Motor drive control device

Abstract

To provide a technique for suppressing a braking current generated in a driving state of a brushless motor.SOLUTION: A motor drive control device that generates a PWM drive signal for driving a brushless motor includes a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency equal to or higher than 280KHz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a motor control device that PWM controls a brushless motor. In conventional technology, PWM control of a brushless motor is generally performed at a PWM frequency of about 20 KHz to 100 KHz. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-133890 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present disclosure discovered that when a brushless motor is driven, not only drive power but also braking power is generated. They 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. [Means for solving the problem]

[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 including a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or higher. According to this motor drive control device, the braking current can be reduced to a negligible level. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing the configuration of a motor system according to a first embodiment. [Figure 2] 3 is a graph showing the drive waveform, voltage, and current of a brushless motor. [Figure 3] A graph showing the difference in braking current depending on the PWM frequency. [Figure 4] Graph showing the change in braking current depending on the PWM frequency. [Figure 5] FIG. 2 is a block diagram showing the function of an input signal generating circuit according to the first embodiment. [Figure 6] FIG. 3 is a block diagram showing the function of a PWM drive signal generation circuit. [Figure 7] 4 is a timing chart showing the operation of the PWM drive signal generation circuit. [Figure 8] 4 is a timing chart showing the operation of the activation trigger circuit. [Figure 9] FIG. 10 is a block diagram showing the function of an input signal generating circuit according to a second embodiment. [Figure 10] 4 is a timing chart showing the operation of a clip circuit. [Figure 11] FIG. 1 is a block diagram showing the configuration of a motor testing system. [Figure 12] 6 is a graph showing the drive waveform of a brushless motor, and measured voltage and current values. [Figure 13] 10 is a flowchart showing the procedure for testing the characteristics of a brushless motor. [Figure 14] FIG. 4 is an explanatory diagram showing an example of a display screen of motor characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: 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. DC power supply 500 supplies a DC voltage Ev to a full-bridge circuit of motor drive control device 400, which directly drives brushless motor 100, and also supplies a voltage obtained by stepping down DC voltage Ev using a step-down circuit as the power supply voltage for circuitry other than the full-bridge circuit.

[0009] Brushless motor 100 is a two-phase motor having A-phase coil 102A and B-phase coil 102B. However, the present disclosure is applicable to brushless motors with any number of phases, including single-phase motors 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 in which driving force is generated, so the effects of the present disclosure are remarkable.

[0010] The brushless motor 100 is provided with magnetic sensors 104A and 104B that generate an analog electrical angle signal Sin that indicates the electrical angle of the brushless motor 100. The analog electrical angle signal Sin has a waveform similar to the waveform of the back electromotive force generated by each phase coil. The magnetic sensor 104A generates an analog electrical angle signal Sin for the A-phase coil 102A, and the magnetic sensor 104B generates an analog electrical angle signal Sin for the B-phase coil 102B. The analog electrical angle signal Sin has a sinusoidal waveform. The magnetic sensors 104A and 104B are, for example, linear Hall ICs.

[0011] In this disclosure, circuit symbols with an "A" at the end indicate that the circuit is for the A-phase coil 102A, and circuit symbols with a "B" at the end indicate that the circuit is for the B-phase coil 102B. 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 102A. Similar PWM drive signals VP1 and VP2 are also supplied to both ends of the B-phase coil 102B. However, the PWM drive signals VP1 and VP2 for the B-phase coil 102B are signals that are 90 degrees out of phase with the PWM drive signals VP1 and VP2 for the A-phase coil 102A. 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 an input signal generation circuit 410A, a PWM drive signal generation circuit 420A, and a low-pass filter circuit 430A as circuits that generate PWM drive signals VP1 and VP2 for the A-phase coil 102A, and an input signal generation circuit 410B, a PWM drive signal generation circuit 420B, and a low-pass filter circuit 430B as circuits that generate PWM drive signals VP1 and VP2 for the B-phase coil 102B.

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

[0017] The motor drive control device 400 further includes a start instruction signal generating section 440, a rotation direction instruction section 450, and a rotation speed increase / decrease instruction section 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 of 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 out 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 a 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] 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 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 460 to input signal generation circuit 410. Input signal generation circuit 410 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 410 may be configured to include rotational speed increase / decrease instruction unit 460. Alternatively, if PWM drive signal generation circuit 420 is configured with 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 460. 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 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 Pw period. One Pw period 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 fourth graph from the top of FIG. 2 shows an enlarged portion of the phase voltage Vpwm. The two graphs at the bottom of FIG. 2 show an enlarged view of the phase voltage Vpwm and the phase current Ipwm generated during one PWM control period Pe.

[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] Figure 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 to 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 a PWM frequency of 300 kHz or higher, there is no need to set the PWM frequency excessively high; a 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 by 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 by a variable resistor 11b within a range from 0 to the maximum amplitude, thereby adjusting the rotational speed, including torque. The signal adjusted by the variable resistor 11b is sent to an 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 the A phase and the input signal generation circuit 410B for the B phase, but the resistance value of the variable resistor 11b is adjusted so that it is linked to the same value for the A phase and the B phase.

[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, and outputs the selected signal. These input signals Vin1 and Vin2 are input to the PWM drive signal generation circuit 420. The 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, respectively. The signal selection circuit 413 can also be considered to correspond to a circuit that crosses 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 of 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 an H level in response to a change in the output DIFF of the differentiation circuit 41. The AND circuit 43 outputs the logical AND 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] 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 generate a selection signal SL that determines the direction of current flowing through each phase coil 102 of the brushless motor 100 and switches between positive and negative polarities. The 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 positive and a PWM drive signal VP2 that is negative for 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 BTL (Bridged Tied Load) compatible class D power amplifier having 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] 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 output from the first signal selection circuit 551 and the H-level signal Vh1, causing a positive current to flow. On the other hand, when first input signal Vin1<second input signal Vin2, PWM drive signal VP2 is output from full bridge circuit 560 in response to output signal Vg2 from first signal selection circuit 552 and H-level signal Vh2, causing a negative current to flow. These PWM drive signals VP1 and VP2 form AC voltages of PWM drive signals Vpwm on the positive and negative sides.

[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 of 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. Therefore, 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 differentiation circuit 41 and the output FLG of the flag generation circuit 42 both remain at L level. 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, discharging the coupling capacitor 12. 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 rotating. 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 generation 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: 9 is a block diagram showing the functions of an input signal generating circuit 410 in the second embodiment. The second embodiment differs from the first embodiment in the following respects, but is the same as the first embodiment in other respects. (1) The attenuator 411 a does not have a coupling capacitor 12 . (2) An amplifier 415 and a clipping circuit 416 are added between the attenuator 411 a and the inverted signal generating circuit 412 . (3) The activation 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 clip circuit 416. Clip circuit 416 has a configuration in which two Zener diodes arranged in opposite directions are connected in series and provided between the input terminal and output terminal of amplifier 415. Clip circuit 416 has a function of clipping amplified signal Sina, obtained by amplifying input signal Sin, at upper limit value Lim when the amplitude of the amplified signal Sina exceeds upper limit value Lim. Upper limit value Lim is set, for example, to a value corresponding to the amplitude level at which the duty of PWM control becomes 100%. By providing such clip circuit 416, it is possible to perform efficient field-weakening control of brushless motor 100, thereby easily increasing the rotational speed and torque to the load.

[0042] The clip 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 clip 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 clip circuit that clips the amplitude of the amplified signal, obtained by amplifying the input signal with the amplification factor set by selecting the tap, at a predetermined upper limit when the amplitude exceeds a predetermined upper limit. These clip circuits also achieve the same effect as that described with reference to FIG. 10 .

[0043] C. Brushless motor characteristic test: 11 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 characteristic testing device 300.

[0044] Brushless motor 100 is connected to motor drive control device 400 shown in Fig. 1. Motor drive control device 400 is supplied with DC voltage Ev 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.

[0045] 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.

[0046] 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 within 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.

[0047] AC / DC conversion unit 240 is electrically connected to the multi-phase coils of electric brake 230, and converts AC induced voltage Vi generated in the coils into DC voltage Vd by full-wave rectification. DC load unit 250 is electrically connected to AC / DC conversion unit 240, and consumes power generated by DC voltage Vd.

[0048] 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.

[0049] In this disclosure, regardless of whether brushless motor 100 is a two-phase motor or a three-phase motor, measured phase voltage values ​​are used as the measured coil voltage values ​​Es, and measured phase current values ​​are used as the measured coil current values ​​Is. For example, if brushless motor 100 is a three-phase motor and line voltages are measured, the phase voltage values ​​obtained by multiplying the measured line voltage values ​​by 1 / √3 are used as the measured coil voltage values ​​Es. Similarly, if brushless motor 100 is a three-phase motor and line currents are measured, the phase current values ​​obtained by multiplying the measured line current values ​​by 1 / √3 are used as the measured coil voltage values ​​Es. In this disclosure, regardless of the number of phases in 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."

[0050] 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.

[0051] Figure 12 is a graph showing the drive waveform, voltage measurement value Es[j], and current measurement value Is[j] of brushless motor 100. In Figure 12, the names of phase voltage Vpwm and phase current Ipwm in Figure 2 have been changed to voltage measurement value Es[j] and current measurement value 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.

[0052] 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.

[0053] <Conventional power calculation method for motor characteristics> The conventional active power Pc of each phase of the 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 to add from 1 to M for j, "^2" indicates the operation to square, 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 voltage measurement value Es[j] of the phase voltage and the current measurement value Is[j] of the phase current, respectively.

[0054] 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.

[0055] The conventional apparent power Sc of the brushless motor 100 is calculated as one phase of 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.

[0056] The conventional power factor ηc is calculated by dividing the conventional active power Pc by the conventional apparent power Sc as follows: ηc = Pc / Sc …(q6)

[0057] 13 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.

[0058] The following parameters are used in the process of Figure 13. The prefix "driving" means that the parameter is related to driving power, and the prefix "braking" means that the parameter is related to braking power. ·N: The number of phase voltage periods Pw during which the phase voltage and phase current are measured, and is an integer of 1 or greater. M: The total number of phase voltage and phase current measurement timings, an integer greater than N. ·j: An ordinal number indicating the measurement timing, an integer from 1 to M. ·jA: An ordinal number indicating the timing of detecting the drive power. · Ma: The total number of drive power detection timings jA. · jN: An ordinal number indicating the timing of detecting braking power. ·Mn: The total number of braking power detection timings jN. Es[j]: The voltage measurement value of the phase voltage measured at timing j. Is[j]: Current measurement value of the phase current measured at timing j. · Ec[j]: conventional voltage value, which is the conventional voltage value at timing j. · Ic[j]: conventional current value, which is the 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.

[0059] 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 of phase voltage periods N for which measurements of the phase voltage and phase current are performed is set to be equal to 1.

[0060] In step S11, the measurement value acquiring unit 310 acquires the voltage measurement value Es[j] and the current measurement value Is[j] measured at measurement timing j.

[0061] In step S12, the conventional voltage value Ec[j] is determined to be equal to the voltage measurement value Es[j], and the conventional current value Ic[j] is determined to be equal to the current measurement 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.

[0062] 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, the drive voltage value Ea[jA] is determined to be equal to the measured voltage Es[j], and the drive current value Ia[jA] is determined to be equal to the measured current Is[j].

[0063] On the other hand, if the sign of the measured voltage Es[j] is different from the sign of the measured current Is[j], it is assumed that braking power is being generated, and 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].

[0064] 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 1 and the process returns to step S11, where the processing from step S11 onwards is executed again. If j has reached M, the process proceeds to step S20. In step S20, the parameter Ma is determined to be equal to the final value of the detection timing jA of the driving power, and the parameter Mn is determined to be 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.

[0065] 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, respectively.

[0066] <Calculation of motor characteristics related to driving power> The driving active power Pa is calculated according to the following formula: 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 drive 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). That is, the drive active power Pa can be calculated by multiplying the drive voltage value Ea[jA] and drive current value Ia[jA] obtained at the drive power detection timing jA out of the M measurement timings to obtain the drive active power value Pea[jA], and then calculating the root mean square of the drive active power value Pea[jA], SQRT{ΣPea[jA]^2 / M}.

[0067] The driving apparent power Sa is calculated according to the following formula: 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 among the M measurement timings by the root mean square Ia_rms of the drive current value Ia[jA] obtained at the detection timing jA among the M measurement timings.

[0068] The driving power factor ηa is calculated by dividing the driving active power Pa by the driving apparent power Sa as shown in the following equation. ηa = Pa / Sa …(q16)

[0069] <Calculation of motor characteristics related to braking power> The braking active power Pn is calculated according to the following formula: Pn = SQRT{ΣPen[jN]^2 / M} …(q21) Pen[jN] = En[jN]×In[jN] …(q22) Here, Σ indicates the addition of 1 to Mn for jN. 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 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}.

[0070] The braking apparent power Sn is calculated according to the following formula: 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 the detection timing jN among the M measurement timings by the root mean square In_rms of the braking current value In[jN] obtained at the detection timing jN among the M measurement timings.

[0071] 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)

[0072] 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.

[0073] Figure 14 is an explanatory diagram showing an example of a display screen W1 of motor characteristics calculated using the power separation calculation method. At the top of the display screen W1, a mode selection tool MT is provided for specifying whether to use the power separation calculation method or the conventional power calculation method. In this example, the power separation calculation method has been selected.

[0074] 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). Display screen W1 also 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 way, 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.

[0075] 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.

[0076] (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 including a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 KHz or higher. According to this motor drive control device, the braking current can be reduced to a negligible level.

[0077] (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 accordance with an analog electrical angle signal that represents 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.

[0078] (3) In the above motor drive control device, the input signal generation circuit may be 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.

[0079] (4) In the motor drive control device, the input signal generating circuit may include an amplifier having a differential input or a differential output.

[0080] (5) In the above motor drive control device, the brushless motor is a three-phase motor having three phase coils, and the motor drive control device includes 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 that represents the electrical angle of the brushless motor, and the input signal generation circuit may include a circuit that swaps two sets of input signals out of the three sets of input signals to be input to the three PWM drive signal generation circuits in order to rotate the brushless motor forward or reverse. This motor drive control device allows the three-phase motor to be switched between forward and reverse rotation at will.

[0081] (6) The motor drive control device may include a plurality of the PWM drive signal generation circuits corresponding to the plurality of phase coils of the brushless motor, and the plurality of PWM drive signal generation circuits may be configured to control the increase and decrease of torque and rotation speed by adjusting variable resistance values ​​linked to each phase.

[0082] (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 can reverse the rotation direction of the brushless motor in response to a rotation direction instruction signal.

[0083] (8) In the above 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 a start instruction signal.

[0084] (9) In the motor drive control device, the PWM drive signal generating circuit may be configured with a BTL (Bridged Tied Load) compatible class D amplifier including a full bridge circuit. According to this motor drive control device, the motor drive control device can be configured using a class D amplifier for audio.

[0085] (10) In the above 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 the brushless motor to be changed.

[0086] (11) In the above 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 amplification factor set by selecting the tap, at an upper limit value when the amplitude of the amplified signal exceeds the upper limit value. According to this motor drive control device, the function of the clip circuit can be used to execute field weakening control of the brushless motor. [Explanation of symbols]

[0087] 11a...variable resistor, 11b...attenuator, 12...coupling capacitor, 21, 22...inverting amplifier, 41...differential circuit, 42...flag generation circuit, 43...AND circuit, 44...switch circuit, 45...resistor, 100...brushless motor, 102...electromagnetic coil, 104...magnetic sensor, 110...rotating shaft, 151...ammeter, 161...voltmeter, 200...motor test equipment, 211, 212...coupling, 220...torque meter, 221, 222...rotating shaft, 230...electric brake, 232...rotating shaft, 234...magnetic sensor, 240...AC / DC conversion unit, 250...DC load unit, 260...measurement value collection unit, 270...test connection structure, 300...characteristic test device, 310...measurement Constant value acquisition unit, 320...characteristic calculation unit, 330...characteristic display unit, 400...motor drive control device, 410...input signal generation circuit, 411...attenuator, 412...inverted signal generation circuit, 413...signal selection circuit, 414...start trigger circuit, 415...amplifier, 416...clipping circuit, 420...PWM drive signal generation circuit, 430...low pass filter circuit, 440...start instruction signal generation unit, 450...rotation direction instruction unit, 460...rotation speed increase / decrease instruction unit, 500...DC power supply, 510...carrier signal generation circuit, 521...first comparator, 522...second comparator, 530...third comparator, 540...XOR circuit, 551...first signal selection circuit, 561...second signal selection circuit, 560...full bridge circuit

Claims

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

2. The 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 response to an analog electrical angle signal that represents an electrical angle of the brushless motor; The motor drive control device, wherein the input signal generating circuit includes a circuit that inverts the waveforms of the first input signal and the second input signal, or crosses the waveforms of the first input signal and the second input signal, in order to rotate the brushless motor forward or reverse.

3. The motor drive control device according to claim 2, the input signal generation circuit is 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.

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

5. The motor drive control device according to claim 1, the brushless motor is a three-phase motor having three phase coils; The motor drive control device includes: three PWM drive signal generating circuits corresponding to the three phase coils; an input signal generation circuit that generates three sets of input signals to be input to the three PWM drive signal generation circuits in response to an analog electrical angle signal that represents the electrical angle of the brushless motor; Equipped with the input signal generation circuit includes 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. The motor drive control device according to claim 1, a plurality of the PWM drive signal generation circuits corresponding to a plurality of phase coils of the brushless motor; The motor drive control device is configured such that the increase and decrease of torque and rotation speed of the plurality of PWM drive signal generation circuits are controlled by adjusting variable resistance values ​​linked to each phase.

7. The motor drive control device according to claim 1, further comprising: 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 that represents the electrical angle of the brushless motor; The input signal generating circuit an inversion signal generating 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; 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, and outputs the selected signal; Including, the PWM drive signal generation circuit is configured to generate a first PWM drive signal supplied to a first end of an electromagnetic coil of the brushless motor by comparing a carrier signal having the PWM frequency with the first input signal, and to generate a second PWM drive signal supplied to a second end of the electromagnetic coil by comparing the carrier signal with the second input signal.

8. The motor drive control device according to claim 7, The input signal generating circuit further 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.

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

10. 10. The motor drive control device according to claim 9, The class D amplifier includes a plurality of taps that are 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. The motor drive control device according to claim 10, The motor drive control device, wherein the class D amplifier further has 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.

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