CN111585479A - Three-phase sensorless brushless direct current motor control system - Google Patents
Three-phase sensorless brushless direct current motor control system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/15—Controlling commutation time
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/18—Indicating phase sequence; Indicating synchronism
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
- H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/20—Arrangements for starting
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Abstract
A three-phase sensorless brushless direct current motor control system comprises a driving controller and a zero-crossing detection circuit, wherein three-phase signals output by a motor are respectively input to the input end of the zero-crossing detection circuit and are converted into feedback signals containing zero-crossing information, the driving controller outputs motor control signals according to the feedback signals of the zero-crossing detection circuit, and the three-phase sensorless brushless direct current motor control system further comprises a phase compensation circuit, wherein the phase compensation circuit outputs PWM (pulse-width modulation) waveforms, so that the zero-crossing points of the output feedback signals and phase change points of the three-phase signals output by the motor. The invention directly carries out source compensation on the zero-crossing signal by using the phase compensation circuit, so that the signal obtained after AD acquisition and comparison is the real phase-change signal, and the compensation time can be more conveniently adjusted by using the controller to output PWM.
Description
Technical Field
The invention belongs to the field of brushless direct current motor control, and relates to a three-phase sensorless brushless direct current motor control system.
Background
The brushless direct current motor (BLDC) uses an electronic commutator to replace a traditional mechanical commutator, not only has the characteristics of good speed regulation performance, dynamic performance and the like of the direct current motor, but also has the advantages of simple structure, no commutation spark, reliable operation, easy maintenance and the like of the alternating current motor.
The BLDC without the position sensor can not only avoid the limitations of the position sensor, such as cost, sensor lead wires and damage, to influence the reliability, but also enlarge the application range of the brushless DC motor, for example, the BLDC can not adapt to the requirements of the whole machine due to the position sensor in some occasions with strict size.
For the reasons, the research on the BLDC driving technology without the position sensor has extremely important significance and application prospect. Although the sensorless has the advantages of simple structure, stable operation and the like, the driving circuit is relatively complex, and particularly, how to judge the position of the rotor at zero start and adaptively adjust the load condition at start becomes a popular research.
The conventional start-up scheme is: prepositioning- > open-loop acceleration- > cutting into a closed loop according to a predetermined acceleration curve. The traditional starting algorithm is suitable for the specific occasions of fixed motors and fixed loads. If the occasions that the starting is required to be frequent and rapid exist, the traditional starting algorithm is subject to failure.
Large companies such as TI and ST have a Field-Oriented Control (FOC) technical solution, but have a problem that the effect is ideal if the motor is started in an idle state or in a light state, but have problems of jitter and step-out if the motor is started in a heavy state. In addition, the controller cost required to use a FOC is also high.
Besides using the FOC scheme, many technical schemes also describe a square wave control scheme, which can detect the back electromotive force earlier and enter a back electromotive force closed loop earlier because the back electromotive force is detected during the PWM off period at the time of starting. However, since the open loop is performed at the time of starting, there is a possibility that the step-out jitter may occur once the load is changed or the belt is running again.
Except for reliable starting, if the motor meets an emergency or the situation that the stop time of the motor is required during running, the motor needs to be quickly braked to be zero in the running process. The common braking scheme is that when the controller runs, an independent one-way braking circuit performs braking control on the motor. This does not meet some requirements that require power-down braking. For the implementation of power-down braking, many schemes in the market are implemented by using a time delay relay. However, the delay relay brings about an increase in the volume and a cost.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention discloses a three-phase sensorless brushless direct current motor control system.
The invention discloses a three-phase sensorless brushless direct current motor control system, which comprises a drive controller and a zero-crossing detection circuit, wherein the input end of the zero-crossing detection circuit respectively inputs three-phase signals output by a motor and converts the three-phase signals into feedback signals containing zero-crossing information, and the drive controller outputs motor control signals according to the feedback signals of the zero-crossing detection circuit.
Preferably, the zero-crossing detection circuit comprises three detection branches, each detection branch comprises a pre-filter, a first follower of which the input end is connected with the output end of the filter, and a rear-end filter connected with the output end of the first follower, the phase compensation circuit is connected to a compensation point between the output end of the pre-filter and the input end of the first follower, and the output end of the first follower is used as a feedback signal output end;
the compensation points of the three detection branches are respectively connected with a virtual midpoint through virtual midpoint generating resistors, the virtual midpoint is connected with the input end of a second follower, and the output end of the second follower is used as a virtual midpoint voltage output end.
Preferably, the compensation point of one of the detection branches is connected with a power supply pull-up circuit.
Preferably, the phase compensation circuit includes a compensation signal generation circuit that generates a pair of mutually inverted PWM waveforms, and a first switching circuit and a second switching circuit connected at a compensation point;
the first switch circuit comprises a first switch device connected between the compensation point and the ground, and the control end of the first switch device is connected with the positive phase input end of the compensation signal generation circuit;
the second switching circuit comprises a compensation capacitor, a compensation resistor and a second switching device which are connected between a compensation point and the ground in series, and the control end of the second switching device is connected with the inverting input end of the compensation signal generating circuit;
the values of the compensation capacitor and the compensation resistor satisfy the following formula:
tan theta = -2 pi fRC, where theta is the phase compensation angle and f is the compensation signal frequency.
Preferably, the compensation signal generation circuit is a comparator.
Preferably, the front-end filter and/or the back-end filter include two voltage dividing resistors connected between the input end of the filter and ground, and a filter capacitor is connected between a common end of the two voltage dividing resistors and ground.
Preferably, the power-down brake device further comprises a power-down brake module and a linear voltage stabilizing module for supplying power to the driving controller, wherein the power-down brake module is in signal connection with the driving controller and is in control connection with an enabling end of the linear voltage stabilizing module;
the power-down brake module comprises an NPN tube connected between a power supply and the ground, a collector resistor is connected in series between a collector of the NPN tube and the power supply, the power-down brake module further comprises a PNP tube, a base of the PNP tube is connected with the collector of the NPN tube, an emitter of the PNP tube is connected with the power supply, the emitter of the PNP tube is also connected with an enabling end of the linear voltage stabilizing module through a power-off start-stop switch and a first diode, the collector of the PNP tube is connected with the enabling end of the linear voltage stabilizing module through a second diode, and cathodes of the two diodes are connected;
the power-off start-stop switch and the common end of the first diode are connected with a power supply voltage acquisition end of the driving controller through a divider resistor, and the base of the NPN tube is connected with an interrupt signal output end of the driving controller.
Preferably, the power supply voltage acquisition end is connected with an ESD protection diode.
Preferably, the power supply voltage acquisition end is connected with a filter capacitor and a divider resistor.
The three-phase sensorless brushless direct current motor control system has the following advantages:
1. a BEMF zero-crossing detection principle is used, a zero-crossing detection circuit is set up, and a controller carries out real-time sampling calculation on the signal conditioned by the three-phase BEMF and the neutral point potential signal. As long as there is a slight rotation of the motor, its BEMF zero crossing is detected. That is, the starting from zero speed is in the closed loop state. Closed loop startup can be guaranteed.
2. The phase compensation circuit is used for directly performing source compensation on the BEMF zero-crossing signal, so that the signal obtained after AD acquisition and comparison is the real phase-change signal, and the controller is used for outputting PWM (pulse width modulation), so that the compensation time can be adjusted more conveniently.
3. Compared with the traditional hardware comparator for comparing signals, the AD acquisition device has the advantages that the filtering time can be adjusted more quickly through the configuration of software, and the filtering algorithm can be corrected more conveniently. The method can acquire the phase change point of the motor more truly, so that the phase change is more accurate, and the method can achieve the quick start without jitter and smoothness even with variable load and large load start.
4. The power-down brake circuit, the components and the circuit characteristics used by the power-down brake circuit have great advantages in cost, and the small leakage current of the power-down brake circuit has more advantages than a time delay relay.
Drawings
Fig. 1 is a schematic diagram of an embodiment of a three-phase sensorless brushless dc motor control system according to the present invention.
FIG. 2 is a diagram illustrating an embodiment of a zero-crossing detection module and a phase compensation module according to the present invention, wherein the rectangular devices not labeled in FIG. 2 represent resistors;
FIG. 3 is a schematic diagram of the motor feedback voltage signal and the output motor control signal and zero crossing signal of the present invention before uncompensation;
FIG. 4 is a schematic diagram of the compensated motor feedback voltage signal and the output motor control signal and zero crossing signal of the present invention;
FIG. 5 is a schematic diagram of an embodiment of a power-down brake module according to the present invention;
the reference numbers in the figures refer to: the brushless direct current motor comprises a BLDC (brushless direct current), a T1-first switching device, a T2-second switching device, a C1-front-end filter capacitor, a C2-rear-end filter capacitor, a U1-first follower, a U2-second follower, a U3-comparator, a C3-compensation capacitor, a R1-compensation resistor and a R2-virtual midpoint generation resistor;
the ESD protection circuit comprises a Q1-NPN tube, a Q2-PNP tube, an S1-power-off start-stop switch, a D1-first diode, a D2-second diode and a D3-ESD protection diode.
Detailed Description
The following provides a more detailed description of the present invention.
The invention discloses a three-phase sensorless brushless direct current motor control system, which comprises a drive controller and a zero-crossing detection circuit, wherein the input end of the zero-crossing detection circuit respectively inputs three-phase signals output by a motor and converts the three-phase signals into feedback signals containing zero-crossing information, and the drive controller outputs motor control signals according to the feedback signals of the zero-crossing detection circuit.
An exemplary embodiment of the control system of the present invention is shown in fig. 1, and includes a dc power input module, a linear voltage regulator circuit, a power-down brake circuit, a driving controller, a gate driving module, a three-phase driving module, a zero-crossing detection module, a phase compensation module, and a brushless dc motor (BLDC). Except an electric brake circuit and a phase compensation module, other modules and connection relations thereof are mature prior art in the field, and the specific working principle is as follows: the direct-current power supply input module is connected with the linear voltage stabilizing circuit, the IGBT module and the power-down brake circuit and provides power supply for the linear voltage stabilizing circuit, the IGBT module and the power-down brake circuit; the linear voltage stabilizing circuit and the direct-current power supply input module input the converted and output direct-current voltage into the grid drive module to provide power supply, and the power-down brake circuit is connected with the drive controller; the drive controller is also connected with the grid drive module, the zero-crossing detection module and the phase compensation module, and converts signals obtained by the zero-crossing detection module into grid drive signals; the grid driving module is usually formed by connecting a plurality of cascaded inverters in series, so that the subsequent output driving capability is improved, and a driving signal is provided for the three-phase driving module; the zero crossing detection module is connected with three phases U, V, W of the brushless dc motor. The phase compensation module performs phase compensation for the zero-crossing detection module and obtains a square wave signal for phase compensation from a PWM output pin of the driving controller.
As shown in fig. 2, the input of the zero-crossing detection circuit is a three-phase input U, V, W terminal of the brushless dc motor, the zero-crossing detection circuit includes three detection branches, each of which includes a pre-filter, a first follower whose input terminal is connected to the output terminal of the filter, and a back-end filter connected to the output terminal of the first follower, the phase compensation circuit is connected to a compensation point between the output terminal of the pre-filter and the input terminal of the first follower, and the output terminal of the first follower serves as a feedback signal output terminal. The zero-crossing detection of the U-phase is exemplified.
The U-phase voltage signal MOTOR _ U is filtered by a front-end filter and then is connected to a first follower for voltage following, the output voltage signal is filtered by a rear-end filter, and the obtained voltage signal is input to a U-phase acquisition port AD _ U port corresponding to the driving controller for acquisition processing.
A pull-up branch may be provided in a certain detection branch, and as shown in the specific embodiment shown in fig. 2, the compensation point of the U-phase detection branch is connected to a power supply pull-up circuit, which is composed of three resistors. And applying a signal obtained by dividing the power supply voltage VDD, wherein the signal is obtained by pulling up the U-phase voltage initially, namely, the default initial power-on phase sequence is the UV or UW phase, and if other detection branches are connected, the power-on phase sequence is correspondingly changed.
Since the collected ac voltage is generally high and the detection voltage of various precision devices such as comparators and controllers for internal detection is low, in the specific embodiment shown in fig. 2, the front-end filter and/or the back-end filter includes two voltage dividing resistors connected between the input end of the filter and ground, and a filter capacitor is connected between the common end of the two voltage dividing resistors and ground.
The phase compensation circuit comprises a compensation signal generation circuit for generating a pair of mutually inverted PWM waveforms, and a first switch circuit and a second switch circuit which are connected at a compensation point; PWM, a pulse width modulated signal, is compensated by outputting a square wave signal with a varying duty cycle.
The first switch circuit comprises a first switch device connected between the compensation point and the ground, and the control end of the first switch device is connected with the positive phase input end of the compensation signal generation circuit;
the second switch circuit comprises a compensation capacitor C3, a compensation resistor R1 and a second switch device which are connected between a compensation point and the ground in series, and the control end of the second switch device is connected with the inverting input end of the compensation signal generating circuit;
the values of the compensation capacitor and the compensation resistor satisfy the following formula:
tan theta = -2 pi fRC, where theta is the phase compensation angle and f is the compensation signal frequency.
As shown in fig. 2, the first switching device and the second switching device are NPN triodes, the collector and the emitter are respectively connected between the compensation point and ground, and the base and the collector can also be respectively connected in series with a base resistor and a collector resistor. The compensation signal is generated by the driving controller, and is usually a square wave with a 50% duty ratio, the compensation signal generating circuit in fig. 2 is a comparator, the power voltage is divided by a resistor to be used as the reference voltage of the comparator, the compensation signal is input from the reverse input end of the comparator, a square wave signal which is in reverse phase with the input signal is output, and the compensation signals before and after the reverse phase are respectively connected with the control ends of the first switching device and the second switching device, namely the base electrodes of the NPN transistors.
As shown in fig. 3 or 4, the MOTOR feedback voltage signal MOTOR _ U, MOTOR _ V, MOTOR _ W collected from each phase of the brushless dc MOTOR includes a lower frequency substantially sinusoidal vibration and a higher frequency substantially square wave vibration, i.e., a composite waveform formed by combining a high frequency vibration and a low frequency vibration, the operating frequency of the compensation signal is identical to the frequency of the high frequency vibration signal of the MOTOR feedback voltage signal collected from each phase of the brushless dc MOTOR, and the first switching device is used for filtering the high frequency signal which cannot be processed by the pre-filter by periodically pulling down the compensation signal. The second switch device and the compensation capacitor and the compensation resistor which are connected in series with the second switch device generate time delay to enable the phase of the input motor feedback voltage signal to deviate, and the phase compensation angle is equal to the phase difference value between the motor feedback voltage signal before uncompensation and the output motor control signal.
As shown in fig. 3 and 4, MOTOR _ U, MOTOR _ V, MOTOR _ W respectively represents a MOTOR feedback voltage signal reversely fed back from the brushless dc MOTOR U, V, W, and AD _ U, AD _ V, AD _ W respectively represents a MOTOR control signal output to the drive controller after zero-crossing detection, where abscissa in the figure is time and ordinate is voltage.
As can be seen from fig. 3 and 4, before uncompensated, there is a time difference between a phase inversion point of the three-phase MOTOR feedback voltage signal MOTOR _ U, MOTOR _ V, MOTOR _ W and a zero crossing point of the corresponding control signal AD _ U, AD _ V, AD _ W, resulting in a 30-degree phase difference, wherein the zero crossing point is generated by comparing the control signal AD _ U, AD _ V, AD _ W with the virtual midpoint voltage AD _ N, and the voltage comparison is performed by an internally integrated ADC or comparator in the drive controller.
After the phase compensation circuit is adopted to delay the motor feedback voltage signal, as shown in fig. 4, the commutation point and the zero crossing point tend to coincide, and in the subsequent control processing process, the commutation point of the motor can be more really obtained, so that commutation is more accurate, and the motor can be started quickly without jitter and smoothly even with variable load and large load. Compared with a software compensation mode, the delay time of the circuit compensation mode is directly related to the frequency of the compensation signal, so that the filtering time can be adjusted more quickly and the filtering algorithm can be corrected more conveniently through the configuration of software.
The virtual midpoint voltage AD _ N for generating the reference for determining whether to cross the zero point as shown in fig. 3 and 4 is generated by a virtual midpoint circuit, as shown in fig. 2, the compensation points of the three detection branches are respectively connected with a virtual midpoint through virtual midpoint generating resistors, the virtual midpoint is connected with the input end of a second follower, the output end of the second follower is used as the output end of the virtual midpoint voltage, the resistance values of the resistors generated by the virtual midpoints connected with the compensation points are equal, the resistance value is generally above 10K, the virtual midpoint voltage is obtained by averaging three-phase signals, the virtual midpoint voltage is an analog voltage value having high-frequency noise but with an approximately fixed mean value in a long period, and is approximately processed as a constant value in fig. 3 and 4.
In the specific embodiment shown in fig. 1 and 5, the control system of the present invention further includes a power-down brake module and a linear voltage stabilizing module for supplying power to the driving controller, wherein the power-down brake module is in signal connection with the driving controller and is in control connection with an enable end of the linear voltage stabilizing module;
the power-down brake module comprises an NPN tube connected between a power supply and the ground, a collector resistor is connected in series between a collector of the NPN tube and the power supply, the power-down brake module further comprises a PNP tube, a base of the PNP tube is connected with the collector of the NPN tube, an emitter of the PNP tube is connected with the power supply, the emitter of the PNP tube is also connected with an enabling end of the linear voltage stabilizing module through a power-off start-stop switch and a first diode, the collector of the PNP tube is connected with the enabling end of the linear voltage stabilizing module through a second diode, and cathodes of the two diodes are connected;
the power-off start-stop switch and the common end of the first diode are connected with a power supply voltage acquisition end of the driving controller through a divider resistor, and the base of the NPN tube is connected with an interrupt signal output end of the driving controller.
When the motor normally works, the power-off start-stop switch S1 is closed, the power supply voltage VIN is divided by the divider resistor to obtain a power supply voltage acquisition SIGNAL AD _ VIN, the SIGNAL is input to a power supply voltage acquisition end of the controller, namely an AD acquisition port, the controller acquires the SIGNAL, and if the acquired voltage is in an input range, namely under the condition of no overvoltage or undervoltage, the controller enables each unit module to start working and pulls up the SIGNAL level of the interrupt SIGNAL BRK _ SIGNAL. At this time, the NPN transistor Q1 and the PNP transistor Q2 are both in a conducting state, and the linear voltage regulator module outputs a working power supply required for the operation of each module, such as the digital power supply voltage VDD and the analog voltage VCC in fig. 5, and each module operates normally.
When the abnormal condition needs power-down braking, the power-off start-stop switch S1 is turned off at the moment, the power supply voltage acquisition signal AD _ VIN acquired by the controller is rapidly reduced to 0, the event is taken as a mark that a user turns off the switch, when the controller detects that the AD _ VIN is reduced to 0, the controller turns off the output driving signal, the common processing mode is that the pull-down tubes of all levels of phase inverters of the three-phase driving module are all opened, the pull-up tubes are all closed, the driving signal output by the driver maintains low level, and at the moment, motor braking can be realized at the fastest speed.
When the controller detects that the AD _ VIN SIGNAL is turned from high to low and maintains the low level for a certain time, the controller pulls down the BRK _ SIGNAL SIGNAL, at the moment, the NPN tube Q1 and the PNP tube Q2 are both cut off, the enable end SIGNAL of the linear voltage stabilizing module is disabled, the linear voltage stabilizing module stops working and does not output a working power supply, and all other modules also stop working. The power failure brake module can be regarded as basically having no power consumption when the power failure occurs because the leakage current of the Q1 is small when the power failure brake module is cut off, the two diodes realize the unidirectional transmission of the switching signals, and in the specific implementation mode shown in figure 5, the power supply voltage acquisition end is connected with the two ESD protection diodes D3 and the filtering capacitor.
The three-phase sensorless brushless direct current motor control system has the following advantages:
1. a BEMF zero-crossing detection principle is used, a zero-crossing detection circuit is set up, and a controller carries out real-time sampling calculation on the signal conditioned by the three-phase BEMF and the neutral point potential signal. As long as there is a slight rotation of the motor, its BEMF zero crossing is detected. That is, the starting from zero speed is in the closed loop state. Closed loop startup can be guaranteed.
2. The phase compensation circuit is used for directly performing source compensation on the BEMF zero-crossing signal, so that the signal obtained after AD acquisition and comparison is the real phase-change signal, and the controller is used for outputting PWM (pulse width modulation), so that the compensation time can be adjusted more conveniently.
3. Compared with the traditional hardware comparator for comparing signals, the AD acquisition device has the advantages that the filtering time can be adjusted more quickly through the configuration of software, and the filtering algorithm can be corrected more conveniently. The method can acquire the phase change point of the motor more truly, so that the phase change is more accurate, and the method can achieve the quick start without jitter and smoothness even with variable load and large load start.
4. The power-down brake circuit, the components and the circuit characteristics used by the power-down brake circuit have great advantages in cost, and the small leakage current of the power-down brake circuit has more advantages than a time delay relay.
The foregoing is a description of preferred embodiments of the present invention, and the preferred embodiments in the preferred embodiments may be combined and combined in any combination, if not obviously contradictory or prerequisite to a certain preferred embodiment, and the specific parameters in the examples and the embodiments are only for the purpose of clearly illustrating the inventor's invention verification process and are not intended to limit the patent protection scope of the present invention, which is defined by the claims and the equivalent structural changes made by the content of the description of the present invention are also included in the protection scope of the present invention.
Claims (9)
1. A three-phase sensorless brushless direct current motor control system comprises a drive controller and a zero-crossing detection circuit, wherein three-phase signals output by a motor are respectively input to the input end of the zero-crossing detection circuit and are converted into feedback signals containing zero-crossing information, and the drive controller outputs motor control signals according to the feedback signals of the zero-crossing detection circuit.
2. The control system of claim 1, wherein the zero-crossing detection circuit comprises three detection branches, each detection branch comprising a pre-filter and a first follower having an input connected to the output of the filter, and a post-filter connected to the output of the first follower, the phase compensation circuit being connected to a compensation point between the output of the pre-filter and the input of the first follower, the output of the first follower serving as the feedback signal output;
the compensation points of the three detection branches are respectively connected with a virtual midpoint through virtual midpoint generating resistors, the virtual midpoint is connected with the input end of a second follower, and the output end of the second follower is used as a virtual midpoint voltage output end.
3. The control system of claim 1, wherein the compensation point of one of the sensing branches is connected to a power pull-up circuit.
4. The three-phase sensorless brushless dc motor control system of claim 2, wherein the phase compensation circuit includes a compensation signal generation circuit that generates a pair of mutually inverted PWM waveforms, and a first switching circuit and a second switching circuit connected at a compensation point;
the first switch circuit comprises a first switch device connected between the compensation point and the ground, and the control end of the first switch device is connected with the positive phase input end of the compensation signal generation circuit;
the second switching circuit comprises a compensation capacitor, a compensation resistor and a second switching device which are connected between a compensation point and the ground in series, and the control end of the second switching device is connected with the inverting input end of the compensation signal generating circuit;
the values of the compensation capacitor and the compensation resistor satisfy the following formula:
tan theta = -2 pi fRC, where theta is the phase compensation angle and f is the compensation signal frequency.
5. The three-phase sensorless brushless dc motor control system of claim 2 wherein the compensation signal generation circuit is a comparator.
6. The control system of claim 2, wherein the pre-filter and/or the post-filter comprises two voltage dividing resistors connected between the input terminal of the filter and ground, and a filter capacitor is connected between a common terminal of the two voltage dividing resistors and ground.
7. The control system of claim 1, further comprising a power-down brake module and a linear voltage stabilization module for supplying power to the driving controller, wherein the power-down brake module is in signal connection with the driving controller and is in control connection with an enable end of the linear voltage stabilization module;
the power-down brake module comprises an NPN tube connected between a power supply and the ground, a collector resistor is connected in series between a collector of the NPN tube and the power supply, the power-down brake module further comprises a PNP tube, a base of the PNP tube is connected with the collector of the NPN tube, an emitter of the PNP tube is connected with the power supply, the emitter of the PNP tube is also connected with an enabling end of the linear voltage stabilizing module through a power-off start-stop switch and a first diode, the collector of the PNP tube is connected with the enabling end of the linear voltage stabilizing module through a second diode, and cathodes of the two diodes are connected;
the power-off start-stop switch and the common end of the first diode are connected with a power supply voltage acquisition end of the driving controller through a divider resistor, and the base of the NPN tube is connected with an interrupt signal output end of the driving controller.
8. The control system of claim 8, wherein an ESD protection diode is connected to the supply voltage pickup terminal.
9. The control system of claim 8, wherein the power voltage collection terminal is connected to a filter capacitor and a voltage divider resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010391341.1A CN111585479A (en) | 2020-05-11 | 2020-05-11 | Three-phase sensorless brushless direct current motor control system |
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Cited By (1)
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| CN117054730A (en) * | 2023-10-11 | 2023-11-14 | 拓尔微电子股份有限公司 | Zero-crossing detection circuit, motor driving circuit and zero-crossing detection method |
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