JP2014087113A - Motor Drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device which, while performing quick and sure startup or constraint operation or stepping-out prevention by sensor drive, can dispense with a startup circuit and a startup procedure for sensorless drive, and can switch to sensorless drive at the time of normal revolution, thereby enabling the motor to rotate with low vibration and low current consumption.SOLUTION: Induced voltage determination means 8 compares a zero-cross signal and a logic value based on an excitation sequence determined by excitation sequence information from a decoder 2 at the time of excitation switchover, and outputs, to sensor selection means 4, a match signal when the zero-cross signal is found to agree with the logic value, or a mismatch signal when the zero-cross signal is not found to agree, the sensor selection means 4 selecting an internal sensor signal upon receiving the match signal and selecting an external sensor signal upon receiving the mismatch signal.

Description

  The present invention relates to a motor driving device that drives, for example, a DC brushless motor by switching between sensor driving and sensorless driving.

  For example, there are two types of driving methods for a motor driving device provided in a DC brushless motor: a sensor driving method that uses a rotor position sensor such as a hall sensor and a sensorless driving method that generates rotor position information from an induced voltage generated in a motor coil. There is.

  The sensorless drive of a brushless DC motor has excellent characteristics that can cancel sensor errors and magnet errors, and can reduce vibration and current consumption compared to sensor drive. However, in sensorless driving, excitation switching is performed based on the induced voltage generated with the rotation of the rotor, so that the induced voltage is not generated when the rotor is stationary and it is difficult to start. Therefore, forced commutation is performed and an induced voltage generated by slight rotation of the rotor is detected and started. For example, an oscillator that oscillates at a starting frequency and a starting circuit that includes a hex ring counter are provided, and activation is performed by performing excitation based on an excitation sequence of forced commutation by a start start signal. Alternatively, at the first start, the excitation phase is energized twice to two pull-in positions that are not 180 degrees or an integer multiple of the electrical angle, and then the excitation is switched in the same way to set the commutation origin at the position where the rotor stops Then, the commutation control is performed to start the motor (see Patent Document 1).

JP 2002-291282 A

  When the motor is started by forced commutation, since the rotational speed of the rotor is small, a minute induced voltage must be handled, and a starting mistake is unavoidable, and the starting circuit is complicated. In particular, starting with a viscous load is difficult, and restraint operation that generates torque in a stationary state is also impossible. Another problem is that if the induced voltage is lost even for a moment due to noise, it will step out and not rotate continuously. Also, there are many applications that cannot be applied because the motor rotates in reverse by forced commutation or sensing energization at the start. Furthermore, the point that it takes time to detect and start the induced voltage is delayed, which is not allowed in many applications. Because of these problems, the sensorless drive has excellent characteristics, but its application is limited.

  In addition, when starting sensorless driving, it is necessary to detect a minute induced voltage on the order of several mV by forced commutation. Alternatively, even if a minute difference in inductance is detected, high frequency pulse driving is performed to detect a minute current change. In any case, a minute signal has to be handled, and a stable operation is difficult particularly in a motor drive circuit with a lot of noise. For this reason, there are many restrictions such as shortening the motor lead wire, and it is inevitable that a start error occurs. Further, there is a problem that the rotor reverses during the sensing period at the time of starting, and the sensing operation takes a time of several hundred ms to several seconds, and the starting is delayed.

  The present invention has been made to solve these problems, and an object of the present invention is to provide a sensorless drive start circuit and a start procedure while performing quick and reliable start or restraint operation or step-out prevention by sensor drive. An object of the present invention is to provide a motor drive device that can be rotated with low vibration and low current consumption by switching to sensorless drive during steady rotation.

In order to achieve the above object, the present invention comprises the following arrangement.
External sensor signal input means for inputting rotor position information output from the rotor position sensor of the motor and zero cross of 1 pulse per electrical angle by comparing the induced voltage and neutral point voltage generated in the motor coil to eliminate spike noise Zero cross detection means for detecting a signal, delay means for generating an internal sensor signal obtained by delaying the zero cross signal generated by the zero cross detection means by a predetermined electrical angle, and an external sensor input from the external sensor signal input means The sensor selection means for selecting one of the signal and the internal sensor signal generated by the delay means, and the excitation sequence stored according to the rotation command from the controller and the sensor signal selected by the sensor selection means The energized phase is determined based on the output, and the excitation switching signal is output to the motor output section. Detected by an excitation switching means for sending excitation sequence information to the pressure detection means, the motor output section for switching the energization phase based on the excitation switching signal output from the excitation switching means and energizing the motor coil, and the zero cross detection means The induced voltage determination means for determining whether or not the zero-cross signal made coincides with a theoretical value based on an excitation sequence determined by excitation sequence information from the excitation switching means (hereinafter simply referred to as “theoretical value”); The induced voltage determination means compares the zero cross signal with the theoretical value based on the excitation sequence determined by the excitation sequence information from the excitation switching means at the excitation switching timing, and the zero cross signal matches the theoretical value. If the match signal is determined to be inconsistent, the mismatch signal is determined to be inconsistent. Each output to the sensor selection means, said sensor selection means selects said internal sensor signal and receiving the coincidence signal, and selects the external sensor signal upon receipt of a mismatch signal.

According to the above configuration, the induced voltage determination means outputs the mismatch signal to the sensor selection means when it determines that the match signal is mismatched when it is determined that the zero cross signal matches the theoretical value. The sensor selection means selects the internal sensor signal when receiving the coincidence signal, and selects the external sensor signal when receiving the mismatch signal. Specifically, at the time of start-up or step-out, the zero cross signal does not match the theoretical value, so excitation switching is performed based on the output of the rotor position sensor built in the motor. As a result, when the motor is started by driving the sensor, normal excitation can be performed from a stationary state, and quick and reliable motor start and restraint operation can be performed. Further, when the motor starts rotating and an induced voltage is generated and the zero cross signal coincides with the theoretical value, the sensorless driving is switched. Thereby, steady rotation of the motor with low vibration and low current consumption can be realized.
Further, since the delay means generates an internal sensor signal for instructing the excitation switching timing obtained by delaying the zero cross signal generated by the zero cross detection means by a predetermined electrical angle, the induced voltage determination means performs the excitation switching timing after the delay. If the zero-cross signal is compared with the theoretical value, the zero-cross signal changes and is compared after the delay time has elapsed, so that a coincidence / mismatch can be determined with sufficient time margin.

The induced voltage determination means outputs a coincidence signal to the sensor selection means only when the zero cross signal of a plurality of consecutive excitation intervals coincides with the theoretical value in all excitation intervals, and the zero cross signal is the theoretical value. It is preferable to output a mismatch signal to the sensor selection means when there is a mismatch in one excitation interval.
As a result, the induced voltage determination means outputs a coincidence signal only when the zero cross signal of a plurality of consecutive excitation intervals coincides with the theoretical value in all excitation intervals, and the sensor selection means selects the internal sensor signal. The drive switching can be stably performed without malfunction when switching to the sensorless drive after the start by the sensor drive. Also, if the zero cross signal does not match the theoretical value even in one excitation interval while the motor is rotating, that is, if the induced voltage determining means loses sight of the induced voltage, a mismatch signal is output and the sensor selecting means instantly By selecting an external sensor signal, normal excitation can be performed and the motor can continue to rotate without stepping out.

  By using the motor drive device described above, a simple circuit configuration without a start circuit automatically switches between smooth and quick start by sensor drive and restraint operation and steady operation with low vibration and low current consumption by sensorless drive. It is possible to provide a motor drive device that is difficult to step out.

It is explanatory drawing which shows the circuit structure of the motor coil and sensor of a motor drive device. It is a timing chart figure of a sensor drive. It is a timing chart figure of sensorless drive. It is a switching timing chart figure of sensor drive and sensorless drive. It is a block block diagram of a motor output part. It is a block block diagram of the motor drive device for three-phase DC brushless motors. It is an output timing chart figure of a zero cross comparator. It is explanatory drawing of a coil voltage waveform and a neutral point voltage waveform.

  Hereinafter, an embodiment of a motor driving device according to the present invention will be described with reference to the accompanying drawings. Further, the following description will be made of a motor driving device for driving a three-phase DC brushless motor having a permanent magnet rotor and a stator.

An example of the motor drive device will be described. The DC brushless motor has three-phase mainstream, and the three-phase motor will be described below as an example.
FIG. 1 shows a circuit configuration of a motor coil and a sensor of a three-phase DC brushless motor with a rotor position sensor. The motor coils U-phase, V-phase, and W-phase for three phases are appropriately arranged so as to have a 120 ° phase difference in electrical angle. In this embodiment, the three-phase coil is star-connected and has U, V, W, and neutral point COMM terminals. Note that when generating a dummy neutral point signal corresponding to a neutral point on the drive circuit side, the COMM terminal can be omitted. Further, the rotor position sensors A, B, and C for three phases are appropriately arranged so as to have a phase difference of 120 ° in electrical angle. The rotor position sensors A to C detect magnetic flux that changes as the rotor rotates. In this embodiment, a Hall IC is used as the rotor position sensors A to C, and includes a Hall element, a power supply regulator, an amplifier, a Schmitt trigger gate, an output element, and the like. For example, a transistor (open collector) or FET (open drain) is used as the output element.

  The driving method of the brushless DC motor is generally a bipolar rectangular wave drive with 120 ° conduction. In this embodiment, a three-phase bipolar 120 ° rectangular wave driving method will be described as an example. This driving method includes sensor driving for determining the energization pattern from the outputs of the rotor position sensors A to C and sensorless driving for determining the energization pattern by detecting a zero cross between the coil induced voltage and the neutral point COMM terminal.

  FIG. 2 shows a sensor driving timing chart. The rotor position sensors A to C are outputs from the Hall IC that detects the rotor position. The three-phase coils U-phase to W-phase are stator windings, + in the figure is connected to the power supply, and-in the figure is connected to GND. (1) When the sensors A to C are H (high), L (low), and H (high), the coil U is energized to V and the W phase is de-energized. (2) When the sensors A to C are HLL, the coil U is energized to W and the V phase is de-energized. (3) When the sensors A to C are HHL, the coil V is energized to the W and the U phase is de-energized. (4) When the sensors A to C are LHL, the coil V is energized to the U and the W phase is de-energized. (5) When the sensors A to C are LHH, the coil W is energized to the U and the V phase is de-energized. (6) When the sensors A to C are LLH, the coil W is energized to the V and the U phase is de-energized. Energization is performed for one electrical angle by the above six-phase excitation pattern. Thereafter, sensor driving is performed by repeating the excitation sequence.

  FIG. 3 shows a timing chart of sensorless driving. COMP-A to C are comparator outputs of coil voltage and neutral point voltage. Zero-cross signals ZU to ZW are zero-cross comparator outputs of coil voltage and neutral point voltage. A spike voltage is generated at the time of excitation switching. However, in a practical circuit, spike waveform mask means is provided and the spike waveform is masked, so it does not appear in the waveform and is not shown. The three-phase coils U-phase to W-phase are stator windings, + in the figure is connected to the power supply, and-in the figure is connected to GND. The edge of the zero cross signal output from the zero cross comparator, that is, the zero cross point, and the coil energization edge, that is, the excitation switching timing, each have a phase difference of 30 ° in terms of electrical angle.

FIG. 4 shows a switching timing chart of sensor driving and sensorless driving. When a rotation command is given from the controller 1 to the drive circuit, an induced voltage is not generated and the sensor drive is selected when the motor is stationary. After the motor is started by the sensor drive, the induced voltage starts to be detected, and the sensorless drive is selected when the zero cross signal coincides with the excitation sequence (theoretical value) determined by the excitation sequence information from the excitation switching means (decoder 2). .
As described above, when the motor is started, it is started by sensor driving, and when the induced voltage is generated when the motor starts to rotate, it is switched to sensorless driving. As a result, smooth startability of the motor and steady rotation with low vibration and low current consumption are realized.

  Here, FIG. 5 and FIG. 6 show a block configuration of the motor drive circuit of the three-phase brushless DC motor. FIG. 5 is a simplified block diagram illustrating sensor drive.

  The decoder 2 (excitation switching means) stores an excitation sequence, and a rotation command from the host controller 1 and sensor signals from the three rotor position sensors A to C (Hall IC) are inputted, and the rotation command and the rotor position sensor are inputted. An energized phase is determined by a combination of A to C inputs, and an excitation switching signal is output to the output stage 3. Rotor position information output from the rotor position sensors A to C of the motor is input to the decoder 2 as external sensor signal input means. If the rotor position sensors A to C are differential outputs, a comparator is provided. Can be converted into a single-ended digital signal. The output stage 3 has a totem pole type three-phase bridge configuration using transistors or FETs, and an arbitrary pattern is energized by an excitation switching signal from the decoder 2. Motor coils U to W are connected to the outputs U to W, respectively.

  FIG. 6 shows a more detailed block diagram of the sensor / sensorless driving circuit of the three-phase brushless DC motor. The sensor selection means 4 (selector) switches between a rotor position sensor (external sensor) signal and an internal sensor signal according to an induced voltage determination signal described later. The sensor selection means 4 (selector) selects the rotor position sensor signal when it is determined that the induced voltage is not stably generated, and the internal sensor signal when it is determined that the induced voltage is stably generated. When selected, sensor driving and sensorless driving are automatically switched. The decoder 2 stores an excitation sequence, selects an excitation sequence based on a sensor signal output from the sensor selection unit 4 (selector), outputs a corresponding excitation signal to the output stage 3, and determines an induced voltage described later. An excitation switching signal indicating energization switching timing and an excitation sequence number indicating the current energization or excitation sequence information indicating the excitation phase are sent to the means 8. The output stage 3 switches a switching element (for example, a power MOSFET) based on an excitation switching signal output from the decoder 2 to excite a motor coil or apply a short brake.

  Further, the neutral point voltage generating means 5 generates a virtual neutral point voltage from the waveform of the three-phase motor coil (U phase to W phase). Specifically, the neutral point signal n can be obtained by connecting one end of three resistors to the outputs of the motor coil U-phase, V-phase, and W-phase and connecting the other end to a common connection. Moreover, the zero cross detection means 6 which compares a neutral point signal n with the output value of each phase motor coil U phase-W phase, detects a zero cross point, and produces | generates a zero cross signal is provided. The zero cross detection means 6 includes, for example, three comparators. The zero cross detecting means 6 performs a mask process for preventing a malfunction due to spike noise by holding the previous comparator output value for a certain period of time when switching the excitation. The excitation switching edge can be detected by the decoder 2, and mask processing is started based on the excitation switching detection signal.

  The delay means 7 generates an excitation signal (internal sensor signal) that delays the zero-cross signals ZU to ZW generated by the zero-cross detection means 6 by an electrical angle by 30 ° to generate energization timing. The induced voltage determination means 8 compares the zero cross signal with the excitation sequence (theoretical value) determined by the excitation sequence information sent from the decoder 2 from the excitation sequences stored in advance, and induces an induced voltage in the motor coil. It is determined whether or not the problem occurs stably. When it does not coincide with the zero cross signal, that is, when it is determined that the induced voltage is not generated normally, a mismatch signal for selecting the external sensor signal is selected, and when it matches, a match signal for selecting the internal sensor signal is displayed. To the selector).

  With the above configuration, switching between sensor driving and sensorless driving can be performed automatically, and the load on the host controller can be reduced. Further, reliable startability by sensor driving can be obtained, and smooth rotation performance with less vibration can be obtained by reducing the influence of rotor position sensor error and rotor magnet magnetization error by sensorless driving.

  Here, the determination method of the induced voltage determination means 8 will be described. Since the excitation sequence is uniquely determined, it is possible to determine an induced voltage detection error by determining whether the zero-cross signal matches a theoretical value based on the excitation sequence stored in advance. Since the zero cross signal is advanced 30 ° in electrical angle from the excitation switching timing, comparing the zero cross signal with the theoretical value at the excitation switching timing after the delay, it is possible to reliably determine the coincidence / mismatch with sufficient time margin. it can. In addition, the transition from the sensor drive to the sensorless drive can be performed more stably if it is performed after the theoretical values coincide with each other in a plurality of continuous excitation intervals. For example, in the case of three-phase full-wave drive, the sensor drive may be shifted to the sensorless drive if the theoretical value coincides with six excitation intervals. According to this configuration, for example, even if one excitation section coincides with noise, switching between sensor driving and sensorless driving does not occur, and malfunction can be prevented. It should be noted that there is no problem even if the transition from sensor driving to sensorless driving is delayed by about one electrical angle. On the other hand, if there is a discrepancy with the theoretical value even in one excitation interval, the sensorless drive is immediately shifted to the sensor drive. As a result, when the induced voltage determining means 8 loses sight of the induced voltage, it can instantaneously carry out normal excitation with an external sensor signal and continue the rotation without stepping out.

  FIG. 7 illustrates a comparator output (zero cross signal) provided in the zero cross detecting means 6 by a timing chart. The induced voltage determination means 8 determines whether or not the zero cross signal is normal by comparing the value of the zero cross signal with a theoretical value based on an excitation sequence stored in advance at the excitation switching timing. The excitation sequence number to be compared can be received from the decoder. When the comparator output is coded with weights of ZU = 2 ^ 0, ZV = 2 ^ 1, ZW = 2 ^ 2, the code is 5-1-3-2-6-4 in synchronization with excitation switching in the normal state. Proceed with Therefore, for example, if the current code value is 5, it can be predicted that the next code value is 1. Therefore, if the code value of the zero cross signal is 1 at the next excitation switching, it can be determined that the induced voltage has been detected normally, and if it is other than 1, it can be determined that it is not normal. Similarly, all the energization timings can be determined by determining 3, 2, 6, 4 and 5 as well.

  In addition, an analog comparison is made between the neutral point voltage and the potential difference between the non-energized coil, and it can be determined whether or not the threshold level is exceeded. The magnitude of the induced voltage to be detected can be determined based on the threshold voltage setting value, and the switching speed of switching between sensor driving and sensorless driving can be selected. FIG. 8 shows a coil voltage waveform and a neutral point voltage waveform. In the case of 120 ° rectangular wave drive, each coil has two non-energized sections of 60 ° per electrical angle. At the time of excitation switching, a mask interval of a certain time is provided in order to remove spike noise. The determination section is a time zone obtained by removing the mask section from the non-energized section. The neutral point voltage is a small-amplitude triangular wave whose gradient changes in each excitation interval, but is displayed as a straight line for easy understanding. Threshold voltages are set on the H side and L side with respect to the neutral point voltage. If the threshold voltage H is equal to or higher than the threshold voltage L or lower than the threshold voltage L within the determination interval, it is determined that an induced voltage is generated. If the above operation is performed on three coils, it can be determined whether or not an induced voltage is generated throughout the entire energization period.

  By using the motor drive device described above, smooth and quick start by sensor drive with a simple circuit configuration without a start circuit, restraint operation by sensor signal and steady operation by low vibration and low current consumption by sensorless drive mutually. It is possible to provide a motor drive device that is not easily stepped out. In sensorless driving, excitation switching is performed based on the induced voltage, and the magnetizing error of the rotor position sensor and the magnet can be canceled. In addition, since the induced voltage reflects torque, excitation with less torque ripple is possible, resulting in low current consumption and reduced vibration. Therefore, the DC brushless motor can be reliably started and, at the normal time, a low-current operation with low current consumption can be achieved by sensorless driving. In addition, although the three-phase DC brushless motor was illustrated, it is also possible to apply to another multiphase brushless motor.

A to C Rotor position sensor 1 Controller 2 Decoder 3 Output stage 4 Sensor selection means 5 Neutral point voltage generation means 6 Zero cross detection means 7 Delay means 8 Induced voltage determination means

Claims (2)

External sensor signal input means for inputting rotor position information output from the rotor position sensor of the motor;
Zero cross detection means that compares the induced voltage generated in the motor coil with the neutral point voltage to eliminate spike noise and detect one pulse of zero cross signal per electrical angle;
A delay means for generating an internal sensor signal obtained by delaying the zero cross signal generated by the zero cross detection means by a predetermined electrical angle;
Sensor selection means for selecting one of the external sensor signal input from the external sensor signal input means and the internal sensor signal generated by the delay means;
Based on the rotation command from the controller and the excitation sequence stored in accordance with the sensor signal selected by the sensor selection means, the energization phase is determined, the excitation switching signal is output to the motor output section, and the excitation voltage detection means is excited. Excitation switching means for sending sequence information;
The motor output unit for energizing the motor coil by switching the energized phase based on the excitation switching signal output from the excitation switching means;
The induced voltage determination means for determining whether or not the zero cross signal detected by the zero cross detection means matches a theoretical value based on an excitation sequence determined by excitation sequence information from the excitation switching means;
The induced voltage determination means compares a zero cross signal with an excitation switching timing and a theoretical value based on an excitation sequence determined by excitation sequence information from the excitation switching means, and the zero cross signal matches the theoretical value. If it is determined that the coincidence signal is determined to be non-coincidence, the non-coincidence signal is output to the sensor selection unit. The sensor selection unit receives the coincidence signal, selects the internal sensor signal, and receives the non-coincidence signal. And a motor driving device for selecting the external sensor signal.   The induced voltage determination means is a coincidence signal only when the zero-cross signal of a plurality of consecutive excitation intervals matches the theoretical value based on the excitation sequence determined by the excitation sequence information from the excitation switching means in all excitation intervals. The motor drive device according to claim 1, wherein when the zero cross signal does not match the theoretical value even in one excitation interval, a mismatch signal is output to the sensor selection means.

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