JP2010045941A - Motor control circuit, fan driver for vehicle and motor control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control circuit that reliably drives a brushless DC motor even if determined difficult to transit to sensorless control after the motor is started. <P>SOLUTION: When an upper controller 2 gives a start command to a motor 7 for rotating a vehicle fan 6 under a stop or low-speed rotary condition that cannot adapt sensorless control, a start control means 23 of a drive device 1 attempts switching to the sensorless control using a rectangular wave drive signal with an energization angle <180° after the motor 7 is started by forced commutation that applies a pseudo sinusoidal drive signal by complementary PWM control. In this case, if switching to the sensorless control cannot be done after a predetermined number of attempts, the motor 7 is kept driven by the forced commutation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor control circuit and a control method for driving and controlling a brushless DC motor without using a position sensor or the like, and a fan drive device for a vehicle including the motor control circuit.

  When driving a brushless DC motor, there are two control methods for driving without using a position sensor such as a Hall IC, and for driving with a sine wave voltage when the conduction angle is less than 180 °, and with a conduction angle of 180 °. It is roughly divided into two types. The control method when the energization angle is less than 180 ° is a method in which drive control is performed by detecting the zero cross point of the induced voltage generated in the winding during the energization stop period and performing position control, and can be realized with simple logic. .

  On the other hand, the method of driving with a sinusoidal voltage with an energization angle of 180 ° cannot calculate the position based on the induced voltage generated in the energization pause period, so it calculates at high speed from the winding voltage, winding current, and motor constants. Thus, the position is estimated and the drive is controlled. In this method, a sinusoidal voltage is applied, so torque ripple is very small and noise and vibration can be suppressed. However, a highly accurate current sensor is required, and a high-performance microcomputer is required for high-speed computation. It becomes.

In the sensorless control described above, the position cannot be detected when the motor is stopped or in a region where the rotational speed is low. Therefore, the synchronous motor is started up by forced commutation and switched to the sensorless control.
However, for example, a motor mounted in a vehicle, particularly in an engine room, has a very severe operating environment, and the magnetic flux of the rotor magnet decreases in an environment where the temperature is high. Therefore, the amplitude level of the induced voltage generated in the stator winding during rotation is also low. It is assumed that it will drop and it will become impossible to transfer to sensorless control. Also, the magnetic flux decreases when rust occurs on the rotor magnet during long-term use.

Patent Document 1 discloses a technique for retrying, for example, by increasing the applied voltage at forced commutation or increasing the number of rotations to switch to sensorless control when it is determined that the transition from synchronous operation to sensorless control has failed. Has been.
JP 2005-137069 A

  However, in the method as disclosed in Patent Document 1, when the cause of the failure to shift to sensorless control is due to environmental factors or changes over time as described above, the essential problem can be solved only by changing the control mode. There is a risk of repeated restarts. And, if the applied voltage is increased or the number of revolutions is increased to force the commutation by a conventional rectangular wave drive signal, the noise during driving becomes larger, which makes the vehicle occupant uncomfortable. Could just give.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control capable of reliably driving the motor even when it is determined that it is difficult to shift to the sensorless control after starting the brushless DC motor. An object of the present invention is to provide a circuit and motor control method, and a vehicle fan driving device including the motor control circuit.

According to the motor control circuit of claim 1, when the brushless DC motor is driven and controlled by the sensorless control method in which the position is estimated by the induced voltage generated in the energization stop period and energized at an energization angle of less than 180 °, the start control is performed. When a start command is given when the motor is in a stop state or low-speed rotation state where the sensorless control cannot be applied, the drive signal is forcedly changed so that the amplitude of the voltage applied to the motor changes gradually by complementary PWM control. After the motor is started by the flow, the control is switched to sensorless control.
Here, “complementary PWM control” refers to a method in which both the upper arm side and lower arm side switching elements constituting the inverter circuit are PWM controlled when the motor is PWM controlled via an inverter circuit.

That is, in a driving state by a steady sensorless system, even if a voltage waveform lacking smoothness (for example, a rectangular wave voltage waveform of 120 °) is applied to the motor due to a conduction angle of less than 180 °, the driving sound of the motor is not generated. Even in an application that does not cause a problem, the drive sound may be a problem when the motor is started from a stopped state or from a low-speed rotation state at a level where sensorless control cannot be applied. On the other hand, it is necessary to apply a torque for reliably starting the motor.
Therefore, when the motor is started from a stopped state or a low-speed rotation state, if the drive signal is forcedly commutated so that the amplitude of the voltage applied to the motor changes gently by complementary PWM control, the drive sound By appropriately adjusting the voltage level and frequency of the drive signal while suppressing the occurrence of the above, it is possible to give torque for reliably starting the motor.

  Then, the activation control means continues to drive the motor by forced commutation when the switch to the sensorless control cannot be made even after a predetermined number of attempts to switch to the sensorless control. That is, if the cause of the failure to shift to sensorless control is due to the operating environment being in a high temperature state as described above, or rusting in the rotor magnet, the transition is successful even after repeated retries. Probability is considered very low. Therefore, in such a case, the motor can be reliably driven by stopping the shift to the sensorless control and driving it with forced commutation as it is. In this case, the forced commutation is performed by applying a drive signal whose voltage amplitude is gently changed by complementary PWM control as in the start-up, so that driving of the motor is continued while suppressing generation of driving sound. Can do.

  According to the motor control circuit of the second aspect, the waveform of the starting drive signal is a pseudo sine wave that is set so that the amplitude of the voltage applied to the motor changes for each section having an electrical angle of less than 60 °. That is, by using a pseudo sinusoidal drive signal (a PWM signal with an average voltage having a sine wave shape), it is possible to smoothly start the motor and suppress the generation of drive sound.

  According to the motor control circuit of the third aspect, when the motor has three phases, the start control means applies the pseudo sine wave start drive signal to the motor by the two-phase modulation method. The total number of times of switching can be reduced. Further, since the number of elements that perform switching at the same time can be changed from six to four, heat generation of the entire apparatus can be suppressed. Furthermore, the current consumption of the circuit for driving the switching element can be reduced.

  According to the motor control circuit of the fourth aspect, since the waveform of the drive signal for starting is set to change in a trapezoidal shape, the motor can be started smoothly by a portion that gives a predetermined inclination to the voltage change.

  According to the motor control circuit of the fifth aspect, the waveform of the drive signal for starting is set so as to change in a triangular wave shape. In this case as well, the motor is started smoothly by a portion that gives a predetermined inclination to the voltage change. Can do.

  According to the motor control circuit of claim 6 or 7, the start control means gradually increases the motor applied voltage amplitude (claim 6) of the start drive signal at the time of forced commutation, or the motor applied voltage amplitude with respect to the frequency. Is gradually increased at a constant ratio (Claim 7), so that the start-up can be performed more smoothly and reliably.

  According to the motor control circuit of the eighth aspect, the start control means includes the storage means for storing the parameter initial value and the increase amount of the start drive signal so that the initial value and the increase amount can be varied. It is possible to determine how to change the drive signal to be applied according to the initial value and the increase amount stored in the storage means according to the characteristics of the motor to be used.

  According to the vehicle fan drive device of the ninth aspect, the motor control circuit according to any one of the first to eighth aspects is provided, and the fan mounted on the vehicle is driven by the motor. That is, a wind noise is generated in a state where the vehicle fan is constantly driven. Therefore, even if a motor driving sound is generated, it is masked by the vehicle occupant and cannot be heard as an abnormal sound, so there is no problem. However, when the motor is started from the rotation stop state or the low-speed rotation state, since the wind noise is hardly generated, the driving sound is difficult to be masked, so that the motor control circuit of the present invention can be applied very effectively.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to a vehicle fan drive device will be described with reference to FIGS. FIG. 1 shows an example of the configuration of an apparatus for driving a fan motor mounted on a vehicle by applying a rectangular wave by PWM control. When the fan processing device 1 receives a fan rotation speed command given as a PWM signal from a host controller 2 such as an ECU (Electronic Control Unit), for example, by the signal processing unit 3, it converts and generates a voltage signal corresponding to the duty of the PWM signal. And output to the rotational speed command conversion circuit 4. The host controller 2 receives output signals from, for example, a water temperature sensor (not shown) for detecting the water temperature inside the radiator, a vehicle speed sensor for detecting the vehicle speed, and the like, and outputs a rotational speed command corresponding to the detection results. Is.

  The rotation speed command conversion circuit 4 determines a rotation speed command according to the voltage signal and outputs the rotation speed command to the duty (DUTY) calculation circuit 5. The fan 6 is rotationally driven by a three-phase brushless DC motor 7, and the rotational state of the motor 7 is detected by a position detection circuit 8. The position detection circuit 8 is configured to detect rotation based on an induced voltage waveform generated in the winding of the motor 7 (so-called position sensorless system), for example.

  The rotation speed detection circuit 9 calculates the rotation speed of the motor 7 based on the detection signal output from the position detection circuit 8 (rotation position signal of the rotor constituting the motor 7), and outputs it to the input side of the duty calculation circuit 5 To do. Then, the difference between the rotational speed calculated by the rotational speed detection circuit 9 and the rotational speed command output by the rotational speed command conversion circuit 4 is calculated by the subtractor 10. The result is entered.

  The duty calculation circuit 5 calculates a duty command by performing, for example, PI (proportional integration) control based on the subtraction result, and the duty command is output to the duty command selection / voltage correction circuit 11. The duty command selection / voltage correction circuit 11 corrects the duty command given from the duty calculation circuit 5 in accordance with the voltage VB of the battery 12 of the vehicle, and responds to the switching signal given from the duty command generation circuit 13 in forced commutation. Thus, the form of the duty command output to the PWM signal generation circuit 14 is switched.

  That is, when a switching signal for outputting a duty command corresponding to forced commutation is given from the forced commutation duty command generation circuit 13, a duty command selection / voltage correction circuit (hereinafter simply referred to as a duty command selection circuit). ) 11 outputs a sinusoidal PWM duty command (see FIG. 3A) for three phases (the phases differ by 120 °). On the other hand, when the switching signal is not given, the duty command given from the duty calculation circuit 5 is outputted as it is. The duty command selection circuit 11 reads out data necessary for control from the EEPOM 24 (storage means) as necessary.

The PWM signal generation circuit 14 generates a PWM signal by comparing the amplitude of the corrected duty command given from the duty command selection circuit 11 and the internally generated PWM control carrier wave, and has six AND gates. 15 (U _U , U _D , V _U , V _D , W _U , W _D ) are output to input terminals. U-phase signal, the AND gate 15U _D via the NOT gate 16U with AND gates 15U _U, V-phase signal, through a NOT gate 16V to AND gate 15V _D with AND gate 15V _U, W-phase signal, AND via the NOT gate 16W is output to the aND gate 15W _D together with the gate 15W _U.

  The detection signal output by the position detection circuit 8 is also supplied to the energized phase distribution circuit 17, and the energized phase distribution circuit 17 uses a 120-degree energization pattern signal by a rectangular wave according to the rotational position of the rotor indicated by the detection signal. Is output to the remaining input terminals of each AND gate 15.

The AND gates 15U _U , 15V _U , and 15W _U are non-overrun using the PWM signal generated by the PWM signal generation circuit 14 as a high side signal during the period when the energization pattern signal supplied from the energization phase distribution circuit 17 is at a high level. The data is output to the gate drive circuit 18 via the lap setting unit 25. Further, the AND gate 15U _D, 15V _D, signals applied to the gate drive circuit 18 via the non-overlap setting unit 25 than 15W _D, a low-side signal. Here, “H” of the signal is a signal for turning on the driving of the MOS, and “L” is a signal for turning off the driving of the MOS.

The inverter circuit 19, for example, six power _{MOSFET19U U, 19V U, 19W U} ( which are _{P-channel), 19U D, 19V D,} 19W D ( which are N-channel) is configured by a three-phase bridge connection a gate signal output from the gate drive circuit 18 is supplied to the gates of the respective FET19U _U ~19W _D (switching element). Each phase output terminal of the inverter circuit 19 is connected to each phase winding 7U, 7V, 7W of the motor 7.

Incidentally, the non-overlap setting unit 25, the arm-side FET19U _U of inverter circuit 19, 19V _U, 19W _U and the lower arm corresponding to those side FET19U _D, through by 19V _D, and a 19W _D to ON at the same time In order to prevent current from flowing, it is arranged to set a period (non-overlap period) in which both FETs are simultaneously turned off while the level of the PWM signal transitions between high and low. Further, such a non-overlap setting unit may be configured integrally with logic circuits such as the AND gate 15 and the NOT gate 16. The non-overlap period is preferably set to a value as close to “0” as possible so that the distortion of the sine wave does not increase.

  A current detecting shunt resistor (current detecting means) 20 is connected between the lower arm side of the inverter circuit 19 and the ground. The terminal voltage of the shunt resistor 20 is a current detecting circuit (current detecting means) 21. Is detected by the forced commutation duty command generation circuit 13. Note that the shunt resistor 20 and the current detection circuit 21 are generally used for detection of overcurrent caused by step-out or overload, and the action when the detection current is given to the command generation circuit 13 is as follows. This will be described in a second embodiment described later. Further, the operation and circuit at the time of overcurrent caused by the above-described step-out or overload are not directly related to the present invention, and will be omitted.

The output signal of the rotation speed detection circuit 9 is also given to the drive method determination circuit 22, and the drive method determination circuit 22 sends a drive method switching signal to the forced commutation duty command generation circuit depending on the rotation speed of the motor 7. 13 and the energized phase distribution circuit 17.
In the above, the position detection circuit 8, the rotation speed detection circuit 9, the duty command selection circuit 11, the forced commutation duty command generation circuit 13, and the drive method determination circuit 22 constitute a start control means 23.

  Next, the operation of this embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing a circuit operation centering on the activation control means 23 of the driving device 1. When the host controller 2 outputs a rotation speed command for the fan 6, the signal processing unit 3 outputs a voltage signal obtained by signal processing of the command to the rotation speed command conversion circuit 4 (step S1). Then, the rotation speed command conversion circuit 4 determines a rotation speed command according to the voltage signal and outputs it to the duty calculation circuit 5 (step S2).

  Subsequently, the drive method determination circuit 22 detects the rotation speed of the motor 7 at that time by the rotation speed detection circuit 9 (step S3), and determines whether or not the rotation speed is equal to or less than a predetermined value Nmin “rpm”. (Step S4). For example, when the motor 7 is stopped or the motor 7 is not driven by the driving device 1 but the fan 6 receives the traveling wind and rotates at a low speed (YES), for example, in the inverter circuit 19 Direct current energization is performed from the arm: V, W phase to the lower arm: U phase to position the rotor of the motor 7 (step S5).

At this time, the driving mode determination circuit 22 is to activate the switching signal driving method, energization phase distribution circuit 17, the from when the switching signal is activated for a predetermined time period AND gate 15U _D, 15V _U, 15W _A high level signal is output only to _U. Further, when the switching signal is given through the forced commutation duty command generation circuit 13, the duty command selection circuit 11 outputs the PWM duty command at a predetermined DUTY for a predetermined time (for example, 10%). As this DUTY, a DUTY capable of generating a torque capable of positioning the rotor may be appropriately set.

  When rotor positioning is performed in step S5, the forced commutation duty command generation circuit 13 subsequently applies a duty command for applying a sinusoidal drive signal (three phases) as shown in FIG. Is output to the duty command selection circuit 11. Then, the duty command selection circuit 11 selects the duty command given from the forced commutation duty command generation circuit 13 and outputs it to the PWM signal generation circuit 14 to start the motor 7 by forced commutation (step S6). .

  In this case, the energized phase distribution circuit 17 outputs a high level signal to all the AND gates 15, and ON / OFF switching of the upper arm and lower arm of the inverter circuit 19 is performed only for the PWM signal output by the PWM signal generation circuit 14. To do. As a result, the PWM control form is complementary three-phase modulation, and the drive signal waveform during forced commutation is a PWM waveform with an average voltage of a sine wave as shown in FIG.

  Here, instead of the drive signal waveform having a sine wave shape as shown in FIG. 3A, a similar sine wave signal may be applied by the two-phase modulation method as shown in FIG. 3B. good. That is, while any one of the three phases is not switched (the upper arm is OFF and the lower arm is ON), the switching operation is performed by complementary PWM control between the remaining two phases.

  While performing forced commutation in step S6, the frequency of forced commutation is gradually increased (step S6a), and it is determined whether or not the frequency is equal to or higher than a predetermined value Fchange [Hz] (step S7). When the forced commutation frequency of the motor 7 becomes equal to or higher than the predetermined value Fchange [Hz] (YES), the driving method determination circuit 22 makes the driving method switching signal inactive. Then, the energization phase distribution circuit 17 outputs a low level signal to all the AND gates 15 for a predetermined time, turns off the energization by the inverter circuit 19, and puts the motor 6 into a free-run state (step S8). Here, the period during which the energization is turned off is 360 ° or more in electrical angle.

  When the energization OFF period elapses, the rotational speed of the motor 7 is increased to some extent at this stage, so that the rotor position based on the zero cross point of the induced voltage generated by the position detection circuit 8 in the windings 7U to 7W of the motor 7 The detection is sufficiently possible. Therefore, the duty command selection circuit 11 switches so as to output a PWM duty command for applying a rectangular-wave drive signal, and the energized phase distribution circuit 17 starts signal output for three-phase distribution and performs sensorless control. Transition is made (step S9).

Thereafter, “NO” is determined in step S4, and the process proceeds to step S9. The motor 7 is driven by applying a rectangular-wave drive signal by the sensorless control method.
The setting of the predetermined value Fchange in step S7 is, for example, a frequency at which the amplitude of the induced voltage generated in the windings 7U to 7W of the motor 7 reaches a level that enables position estimation by sensorless control. In addition to the conditions, the frequency at which the driving noise of the fan 6 by the motor 7 is equal to or higher than the driving noise of the motor 7 by the sensorless control of the rectangular wave may be used. When the latter is set, the driving noise of the motor 7 alone due to the rectangular wave is masked by the driving noise of the fan 6 and cannot be heard as an abnormal noise in the low rotation area where the noise of the fan 6 is low.

  After execution of step S9, it is determined whether or not the rotational speed of the motor 7 is equal to or greater than a predetermined value Nmin “rpm” (step S21). At this stage, if the rotational speed is equal to or greater than Nmin (YES), it can be determined that the sensorless control has been successfully shifted to, so the process returns to step S1 to continue the drive control.

  On the other hand, if the rotational speed of the motor 7 is less than Nmin (NO), it is determined that the shift to the sensorless control has failed, that is, the motor 7 has failed to start, so the number of times of start failure is counted by a counter ( Step S22). If the value of the counter does not reach a predetermined value A (for example, “3”) (step S23: NO), the process returns to step S5 to retry switching from positioning to forced commutation and sensorless control.

If the value of the start failure frequency counter becomes equal to or greater than the predetermined value A (step S23: YES) due to continuous failure to shift to sensorless control, the rotor is positioned as in steps S5 and S6 (step S24). The motor 7 is forcibly commutated by a sinusoidal PWM drive waveform (step S25).
In other words, if the cause of the failure to shift to sensorless control is due to the operating environment being at a high temperature or due to rusting on the rotor magnet, the probability of successful transition is extremely low even after repeated retries. it is conceivable that. Therefore, in such a case, the motor 7 can be reliably driven by stopping the shift to the sensorless control and driving it with forced commutation as it is.

As described above, according to the present embodiment, the start control means 23 of the drive device 1 is the host controller when the motor 7 that rotates the vehicle fan 6 is in a stop state or a low-speed rotation state where sensorless control cannot be applied. When the start command is given by No. 2, the motor 7 is started by forced commutation applying a pseudo sine wave drive signal by complementary PWM control, and then switched to sensorless control.
That is, wind noise is generated when the vehicle fan 6 is being driven steadily. Therefore, even if drive noise is generated by applying a rectangular wave drive voltage to the motor 7, There is no problem because it is masked. However, when the motor 7 is started from a state where the rotation is stopped or a low-speed rotation state, the drive sound is difficult to be masked, and the drive sound becomes a problem. There is also a need to apply torque for starting the motor 7 reliably.

  Therefore, when starting the motor 7, by applying a sine-wave drive signal and performing forced commutation, the motor 7 is started smoothly and the generation of drive sound is suppressed, while the voltage level of the drive signal or It is also possible to give a torque for starting the motor 7 reliably by adjusting the frequency appropriately. In this case, as shown in FIG. 3 (b), if a pseudo sine-wave start drive signal is applied to the motor 7 by the two-phase modulation method, the total number of times each FET of the inverter circuit 19 performs switching by PWM control is totalized. Thus, the driving current of the gate drive circuit 18 can be reduced and the switching loss (heat generation of each FET) can be suppressed.

  In addition, after the forced commutation is performed, the activation control means 23 switches to sensorless control after turning off the energization of the motor 7 for a predetermined period, for example, at an electrical angle of 360 ° or more at the rotation speed at the time of switching. Switching between methods can be performed smoothly by ensuring a sufficient interval. Furthermore, since the forced commutation is started after positioning the rotor of the motor by the direct current energization 7, the start-up of the motor 7 can be started smoothly from the state where the rotor position is determined.

  In addition, the activation control means 23 continues the drive of the motor 7 by forced commutation when the transition to the sensorless control cannot be made even after a predetermined number of times: A attempts. Therefore, even when the operating environment is in a high temperature state or the rotor magnet is rusted or the like is a cause of the transition failure, the motor 7 can be reliably driven. In this case, the forced commutation is performed by applying a drive signal whose voltage amplitude is gently changed by complementary PWM control as in the case of startup, so that the motor 7 is driven while suppressing the generation of drive sound. Can continue.

(Second embodiment)
FIG. 5 shows a second embodiment of the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals and the description thereof will be omitted. Hereinafter, different parts will be described. The configuration of the second embodiment is the same as that of the first embodiment, and the operation when the current detection circuit 21 is used will be described. In FIG. 5, which corresponds to FIG. 2, when the rotor positioning is performed by DC excitation in step S <b> 5, the duty command selection circuit 11 detects the current value flowing through the shunt resistor 20 at that time via the current detection circuit 21. (Step S11). Then, according to the magnitude of the current value, the voltage amplitude (maximum value) of the pseudo sine wave that is the drive signal for starting is variably set.

  That is, since the resistance of the winding of the motor 7 varies according to the ambient temperature, the current reflects the winding resistance value at that time according to the voltage applied to the winding during positioning. Therefore, if the voltage amplitude of the drive signal for start-up is set according to the current, stable start-up can be performed by flowing substantially the same current through the windings 7U to 7W of the motor 7 even when the ambient temperature is different.

(Third embodiment)
FIG. 6 shows a third embodiment of the present invention. In the third embodiment, the voltage of the activation drive signal is gradually increased (step S14). That is, the maximum value of the amplitude that changes sinusoidally is increased every time step S14 is executed. For example, it increases by 1% of the upper limit until the upper limit of the applied voltage is reached. Thereby, the motor 7 can be started more smoothly and reliably.

(Fourth embodiment)
FIG. 7 shows a fourth embodiment of the present invention. In the fourth embodiment, in step S15 instead of step S14 in the third embodiment, the commutation frequency and voltage of the drive signal for activation are sequentially increased at the same predetermined ratio. For example, when forced commutation is performed while increasing the frequency from 2.5 Hz to 25 Hz at a rate of 0.05 Hz / ms, the duty is increased from 15% to 0.36% / Hz. Thereby, the motor 7 can be started more smoothly and reliably.

(5th Example)
FIG. 8 shows a fifth embodiment of the present invention. In the fifth embodiment, both the commutation frequency and the voltage (parameter) of the drive signal for activation are sequentially increased as in the fourth embodiment. The EEPROM 24 (memory) uses the initial value and the increase amount as data. Remember me. When step S5 is executed, the duty command selection circuit 11 causes the commutation frequency stored in the EEPROM 24 and the initial value of the applied voltage (for example, the frequency is 2.5 Hz (30 rpm for a 10-pole motor), and the voltage is a duty 15 %) Is read and set (step S16), and the forced commutation in step S6 is started.

  Further, during the forced commutation in steps S6 and S7, the commutation frequency stored in the memory and the increase amount of the applied voltage (for example, the frequency is 0.05 Hz / ms, the voltage is duty 0.36% / Hz) is read and set (step S17), and the frequency and voltage are sequentially increased according to the increase amount. Accordingly, it is possible to determine how to change the drive signal to be applied according to the initial value and the increase amount stored in the memory, for example, according to the characteristics of the motor to be used.

(Sixth to eighth examples)
9 to 12 show sixth to eighth embodiments of the present invention. The sixth to eighth embodiments show variations of the startup drive signal waveform applied when the motor 7 is forcedly commutated. In the sixth embodiment shown in FIG. 9, the resolution of the pseudo sine wave by the two-phase modulation method similar to that in FIG. 3B is made rougher, and the energization angle is set to 15 ° steps.

  The seventh embodiment shown in FIG. 10 is a case where the voltage waveform is trapezoidal, and the slopes of the hypotenuses are different between (a) and (b). In the eighth embodiment shown in FIG. 11, the voltage waveform is triangular. Even in the case where the waveform of the drive signal for start-up is such, the change in applied voltage becomes more gradual compared to the rectangular wave, so that the motor 7 can be started smoothly.

  FIG. 12 compares torque ripples when the resolution of the pseudo sine wave is changed and when driven by a rectangular wave. The torque ripple when the energization angle is 30 ° is less than ½ of the rectangular wave. Although the torque ripple decreases as the resolution of the pseudo sine wave is improved, the circuit scale increases accordingly. Therefore, the trade-off between the two may be set so as to balance at an appropriate point according to the individual design.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
The drive signal waveform at the time of sensorless control is not limited to a rectangular wave of a 120 ° energization method, and may be any signal as long as the energization angle is less than 180 °.
In addition, the pseudo sine wave used as the drive signal for start-up may be, for example, one having an energization angle of 30 ° step, as long as the energization angle is less than 60 °.
The applied voltage of the drive signal during forced commutation may be constant as in the first embodiment depending on the load. Further, the frequency and applied voltage may be set to optimum values based on the load torque and the moment of inertia, such as setting the frequency and applied voltage high at first and then gradually decreasing them.

When starting forced commutation, the positioning of the rotor is not limited to the pattern shown in step S5. The rotor may be positioned as necessary.
The period during which the power supply to the motor is turned off during the transition from forced commutation to sensorless control is not limited to an electrical angle of 360 ° or more, and may be appropriately changed according to the individual design. Moreover, what is necessary is just to determine suitably also about whether to provide the electricity supply OFF period itself.
The predetermined value A may be appropriately changed and set.
The second embodiment may be applied to the third to eighth embodiments.
In the fifth embodiment, the storage means need not be an EEPROM.
An N-channel MOSFET may be used on the upper arm side of the inverter circuit.
The switching element constituting the inverter circuit may be an IGBT.
The present invention is not limited to driving a vehicle fan, and is particularly applicable to a motor that needs to reduce motor driving noise at startup.

The figure which is 1st Example of this invention and shows the structure of the fan drive device for vehicles. Flow chart showing circuit operation The figure which shows the waveform of the drive signal for starting The figure which shows that the average voltage of the drive signal for starting becomes a sine wave form by PWM control FIG. 2 equivalent diagram showing a second embodiment of the present invention. FIG. 2 equivalent view showing a third embodiment of the present invention. FIG. 2 equivalent diagram showing a fourth embodiment of the present invention. FIG. 2 equivalent diagram showing a fifth embodiment of the present invention. FIG. 3 equivalent view showing a sixth embodiment of the present invention. FIG. 3 equivalent diagram showing a seventh embodiment of the present invention. FIG. 3 equivalent view showing an eighth embodiment of the present invention. Comparison of torque ripples when changing the resolution of the pseudo sine wave and when driving with a square wave

Explanation of symbols

  In the drawings, 1 is a fan driving device, 6 is a fan, 7 is a three-phase brushless DC motor, 8 is a position detection circuit, 9 is a rotation speed detection circuit, 11 is a duty command selection circuit, and 13 is a duty command generation at forced commutation. Circuit, 19 an inverter circuit, 20 a shunt resistor (current detection means), 21 a current detection circuit (current detection means), 22 a drive method determination circuit, 23 a start control means, 24 an EEPROM (storage means), 31 Denotes a fan drive device, 32 denotes a temperature detection circuit (temperature detection means), 33 denotes a drive method determination circuit, 34 denotes a forced commutation duty command generation circuit, and 36 denotes an activation control means.

Claims (17)

In a motor control circuit for driving and controlling a brushless DC motor by a sensorless control method in which a position is estimated by an induced voltage generated in an energization pause section and energized at an energization angle of less than 180 °,
When a start command is given when the motor is in a stop state or low-speed rotation state where the sensorless control cannot be applied, the drive signal is forcedly changed so that the amplitude of the voltage applied to the motor changes gradually by complementary PWM control. After starting the motor by flow, control to switch to the sensorless control,
When the switching to the sensorless control is attempted a predetermined number of times and the shift to the sensorless control is not possible, the apparatus has a start control means for continuing the driving of the motor by the forced commutation as it is. Motor control circuit.   The motor control according to claim 1, wherein the waveform of the drive signal for start-up is a pseudo sine wave that is set so that an amplitude of a voltage applied to the motor changes for each section having an electrical angle of less than 60 °. circuit.   3. The motor control circuit according to claim 2, wherein, when the motor has three phases, the start control means applies the pseudo sine wave start drive signal to the motor by a two-phase modulation method.   The motor control circuit according to claim 1, wherein the waveform of the start drive signal is set to change in a trapezoidal waveform.   2. The motor control circuit according to claim 1, wherein the waveform of the starting drive signal is set so as to change in a triangular waveform.   6. The motor control circuit according to claim 1, wherein the start control unit gradually increases a voltage amplitude applied to the motor of the start drive signal during the forced commutation.   6. The start control means gradually increases the frequency of the start drive signal and the applied voltage amplitude to the motor at the time of the forced commutation at a constant ratio. Motor control circuit.   8. The start control means includes storage means for storing a parameter initial value and an increase amount of the start drive signal so that the initial value and the increase amount can be varied. Motor control circuit. A motor control circuit according to any one of claims 1 to 8,
A fan driving device for a vehicle, wherein a fan mounted on the vehicle is driven by the motor. In a method of driving and controlling a brushless DC motor by a sensorless control method in which a position is estimated by an induced voltage generated in an energization pause section and energized at an energization angle of less than 180 °,
When a start command is given when the motor is in a stop state or low-speed rotation state where the sensorless control cannot be applied, the drive signal is forcedly changed so that the amplitude of the voltage applied to the motor changes gradually by complementary PWM control. After starting the motor by flow, switch to the sensorless control,
A motor control method characterized in that if the switch to the sensorless control cannot be made even after a predetermined number of attempts to switch to the sensorless control, the driving of the motor by the forced commutation is continued as it is.   11. The motor control according to claim 10, wherein the waveform of the drive signal for start-up is a pseudo sine wave that is set so that an amplitude of a voltage applied to the motor changes for each section having an electrical angle of less than 60 °. Method.   The motor control method according to claim 11, wherein when the motor has three phases, the pseudo sine wave-like drive signal for starting is applied to the motor by a two-phase modulation method.   11. The motor control method according to claim 10, wherein the waveform of the drive signal for starting is set so as to change in a trapezoidal waveform.   The motor control method according to claim 10, wherein the waveform of the start drive signal is set so as to change in a triangular waveform.   The motor control method according to any one of claims 10 to 14, wherein an amplitude of a voltage applied to the motor of the driving signal for starting at the time of the forced commutation is gradually increased.   16. The motor control method according to claim 10, wherein the frequency of the start drive signal and the voltage amplitude applied to the motor at the time of the forced commutation are gradually increased at a constant ratio.   The motor control method according to claim 15 or 16, wherein the parameter initial value and the increase amount of the drive signal for activation are stored in a storage means, and the initial value and the increase amount are varied.

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