AC asynchronous motor and stepless speed regulation circuit and method thereof

Abstract

The present invention provides an AC asynchronous motor and a stepless speed regulation circuit and method thereof. An input AC sinusoidal voltage with positive and negative half cycles is rectified into a unipolar DC voltage through a rectifier circuit. No filtering is performed after rectification, so that the rectified voltage is a DC steamed wave with a frequency twice that of a power supply. Then, a pulse width modulation is performed on the steamed wave DC voltage of half a cycle through an H-bridge drive circuit. When a zero-crossing signal arrives, the pulse width modulation is stopped. After the zero-crossing signal has passed, the H-bridge arm is switched to perform pulse width modulation on another half cycle. In this way, the phase is repeatedly switched with the zero-crossing signal as a dividing point, and finally an AC voltage with a sinusoidal profile that has been pulse-width modulated is synthesized on the load, thereby solving the problems of high cost, voltage distortion and reduced power factor in the prior art for speed regulation of motors.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and in particular to an AC asynchronous motor and a stepless speed regulation circuit and method thereof. Background Art

[0002] AC asynchronous motors are widely used in industrial equipment and various household appliances. In the field of household appliances, they are commonly used in electric fans, air conditioners, air purifiers, dehumidifiers and other electrical equipment. No matter which field they are used in, they need to face the problem of speed regulation. There are many ways to regulate the speed of AC asynchronous motors. The traditional speed regulation methods are usually the following:

[0003] (1) Multiple taps are set in the motor windings, and the external control circuit switches the windings through electronic or mechanical switches such as relays and thyristors to achieve the purpose of speed regulation.

[0004] (2) An inductor with multiple taps is connected in series in the power supply circuit of the motor, and the windings are switched using electronic or mechanical switches to achieve the speed regulation effect by connecting different inductors in series.

[0005] (3) Use bidirectional thyristor to control the conduction angle to achieve speed regulation.

[0006] For (1) and (2), since the motor adopts a multi-tap method, the process of winding the motor coil is relatively complicated. At the same time, for the lower speed gear, the winding needs to be wound with more turns, so more copper wire will be used, and the cost of the motor is relatively high. At the same time, the gear switching circuit also requires more control paths, so the cost of the control circuit is also relatively high. For (3), since the thyristor is used to adjust the conduction angle, the voltage supplied to the motor winding is not a complete sine wave voltage, but an incomplete waveform that is cut off from the zero point to the conduction angle. The voltage wave has a large distortion and a high harmonic component. The power factor will drop significantly. The motor will generate a high electromagnetic sound when running. For electrical appliances that need to be used at night, it will affect people's sleep quality.

[0007] In view of this, this application is filed. Summary of the invention

[0008] The invention discloses an AC asynchronous motor and a stepless speed regulation circuit and method thereof, aiming to solve the problems of high cost, voltage distortion and power factor reduction in the speed regulation of the motor in the prior art.

[0009] The first embodiment of the present invention provides a stepless speed regulation circuit for an AC asynchronous motor, comprising: a controller, a rectifier circuit, a zero-crossing detection circuit, an H-bridge drive circuit, a first drive circuit, a second drive circuit, a first electronic switch, and a second electronic switch;

[0010] The input end of the rectifier circuit is used to connect to an AC power supply, the output end of the rectifier circuit is electrically connected to the input end of the zero-crossing detection circuit, and the output end of the zero-crossing detection circuit is electrically connected to the input end of the controller;

[0011] The output end of the rectifier circuit is electrically connected to the input end of the H-bridge drive circuit, and the output end of the H-bridge drive circuit is used to connect to the AC asynchronous motor;

[0012] The first phase signal output terminal of the controller is electrically connected to the first control terminal of the H-bridge drive circuit through the first drive circuit, and the second phase signal output terminal of the controller is electrically connected to the second control terminal of the H-bridge drive circuit through the second drive circuit;

[0013] The driving signal output terminal of the controller is electrically connected to the input terminal of the first driving circuit through the first electronic switch, and the driving signal output terminal of the controller is electrically connected to the input terminal of the second driving circuit through the second electronic switch.

[0014] Preferably, the H-bridge driving circuit comprises: a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, and a first resistor;

[0015] The first end of the first resistor is electrically connected to the output end of the rectifier circuit, the D pole of the first MOS tube and the D pole of the second MOS tube are electrically connected to the second end of the first resistor, the S pole of the first MOS tube is electrically connected to the D pole of the third MOS tube, the S pole of the second MOS tube is electrically connected to the D pole of the fourth MOS tube, and the S pole of the third MOS tube is electrically connected to the S pole of the fourth MOS tube;

[0016] The output end of the first driving circuit is electrically connected to the G pole of the first MOS tube and the G pole of the third MOS tube, and the output end of the second driving circuit is electrically connected to the G pole of the second MOS tube and the G pole of the fourth MOS tube.

[0017] Preferably, the zero-crossing detection circuit comprises: a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a first transistor;

[0018] The output end of the rectifier circuit is electrically connected to the first end of the second resistor, the second end of the second resistor is electrically connected to the first end of the third resistor, the second end of the third resistor is electrically connected to the B pole of the first transistor through the fourth resistor, the B pole of the first transistor is grounded through the fifth resistor, the E pole of the first transistor is grounded, the C pole of the first transistor is connected to the power supply through the sixth resistor, and the C pole of the first transistor is electrically connected to the input end of the controller.

[0019] Preferably, the first driving circuit comprises: a first driving chip, a first diode, a seventh resistor, an eighth resistor, and a first capacitor;

[0020] The HO terminal of the first driver chip is electrically connected to the G pole of the first MOS tube through the seventh resistor, the LO terminal of the first driver chip is electrically connected to the G pole of the third MOS tube through the eighth resistor, the VB terminal of the first driver chip is electrically connected to the S pole of the first MOS tube through the first capacitor, the VS terminal of the first driver chip is electrically connected to the S pole of the first MOS tube and the D pole of the third MOS tube, and the VS terminal of the first driver chip is electrically connected to the input terminal of the AC asynchronous motor;

[0021] The VCC terminal of the first driver chip is electrically connected to the positive electrode of the first diode, the VB terminal of the first driver chip is electrically connected to the negative electrode of the first diode, the first phase output terminal of the controller is electrically connected to the HIN terminal of the first driver chip, and the output terminal of the first electronic switch is electrically connected to the LIN terminal of the first driver chip.

[0022] Preferably, the second driving circuit comprises: a second driving chip, a second diode, a ninth resistor, a tenth resistor, and a second capacitor;

[0023] The HO terminal of the second driver chip is electrically connected to the G pole of the second MOS tube through the ninth resistor, the LO terminal of the second driver chip is electrically connected to the G pole of the fourth MOS tube through the tenth resistor, the VB terminal of the second driver chip is electrically connected to the S pole of the second MOS tube through the first capacitor, the VS terminal of the second driver chip is electrically connected to the S pole of the second MOS tube and the D pole of the fourth MOS tube, and the VS terminal of the second driver chip is electrically connected to the input terminal of the AC asynchronous motor;

[0024] The VCC terminal of the second driver chip is electrically connected to the anode of the second diode, the VB terminal of the second driver chip is electrically connected to the cathode of the second diode, the second phase output terminal of the controller is electrically connected to the HIN terminal of the second driver chip, and the output terminal of the second electronic switch is electrically connected to the LIN terminal of the second driver chip.

[0025] Preferably, the first electronic switch includes a second triode, a third triode, a third diode, an eleventh resistor, and a twelfth resistor;

[0026] The B pole of the second triode is electrically connected to the C pole of the third triode through the eleventh resistor, the E pole of the third triode is grounded, the B pole of the third triode is electrically connected to the first phase output terminal of the controller through the twelfth resistor, the C pole of the second triode is electrically connected to the positive pole of the third diode, and the E pole of the second triode is electrically connected to the negative pole of the diode;

[0027] The C pole of the second transistor is electrically connected to the LIN terminal of the first driving chip, and the E pole of the second transistor is electrically connected to the driving signal output terminal of the controller.

[0028] Preferably, the second electronic switch includes a fourth triode, a fifth triode, a fourth diode, a thirteenth resistor, and a fourteenth resistor;

[0029] The B pole of the fourth triode is electrically connected to the C pole of the fifth triode through the thirteenth resistor, the E pole of the fifth triode is grounded, the B pole of the fifth triode is electrically connected to the second phase signal output end of the controller through the fourteenth resistor, the C pole of the fourth triode is electrically connected to the positive pole of the fourth diode, and the E pole of the fourth triode is electrically connected to the negative pole of the tetrode;

[0030] The C pole of the fourth transistor is electrically connected to the LIN terminal of the second driving chip, and the E pole of the fourth transistor is electrically connected to the driving signal output terminal of the controller.

[0031] A second embodiment of the present invention provides a stepless speed regulation method for an AC asynchronous motor, comprising:

[0032] Acquiring a detection signal collected by the zero-crossing detection circuit;

[0033] After judging that the first rising edge of the zero-crossing signal has arrived according to the detection signal, the drive signal, the first phase signal, and the second phase signal are cleared; after judging that the first falling edge of the zero-crossing signal has arrived according to the detection signal, the drive signal is started, and the first phase signal is set high, and a positive half-cycle voltage matching the required speed of the AC asynchronous motor is output through the H-bridge drive circuit;

[0034] After judging that the second rising edge of the zero-crossing signal has arrived according to the detection signal, the drive signal, the first phase signal, and the second phase signal are cleared; after judging that the second falling edge of the zero-crossing signal has arrived according to the detection signal, the drive signal is started and the second phase signal is set high, and a negative half-cycle voltage matching the required speed of the AC asynchronous motor is output through the H-bridge drive circuit; wherein the positive half-cycle voltage and the negative half-cycle voltage are used to drive the AC asynchronous motor.

[0035] Preferably, the rotation speed of the AC asynchronous motor can be changed according to the duty cycle of the drive signal.

[0036] A third embodiment of the present invention provides an AC asynchronous motor, comprising a motor body and a stepless speed regulation circuit for an AC asynchronous motor as described in any one of the above items, wherein the output end of the H-bridge drive circuit is electrically connected to the input end of the motor body.

[0037] Based on an AC asynchronous motor and its stepless speed regulation circuit and method provided by the present invention, an input AC sinusoidal voltage with positive and negative half cycles is rectified into a unipolar DC voltage through a rectifier circuit, and no filtering is performed after rectification, so that the rectified voltage is a DC steamed wave with a frequency twice that of the power supply. Then, through an H-bridge drive circuit, pulse width modulation is performed on the steamed wave DC voltage of half a cycle, and it stops when a zero-crossing signal arrives. After the zero-crossing signal passes, the H-bridge arm is switched to perform pulse width modulation on the other half cycle. In this way, the phase is repeatedly switched with the zero-crossing signal as the dividing point, and finally an AC voltage with a sinusoidal profile that has been pulse-width modulated is synthesized on the load, thereby solving the problems of high cost, voltage distortion and reduced power factor in the existing technology for motor speed regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a module schematic diagram of an AC asynchronous motor and a stepless speed regulation circuit thereof provided by an embodiment of the present invention;

[0039] Figure 2 It is a schematic diagram of an AC asynchronous motor and a stepless speed regulation circuit thereof provided by an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of waveform adjustment changes provided by an embodiment of the present invention;

[0041] Figure 4 The present invention provides an AC asynchronous motor and a stepless speed regulation method thereof. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0044] It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0046] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0047] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0048] The "first\second" mentioned in the embodiments is only to distinguish similar objects, and does not represent a specific order for the objects. It is understandable that the "first\second" can be interchanged with the specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second" can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0049] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0050] The invention discloses an AC asynchronous motor and a stepless speed regulation circuit and method thereof, aiming to solve the problems of high cost, voltage distortion and power factor reduction in the speed regulation of the motor in the prior art.

[0051] See also Figure 1 and 2 The first embodiment of the present invention provides a stepless speed regulation circuit for an AC asynchronous motor, comprising: a controller 1, a rectifier circuit 2, a zero-crossing detection circuit 3, an H-bridge drive circuit 5, a first drive circuit 4, a second drive circuit 6, a first electronic switch 8, and a second electronic switch 7;

[0052] The input end of the rectifier circuit 2 is used to connect to an AC power supply, the output end of the rectifier circuit 2 is electrically connected to the input end of the zero-crossing detection circuit 3, and the output end of the zero-crossing detection circuit 3 is electrically connected to the input end of the controller 1;

[0053] The output end of the rectifier circuit 2 is electrically connected to the input end of the H-bridge drive circuit 5, and the output end of the H-bridge drive circuit 5 is used to connect to the AC asynchronous motor;

[0054] The first phase signal output terminal of the controller 1 is electrically connected to the first control terminal of the H-bridge drive circuit 5 through the first drive circuit 4, and the second phase signal output terminal of the controller 1 is electrically connected to the second control terminal of the H-bridge drive circuit 5 through the second drive circuit 6;

[0055] The drive signal output end of the controller 1 is electrically connected to the input end of the first drive circuit 4 through the first electronic switch 8 , and the drive signal output end of the controller 1 is electrically connected to the input end of the second drive circuit 6 through the second electronic switch 7 .

[0056] It should be noted that, in the present embodiment, the input AC sinusoidal voltage with positive and negative half cycles is rectified into a unipolar DC voltage through the rectifier circuit 2, and no filtering is performed after rectification, so that the rectified voltage is a DC steamed wave with a frequency twice that of the power supply, and then divided into two paths, one path passes through the zero-crossing detection circuit 3, and the other path passes through the H-bridge drive circuit 5, wherein the controller 1 detects the zero-crossing signal and the corresponding rising edge and falling edge through the zero-crossing detection circuit 3, and when the first zero-crossing signal arrives, the first drive circuit 4, the second drive circuit 6, the first electronic switch 8, and the second electronic switch 7 are used. Switching is performed so that the steamed bun wave DC voltage of the first half cycle of the H-bridge driving circuit 5 is pulse-width modulated. When the next zero-crossing signal arrives, switching is performed through the first driving circuit 4, the second driving circuit 6, the first electronic switch 8, and the second electronic switch 7, so that the steamed bun wave DC voltage of the second half cycle of the H-bridge driving circuit 5 is pulse-width modulated. In this way, the phase is repeatedly switched with the zero-crossing signal as the dividing point, and finally an AC voltage with a sinusoidal profile after pulse width modulation is synthesized on the load, thereby solving the problems of high cost, voltage distortion, and reduced power factor in the prior art for speed regulation of the motor.

[0057] See also Figure 2 In a possible embodiment of the present invention, the H-bridge driving circuit 5 includes: a first MOS tube Q1, a second MOS tube Q2, a third MOS tube Q3, a fourth MOS tube Q4, and a first resistor R1;

[0058] The first end of the first resistor R1 is electrically connected to the output end of the rectifier loop 2, the D pole of the first MOS tube Q1 and the D pole of the second MOS tube Q2 are electrically connected to the second end of the first resistor R1, the S pole of the first MOS tube Q1 is electrically connected to the D pole of the third MOS tube Q3, the S pole of the second MOS tube Q2 is electrically connected to the D pole of the fourth MOS tube Q4, and the S pole of the third MOS tube Q3 is electrically connected to the S pole of the fourth MOS tube Q4;

[0059] The output end of the first driving circuit 4 is electrically connected to the G pole of the first MOS transistor Q1 and the G pole of the third MOS transistor Q3 , and the output end of the second driving circuit 6 is electrically connected to the G pole of the second MOS transistor Q2 and the G pole of the fourth MOS transistor Q4 .

[0060] It should be noted that the first MOS tube Q1, the second MOS tube Q2, the third MOS tube Q3, and the fourth MOS tube Q4 form an H-bridge, the rectified power supply is input to the H-bridge through the first resistor R1, and the H-bridge outputs a voltage capable of adjusting the speed of the AC asynchronous motor. In other embodiments, other circuit structures may be used to form the H-bridge drive circuit 5, which is not specifically limited here, but these solutions are within the protection scope of the present invention.

[0061] In a possible embodiment of the present invention, the zero-crossing detection circuit 3 includes: a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a first transistor N1;

[0062] The output end of the rectifier circuit 2 is electrically connected to the first end of the second resistor R2, the second end of the second resistor R2 is electrically connected to the first end of the third resistor R3, the second end of the third resistor R3 is electrically connected to the B pole of the first transistor N1 through the fourth resistor R4, the B pole of the first transistor N1 is grounded through the fifth resistor R5, the E pole of the first transistor N1 is grounded, the C pole of the first transistor N1 is connected to the power supply through the sixth resistor R6, and the C pole of the first transistor N1 is electrically connected to the input end of the controller 1.

[0063] It should be noted that after the AC power is rectified by the rectifier circuit 2, the detection signal is output to the controller 1 through the zero-crossing detection circuit 3, and the controller 1 can judge the zero-crossing point, the rising edge after the zero-crossing point, the falling edge after the rising edge, the zero-crossing point, the rising edge after the zero-crossing point, and the falling edge after the rising edge through the detection signal, and so on. In other embodiments, other circuit structures can also be used to form the zero-crossing detection circuit 3, which is not specifically limited here, but these schemes are all within the protection scope of the present invention.

[0064] In a possible embodiment of the present invention, the first driving circuit 4 includes: a first driving chip U1, a first diode D1, a seventh resistor R7, an eighth resistor R8, and a first capacitor C1;

[0065] The HO terminal of the first driver chip U1 is electrically connected to the G pole of the first MOS tube Q1 through the seventh resistor R7, the LO terminal of the first driver chip U1 is electrically connected to the G pole of the third MOS tube Q3 through the eighth resistor R8, the VB terminal of the first driver chip U1 is electrically connected to the S pole of the first MOS tube Q1 through the first capacitor C1, the VS terminal of the first driver chip U1 is electrically connected to the S pole of the first MOS tube Q1 and the D pole of the third MOS tube Q3, and the VS terminal of the first driver chip U1 is electrically connected to the input terminal of the AC asynchronous motor;

[0066] The VCC terminal of the first driver chip U1 is electrically connected to the positive electrode of the first diode D1, the VB terminal of the first driver chip U1 is electrically connected to the negative electrode of the first diode D1, the first phase output terminal of the controller 1 is electrically connected to the HIN terminal of the first driver chip U1, and the output terminal of the first electronic switch 8 is electrically connected to the LIN terminal of the first driver chip U1.

[0067] In a possible embodiment of the present invention, the second driving circuit 6 includes: a second driving chip U2, a second diode D2, a ninth resistor R9, a tenth resistor R10, and a second capacitor C2;

[0068] The HO terminal of the second driver chip U2 is electrically connected to the G pole of the second MOS tube Q2 through the ninth resistor R9, the LO terminal of the second driver chip U2 is electrically connected to the G pole of the fourth MOS tube Q4 through the tenth resistor R10, the VB terminal of the second driver chip U2 is electrically connected to the S pole of the second MOS tube Q2 through the first capacitor C1, the VS terminal of the second driver chip U2 is electrically connected to the S pole of the second MOS tube Q2 and the D pole of the fourth MOS tube Q4, and the VS terminal of the second driver chip U2 is electrically connected to the input terminal of the AC asynchronous motor;

[0069] The VCC terminal of the second driver chip U2 is electrically connected to the positive electrode of the second diode D2, the VB terminal of the second driver chip U2 is electrically connected to the negative electrode of the second diode D2, the second phase output terminal of the controller 1 is electrically connected to the HIN terminal of the second driver chip U2, and the output terminal of the second electronic switch 7 is electrically connected to the LIN terminal of the second driver chip U2.

[0070] In a possible embodiment of the present invention, the first electronic switch 8 includes a second transistor N2, a third transistor N3, a third diode D3, an eleventh resistor R11, and a twelfth resistor R12;

[0071] The B pole of the second triode N2 is electrically connected to the C pole of the third triode N3 through the eleventh resistor R11, the E pole of the third triode N3 is grounded, the B pole of the third triode N3 is electrically connected to the first phase output terminal of the controller 1 through the twelfth resistor R12, the C pole of the second triode N2 is electrically connected to the positive pole of the third diode D3, and the E pole of the second triode N2 is electrically connected to the negative pole of the diode;

[0072] The C pole of the second transistor N2 is electrically connected to the LIN terminal of the first driving chip U1 , and the E pole of the second transistor N2 is electrically connected to the driving signal output terminal of the controller 1 .

[0073] In a possible embodiment of the present invention, the second electronic switch 7 includes a fourth transistor N4, a fifth transistor N5, a fourth diode D4, a thirteenth resistor R13, and a fourteenth resistor R14;

[0074] The B pole of the fourth triode N4 is electrically connected to the C pole of the fifth triode N5 through the thirteenth resistor R13, the E pole of the fifth triode N5 is grounded, the B pole of the fifth triode N5 is electrically connected to the second phase signal output end of the controller 1 through the fourteenth resistor R14, the C pole of the fourth triode N4 is electrically connected to the positive pole of the fourth diode D4, and the E pole of the fourth triode N4 is electrically connected to the negative pole of the tetrode;

[0075] The C pole of the fourth transistor N4 is electrically connected to the LIN terminal of the second driving chip U2 , and the E pole of the fourth transistor N4 is electrically connected to the driving signal output terminal of the controller 1 .

[0076] The working principle of the embodiment of the present invention is briefly described below:

[0077] The detection signal is sent to the input end of the controller 1 through the zero-crossing detection circuit 3. When the controller 1 does not detect the zero-crossing according to the detection signal, the controller 1 controls the drive signal, the first phase signal, and the second phase signal to be all cleared;

[0078] After the controller 1 detects the rising edge of the zero-crossing signal according to the detection signal, the controller 1 controls the drive signal, the first phase signal, and the second phase signal to be all cleared;

[0079] After the controller 1 detects the arrival of the falling edge of the zero-crossing signal according to the detection signal, the controller 1 sends a driving signal and sets the first phase signal high, wherein the high-level signal is sent to the HIN pin of the first driver chip U1, and at the same time, the high-level signal controls the opening of the first electronic switch 8 composed of the second transistor N2, the third transistor N3, the third diode D3, the eleventh resistor R11, and the twelfth resistor R12, and sends the driving signal to the LIN pin of the second driver chip U2 through the fourth transistor N4. In this way, the first MOS tube Q1 is turned on under the drive of the first driver chip U1, and the fourth MOS tube Q4 is in the switch-on state under the drive of the second driver chip U2, so as to synthesize a waveform of the positive half cycle, and the waveform is as shown in FIG. Figure 3 shown.

[0080] After the controller 1 detects the rising edge of the zero-crossing signal again according to the detection signal, the controller 1 controls the drive signal, the first phase signal, and the second phase signal to remain all cleared;

[0081] After the controller 1 detects the falling edge of the zero-crossing signal again according to the detection signal, the controller 1 sends a driving signal and sets the second phase signal high, wherein the high-level signal is sent to the HIN pin of the second driver chip U2, and at the same time, the high-level signal controls the opening of the second electronic switch 7 composed of the fourth transistor N4, the fifth transistor N5, the fourth diode D4, the thirteenth resistor R13, and the fourteenth resistor R14, and sends the driving signal to the LIN pin of the first driver chip U1 through the second transistor N2. In this way, the second MOS tube Q2 is turned on under the drive of the second driver chip U2, and the third MOS tube Q3 is in the switch-on state under the drive of the first driver chip U1, so as to synthesize the waveform of the negative half cycle.

[0082] It should be noted that the waveforms of the positive and negative half cycles synthesize an AC voltage with a sinusoidal voltage profile to supply the motor, which can easily adjust the speed of the motor by adjusting the duty cycle of the drive signal (e.g., PWM signal), and the adjustment level of the speed depends on the resolution of PWM. In this embodiment, the controller 1 can be a single-chip microcomputer of the STM32 series, of course, it is not limited to this, and PLC can also be used for processing.

[0083] The present invention has at least the following beneficial effects:

[0084] 1. The power factor is high, and the waveform is still a sine wave, so the power factor can still be maintained above 0.9, and the power utilization rate is high;

[0085] 2. Good waveform coefficient and low noise: Since there is no obvious waveform distortion, the waveform coefficient is high, the harmonic component is small, there is no electromagnetic sound when the motor is working, and the user experience is very good when used in home appliances.

[0086] 3. Low cost. Since the motor adopts a single-speed motor, the cost of the motor can be significantly reduced.

[0087] See also Figure 4 The second embodiment of the present invention provides a stepless speed regulation method for an AC asynchronous motor, comprising:

[0088] S101, acquiring a detection signal collected by the zero-crossing detection circuit 3;

[0089] S102, after judging that the first rising edge of the zero-crossing signal has arrived according to the detection signal, clearing the drive signal, the first phase signal, and the second phase signal, after judging that the first falling edge of the zero-crossing signal has arrived according to the detection signal, starting the drive signal and setting the first phase signal high, outputting a positive half-cycle voltage adapted to the required speed of the AC asynchronous motor through the H-bridge drive circuit 5;

[0090] S103, after judging according to the detection signal that the second rising edge of the zero-crossing signal has arrived, clear the drive signal, the first phase signal, and the second phase signal; after judging according to the detection signal that the second falling edge of the zero-crossing signal has arrived, start the drive signal and set the second phase signal high, and output a negative half-cycle voltage that matches the required speed of the AC asynchronous motor through the H-bridge drive circuit 5; wherein the positive half-cycle voltage and the negative half-cycle voltage are used to drive the AC asynchronous motor.

[0091] Preferably, the rotation speed of the AC asynchronous motor can be changed according to the duty cycle of the drive signal.

[0092] A third embodiment of the present invention provides an AC asynchronous motor, comprising a motor body and a stepless speed regulation circuit for an AC asynchronous motor as described in any one of the above items, wherein the output end of the H-bridge drive circuit 5 is electrically connected to the input end of the motor body.

[0093] Based on an AC asynchronous motor and its stepless speed regulation circuit and method provided by the present invention, an input AC sinusoidal voltage with positive and negative half cycles is rectified into a unipolar DC voltage through a rectifier circuit 2, and no filtering is performed after rectification, so that the rectified voltage is a DC steamed wave with a frequency twice that of the power supply. Then, through an H-bridge drive circuit 5, pulse width modulation is performed on the steamed wave DC voltage of half a cycle, and it stops when a zero-crossing signal arrives. After the zero-crossing signal passes, the H-bridge arm is switched to perform pulse width modulation on the other half cycle. In this way, the phase is repeatedly switched with the zero-crossing signal as the dividing point, and finally an AC voltage with a sinusoidal profile that has been pulse-width modulated is synthesized on the load, thereby solving the problems of high cost, voltage distortion and reduced power factor in the existing technology for speed regulation of motors.

[0094] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A stepless speed regulation circuit for an AC asynchronous motor, characterized in that: include: A controller, a rectification circuit, a zero-crossing detection circuit, an H-bridge drive circuit, a first drive circuit, a second drive circuit, a first electronic switch, and a second electronic switch; The input end of the rectifier circuit is used to connect to an AC power supply, the output end of the rectifier circuit is electrically connected to the input end of the zero-crossing detection circuit, and the output end of the zero-crossing detection circuit is electrically connected to the input end of the controller, wherein the voltage waveform output by the rectifier circuit is a DC steamed wave with a frequency twice that of the power supply; The output end of the rectifier circuit is electrically connected to the input end of the H-bridge drive circuit, the output end of the H-bridge drive circuit is used to connect the AC asynchronous motor, and the voltage output by the H-bridge drive circuit is an AC voltage that has been pulse-width modulated and has a sinusoidal profile; The first phase signal output terminal of the controller is electrically connected to the first control terminal of the H-bridge drive circuit through the first drive circuit, and the second phase signal output terminal of the controller is electrically connected to the second control terminal of the H-bridge drive circuit through the second drive circuit; The drive signal output terminal of the controller is electrically connected to the input terminal of the first drive circuit through the first electronic switch, and the drive signal output terminal of the controller is electrically connected to the input terminal of the second drive circuit through the second electronic switch; The H-bridge driving circuit comprises: a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, and a first resistor; The first end of the first resistor is electrically connected to the output end of the rectifier circuit, the D pole of the first MOS tube and the D pole of the second MOS tube are electrically connected to the second end of the first resistor, the S pole of the first MOS tube is electrically connected to the D pole of the third MOS tube, the S pole of the second MOS tube is electrically connected to the D pole of the fourth MOS tube, and the S pole of the third MOS tube is electrically connected to the S pole of the fourth MOS tube; The output end of the first driving circuit is electrically connected to the G pole of the first MOS tube and the G pole of the third MOS tube, and the output end of the second driving circuit is electrically connected to the G pole of the second MOS tube and the G pole of the fourth MOS tube; The zero-crossing detection circuit includes: a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a first transistor; The output end of the rectifier circuit is electrically connected to the first end of the second resistor, the second end of the second resistor is electrically connected to the first end of the third resistor, the second end of the third resistor is electrically connected to the B pole of the first transistor through the fourth resistor, the B pole of the first transistor is grounded through the fifth resistor, the E pole of the first transistor is grounded, the C pole of the first transistor is connected to the power supply through the sixth resistor, and the C pole of the first transistor is electrically connected to the input end of the controller.

2. The stepless speed regulation circuit of an AC asynchronous motor according to claim 1, characterized in that: The first driving circuit includes: a first driving chip, a first diode, a seventh resistor, an eighth resistor, and a first capacitor; The HO terminal of the first driver chip is electrically connected to the G pole of the first MOS tube through the seventh resistor, the LO terminal of the first driver chip is electrically connected to the G pole of the third MOS tube through the eighth resistor, the VB terminal of the first driver chip is electrically connected to the S pole of the first MOS tube through the first capacitor, the VS terminal of the first driver chip is electrically connected to the S pole of the first MOS tube and the D pole of the third MOS tube, and the VS terminal of the first driver chip is electrically connected to the input terminal of the AC asynchronous motor; The VCC terminal of the first driver chip is electrically connected to the positive electrode of the first diode, the VB terminal of the first driver chip is electrically connected to the negative electrode of the first diode, the first phase output terminal of the controller is electrically connected to the HIN terminal of the first driver chip, and the output terminal of the first electronic switch is electrically connected to the LIN terminal of the first driver chip.

3. The stepless speed regulation circuit of an AC asynchronous motor according to claim 2, characterized in that: The second driving circuit includes: a second driving chip, a second diode, a ninth resistor, a tenth resistor, and a second capacitor; The HO terminal of the second driver chip is electrically connected to the G pole of the second MOS tube through the ninth resistor, the LO terminal of the second driver chip is electrically connected to the G pole of the fourth MOS tube through the tenth resistor, the VB terminal of the second driver chip is electrically connected to the S pole of the second MOS tube through the first capacitor, the VS terminal of the second driver chip is electrically connected to the S pole of the second MOS tube and the D pole of the fourth MOS tube, and the VS terminal of the second driver chip is electrically connected to the input terminal of the AC asynchronous motor; The VCC terminal of the second driver chip is electrically connected to the anode of the second diode, the VB terminal of the second driver chip is electrically connected to the cathode of the second diode, the second phase output terminal of the controller is electrically connected to the HIN terminal of the second driver chip, and the output terminal of the second electronic switch is electrically connected to the LIN terminal of the second driver chip.

4. The stepless speed regulation circuit of an AC asynchronous motor according to claim 3, characterized in that: The first electronic switch includes a second triode, a third triode, a third diode, an eleventh resistor, and a twelfth resistor; The B pole of the second triode is electrically connected to the C pole of the third triode through the eleventh resistor, the E pole of the third triode is grounded, the B pole of the third triode is electrically connected to the first phase output terminal of the controller through the twelfth resistor, the C pole of the second triode is electrically connected to the positive pole of the third diode, and the E pole of the second triode is electrically connected to the negative pole of the diode; The C pole of the second transistor is electrically connected to the LIN terminal of the first driving chip, and the E pole of the second transistor is electrically connected to the driving signal output terminal of the controller.

5. The stepless speed regulation circuit of an AC asynchronous motor according to claim 4, characterized in that: The second electronic switch includes a fourth triode, a fifth triode, a fourth diode, a thirteenth resistor, and a fourteenth resistor; The B pole of the fourth triode is electrically connected to the C pole of the fifth triode through the thirteenth resistor, the E pole of the fifth triode is grounded, the B pole of the fifth triode is electrically connected to the second phase signal output terminal of the controller through the fourteenth resistor, the C pole of the fourth triode is electrically connected to the positive pole of the fourth diode, and the E pole of the fourth triode is electrically connected to the negative pole of the fourth diode; The C pole of the fourth transistor is electrically connected to the LIN terminal of the second driving chip, and the E pole of the fourth transistor is electrically connected to the driving signal output terminal of the controller.

6. A method for steplessly regulating the speed of an AC asynchronous motor based on a steplessly regulating speed circuit of an AC asynchronous motor according to any one of claims 1 to 5, characterized in that: include Acquiring a detection signal collected by the zero-crossing detection circuit; After judging that the first rising edge of the zero-crossing signal has arrived according to the detection signal, the drive signal, the first phase signal, and the second phase signal are cleared; after judging that the first falling edge of the zero-crossing signal has arrived according to the detection signal, the drive signal is started, and the first phase signal is set high, and a positive half-cycle voltage matching the required speed of the AC asynchronous motor is output through the H-bridge drive circuit; After judging that the second rising edge of the zero-crossing signal has arrived according to the detection signal, the drive signal, the first phase signal, and the second phase signal are cleared; after judging that the second falling edge of the zero-crossing signal has arrived according to the detection signal, the drive signal is started and the second phase signal is set high, and a negative half-cycle voltage matching the required speed of the AC asynchronous motor is output through the H-bridge drive circuit; wherein the positive half-cycle voltage and the negative half-cycle voltage are used to drive the AC asynchronous motor.

7. The stepless speed regulation method of an AC asynchronous motor according to claim 6, characterized in that: The rotation speed of the AC asynchronous motor can be changed according to the duty cycle of the driving signal.

8. An AC asynchronous motor, characterized in that: It comprises a motor body and a stepless speed regulation circuit of an AC asynchronous motor as claimed in any one of claims 1 to 5, wherein the output end of the H-bridge drive circuit is electrically connected to the input end of the motor body.

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