Motor drive control device

Abstract

This technology provides a way to minimize the braking current generated when a brushless motor is in operation. [Solution] The device of the present disclosure includes a motor drive control device comprising: a PWM drive signal generation circuit that generates a PWM drive signal at a PWM frequency of 280 kHz or higher; and an input signal generation circuit that generates an input signal to the PWM drive signal generation circuit according to an electrical angle signal representing the electrical angle of a brushless motor. The PWM drive signal generation circuit includes: a first comparator that generates a rectangular wave-shaped first comparison signal by comparing a first input signal having a waveform change proportional to the waveform change of the electrical angle signal with a carrier signal; a second comparator that generates a rectangular wave-shaped second comparison signal by comparing a second input signal with the carrier signal obtained by inverting the sign of the first input signal; and a full bridge circuit that generates a PWM drive signal applied to the electromagnetic coil of a brushless motor by taking the exclusive OR of the first comparison signal and the second comparison signal.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a motor control device that performs PWM control on 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor of the present disclosure has found that when driving a brushless motor, not only driving power but also braking power is generated. It has also been found that the amount of braking power generated depends on the PWM frequency. Therefore, a motor drive control device with a small amount of generated braking power is desired.

Means for Solving the Problems

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

[0006] According to a first embodiment of the present disclosure, a motor drive control device is provided 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, and an input signal generation circuit that generates an input signal to the PWM drive signal generation circuit according to an electrical angle signal representing the electrical angle of the brushless motor. The PWM drive signal generation circuit includes a first comparator that generates a rectangular wave-shaped first comparison signal by comparing a first input signal having a waveform change proportional to the waveform change of the electrical angle signal with a carrier signal, a second comparator that generates a rectangular wave-shaped second comparison signal by comparing a second input signal obtained by inverting the sign of the first input signal with the carrier signal, and a full bridge circuit that generates the PWM drive signal 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 allows the braking current to be reduced to a negligible level. Furthermore, it enables EMI countermeasures substantially similar to spread spectrum modulation using a full-bridge circuit without the need for a modulation section to modulate the PWM frequency.

[0007] A second embodiment of the present disclosure provides a motor drive control device for generating 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, and comprises an analog control unit formed of an analog circuit and a digital control unit formed of a digital circuit that generates an input signal to the analog control unit in accordance with an electrical angle signal representing the electrical angle of the brushless motor. The digital control unit is configured to perform feedback control in accordance with at least one of the rotational speed and phase current of the brushless motor. This motor drive control system allows the braking current to be reduced to a negligible level. Furthermore, feedback control can be implemented using a digital control unit. [Brief explanation of the drawing]

[0008] [Figure 1] A block diagram showing the configuration of the motor system in the first embodiment. [Figure 2] A graph showing the drive waveform, voltage, and current of a brushless motor. [Figure 3] A graph showing the difference in damping current depending on the PWM frequency. [Figure 4] A graph showing the change in damping current according to the PWM frequency. [Figure 5] A block diagram showing the configuration of the input signal generation circuit. [Figure 6] A block diagram showing the configuration of the rotation direction switching circuit. [Figure 7] A block diagram showing the configuration of a differential amplifier unit. [Figure 8] A block diagram showing the configuration of a PWM drive signal generation circuit. [Figure 9] A timing chart showing the operation of the PWM drive signal generation circuit. [Figure 10] A block diagram showing the configuration of the rotation flag generation circuit. [Figure 11] A timing chart showing the operation of the startup trigger circuit. [Figure 12] A block diagram showing the configuration of the input signal generation circuit in the second embodiment. [Figure 13] A timing chart showing the operation of the activation trigger circuit in the second embodiment. [Figure 14] A block diagram showing the configuration of the input signal generation circuit in the third embodiment. [Figure 15] A timing chart showing the operation of the activation trigger circuit in the third embodiment. [Figure 16] A timing chart showing the operation of the activation trigger circuit in the third embodiment. [Figure 17] A block diagram showing the configuration of the motor system in the fourth embodiment. [Figure 18] An explanatory diagram showing an example of the configuration of a low-pass filter circuit. [Figure 19]Explanatory diagram showing another example of the configuration of a low-pass filter circuit. [Figure 20] Block diagram showing the configuration of the input signal generation circuit in the fourth embodiment. [Figure 21] Block diagram showing the configuration of the ignition advance adjustment circuit. [Figure 22] Timing chart showing the operation of the ignition advance adjustment circuit. [Figure 23] Block diagram showing the configuration of the input signal generation circuit in the fifth embodiment. [Figure 24] Block diagram showing the configuration of the motor system in the sixth embodiment. [Figure 25] Block diagram showing the configuration of the motor system in the seventh embodiment. [Figure 26] Block diagram showing the configuration of the motor test system. [Figure 27] Graph showing the drive waveform, voltage measurement value, and current measurement value of the brushless motor. [Figure 28] Flowchart showing the procedure for the characteristic test of the brushless motor. [Figure 29] Explanatory diagram showing an example of the display screen of the motor characteristics.

Embodiments for Carrying Out the Invention

[0009] A. First Embodiment: FIG. 1 is a block diagram showing the configuration of the motor system in the first embodiment. This motor system has 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 the full-bridge circuit of the motor drive control device 400 that directly drives the brushless motor 100, and also supplies a voltage obtained by stepping down the DC voltage Ev with a step-down circuit as the power supply voltage for the circuit part excluding the full-bridge circuit.

[0010] The brushless motor 100 is a two-phase motor having an A-phase coil 102_A and a B-phase coil 102_B. However, this 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 420 as the number of phases, as shown in Figure 1.

[0011] The brushless motor 100 is equipped with magnetic sensors 104_A and 104_B that generate analog electrical angle signals Sin_A and Sin_B representing the electrical angle of the brushless motor 100. The analog electrical angle signals Sin_A and Sin_B have waveforms similar to the reverse induced voltage waveforms generated from each phase coil. Magnetic sensor 104_A generates the analog electrical angle signal Sin_A for the A-phase coil 102_A, and magnetic sensor 104_B generates the analog electrical angle signal Sin_B for the B-phase coil 102_B. The analog electrical angle signals Sin_A and Sin_B have sinusoidal waveforms. The magnetic sensors 104_A and 104_B are, for example, linear Hall ICs.

[0012] In this disclosure, a circuit code with "_A" appended to the end of its name indicates a circuit for the A-phase coil 102_A, and a circuit code with "_B" appended to the end of its name indicates a circuit for the B-phase coil 102_B. Similarly, signal names with "_A" appended to the end of their name indicate a signal for the A-phase coil 102_A, and signal names with "_B" appended to the end of their name indicate a signal for the B-phase coil 102_B. However, if it is not necessary to distinguish between the phases of the electromagnetic coils, the "_A" and "_B" at the end of the code or signal name may be omitted.

[0013] The motor drive control device 400 includes an input signal generation circuit 410, PWM drive signal generation circuits 420_A and 420_B, a start instruction signal generation unit 440, a rotation direction instruction unit 450, and a rotation speed increase / decrease instruction unit 460.

[0014] The PWM drive signal generation circuit 420_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 420_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 whose phase is shifted by 90 degrees from the PWM drive signals VP1_A and VP2_A 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.

[0015] The input signal generation circuit 410 is configured to generate input signals Vin1_A, Vin2_A, Vin1_B, and Vin2_B for the PWM drive signal generation circuits 420_A and 420_B according to analog electrical angle signals Sin_A and Sin_B representing the electrical angle of the brushless motor 100. The waveform change of the first input signal Vin1_A for phase A is proportional to the waveform change of the analog electrical angle signal Sin_A. The waveform of the second input signal Vin2_A is the waveform of the first input signal Vin1_A with the sign reversed. The same applies to the signals Vin1_B and Vin2_B for phase B.

[0016] The start command signal generator 440 supplies a start command signal Trg to the input signal generation circuit 410 to initiate the start of the brushless motor 100. When the start command signal Trg is supplied, the input signal generation circuit 410 starts supplying input signals Vin1 and Vin2 to the PWM drive signal generation circuit 420, and the brushless motor 100 begins to rotate. The internal configuration and operation of the start command signal generator 440 will be described later.

[0017] The rotation direction indicator unit 450 is used by the user to indicate the rotation direction of the brushless motor 100. That is, when the user selects either forward rotation or reverse rotation as the rotation direction, a rotation direction indicator signal Rd is input from the rotation direction indicator unit 450 to the input signal generation circuit 410. When the rotation direction indicator signal Rd is input, the phases of the input signals Vin1 and Vin2 from the input signal generation circuit 410 to the PWM drive signal generation circuit 420 are selected, and the brushless motor 100 rotates in either the forward or reverse direction. That is, the input signal generation circuit 410 is configured to include a circuit that either inverts the sign 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 in order to rotate the brushless motor 100 in either the forward or reverse direction. Here, "crossing" the two signals means swapping the two signals. In the case of a single-phase brushless motor, the direction of rotation can be controlled by a reversal signal (electrical angle π phase conversion), similar to a two-phase brushless motor. In the case of a three-phase brushless motor, the direction of rotation can be controlled in either the forward or reverse direction by swapping two of the three phases (U, V, and W).

[0018] 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. Furthermore, the input signal generation circuit 410 is configured to include a circuit that swaps two of the three sets of input signals {Vin1, Vin2} input to the three PWM drive signal generation circuits 420 in order to rotate the brushless motor 100 in the forward or reverse direction according to the rotation direction indicator 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.

[0019] The rotation speed increase / decrease instruction unit 460 is used by the user to instruct the increase or decrease of the torque or rotation speed of the brushless motor 100. That is, when the user instructs an increase or decrease in rotation speed, a rotation speed increase / decrease instruction signal Rv is input from the rotation 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 according to the rotation speed increase / decrease instruction signal Rv, and the rotation speed of the brushless motor 100 is set accordingly. The input signal generation circuit 410 may be configured to include the rotation speed increase / decrease instruction unit 460. Alternatively, if the PWM drive signal generation circuit 420 is configured with an audio Class D amplifier, the volume control potentiometer of the Class D amplifier may be used as the rotation speed increase / decrease instruction unit 460. By adjusting the amplitude level of the volume control potentiometer, linear increase / decrease adjustment over the entire range of rotation speed and torque of the brushless motor 100 can be easily achieved using the functions of the PWM drive signal generation circuit 420. In other words, simply by turning the volume control knob, you can start and operate the brushless motor 100 with the same ease as turning a power supply voltage knob, without having to set complex parameters like with a brushed motor.

[0020] Figure 2 is a graph showing the drive waveform, voltage, and current of the brushless motor 100. The brushless motor 100 is in a driving state that generates driving force. The A-phase voltage Vcoil_A and B-phase voltage Vcoil_B shown at the top of Figure 2 represent the ideal analog voltage waveforms of the two-phase electromagnetic coil 102. The voltage waveforms of the A-phase voltage Vcoil_A and B-phase voltage Vcoil_B change periodically every period Pw. One period Pw corresponds to an electrical angle of 360 degrees. The phase voltage Vpwm due to PWM control is a rectangular wave, as shown third from the top in Figure 2. The phase voltage Vpwm is the voltage corresponding to the difference between the PWM drive signals VP1 and VP2 applied across the electromagnetic coil 102. The fourth phase voltage Vpwm shown from the top in Figure 2 is a magnified view of a portion of it. The two graphs at the bottom of Figure 2 show magnified views of the phase voltage Vpwm and phase current Ipwm generated during one period Pe of PWM control.

[0021] Even when the brushless motor 100 is in a driving state that generates driving force, there are periods in which the sign of the phase current Ipwm differs, as shown in Figure 2. In the example in Figure 2, driving power is generated in the period when the phase current Ipwm is positive, and braking power is generated in the period when the phase current Ipwm is negative. Generally, driving power is generated when the sign of the phase voltage Vpwm and the phase current Ipwm are the same, and braking power is generated when the sign of the phase voltage Vpwm and the phase current Ipwm differ. The phase current Ipwm when the sign of the phase voltage Vpwm and the phase current Ipwm differ is called the "braking current". As will be explained below, the braking current changes significantly depending on the PWM frequency.

[0022] Figure 3 is a graph showing the difference in damping current depending on the PWM frequency. Here, the change in phase current at four PWM frequencies: 140 kHz, 210 kHz, 280 kHz, and 314 kHz is shown. These graphs are the results of a simulation under the same load on the brushless motor 100. The hatched areas correspond to the damping current. From these graphs, it can be seen that the damping current is larger as the PWM frequency decreases, and smaller as the PWM frequency increases.

[0023] Figure 4 is a graph showing the change in damping current according to the PWM frequency. The horizontal axis is the PWM frequency, and the vertical axis is the damping current. This graph is a semi-logarithmic graph, where the vertical axis is on a logarithmic scale. As can be seen from this graph, when the PWM frequency is 280 kHz or higher, the damping current can be reduced to a negligible level. Therefore, it is preferable to set the PWM frequency to 280 kHz or higher. It is even more preferable to set the PWM frequency to 300 kHz or higher. By setting the PWM frequency to 280 kHz or higher or 300 kHz or higher, and by using electromagnetic coils with small resistance and inductance values ​​and a small number of turns, it is possible to easily realize high-torque motors that require even larger currents, such as those used in the electrification of jet engines. Note that when the PWM frequency is 300 kHz or higher, the damping current becomes almost zero, so it is not necessary to set the PWM frequency excessively high, and 3 MHz or less is sufficient.

[0024] Figure 5 is a block diagram showing the configuration of the input signal generation circuit 410. The input signal generation circuit 410 includes a voltage adjustment circuit 411, a rotation direction switching circuit 412, an amplitude adjustment circuit 413, differential amplifier units 414_A and 414_B, and a start trigger circuit 415.

[0025] The voltage adjustment circuit 411 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 supplied from the magnetic sensor 104 of the brushless motor 100 to generate input signals Xin_A and Xin_B to the rotation direction switching circuit 412. The voltage at specific positions PP_A and PP_B in the signal path of the voltage adjustment circuit 411 changes in response to the signal from the start trigger circuit 415. This will be explained later.

[0026] The rotation direction switching circuit 412 generates output signals Xout_A and Xout_B according to the rotation direction indicator signal Rd provided by the rotation direction indicator unit 450. When the brushless motor 100 is rotated forward, the rotation direction switching circuit 412 outputs the input signals Xin_A and Xin_B as output signals Xout_A and Xout_B. When the brushless motor 100 is rotated in reverse, the rotation direction switching circuit 412 outputs signals with the positive and negative signs of the input signals Xin_A and Xin_B reversed, respectively, as output signals Xout_A and Xout_B.

[0027] Figure 6 is a block diagram showing the configuration of the rotation direction switching circuit 412. The rotation direction switching circuit 412 includes an inverting amplifier circuit 51, a selection circuit 52, and a reference voltage setting circuit 53.

[0028] The inverting amplifier circuit 51 is composed of an operational amplifier and has the function of inverting the sign of the input signals Xin_A and Xin_B. The selection circuit 52 selects one of the input signals Xin_A and Xin_B or their inverted signals according to the rotation direction indicator signal Rd provided from the rotation direction indicator unit 450. When the brushless motor 100 is rotated forward, the selection circuit 52 selects the input signals Xin_A and Xin_B and outputs them as output signals Xout_A and Xout_B. When the brushless motor 100 is rotated in reverse, the selection circuit 52 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 53 adjusts the reference voltage input to the positive input terminal of the operational amplifier so that the inverting amplifier circuit 51 operates properly.

[0029] The amplitude adjustment circuit 413 shown in Figure 5 generates signals Y_A and Y_B by increasing or decreasing the amplitude of signals Xout_A and Xout_B in response to the rotation speed increase / decrease instruction signal Rv provided by the rotation speed increase / decrease instruction unit 460. This amplitude adjustment adjusts the rotation speed and torque of the brushless motor 100.

[0030] The differential amplifier unit 414_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 with the sign reversed from that of signal Vin1_A. The differential amplifier unit 414_B is configured similarly.

[0031] Figure 7 is a block diagram showing the configuration of the differential amplifier unit 414. The differential amplifier unit 414 includes a differential amplifier 61 and an inverting amplifier 62. The differential amplifier 61 generates a signal Vin1 whose waveform change is proportional to the waveform change of the input signal Y. The inverting amplifier 62 generates a signal Vin2 whose waveform change is the reverse of the sign of signal Vin1. The first input terminal of the differential amplifier 61 is connected to the output terminal of the amplitude adjustment circuit 413 shown in Figure 5 via a coupling capacitor C1 as a capacitive coupling. The second input terminal of the differential amplifier 61 is grounded via a capacitor C2. Since the differential amplifier 61 amplifies the difference between the signal Y supplied from the amplitude adjustment circuit 413 and the ground potential, it can remove noise generated at the ground potential.

[0032] Figure 8 is a block diagram showing the configuration 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, two comparators 521 and 522, and a full bridge circuit 50. The first comparator 521 compares the first input signal Vin1 with the carrier signal Vcr to generate the first comparison signal Vc1. The second comparator 522 compares the second input signal Vin2 with the carrier signal Vcr to generate the second comparison signal Vc2. As mentioned above, the second input signal Vin2 is the signal obtained by inverting the sign of the first input signal Vin1.

[0033] The full-bridge circuit 530 is an H-bridge circuit composed of a first p-channel transistor 531p, a first n-channel transistor 531n, a second p-channel transistor 532p, and a second n-channel transistor 532n. The first comparison signal Vc1 is input to the gate terminals of the first p-channel transistor 531p and the first n-channel transistor 531n. The second comparison signal Vc2 is input to the gate terminals of the second p-channel transistor 532p and the second n-channel transistor 532n.

[0034] The first node 531c, located between the source terminal of the first p-channel transistor 531p and the drain terminal of the first n-channel transistor 531n, is connected to one end of the electromagnetic coil 102. From the first node 531c, a first PWM drive signal VP1 having a waveform similar to the first comparison signal Vc1 is supplied to the electromagnetic coil 102. The second node 532c, located between the source terminal of the second p-channel transistor 532p and the drain terminal of the second n-channel transistor 532n, is connected to the other end of the electromagnetic coil 102. From the second node 532c, a second PWM drive signal VP2 having a waveform similar to the second comparison signal Vc2 is supplied to the electromagnetic coil 102.

[0035] The carrier signal Vcr is a triangular wave or a sawtooth wave. The period Pcr of the carrier signal Vcr corresponds to the PWM period Pe shown in Figure 2. In this embodiment, the carrier period Pcr is constant. This PWM drive signal generation circuit 420 is a BTL (Bridged Tied Load) compatible Class D power amplifier having a full bridge circuit 530. However, the PWM drive signal generation circuit 420 may also be configured using two Class D power amplifiers, each having a half bridge circuit.

[0036] Figure 9 is a timing chart showing the operation of the PWM drive signal generation circuit 420 shown in Figure 8. The first comparison signal Vc1 output from the first comparator 521 is a square wave resulting from comparing the carrier signal Vcr with the first input signal Vin1, which has a waveform change proportional to the waveform change of the analog electrical angle signal Sin_A. The second comparison signal Vc2 output from the second comparator 522 is a square wave resulting from comparing the carrier signal Vcr with the carrier signal Vin2, which is the second input signal Vin2 obtained by inverting the sign of the first input signal Vin1. The PWM drive signals VP1 and VP2 have waveforms similar to the comparison signals Vc1 and Vc2. These PWM drive signals VP1 and VP2 form the AC voltage of the PWM drive signal Vpwm.

[0037] When both the first comparison signal Vc1 and the second comparison signal Vc2 are at a high level, the power supply potential Ev is applied to both ends of the electromagnetic coil 102, so the potential difference across the electromagnetic coil 102 is zero. Similarly, when both the first comparison signal Vc1 and the second comparison signal Vc2 are at a low level, both ends of the electromagnetic coil 102 are at ground potential, so the potential difference across the electromagnetic coil 102 is zero. When one of the first comparison signal Vc1 and the second comparison signal Vc2 is at a high level and the other is at a low level, the power supply potential Ev is applied to one end of the electromagnetic coil 102 and the other end is at ground potential, so the potential difference across the electromagnetic coil 102 is Ev. As can be understood from these operations, the PWM drive signal Vpwm applied to both ends of the electromagnetic coil 102 has the shape of the XOR (exclusive OR) of the first comparison signal Vc1 and the second comparison signal Vc2. Furthermore, considering the positive and negative nature of the potential difference, the potential difference applied across the electromagnetic coil 102 is positive when the first comparison signal Vc1 is at a high level and the second comparison signal Vc2 is at a low level, and negative when the first comparison signal Vc1 is at a low level and the second comparison signal Vc2 is at a high level. As can be understood from these explanations, the full-bridge circuit 530 is configured to generate and supply to the electromagnetic coil 102 a PWM drive signal Vpwm having a waveform proportional to the waveform obtained by taking the exclusive OR of the first comparison signal Vc1 and the second comparison signal Vc2.

[0038] The driving method that generates a PWM driving signal Vpwm by taking the exclusive OR of two comparison signals Vc1 and Vc2 achieves EMI (Electromagnetic Interference) countermeasures that are substantially similar to spread spectrum modulation. This can be understood from the waveforms of signals Vc1, Vc2, and Vpwm shown in Figure 9. That is, the first comparison signal Vc1 and the second comparison signal Vc2 are composed of square waves with frequencies approximately equal to the carrier frequency, so in the power spectrum obtained from their frequency analysis, the spectral intensity at the carrier frequency is a prominent peak. Conventional PWM driving signals are also signals in which the spectral intensity at the carrier frequency is a prominent peak. On the other hand, the PWM driving signal Vpwm generated in this embodiment corresponds to the signal obtained by taking the exclusive OR of the two comparison signals Vc1 and Vc2, so the number of edges occurring at frequencies different from the carrier frequency increases, and the spectral intensity at those frequencies also increases. As a result, the power spectrum of the PWM drive signal Vpwm is leveled overall, so that EMI countermeasures substantially similar to spread spectrum modulation can be achieved, and harmonics generated by PWM driving can be reduced. Thus, in this embodiment, EMI countermeasures substantially similar to spread spectrum modulation can be achieved without providing a frequency modulation unit that modulates the PWM frequency, so the circuit configuration of the PWM drive signal generation circuit 420 can be simplified.

[0039] The start trigger circuit 415 shown in Figure 5 starts the operation of the brushless motor 100 by starting to supply input signals Vin1 and Vin2 to the PWM drive signal generation circuit 420 in response to the start command signal Trg provided by the start command signal generation unit 440. The start trigger circuit 415 includes a rotation flag generation circuit 41, an oscillator circuit 42, an AND circuit 43, and switch circuits 44_A and 44_B.

[0040] The rotation flag generation circuit 41 generates a rotation flag FLG indicating whether the brushless motor 100 is rotating or not, in response to electrical angle signals Sin_A and Sin_B. In this embodiment, the rotation flag FLG is maintained at an H level when the brushless motor 100 is stopped, and drops to an L level when the brushless motor 100 is rotating. The oscillation circuit 42 generates a pulse signal PLS at a constant period when it receives a start instruction signal Trg. The AND circuit 43 generates a start signal SW indicating that the pulse signal PLS was generated while the brushless motor 100 was stopped by calculating the logical AND of the rotation flag FLG and the pulse signal PLS. Other logic circuits may be used instead of the AND circuit 43. This logic circuit is configured to generate a start signal SW indicating that the pulse signal PLS was generated while the brushless motor 100 was stopped by performing a logical operation on the rotation flag FLG and the pulse signal PLS. The switch circuits 44_A and 44_B turn on / off in response to the start signal SW. In other words, when the start signal SW rises to a high level in response to the start instruction signal Trg, the switch circuits 44_A and 44_B switch from off to on, and a preset voltage Vs / 2 is applied to specific positions PP_A and PP_B of the voltage adjustment circuit 411. That is, the voltage levels at specific positions PP_A and PP_B are forcibly set to the preset 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 44_A and 44_B function as signal level changing circuits that change the signal levels at specific positions PP_A and PP_B.

[0041] Figure 10 is a block diagram showing the configuration of the rotation flag generation circuit 41. The rotation flag generation circuit 41 includes coupling capacitors 31_A and 31_B, an integrating circuit 32 including a capacitor 33, and a comparator 34 composed of an operational amplifier. The coupling capacitors 31_A and 31_B receive analog electrical angle signals Sin_A and Sin_B and pass their fluctuating components (AC components) through. The fluctuating components of the analog electrical angle signals Sin_A and Sin_B are integrated by the integrating circuit 32 and the capacitor 33 is charged. The output voltage of the capacitor 33 is input to the negative input terminal of the comparator 34. A preset reference voltage is supplied to the positive input terminal of the comparator 34. When the rotation of the brushless motor 100 is stopped, the output voltage of the capacitor 33 is lower than the reference voltage of the comparator 34, so the rotation flag FLG output from the comparator 34 is at the H level. On the other hand, when the brushless motor 100 rotates, the output voltage of the capacitor 33 becomes higher than the reference voltage, so the rotation flag FLG output from the comparator 34 drops from a high level to a low level. In this way, the rotation flag generation circuit 41 generates the rotation flag FLG by integrating the fluctuating components of the analog electrical angle signals Sin_A and Sin_B corresponding to the rotation of the brushless motor 100 and comparing the integral result with the reference voltage, so the rotation flag FLG can be generated using a simple circuit configuration.

[0042] Figure 11 is a timing chart showing the operation of the start trigger circuit 415. Here, the start instruction signal Trg, the analog electrical angle signal Sin, the input signal Xin for the rotation direction switching circuit 412, the rotation flag FLG, the pulse signal PLS, the start signal SW, and the PWM drive signal Vpwm applied to the electromagnetic coil 102 are shown.

[0043] When the start command signal Trg rises from L level to H level in response to the user's start command, if the coupling capacitor C1 shown in Figure 5 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 414, so the PWM drive signals VP1 and VP2 are not generated and the brushless motor 100 remains in a stopped state. In this stopped state, the rotation flag FLG remains at the H level. When the pulse signal PLS is generated in response to the start command signal Trg, the start signal SW rises to the H level accordingly, causing the voltage of the input signal Xin of the rotation direction switching circuit 412 to fluctuate. This voltage fluctuation is achieved by forcibly setting the voltages at specific positions PP_A and PP_B shown in Figure 5 to a preset voltage Vs / 2. As a result, the generation of PWM drive signals VP1 and VP2 begins and the brushless motor 100 starts rotating. Note that the specific locations where the voltage is varied are not limited to the locations PP_A and PP_B shown in Figure 5, but may be other locations in the signal path prior to the coupling capacitor C1.

[0044] As described above, in the first embodiment, the PWM drive signal generation circuit 420 generates a PWM drive signal at a PWM frequency of 280 kHz or higher, so the braking current can be reduced to a negligible level. Furthermore, without providing a modulation unit to modulate the PWM frequency, EMI countermeasures substantially similar to spread spectrum modulation can be achieved using the full-bridge circuit 530. In addition, the brushless motor 100 can be started in response to the start instruction signal Trg.

[0045] B. Second Embodiment: Figure 12 is a block diagram showing the configuration of the input signal generation circuit 410 in the second embodiment. The input signal generation circuit 410 in the second embodiment omits the switch circuits 44_A and 44_B of the first embodiment shown in Figure 5 and adds a crossover circuit 45, while the other configurations are the same as in the first embodiment. The crossover circuit 45 is provided in the signal path between the voltage adjustment circuit 411 and the rotation direction switching circuit 412. The analog electrical angle signals Sin_A and Sin_B after voltage adjustment are input to the crossover circuit 45. Depending on the activation signal SW, the crossover circuit 45 can take on one of two states: a first state S1 in which the analog electrical angle signals Sin_A and Sin_B are passed through as they are, or a second state S2 in which the analog electrical angle signals Sin_A and Sin_B are crossed. That is, when the activation signal SW is at the L level, the crossover circuit 45 is in the first state S1, and 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. Furthermore, when the activation signal SW is at a high level, the crossover circuit 45 enters the second state S2, crossing the analog electrical angle signals Sin_A and Sin_B and outputting them as signals Xin_A and Xin_B.

[0046] Figure 13 is a timing chart showing the operation of the start trigger circuit 415 in the second embodiment. Here, the A-phase analog electrical angle signal Sin_A and the B-phase analog electrical angle signal Sin_B are drawn separately. When stopped, it is assumed that 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 start signal SW rises to the H level, the crossover circuit 45 crosses the analog electrical angle signals Sin_A and Sin_B, so the voltage levels of signals Xin_A and Xin_B change. As a result, the generation of PWM drive signals VP1 and VP2 begins, and the brushless motor 100 starts rotating.

[0047] The crossover circuit 45 functions as a signal level changing circuit that changes the signal level at a specific position in the signal path prior to the coupling capacitor C1. The crossover circuit 45 is not limited to the position between the voltage adjustment circuit 411 and the rotation direction switching circuit 412; it may also be provided at other positions in the signal path prior to the coupling capacitor C1. The second embodiment achieves substantially the same effects as the first embodiment.

[0048] C. Third Embodiment: Figure 14 is a block diagram showing the configuration of the input signal generation circuit 410 in the third embodiment. The input signal generation circuit 410 in the third embodiment omits the switch circuits 44_A and 44_B of the first embodiment shown in Figure 5 and adds a voltage change circuit 46, while the other configurations are the same as in the first embodiment. The voltage change circuit 46 has the function of changing the voltage at specific positions PP_A and PP_B in the signal path between the voltage adjustment circuit 411 and the rotation direction switching circuit 412 to either the maximum voltage Vs of the electrical angle signal Sin or the ground potential.

[0049] The voltage change circuit 46 includes a comparison circuit 81, a voltage selection circuit 82, and a switch circuit 83. The comparison circuit 81 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 of the maximum voltage Vs of the analog electrical angle signals Sin_A and Sin_B. The comparison circuit 81 sets the comparison signal SEL_A to the H level if 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 the L level if it is equal to or greater than the threshold voltage Vs / 2. The same applies to the B-phase.

[0050] The voltage selection circuit 82 selects the maximum voltage Vs when the comparison signal SEL_A is at a high level. When the activation signal SW becomes high and the switch circuit 83 turns on in this state, the voltage at the specific position PP_A is forcibly set to the maximum voltage Vs. On the other hand, the voltage selection circuit 82 selects the ground potential when the comparison signal SEL_A is at a low level. When the activation signal SW becomes high and the switch circuit 83 turns on in this state, the voltage at the specific position PP_A is forcibly set to the ground potential. The same applies to phase B.

[0051] Figure 15 is a timing chart showing the operation of the start trigger circuit 415 in the third embodiment. Figure 15 shows the operation when the voltage level of the analog electrical angle signal Sin is less than the threshold voltage Vs / 2 during stopping. When the start signal SW rises to the H level, the voltage level of the signal Xin changes to the maximum voltage Vs. As a result, the generation of PWM drive signals VP1 and VP2 begins, and the brushless motor 100 starts rotating.

[0052] Figure 16 shows the operation when the voltage level of the analog electrical angle signal Sin is greater than or equal to the threshold voltage Vs / 2 during a stop. When the start signal SW rises to a high level, the voltage level of signal Xin changes to ground potential. As a result, the generation of PWM drive signals VP1 and VP2 begins, and the brushless motor 100 starts rotating.

[0053] The voltage change circuit 46 functions as a signal level change circuit that changes the signal level at a specific position in the signal path prior to the coupling capacitor C1. The voltage change circuit 46 is not limited to the position between the voltage adjustment circuit 411 and the rotation direction switching circuit 412, but may be provided at other positions in the signal path prior to the coupling capacitor C1. The third embodiment also achieves substantially the same effects as the first embodiment.

[0054] Considering the configuration and operation of the start trigger circuit 415 in the first to third embodiments described above, it can be understood that it is preferable for the start trigger circuit 415 to be configured to change the signal level at a specific position in the signal path prior to the coupling capacitor C1 in accordance with the start instruction signal Trg.

[0055] D. Fourth Embodiment: Figure 17 is a block diagram showing the configuration of the motor system in the fourth embodiment. The motor drive control device 400 of the fourth embodiment is modified by adding low-pass filter circuits 430_A and 430_B between the PWM drive signal generation circuits 420_A and 420_B of the first embodiment shown in Figure 1 and the brushless motor 100, while the other configurations are the same as in the first embodiment.

[0056] When PWM drive signals VP1_A and VP2_A are input to the low-pass filter circuit 430_A for phase A, sinusoidal analog drive voltages Vout1_A and Vout2_A are output from the low-pass filter circuit 430_A and applied to the coil 102_A of the brushless motor 100. The same applies to phase B.

[0057] Figure 18 is an explanatory diagram showing an example of the internal configuration of a low-pass filter circuit 430. The low-pass filter circuit 430 includes a choke coil 431 and an integrating circuit 432. When the PWM drive signal generation circuit 420 generates a PWM drive signal at a PWM frequency of 280 kHz or higher, if the choke coil 431 is formed using ordinary magnet wire, the impedance of the choke coil 431 may become excessively high due to the skin effect. Therefore, it is preferable to form the choke coil 431 using a wire made of braided thin wires, such as Litz wire.

[0058] Figure 19 is an explanatory diagram showing another example of the internal configuration of the low-pass filter circuit 430. In this example, the choke coil 431 is configured as a common-mode choke coil. Using a common-mode choke coil allows for efficient reduction of high-frequency components.

[0059] The low-pass filter circuits 430_A and 430_B function as choke coils, thereby reducing iron losses due to harmonic components of the PWM drive signals VP1 and VP2. However, when using the low-pass filter circuits 430_A and 430_B, a phenomenon occurs where the phase of the phase current flowing through 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 and efficiency decreases. Therefore, in the fourth embodiment, the advance angle adjustment described below is performed.

[0060] Figure 20 is a block diagram showing the configuration of the input signal generation circuit 410 in the fourth embodiment. The input signal generation circuit 410 in the fourth embodiment has an advance angle adjustment circuit 416 added between the rotation direction switching circuit 412 and the amplitude adjustment circuit 413 of the first embodiment shown in Figure 5, and the other configurations are substantially the same as those of the first embodiment.

[0061] The advance angle adjustment circuit 416 generates signals Qout_A and Qout_B by performing an advance angle adjustment, which advances the phases of signals Xout_A and Xout_B by the advance angle adjustment amount θd, respectively, according to the advance angle adjustment amount θd provided from the outside. The generated signals Qout_A and Qout_B become the input signals for the amplitude adjustment circuit 413. As a result, the phases of the phase current and induced voltage 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 advance angle adjustment circuit 416 are also called "adjusted electrical angle signals".

[0062] Figure 21 is a block diagram showing the configuration of the advance angle adjustment circuit 416. The advance angle adjustment circuit 416 includes an AD converter 71, a phase adjustment unit 72, an electrical angle conversion unit 73, a waveform conversion unit 74, a waveform data table 75, and a DA converter 76. The AD converter 71 binarizes analog signals Xout_A and Xout_B and converts them into digital signals Dout_A and Dout_B. The phase adjustment unit 72 generates signals Pout_A and Pout_B by adjusting the phase of the digital signals Dout_A and Dout_B according to the advance angle adjustment amount θd. The electrical angle conversion unit 73 calculates electrical angles θ_A and θ_B according to signals Pout_A and Pout_B. The waveform conversion unit 74 reads waveform data Ddac_A and Ddac_B corresponding to electrical angles θ_A and θ_B from the waveform data table 75 and generates waveform data Ddac_A and Ddac_B. The "waveform data" is multi-gradation data that shows the waveform of the induced voltage generated in coils 102_A and 102_B in accordance with the rotation of the rotor. The waveform data stored in the waveform data table 75 can be arbitrarily set by an external circuit such as the CPU 77. The waveform data Ddac_A and Ddac_B are converted into analog signals, the adjustment electrical angle signals Qout_A and Qout_B, by the DA converter 76. These adjustment electrical angle signals Qout_A and Qout_B are input to the amplitude adjustment circuit 413 in Figure 20.

[0063] Figure 22 is a timing chart showing the operation of the advance angle adjustment circuit 416. It shows the clock signal CLK, the input signal Dout and output signal Pout to the phase adjustment unit 72, the output signal Ddac of the waveform conversion unit 74, the output signal Qout of the DA converter 76, 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 72 corresponds to 360 degrees of electrical angle.

[0064] The phase adjustment unit 72 generates the output signal Pout by advancing the phase of the input signal Dout by an advance angle adjustment amount θd. The minimum adjustment range in the phase adjustment unit 72 is one period of the clock signal CLK. The waveform data Ddac generated by the waveform conversion unit 74 is multi-gradation data representing the induced voltage waveform corresponding to the signal Pout after the advance angle adjustment. The output signal Qout of the DA converter 76 is the result of converting the waveform data Ddac into an analog signal. The phase current Qcoil in the electromagnetic coil 102 of the brushless motor 100 is delayed in phase by the low-pass filter circuit 430 shown in Figure 17, so it almost matches the phase of the induced voltage. By performing this advance angle adjustment, the phase of the phase current in coils 102_A and 102_B of the brushless motor 100 and the phase of the induced voltage can be matched, and the motor efficiency can be improved.

[0065] As described above, in the fourth embodiment, the iron loss due to harmonic components of the PWM drive signal can be reduced by using the low-pass filter circuit 430. Furthermore, since the advance angle is adjusted using the advance angle adjustment circuit 416, the decrease in motor efficiency caused by using the low-pass filter circuit 430 can be mitigated.

[0066] E. Fifth Embodiment: Figure 23 is a block diagram showing the configuration of the input signal generation circuit 410 in the fifth embodiment. The input signal generation circuit 410 in the fifth embodiment differs from the input signal generation circuit 410 in the fourth embodiment shown in Figure 20 in the following respects, while other configurations are the same as in the fourth embodiment. (1) Instead of analog electrical angular signals Sin_A and Sin_B, digital electrical angular signals Din_A and Din_B are supplied from the brushless motor 100. (2) The activation trigger circuit 415 is omitted. (3) The coupling capacitor C1 is omitted.

[0067] In the fifth embodiment, since digital electrical angle signals Din_A and Din_B are supplied from the brushless motor 100, the electrical angle signals Dout_A and Dout_B input from the rotation direction switching circuit 412 to the advance angle adjustment circuit 416 are digital signals. The advance angle adjustment circuit 416 of the fifth embodiment has a configuration in which the AD converter 71 is omitted from the advance angle adjustment circuit 416 of the fourth embodiment shown in Figure 21.

[0068] The fifth embodiment also produces almost the same effects as the fourth embodiment. In the fifth embodiment, a digital electrical angular signal Din is input to the input signal generation circuit 410, and an amplitude adjustment circuit 413 is used to adjust the amplitude to the same potential as the clamp potential of the differential amplifier unit 414. As a result, the analog signal Y generated using this digital electrical angular signal Din is directly input to the PWM drive signal generation circuit 420 without using a coupling capacitor C1. Therefore, the brushless motor 100 can be started even if the start trigger circuit 415 described in the first to fourth embodiments is omitted.

[0069] F. Sixth Embodiment: Figure 24 is a block diagram showing the configuration of the motor system in the sixth embodiment. This motor system includes a brushless motor 100 and a motor drive control device 600.

[0070] The brushless motor 100 includes an A-phase coil 102_A and 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.

[0071] The motor drive control device 600 includes a digital control unit 610 formed by a digital circuit and an analog control unit 620 formed by an analog circuit.

[0072] The digital control unit 610 includes a feedback control unit 611, a DA converter 612, a CPU 613, and a signal receiving unit 614. The signal receiving unit 614 receives digital electrical angle signals Din_A and Din_B and digital phase current signals Dis_A and Dis_B. A control command input unit 615 is connected to the digital control unit 610 for inputting control commands such as speed commands and position commands.

[0073] The feedback control unit 611 has the function of performing 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, it can perform one or more of the following: rotational speed control, torque control (current control), position control, etc. The feedback control unit 611 can be configured to include the rotational direction switching circuit 412, advance angle adjustment circuit 416, and waveform conversion circuit 417 shown in Figure 22.

[0074] The DA converter 612 converts the digital signals Ddac_A and Ddac_B generated by the feedback control unit 611 into analog signals Qout_A and Qout_B. The CPU 613 supplies control commands such as speed commands and position commands input from the control command input unit 615 to the feedback control unit 611. The signal receiving unit 614 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 611. The signal receiving unit 614 is wired to the electrical angle detection unit 104 and the phase current detection unit 106 of the brushless motor 100. The feedback control unit 611 can determine the rotational speed of the brushless motor 100 from the digital electrical angle signals Din_A and Din_B. Alternatively, the rotational speed signal may be received from a sensor that detects the rotational speed of the brushless motor 100.

[0075] The analog control unit 620 includes an amplitude adjustment circuit 621, differential amplifier units 622_A and 622_B, PWM drive signal generation circuits 623_A and 623_B, and low-pass filter circuits 624_A and 624_B. The amplitude adjustment circuit 621 and differential amplifier units 622_A and 622_B are the same as the amplitude adjustment circuit 413 and differential amplifier units 414_A and 414_B shown in Figure 23. The PWM drive signal generation circuits 623_A and 623_B and low-pass filter circuits 624_A and 624_B are the same as the PWM drive signal generation circuits 420_A and 420_B and low-pass filter circuits 430_A and 430_B shown in Figure 17.

[0076] The amplitude adjustment circuit 621 may be fixed at 100% adjustment (maximum amplitude state), and feedback control such as speed control and current control may be performed by the digital control unit 610. Alternatively, the amplitude adjustment circuit 621 can be used to adjust the response time of the feedback control. However, if these functions are not used, the amplitude adjustment circuit 621 can be omitted.

[0077] By configuring the motor drive control device 600 with a digital control unit 610 and an analog control unit 620, it is possible to perform high-precision feedback control with the digital control unit 610 while performing motor control with low loss and electromagnetic noise with the analog control unit 620.

[0078] G. Seventh Embodiment: Figure 25 is a block diagram showing the configuration of the motor system in the seventh embodiment. The motor drive control device 600 of the seventh embodiment is modified from the signal receiving unit 614 of the sixth embodiment shown in Figure 24 to perform wireless communication, and a wireless communication unit 108 is added to the brushless motor 100, with the other configurations being the same as in the sixth embodiment.

[0079] The signal receiving unit 614 of the motor drive control device 600 is wirelessly connected to the control command input unit 615 and the wireless communication unit 108 of the brushless motor 100. For wireless communication, for example, IP (Internet Protocol) wireless can be used. The motor drive control device 600 can receive rotational speed and phase current from the brushless motor 100 using wireless communication. In addition, the motor drive control device 600 can receive feedback control commands from the control command input unit 615 using wireless communication. As a result, wiring can be omitted, freeing the user from complex wiring and reducing production costs.

[0080] H. Characteristics test of brushless motors: Figure 26 is a block diagram showing the configuration of a motor test system. This motor test system is for testing the characteristics of a brushless motor 100 and comprises a motor test device 200 and a characteristics test device 300.

[0081] The brushless motor 100 is connected to the motor drive control device 400 shown in Figure 1. The motor drive control device 400 is supplied with a DC voltage Ev from a DC power supply 500. The coil connection wiring between the motor drive control device 400 and the brushless motor 100 is equipped with an ammeter 151 for measuring the coil current of the electromagnetic coil and a voltmeter 161 for measuring the coil voltage of the electromagnetic coil.

[0082] The motor test device 200 includes a first coupling 211, a torque meter 220, a second coupling 212, an electric brake 230, an AC / DC converter 240, a DC load unit 250, and a measurement value acquisition unit 260. The mechanical coupling structure including the first coupling 211, the torque meter 220, the second coupling 212, and the electric brake 230 is called the test coupling structure 270.

[0083] 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. Preferably, the torque meter 220 is also configured to measure the rotational speed Nm of the rotating shafts 221 and 222. Instead of measuring the rotational speed Nm with the torque meter 220, the rotational speed Nm may be accurately measured using a magnetic sensor 104 provided on the brushless motor 100, based on the clock counter value within the sensor signal. 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 losses (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 fixed to the stator and measures the magnetic flux density of a permanent magnet provided on the rotor. The magnetic sensor 234 is configured as, for example, a Hall IC. However, the magnetic sensor 234 is optional.

[0084] The AC / DC converter 240 is electrically connected to the multi-phase coils 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 unit 250 is electrically connected to the AC / DC converter 240 and, by constant current load control using the DC voltage Vd, the electric brake 230 is torque-controlled.

[0085] The measurement data acquisition unit 260 collects the measured coil voltage Es from the voltmeter 161, the measured coil current Is from the ammeter 151, and the torque T and rotational speed Nm from the torque meter 220, synchronized with the analog electrical angle signal Sin, and transfers them to the characteristic test device 300.

[0086] In this disclosure, regardless of whether the brushless motor 100 is a two-phase or three-phase motor, the measured phase voltage is used as the measured coil voltage Es, and the measured phase current Is is used as the measured coil current. For example, if the brushless motor 100 is a three-phase motor and the line voltage is measured, the phase voltage value obtained by multiplying the measured line voltage value by 1 / √3 is used as the measured coil voltage Es. Similarly, if the brushless motor 100 is a three-phase motor and the line current is measured, the phase current value obtained by multiplying the measured line current value by 1 / √3 is used as the measured coil current Is. In this disclosure, regardless of the number of phases of the motor, the phase voltage of one phase of the coil is referred to as "coil voltage," and the phase current of one phase of the coil is referred to as "coil current."

[0087] The characteristic test device 300 includes a measurement value acquisition unit 310, a characteristic calculation unit 320, and a characteristic display unit 330. The characteristic test device 300 also has the function of controlling each part of the motor test device 200. The measurement value acquisition unit 310 acquires measurement values, including the phase voltage and phase current measurements Es and Is 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 phase voltage and phase current measurements Es and Is. 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 device 300 can be implemented, for example, using a personal computer. The functions of the characteristic test device 300 are realized by a processor executing a computer program stored in the memory of the characteristic test device 300.

[0088] Figure 27 is a graph showing the drive waveform of the brushless motor 100 and the measured voltage Es[j] and current Is[j]. In Figure 27, the names of the phase voltage Vpwm and phase current Ipwm are changed to the measured voltage Es[j] and measured current Is[j], respectively, as in Figure 2, but the content of each signal is the same as in Figure 2. The dashed line indicates the measurement timing j, i.e., the sampling timing.

[0089] The following section will first explain the conventional method for calculating motor characteristics. In this specification, the conventional method for calculating motor characteristics will be 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.

[0090] <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 of finding the square root of the value in parentheses, Σ indicates the operation of adding j from 1 to M, "^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 conventional current value Ic[j] are equal to the measured voltage Es[j] and current Is[j] of the phase voltage, respectively.

[0091] Thus, the conventional active power Pc can be calculated by multiplying the conventional voltage value Ec[j] and 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.

[0092] The conventional apparent power Sc of the brushless motor 100 is calculated as follows, for each phase. Sc = Ec_rms·Ic_rms …(q3) Ec_rms = SQRT(ΣEc[j]^2 / M) …(q4) Ic_rms = SQRT(ΣIc[j]^2 / M) …(q5) Thus, 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.

[0093] 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)

[0094] Figure 28 is a flowchart showing the procedure for a characteristic test of the brushless motor 100. It is preferable to perform this characteristic test while the brushless motor 100 is rotating at a constant rotational speed Nm and a constant torque T.

[0095] In the process shown in Figure 28, the following parameters are used. The prefix "drive" indicates that the parameter relates to the drive power, and the prefix "braking" indicates that the parameter relates to the braking power. • N: The number of phase voltage periods Pw used for measuring phase voltage and phase current; an integer greater than or equal to 1. • M: The total number of measurement timings for phase voltage and phase current, which is an integer greater than N. • j: An ordinal number indicating the measurement timing, ranging from 1 to M. • jA: An ordinal number indicating the timing of drive power detection. • Ma: Total number of detection timing jA for drive power. • jN: An ordinal number indicating the timing of brake power detection. Mn: Total number of detection timings jN for braking power. • Es[j]: Voltage measurement of the phase voltage measured at timing j. • Is[j]: Current measurement of the phase current measured at timing j. • Ec[j]: The conventional voltage value, which is the conventional voltage value at timing j. • Ic[j]: The conventional current value, which is the conventional current value at timing j. • Ea[jA]: The drive voltage value, which is the voltage value of the drive power at timing jA. • Ia[jA]: The drive current value, which is the current value of the drive power at timing jA. • En[jN]: The braking voltage value, which is the voltage value of the braking power at timing jN. • In[jN]: The braking current value, which is the current value of the braking power at timing jN.

[0096] In step S10, the ordinal parameter j is initialized to 1, parameters jA and jN are initialized to 0, and the other parameters mentioned above are also initialized. In this embodiment, the number of phase voltage periods N used for measuring the phase voltage and phase current is assumed to be equal to 1.

[0097] 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 the measurement timing j.

[0098] In step S12, the conventional voltage value Ec[j] is determined to be equal to the measured voltage Es[j], and the conventional current value Ic[j] is determined to be equal to the measured current 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 equations (q1) to (q6) above. Step S12 may be omitted.

[0099] In step S13, the characteristic calculation unit 320 determines whether the positive or negative sign of the voltage measurement value Es[j] and the positive or negative sign of the current measurement value Is[j] are the same. This determination can be performed by applying the XNOR or XOR logical operation to the positive or negative sign of the voltage measurement value Es[j] and the positive or negative sign of the current measurement value Is[j]. If the positive or negative sign of the voltage measurement value Es[j] and the positive or negative sign of the current measurement value Is[j] are the same, it is assumed that drive power is being generated and the processes in steps S14 and S15 are executed. In step S14, the drive power detection timing jA is incremented by one. In step S15, it is determined that the drive voltage value Ea[jA] is equal to the voltage measurement value Es[j], and it is determined that the drive current value Ia[jA] is equal to the current measurement value Is[j].

[0100] On the other hand, if the positive or negative sign of the voltage measurement Es[j] and the positive or negative sign of the current measurement Is[j] are different, it is assumed that damping power is being generated, and the processes in steps S16 and S17 are executed. In step S16, the damping power detection timing jN is incremented by one. In step S17, the damping voltage value En[jN] is determined to be equal to the voltage measurement Es[j], and the damping current value In[jN] is determined to be equal to the current measurement Is[j].

[0101] In step S18, it is determined whether the measurement timing j has reached its maximum value M. If j is less than M, the process proceeds to step S19, where j is incremented by one and the process returns to step S11, and the steps from step S11 onwards described above are 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 drive power detection timing jA, and the parameter Mn is determined to be equal to the final value of the braking power detection timing jN. The parameter Ma is the total number of drive power detection timings jA, and the parameter Mn is the total number of braking power detection timings jN. Note that Ma + Mn = M.

[0102] In step S21, the characteristic 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 equations (q1) to (q6) described above. 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.

[0103] <Calculation of motor characteristics related to driving power> The active driving 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 represents the summation operation from 1 to Ma with respect to jA. 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 the drive current value Ia[jA] obtained at the drive power detection timing jA among 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}.

[0104] The 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) Thus, the apparent drive power Sa can be calculated by multiplying the root mean square Ea_rms of the drive voltage value Ea[jA] obtained at detection timing jA among the M measurement timings by the root mean square Ia_rms of the drive current value Ia[jA] obtained at detection timing jA among the M measurement timings.

[0105] 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)

[0106] <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 represents the summation operation from 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 the braking current value In[jN] obtained at braking power detection timing jN among 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}.

[0107] The damped 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) Thus, 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.

[0108] The braking force ratio ηn is calculated by dividing the braking active power Pn by the braking apparent power Sn, as shown in the following equation. ηn = Pn / Sn …(q26)

[0109] 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 apparatus 300.

[0110] Figure 29 is an explanatory diagram showing an example of a display screen W1 for motor characteristics calculated using the power separation calculation method. At the top of the display screen W1, there is a mode selection tool MT for specifying whether to use the power separation calculation method or the conventional power calculation method. In this example, the power separation calculation method is selected.

[0111] On display screen W1, the first measurement results for drive power are displayed, including the root mean square of the drive voltage value Ea_rms, the root mean square of the drive current value Ia_rms, the apparent drive power Sa, the active drive power Pa, and the power factor ηa. The second measurement results for braking power are also displayed, including the root mean square of the braking voltage value En_rms, the root mean square of the braking current value In_rms, the apparent braking power Sn, the active braking power Pn, and the braking power factor ηn. In this embodiment, the motor characteristics are calculated and displayed separately for drive power and braking power, allowing the user to understand the motor characteristics of the brushless motor 100 in more detail. Furthermore, it is possible to confirm whether the braking current is sufficiently small. Note that items other than the braking current may be omitted on display screen W1.

[0112] This disclosure is not limited to the embodiments, models, and modifications described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments, models, and modifications corresponding to the technical features in each form described in the Summary of the Disclosure section can be replaced or combined as appropriate to solve some or all of the above-described problems or to 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.

[0113] (1) According to a first embodiment of the present disclosure, a motor drive control device is provided that generates a PWM drive signal for driving a brushless motor. The motor drive control device comprises a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 kHz or higher, and an input signal generation circuit that generates an input signal to the PWM drive signal generation circuit according to an electrical angle signal representing the electrical angle of the brushless motor. The PWM drive signal generation circuit includes a first comparator that generates a rectangular wave first comparison signal by comparing a first input signal having a waveform change proportional to the waveform change of the electrical angle signal with a carrier signal, a second comparator that generates a rectangular wave second comparison signal by comparing a second input signal with the carrier signal obtained by inverting the sign of the first input signal, and a full bridge circuit that generates the PWM drive signal 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 allows the braking current to be reduced to a negligible level. Furthermore, it enables EMI countermeasures substantially similar to spread spectrum modulation using a full-bridge circuit without the need for a modulation section to modulate the PWM frequency.

[0114] (2) In the motor drive control device described above, the input signal generation circuit includes a capacitive coupling provided in a signal path that transmits an in-circuit signal generated in accordance with the electrical angle signal, and a start trigger circuit that starts supplying the input signal to the PWM drive signal generation circuit in accordance with a start instruction signal given when the brushless motor is stopped, thereby starting the operation of the brushless motor, wherein the start trigger circuit is configured to change the signal level at a specific position in the signal path prior to the capacitive coupling in accordance with the start instruction signal. This motor drive control device allows a brushless motor to be started in response to a start command signal.

[0115] (3) In the motor drive control device described above, the start trigger circuit may include: a rotation flag generation circuit that generates a rotation flag indicating whether or not the brushless motor is rotating in response to the electrical angle signal; an oscillation circuit that generates a pulse signal at a constant period in response to the start instruction signal; a logic circuit that generates a start signal indicating that the pulse signal was generated while the brushless motor was stopped by performing a logic operation between the rotation flag and the pulse signal; 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 allows a brushless motor to be started in response to a start command signal.

[0116] (4) In the motor drive control device described above, the signal level changing circuit may be configured to change the signal level at the specific position to a preset voltage level in response to the start signal. This motor drive control device allows a brushless motor to be started by changing the signal level at a specific location to a preset voltage level.

[0117] (5) In the motor drive control device described above, the electrical angle signal may 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 may be configured to cross an A-phase signal generated at the specific position in response to the A-phase electrical angle signal and a B-phase signal generated at the specific position in response to the B-phase electrical angle signal in response to the start signal. This motor drive control device allows a brushless motor to be started by crossing the A-phase signal and the B-phase signal at a specific position.

[0118] (6) In the motor drive control device described above, the signal level changing circuit may be configured to use a threshold voltage corresponding to half of the maximum voltage of the electrical angle signal, so as to: (i) when the voltage level of the electrical angle signal is less than the threshold voltage, change the signal level at the specific position to the maximum voltage in response to the start signal; and (ii) when the voltage level of the electrical angle signal is equal to or greater than the threshold voltage, change the signal level at the specific position to the ground level in response to the start signal. This motor drive control device allows a brushless motor to be started by changing the signal level at a specific position to either the maximum voltage of the electrical angular signal or the ground level.

[0119] (7) In the motor drive control device described above, the input signal generation circuit may include an advance angle adjustment circuit that generates an adjusted electrical angle signal by advancing the phase of the electrical angle signal. This motor drive control device allows for the improvement of the power factor of a brushless motor by adjusting the advance angle.

[0120] (8) A second embodiment of the present disclosure provides a motor drive control device for generating 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, and comprises an analog control unit formed of an analog circuit and a digital control unit formed of a digital circuit that generates an input signal to the analog control unit in accordance with an electrical angle signal representing the electrical angle of the brushless motor. The digital control unit is configured to perform feedback control in accordance with at least one of the rotational speed and phase current of the brushless motor. This motor drive control system allows the braking current to be reduced to a negligible level. Furthermore, feedback control can be implemented using a digital control unit. [Explanation of Symbols]

[0121] 31...Coupling capacitor, 32...Integrating circuit, 33...Capacitor, 34...Comparator, 41...Rotation flag generation circuit, 42...Oscillator circuit, 43...AND circuit, 44...Switch circuit, 45...Crossing circuit, 46...Voltage change circuit, 50...Full bridge circuit, 51...Inverting amplifier circuit, 52...Selection circuit, 53...Reference voltage setting circuit, 61...Differential amplifier, 62...Inverting amplifier, 71...AD converter, 72...Phase adjustment section, 73...Electrical angle conversion section, 74...Waveform conversion section, 75...Waveform data table, 76...DA converter, 77...CPU81...Comparison circuit, 82...Voltage selection circuit, 83...Switch circuit, 100...Brushless motor, 102...Electromagnetic coil, 104...Electric angle detection unit (magnetic sensor), 106...Phase current detection unit, 108...Wireless communication unit, 110...Rotating shaft, 151...Ammeter, 161...Voltmeter, 200...Motor test device, 211...First coupling, 212...Second coupling, 220...Torque meter, 221...First rotating shaft, 222...Second rotating shaft, 230...Electric brake, 232...Rotating shaft, 2 34…Magnetic sensor, 240…AC / DC conversion unit, 250…DC load unit, 260…Measurement value acquisition unit, 270…Test connection structure, 300…Characteristic test device, 310…Measurement value acquisition unit, 320…Characteristic calculation unit, 330…Characteristic display unit, 400…Motor drive control device, 410…Input signal generation circuit, 411…Voltage adjustment circuit, 412…Rotation direction switching circuit, 413…Amplitude adjustment circuit, 414…Differential amplifier unit, 415…Start trigger circuit, 416…Advance angle adjustment circuit, 417…Waveform change Conversion circuit, 420…PWM drive signal generation circuit, 430…Low-pass filter circuit, 431…Choke coil, 432…Integration 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…Full bridge circuit, 531c…First node, 531n…First n-channel transistor, 531p…First p-channel transistor T, 532c...Second node, 532n...Second n-channel transistor, 532p...Second p-channel transistor, 600...Motor drive control device, 610...Digital control unit, 611...Feedback control unit, 612...DA converter, 613...CPU, 614...Signal receiving unit, 615...Control command input unit, 620...Analog control unit, 621...Amplitude adjustment circuit, 622...Differential amplifier unit, 623...PWM drive signal generation circuit, 624...Low-pass filter circuit,

Claims

1. A motor drive control device that generates a PWM drive signal for driving a brushless motor, A PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 kHz or higher, An input signal generation circuit that generates an input signal to the PWM drive signal generation circuit according to an electrical angle signal representing the electrical angle of the brushed motor, Equipped with, The PWM drive signal generation circuit is A first comparator generates a rectangular wave-shaped first comparison signal by comparing a first input signal having a waveform change proportional to the waveform change of the electrical angular signal with a carrier signal. A second comparator generates a rectangular wave-shaped second comparison signal by comparing a second input signal, which is the first input signal with its sign inverted, with the carrier signal. A full-bridge circuit that generates the PWM drive signal applied to the electromagnetic coil of the brushless motor by taking the exclusive OR of the first comparison signal and the second comparison signal, A motor drive control device, including

2. A motor drive control device according to claim 1, The aforementioned input signal generation circuit is A capacitive coupling is provided in a signal path that transmits an in-circuit signal generated in accordance with the aforementioned electrical angle signal, A start trigger circuit that starts the operation of the brushless motor by starting to supply the input signal to the PWM drive signal generation circuit in response to a start command signal given when the brushless motor is stopped, Includes, The activation trigger circuit is configured to change the signal level at a specific position in the signal path prior to the capacitive coupling in accordance with the activation instruction signal. Motor drive control device.

3. A motor drive control device according to claim 2, The aforementioned activation trigger circuit is A rotation flag generation circuit generates a rotation flag indicating whether or not the brushless motor is rotating in response to the aforementioned electrical angle signal. An oscillator circuit that generates a pulse signal at a constant period in response to the aforementioned startup instruction signal, A logic circuit that generates a start signal indicating that the pulse signal was generated while the brushless motor was stopped by performing a logical operation between the rotation flag and the pulse signal, A signal level changing circuit that changes the signal level at the specific position in response to the activation signal, A motor drive control device, including

4. A motor drive control device according to claim 3, The signal level changing circuit is configured to change the signal level at a specific position to a preset voltage level in response to the activation signal, and is used as a motor drive control device.

5. A motor drive control device according to claim 3, The electrical angle signal includes 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. The aforementioned signal level changing circuit is configured to cross the A-phase signal generated at the specific position in accordance with the A-phase electrical angle signal and the B-phase signal generated at the specific position in accordance with the B-phase electrical angle signal, in accordance with the start signal, in a motor drive control device.

6. A motor drive control device according to claim 3, The signal level changing circuit uses a threshold voltage equivalent to half the maximum voltage of the electrical angular signal, (i) If the voltage level of the electrical angle signal is less than the threshold voltage, the signal level at the specific position is changed to the maximum voltage in accordance with the activation signal. (ii) If the voltage level of the electrical angle signal is equal to or greater than the threshold voltage, the signal level at the specific location is changed to the ground level in accordance with the activation signal. A motor drive control device configured in such a way.

7. A motor drive control device according to claim 1, 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. Motor drive control device.

8. A motor drive control device that generates a PWM drive signal for driving a brushless motor, The system includes a PWM drive signal generation circuit that generates the PWM drive signal at a PWM frequency of 280 kHz or higher, and an analog control unit formed by an analog circuit, A digital control unit formed by a digital circuit that generates an input signal to the analog control unit in accordance with an electrical angle signal representing the electrical angle of the brushed motor, Equipped with, The digital control unit is configured to perform feedback control according to at least one of the rotational speed and phase current of the brushless motor. Motor drive control device.

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