown in Figures 5A and 5B. Figure 5A is a waveform diagram showing the sinusoidal drive voltage generated in each phase when the phase is shifted by 180°. The numbers "1," "2," ... "6" in Figure 5A indicate "Six_state," with each section being 60°, for a total of 360°. As shown in Figure 5A, the time when the A-phase voltage v1 changes from positive to negative is t1, and the time when it changes from negative to positive is t2.

[0039] FIG. 5B is a waveform diagram showing the A-phase voltage v2 before the phase is shifted, the A-phase voltage v1 after the phase is shifted by 180°, and the BEMF. As can be seen from FIGS. 5A and 5B, the BEMF rises near the zero-crossing point (time t1) where the A-phase voltage v2 (the voltage before the shift) changes from negative to positive. In other words, the rising edge of the BEMF occurs near time t1. The BEMF falls at the zero-crossing point (time t2) where the A-phase voltage v1 (the voltage after the shift) changes from negative to positive. In other words, the falling edge of the BEMF occurs. As explained above with reference to FIG. 2, by shifting the phase of the A-phase voltage by 180°, a larger negative torque can be generated during deceleration, thereby hastening the deceleration of the motor M1.

[0040] Next, the current flow in inverter circuit 16 (see FIG. 1) when the window is closed and when it is open will be described with reference to the circuit diagrams shown in FIGS. 6 and 7. FIG. 6 is an explanatory diagram showing the current flow when the window is closed, showing State 4 ("4" in FIG. 5A) during normal operation and State 5 ("5" in FIG. 5A) during reverse braking. A-phase and B-phase H-FETs 11A and 11B are off, L-FETs 12A and 12B are on, and C-phase H-FET 11C is on and L-FET 12C is off. As shown in FIG. 6, when the window is closed, current flows in coil LC in the direction of arrow Y1, and current flows in coils LB and LA in the directions of arrows Y2 and Y3.

[0041] In the above, the peak current flowing through phase C can be detected based on the current values ​​detected by the two amplifiers 13a and 13b. Therefore, if an overcurrent exceeding the threshold current flows through each phase of inverter circuit 16, this can be detected by comparator 15, and the current flowing through phase C can be controlled to be equal to or less than the threshold current.

[0042] 7 is an explanatory diagram showing the current flow when the window is open. The A-phase and B-phase H-FETs 11A and 11B are off, the L-FET 12A is off, the L-FET 12B is on, the C-phase H-FET 11C is on, and the L-FET 12C is off. When the window is open as shown in FIG. 7, current flows in the coil LC in the direction of arrow Y1, in the coil LB in the direction of arrow Y2, and in the coil LA in the direction of arrow Y4. In other words, when the window is open, no current flows through the L-FET 12A.

[0043] Next, the measurement of the currents flowing through phases A, B, and C and their current values ​​will be described with reference to Fig. 8. The current value of each phase reaches its peak during the periods indicated by "1" to "6" in Fig. 5A. Specifically, the phase A current reaches its positive peak at "1," the phase C current reaches its negative peak at "2," the phase B current reaches its positive peak at "3," the phase A current reaches its negative peak at "4," the phase C current reaches its positive peak at "5," and the phase B current reaches its negative peak at "6."

[0044] Therefore, it is necessary to control the current values ​​flowing through the A-phase, B-phase, and C-phase in each of the periods "1" to "6" so that they are less than the threshold current allowed by the inverter circuit 16.

[0045] Fig. 8 is an explanatory diagram showing current detection in each of periods "1" to "6" in the "Six_state" shown in Fig. 5A described above. In Fig. 8, "+" indicates current flowing from inverter circuit 16 to motor M1, and "-" indicates current flowing from motor M1 to inverter circuit 16. When the window is open, as shown in Fig. 7, H-FET 11A and L-FET 12A in phase A are both turned off, and therefore, amplifier 13a cannot detect the current flowing through L-FET 12A in phase A.

[0046] Furthermore, as mentioned above, comparator 15 determines whether the current flowing through low-side L-FETs 12A to 12C is equal to or greater than a threshold, and therefore cannot make a threshold determination for high-side H-FETs 11A to 11C. Under these conditions, the current values ​​for periods "1" to "6" are calculated as follows. In the following, the current values ​​flowing through phases A, B, and C will be simply represented by the symbols A, B, and C.

[0047] During the period "1" shown in FIG. 5A, the A-phase current reaches a positive peak. Therefore, during the period "1" shown in FIG. 8, the B-phase current and the C-phase current are both negative. Because no current flows through the A-phase L-FET 12A, the A-phase current cannot be detected. Since "A = B + C" holds, the A-phase current can be calculated from the B-phase current and the C-phase current. Therefore, during the period "1," the comparator 15 can determine whether the A-phase current exceeds the threshold current, and can control it to be below the threshold current.

[0048] During the period "2" shown in Figure 5A, the C-phase current reaches a negative peak value. Because "C = A + B" holds, the C-phase current can be directly detected even if the A-phase current cannot be detected. Therefore, the comparator 15 can determine whether the C-phase current exceeds the threshold current, and if an overshoot occurs in the C-phase current, it can be detected.

[0049] During the period "3" shown in Figure 5A, the B-phase current reaches a positive peak value. "B = A + C" holds. Because the B-phase current is a positive current, it cannot be detected directly. Furthermore, because the A-phase current cannot be detected, even if the C-phase current can be detected, the comparator 15 cannot determine whether the sum of the A-phase current and the C-phase current exceeds the threshold current. As a result, there is a risk that a current exceeding the threshold current will flow through the inverter circuit 16, causing an overshoot.

[0050] During the period "4" shown in Figure 5A, the phase A current reaches a negative peak value. If the window were open, the phase A current would not be detectable. "A = B + C" holds. The phase B current and the phase C current are both positive currents and cannot be detected directly. Therefore, the comparator 15 cannot determine whether the phase A current exceeds the threshold current. For this reason, as with "3" above, there is a risk that a current exceeding the threshold current will flow through the inverter circuit 16, causing an overshoot.

[0051] During the period "5" shown in Figure 5A, the C-phase current reaches a positive peak value. "C = A + B" is established. Because the C-phase current is a positive current, it cannot be detected directly. Furthermore, although the B-phase current can be detected, the A-phase current cannot be detected, so "A + B" cannot be calculated. Therefore, the comparator 15 cannot determine whether the C-phase current exceeds the threshold current. For this reason, as with "3" and "4" above, there is a risk that a current exceeding the threshold current will flow through the inverter circuit 16, causing an overshoot.

[0052] At "6" in FIG. 5A, the B-phase current reaches a negative peak value. "B = A + C" holds true. The B-phase current can be directly detected. Therefore, the comparator 15 can determine whether the B-phase current exceeds the threshold current.

[0053] To summarize the above "1" to "6", the peak value of the current can be detected during the periods "1", "2", and "6" shown in Figure 5A, but the peak value of the current cannot be detected during the periods "3", "4", and "5".

[0054] If the window is opened on the falling edge of the BEMF, the timing will be as shown in "5" above (see time t2 in FIGS. 5A and 5B), and the peak value of the current will not be detected while the window is open, which could result in the current overshooting and damaging the inverter circuit 16. In this embodiment, the window is opened on the rising edge of the BEMF, which results in the timing as shown in "2" above, and the peak value of the current can be detected while the window is open. This prevents the current from overshooting while the window is open, and protects the inverter circuit 16 from overcurrent.

[0055] That is, in the motor control device 200 according to this embodiment, the window is opened in synchronization with the rising edge of the BEMF, so that even when the high-side H-FET 11A and the low-side L-FET 12A in phase A (one phase) are both turned off, the comparator 15 can determine whether the current flowing through each phase exceeds the threshold value. This makes it possible to prevent current overshoot and damage to the inverter circuit 16.

[0056] The motor control device 200 according to this embodiment includes a comparator 15 (current determination unit) that determines whether the current flowing through the low-side switches (L-FETs 12A, 12B, and 12C) in each phase of the motor M1 exceeds a predetermined threshold current, but does not include a sensor that detects the current flowing through the high-side switches (H-FETs 11A, 11B, and 11C). This simplifies the circuit configuration.

[0057] Furthermore, since motor M1 is a sensorless motor, and control unit 25 installed in motor control device 200 detects the speed of motor M1 based on the time when BEMF (back electromotive force) crosses zero, there is no need to provide a sensor for detecting the number of rotations, such as an encoder, which makes it possible to further simplify the circuit configuration.

[0058] (Other embodiments) Although the present disclosure has been described in detail above, it will be apparent to those skilled in the art that the present disclosure is not limited to the embodiments described herein. One or more elements of one embodiment may be combined with one or more elements of another embodiment. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure, as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and explanatory and is not intended to be limiting of the present disclosure.

[0059] (Addendum) The technical ideas that can be understood from the present disclosure are described below. Note that, for the purpose of aiding understanding and not intending to be limiting, the components described in the appendices are given the reference numerals of the corresponding components in the embodiments. The reference numerals are shown as examples to aid understanding, and the components described in each appendix should not be limited to the components indicated by the reference numerals.

[0060] (Appendix 1) A motor control device 200 that controls the driving of a three-phase motor includes a first PWM output unit 21 that outputs a first PWM signal that drives high-side switches (H-FETs 11A, 11B, 11C) and low-side switches (L-FETs 12A, 12B, 12C) installed in each phase of the three-phase motor M1, a second PWM output unit 22 that outputs a second PWM signal that is the first PWM signal shifted by 180° when the three-phase motor M1 is decelerated, and a control unit 25 that controls to open a window for detecting the zero crossing of the induced voltage in synchronization with the rising edge of the induced voltage generated in one phase (for example, phase A) of the three-phase motor M1. According to the motor control device 200 of Supplementary Note 1, the window is opened in synchronization with the rising edge of the BEMF, so that even when the high-side H-FET 11A and the low-side L-FET 12A in the A phase (one phase) are both turned off, the comparator 15 can determine whether the current flowing through each phase exceeds the threshold value. This makes it possible to prevent current overshoot and damage to the inverter circuit 16.

[0061] (Appendix 2) The motor control device 200 according to Supplementary Note 1 further includes a current determination unit (comparator 15) that determines whether or not the current flowing through the low-side switches (L-FETs 12A, 12B, 12C) in each phase of the three-phase motor M1 exceeds a predetermined threshold current. Since no sensor is provided to detect the current flowing through the high-side switches (H-FETs 11A, 11B, 11C), the circuit configuration can be simplified.

[0062] (Appendix 3) In the motor control device 200 according to Supplementary Note 1 or 2, the three-phase motor M1 is a sensorless motor, and the control unit 25 detects the speed of the three-phase motor M1 based on the time when the induced voltage crosses zero. Since there is no need to provide a sensor for detecting the number of rotations, such as an encoder, the circuit configuration can be further simplified.

[0063] (Appendix 4) A motor control method for controlling the driving of a three-phase motor M1, wherein when the three-phase motor M1 is driven, a first PWM output unit 21 outputs a first PWM signal that drives high-side switches (H-FETs 11A, 11B, 11C) and low-side switches (L-FETs 12A, 12B, 12C) installed in each phase of the three-phase motor M1, and when the three-phase motor M1 is decelerated, a second PWM output unit 22 outputs a second PWM signal that is the first PWM signal shifted by 180°, and a control unit 25 performs control to open a window for detecting the zero crossing of the induced voltage in synchronization with the rising edge of the induced voltage generated in one phase of the three-phase motor M1. [Explanation of symbols]

[0064] 10 Switching element 11A, 11B, 11C High-side switches (H-FET) 12A, 12B, 12C Low-side switch (L-FET) 13a, 13b, 13c amplifiers 14 Multiplexer 15 Comparator 16 Inverter circuit 21 First PWM output section 22 Second PWM output section 23 Multiplexer 24A A-phase drive signal 24B B-phase drive signal 24C C-phase drive signal 25 Control Unit 100 Drive circuit 200 Motor control device LA, LB, LC coils M1 3-phase motor (motor)

Claims

1. A motor control device that controls the drive of a three-phase motor, a first PWM output unit that outputs a first PWM signal to drive a high-side switch and a low-side switch installed in each phase of the three-phase motor; a second PWM output unit that outputs a second PWM signal obtained by shifting the first PWM signal by 180° when the three-phase motor is decelerating; a control unit that performs control to open a window for detecting a zero crossing of an induced voltage generated in one phase of the three-phase motor in synchronization with a rising edge of the induced voltage; A motor control device comprising:

2. a current determination unit that determines whether or not a current flowing through a low-side switch in each phase of the three-phase motor exceeds a predetermined threshold current; The motor control device according to claim 1 , further comprising:

3. the three-phase motor is a sensorless motor, The control unit detects the speed of the three-phase motor based on the time when the induced voltage crosses zero.

3. The motor control device according to claim 1 or 2.

4. A motor control method for controlling the drive of a three-phase motor, comprising: When the three-phase motor is driven, a first PWM output unit outputs a first PWM signal for driving a high-side switch and a low-side switch installed in each phase of the three-phase motor; When the three-phase motor is decelerating, a second PWM output unit outputs a second PWM signal obtained by shifting the first PWM signal by 180°, A control unit performs control to open a window for detecting a zero crossing of an induced voltage in synchronization with a rising edge of the induced voltage occurring in one phase of the three-phase motor. Motor control methods.

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