Motor drive control device

Abstract

A device according to the present disclosure is a motor drive control device that generates PWM drive signals for driving a brushless motor. The device is provided with a PWM drive signal generating circuit that generates the PWM drive signals at a PWM frequency of at least 280 KHz.

Description

Motor drive control device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority based on Japanese patent application No. 2024-101636 filed on June 25, 2024, and Japanese patent application No. 2025-6647 filed on January 17, 2025, the entire disclosures of which are incorporated herein by reference.

[0002] The present disclosure relates to a motor drive control device.

[0003] JP2018-133890A discloses a motor control device that PWM controls a brushless motor. In the prior art, PWM control of a brushless motor is generally performed at a PWM frequency of about 20 KHz to 100 KHz.

[0004] The inventors of the present disclosure have discovered that when a brushless motor is driven, not only drive power but also braking power is generated. The inventors of the present disclosure have also discovered that the amount of braking power generated depends on the PWM frequency. Therefore, a motor drive control device that generates less braking power is desired.

[0005] The present disclosure has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0006] According to one aspect of the present disclosure, there is provided a motor drive control device that generates a PWM drive signal for driving a brushless motor. The motor drive control device includes a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or higher. With this motor drive control device, braking current can be reduced to a negligible level.

[0007] 1 is a block diagram showing the configuration of a motor system in a first embodiment. Graphs showing the drive waveform, voltage, and current of a brushless motor. Graphs showing the difference in braking current depending on PWM frequency. Graphs showing changes in braking current according to PWM frequency. Block diagram showing the function of an input signal generation circuit in a first embodiment. Block diagram showing the function of a PWM drive signal generation circuit. Timing chart showing the operation of the PWM drive signal generation circuit. Timing chart showing the operation of a startup trigger circuit. Block diagram showing the function of an input signal generation circuit in a second embodiment. Timing chart showing the operation of a clip circuit. Block diagram showing the configuration of a motor system in a third embodiment. Block diagram showing the configuration of an input signal generation circuit. Block diagram showing the configuration of a rotation direction switching circuit. Block diagram showing the configuration of a differential amplifier unit. Block diagram showing the configuration of a PWM drive signal generation circuit. Timing chart showing the operation of the PWM drive signal generation circuit. Block diagram showing the configuration of a rotation flag generation circuit. Timing chart showing the operation of the startup trigger circuit. Block diagram showing the configuration of an input signal generation circuit in a fourth embodiment. Timing chart showing the operation of the startup trigger circuit in the fourth embodiment. Block diagram showing the configuration of an input signal generation circuit in a fifth embodiment. Timing chart showing the operation of the startup trigger circuit in the fifth embodiment. 10. A timing chart showing the operation of the activation trigger circuit in the fifth embodiment. A block diagram showing the configuration of a motor system in a sixth embodiment. An explanatory diagram showing an example of the configuration of a low-pass filter circuit. An explanatory diagram showing another example of the configuration of a low-pass filter circuit. A block diagram showing the configuration of an input signal generation circuit in the sixth embodiment. A block diagram showing the configuration of a lead angle adjustment circuit. A timing chart showing the operation of the lead angle adjustment circuit. A block diagram showing the configuration of an input signal generation circuit in a seventh embodiment. A block diagram showing the configuration of a motor system in an eighth embodiment. A block diagram showing the configuration of a motor system in a ninth embodiment. A block diagram showing the configuration of a motor testing system. A graph showing the drive waveform, measured voltage values, and measured current values ​​of a brushless motor. A flowchart showing the procedure for testing the characteristics of a brushless motor. An explanatory diagram showing an example of a display screen for motor characteristics.

[0008] A. First Embodiment: Figure 1 is a block diagram showing the configuration of a motor system according to an embodiment. This motor system includes a brushless motor 100, a motor drive control device 400, and a DC power supply 500. The DC power supply 500 supplies a DC voltage Ev to a full-bridge circuit in the motor drive control device 400, which directly drives the brushless motor 100. The DC power supply 500 also supplies a voltage obtained by stepping down the DC voltage Ev using a step-down circuit as a power supply voltage for the circuitry of the motor drive control device 400 excluding the full-bridge circuit.

[0009] Brushless motor 100 is a two-phase motor having A-phase coil 102_A and B-phase coil 102_B. However, the present disclosure can be applied to brushless motors with any number of phases, including single-phase and three-phase motors. Brushless motor 100 preferably has a rotor using a ferromagnetic permanent magnet such as a neodymium magnet, and is a high-torque motor with low inductance (few turns) in the electromagnetic coil. In such brushless motors, braking power is generated due to induced voltage even when the motor is in a driving state generating driving force, making the present disclosure particularly effective.

[0010] The brushless motor 100 is provided with magnetic sensors 104_A and 104_B that generate analog electrical angle signals Sin that represent the electrical angle of the brushless motor 100. The analog electrical angle signals Sin have waveforms that resemble the waveforms of back-electromotive force generated by the coils of each phase. The magnetic sensor 104A generates the analog electrical angle signal Sin for the A-phase coil 102_A, and the magnetic sensor 104B generates the analog electrical angle signal Sin for the B-phase coil 102_B. The analog electrical angle signals Sin have sinusoidal waveforms. The magnetic sensors 104_A and 104_B are, for example, linear Hall ICs.

[0011] In this disclosure, circuit symbols with "_A" at the end indicate that the circuit is for the A-phase coil 102_A, and circuit symbols with "_B" at the end indicate that the circuit is for the B-phase coil 102_B. However, when it is not necessary to distinguish between the phases of the electromagnetic coils, symbols without the "_A" or "_B" at the end are used. Furthermore, the letters "_A" or "_B" used to distinguish between the phases of the electromagnetic coils are not added to signal names.

[0012] The motor drive control device 400 generates PWM drive signals VP1 and VP2 for driving the brushless motor 100 and supplies them to both ends of the A-phase coil 102_A. Similar PWM drive signals VP1 and VP2 are also supplied to both ends of the B-phase coil 102_B. However, the PWM drive signals VP1 and VP2 for the B-phase coil 102_B are signals that are 90 degrees out of phase with the PWM drive signals VP1 and VP2 for the A-phase coil 102_A. It is preferable that the PWM drive signals VP1 and VP2 have a PWM frequency of 280 kHz or higher. This point will be discussed later.

[0013] The motor drive control device 400 has a circuit that generates PWM drive signals VP1 and VP2 for the A-phase coil 102_A and a circuit that generates PWM drive signals VP1 and VP2 for the B-phase coil 102_B. The circuit that generates the PWM drive signals VP1 and VP2 for the A-phase coil 102_A includes an input signal generation circuit 410_A, a PWM drive signal generation circuit 420_A, and a low-pass filter circuit 430_A. The circuit that generates the PWM drive signals VP1 and VP2 for the B-phase coil 102_B includes an input signal generation circuit 410_B, a PWM drive signal generation circuit 420_B, and a low-pass filter circuit 430_B.

[0014] The input signal generating circuit 410 is configured to generate input signals Vin1 and Vin2 to the PWM drive signal generating circuit 420 in response to an analog electrical angle signal Sin that indicates the electrical angle of the brushless motor 100 .

[0015] The PWM drive signal generating circuit 420 is configured to generate a first PWM drive signal VP1 that is supplied to a first end of the electromagnetic coil 102 of the brushless motor 100, and to generate a second PWM drive signal VP2 that is supplied to a second end of the electromagnetic coil 102.

[0016] The low-pass filter circuit 430 is intended to remove current ripples from the PWM drive signals VP1 and VP2. Removing the current ripples reduces torque fluctuations in the brushless motor 100. However, the low-pass filter circuit 430 may be omitted.

[0017] The motor drive control device 400 further includes a start instruction signal generating unit 440 , a rotation direction instruction unit 450 , and a rotation speed increase / decrease instruction unit 460 .

[0018] Start instruction signal generating unit 440 performs an operation to start the startup of brushless motor 100. That is, when motor drive control device 400 is powered on, start instruction signal Trg is input from start instruction signal generating unit 440 to input signal generating circuit 410. When start instruction signal Trg is input, input signal generating circuit 410 starts supplying input signals Vin1 and Vin2 to PWM drive signal generating circuit 420, and brushless motor 100 starts rotating.

[0019] The rotation direction indicator 450 is used by the user to indicate the rotation direction of the brushless motor 100. That is, when the user selects either forward or reverse rotation as the rotation direction, the rotation direction indicator 450 inputs a rotation direction indicator signal Rd to the input signal generating circuit 410. When the rotation direction indicator signal Rd is input, the phase of the input signals Vin1 and Vin2 from the input signal generating circuit 410 to the PWM drive signal generating circuit 420 is selected, causing the brushless motor 100 to rotate in the forward or reverse direction. That is, the input signal generating circuit 410 is configured to include a circuit that inverts the waveforms of the first input signal Vin1 and the second input signal Vin2, respectively, or crosses the first input signal Vin1 and the second input signal Vin2, in order to rotate the brushless motor 100 in the forward or reverse direction. Here, "crossing" two signals means swapping the two signals. In the case of a single-phase brushless motor, the direction of rotation can be controlled by an inversion signal (phase conversion by an electrical angle of π), just like in the case of a two-phase brushless motor. In the case of a three-phase brushless motor, the direction of rotation can be controlled to either forward or reverse by switching two of the three phases, U, V, and W.

[0020] If the brushless motor 100 is a three-phase motor having three phase coils, the motor drive control device 400 is configured to include three PWM drive signal generation circuits 420 corresponding to the three phase coils, and an input signal generation circuit 410 that generates three sets of input signals Vin1, Vin2 that are input to the three PWM drive signal generation circuits 420 in response to an analog electrical angle signal Sin that indicates the electrical angle of the brushless motor 100. The input signal generation circuit 410 is configured to include a circuit that switches two sets of input signals Vin1, Vin2 of the three sets of input signals Vin1, Vin2 that are input to the three PWM drive signal generation circuits 420 in order to rotate the brushless motor 100 forward or reverse in response to the rotation direction indication signal Rd. This makes it possible to arbitrarily switch between forward and reverse rotation even in the case of a three-phase motor.

[0021] The rotational speed increase / decrease instruction unit 460 is used by the user to instruct the increase / decrease of torque or the increase / decrease of rotational speed of the brushless motor 100. That is, when the user instructs the increase / decrease of rotational speed, a rotational speed increase / decrease instruction signal Rv is input from the rotational speed increase / decrease instruction unit 460 to the input signal generation circuit 410. The input signal generation circuit 410 increases or decreases the amplitude of the signal in response to the rotational speed increase / decrease instruction signal Rv, and the rotational speed of the brushless motor 100 is set accordingly. The input signal generation circuit 410 may also be configured to include the rotational speed increase / decrease instruction unit 460. Alternatively, if the PWM drive signal generation circuit 420 is configured as a Class D amplifier for audio, the volume control volume of the Class D amplifier may be used as the rotational speed increase / decrease instruction unit 460. The amplitude level of the volume control volume can be used to easily achieve linear increase / decrease adjustment of the rotational speed and torque of the brushless motor 100 over the entire range using the functions of the PWM drive signal generation circuit 420. In other words, brushless motor 100 can be started and operated simply by turning the volume control, just like turning the volume of the power supply voltage, without having to set complex parameters like with a brushed motor.

[0022] FIG. 2 is a graph showing the drive waveforms, voltages, and currents of the brushless motor 100. The brushless motor 100 is in a drive state in which it generates drive force. The A-phase voltage Va and B-phase voltage Vb shown at the top of FIG. 2 represent ideal analog voltage waveforms of the two-phase electromagnetic coil 102. The voltage waveforms of the A-phase voltage Va and B-phase voltage Vb change periodically every cycle Pw. One cycle Pw corresponds to 360 electrical degrees. The phase voltage Vpwm generated by PWM control is a rectangular wave, as shown in the third graph from the top of FIG. 2. The phase voltage Vpwm is a voltage corresponding to the difference between the PWM drive signals VP1 and VP2 applied to both ends of the electromagnetic coil 102. The phase voltage Vpwm shown in the fourth graph from the top of FIG. 2 is an enlarged view of a portion. The two graphs at the bottom of FIG. 2 show an enlarged view of the phase voltage Vpwm and phase current Ipwm generated during one cycle Pe of PWM control.

[0023] Even when brushless motor 100 is in a driving state in which it generates driving force, there are intervals in which the phase current Ipwm has a different sign, as shown in FIG. 2 . In the example of FIG. 2 , driving power is generated in the interval in which phase current Ipwm is positive, and braking power is generated in the interval in which phase current Ipwm is negative. In general, driving power is generated when the phase voltage Vpwm and the phase current Ipwm have the same sign, and braking power is generated when the phase voltage Vpwm and the phase current Ipwm have different signs. The phase current Ipwm when the phase voltage Vpwm and the phase current Ipwm have different signs is called the "braking current." As explained below, the braking current varies significantly depending on the PWM frequency.

[0024] FIG. 3 is a graph showing the difference in braking current depending on the PWM frequency. It shows the change in phase current at four PWM frequencies: 140 KHz, 210 KHz, 280 KHz, and 314 KHz. These graphs are the results of simulating a state in which the same load is applied to the brushless motor 100. The hatched areas correspond to the braking current. From these graphs, it can be seen that the lower the PWM frequency, the larger the braking current, and the higher the PWM frequency, the smaller the braking current.

[0025] FIG. 4 is a graph showing the change in braking current as a function of PWM frequency. The horizontal axis represents the PWM frequency, and the vertical axis represents the braking current. This graph is semi-logarithmic, with the vertical axis representing the logarithmic scale. As can be seen from this graph, a PWM frequency of 280 kHz or higher reduces the braking current to a negligible level. Therefore, a PWM frequency of 280 kHz or higher is preferable. A PWM frequency of 300 kHz or higher is even more preferable. By setting the PWM frequency at 280 kHz or higher or 300 kHz or higher and using phase coils with low resistance and inductance values ​​and fewer turns, it is possible to easily realize high-torque motors that require even higher currents, such as those used in electrified jet engines. Since the braking current is nearly zero at PWM frequencies of 300 kHz or higher, there is no need to increase the PWM frequency excessively; a PWM frequency of 3 MHz or lower is sufficient.

[0026] 5 is a block diagram showing the functions of the input signal generating circuit 410. The input signal generating circuit 410 includes an attenuator 411, an inverted signal generating circuit 412, a signal selecting circuit 413, and an activation trigger circuit 414.

[0027] The attenuator 411 includes an attenuator 11a that attenuates the analog electrical angle signal Sin provided from the magnetic sensor 104 of the brushless motor 100. The analog electrical angle signal Sin is subjected to impedance conversion by the attenuator 411 to determine its maximum amplitude, resulting in a signal of a level suitable for subsequent processing. In the example of FIG. 5 , the signal is adjusted within a range of 0 to the maximum amplitude by a variable resistor 11b, thereby adjusting the rotational speed, including torque. The signal adjusted by the variable resistor 11b is sent to the inverted signal generating circuit 412 via a coupling capacitor 12. The signal from the variable resistor 11b is adjusted in response to a rotational speed increase / decrease instruction signal Rv provided by a rotational speed increase / decrease instruction unit 460. Note that the variable resistor 11b may be configured as the rotational speed increase / decrease instruction unit 460. The attenuator 411 is provided independently in the input signal generation circuit 410A for phase A and the input signal generation circuit 410B for phase B, but the resistance value of the variable resistor 11b is adjusted so that it becomes the same value in conjunction with the resistance value of the variable resistor 11b for phase A and phase B.

[0028] The inverted signal generating circuit 412 generates a first signal V1 proportional to the analog electrical angle signal Sin and a second signal V2 obtained by inverting the first signal V1. In the example shown in FIG. 5, the inverted signal generating circuit 412 has two inverting amplifiers 21 and 22 connected in series, each of which performs inverting amplification using a bias voltage Vref. The output of the second inverting amplifier 22 is the first signal V1 proportional to the analog electrical angle signal Sin. The output of the first inverting amplifier 21 corresponds to the second signal V2 obtained by inverting the first signal V1.

[0029] The signal selection circuit 413 selects one of the first signal V1 and the second signal V2 as the first input signal Vin1 and the other as the second input signal Vin2 in response to the rotation direction indication signal Rd provided by the rotation direction indication unit 450. These input signals Vin1 and Vin2 are input to the PWM drive signal generation circuit 420. This rotation direction indication signal Rd can be used to switch between forward and reverse rotation of the brushless motor 100. The signal selection circuit 413 corresponds to a circuit that inverts the waveforms of the first input signal Vin2 and the second input signal Vin2. The signal selection circuit 413 can also be considered to correspond to a circuit that crosses the waveforms of the first input signal Vin2 and the second input signal Vin2.

[0030] The start trigger circuit 414 starts supplying the input signals Vin1 and Vin2 to the PWM drive signal generation circuit 420 in response to the start instruction signal Trg provided by the start instruction signal generation unit 440, thereby starting operation of the brushless motor 100. In the example shown in FIG. 5 , the start trigger circuit 414 includes a differentiation circuit 41, a flag generation circuit 42, an AND circuit 43, a switch circuit 44, and a resistor 45. The differentiation circuit 41 outputs the differentiation of the output of the coupling capacitor 12. The flag generation circuit 42 generates a flag signal FLG that rises to a high level in response to changes in the output DIFF of the differentiation circuit 41. The AND circuit 43 outputs the logical product of the inverted signal of the flag signal FLG, which is the output of the flag generation circuit 42, and the start instruction signal Trg. The switch circuit 44 turns on / off in response to the output SW of the AND circuit 43. The operation of the start trigger circuit 414 will be described later.

[0031] FIG. 6 is a block diagram showing the functions of the PWM drive signal generation circuit 420. The PWM drive signal generation circuit 420 includes a carrier signal generation circuit 510 that generates a carrier signal Vcr, three comparators 521, 522, and 530, an XOR circuit 540, two signal selection circuits 551 and 552, and a full-bridge circuit 560. The first comparator 521 compares the first input signal Vin1 with the carrier signal Vcr to generate a first comparison signal Vc1. The second comparator 522 compares the second input signal Vin2 with the carrier signal Vcr to generate a second comparison signal Vc2. The third comparator 530 compares the two input signals Vin1 and Vin2 to determine the direction of current flowing through each phase coil 102 of the brushless motor 100 and generates a selection signal SL that switches between positive and negative polarities. This selection signal SL is supplied to the two signal selection circuits 551 and 552. When the selection signal SL is at H level, the signal selection circuit 551 is conductive, and when the selection signal SL is at L level, the signal selection circuit 552 is conductive. The signal selection circuits 551 and 552 in Fig. 6 show a conductive state when the selection signal SL is at H level. Based on the control signals supplied from the two signal selection circuits 551 and 552, the full-bridge circuit 560 generates a PWM drive signal VP1 that is supplied to the positive side of the phase coil 102 and a PWM drive signal VP2 that is supplied to the negative side of the phase coil 102, thereby generating an AC current.

[0032] The XOR circuit 540 generates the original drive signal Vpre by taking the exclusive OR of the first comparison signal Vc1 and the second comparison signal Vc2. When the first input signal Vin1 is greater than the second input signal Vin2, the selection signal SL goes high, and the full-bridge circuit 560 outputs a PWM drive signal VP1 in response to the output signal Vg1 and the high-level signal Vh1 output from the first signal selection circuit 551, causing a positive current to flow. On the other hand, when the first input signal Vin1 is less than the second input signal Vin2, the selection signal SL goes low, and the full-bridge circuit 560 outputs a PWM drive signal VP2 in response to the output signal Vg2 and the high-level signal Vh2 output from the first signal selection circuit 552, causing a negative current to flow. The output signals Vg1, Vg2, Vh1, and Vh2 from the signal selection circuits 551 and 552 are used as gate signals for the four transistors in the full-bridge circuit 560.

[0033] The carrier signal Vcr is a triangular wave or a sawtooth wave. The carrier frequency of the carrier signal Vcr corresponds to the PWM frequency. The PWM drive signal generation circuit 420 is a single class-D power amplifier that supports BTL (Bridged Tied Load) and has a full-bridge circuit 560. However, the PWM drive signal generation circuit 420 may also be configured using two class-D power amplifiers each having a half-bridge circuit.

[0034] FIG. 7 is a timing chart showing the operation of the PWM drive signal generation circuit 420 shown in FIG. 6 . The first comparison signal Vc1 output from the first comparator 521 is a square wave resulting from a comparison between the first input signal Vin1 and the carrier signal Vcr. The second comparison signal Vc2 output from the second comparator 522 is a square wave resulting from a comparison between the second input signal Vin2 and the carrier signal Vcr. The XOR circuit 540 generates the original drive signal Vpre by taking the exclusive OR of the comparison signals Vc1 and Vc2 and supplies this to the first signal selection circuit 551 and the first signal selection circuit 552. When the first input signal Vin1 is greater than the second input signal Vin2, the full-bridge circuit 560 outputs a PWM drive signal VP1 in response to the output signal Vg1 and the H-level signal Vh1 output from the first signal selection circuit 551, causing a positive current to flow. On the other hand, when the first input signal Vin1 is smaller than the second input signal Vin2, the full-bridge circuit 560 outputs a PWM drive signal VP2 in response to the output signal Vg2 output from the first signal selection circuit 552 and the H-level signal Vh2, causing a negative current to flow. The PWM drive signals VP1 and VP2 form the AC voltage of the PWM drive signal Vpwm.

[0035] Fig. 8 is a timing chart showing the operation of the activation trigger circuit 414 shown in Fig. 5. The timing chart shows the on / off state of the power supply to the motor drive control device 400, the analog electrical angle signal Sin, the input Cin to the coupling capacitor 12, the output DIFF of the differentiation circuit 41, the output FLG of the flag generation circuit 42, the output SW of the AND circuit 43, the activation instruction signal Trg, the output Cout of the coupling capacitor 12, and the PWM drive signal Vpwm applied to the electromagnetic coil 102.

[0036] If the coupling capacitor 12 is fully charged when power is supplied to the motor drive control device 400, the output Cout of the coupling capacitor 12 is maintained at a constant voltage. Therefore, even if the analog electrical angle signal Sin is input, its waveform change is not input to the inverted signal generation circuit 412, so the PWM drive signals VP1 and VP2 are not generated and the brushless motor 100 remains stopped. In this stopped state, the output DIFF of the differentiating circuit 41 and the output FLG of the flag generation circuit 42 both remain low. When the motor drive control device 400 is powered on, the start instruction signal Trg rises, and the output SW of the AND circuit 43 rises and is input to the switch circuit 44. As a result, the switch circuit 44 changes from off to on, the coupling capacitor 12 is discharged, the analog electrical angle signal Sin charges the coupling capacitor 12, and a waveform change appears in the output Cout of the coupling capacitor 12. As a result, generation of the PWM drive signals VP1 and VP2 begins and the brushless motor 100 begins to rotate. Preferably, the start instruction signal generating unit 440 is configured to generate the start instruction signal Trg at regular intervals after the power supply to the motor drive control device 400 is turned on. Alternatively, the start instruction signal generating unit 440 may be configured to generate the start instruction signal Trg in response to a start instruction given by the user.

[0037] As described above, in this embodiment, the PWM drive signal generating circuit 420 generates a PWM drive signal at a PWM frequency of 280 KHz or higher, so that the braking current can be reduced to a negligible level.

[0038] B. Second Embodiment: Fig. 9 is a block diagram showing the functions of the input signal generating circuit 410 in the second embodiment. The second embodiment differs from the first embodiment in the following respects, but is otherwise the same as the first embodiment: (1) The attenuator 411a does not have a coupling capacitor 12. (2) An amplifier 415 and a clip circuit 416 are added between the attenuator 411a and the inverted signal generating circuit 412. (3) The startup trigger circuit 414 is omitted.

[0039] In the second embodiment, the coupling capacitor 12 is omitted, so the startup problem described in FIG. 8 does not occur. Therefore, the startup trigger circuit 414 and the startup instruction signal generator 440 can be omitted. In other words, the input signal generation circuit 410 of the second embodiment is configured so that the first input signal Vin1 and the second input signal Vin2 are directly transmitted to the PWM drive signal generation circuit 420 regardless of whether the brushless motor 100 is stopped or operating, because the coupling capacitor 12 is omitted. Furthermore, if the input section of the amplifier 415 is a differential input, the noise level generated between the variable resistor 11b and GND can be suppressed, which has the effect of significantly improving the S / N ratio of the amplified signal Sina. Furthermore, if the output section of the amplifier 415 is a differential output, the inverted signal generation circuit 412 can be omitted.

[0040] The amplifier 415 amplifies the analog electrical angle signal Sin in accordance with a given gain to generate an amplified electrical angle signal Sina. The gain of the amplifier 415 is preferably configured to be switchable among a plurality of gain values ​​in accordance with the level of the rotation speed increase / decrease instruction signal Rv.

[0041] FIG. 10 is a timing chart showing the operation of the clip circuit 416. The clip circuit 416 has a configuration in which two Zener diodes arranged in opposite directions are connected in series between the input terminal and the output terminal of the amplifier 415. The clip circuit 416 has a function of clipping the amplified signal Sina, obtained by amplifying the input signal Sin, at the upper limit value Lim when the amplitude of the amplified signal Sina exceeds the upper limit value Lim. The upper limit value Lim is set, for example, to a value corresponding to the amplitude level at which the duty of the PWM control is 100%. By providing such a clip circuit 416, efficient field-weakening control of the brushless motor 100 can be performed, easily increasing the rotational speed and torque to the load.

[0042] The clipping circuit 416 may be provided in an amplifier within the PWM drive signal generation circuit 420. Specifically, when the PWM drive signal generation circuit 420 is configured with a class-D amplifier, the clipping circuit 416 may be provided in an amplifier that amplifies an input signal input to the class-D amplifier. The class-D amplifier may also be configured to include multiple taps selected in response to the rotation speed increase / decrease command signal Rv as taps for setting an amplification factor for amplifying the input signal input to the class-D amplifier. These taps have a function of setting a resistance value according to the amplification factor. The class-D amplifier may further be configured to include a clipping circuit that clips the amplitude of the amplified signal, obtained by amplifying the input signal with the amplification factor set by the selected tap, at a predetermined upper limit when the amplitude exceeds a predetermined upper limit. These clipping circuits also achieve the same effect as that described with reference to FIG. 10 .

[0043] C. Third Embodiment: Figure 11 is a block diagram showing the configuration of a motor system according to a third embodiment. This motor system includes a brushless motor 100, a motor drive control device 1400, and a DC power supply 1500. The DC power supply 1500 supplies a DC voltage Ev to a full-bridge circuit of the motor drive control device 1400 that directly drives the brushless motor 100. The DC power supply 1500 also supplies a voltage obtained by stepping down the DC voltage Ev using a step-down circuit as a power supply voltage for the circuitry of the motor drive control device 1400 excluding the full-bridge circuit.

[0044] The brushless motor 100 is a two-phase motor having an A-phase coil 102_A and a B-phase coil 102_B. However, the present disclosure is applicable to brushless motors with any number of phases, including single-phase motors and three-phase motors. It is preferable to provide the same number of PWM drive signal generation circuits 1420 shown in FIG. 11 as the number of phases.

[0045] The motor drive control device 1400 has an input signal generation circuit 1410, PWM drive signal generation circuits 1420_A and 1420_B, a start instruction signal generation unit 1440, a rotation direction instruction unit 1450, and a rotation speed increase / decrease instruction unit 1460.

[0046] The PWM drive signal generation circuit 1420_A generates PWM drive signals VP1_A and VP2_A and supplies them to both ends of the A-phase coil 102_A. The PWM drive signal generation circuit 1420_B generates PWM drive signals VP1_B and VP2_B and supplies them to both ends of the B-phase coil 102_B. The PWM drive signals VP1_B and VP2_B for the B-phase coil 102_B are signals that are 90 degrees out of phase with the PWM drive signals VP1_A and VP2_A for the A-phase coil 102_A. The PWM drive signals VP1 and VP2 preferably have a PWM frequency of 280 kHz or higher.

[0047] The input signal generation circuit 1410 is configured to generate input signals Vin1_A and Vin2_A for the PWM drive signal generation circuit 1420_A in response to an analog electrical angle signal Sin_A that indicates the electrical angle of the brushless motor 100, and to generate input signals Vin1_B and Vin2_B for the PWM drive signal generation circuit 1420_B in response to the analog electrical angle signal Sin_B. The waveform change of the first input signal Vin1_A for the A phase is proportional to the waveform change of the analog electrical angle signal Sin_A. The waveform of the second input signal Vin2_A is a waveform obtained by inverting the positive and negative polarities of the first input signal Vin1_A. The same is true for the signals Vin1_B and Vin2_B for the B phase.

[0048] Start instruction signal generating unit 1440 supplies input signal generating circuit 1410 with a start instruction signal Trg for starting the startup of brushless motor 100. When start instruction signal Trg is supplied, input signal generating circuit 1410 starts supplying input signals Vin1 and Vin2 to PWM drive signal generating circuit 1420, and brushless motor 100 starts rotating. The internal configuration and operation of start instruction signal generating unit 1440 will be described later.

[0049] The rotation direction indicator 1450 is used by the user to indicate the rotation direction of the brushless motor 100. That is, when the user selects either forward or reverse rotation as the rotation direction, the rotation direction indicator 1450 inputs a rotation direction indicator signal Rd to the input signal generating circuit 1410. When the rotation direction indicator signal Rd is input, the phase of the input signals Vin1 and Vin2 from the input signal generating circuit 1410 to the PWM drive signal generating circuit 1420 is selected, causing the brushless motor 100 to rotate in the forward or reverse direction. That is, the input signal generating circuit 1410 is configured to include a circuit that inverts the positive and negative polarities of the first input signal Vin1 and the second input signal Vin2, or crosses the first input signal Vin1 and the second input signal Vin2, in order to rotate the brushless motor 100 in the forward or reverse direction. Here, "crossing" two signals means swapping the two signals. In the case of a single-phase brushless motor, the direction of rotation can be controlled by an inversion signal (phase conversion by an electrical angle of π), just like in the case of a two-phase brushless motor. In the case of a three-phase brushless motor, the direction of rotation can be controlled to either forward or reverse by switching two of the three phases, U, V, and W.

[0050] If brushless motor 100 is a three-phase motor having three phase coils, motor drive control device 1400 is configured to include three PWM drive signal generation circuits 1420 corresponding to the three phase coils. Furthermore, input signal generation circuit 1410 is configured to include a circuit that switches two pairs of input signals {Vin1, Vin2} out of the three pairs of input signals {Vin1, Vin2} input to the three PWM drive signal generation circuits 1420 in order to rotate brushless motor 100 forward or reverse in response to rotation direction indication signal Rd. In this way, it is possible to arbitrarily switch between forward and reverse rotation even in the case of a three-phase motor.

[0051] Rotational speed increase / decrease instruction unit 1460 is used by the user to instruct the increase / decrease of torque or the increase / decrease of rotational speed of brushless motor 100. That is, when the user instructs the increase / decrease of rotational speed, rotational speed increase / decrease instruction signal Rv is input from rotational speed increase / decrease instruction unit 1460 to input signal generation circuit 1410. Input signal generation circuit 1410 increases or decreases the amplitude of the signal in response to rotational speed increase / decrease instruction signal Rv, and the rotational speed of brushless motor 100 is set accordingly. Note that input signal generation circuit 1410 may be configured to include rotational speed increase / decrease instruction unit 1460. Alternatively, if PWM drive signal generation circuit 1420 is configured as a Class D amplifier for audio, the volume control volume of the Class D amplifier may be used as rotational speed increase / decrease instruction unit 1460. Depending on the amplitude level of the volume control volume, linear increase / decrease adjustment of the rotational speed and torque of brushless motor 100 over the entire range can be easily achieved using the functions of PWM drive signal generation circuit 1420. In other words, brushless motor 100 can be started and operated simply by turning the volume control, just like turning the volume of the power supply voltage, without having to set complex parameters like with a brushed motor.

[0052] 12 is a block diagram showing the configuration of the input signal generation circuit 1410. The input signal generation circuit 1410 includes a voltage adjustment circuit 1411, a rotation direction switching circuit 1412, an amplitude adjustment circuit 1413, differential amplification units 1414_A and 1414_B, and a startup trigger circuit 1415.

[0053] The voltage adjustment circuit 1411 is an attenuator that adjusts the voltage between GND (maximum negative magnetic pole) and Vs (maximum positive magnetic pole) of the analog electrical angle signals Sin_A and Sin_B provided from the magnetic sensor 104 of the brushless motor 100, and generates input signals Xin_A and Xin_B to the rotation direction switching circuit 1412. The voltages at specific positions PP_A and PP_B in the signal path of the voltage adjustment circuit 1411 change in response to a signal from a start-up trigger circuit 1415. This point will be described later.

[0054] The rotation direction switching circuit 1412 generates output signals Xout_A and Xout_B according to the rotation direction instruction signal Rd provided by the rotation direction instruction unit 1450. When rotating the brushless motor 100 forward, the rotation direction switching circuit 1412 outputs the input signals Xin_A and Xin_B as they are as output signals Xout_A and Xout_B. When rotating the brushless motor 100 in the reverse direction, the rotation direction switching circuit 1412 inverts the positive and negative signs of the input signals Xin_A and Xin_B and outputs them as output signals Xout_A and Xout_B.

[0055] 13 is a block diagram showing the configuration of the rotation direction switching circuit 1412. The rotation direction switching circuit 1412 includes an inverting amplifier circuit 1051, a selection circuit 1052, and a reference voltage setting circuit 1053.

[0056] The inverting amplifier circuit 1051 is composed of an operational amplifier and has the function of inverting the positive and negative polarities of the input signals Xin_A and Xin_B. The selection circuit 1052 selects one of the input signals Xin_A and Xin_B or their inverted signals in response to a rotation direction indication signal Rd provided by the rotation direction indication unit 1450. When rotating the brushless motor 100 forward, the selection circuit 1052 selects the input signals Xin_A and Xin_B and outputs them as output signals Xout_A and Xout_B. When rotating the brushless motor 100 reversely, the selection circuit 1052 selects the inverted signals of the input signals Xin_A and Xin_B and outputs them as output signals Xout_A and Xout_B. The reference voltage setting circuit 1053 adjusts the reference voltage input to the positive input terminal of the operational amplifier so that the inverting amplifier circuit 1051 operates properly.

[0057] 12 generates signals Y_A and Y_B by increasing or decreasing the amplitude of signals Xout_A and Xout_B in accordance with rotation speed increase / decrease instruction signal Rv provided by rotation speed increase / decrease instruction unit 1460. This amplitude adjustment adjusts the rotation speed and torque of brushless motor 100.

[0058] The differential amplifier unit 1414_A is configured to generate a signal Vin1_A having a waveform change proportional to the waveform change of the signal Y_A input to the first input terminal, and a signal Vin2_A having a waveform change obtained by inverting the polarity of the signal Vin1_A. The differential amplifier unit 1414_B is configured similarly.

[0059] FIG. 14 is a block diagram showing the configuration of the differential amplifier unit 1414. The differential amplifier unit 1414 includes a differential amplifier 1061 and an inverting amplifier 1062. The differential amplifier 1061 generates a signal Vin1 having a waveform change proportional to the waveform change of the input signal Y. The inverting amplifier 1062 generates a signal Vin2 having a waveform change obtained by inverting the polarity of the signal Vin1. The first input terminal of the differential amplifier 1061 is connected to the output terminal of the amplitude adjustment circuit 1413 shown in FIG. 12 via a coupling capacitor C1 that provides capacitive coupling. The second input terminal of the differential amplifier 1061 is grounded via a capacitor C2. The differential amplifier 1061 amplifies the difference between the signal Y supplied from the amplitude adjustment circuit 1413 and the ground potential, thereby eliminating noise that occurs at the ground potential.

[0060] 15 is a block diagram showing the configuration of the PWM drive signal generation circuit 1420. The PWM drive signal generation circuit 1420 includes a carrier signal generation circuit 1510 that generates a carrier signal Vcr, two comparators 1521 and 1522, and a full-bridge circuit 1050. The first comparator 1521 compares the first input signal Vin1 with the carrier signal Vcr to generate a first comparison signal Vc1. The second comparator 1522 compares the second input signal Vin2 with the carrier signal Vcr to generate a second comparison signal Vc2. As described above, the second input signal Vin2 is a signal obtained by inverting the first input signal Vin1.

[0061] The full-bridge circuit 1530 is an H-bridge circuit composed of a first p-channel transistor 1531p, a first n-channel transistor 1531n, a second p-channel transistor 1532p, and a second n-channel transistor 1532n. A first comparison signal Vc1 is input to the gate terminals of the first p-channel transistor 1531p and the first n-channel transistor 1531n. A second comparison signal Vc2 is input to the gate terminals of the second p-channel transistor 1532p and the second n-channel transistor 1532n.

[0062] A first node 1531c between the source terminal of the first p-channel transistor 1531p and the drain terminal of the first n-channel transistor 1531n is connected to one end of the electromagnetic coil 102. A first PWM drive signal VP1 having a waveform similar to that of the first comparison signal Vc1 is supplied from the first node 1531c to the electromagnetic coil 102. A second node 1532c between the source terminal of the second p-channel transistor 1532p and the drain terminal of the second n-channel transistor 1532n is connected to the other end of the electromagnetic coil 102. A second PWM drive signal VP2 having a waveform similar to that of the second comparison signal Vc2 is supplied from the second node 1532c to the electromagnetic coil 102.

[0063] The carrier signal Vcr is a triangular wave or a sawtooth wave. One cycle Pcr of the carrier signal Vcr corresponds to the PWM cycle Pe shown in FIG. 2. In this embodiment, the carrier cycle Pcr is constant. The PWM drive signal generation circuit 1420 is a single class-D power amplifier compatible with BTL (Bridged Tied Load) and having a full-bridge circuit 1530. However, the PWM drive signal generation circuit 1420 may also be configured using two class-D power amplifiers each having a half-bridge circuit.

[0064] FIG. 16 is a timing chart showing the operation of the PWM drive signal generation circuit 1420 shown in FIG. 15. The first comparison signal Vc1 output from the first comparator 1521 is a square wave resulting from a comparison between the carrier signal Vcr and the first input signal Vin1, whose waveform changes proportionally to the waveform change of the analog electrical angle signal Sin_A. The second comparison signal Vc2 output from the second comparator 1522 is a square wave resulting from a comparison between the carrier signal Vcr and the second input signal Vin2, which is the inverse of the first input signal Vin1. The PWM drive signals VP1 and VP2 have waveforms similar to those of the comparison signals Vc1 and Vc2. These PWM drive signals VP1 and VP2 form the AC voltage of the PWM drive signal Vpwm.

[0065] When the first comparison signal Vc1 and the second comparison signal Vc2 are both at H level, the power supply potential Ev is applied to both ends of the electromagnetic coil 102, and the potential difference between both ends of the electromagnetic coil 102 is zero. Similarly, when the first comparison signal Vc1 and the second comparison signal Vc2 are both at L level, both ends of the electromagnetic coil 102 are at ground potential, and the potential difference between both ends of the electromagnetic coil 102 is zero. When one of the first comparison signal Vc1 and the second comparison signal Vc2 is at H level and the other is at L level, the power supply potential Ev is applied to one end of the electromagnetic coil 102 and the other end is at ground potential, and the potential difference between both ends of the electromagnetic coil 102 is Ev. As can be seen from these operations, the PWM drive signal Vpwm applied to both ends of the electromagnetic coil 102 has a shape obtained by XORing the first comparison signal Vc1 and the second comparison signal Vc2. Furthermore, if the positive and negative potential differences are taken into consideration, the potential difference applied across the electromagnetic coil 102 is positive when the first comparison signal Vc1 is at H level and the second comparison signal Vc2 is at L level, and is negative when the first comparison signal Vc1 is at L level and the second comparison signal Vc2 is at H level. As can be understood from these explanations, the full bridge circuit 1530 is configured to generate a PWM drive signal Vpwm having a waveform proportional to the waveform obtained by exclusive ORing the first comparison signal Vc1 and the second comparison signal Vc2, and supply this to the electromagnetic coil 102.

[0066] The driving method of generating the PWM driving signal Vpwm by taking the exclusive OR of two comparison signals Vc1 and Vc2 essentially achieves EMI (electromagnetic interference) countermeasures similar to spread spectrum modulation. This can be understood from the waveforms of the signals Vc1, Vc2, and Vpwm shown in FIG. 16. Specifically, the first comparison signal Vc1 and the second comparison signal Vc2 are composed of square waves with frequencies approximately equal to the carrier frequency. Therefore, the power spectrum obtained by frequency analysis of these signals exhibits prominent peaks in the spectral intensity of the carrier frequency. Conventional PWM driving signals also exhibit prominent peaks in the spectral intensity of the carrier frequency. In contrast, the PWM driving signal Vpwm generated in this embodiment corresponds to a signal obtained by taking the exclusive OR of the two comparison signals Vc1 and Vc2. Therefore, the number of edges occurring at frequencies other than the carrier frequency is increased, and the spectral intensities of these frequencies are also high. As a result, the power spectrum of the PWM drive signal Vpwm is leveled overall, making it possible to achieve EMI countermeasures that are essentially similar to spread spectrum modulation, and reducing harmonics generated by PWM drive. In this way, in this embodiment, EMI countermeasures that are essentially similar to spread spectrum modulation can be achieved without providing a frequency modulation unit that modulates the PWM frequency, making it possible to simplify the circuit configuration of the PWM drive signal generation circuit 1420.

[0067] 12 starts supplying input signals Vin1 and Vin2 to a PWM drive signal generation circuit 1420 in response to a start instruction signal Trg provided from a start instruction signal generation unit 1440, thereby starting operation of the brushless motor 100. The start trigger circuit 1415 has a rotation flag generation circuit 1041, an oscillation circuit 1042, an AND circuit 1043, and switch circuits 1044_A and 1044_B.

[0068] The rotation flag generation circuit 1041 generates a rotation flag FLG indicating whether the brushless motor 100 is rotating in response to the electrical angle signals Sin_A and Sin_B. In this embodiment, the rotation flag FLG is maintained at a high level when the brushless motor 100 is stopped and drops to a low level when the brushless motor 100 is rotating. Upon receiving the start instruction signal Trg, the oscillator circuit 1042 periodically generates a pulse signal PLS. The AND circuit 1043 generates a start signal SW indicating that the pulse signal PLS was generated while the brushless motor 100 was stopped by calculating the logical product of the rotation flag FLG and the pulse signal PLS. Another logic circuit may be used instead of the AND circuit 1043. This logic circuit is configured to perform a logical operation on the rotation flag FLG and the pulse signal PLS to generate the start signal SW indicating that the pulse signal PLS was generated while the brushless motor 100 was stopped. The switch circuits 1044_A and 1044_B are turned on / off in response to the start signal SW. That is, when the activation signal SW rises to the H level in response to the activation instruction signal Trg, the switch circuits 1044_A and 1044_B are switched from OFF to ON, and a predetermined voltage Vs / 2 is applied to the specific positions PP_A and PP_B of the voltage adjustment circuit 1411. That is, the voltage levels of the specific positions PP_A and PP_B are forcibly set to the predetermined voltage Vs / 2. The voltage Vs / 2 is, for example, half the maximum voltage Vs of the analog electrical angle signal Sin. The switch circuits 1044_A and 1044_B function as signal level change circuits that change the signal levels at the specific positions PP_A and PP_B.

[0069] FIG. 17 is a block diagram showing the configuration of the rotation flag generation circuit 1041. The rotation flag generation circuit 1041 includes coupling capacitors 1031_A and 1031_B, an integrating circuit 1032 including a capacitor 1033, and a comparator 1034 configured with an operational amplifier. The coupling capacitors 1031_A and 1031_B receive the analog electrical angle signals Sin_A and Sin_B and pass their fluctuation components (AC components). The fluctuation components of the analog electrical angle signals Sin_A and Sin_B are integrated by the integrating circuit 1032 to charge the capacitor 1033. The output voltage of the capacitor 1033 is input to the negative input terminal of the comparator 1034. A preset reference voltage is supplied to the positive input terminal of the comparator 1034. When brushless motor 100 is not rotating, the output voltage of capacitor 1033 is lower than the reference voltage of comparator 1034, and therefore the rotation flag FLG output from comparator 1034 is at H level. On the other hand, when brushless motor 100 is rotating, the output voltage of capacitor 1033 becomes higher than the reference voltage, and therefore the rotation flag FLG output from comparator 1034 drops from H level to L level. In this way, rotation flag generation circuit 1041 integrates the fluctuation components of analog electrical angle signals Sin_A and Sin_B corresponding to the rotation of brushless motor 100 and compares the integration result with the reference voltage to generate rotation flag FLG, so that rotation flag FLG can be generated using a simple circuit configuration.

[0070] 18 is a timing chart showing the operation of the activation trigger circuit 1415. Here, the activation instruction signal Trg, the analog electrical angle signal Sin, the input signal Xin of the rotation direction switching circuit 1412, the rotation flag FLG, the pulse signal PLS, the activation signal SW, and the PWM drive signal Vpwm applied to the electromagnetic coil 102 are shown.

[0071] When the start instruction signal Trg rises from low to high in response to a user start instruction, if the coupling capacitor C1 shown in FIG. 12 is fully charged, the output of the coupling capacitor C1 is maintained at a constant voltage. In this case, even if the analog electrical angle signal Sin is input, its waveform change is not input to the differential amplifier unit 1414. Therefore, the PWM drive signals VP1 and VP2 are not generated, and the brushless motor 100 remains stopped. In this stopped state, the rotation flag FLG remains high. When the pulse signal PLS is generated in response to the start instruction signal Trg, the start signal SW rises to high in response, fluctuating the voltage of the input signal Xin to the rotation direction switching circuit 1412. This voltage fluctuation is achieved by forcibly setting the voltages at the specific positions PP_A and PP_B shown in FIG. 12 to a predetermined voltage Vs / 2. As a result, generation of the PWM drive signals VP1 and VP2 begins, and the brushless motor 100 begins rotating. The specific positions at which the voltage is varied are not limited to the positions PP_A and PP_B shown in FIG. 12, but may be other positions on the signal path located before the coupling capacitor C1.

[0072] As described above, in the third embodiment, the PWM drive signal generation circuit 1420 generates a PWM drive signal at a PWM frequency of 280 KHz or higher, thereby reducing the braking current to a negligible level. Furthermore, the full-bridge circuit 1530 can be used to achieve EMI countermeasures similar to those achieved by spread spectrum modulation, without providing a modulation unit for modulating the PWM frequency. Furthermore, the brushless motor 100 can be started in response to the start instruction signal Trg.

[0073] D. Fourth Embodiment: FIG. 19 is a block diagram showing the configuration of an input signal generation circuit 1410 according to the fourth embodiment. The input signal generation circuit 1410 of the fourth embodiment is identical to that of the third embodiment, except that the switch circuits 1044_A and 1044_B of the third embodiment shown in FIG. 12 are omitted and a crossover circuit 1045 is added. The crossover circuit 1045 is provided in a signal path between a voltage adjustment circuit 1411 and a rotation direction switching circuit 1412. The voltage-adjusted analog electrical angle signals Sin_A and Sin_B are input to the crossover circuit 1045. In response to an activation signal SW, the crossover circuit 1045 can be in one of two states: a first state S1 in which the analog electrical angle signals Sin_A and Sin_B pass through as is, or a second state S2 in which the analog electrical angle signals Sin_A and Sin_B are crossed. That is, when the start signal SW is at L level, the crossover circuit 1045 is in the first state S1, where the analog electrical angle signals Sin_A and Sin_B are passed through as they are and output as signals Xin_A and Xin_B. When the start signal SW is at H level, the crossover circuit 1045 is in the second state S2, where the analog electrical angle signals Sin_A and Sin_B are crossed and output as signals Xin_A and Xin_B.

[0074] FIG. 20 is a timing chart showing the operation of the activation trigger circuit 1415 in the fourth embodiment. Here, the A-phase analog electrical angle signal Sin_A and the B-phase analog electrical angle signal Sin_B are depicted separately. Assume that, during a stop, the voltage level of the A-phase analog electrical angle signal Sin_A is greater than Vs / 2 and the voltage level of the B-phase analog electrical angle signal Sin_B is less than Vs / 2. When the activation signal SW rises to the H level, the crossover circuit 1045 crosses the analog electrical angle signals Sin_A and Sin_B, changing the voltage levels of the signals Xin_A and Xin_B. As a result, generation of the PWM drive signals VP1 and VP2 begins, and the brushless motor 100 starts rotating.

[0075] The intersection circuit 1045 functions as a signal level change circuit that changes the signal level at a specific position in the signal path upstream of the coupling capacitor C1. The intersection circuit 1045 is not limited to being located between the voltage adjustment circuit 1411 and the rotation direction switching circuit 1412, and may be located at another position in the signal path upstream of the coupling capacitor C1. The fourth embodiment also achieves substantially the same effects as the third embodiment.

[0076] E. Fifth Embodiment: Figure 21 is a block diagram showing the configuration of an input signal generation circuit 1410 according to a fifth embodiment. The input signal generation circuit 1410 of the fifth embodiment is identical to that of the third embodiment, except that the switch circuits 1044_A and 1044_B of the third embodiment shown in Figure 12 are omitted and a voltage change circuit 1046 is added. The voltage change circuit 1046 has a function of changing the voltage at specific positions PP_A and PP_B in the signal path between the voltage adjustment circuit 1411 and the rotation direction switching circuit 1412 to either the maximum voltage Vs of the electrical angle signal Sin or ground potential.

[0077] The voltage change circuit 1046 includes a comparison circuit 1081, a voltage selection circuit 1082, and a switch circuit 1083. The comparison circuit 1081 generates comparison signals SEL_A and SEL_B by comparing the voltage levels of the analog electrical angle signals Sin_A and Sin_B with a threshold voltage Vs / 2, which corresponds to half the maximum voltage Vs of the analog electrical angle signals Sin_A and Sin_B. The comparison circuit 1081 sets the comparison signal SEL_A to an H level when the voltage level of the A-phase analog electrical angle signal Sin_A is less than the threshold voltage Vs / 2, and sets the comparison signal SEL_A to an L level when the voltage level is equal to or greater than the threshold voltage Vs / 2. The same applies to the B-phase analog electrical angle signal.

[0078] When the comparison signal SEL_A is at H level, the voltage selection circuit 1082 selects the maximum voltage Vs. In this state, when the activation signal SW becomes H level and the switch circuit 1083 turns on, the voltage at the specific position PP_A is forcibly set to the maximum voltage Vs. On the other hand, when the comparison signal SEL_A is at L level, the voltage selection circuit 1082 selects the ground potential. In this state, when the activation signal SW becomes H level and the switch circuit 1083 turns on, the voltage at the specific position PP_A is forcibly set to the ground potential. The same is true for the B phase.

[0079] FIG. 22 is a timing chart showing the operation of the activation trigger circuit 1415 in the fifth embodiment. This diagram shows the operation when the voltage level of the analog electrical angle signal Sin at the time of stopping is less than the threshold voltage Vs / 2. When the activation signal SW rises to the H level, the voltage level of the signal Xin changes to the maximum voltage Vs. As a result, generation of the PWM drive signals VP1 and VP2 begins, and the brushless motor 100 starts to rotate.

[0080] 23 shows the operation when the voltage level of the analog electrical angle signal Sin at the time of stopping is equal to or higher than the threshold voltage Vs / 2. When the start signal SW rises to the H level, the voltage level of the signal Xin changes to the ground potential. As a result, generation of the PWM drive signals VP1 and VP2 begins, and the brushless motor 100 starts rotating.

[0081] The voltage change circuit 1046 functions as a signal level change circuit that changes the signal level at a specific position in the signal path upstream of the coupling capacitor C1. The voltage change circuit 1046 is not limited to being located between the voltage adjustment circuit 1411 and the rotation direction switching circuit 1412, and may be provided at another position in the signal path upstream of the coupling capacitor C1. The fifth embodiment also achieves substantially the same effects as the third embodiment.

[0082] Considering the configuration and operation of the startup trigger circuit 1415 in the third to fifth embodiments described above, it can be understood that the startup trigger circuit 1415 is preferably configured to change the signal level at a specific position in the signal path before the coupling capacitor C1 in accordance with the startup instruction signal Trg.

[0083] F. Sixth Embodiment: Figure 24 is a block diagram showing the configuration of a motor system according to a sixth embodiment. A motor drive control device 1400 according to the sixth embodiment has low-pass filter circuits 1430_A and 1430_B added between the PWM drive signal generation circuits 1420_A and 1420_B and the brushless motor 100 of the third embodiment shown in Figure 11, but the other configurations are the same as those of the third embodiment.

[0084] When PWM drive signals VP1_A and VP2_A are input to the low-pass filter circuit 1430_A for the A phase, sinusoidal analog drive voltages Vout1_A and Vout2_A are output from the low-pass filter circuit 1430_A and applied to the coil 102_A of the brushless motor 100. The same applies to the B phase.

[0085] 25 is an explanatory diagram showing an example of the internal configuration of the low-pass filter circuit 1430. The low-pass filter circuit 1430 includes a choke coil 1431 and an integrating circuit 1432. When the PWM drive signal generating circuit 1420 generates a PWM drive signal at a PWM frequency of 280 KHz or higher, if the choke coil 1431 is formed using ordinary magnet wire, the impedance of the choke coil 1431 may become excessively high due to the skin effect. Therefore, it is preferable to form the choke coil 1431 using an electric wire made by braiding thin wires, such as a Litz wire.

[0086] 26 is an explanatory diagram showing another example of the internal configuration of the low-pass filter circuit 1430. In this example, the choke coil 1431 is configured as a common mode choke coil. Use of a common mode choke coil can efficiently reduce high frequency components.

[0087] The low-pass filter circuits 1430_A and 1430_B function as choke coils, thereby reducing iron loss due to harmonic components of the PWM drive signals VP1 and VP2. However, when the low-pass filter circuits 1430_A and 1430_B are used, a phenomenon occurs in which the phase of the phase current flowing through the coils 102_A and 102_B lags behind the phase of the induced voltage. When a phase lag occurs in the phase current, the power factor decreases, resulting in a decrease in efficiency. Therefore, in the sixth embodiment, advance angle adjustment is performed as described below.

[0088] Fig. 27 is a block diagram showing the configuration of an input signal generation circuit 1410 according to the sixth embodiment. The input signal generation circuit 1410 according to the sixth embodiment is configured such that a lead angle adjustment circuit 1416 is added between the rotation direction switching circuit 1412 and the amplitude adjustment circuit 1413 of the third embodiment shown in Fig. 12, and the other configurations are substantially the same as those of the third embodiment.

[0089] The lead angle adjustment circuit 1416 performs lead angle adjustment to advance the phases of the signals Xout_A and Xout_B by the lead angle adjustment amount θd, respectively, in accordance with the lead angle adjustment amount θd provided from the outside, thereby generating signals Qout_A and Qout_B. The generated signals Qout_A and Qout_B become input signals to the amplitude adjustment circuit 1413. As a result, the phases of the phase currents and induced voltages in the coils 102_A and 102_B of the brushless motor 100 can be matched. The signals Qout_A and Qout_B generated by the lead angle adjustment circuit 1416 are also referred to as "adjusted electrical angle signals."

[0090] 28 is a block diagram showing the configuration of the lead angle adjustment circuit 1416. The lead angle adjustment circuit 1416 includes an AD converter 1071, a phase adjustment unit 1072, an electrical angle conversion unit 1073, a waveform conversion unit 1074, a waveform data table 1075, and a DA converter 1076. The AD converter 1071 digitizes the analog signals Xout_A and Xout_B and converts them into digital signals Dout_A and Dout_B. The phase adjustment unit 1072 generates signals Pout_A and Pout_B by adjusting the phases of the digital signals Dout_A and Dout_B in accordance with the lead angle adjustment amount θd. The electrical angle conversion unit 1073 calculates electrical angles θ_A and θ_B in accordance with the signals Pout_A and Pout_B. The waveform converter 1074 reads waveform data Ddac_A and Ddac_B corresponding to the electrical angles θ_A and θ_B from a waveform data table 1075 and generates the waveform data Ddac_A and Ddac_B. The "waveform data" is multi-level data representing the waveforms of the induced voltages generated in the coils 102_A and 102_B in response to the rotation of the rotor. The waveform data stored in the waveform data table 1075 can be arbitrarily set by an external circuit such as the CPU 1077. The waveform data Ddac_A and Ddac_B are converted by a DA converter 1076 into adjusted electrical angle signals Qout_A and Qout_B, which are analog signals. These adjusted electrical angle signals Qout_A and Qout_B are input to the amplitude adjustment circuit 1413 shown in FIG. 27 .

[0091] 29 is a timing chart showing the operation of the lead angle adjustment circuit 1416. Illustrated here are the clock signal CLK, the input signal Dout and output signal Pout to the phase adjustment unit 1072, the output signal Ddac of the waveform conversion unit 1074, the output signal Qout of the DA converter 1076, and the phase current Qcoil in the electromagnetic coil 102 of the brushless motor 100. One period Pw of the input signal Dout to the phase adjustment unit 1072 corresponds to 360 electrical degrees.

[0092] The phase adjustment unit 1072 generates the output signal Pout by advancing the phase of the input signal Dout by the lead angle adjustment amount θd. The minimum adjustment width in the phase adjustment unit 1072 is one cycle of the clock signal CLK. The waveform data Ddac generated by the waveform conversion unit 1074 is multi-tone data representing an induced voltage waveform corresponding to the signal Pout after lead angle adjustment. The output signal Qout of the DA converter 1076 is the result of converting the waveform data Ddac into an analog signal. The phase of the phase current Qcoil in the electromagnetic coil 102 of the brushless motor 100 is delayed by the low-pass filter circuit 1430 shown in FIG. 24, so that it approximately matches the phase of the induced voltage. By performing this lead angle adjustment, the phases of the phase current and the induced voltage in the coils 102_A and 102_B of the brushless motor 100 can be matched, thereby improving motor efficiency.

[0093] As described above, in the sixth embodiment, iron loss due to harmonic components of the PWM drive signal can be reduced by using the low-pass filter circuit 1430. Furthermore, because the lead angle adjustment circuit 1416 is used to perform lead angle adjustment, the reduction in motor efficiency caused by using the low-pass filter circuit 1430 can be mitigated.

[0094] G. Seventh Embodiment: Figure 30 is a block diagram showing the configuration of an input signal generation circuit 1410 in a seventh embodiment. The input signal generation circuit 1410 in the seventh embodiment differs from the input signal generation circuit 1410 in the sixth embodiment shown in Figure 27 in the following respects, with the remaining configuration being the same as that of the sixth embodiment. (1) Digital electrical angle signals Din_A and Din_B are supplied from the brushless motor 100 instead of analog electrical angle signals Sin_A and Sin_B. (2) The startup trigger circuit 1415 is omitted. (3) The coupling capacitor C1 is omitted.

[0095] In the seventh embodiment, digital electrical angle signals Din_A and Din_B are supplied from the brushless motor 100, and therefore the electrical angle signals Dout_A and Dout_B input from the rotation direction switching circuit 1412 to the lead angle adjustment circuit 1416 are digital signals. The lead angle adjustment circuit 1416 of the seventh embodiment has a configuration in which the AD converter 1071 is omitted from the lead angle adjustment circuit 1416 of the sixth embodiment shown in FIG.

[0096] The seventh embodiment also achieves substantially the same effects as the sixth embodiment. In the seventh embodiment, a digital electrical angle signal Din is input to an input signal generation circuit 1410, and after switching the rotation direction and adjusting the lead angle, an amplitude adjustment circuit 1413 adjusts the amplitude using the clamp potential of a differential amplifier unit 1414 and the same potential as an offset to generate an analog signal Y. Because the analog signal Y generated using the digital electrical angle signal Din is input directly to the PWM drive signal generation circuit 1420 without using a coupling capacitor C1, the brushless motor 100 can be started even if the start trigger circuit 1415 described in the third to sixth embodiments is omitted.

[0097] H. Eighth Embodiment: Figure 31 is a block diagram showing the configuration of a motor system according to the eighth embodiment. This motor system includes a brushless motor 100 and a motor drive control device 1600.

[0098] The brushless motor 100 includes an A-phase coil 102_A, a B-phase coil 102_B, an electrical angle detection unit 104, and a phase current detection unit 106. The electrical angle detection unit 104 generates digital electrical angle signals Din_A and Din_B representing the electrical angles of the A-phase and B-phase. The phase current detection unit 106 generates digital phase current signals Dis_A and Dis_B representing the phase currents of the A-phase and B-phase.

[0099] The motor drive control device 1600 includes a digital control unit 1610 formed by a digital circuit and an analog control unit 1620 formed by an analog circuit.

[0100] The digital control unit 1610 includes a feedback control unit 1611, a DA converter 1612, a CPU 1613, and a signal receiving unit 1614. The signal receiving unit 1614 receives the digital electrical angle signals Din_A and Din_B and the digital phase current signals Dis_A and Dis_B. A control command input unit 1615 for inputting control commands such as a speed command and a position command is connected to the digital control unit 1610.

[0101] The feedback control unit 1611 has a function of executing feedback control of the brushless motor 100 in accordance with the digital electrical angle signals Din_A and Din_B and the digital phase current signals Dis_A and Dis_B. As feedback control, one or more of rotation speed control, torque control (current control), position control, etc. can be executed. The feedback control unit 1611 can be configured to include the rotation direction switching circuit 1412, lead angle adjustment circuit 1416, and waveform conversion circuit 1417 shown in FIG. 29 .

[0102] The DA converter 1612 converts the digital signals Ddac_A and Ddac_B generated by the feedback control unit 1611 into analog signals Qout_A and Qout_B. The CPU 1613 supplies control commands such as speed commands and position commands input from a control command input unit 1615 to the feedback control unit 1611. The signal receiving unit 1614 receives the digital electrical angle signals Din_A and Din_B and the digital phase current signals Dis_A and Dis_B and supplies them to the feedback control unit 1611. The signal receiving unit 1614 is connected by wire to the electrical angle detection unit 104 and the phase current detection unit 106 of the brushless motor 100. The feedback control unit 1611 can calculate the rotation speed of the brushless motor 100 from the digital electrical angle signals Din_A and Din_B. Alternatively, a rotation speed signal may be received from a sensor that detects the rotation speed of the brushless motor 100.

[0103] The analog control unit 1620 has an amplitude adjustment circuit 1621, differential amplification units 1622_A and 1622_B, PWM drive signal generation circuits 1623_A and 1623_B, and low-pass filter circuits 1624_A and 1624_B. The amplitude adjustment circuit 1621 and differential amplification units 1622_A and 1622_B are the same as the amplitude adjustment circuit 1413 and differential amplification units 1414_A and 1414_B, respectively, shown in Figure 30. The PWM drive signal generation circuits 1623_A and 1623_B and low-pass filter circuits 1624_A and 1624_B are the same as the PWM drive signal generation circuits 1420_A and 1420_B and low-pass filter circuits 1430_A and 1430_B, respectively, shown in Figure 24.

[0104] The amplitude adjustment circuit 1621 may be fixed at a 100% adjustment state (maximum amplitude state), and feedback control such as speed control and current control may be performed by the digital control unit 1610. The amplitude adjustment circuit 1621 may also be used to adjust the response time of feedback control. However, if these functions are not used, the amplitude adjustment circuit 1621 may be omitted.

[0105] By configuring the motor drive control device 1600 with a digital control unit 1610 and an analog control unit 1620, it is possible to perform highly accurate feedback control with the digital control unit 1610 while performing motor control with less loss and electromagnetic noise with the analog control unit 1620.

[0106] I. Ninth Embodiment: Figure 32 is a block diagram showing the configuration of a motor system according to a ninth embodiment. A motor drive control device 1600 according to the ninth embodiment has the same configuration as the eighth embodiment, except that the signal receiving unit 1614 of the eighth embodiment shown in Figure 31 is replaced with one that performs wireless communication, and a wireless communication unit 108 is added to the brushless motor 100.

[0107] The signal receiving unit 1614 of the motor drive control device 1600 is wirelessly connected to the control command input unit 1615 and the wireless communication unit 108 of the brushless motor 100. For example, IP (Internet Protocol) wireless communication can be used as the wireless communication. The motor drive control device 1600 can receive the rotation speed and phase current from the brushless motor 100 using wireless communication. The motor drive control device 1600 can also receive feedback control commands from the control command input unit 1615 using wireless communication. As a result, it is possible to omit wiring, freeing the system from complex wiring and reducing production costs.

[0108] J. Brushless Motor Characteristics Test: Figure 33 is a block diagram showing the configuration of a motor testing system. This motor testing system is used to test the characteristics of a brushless motor 100, and includes a motor testing device 200 and a characteristics testing device 300.

[0109] Brushless motor 100 is connected to motor drive control device 400. DC voltage Ev is supplied to motor drive control device 400 from DC power supply 500. An ammeter 151 that measures the coil current of the electromagnetic coil and a voltmeter 161 that measures the coil voltage of the electromagnetic coil are provided on the coil connection wiring between motor drive control device 400 and brushless motor 100.

[0110] The motor testing device 200 includes a first coupling 211, a torque meter 220, a second coupling 212, an electric brake 230, an AC / DC conversion unit 240, a DC load unit 250, and a measurement value collection unit 260. The mechanical connection structure including the first coupling 211, the torque meter 220, the second coupling 212, and the electric brake 230 is referred to as a test connection structure 270.

[0111] The rotating shaft 110 of the brushless motor 100 and the first rotating shaft 221 of the torque meter 220 are connected by a first coupling 211. The torque meter 220 has a first rotating shaft 221 and a second rotating shaft 222 and measures the torque T between the first rotating shaft 221 and the second rotating shaft 222. The torque meter 220 is preferably configured to further measure the rotation speed Nm of the rotating shafts 221 and 222. Instead of measuring the rotation speed Nm with the torque meter 220, the rotation speed Nm may be measured with high accuracy based on a clock counter value in a sensor signal using a magnetic sensor 104 provided in the brushless motor 100. The second rotating shaft 222 of the torque meter 220 and the rotating shaft 232 of the electric brake 230 are connected by a second coupling 212. The electric brake 230 has a coreless motor structure with low iron loss (cogging loss, hysteresis loss, etc.). The electric brake 230 is preferably configured as, for example, a two-phase or three-phase brushless motor. In this embodiment, the electric brake 230 has a magnetic sensor 234 that measures the rotational position of the rotor. In this embodiment, the magnetic sensor 234 is a sensor that is fixed to the stator and measures the magnetic flux density of a permanent magnet provided in the rotor. The magnetic sensor 234 is configured, for example, by a Hall IC. However, the magnetic sensor 234 can be omitted.

[0112] The AC / DC converter 240 is electrically connected to the coils of multiple phases of the electric brake 230, and converts the AC induced voltage Vi generated in the coils into a DC voltage Vd by full-wave rectification. The DC load 250 is electrically connected to the AC / DC converter 240, and is subjected to constant current load control by the DC voltage Vd, thereby subjecting the electric brake 230 to torque control.

[0113] The measurement value collection unit 260 collects the measurement value Es of the coil voltage measured by the voltmeter 161, the measurement value Is of the coil current measured by the ammeter 151, and the torque T and rotation speed Nm measured by the torque meter 220 in synchronization with the analog electrical angle signal Sin, and transfers them to the characteristic test device 300.

[0114] In this disclosure, regardless of whether brushless motor 100 is a two-phase motor or a three-phase motor, a phase voltage measurement value is used as the coil voltage measurement value Es, and a phase current measurement value is used as the coil current measurement value Is. For example, if brushless motor 100 is a three-phase motor and line voltage is measured, the phase voltage value obtained by multiplying the measured line voltage value by 1 / √3 is used as the coil voltage measurement value Es. Similarly, if brushless motor 100 is a three-phase motor and line current is measured, the phase current value obtained by multiplying the measured line current value by 1 / √3 is used as the coil current measurement value Is. In this disclosure, regardless of the number of phases of the motor, the phase voltage of a coil for one phase is referred to as the "coil voltage." Similarly, the phase current of a coil for one phase is referred to as the "coil current."

[0115] The characteristic test apparatus 300 includes a measurement value acquisition unit 310, a characteristic calculation unit 320, and a characteristic display unit 330. The characteristic test apparatus 300 also has the function of controlling each unit of the motor testing apparatus 200. The measurement value acquisition unit 310 acquires measurement values, including the measurement values ​​Es and Is of the phase voltage and phase current of the brushless motor 100, from the measurement value collection unit 260. The characteristic calculation unit 320 calculates the characteristics of the brushless motor 100 using the measurement values ​​Es and Is of the phase voltage and phase current. The characteristic display unit 330 displays the calculated characteristics of the brushless motor 100 on a display screen. In this embodiment, the characteristic calculation unit 320 calculates the apparent power and power factor of the brushless motor 100. The characteristic test apparatus 300 can be realized, for example, by a personal computer. The functions of the characteristic test apparatus 300 are realized by a processor executing a computer program stored in the memory of the characteristic test apparatus 300.

[0116] Figure 34 is a graph showing the drive waveform, voltage measurement Es[j], and current measurement Is[j] of brushless motor 100. In Figure 34, the names of phase voltage Vpwm and phase current Ipwm in Figure 2 have been changed to voltage measurement Es[j] and current measurement Is[j], and the content of each signal is the same as in Figure 2. The dashed dotted line indicates measurement timing j, i.e., the timing of sampling.

[0117] In the following, we will first explain the conventional method for calculating motor characteristics. In this specification, the conventional method for calculating motor characteristics is referred to as the "conventional power calculation method." In the terms used below, the prefix "conventional" means that it is used in the conventional power calculation method.

[0118] <Method for Calculating Conventional Power of Motor Characteristics> The conventional active power Pc of each phase of brushless motor 100 is calculated as follows: Pc = SQRT{ΣPe[j]^2 / M} ...(q1) Pe[j] = Ec[j] × Ic[j] ...(q2) Here, SQRT{} indicates the operation to find the square root in the parentheses, Σ indicates the operation of adding from 1 to M for j, "^2" indicates the operation of squaring, Ec[j] is the conventional voltage value, and Ic[j] is the conventional current value. The conventional voltage value Ec[j] and the conventional current value Ic[j] are equal to the measured voltage value Es[j] of the phase voltage and the measured current value Is[j] of the phase current, respectively.

[0119] In this way, the conventional active power Pc can be calculated by multiplying the conventional voltage value Ec[j] by the conventional current value Ic[j] to obtain the active power value Pe[j], and then calculating the root mean square SQRT{ΣPe[j]^2 / M} of the active power values ​​Pe[j] obtained at M measurement timings.

[0120] The conventional apparent power Sc of brushless motor 100 is calculated for each phase as follows: Sc = Ec_rms·Ic_rms ... (q3) Ec_rms = SQRT(ΣEc[j]^2 / M) ... (q4) Ic_rms = SQRT(ΣIc[j]^2 / M) ... (q5) In this way, the conventional apparent power Sc can be calculated by multiplying the root mean square Ec_rms of the conventional voltage values ​​Ec[j] obtained at M measurement timings j by the root mean square Ic_rms of the conventional current values ​​Ic[j] obtained at M measurement timings j.

[0121] The conventional power factor ηc is calculated by dividing the conventional effective power Pc by the conventional apparent power Sc as follows: ηc = Pc / Sc ...(q6)

[0122] 35 is a flowchart showing the procedure for a characteristic test of brushless motor 100. This characteristic test is preferably carried out while brushless motor 100 is rotating at a constant rotation speed Nm and a constant torque T.

[0123] The following parameters are used in the process of Figure 35. The prefix "driving" indicates that the parameter is related to driving power, and the prefix "braking" indicates that the parameter is related to braking power. N: The number of phase voltage periods Pw for which phase voltage and phase current measurements are performed, and is an integer equal to or greater than 1. M: The total number of measurement timings for phase voltage and phase current, and is an integer greater than N. j: An ordinal number indicating the measurement timing, and is an integer between 1 and M. jA: An ordinal number indicating the detection timing of driving power. Ma: The total number of detection timings jA for driving power. jN: An ordinal number indicating the detection timing of braking power. Mn: The total number of detection timings jN for braking power. Es[j]: The measured voltage value of the phase voltage measured at timing j. Is[j]: The measured current value of the phase current measured at timing j. Ec[j]: A conventional voltage value that is a conventional voltage value at timing j. Ic[j]: A conventional current value that is a conventional current value at timing j. Ea[jA]: Drive voltage value, which is the voltage value of the drive power at timing jA. Ia[jA]: Drive current value, which is the current value of the drive power at timing jA. En[jN]: Braking voltage value, which is the voltage value of the braking power at timing jN. In[jN]: Braking current value, which is the current value of the braking power at timing jN.

[0124] In step S10, the parameter j, which is an ordinal number, is initialized to 1, the parameters jA and jN are each initialized to 0, and the other parameters described above are also initialized. In this embodiment, the number N of phase voltage periods for which measurements of the phase voltage and phase current are performed is assumed to be equal to 1.

[0125] In step S11, the measurement value acquisition unit 310 acquires the voltage measurement value Es[j] and the current measurement value Is[j] measured at measurement timing j.

[0126] In step S12, the conventional voltage value Ec[j] is determined to be equal to the measured voltage value Es[j], and the conventional current value Ic[j] is determined to be equal to the measured current value Is[j]. The conventional voltage value Ec[j] and the conventional current value Ic[j] are values ​​used in the conventional power calculation method according to the above equations (q1) to (q6). Step S12 may be omitted.

[0127] In step S13, the characteristics calculation unit 320 determines whether the sign of the measured voltage Es[j] is the same as the sign of the measured current Is[j]. This determination can be made by applying an XNOR or XOR logical operation to the signs of the measured voltage Es[j] and the measured current Is[j]. If the signs of the measured voltage Es[j] and the measured current Is[j] are the same, it is assumed that drive power is being generated, and steps S14 and S15 are executed. In step S14, the detection timing jA of the drive power is incremented by one. In step S15, it is determined that the drive voltage value Ea[jA] is equal to the measured voltage Es[j], and the drive current value Ia[jA] is equal to the measured current Is[j].

[0128] On the other hand, if the positive / negative signs of the measured voltage Es[j] and the measured current Is[j] are different, it is assumed that braking power is being generated, and the processes of steps S16 and S17 are executed. In step S16, the detection timing jN of the braking power is incremented by 1. In step S17, it is determined that the braking voltage value En[jN] is equal to the measured voltage Es[j], and the braking current value In[jN] is equal to the measured current Is[j].

[0129] In step S18, it is determined whether the measurement timing j has reached the maximum value M. If j is smaller than M, the process proceeds to step S19, where j is incremented by one, and the process returns to step S11, where the processes from step S11 onwards are executed again. If j has reached M, the process proceeds to step S20. In step S20, it is determined that the parameter Ma is equal to the final value of the detection timing jA of the driving power, and the parameter Mn is equal to the final value of the detection timing jN of the braking power. The parameter Ma is the total number of detection timing jA of the driving power, and the parameter Mn is the total number of detection timing jN of the braking power. Note that Ma + Mn = M.

[0130] In step S21, the characteristics calculation unit 320 calculates the motor characteristics according to the conventional power calculation method or the power separation calculation method. In the conventional power calculation method, the motor characteristics are calculated according to the above-mentioned equations (q1) to (q6). In the power separation calculation method, the motor characteristics related to driving power and the motor characteristics related to braking power are calculated as follows:

[0131] <Calculation of Motor Characteristics Related to Driving Power> The driving active power Pa is calculated according to the following equations: Pa = SQRT{ΣPea[jA]^2 / M} ...(q11) Pea[jA] = Ea[jA] × Ia[jA] ...(q12) Here, Σ indicates the addition of jA from 1 to Ma. Ma is the total number of driving power detection timings jA. M is the total number of measurement timings j. Equations (q11) and (q12) correspond to the above-mentioned equations (q1) and (q2). In other words, the driving active power Pa can be calculated by multiplying the driving voltage value Ea[jA] and driving current value Ia[jA] obtained at the driving power detection timing jA out of the M measurement timings to obtain the driving active power Pea[jA], and then calculating the root mean square of the driving active power Pea[jA], SQRT{ΣPea[jA]^2 / M}.

[0132] The drive apparent power Sa is calculated according to the following equations: Sa = Ea_rms·Ia_rms ... (q13) Ea_rms = SQRT(ΣEa[jA]^2 / M) ... (q14) Ia_rms = SQRT(ΣIa[jA]^2 / M) ... (q15) In this way, the drive apparent power Sa can be calculated by multiplying the root mean square Ea_rms of the drive voltage value Ea[jA] obtained at the detection timing jA of the M measurement timings by the root mean square Ia_rms of the drive current value Ia[jA] obtained at the detection timing jA of the M measurement timings.

[0133] The driving power factor ηa is calculated by dividing the driving effective power Pa by the driving apparent power Sa as shown in the following equation: ηa=Pa / Sa (q16)

[0134] <Calculation of motor characteristics related to braking power> The braking active power Pn is calculated according to the following equations: Pn = SQRT{ΣPen[jN]^2 / M} ...(q21) Pen[jN] = En[jN] × In[jN] ...(q22) Here, Σ represents the addition of jN from 1 to Mn. Mb is the total number of braking power detection timings jN. M is the total number of measurement timings j. The braking active power Pn can be calculated by multiplying the braking voltage value En[jN] and braking current value In[jN] obtained at the braking power detection timing jN out of the M measurement timings to obtain the braking active power value Pen[jN], and then calculating the root mean square of the braking active power value Pen[jN], SQRT{ΣPen[jN]^2 / M}.

[0135] The braking apparent power Sn is calculated according to the following equations: Sn = En_rms·In_rms ... (q23) En_rms = SQRT(ΣEn[jN]^2 / M) ... (q24) In_rms = SQRT(ΣIn[jN]^2 / M) ... (q25) In this way, the braking apparent power Sn can be calculated by multiplying the root mean square En_rms of the braking voltage value En[jN] obtained at detection timing jN among the M measurement timings by the root mean square In_rms of the braking current value In[jN] obtained at detection timing jN among the M measurement timings.

[0136] The braking force ratio ηn is calculated by dividing the braking effective power Pn by the braking apparent power Sn as shown in the following equation: ηn = Pn / Sn (q26)

[0137] In step S22, the characteristic display unit 330 displays the calculated characteristics of the brushless motor 100 on the display device of the characteristic test device 300.

[0138] 36 is an explanatory diagram showing an example of a display screen W1 of motor characteristics calculated by the power separation calculation method. At the top of the display screen W1, a mode selection tool MT is provided for selecting whether to use the power separation calculation method or the conventional power calculation method. In this example, the power separation calculation method is selected.

[0139] Display screen W1 displays first measurement results for driving power, including the root mean square (Ea_rms) of the driving voltage, the root mean square (Ia_rms) of the driving current, the driving apparent power (Sa), the driving active power (Pa), and the driving power factor (ηa). Also, display screen W1 displays second measurement results for braking power, including the root mean square (En_rms) of the braking voltage, the root mean square (In_rms) of the braking current, the braking apparent power (Sn), the braking active power (Pn), and the braking power factor (ηn). In this manner, this embodiment calculates and displays motor characteristics separately for driving power and braking power, allowing the user to learn more about the motor characteristics of brushless motor 100. It also allows the user to confirm whether the braking current is sufficiently small. Items other than the braking current may be omitted from display screen W1.

[0140] The present disclosure is not limited to the above-described embodiments, embodiments, and variations, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, embodiments, and variations corresponding to the technical features in each aspect described in the Summary of the Disclosure section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0141] (1) According to one aspect of the present disclosure, there is provided a motor drive control device that generates a PWM drive signal for driving a brushless motor. The motor drive control device includes a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or higher. With this motor drive control device, braking current can be reduced to a negligible level.

[0142] (2) The motor drive control device may further include an input signal generation circuit that generates a first input signal and a second input signal to be input to the PWM drive signal generation circuit in response to an analog electrical angle signal representing the electrical angle of the brushless motor, and the input signal generation circuit may include a circuit that inverts the waveforms of the first input signal and the second input signal, respectively, or crosses the first input signal and the second input signal in order to rotate the brushless motor forward or reverse. This motor drive control device can reverse the rotation direction of the brushless motor.

[0143] (3) In the above motor drive control device, the input signal generation circuit may be configured to directly transmit the first input signal and the second input signal to the PWM drive signal generation circuit regardless of whether the brushless motor is stopped or operating.

[0144] (4) In the motor drive control device, the input signal generating circuit may include an amplifier having a differential input or a differential output.

[0145] (5) In the above motor drive control device, the brushless motor may be a three-phase motor having three phase coils, and the motor drive control device may include three PWM drive signal generation circuits corresponding to the three phase coils, and an input signal generation circuit that generates three sets of input signals to be input to the three PWM drive signal generation circuits in accordance with an analog electrical angle signal representing the electrical angle of the brushless motor, and the input signal generation circuit may include a circuit that switches two sets of input signals out of the three sets of input signals to the three PWM drive signal generation circuits in order to rotate the brushless motor in a forward or reverse direction. This motor drive control device allows the three-phase motor to be freely switched between forward and reverse rotation.

[0146] (6) The motor drive control device may include a plurality of the PWM drive signal generation circuits corresponding to a plurality of phase coils of the brushless motor, and the plurality of PWM drive signal generation circuits may be configured to control an increase or decrease in torque and rotation speed by adjusting variable resistance values ​​linked to each phase.

[0147] (7) The motor drive control device may further include an input signal generation circuit that generates an input signal to the PWM drive signal generation circuit in response to an analog electrical angle signal representing the electrical angle of the brushless motor. The input signal generation circuit may include an inversion signal generation circuit that generates a first signal having a waveform proportional to the analog electrical angle signal and a second signal having a waveform obtained by inverting the first signal, and a signal selection circuit that selects one of the first signal and the second signal as a first input signal and the other as a second input signal in response to a rotation direction indication signal. The PWM drive signal generation circuit may be configured to compare a carrier signal having the PWM frequency with the first input signal to generate a first PWM drive signal that is supplied to a first end of an electromagnetic coil of the brushless motor, and to compare the carrier signal with the second input signal to generate a second PWM drive signal that is supplied to a second end of the electromagnetic coil. This motor drive control device may reverse the rotation direction of the brushless motor in response to the rotation direction indication signal.

[0148] (8) In the motor drive control device, the input signal generation circuit may further include a start trigger circuit that starts supplying the first input signal and the second input signal to the PWM drive signal generation circuit in response to a start instruction signal given when the brushless motor is stopped, thereby starting operation of the brushless motor. This motor drive control device can start the brushless motor in response to the start instruction signal.

[0149] (9) In the above motor drive control device, the PWM drive signal generation circuit may be configured as a BTL (Bridged Tied Load) compatible class D amplifier including a full bridge circuit. This motor drive control device can be configured using a class D amplifier for audio.

[0150] (10) In the motor drive control device, the class D amplifier may include a plurality of taps selected in response to a rotation speed increase / decrease instruction signal as taps for setting an amplification factor for amplifying an input signal input to the class D amplifier. This motor drive control device allows the rotation speed of a brushless motor to be changed.

[0151] (11) In the motor drive control device, the class D amplifier may further include a clipping circuit that clips the amplitude of the amplified signal, obtained by amplifying the input signal with the gain set by selecting the tap, at an upper limit value if the amplitude of the amplified signal exceeds the upper limit value. With this motor drive control device, the function of the clipping circuit can be used to perform field-weakening control of the brushless motor.

[0152] (12) The motor drive control device may further include an input signal generation circuit that generates an input signal to the PWM drive signal generation circuit in response to an electrical angle signal representing the electrical angle of the brushless motor. The PWM drive signal generation circuit may include a first comparator that generates a first comparison signal having a rectangular waveform by comparing a first input signal, the waveform of which is proportional to the waveform change of the electrical angle signal, with a carrier signal; a second comparator that generates a second comparison signal having a rectangular waveform by comparing a second input signal, which is the inverse of the first input signal, with the carrier signal; and a full-bridge circuit that generates the PWM drive signal to be applied to the electromagnetic coil of the brushless motor by taking the exclusive OR of the first comparison signal and the second comparison signal. This motor drive control device can minimize braking current to a negligible level. Furthermore, EMI countermeasures similar to spread spectrum modulation can be achieved using a full-bridge circuit without a modulation unit that modulates the PWM frequency.

[0153] (13) In the above motor drive control device, the input signal generation circuit may include a capacitive coupling provided in a signal path that transmits an in-circuit signal generated in response to the electrical angle signal, and a start trigger circuit that starts supply of the input signal to the PWM drive signal generation circuit in response to a start instruction signal given when the brushless motor is stopped, thereby starting operation of the brushless motor, wherein the start trigger circuit is configured to change a signal level at a specific position in the signal path that is located upstream of the capacitive coupling in response to the start instruction signal. This motor drive control device can start the brushless motor in response to the start instruction signal.

[0154] (14) In the motor drive control device, the start trigger circuit may include a rotation flag generation circuit that generates a rotation flag indicating whether the brushless motor is rotating in response to the electrical angle signal, an oscillation circuit that generates a pulse signal at a constant interval in response to the start instruction signal, a logic circuit that performs a logical operation on the rotation flag and the pulse signal to generate a start signal indicating that the pulse signal was generated while the brushless motor was stopped, and a signal level change circuit that changes the signal level at the specific position in response to the start signal. This motor drive control device can start the brushless motor in response to the start instruction signal.

[0155] (15) In the motor drive control device, the signal level change circuit may be configured to change the signal level at the specific position to a preset voltage level in response to the start signal. With this motor drive control device, the brushless motor can be started by changing the signal level at the specific position to the preset voltage level.

[0156] (16) In the above motor drive control device, the electrical angle signals may include an A-phase electrical angle signal indicating the electrical angle of an A-phase coil of the brushless motor and a B-phase electrical angle signal indicating the electrical angle of a B-phase coil of the brushless motor, and the signal level change circuit may be configured to cross the A-phase signal generated at the specific position in response to the A-phase electrical angle signal and the B-phase signal generated at the specific position in response to the B-phase electrical angle signal in response to the start signal. With this motor drive control device, the brushless motor can be started by crossing the A-phase signal and the B-phase signal at the specific position.

[0157] (17) In the motor drive control device, the signal level change circuit may be configured to use a threshold voltage equivalent to half the maximum voltage of the electrical angle signal to (i) change the signal level at the specific position to the maximum voltage in response to the start signal if the voltage level of the electrical angle signal is less than the threshold voltage, and (ii) change the signal level at the specific position to ground level in response to the start signal if the voltage level of the electrical angle signal is equal to or greater than the threshold voltage. This motor drive control device can start the brushless motor by changing the signal level at the specific position to the maximum voltage of the electrical angle signal or ground level.

[0158] (18) In the motor drive control device, the input signal generation circuit may include a lead angle adjustment circuit that generates an adjusted electrical angle signal by adjusting the phase of the electrical angle signal to advance the angle. With this motor drive control device, the power factor of the brushless motor can be improved by performing lead angle adjustment.

[0159] (19) A second aspect of the present disclosure provides a motor drive control device that generates a PWM drive signal for driving a brushless motor. The motor drive control device includes a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or higher, an analog control unit formed by an analog circuit, and a digital control unit formed by a digital circuit that generates an input signal to the analog control unit in response to an electrical angle signal representing the electrical angle of the brushless motor. The digital control unit is configured to perform feedback control in response to at least one of the rotation speed and phase current of the brushless motor. This motor drive control device can reduce braking current to a negligible level. Furthermore, feedback control can be achieved using the digital control unit.

Claims

1. A motor drive control device that generates a PWM drive signal for driving a brushless motor, comprising a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or more.

2. A motor drive control device according to claim 1, further comprising an input signal generation circuit that generates a first input signal and a second input signal to be input to the PWM drive signal generation circuit in accordance with an analog electrical angle signal that represents the electrical angle of the brushless motor, and the input signal generation circuit includes a circuit that inverts the waveforms of the first input signal and the second input signal, respectively, or crosses the first input signal and the second input signal in order to rotate the brushless motor forward or reverse.

3. A motor drive control device according to claim 2, wherein the input signal generation circuit is configured so that the first input signal and the second input signal are directly transmitted to the PWM drive signal generation circuit regardless of whether the brushless motor is stopped or operating.

4. A motor drive control device according to claim 2, wherein the input signal generating circuit includes an amplifier having a differential input or a differential output.

5. A motor drive control device according to claim 1, wherein the brushless motor is a three-phase motor having three phase coils, the motor drive control device comprising: three PWM drive signal generation circuits corresponding to the three phase coils; and an input signal generation circuit that generates three sets of input signals to be input to the three PWM drive signal generation circuits in accordance with an analog electrical angle signal representing the electrical angle of the brushless motor, the input signal generation circuit including a circuit that swaps two sets of input signals out of the three sets of input signals input to the three PWM drive signal generation circuits in order to rotate the brushless motor forward or reverse.

6. A motor drive control device according to claim 1, comprising a plurality of the PWM drive signal generation circuits corresponding to the plurality of phase coils of the brushless motor, and wherein the plurality of PWM drive signal generation circuits are configured so that torque and rotation speed increases and decreases are controlled by adjusting variable resistance values ​​linked to each phase.

7. A motor drive control device according to claim 1, further comprising an input signal generation circuit that generates an input signal to said PWM drive signal generation circuit in response to an analog electrical angle signal that indicates the electrical angle of said brushless motor, said input signal generation circuit including: an inversion signal generation circuit that generates a first signal having a waveform proportional to said analog electrical angle signal and a second signal having a waveform obtained by inverting said first signal; and a signal selection circuit that selects one of said first signal and said second signal as a first input signal and the other as a second input signal in response to a rotation direction indication signal, and outputs these signals; wherein said PWM drive signal generation circuit is configured to compare a carrier signal having said PWM frequency with said first input signal to generate a first PWM drive signal that is supplied to a first end of an electromagnetic coil of said brushless motor, and to compare said carrier signal with said second input signal to generate a second PWM drive signal that is supplied to a second end of said electromagnetic coil.

8. A motor drive control device according to claim 7, wherein the input signal generating circuit further includes a start trigger circuit that starts supplying the first input signal and the second input signal to the PWM drive signal generating circuit in response to a start instruction signal given when the brushless motor is stopped, thereby starting operation of the brushless motor.

9. A motor drive control device according to claim 1, wherein the PWM drive signal generating circuit is configured with a BTL (Bridged Tied Load) compatible class D amplifier including a full bridge circuit.

10. A motor drive control device according to claim 9, wherein the class D amplifier includes a plurality of taps selected in response to a rotation speed increase / decrease instruction signal as taps for setting an amplification factor for amplifying an input signal input to the class D amplifier.

11. A motor drive control device according to claim 10, wherein the class D amplifier further comprises a clipping circuit that clips the amplitude of the amplified signal, obtained by amplifying the input signal at the amplification factor set by the selection of the tap, at an upper limit value when the amplitude of the amplified signal exceeds the upper limit value.

12. A motor drive control device according to claim 1, further comprising: an input signal generation circuit that generates an input signal to said PWM drive signal generation circuit in accordance with an electrical angle signal that indicates the electrical angle of said brushless motor; said PWM drive signal generation circuit including: a first comparator that generates a first comparison signal having a rectangular wave by comparing a first input signal, the waveform of which changes proportionally to the waveform change of said electrical angle signal, with a carrier signal; a second comparator that generates a second comparison signal having a rectangular wave by comparing a second input signal, which is the inverse of the first input signal, with the carrier signal; and a full-bridge circuit that generates the PWM drive signal to be applied to the electromagnetic coil of said brushless motor by taking the exclusive OR of said first comparison signal and said second comparison signal.

13. A motor drive control device as claimed in claim 12, wherein the input signal generation circuit includes: a capacitive coupling provided in a signal path that transmits an in-circuit signal generated in response to the electrical angle signal; and a start-up trigger circuit that starts supplying the input signal to the PWM drive signal generation circuit in response to a start-up instruction signal given when the brushless motor is stopped, thereby starting operation of the brushless motor, and the start-up trigger circuit is configured to change the signal level at a specific position in the signal path that is located before the capacitive coupling in response to the start-up instruction signal.

14. A motor drive control device according to claim 13, wherein the start trigger circuit includes: a rotation flag generation circuit that generates a rotation flag indicating whether the brushless motor is rotating or not in accordance with the electrical angle signal; an oscillation circuit that generates a pulse signal at a fixed cycle in accordance with the start instruction signal; a logic circuit that performs a logical operation on the rotation flag and the pulse signal to generate a start signal indicating that the pulse signal was generated while the brushless motor was stopped; and a signal level change circuit that changes the signal level at the specific position in accordance with the start signal.

15. A motor drive control device according to claim 14, wherein the signal level change circuit is configured to change the signal level at the specific position to a preset voltage level in response to the activation signal.

16. A motor drive control device according to claim 14, wherein the electrical angle signals include an A-phase electrical angle signal indicating the electrical angle of the A-phase coil of the brushless motor, and a B-phase electrical angle signal indicating the electrical angle of the B-phase coil of the brushless motor, and the signal level change circuit is configured to cross the A-phase signal generated at the specific position in response to the A-phase electrical angle signal and the B-phase signal generated at the specific position in response to the B-phase electrical angle signal in response to the start signal.

17. A motor drive control device as claimed in claim 14, wherein the signal level change circuit is configured to use a threshold voltage equivalent to half the maximum voltage of the electrical angle signal to: (i) change the signal level at the specific position to the maximum voltage in response to the start signal when the voltage level of the electrical angle signal is less than the threshold voltage; and (ii) change the signal level at the specific position to the ground level in response to the start signal when the voltage level of the electrical angle signal is equal to or greater than the threshold voltage.

18. A motor drive control device according to claim 12, wherein the input signal generation circuit includes an advance angle adjustment circuit that generates an adjusted electrical angle signal by advancing the phase of the electrical angle signal.

19. A motor drive control device that generates a PWM drive signal for driving a brushless motor, comprising: an analog control unit formed by an analog circuit, including a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or more; and a digital control unit formed by a digital circuit that generates an input signal to the analog control unit in response to an electrical angle signal that represents the electrical angle of the brushless motor, wherein the digital control unit is configured to perform feedback control in response to at least one of the rotation speed and phase current of the brushless motor.

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