Alternating current motor speed regulation device

Abstract

The utility model relates to the technical field of motor speed regulation equipment, in particular to an alternating current motor speed regulation device which comprises a control chip, a zero-cross detection circuit module and a speed regulation circuit module. One end of the zero-crossing detection circuit module is used for receiving an alternating current signal sent by an alternating current power supply, the other end of the zero-crossing detection circuit module is connected to the control chip, and the zero-crossing detection circuit module is used for obtaining a zero-crossing signal of the alternating current signal and transmitting the zero-crossing signal to the control chip. The speed regulation circuit module is connected to the control chip and used for being connected to an alternating current motor, the control chip outputs a control signal to the speed regulation circuit module according to the zero-crossing signal, and the speed regulation circuit module is provided with a bidirectional silicon controlled rectifier switch. The bidirectional silicon-controlled switch is used for controlling the disconnection of the current of the AC motor when a zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered. The AC motor speed regulation device can avoid the problem that the silicon controlled rectifier cannot be effectively controlled due to the zero-crossing signal detection delay defect caused by components, and can realize accurate speed regulation.

Description

Technical Field

[0001] The present application relates to the technical field of motor speed regulation equipment, and in particular to an AC motor speed regulation device. Background Art

[0002] At present, AC motor speed regulation generally requires the application of zero-crossing detection technology. In the AC system, when the current waveform changes from the positive half-cycle to the negative half-cycle and passes through the zero point, the system detects, that is, controls the conduction time of the thyristor switch when the current passes through zero, thereby achieving the purpose of speed regulation. The above method requires a very accurate zero-crossing signal. Due to the errors of the components themselves and the conduction characteristics of the thyristor switch, the zero-crossing detection signal will lag and cannot effectively control the thyristor switch to achieve speed regulation. At the same time, the pursuit of accurate zero-crossing signals means an increase in cost and an increase in the difficulty of hardware development. Utility Model Content

[0003] The present application provides an AC motor speed control device, which includes: a control chip, a zero-crossing detection circuit module and a speed control circuit module. One end of the zero-crossing detection circuit module is used to receive an AC signal emitted by an AC power source, and the other end is connected to the control chip. The zero-crossing detection circuit module is used to obtain the zero-crossing moment of the AC signal to generate a zero-crossing signal, and transmit the zero-crossing signal to the control chip. The speed control circuit module is connected to the control chip and is used to connect to the AC motor. The control chip outputs a control signal to the speed control circuit module according to the zero-crossing signal. The speed control circuit module is provided with a bidirectional thyristor switch; the bidirectional thyristor switch is used to control the disconnection of the current of the AC motor when the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered.

[0004] Optionally, in some embodiments, the zero-crossing detection circuit module includes an NPN transistor, the base of the NPN transistor is connected to the AC power supply, the emitter of the NPN transistor is grounded, the control chip is provided with a first pin, the collector of the NPN transistor is connected to the first pin of the control chip and is used to output a zero-crossing signal to the first pin.

[0005] Optionally, in some embodiments, the NPN transistor is provided with a preset voltage value, which is equal to the cut-off voltage of the NPN transistor. When the AC voltage of the AC power supply is less than or equal to the preset voltage value, the collector of the NPN transistor outputs a zero-crossing signal to the control chip; the control chip is used to generate a control waveform according to the zero-crossing signal, wherein the control waveform is at a low level when the voltage of the AC power supply is greater than the preset voltage value, and the control waveform is at a high level when the voltage of the AC power supply is less than or equal to the preset voltage value. When the zero-crossing signal corresponding to the AC signal changing from the positive half cycle to the negative half cycle is triggered, the control waveform presents a rising edge, and the control chip is also used to control the bidirectional thyristor switch to operate according to the control waveform.

[0006] Optionally, in some embodiments, the control chip is provided with a timer, and the timer is used to alternately time a first preset time length and a second preset time length; the control chip is used to control the bidirectional thyristor to turn off and on according to a predetermined period, and the bidirectional thyristor switch remains off for a first preset time length during the predetermined period, and remains on for a second preset time length; the first preset time length and the second preset time length are both integer multiples of the period of the AC current emitted by the AC power supply.

[0007] Optionally, in some embodiments, the timer is used to start timing at a rising edge of the control waveform and end timing at the next rising edge of the control waveform to obtain the cycle of the AC current; the control chip is used to send a first control signal to the bidirectional thyristor switch at a rising edge of the control waveform to turn off the bidirectional thyristor switch, and the timer starts timing for a first preset time. When the timer reaches the first preset time, the control chip sends a second control signal to the bidirectional thyristor switch to turn on the bidirectional thyristor switch, and the timer starts timing for a second preset time. When the timer reaches the second preset time, the control chip sends a first control signal to the bidirectional thyristor switch to turn on the bidirectional thyristor switch.

[0008] Optionally, in some embodiments, the AC motor speed control device also includes a conversion circuit module, the control chip is provided with a second pin, the conversion circuit module is connected between the AC power supply and the second pin of the control chip, and is used to convert the AC power output by the AC power supply into DC power and provide it to the control chip.

[0009] Optionally, in some embodiments, the conversion circuit module is also connected between the AC power source and the collector of the NPN transistor, and is used to convert the AC power output by the AC power source into DC power and provide it to the zero-crossing detection circuit module.

[0010] Optionally, in some embodiments, the zero-crossing detection circuit module further includes a first current limiting resistor and a second current limiting resistor, the first current limiting resistor being connected in series between the collector and the second pin of the NPN transistor, and the second current limiting resistor being connected in series between the collector and the first pin of the NPN transistor.

[0011] Optionally, in some embodiments, the zero-crossing circuit detection module also includes a first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor, the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between the base of the NPN transistor and the AC power supply, and the two ends of the third voltage-dividing resistor are respectively connected to the base and emitter of the NPN transistor.

[0012] Optionally, in some embodiments, the zero-crossing detection circuit module further includes a filter capacitor, and the filter capacitor is connected in parallel to both ends of the third voltage divider resistor.

[0013] Optionally, in some embodiments, the first main pole of the bidirectional thyristor switch is used to connect to the AC motor, the second main pole of the bidirectional thyristor switch is connected to the AC power supply, the control chip is provided with a third pin, and the gate of the bidirectional thyristor switch is connected to the third pin.

[0014] Optionally, in some embodiments, the speed regulating circuit module further includes a third current limiting resistor, and the third current limiting resistor is connected in series between the gate and the third pin of the bidirectional thyristor switch.

[0015] Optionally, in some embodiments, there are multiple bidirectional thyristor switches, the number of third pins of the control chip is the same as the number of bidirectional thyristors, and the gates of the multiple bidirectional thyristors are connected to the multiple third pins of the control chip in a one-to-one correspondence.

[0016] In the AC motor speed control device provided in the present application, a zero-crossing detection circuit module is set to obtain the zero-crossing moment of the AC power supply to generate a zero-crossing signal and transmit it to the control chip. The control chip outputs a control signal to the speed control circuit module according to the zero-crossing signal. The control signal is used to control the conduction and shutdown of the bidirectional thyristor switch, thereby controlling the on and off of the current of the AC motor. Specifically, when the zero-crossing signal corresponding to the change from the positive half-cycle to the negative half-cycle of the AC signal is triggered, the control chip can send a shutdown signal to the bidirectional thyristor switch. Since the triggering moment of the zero-crossing signal corresponding to the change from the positive half-cycle to the negative half-cycle of the AC signal is ahead of the actual zero-crossing moment of the AC power, the delay characteristics of the bidirectional thyristor can make the bidirectional thyristor switch turn off at the actual zero-crossing moment of the AC power signal. Therefore, it can be ensured that the bidirectional thyristor switch is turned off more accurately when the actual zero-crossing signal is generated, and the turn-off moment of the bidirectional thyristor switch is as close as possible to the actual zero-crossing moment of the AC power. Therefore, the transfer control of the AC motor is more accurate. In the embodiment of the present application, by controlling the turn-off time and the turn-on time of the bidirectional thyristor switch, the AC motor can be accurately controlled without increasing the hardware cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is a circuit structure block diagram of the AC motor speed control device in some embodiments of the present application.

[0019] Figure 2 It is a circuit schematic diagram of the AC motor speed control device in some embodiments of the present application.

[0020] Figure 3 It is a schematic diagram of the relationship between the control waveform L2 generated by the control module according to the zero-crossing signal output by the zero-crossing detection circuit module and the waveform L1 of the AC power signal of the AC power supply in some embodiments of the present application.

[0021] Figure 4 It is a speed regulation flow chart of the AC motor speed regulation device in some embodiments of the present application.

[0022] Explanation of reference numerals: 100, AC motor speed control device; 70, control chip; 101, first pin; 102, second pin; 103, third pin; 80, zero-crossing detection circuit module; Q1, NPN transistor; R1, first current limiting resistor; R2, second current limiting resistor; R3, first voltage dividing resistor; R4, second voltage dividing resistor; R5, third voltage dividing resistor; C, filter capacitor; 30, speed control circuit module; S1, bidirectional thyristor switch; R6, third current limiting resistor; 40, conversion circuit module; 50, AC motor; 60, AC power supply. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0024] In the description of the present application, it should be understood that the terms "length", "width", "thickness", "up", "down", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or state relationships based on the positions or state relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0025] In addition, some of the above terms may be used to express other meanings in addition to indicating a position or state relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0026] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] In addition, unless otherwise expressly specified or limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can be internal communication between two elements, or it can be only surface contact. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0028] If certain words are used in the specification and claims to refer to specific components, those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use differences in names as a way to distinguish components, but use differences in components' functions as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to"; "substantially" means that those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0029] See also Figure 1 , an embodiment of the present application provides an AC motor speed regulating device 100, which is used to regulate the speed of an AC motor 50. For example, the AC motor speed regulating device 100 can be used in an electric fan, which adjusts the speed of the AC motor 50 in the electric fan to change the gear of the electric fan, thereby meeting the diverse usage needs of users. The electric fan here is only an example, and does not limit the application environment of the AC motor speed regulating device 100. The AC motor 50 motor speed regulating device can also be used in any device or equipment equipped with an AC motor 50, for example, a walking device using an AC motor drive wheel, etc.

[0030] The AC motor speed control device 100 includes: a control chip 70, a zero-crossing detection circuit module 80 and a speed control circuit module 30. One end of the zero-crossing detection circuit module 80 is used to receive an AC signal from an AC power source 60, and the other end is connected to the control chip 70. The zero-crossing detection circuit module 80 is used to obtain a zero-crossing signal of the AC signal and transmit the zero-crossing signal to the control chip 70. The speed control circuit module 30 is connected to the control chip 70 and is used to be connected to the AC motor 50. The control chip 70 outputs a control signal to the speed control circuit module 30 according to the zero-crossing signal. The speed control circuit module 30 is provided with a bidirectional thyristor switch S1. The bidirectional thyristor switch S1 controls the on and off of the current of the AC motor 50 according to the control signal when the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered. As a specific example, the control chip 70 can be a microcontroller unit (MCU).

[0031] Through the above configuration, the zero-crossing detection circuit module 80 is used to obtain the zero-crossing signal of the AC power supply 60 and transmit it to the control chip 70. The control chip 70 outputs a control signal to the speed control circuit module 30 according to the zero-crossing signal. The control signal is used to control the on and off of the bidirectional thyristor switch S1, thereby controlling the on and off of the current of the AC motor 50. Specifically, when the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered, the control chip 70 can send a shutdown signal to the bidirectional thyristor switch S1. Since the zero-crossing signal triggering moment ( Figure 2 Point A) relative to the actual zero-crossing moment of the alternating current ( Figure 2 The delay characteristic of the bidirectional thyristor is used to make the bidirectional thyristor switch S1 turn off only when the AC power actually crosses zero. Therefore, it can be ensured that the bidirectional thyristor switch S1 is turned off more accurately when the actual zero-crossing signal is generated. The turn-off time of the bidirectional thyristor switch is as close as possible to the actual zero-crossing time of the AC power. Therefore, the transfer control of the AC motor 50 is more accurate. In the embodiment of the present application, by controlling the turn-off time and the turn-on time of the bidirectional thyristor switch S1, the AC motor 50 can be accurately controlled without increasing the hardware cost.

[0032] See also Figure 1 In some embodiments, the zero-crossing detection circuit module 80 includes an NPN transistor Q1, the base of the NPN transistor Q1 is connected to the AC power supply 60, specifically connected to the neutral line (ACN) of the AC power supply 60, the emitter of the NPN transistor Q1 is grounded, and the control chip 70 is provided with a first pin 101 ( Figure 1 The collector of the NPN transistor Q1 is connected to the first pin 101 of the control chip 70 and is used to output a zero-crossing signal to the first pin 101. Figure 2 , the NPN transistor Q1 is provided with a preset voltage value, and the preset voltage value is equal to the cut-off voltage of the NPN transistor Q1. As a specific example, in the present embodiment, the cut-off voltage of the NPN transistor Q1 is 0.7V, so the preset voltage value is 0.7V. When the AC voltage of the AC power supply 60 is less than or equal to the preset voltage value, the collector of the NPN transistor Q1 outputs a zero-crossing signal to the control chip 70; the control chip 70 is used to generate a control waveform L2 according to the zero-crossing signal, wherein when the voltage of the AC power supply 60 is greater than the preset voltage value, the control waveform L2 is at a low level, and when the voltage of the AC power supply 60 is less than or equal to the preset voltage value, the control waveform L2 is at a high level, and when the zero-crossing signal corresponding to the AC signal L1 from the positive half cycle to the negative half cycle is triggered ( Figure 2 The control waveform L2 presents a rising edge, and the control chip 70 is also used to control the bidirectional thyristor switch S1 to work according to the control waveform L2. Specifically, when the control waveform L2 presents a rising edge ( Figure 2 At point A in the middle, the control chip 70 sends a shutdown signal to the bidirectional thyristor switch S1. At this time, the voltage of the AC signal L1 ( Figure 2 Point C in the middle) is equal to the cut-off voltage of the NPN transistor Q1 and is in a decreasing state. Therefore, the moment A when the control chip 70 sends a shutdown signal to the bidirectional thyristor S1 is ahead of the actual zero-crossing moment B of the AC signal L1. Therefore, when the AC signal L1 actually generates a zero-crossing signal, the bidirectional thyristor S1 can be turned off more accurately, thereby realizing precise speed regulation of the AC motor 50.

[0033] See also Figure 2In some embodiments, the control chip 70 is provided with a timer (not shown in the figure), and the timer is used to alternately count the first preset duration and the second preset duration. The control chip 70 is used to control the bidirectional thyristor S1 to turn off and on according to a predetermined period, and the bidirectional thyristor S1 is kept off for the first preset duration and kept on for the second preset duration in the predetermined period. The first preset duration and the second preset duration are both integer multiples of the period of the alternating current emitted by the AC power supply. As a specific example, assuming that the period of the alternating current is T, the predetermined period is Z*T, the first preset duration is X*T, and the second preset duration is Y*T, where Z=X+Y, and X, Y, and Z are all positive integers. In the first predetermined period, the control chip 70 first controls the bidirectional thyristor S1 to remain off for the first preset duration, and then controls the bidirectional thyristor S1 to remain on for the second preset duration, continues to enter the second predetermined period, and repeats the above process. Through the above settings, the control chip 70 can achieve precise regulation of the speed of the AC motor 50 by precisely controlling the on-time (second preset time) and off-time (first preset time) of the bidirectional thyristor switch S1 in each predetermined period. Its speed regulation logic can be understood as: when the predetermined period is fixed, the larger the value of the first preset time, the longer the off-time of the bidirectional thyristor switch S1, and the smaller the speed of the AC motor 50. Among them, the three data of the predetermined period, the first preset time and the second preset time need to be pre-calculated by the staff through experiments, and written into the control chip 70 as parameters of the control program in advance. The specific values ​​of the three data of the predetermined period, the first preset time and the second preset time can change with the change of the speed regulation demand.

[0034] See also Figure 2 and Figure 3 In some embodiments, the timer is specifically used to start timing at a rising edge of the control waveform L2, and end timing at the next rising edge of the control waveform L2 to obtain the cycle of the AC current. For example, the timer is Figure 2 Start from point A in Figure 2The control chip 70 is used to send a first control signal to the bidirectional thyristor S1 at a rising edge of the control waveform L2 to turn off the bidirectional thyristor S1, and at the same time, the timer starts to count the first preset time. When the timer reaches the first preset time, the control chip 70 sends a second control signal to the bidirectional thyristor S1 to turn on the bidirectional thyristor S1, and at the same time, the timer starts to count the second preset time. When the timer reaches the second preset time, the control chip 70 sends the first control signal to the bidirectional thyristor S1 to turn off the bidirectional thyristor S1 again. It should be noted that the bidirectional thyristor switch S1 can only be turned off when the AC current passes through zero, and in order to ensure that the bidirectional thyristor switch S1 is accurately turned off, the control chip 70 must issue a switch shutdown command at the rising edge of the control waveform L2. Because the rising edge of the control waveform L2 is ahead of the actual zero-crossing moment of the falling edge of the AC signal L1, the bidirectional thyristor switch S1 can be turned off more accurately at the actual zero-crossing moment of the falling edge of the AC signal L1 after receiving the shutdown signal, thereby achieving precise speed regulation of the AC motor 50.

[0035] See also Figure 1 In some embodiments, the AC motor speed control device 100 further includes a conversion circuit module 40, and the control chip 70 is provided with a second pin 102 ( Figure 1 The conversion circuit module 40 is connected between the AC power supply 60 and the second pin 102 of the control chip 70, and is used to convert the AC power output by the AC power supply 60 into DC power and provide it to the control chip 70. The conversion circuit module 40 is a circuit module commonly used in the prior art for converting AC power into DC power, so it is not described in detail here. Through the above arrangement, the AC power supply 60 can provide AC power to the zero-crossing detection circuit module 80 to ensure that the zero-crossing detection circuit module 80 can work normally, and can also provide DC power to the control chip 70 to ensure that the control chip 70 can work normally.

[0036] In some embodiments, the conversion circuit module 40 is also connected between the AC power supply 60 and the collector of the NPN transistor Q1, and is used to convert the AC power output by the AC power supply 60 into DC power and provide it to the zero-crossing detection circuit module 80. Through the above configuration, the AC power supply 60 provides AC power to the base of the NPN transistor Q1 and provides DC power to the collector of the NPN transistor Q1 to ensure that the NPN transistor Q1 can be smoothly turned on and off, thereby realizing zero-crossing detection of the AC signal. In other embodiments, the AC motor speed control device 100 can also be provided with a DC power supply (not shown in the figure) instead of the conversion circuit module 40, and the DC power supply is respectively connected to the second pin 102 of the control chip 70 and the collector of the NPN transistor Q1.

[0037] In some embodiments, the zero-crossing detection circuit module 80 further includes a first current limiting resistor R1 and a second current limiting resistor R2, wherein the first current limiting resistor R1 is connected in series between the collector of the NPN transistor Q1 and the second pin 102, and an end of the first current limiting resistor R1 away from the collector of the NPN transistor Q1 is connected to the output end of the conversion circuit module 40. The second current limiting resistor R2 is connected in series between the collector of the NPN transistor Q1 and the first pin 101. The first current limiting resistor R1 is used to prevent the current flowing through the collector of the NPN transistor Q1 and the second pin 102 from being too large, so as to protect the collector of the NPN transistor Q1 and the second pin 102. The second current limiting resistor R2 is used to prevent the current flowing through the collector of the NPN transistor Q1 and the first pin 101 from being too large, so as to protect the collector of the NPN transistor Q1 and the first pin 101.

[0038] Please continue reading Figure 1 In some embodiments, the zero-crossing detection circuit module 80 further includes a first voltage-dividing resistor R3, a second voltage-dividing resistor R4, and a third voltage-dividing resistor R5. The first voltage-dividing resistor R3 and the second voltage-dividing resistor R4 are sequentially connected in series between the base of the NPN transistor Q1 and the AC power supply 60, and the first voltage-dividing resistor R3 and the second voltage-dividing resistor R4 are specifically connected in series between the base of the NPN transistor Q1 and the zero line (ACN) of the AC power supply 60. The two ends of the third voltage-dividing resistor R5 are respectively connected to the base and the emitter of the NPN transistor Q1. Specifically, the first end of the third voltage-dividing resistor R5 is connected to the common connection point of the second voltage-dividing resistor R4 and the base of the NPN transistor Q1, and the second end of the third voltage-dividing resistor R5 is grounded. The first voltage-dividing resistor R3, the second voltage-dividing resistor R4, and the third voltage-dividing resistor R5 work together to divide the high-voltage AC outputted by the AC power supply 60 into a voltage that the NPN transistor Q1 can withstand, thereby protecting the safety of the NPN transistor Q1.

[0039] In some embodiments, the zero-crossing detection circuit module 80 further includes a filter capacitor C, which is connected in parallel to both ends of the third voltage-dividing resistor R5. Specifically, both ends of the filter capacitor C are connected to the first end and the second end of the third voltage-dividing resistor R5, respectively. The filter capacitor C is used to reduce the interference of the AC ripple coefficient on the circuit, and can also absorb the current fluctuations generated during the operation of the circuit and the interference connected via the AC power supply 60, so that the working performance of the circuit is more stable.

[0040] Please continue reading Figure 1 In some embodiments, the first main pole of the bidirectional thyristor switch S1 is used to connect the AC motor 50, the second main pole of the bidirectional thyristor switch S1 is connected to the AC power supply 60, and the control chip 70 is provided with a third pin 103 ( Figure 1The gate of the bidirectional thyristor S1 is connected to the third pin 103. Through the above configuration, the control chip 70 inputs a control signal to the bidirectional thyristor S1 after receiving the zero-crossing signal to control the turning off and on of the bidirectional thyristor S1, and by controlling the turning off time and the turning on time of the bidirectional thyristor S1, different speed regulation of the AC motor 50 can be achieved.

[0041] In some embodiments, the speed regulating circuit module 30 further includes a third current limiting resistor R6, which is connected in series between the gate of the bidirectional thyristor switch S1 and the third pin 103. The third current limiting resistor R6 can prevent excessive current flowing through the bidirectional thyristor switch S1 and the third pin 103, thereby protecting the bidirectional thyristor switch S1 and the control chip 70.

[0042] In some embodiments, there are multiple bidirectional thyristor switches S1, the number of the third pins 103 of the control chip 70 is the same as the number of the bidirectional thyristor switches S1, and the gates of the multiple bidirectional thyristor switches S1 are connected to the multiple third pins 103 of the control chip 70 in a one-to-one correspondence. Figure 1 In the embodiment, the number of bidirectional thyristor switches S1 is three, the number of the third current limiting resistor R6 and the third pin 103 of the control chip 70 is also three, and the first main electrodes of the three bidirectional thyristor switches S1 are respectively connected to the three pins of the AC motor 50 ( Figure 1 The second main electrodes of the three bidirectional thyristors S1 are connected to the live wire (ACL) of the AC power source 60, and the gate electrodes of the three bidirectional thyristors S1 are connected to the three third pins 103 ( Figure 1 In the embodiment, the pins 4, 3, and 2 of the AC motor 50 correspond to the three speed modes of high speed, medium speed, and low speed, respectively. At any time, the AC motor 50 can only be in one of the speed modes of high speed, medium speed, and low speed. In the above three speed modes, the control chip 70 can further adjust the speed in different speed modes of high speed, medium speed, and low speed by controlling the on-time and off-time of the corresponding bidirectional thyristor S1, thereby adjusting more speed gears of the AC motor 50. In other embodiments, the number of bidirectional thyristors S1 can also be any number such as two, four, or five. The specific number of bidirectional thyristors S1 needs to be consistent with the number of corresponding pins of the AC motor 50, and the number of the third pins 103 of the control chip 70 and the number of the third current limiting resistors R6 need to be the same as the number of bidirectional thyristors S1.

[0043] In summary, the present embodiment provides an AC motor speed control device 100, which is provided with a zero-crossing detection circuit module 80 to obtain the zero-crossing signal of the AC power supply 60 and transmit it to the control chip 70. The control chip 70 outputs a control signal to the speed control circuit module 30 according to the zero-crossing signal. The control signal is used to control the conduction and disconnection of the bidirectional thyristor switch S1, thereby controlling the on-off of the current of the AC motor 50. Specifically, when the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered, the control chip 70 can send a shutdown signal to the bidirectional thyristor switch S1. Since the triggering moment of the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is ahead of the actual falling edge zero-crossing signal, and the bidirectional thyristor switch S1 can only be turned off when the AC signal actually crosses zero, it can ensure that the bidirectional thyristor switch S1 is more accurately turned off when the actual zero-crossing signal is generated. By controlling the off time and the on time of the bidirectional thyristor switch S1, the AC motor 50 can be accurately controlled without increasing the hardware cost. The above-mentioned AC motor speed control device 100 is analyzed from the perspective of the defects of the current circuit design itself, and a new AC motor 50 speed control scheme logic is proposed without increasing the hardware cost and design difficulty. It makes up for the problem of low stability of products (such as electric fans) caused by the current circuit design defects, and achieves the purpose of improving product reliability.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application is described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not drive the essence of the corresponding technical solutions out of the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An AC motor speed control device, characterized in that: The AC motor speed regulating device comprises: Control chip; a zero-crossing detection circuit module, one end of which is used to receive an AC signal from an AC power source, and the other end of which is connected to the control chip, and the zero-crossing detection circuit module is used to obtain the zero-crossing moment of the AC signal to generate a zero-crossing signal, and transmit the zero-crossing signal to the control chip; and A speed regulation circuit module is connected to the control chip and is used to be connected to the AC motor. The control chip outputs a control signal to the speed regulation circuit module according to the zero-crossing signal. The speed regulation circuit module is provided with a bidirectional thyristor switch; the bidirectional thyristor switch is used to control the disconnection of the current of the AC motor when the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered.

2. The AC motor speed regulating device according to claim 1, characterized in that: The zero-crossing detection circuit module includes an NPN transistor, the base of the NPN transistor is connected to the AC power supply, the emitter of the NPN transistor is grounded, the control chip is provided with a first pin, the collector of the NPN transistor is connected to the first pin of the control chip and is used to output the zero-crossing signal to the first pin.

3. The AC motor speed regulating device according to claim 2, characterized in that: The NPN transistor is provided with a preset voltage value, and the preset voltage value is equal to the cut-off voltage of the NPN transistor. When the AC voltage of the AC power supply is less than or equal to the preset voltage value, the collector of the NPN transistor outputs the zero-crossing signal to the control chip; the control chip is used to generate a control waveform according to the zero-crossing signal, wherein when the voltage of the AC power supply is greater than the preset voltage value, the control waveform is at a low level, and when the voltage of the AC power supply is less than or equal to the preset voltage value, the control waveform is at a high level, and when the zero-crossing signal corresponding to the AC signal from the positive half cycle to the negative half cycle is triggered, the control waveform presents a rising edge, and the control chip is also used to control the bidirectional thyristor switch to operate according to the control waveform.

4. The AC motor speed regulating device according to claim 3, characterized in that: The control chip is provided with a timer, and the timer is used to alternately time a first preset time and a second preset time; the control chip is used to control the bidirectional thyristor to be turned off and on according to a preset period, and the bidirectional thyristor switch remains turned off for the first preset time and remains on for the second preset time within the predetermined period; the first preset time and the second preset time are both integer multiples of the period of the AC current emitted by the AC power supply.

5. The AC motor speed regulating device according to claim 4, characterized in that: The timer is used to start timing at a rising edge of the control waveform and end timing at the next rising edge of the control waveform to obtain the cycle of the alternating current; the control chip is used to send a first control signal to the bidirectional thyristor switch at a rising edge of the control waveform to turn off the bidirectional thyristor switch, and at the same time the timer starts timing the first preset time. When the timer reaches the first preset time, the control chip sends a second control signal to the bidirectional thyristor switch to turn on the bidirectional thyristor switch, and at the same time the timer starts timing the second preset time. When the timer reaches the second preset time, the control chip sends the first control signal to the bidirectional thyristor switch to turn off the bidirectional thyristor switch again.

6. The AC motor speed regulating device according to claim 2, characterized in that: The AC motor speed regulation device also includes a conversion circuit module. The control chip is provided with a second pin. The conversion circuit module is connected between the AC power supply and the second pin of the control chip and is used to convert the AC power output by the AC power supply into DC power and provide it to the control chip.

7. The AC motor speed regulating device according to claim 6, characterized in that: The conversion circuit module is also connected between the AC power source and the collector of the NPN transistor, and is used to convert the AC power output by the AC power source into DC power and provide it to the zero-crossing detection circuit module.

8. The AC motor speed regulating device according to claim 7, characterized in that: The zero-crossing detection circuit module also includes a first current limiting resistor and a second current limiting resistor, wherein the first current limiting resistor is connected in series between the collector of the NPN transistor and the second pin, and the second current limiting resistor is connected in series between the collector of the NPN transistor and the first pin.

9. The AC motor speed regulating device according to claim 8, characterized in that: The zero-crossing detection circuit module also includes a first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor. The first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between the base of the NPN transistor and the AC power supply in sequence, and the two ends of the third voltage-dividing resistor are respectively connected to the base and emitter of the NPN transistor.

10. The AC motor speed regulating device according to claim 9, characterized in that: The zero-crossing detection circuit module further includes a filter capacitor, which is connected in parallel to both ends of the third voltage divider resistor.

11. The AC motor speed regulating device according to claim 1, characterized in that: The first main pole of the bidirectional thyristor is used to connect the AC motor, the second main pole of the bidirectional thyristor is connected to the AC power supply, the control chip is provided with a third pin, and the gate of the bidirectional thyristor is connected to the third pin.

12. The AC motor speed regulating device according to claim 11, characterized in that: The speed regulation circuit module further includes a third current limiting resistor, which is connected in series between the gate of the bidirectional thyristor switch and the third pin.

13. The AC motor speed regulating device according to claim 11, characterized in that: There are multiple bidirectional thyristors, the number of the third pins of the control chip is the same as the number of the bidirectional thyristors, and the gates of the multiple bidirectional thyristors are connected to the multiple third pins of the control chip in a one-to-one correspondence.

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