A method for controlling the rotational speed of an electric motor

Abstract

The method for controlling the rotating speed of the motor comprises the following steps: obtaining the initial current value and the actual current value of the motor when the motor is idle and when the motor is running respectively by means of current sampling points in a preset period, so as to obtain the maximum change value and the minimum change value in the actual current change value in the preset period; obtaining the effective current change value and the maximum effective current change value of the motor in the preset period based on the difference between the actual current change value and the minimum change value and the difference between the maximum change value and the minimum change value; and obtaining the rotating speed information of the motor corresponding to the actual output power of the motor based on the actual output power of the motor under the actual power output ratio and the power factor of the actual maximum available power of the motor. The state of the rotating speed adjusting unit is automatically adjusted by the master control chip, so that the motor always operates at the best working point.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of motor control, and in particular to a motor speed control method. BACKGROUND

[0002] In the field of modern industrial automation, household appliances, and transportation tools, motors serve as an important power source, and the precision of their speed control directly affects the overall performance and efficiency of the system. Traditional motor speed control methods mainly include the following: controlling motor speed by setting a fixed power supply voltage, which is simple but lacks flexibility and cannot adapt to complex load changes. Adjusting the input voltage or current of the motor using PWM signals to change the speed. Although PWM control has high response speed and good dynamic characteristics, it can produce noise at low speeds and has limited adaptability to load changes. Combining sensor detection of the actual motor speed with a pre-set target, and adjusting the drive signal through a PID algorithm to achieve the desired speed. However, this solution relies on high-precision sensors, increasing system cost and complexity. SUMMARY

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a motor speed control method to solve the problems in the related art.

[0004] The first aspect of the present disclosure provides a motor speed control method, wherein the motor is controlled in speed by a motor control circuit, and the motor control circuit comprises:

[0005] a power supply interface including a positive terminal and a negative terminal; the positive terminal of the power supply interface is coupled to a first end of the motor via a speed regulation unit, and the negative terminal of the power supply interface is coupled to a second end of the motor via a switching element;

[0006] a master control chip including a chip regulation end, a chip control end, a chip feedback end, and a current detection end; the chip regulation end is coupled to a regulation circuit for receiving motor speed information output by the regulation circuit; the chip control end is coupled to a control end of the speed regulation unit via a first resistor for controlling the on / off of the speed regulation unit according to the speed information; the chip feedback end is coupled to another end of the speed regulation unit via a feedback circuit for detecting the conduction state of the speed regulation unit; and the current detection end is coupled to the speed regulation unit via a current detection circuit, and the current detection circuit is coupled to a current sampling point between the positive terminal and the first end of the motor;

[0007] wherein the master control chip applies the control method, including:

[0008] The initial current value and the actual current value of the motor when idle and when running are obtained through the current sampling point in a preset period;

[0009] The actual current change value of the motor in the preset period is obtained based on the initial current value and the actual current value, to obtain the maximum change value and the minimum change value in the actual current change value in the preset period;

[0010] The effective current change value and the maximum effective current change value of the motor in the preset period are obtained based on the difference between the actual current change value and the minimum change value, and the difference between the maximum change value and the minimum change value;

[0011] The actual output power of the motor under the actual power output ratio and the power factor based on the actual maximum available power of the motor, and the motor speed information corresponding to the actual output power are obtained; wherein the actual power output ratio is the ratio of the effective current change value to the maximum effective current change value.

[0012] In an embodiment of the first aspect, the initial current value and the actual current value of the motor when idle and when running are obtained through the current sampling point in a preset period, comprising:

[0013] In the preset period, the current value of the motor is collected through the current sampling end when the motor is idle, to obtain the first maximum current value and the first minimum current value in the preset period, and the initial current value is obtained based on the difference between the first maximum current value and the first minimum current value;

[0014] In the preset period, the current value of the motor is collected through the current sampling end when the motor is in running state, to obtain the second maximum current value and the second minimum current value in the preset period, and the actual current value is obtained based on the difference between the second maximum current value and the second minimum current value.

[0015] In an embodiment of the first aspect, an amplification circuit is further provided between the current detection end and the current sampling point, and the initial current value and the actual current value of the motor when idle and when running are obtained through the current sampling point in a preset period, comprising:

[0016] In the preset period, the current value of the motor in idle state and running state is obtained through the current sampling circuit, and output to the amplification circuit through the current sampling point;

[0017] The collected current value is amplified and output to the current detection end through the amplification circuit;

[0018] The initial current value and the actual current value are obtained according to the difference between the maximum current value and the minimum current value after amplification under the idle state and the running state in the preset period.

[0019] In an embodiment of the first aspect, the actual output power is a product of the power factor and the actual power output ratio and the actual maximum available power.

[0020] In an embodiment of the first aspect, the obtaining of the speed information of the motor corresponding to the actual output power comprises:

[0021] Based on the actual output power, a ratio of the actual output power to the maximum power of the motor is obtained, and the speed information of the motor in the preset period is obtained according to the ratio.

[0022] In an embodiment of the first aspect, the current detection circuit comprises a second resistor and a third resistor.

[0023] One end of the second resistor is coupled to the current detection end, and the other end of the second resistor is coupled to the positive end through the third resistor, and the third resistor is coupled to the first end of the motor through the speed regulation unit.

[0024] In an embodiment of the first aspect, the regulation circuit comprises:

[0025] A variable resistor, one end of the variable resistor is coupled to a reference power supply, the other end of the variable resistor is grounded, and the adjustable end of the variable resistor is coupled to the chip regulation end, and the chip regulation end generates the speed information according to the resistance value of the variable resistor.

[0026] In an embodiment of the first aspect, the master control chip further comprises a chip power supply end, and the chip power supply end is coupled to a power supply circuit; the feedback circuit comprises:

[0027] A fourth resistor, one end of the fourth resistor is coupled to the output end of the power supply circuit, and the other end of the fourth resistor is coupled to the first end of the motor through a fifth resistor, and a voltage dividing point between the fourth resistor and the fifth resistor leads to the chip feedback end.

[0028] In an embodiment of the first aspect, the master control chip further comprises a chip power supply end, and the chip power supply end is coupled to a power supply circuit; the power supply circuit comprises at least one of the following elements:

[0029] A voltage stabilizing diode, the positive electrode of the voltage stabilizing diode is coupled to the negative end, and the negative electrode of the voltage stabilizing diode is coupled to the positive end.

[0030] a storage capacitor, the positive electrode of the storage capacitor being coupled to the chip power supply end, and the negative electrode of the storage capacitor being grounded;

[0031] a first diode, the positive electrode of the first diode being coupled to the negative electrode of the storage capacitor, and the negative electrode of the first diode being coupled to the negative electrode end via a sixth resistor.

[0032] In an embodiment of the first aspect, the rotation speed adjusting unit comprises a bidirectional thyristor.

[0033] Advantages of the present disclosure: by setting a current sampling point between the power supply interface and the motor, the initial current value and the actual current value in the idle state and the running state of the motor are obtained in real time, and through the application of the master control chip, the state of the rotation speed adjusting unit is automatically adjusted, so that the motor always runs at the best working point, and the stability and efficiency of the system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A structural block diagram of a motor control circuit in an embodiment of the present disclosure is shown.

[0035] Figure 2 A circuit connection schematic diagram of a motor control circuit in an embodiment of the present disclosure is shown.

[0036] Figure 3 A flowchart of a control method of a motor rotation speed in an embodiment of the present disclosure is shown.

[0037] Figure 4 A flowchart of obtaining an initial current value and an actual current value in a control method of a motor rotation speed in an embodiment of the present disclosure is shown.

[0038] Figure 5 A flowchart of obtaining an initial current value and an actual current value in a control method of a motor rotation speed in another embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0039] The embodiments of the present disclosure will be described in detail below with specific examples. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the messages disclosed in the present disclosure. The present disclosure can also be implemented or applied by different specific embodiments and application modules, and the details in the present disclosure can be modified or changed according to different views and application modules without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0040] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings, so that those skilled in the art to which the present disclosure pertains can easily implement the present disclosure. The present disclosure can be embodied in various ways, and is not limited to the embodiments described herein.

[0041] In the present disclosure, the expressions of "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. Also, the specific features, structures, materials or characteristics represented can be combined in any appropriate manner in any one or a group of embodiments or examples. In addition, the different embodiments or examples represented in the present disclosure and the features of the different embodiments or examples can be combined and integrated by those skilled in the art without contradiction, if necessary.

[0042] In addition, the terms "first", "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the present disclosure, the meaning of "a group" is two or more, unless specifically limited otherwise.

[0043] In order to clearly explain the present disclosure, the devices irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar constituent elements throughout the specification.

[0044] In the entire specification, when it is said that a device is "connected" to another device, it includes not only the case of "direct connection", but also the case of "indirect connection" in which other elements are interposed therebetween. In addition, when it is said that a device "includes" a certain constituent element, unless specifically stated to the contrary, other constituent elements are not excluded, but it means that other constituent elements can also be included.

[0045] Although the terms first, second, etc. are used herein to refer to various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first interface and a second interface, etc. are distinguished from each other. Also, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including" specify the presence of stated features, steps, operations, elements, modules, items, components, and / or groups thereof but do not preclude the presence or addition of one or more other features, steps, operations, elements, modules, items, components, and / or groups thereof. As used herein, the terms "or" and "and / or" are construed to be inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Exceptions to this definition are only present when elements, functions, steps or operations are inherently mutually exclusive between some versions and not others.

[0046] The professional terms used herein are only used to refer to specific embodiments and are not intended to limit the disclosure. The singular form used herein, unless the context clearly indicates otherwise, also includes the plural form. The meaning of "comprising" used in the specification is to specify a particular feature, area, integer, step, operation, element and / or component, and not to exclude the presence or addition of other features, areas, integers, steps, operations, elements and / or components.

[0047] Although not differently defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms defined in commonly used dictionaries are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, unless defined otherwise, and should not be interpreted in an idealized or overly formal sense.

[0048] The existing control system has a slow response speed to load changes, and cannot timely adjust the working state of the motor to respond to sudden load changes. This leads to the fact that in actual applications, especially in scenarios that require frequent start-stop or have large load fluctuations, the efficiency and performance of the motor are affected.

[0049] The first aspect of the present disclosure provides a control method for the rotating speed of a motor, wherein the motor is controlled in rotating speed by a motor control circuit, and a main control chip acquires initial current values and actual current values of the motor when idle and when running respectively through current sampling points in each preset period. This method ensures accurate monitoring of the working state of the motor.

[0050] In Figure 1In an embodiment, the motor 100 comprises:

[0051] The power interface 200 comprises: a positive terminal 201 and a negative terminal 202; the positive terminal 201 of the power interface 200 is coupled to the first end of the motor 100 via a speed regulation unit 300, and the negative terminal 202 of the power interface 200 is coupled to the second end of the motor 100 via a switching element 400;

[0052] The main control chip 500 comprises a chip regulation end 501, a chip control end 502, a chip feedback end 503, and a current detection end 504; the chip regulation end 501 is coupled to an adjustment circuit 600 for receiving the speed information of the motor 100 output by the adjustment circuit 600; the chip control end 502 is coupled to the control end of the speed regulation unit 300 via a first resistor R1 for controlling the on / off of the speed regulation unit 300 according to the speed information; the chip feedback end 503 is coupled to the other end of the speed regulation unit 300 via a feedback circuit 700 for detecting the conduction state of the speed regulation unit 300; and the current detection end 504 is coupled to the speed regulation unit 300 via a current detection circuit 800, and the current detection circuit 800 is coupled to a current sampling point between the positive terminal 201 and the first end of the motor 100.

[0053] Specifically, the adjustment circuit 600 outputs the speed information that the motor 100 needs to reach according to actual needs, ensuring that the system can flexibly adjust the speed of the motor 100 according to different application scenarios. The adjustment circuit 600 outputs the speed information that the motor 100 needs to reach according to actual needs, ensuring that the system can flexibly adjust the speed of the motor 100 according to different application scenarios. At the same time, the main control chip 500 detects the conduction state of the speed regulation unit 300 in real time through the chip feedback end 503, ensuring the stable operation of the system.

[0054] Optionally, the current detection circuit 800 comprises a second resistor R2 and a third resistor R3.

[0055] One end of the second resistor R2 is coupled to the current detection end 504, and the other end of the second resistor R2 is coupled to the positive terminal 201 via the third resistor R3, and the third resistor R3 is coupled to the first end of the motor 100 via the speed regulation unit 300.

[0056] Specifically, in some embodiments, when the motor 100 is running, the current flows through the path formed by the second resistor R2 and the third resistor R3. Since the voltage drop across a resistor is proportional to the current, the master control chip 500 can calculate the current size of the motor 100 by measuring the voltage difference across the second resistor R2. The master control chip 500 monitors the current of the motor 100 in real time through the current detection end 504, ensuring that the motor 100 can operate stably under different load conditions. If an abnormal situation (such as too large or too small current) is detected, the master control chip 500 will take immediate action, such as adjusting the conduction angle of the speed regulation unit 300 or triggering an alarm, to protect the motor 100 and the system from damage. A first capacitor C1 is also provided in parallel with the third resistor R3 for filtering.

[0057] When the load driven by the motor 100 increases, the motor 100 needs to consume more power to overcome greater resistance to do work, which will cause the current flowing through the motor 100 winding to increase. Conversely, if the load decreases, the required current will also decrease accordingly. When the load of the motor 100 suddenly increases, due to the lack of effective power regulation mechanism, the motor speed will decrease significantly, and even may enter the locked-rotor state. At this time, the motor 100 winding current rises sharply, generating a large amount of heat, which can cause the motor 100 to be damaged and shorten its service life. To solve the above problems, in Figure 3 In an embodiment, a motor speed control method is provided, and the master control chip 500 applies the control method, which includes:

[0058] Step S1: Within a preset period, the initial current value and the actual current value of the motor 100 when idle and when running are obtained through the current sampling points respectively.

[0059] Specifically, in some embodiments, the initial current value when the motor 100 is idle is recorded, providing a comparison benchmark for subsequent current changes during actual operation, to eliminate errors. The actual current value reflects the mechanical load condition of the motor 100. When the load increases, the motor 100 needs to consume more power to overcome resistance, resulting in an increase in current; conversely, when the load decreases, the current decreases. By continuously monitoring the actual current value, the working state of the motor 100 and the trend of its load change can be understood in a timely manner.

[0060] Optionally, in some embodiments, as Figure 4 In an embodiment, the initial current value and the actual current value of the motor 100 when idle and when running are obtained through the current sampling points respectively within a preset period, which includes:

[0061] Step S111: During the preset period, when the motor 100 is idle, the current value of the motor 100 is collected through the current sampling end to obtain a first maximum current value and a first minimum current value in the preset period, and the initial current value is obtained according to the difference between the first maximum current value and the first minimum current value.

[0062] Step S112: During the preset period, when the motor 100 is in a running state, the current value of the motor 100 is collected through the current sampling end to obtain a second maximum current value and a second minimum current value in the preset period, and the actual current value is obtained according to the difference between the second maximum current value and the second minimum current value.

[0063] Specifically, during the preset period, when the motor 100 is in an idle state (i.e. unloaded or lightly loaded), the current value of the motor 100 is continuously collected through the current sampling end. Also during the preset period, but this time the motor 100 is in a running state (i.e. working state), the current value of the motor 100 is continuously collected through the current sampling end. In this application, current sampling is achieved through a resistor (commonly known as a shunt or sampling resistor). This sampling method is simple and low cost, but it is also susceptible to a variety of factors, resulting in errors in the measurement results. Therefore, the difference between the maximum current value and the minimum current value is used when calculating the initial current value and the actual current value. In a period, by the maximum and minimum value of the current value between each other to offset the possible fluctuation error, so that the difference is closer to the real current change. Because the actual current value may not be 0, therefore by subtracting the actual minimum value from the maximum value can obtain more accurate and effective initial current value of the motor idle state and the actual current value of the motor running state.

[0064] Optionally, in another embodiment, considering that the current value directly sampled from the current sampling end is too small, it is difficult to accurately obtain its change, then an amplification circuit can also be provided between the current detection end 504 and the current sampling point, then as Figure 5 In an embodiment, the initial current value and the actual current value of the motor 100 in idle and running states are obtained through the current sampling point in the preset period, including:

[0065] Step S121: During the preset period, the current values of the motor 100 in idle and running states are obtained through the current sampling circuit, and output to the amplification circuit through the current sampling point.

[0066] Step S122: The collected current value is amplified and output to the current detection end 504 through the amplification circuit.

[0067] Step S123: obtaining the initial current value and the actual current value according to the difference between the maximum current value and the minimum current value collected and amplified in the idle state and the running state respectively in the preset period.

[0068] Specifically, as shown in the embodiments, the motor control circuit collects the current by resistance sampling, but the original current signal collected by resistance sampling is usually weak, especially in the low load or idle state. The amplification circuit can amplify the weak current signal to a level that is easier to process. In this application, although there is no specific connection diagram of the amplification circuit, the amplification circuit also belongs to the protection scope of this application. Figure 2

[0069] Step S2: obtaining the actual current change value of the motor 100 in the preset period based on the initial current value and the actual current value, to obtain the maximum change value and the minimum change value in the actual current change value in the preset period.

[0070] Specifically, in some embodiments, in order to determine the change of the load of the motor 100, it is necessary to calculate the actual current change value from the idle state to the running state. The actual current change value is obtained by calculating the difference between the actual current value and the initial current value, and the initial current value is used as a reference. By subtracting the current value in the idle state from the current value in the running state, the change of the power is reflected.

[0071] In step S3, the effective current change value and the maximum effective current change value of the motor 100 in the preset period are obtained based on the difference between the actual current change value and the minimum change value, and the difference between the maximum change value and the minimum change value respectively.

[0072] Specifically, the difference between the actual current change value and the minimum change value is the effective current change value. By subtracting, the influence of the lowest current change in the period and the error can be removed, and a more stable reference value is obtained. The difference between the maximum change value and the minimum change value is the maximum effective current change value. The maximum effective current change value reflects the maximum current change between the maximum power state and the minimum power state of the motor 100 in the period.

[0073] Step S4: obtaining the speed information of the motor 100 corresponding to the actual output power based on the actual output power of the motor 100 under the actual power output ratio and the power factor, wherein the actual power output ratio is the ratio of the effective current change value to the maximum effective current change value.

[0074] ​Specifically, in some embodiments, the actual maximum available power is the difference between the maximum power (e.g. rated power) marked by the motor 100 or the maximum output power determined at the design time and the minimum power. The ratio of the effective current change value to the maximum effective current change value reflects the proportion of the power output relative to the maximum available power under the current working state, reflecting the working state of the motor 100 under different load conditions. The power factor represents the proportion of the actual effective power consumed to the apparent power. By calculating the proportional relationship between the effective current change value and the maximum effective current change value, it can be known how much the actual output power of the motor 100 is, where the actual output power is the product of the power factor, the actual power output proportion and the actual maximum available power.

[0075] Optionally, the obtaining of the speed information of the motor 100 corresponding to the actual output power comprises:

[0076] Based on the actual output power, the ratio of the actual output power to the maximum power of the motor 100 is obtained, and the speed information of the motor 100 in the preset period is obtained according to the ratio.

[0077] Specifically, in some embodiments, the speed information includes the on-time of the motor 100, and according to the ratio between the actual output power and the maximum power, it can be known whether the load of the motor 100 is increased or not, so as to decide whether the power output needs to be adjusted. By constantly monitoring and adjusting the actual output power, it can be ensured that the motor 100 stably operates at the required speed, meeting the application requirements. At the same time, it prevents the motor 100 from entering the locked-rotor state or overheating, prolonging the service life of the motor 100.

[0078] Optionally, in Figure 2 In an embodiment, the adjusting circuit 600 comprises:

[0079] The adjustable resistor RV1 has one end coupled to a reference power supply and the other end grounded, and the adjustable end of the adjustable resistor RV1 is coupled to the chip adjusting end 501, and the chip adjusting end 501 generates the speed information according to the resistance value of the adjustable resistor RV1.

[0080] Specifically, in some embodiments, the host chip 500 calculates the current resistance value by reading the voltage difference between the two ends of the adjustable resistor RV1. According to the pre-set mapping relationship, the host chip 500 converts the resistance value into corresponding speed information. The user can adjust the resistance value of the adjustable resistor RV1 in a manual or automatic manner, thereby changing the speed setting of the motor 100. For example, in the manual mode, the user can directly rotate the knob of the adjustable resistor RV1; in the automatic mode, the host chip 500 can automatically adjust the resistance value according to the pre-set program. In Figure 3In the embodiment, a third capacitor C3 is further provided, one end of the third capacitor C3 is coupled to the chip adjusting end 501, the other end of the third capacitor C3 is grounded, and the third capacitor C3 is used for filtering.

[0081] Optionally, in Figure 2 In the embodiment, the master control chip 500 further includes a chip power supply end 506 coupled to a power supply circuit; and the feedback circuit 700 includes:

[0082] A fourth resistor R4, one end of the fourth resistor R4 is coupled to the output end of the power supply circuit, the other end of the fourth resistor R4 is coupled to the first end of the motor 100 through a fifth resistor R5, and a voltage dividing point between the fourth resistor R4 and the fifth resistor R5 is led out as the chip feedback end 503. Optionally, in Figure 2 In the embodiment, the rotating speed adjusting unit 300 includes a bidirectional thyristor.

[0083] Specifically, in some embodiments, the bidirectional thyristor is a kind of bidirectional triggered semiconductor device, which can be turned on or turned off in two half cycles of alternating current. By changing the conduction time (i.e. conduction angle) of the bidirectional thyristor, the effective value of the input voltage of the motor 100 can be adjusted, thereby controlling the rotating speed of the motor 100. The fourth resistor R4 and the fifth resistor R5 constitute a voltage dividing circuit for detecting the conduction state of the bidirectional thyristor. When the bidirectional thyristor is turned on, current flows through the fourth resistor R4 and the fifth resistor R5, forming a voltage dividing point between them. The master control chip 500 reads the voltage value of the voltage dividing point through the chip feedback end 503, thereby determining the actual conduction state of the bidirectional thyristor. The master control chip 500 detects the conduction state of the bidirectional thyristor in real time through the chip feedback end 503, ensuring stable operation of the system. If an abnormal condition (such as a deviation of the conduction angle from the set value) is detected, the master control chip 500 will immediately adjust the control signal to restore the normal conduction state.

[0084] Optionally, in Figure 2 In the embodiment, the power supply circuit 800 includes at least one of the following elements:

[0085] A voltage stabilizing diode DW1, the positive electrode of the voltage stabilizing diode DW1 is coupled to the negative electrode end 202, and the negative electrode of the voltage stabilizing diode DW1 is coupled to the positive electrode end 201;

[0086] An energy storage capacitor CV1, which is connected in parallel with the voltage stabilizing diode DW1, the positive electrode of the energy storage capacitor CV1 is coupled to the chip power supply end 506, and the negative electrode of the energy storage capacitor CV1 is grounded;

[0087] A first diode D1, a positive electrode of the first diode D1 is coupled to a negative electrode of the energy storage capacitor CV1, and a negative electrode of the first diode D1 is coupled to the negative terminal 202 via a sixth resistor R6.

[0088] Specifically, in some embodiments, the role of the voltage stabilizing diode DW1 is to maintain the power supply voltage within a stable range, preventing voltage fluctuations from affecting the normal operation of the master chip 500 and other circuit elements. The role of the first diode D1 is to prevent reverse current from flowing into the power interface 200, protecting the circuit from damage. The sixth resistor R6 is used to limit the current and ensure the safe operation of the first diode D1. The energy storage capacitor CV1 is charged when the power supply voltage is stable, and discharged when the power supply voltage is temporarily reduced or powered off for a short time, ensuring that the master chip 500 receives continuous power supply. A second capacitor C2 is also provided in parallel with the voltage stabilizing diode DW1 for filtering.

[0089] Optionally, in Figure 2 In an embodiment, the master chip 500 further includes a protection terminal 505 coupled to the switching element 400 via a protection circuit; the protection circuit includes:

[0090] A seventh resistor R7, one end of the seventh resistor R7 is grounded, the other end of the seventh resistor R7 is coupled to the negative terminal 202 via an eighth resistor R8, the seventh resistor R7 and the eighth resistor R8 between the protection terminal 505 is drawn, the protection terminal 505 receives a level signal, the master chip 500 based on the level signal is high or high-low level change to determine the on-off state of the switching element 400, to set the off switching element 400 to on.

[0091] Specifically, in some embodiments, the seventh resistor R7 and the eighth resistor R8 constitute a voltage dividing circuit for detecting the on-off state of the switch element 400. When the switch element 400 is turned on, the protection terminal 505 of the master control chip 500 is led out through the voltage dividing point between the seventh resistor R7 and the eighth resistor R8. When the plug is connected to the socket, the master control chip 500 detects the level signal through the protection terminal 505, and if a square wave signal is detected, it means that the switch is in the on state. At this time, the master control chip 500 sends a start signal to the speed regulation unit 300 through the chip control terminal 502, to ensure that the motor 100 will not start immediately, preventing accidental injury. Then, the master control chip 500 waits for the user to manually turn on the switch again to start the motor 100. If a low level or a high level that does not reach the preset voltage value is detected, it means that the switch is in the off state, and at this time the motor 100 is not allowed to start. Only when the master control chip 500 detects a high level signal above the preset voltage value, will the motor 100 start when the switch element 400 is turned on again. This ensures that in any case, the motor 100 will only start after confirming that the switch element 400 has been properly turned on, improving safety. The main function of the protection unit is to prevent the plug from being connected while the switch is off, thereby avoiding the motor 100 from starting immediately and injuring people. By detecting the level signal, the master control chip 500 can intelligently determine the state of the switch element 400, ensuring that the motor 100 will not start immediately when the plug is inserted.

[0092] Optionally, in Figure 2 In embodiments, the protection circuit further comprises:

[0093] The fourth capacitor C4 is connected in parallel with the seventh resistor R7, for filtering high-frequency noise.

[0094] The above embodiments are only illustrative of the principles and effects of the present disclosure, and are not intended to limit the present disclosure. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present disclosure shall be covered by the protection scope of the present disclosure.

Claims

1. A method of controlling the rotational speed of an electric machine, characterized by, The motor is controlled in rotating speed by a motor control circuit, the motor control circuit comprises: a power interface comprising a positive terminal and a negative terminal, the positive terminal of the power interface is coupled to the first end of the motor via a rotating speed adjusting unit, the negative terminal of the power interface is coupled to the second end of the motor via a switch element; a master control chip comprising a chip adjusting terminal, a chip control terminal, a chip feedback terminal and a current detection terminal, the chip adjusting terminal is coupled to an adjusting circuit for receiving the rotating speed information of the motor outputted by the adjusting circuit, the chip control terminal is coupled to the control terminal of the rotating speed adjusting unit via a first resistor for controlling the on / off of the rotating speed adjusting unit according to the rotating speed information, the chip feedback terminal is coupled to the other end of the rotating speed adjusting unit via a feedback circuit for detecting the on state of the rotating speed adjusting unit, the current detection terminal is coupled to the rotating speed adjusting unit via a current detection circuit, the current detection circuit is coupled to a current sampling point between the positive terminal and the first end of the motor; wherein the master control chip applies the control method, comprising: acquiring an initial current value through the current sampling point when the motor is idle and acquiring an actual current value through the current sampling point when the motor is in operation within a preset period; obtaining the actual current change value of the motor within the preset period based on the initial current value and the actual current value, so as to obtain the maximum change value and the minimum change value in the actual current change value within the preset period; obtaining the effective current change value and the maximum effective current change value of the motor in the preset period based on the difference between the actual current change value and the minimum change value and the difference between the maximum change value and the minimum change value respectively; obtaining the rotating speed information of the motor corresponding to the actual output power of the motor based on the actual output power of the motor under the actual power output ratio and the power factor of the actual maximum available power of the motor.

2. The control method according to claim 1, characterized by, The acquisition of the initial current value and the actual current value of the motor when idle and in operation respectively through the current sampling point within the preset period comprises: acquiring the current value of the motor through the current sampling terminal when the motor is idle within the preset period to obtain the first maximum current value and the first minimum current value within the preset period, and obtaining the initial current value based on the difference between the first maximum current value and the first minimum current value; acquiring the current value of the motor through the current sampling terminal when the motor is in operation within the preset period to obtain the second maximum current value and the second minimum current value within the preset period, and obtaining the actual current value based on the difference between the second maximum current value and the second minimum current value.

3. The control method according to claim 1, characterized by, An amplification circuit is further arranged between the current detection end and the current sampling point, and the initial current value is obtained through the current sampling point when the motor is idle, and the actual current is obtained through the current sampling point when the motor is in operation within the preset period, comprising: Within the preset period, the current value of the motor in the idle state is obtained through the current sampling circuit; and The current value of the motor in the running state is obtained through the current sampling circuit, and the current value in the idle state and the current value in the running state are output to the amplification circuit through the current sampling point; The collected current value is amplified and output to the current detection end through the amplification circuit; Within the preset period, the initial current value and the actual current value are obtained according to the difference between the maximum current value and the minimum current value collected and amplified in the idle state and the running state, respectively.

4. The control method according to claim 1, characterized by, The actual output power is the product of the power factor, the actual power output ratio and the actual maximum available power.

5. The control method according to claim 1, characterized by, The speed information of the motor corresponding to the actual output power comprises: Based on the actual output power, the ratio of the actual output power to the maximum power of the motor is obtained, and the speed information of the motor within the preset period is obtained according to the ratio.

6. The control method according to claim 1, characterized by The current detection circuit comprises a second resistor and a third resistor; One end of the second resistor is coupled to the current detection end, and the other end of the second resistor is coupled to the positive end through the third resistor, and the third resistor is coupled to the first end of the motor through the speed regulation unit.

7. The control method according to claim 1, characterized by, The regulation circuit comprises: An adjustable resistor, one end of the adjustable resistor is coupled to a reference power supply, the other end of the adjustable resistor is grounded, and the adjustable end of the adjustable resistor is coupled to the chip regulation end, and the chip regulation end generates the speed information according to the resistance value of the adjustable resistor.

8. The control method according to claim 1, characterized by The main control chip further comprises a chip power supply end, and the chip power supply end is coupled to a power supply circuit; The feedback circuit comprises: A fourth resistor, one end of the fourth resistor is coupled to the output end of the power supply circuit, the other end of the fourth resistor is coupled to the first end of the motor through a fifth resistor, and the voltage dividing point between the fourth resistor and the fifth resistor leads to the chip feedback end.

9. The control method according to claim 1, characterized by, The main control chip further comprises a chip power supply end, and the chip power supply end is coupled to a power supply circuit; the power supply circuit comprises at least one of the following elements: A voltage stabilizing diode, the positive electrode of the voltage stabilizing diode is coupled to the negative electrode, and the negative electrode of the voltage stabilizing diode is coupled to the positive electrode; An energy storage capacitor is connected in parallel with the voltage stabilizing diode, the positive electrode of the energy storage capacitor is coupled to the chip power supply end, and the negative electrode of the energy storage capacitor is grounded; A first diode, the positive electrode of the first diode is coupled to the negative electrode of the energy storage capacitor, and the negative electrode of the first diode is coupled to the negative electrode through a sixth resistor.

10. The control method according to claim 1, characterized by, The speed regulation unit comprises a bidirectional thyristor.

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