CN216290746U - Stepless speed regulation circuit and module of alternating current motor and electrical equipment - Google Patents

Abstract

The utility model discloses a stepless speed regulation circuit, a module and electrical equipment of an alternating current motor. The utility model improves the accuracy of the stepless speed regulation of the alternating current motor.

Description

Stepless speed regulation circuit and module of alternating current motor and electrical equipment

Technical Field

The utility model relates to the field of speed regulation of alternating current motors, in particular to a stepless speed regulation circuit, a stepless speed regulation module and electrical equipment of an alternating current motor.

Background

The product motor control that uses AC motor as the load such as smoke ventilator, air conditioner, washing machine, dish washer, air purifier, electric fan in the present household electrical appliances product field is silicon controlled rectifier control with the traditional mode of speed governing, and silicon controlled rectifier is simple though control scheme, nevertheless because of its circuit is too simple, the speed governing is not accurate enough, has not satisfied the demand in high-end household electrical appliances market far away.

SUMMERY OF THE UTILITY MODEL

The utility model mainly aims to provide a stepless speed regulating circuit of an alternating current motor, aiming at improving the accuracy of stepless speed regulation of the alternating current motor.

In order to achieve the above object, the present invention provides an ac motor stepless speed regulating circuit, which comprises:

the rotating speed adjusting input end is used for accessing a rotating speed adjusting control signal;

the main control circuit is electrically connected with the rotating speed adjusting input end and is used for generating a corresponding driving signal according to the rotating speed adjusting control signal;

and the controlled end of the H-bridge control circuit is electrically connected with the main control circuit, and the H-bridge control circuit is used for performing power conversion on the power supply voltage accessed by the power supply end according to the driving signal and outputting the power supply voltage to the alternating current motor so as to drive the alternating current motor to rotate at a rotating speed corresponding to the rotating speed adjusting control signal.

Optionally, the main control circuit includes a main control chip and a driver chip, the main control chip is electrically connected to the input end of the rotation speed adjustment and the input end of the driver chip, respectively, and the output end of the driver chip is connected to the controlled end of the H-bridge control circuit.

Optionally, the main control chip and the driving chip are integrated in the same integrated chip.

Optionally, the stepless speed regulating circuit of the ac motor further includes a zero-crossing detection circuit, an input end of the zero-crossing detection circuit is connected to the power supply end, and an output end of the zero-crossing detection circuit is electrically connected to the main control circuit, and is configured to detect a voltage zero of a power supply voltage accessed by the power supply end, and output a zero detection signal to the main control circuit when the voltage zero is detected;

and the main control circuit is used for driving the H-bridge control circuit to work according to the zero detection signal so as to enable the time of the voltage zero of the alternating current voltage output by the H-bridge control circuit to be consistent with the time of the voltage zero of the power supply voltage.

Optionally, the stepless speed regulating circuit of the alternating current motor further comprises a temperature detection circuit, an output end of the temperature detection circuit is electrically connected with the main control circuit, and the temperature detection circuit is used for detecting the temperature of the H-bridge control circuit and outputting a temperature detection signal to the main control circuit;

and the main control circuit is used for stopping driving the H-bridge control circuit to work when the temperature of the H-bridge control circuit reaches a preset alarm temperature according to the temperature detection signal.

Optionally, the stepless speed regulating circuit of the alternating current motor further comprises a current detection circuit, a detection end of the current detection circuit is electrically connected with the alternating current motor, and an output end of the current detection circuit is electrically connected with the main control circuit; the current detection circuit is used for detecting the working current flowing through the alternating current motor and outputting a current detection signal to the main control circuit;

and the main control circuit is used for controlling the H-bridge control circuit to stop driving the alternating current motor to rotate when the working current of the alternating current motor is determined to be larger than the preset alarm current according to the current detection signal.

Optionally, the current detection circuit is further configured to detect a working current flowing through the ac motor, and output an overcurrent protection signal to the main control circuit when it is determined that the working current of the ac motor is greater than the preset alarm current;

and the main control circuit is used for controlling the H-bridge control circuit to stop driving the alternating current motor to rotate when receiving the overcurrent protection signal.

Optionally, the stepless speed regulating circuit of the alternating current motor further comprises an indicating circuit, and an input end of the indicating circuit is electrically connected with the main control circuit; and the main control circuit is used for controlling the indicating circuit to indicate the rotating speed of the alternating current motor corresponding to the rotating speed adjusting control signal according to the rotating speed adjusting control signal.

The utility model also provides an alternating current motor stepless speed regulation module which comprises a circuit board and the alternating current motor stepless speed regulation circuit as claimed in the above claim; wherein the content of the first and second substances,

the alternating current motor stepless speed regulating circuit is arranged on the circuit board.

The utility model provides electrical equipment, which comprises an alternating current motor, a shell and the stepless speed regulation module of the alternating current motor as claimed in claim 9; wherein the content of the first and second substances,

the alternating current motor stepless speed regulation module is accommodated in the shell and electrically connected with the alternating current motor so as to drive the alternating current motor to work.

The stepless speed regulating circuit of the alternating current motor is provided with a rotating speed regulating input end for accessing a rotating speed regulating control signal, so that a main control circuit generates a corresponding driving signal according to the rotating speed regulating control signal to drive an H-bridge control circuit to carry out power supply conversion on power supply voltage accessed by a power supply end and output the power supply voltage to the alternating current motor, and the alternating current motor is driven to rotate at a rotating speed corresponding to the rotating speed regulating control signal. Therefore, stepless speed regulation of the alternating current motor is realized, and the accuracy of speed regulation is improved. Meanwhile, the heating power consumption of the alternating current motor in the stepless speed regulation process is reduced, so that the electrical equipment is more energy-saving in the use process.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic block diagram of an embodiment of a stepless speed regulating circuit of an AC motor according to the present invention;

FIG. 2 is a schematic block diagram of another embodiment of a stepless speed regulating circuit of an AC motor according to the present invention;

FIG. 3 is a specific schematic diagram of a circuit of an embodiment of a stepless speed regulating circuit of an AC motor according to the utility model;

FIG. 4 is a schematic circuit diagram of a stepless speed regulating circuit of an AC motor according to another embodiment of the present invention;

FIG. 5 is a schematic circuit diagram of a stepless speed regulating circuit of an AC motor according to another embodiment of the present invention;

fig. 6 is a timing diagram of the commercial power, the power supply voltage, the zero point detection signal and the working voltage of the ac motor in the embodiment of the stepless speed regulating circuit of the ac motor of the present invention.

The reference numbers illustrate:

reference numerals	Name (R)	Reference numerals	Name (R)
				10	Master control circuit	20	H-bridge control circuit
30	Zero-crossing detection circuit	40	Current detection circuit
				50	Temperature detection circuit

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

The utility model provides a stepless speed regulating circuit of an alternating current motor.

Referring to fig. 1-3, in an embodiment of the present invention, the stepless speed regulating circuit of the ac motor includes a rotation speed adjusting input terminal, a main control circuit 10 and an H-bridge control circuit 20, the main control circuit 10 is connected to the rotation speed adjusting input terminal, and a controlled terminal of the H-bridge control circuit 20 is connected to the main control circuit 10.

The H-bridge control circuit 20 is configured to perform power conversion on the power supply voltage accessed by the power supply end according to the driving signal and output the power supply voltage to the alternating current motor, so that the alternating current motor rotates at a rotating speed corresponding to the rotating speed adjusting control signal.

In practical application, the alternating current motor inside electrical equipment such as an air purifier is often driven and controlled through the silicon controlled rectifier, the silicon controlled rectifier speed regulation is easy to generate errors, the energy consumption is high, and the silicon controlled rectifier is large in size and needs a large PCB area.

For this reason, in this embodiment, the electrical apparatus may be provided with a touch screen on a housing thereof, and a user may set different rotation speeds by touching corresponding functional areas of the touch screen, for example, the touch screen is provided with numbers 0 to 9 and ten determined functional areas, and the user may sequentially touch "1", "0", and "determined" functional areas to set a currently required rotation speed to be 1000 r/Min. The touch screen converts the touch signal into an electrical signal to output a rotation speed adjustment control signal to the main control circuit 10 through the rotation speed adjustment input terminal, where the rotation speed adjustment control signal may be a digital signal, such as "I ^2C signal, SPI signal, USART signal, and the like. Can also set up wireless communication circuit in electrical equipment, for example bluetooth circuit, WIFI circuit, 5G communication circuit etc. can be connected with outside remote controller or cell-phone APP communication, and wireless communication circuit passes through rotational speed regulation input and is connected with master control circuit 10 electricity simultaneously. The user can set up the rotational speed and export rotational speed signal to wireless communication circuit through outside remote controller or cell-phone APP according to the demand, and wireless communication circuit converts the rotational speed signal who receives into rotational speed regulation control signal again to export to master control circuit 10 through the rotational speed regulation input, with the rotational speed of the induced draft fan that the adjustment alternating current motor drove, thereby realize the self-service intelligent rotational speed of adjusting the induced draft fan of air purifier.

In this embodiment, the H-bridge control circuit 20 may be implemented by using four symmetrically arranged switching tubes, where the first switching tube and the third switching tube belong to the same bridge arm, the second switching tube and the fourth switching tube belong to the same bridge arm, that is, the first switching tube and the fourth switching tube are diagonally arranged, and the second switching tube and the third switching tube are diagonally arranged. For example, when the first switching tube is conducted with the fourth switching tube, the power supply voltage accessed by the power supply end flows from the first end to the second end of the alternating current motor, and when the second switching tube is conducted with the third switching tube, the power supply voltage accessed by the power supply end flows from the second end to the first end of the alternating current motor, so that the power supply voltage accessed by the power supply end is converted into the alternating current voltage flowing through the alternating current motor, and the alternating current motor can be driven to work.

In this embodiment, the main control circuit 10 may be provided with a digital signal unit for receiving the rotation speed adjustment control signal, so as to obtain the currently required rotation speed. And then adjusting the rotating speed of the alternating current motor according to a preset mapping table of driving signals, alternating current voltage amplitude and alternating current motor rotating speed, wherein the alternating conduction frequency of the two groups of diagonally arranged switching tubes is kept unchanged, namely the frequency of the formed alternating current voltage is unchanged. The amplitude of the alternating current voltage output to the alternating current motor by the H bridge is changed through the driving signal so as to change the rotating speed of the alternating current motor, for example, the driving signal is a PWM signal, the duty ratio of the PWM signal is changed to change the voltage value of the alternating current motor flowing through each group of diagonally arranged switching tubes when the switching tubes are switched on, and then the amplitude of the alternating current voltage output to the alternating current motor is finally changed, so that the rotating speed of the alternating current motor is changed. The larger the duty ratio of the driving signal is, the higher the amplitude of the alternating voltage is, and the faster the rotation speed of the alternating current motor is. For example, a "50% duty cycle, corresponding to an AC voltage amplitude of 200V, and a corresponding speed of 1000 r/Min. "

In another embodiment, the main control circuit 10 may further adjust the rotation speed of the ac motor according to a preset mapping table of driving signals, i.e., ac voltage frequency, ac motor rotation speed, and change the alternating conduction frequency of the two sets of diagonally arranged switching tubes to change the frequency of the ac voltage output to the ac motor under the condition that the switching frequency of the switching tube when each set of diagonally arranged switching tubes in the H-bridge control circuit 20 is turned on is kept unchanged, so as to change the rotation speed of the ac motor. Specifically, the driving signals may include a first driving signal and a second driving signal, and the main control circuit 10 drives the first switching tube and the fourth switching tube of the H-bridge control circuit 20 to be conducted by outputting the first driving signal, and drives the second switching tube and the third switching tube of the H-bridge control circuit 20 to be conducted by outputting the second driving signal. The main control circuit 10 can change the frequency of switching the output of the first driving signal and the second driving signal, for example, the main control circuit 10 outputs the first driving signal within 0 to 1 second, the main control circuit 10 outputs the second driving signal within 1 to 2 seconds and changes the frequency alternately into the frequency of the alternating current voltage output to the alternating current motor, which is the frequency at which the main control circuit 10 outputs the first driving signal within 0 to 0.5 seconds and the frequency at which the main control circuit 10 outputs the second driving signal within 0.5 to 1 second. The faster the main control circuit 10 alternately outputs the first drive signal and the second drive signal, the faster the frequency of the ac voltage output to the ac motor, and thus the faster the rotational speed of the ac motor. For example, "the alternating frequency of the first driving signal and the second driving signal is 20hZ, that is, the main control circuit 10 outputs the first driving signal and the second driving signal alternately every 0.05 seconds, the frequency of the corresponding ac voltage is 10hZ, and the corresponding rotation speed is 1000 r/Min. "wherein, the preset mapping table of driving signal-ac voltage amplitude-ac motor rotation speed and the preset mapping table of driving signal-ac voltage frequency-ac motor rotation speed may be obtained according to a plurality of experiments in advance and stored in the main control circuit 10.

Thus, in this embodiment, the main control circuit 10 can control the H-bridge control circuit 20 to drive the ac motor to adjust arbitrarily within the allowable range of the rotation speed according to the rotation speed adjustment control signal, so that this embodiment realizes stepless speed adjustment of the ac motor and improves the accuracy of speed adjustment of the ac motor.

In addition, because the H-bridge control circuit 20 is adopted, only half-bridge is turned on (the lower bridge arm is in a cut-off state when the upper bridge arm switch is turned on) in the same bridge arm every time, and the upper bridge arm and the lower bridge arm are prevented from being directly turned on, so that the heating power consumption of the alternating current motor in the stepless speed regulation process is reduced, and the electrical equipment is more energy-saving in the use process.

The stepless speed regulating circuit of the alternating current motor is provided with a rotating speed regulating input end for accessing a rotating speed regulating control signal, so that a main control circuit 10 generates a corresponding driving signal according to the rotating speed regulating control signal to drive an H-bridge control circuit 20 to carry out power conversion on power supply voltage accessed by a power supply end and output the power supply voltage to the alternating current motor, and the alternating current motor is driven to rotate at a rotating speed corresponding to the rotating speed regulating control signal. Therefore, stepless speed regulation of the alternating current motor is realized, and the accuracy of speed regulation is improved. Meanwhile, the heating power consumption of the alternating current motor in the stepless speed regulation process is reduced, so that the electrical equipment is more energy-saving in the use process.

Referring to fig. 3, the main control circuit 10 includes a main control chip and a driving chip, the main control chip is electrically connected to the input end of the rotation speed adjusting circuit and the input end of the driving chip, respectively, and the output end of the driving chip is connected to the controlled end of the H-bridge control circuit 20.

In this embodiment, the main control chip may adopt an MCU (micro controller unit), a DSP (Digital Signal processing) chip, an FPGA (Field Programmable Gate Array) chip, etc., the driving chip may adopt an ac motor driving chip, and the main control chip may control the driving chip to output a corresponding driving Signal according to the rotation speed adjustment control Signal to drive the H-bridge control circuit 20 to alternately conduct the diagonal switching tubes, so as to output the power supply voltage received by the power supply terminal to the ac motor after performing power supply transformation, so as to drive the ac motor to rotate at a rotation speed corresponding to the rotation speed adjustment control Signal.

In another embodiment, the main control chip and the driving chip are integrated on the same integrated chip, for example, a TW15501 integrated chip is adopted, and the integrated chip may include a core unit, a pulse modulation unit, a driving unit, an SIP detection unit, a dynamic sampling unit, an I/O interface unit, and the like. The core unit may include an arithmetic unit and a storage unit. Therefore, the integrated chip can adjust the control signal according to the rotating speed, after logical programming and PI operation are carried out through software, corresponding driving signals are directly output to drive the H-bridge control circuit 20 to work, two groups of diagonal switch tubes of the H-bridge control circuit 20 are conducted alternately, concretely, the driving signals can be PWM signals, the H-bridge control circuit 20 can be composed of a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, the first switch tube and the fourth switch tube are arranged in a diagonal mode, and the second switch tube and the third switch tube are arranged in a diagonal mode. The integrated chip drives the first switch tube and the fourth switch tube at opposite corners of the H-bridge control circuit 20 through the driving signal which is a PWM signal in a half period, and turns off the second switch tube and the third switch tube all the time. Then, in another half period of the same period, the integrated chip drives the second switching tube and the third switching tube which are opposite to each other to work through the driving signal which is the PWM signal, and the first switching tube and the fourth switching tube are always turned off. So that the power supply voltage accessed by the power supply end flows through the alternating current motor alternately from two directions, and the power supply voltage accessed by the power supply end is converted into alternating current voltage to be output to the alternating current motor so as to drive the alternating current motor to rotate at the rotating speed corresponding to the rotating speed adjusting control signal. The integrated chip can be used for storing a mapping table of the duty ratio of the preset driving signal, the amplitude of the alternating voltage and the rotating speed of the alternating current motor in the storage unit. Compared with the circuit structure of the main control chip and the driving chip in the embodiment, the integrated chip effectively improves the stability and accuracy of the driving signal through internal logic programming and PI operation, and the problem of reduction of speed regulation accuracy caused by unstable signal error, delay and transmission of the main control chip for controlling the driving chip in the embodiment can be solved. The accuracy of stepless speed regulation of the alternating current motor is effectively improved.

Through the arrangement, the stepless speed regulation of the alternating current motor can be realized, a driving chip is not required to be additionally arranged, and logic programming and PI operation are carried out through internal software to directly output a driving signal, so that the accuracy of speed regulation is improved. And the layout area of the whole stepless speed regulating circuit of the alternating current motor is reduced, the size of the circuit board is reduced, and the size of electrical equipment is further reduced.

Referring to fig. 4 and 6, in an embodiment, the stepless speed regulating circuit of the ac motor further includes a zero-cross detection circuit 30, an input end of the zero-cross detection circuit 30 is connected to the power supply terminal, and an output end of the zero-cross detection circuit is electrically connected to the main control circuit 10.

The zero-cross detection circuit 30 is configured to detect a voltage zero of a power supply voltage accessed by the power supply terminal, and output a zero-cross detection signal to the main control circuit 10 when the voltage zero is detected. The main control circuit 10 is configured to drive the H-bridge control circuit 20 according to the zero-point detection signal, so that a time of a voltage zero point of the ac voltage output by the H-bridge control circuit 20 coincides with a time of a voltage zero point of the power supply voltage.

In this embodiment, referring to fig. 4, fig. 6B and fig. 6C, the zero-cross detection circuit 30 may be formed by an optical coupler, an input end of the optical coupler is connected to a power supply voltage V1 that is connected to a power supply end, the power supply voltage V1 may be a dc pulse signal obtained by a commercial power after passing through a rectification circuit, according to a working characteristic of the optical coupler, in a voltage zero-point time interval of the power supply voltage that is connected to the power supply end, a voltage value of the power supply voltage V1 cannot drive the optical coupler to work, the optical coupler outputs a zero-point detection signal to the main control circuit 10, and the main control circuit 10 drives the H-bridge control circuit 20 to perform a commutation work when receiving the zero-point detection signal, so that an ac voltage output to the ac motor, that is, a zero-point time of the working voltage of the ac motor is kept consistent with a zero-point time of the power supply voltage V1. The zero-crossing detection circuit 30 may also be composed of a switch tube, a controlled end of the switch tube is electrically connected to the power voltage V1, and in a voltage zero point time interval of the power voltage accessed by the power end, the voltage value of the power voltage V1 cannot drive the switch tube to work, so that the switch tube outputs a zero point detection signal to the main control circuit 10 to repeat the above process.

Through the arrangement, the time of the voltage zero point of the power supply voltage accessed by the power supply end can be consistent with the time of the voltage zero point of the alternating-current voltage output to the alternating-current motor, so that the main control circuit 10 can more accurately control the alternating-current voltage output to the alternating-current motor by the H-bridge control circuit 20, the accuracy of the rotating speed of the alternating-current motor is improved, the condition that the rotating speed deviation of the alternating-current motor is caused by the fact that the time of the voltage zero point of the alternating-current voltage output to the alternating-current motor is staggered with the time of the voltage zero point of the power supply voltage is avoided, and the stability and the accuracy of the rotating speed of the alternating-current motor are improved.

Specifically, referring to fig. 3, 4 and 6, a main control chip and a driving chip are integrated on the same integrated chip, and a power supply voltage V1 of a power supply access is taken as a dc pulse obtained after a commercial power V0 passes through a rectifying circuit. The integrated chip U1 is provided with a rotating speed adjusting input pin CFI, a left bridge control first pin L-VB, a left bridge control second pin L-HO, a left bridge control third pin L-VS, a left bridge control fourth pin L-LO, a right bridge control first pin R-VB, a right bridge control second pin R-HO, a right bridge control third pin R-VS, a right bridge control fourth pin R-LO and a zero point detection pin Z-INT. The H-bridge control circuit 20 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The input ends of a first switch tube Q1 and a second switch tube Q2 are connected with a power supply voltage, the controlled end of a first switch tube Q1 is connected with a left bridge control second pin L-HO through a second resistor R2, the controlled end of the first switch tube Q1 is respectively connected with the first end of an alternating current motor AC, the input end of a third switch tube Q3, a left bridge control third pin L-VS and a left bridge control first pin L-VB through the first resistor R1, the controlled end of a second switch tube Q2 is connected with a right bridge control second pin R-HO through a sixth resistor R6, the controlled end of the second switch tube Q5 is respectively connected with the second end of the alternating current motor AC, the input end of a fourth switch tube Q3, the right bridge control third pin R-VS and the right bridge control first pin R-VB, the output ends of the third switch tube Q3 and the fourth switch tube Q4 are both grounded, the controlled end of the third switch tube Q3 is connected with the left bridge control second pin L-HO through a fourth resistor R4, the controlled end of the fourth switching tube Q4 is connected with the fourth leg R-LO of the right bridge control through an eighth resistor R8, and is also grounded through a seventh resistor R7. The zero-crossing detection circuit 30 comprises an optical coupler U2, a ninth resistor R9 and a tenth resistor R10, a first pin of the optical coupler U2 is connected with a second end of the ninth resistor R9, a first end of the ninth resistor R9 is connected with a power voltage V1, a second pin and a third pin of the optical coupler U2 are both grounded, and a fourth pin of the optical coupler U2 and a second pin of the tenth resistor R10 are respectively connected with a zero-point detection pin Z-INT of the integrated chip U1.

In the time interval of the voltage zero point of the power voltage V1, the voltage value of the power voltage V1 cannot drive the optocoupler to act, so that the zero point detection pin Z-INT of the integrated chip U1 is pulled up to the second voltage V2 by the tenth resistor R10, and when the voltage value of the power voltage V1 can drive the optocoupler to act, the zero point detection pin Z-INT of the integrated chip U1 is pulled down by the optocoupler to be grounded and receives a low-level signal. Then it is exactly the time of the voltage zero of the supply voltage V1 when the integrated chip U1 receives a high level signal through the zero point detection pin Z-INT.

After the integrated chip U1 receives the rotation speed adjustment control signal through the rotation speed adjustment input pin CFI, when the zero point detection pin Z-INT receives the next high level, that is, the voltage zero point time of the power supply voltage V1 (refer to the time t0 in fig. 6), the first pin L-VB, the second pin L-HO, the third pin L-VS, the fourth pin L-LO, the first pin R-VB, the second pin R-HO, the third pin R-VS, and the fourth pin R-LO are controlled by the left bridge, the first switching tube Q1 and the fourth switching tube Q4 are conducted by the left bridge, the power supply voltage V1 flows from the AC first end to the second end through the first switching tube Q1, and then the fourth switching tube Q4 is grounded, when the zero point detection pin Z-INT receives the next high level, that is, at the second voltage zero point of the power voltage V1 (refer to time t1 in fig. 6), the integrated chip U1 turns off the first switching tube Q1 and the fourth switching tube Q4, turns on the second switching tube Q2 and the third switching tube Q3, and allows the power voltage V1 to flow from the second end to the first end of the ac motor through the second switching tube Q2, and then to be grounded through the third switching tube Q3. And then, repeatedly switching and conducting two groups of diagonal switching tubes at the subsequent voltage zero point moment of the power supply voltage so as to enable the working voltage output to the alternating current motor to be the working voltage. Meanwhile, the integrated chip U1 may change the switching frequency of each group of switching tubes when each group of switching tubes is turned on according to a preset mapping table of ac voltage value-ac motor rotation speed, for example, "100V corresponds to 1000 rpm, 120V corresponds to 1200 rpm", so as to change the ac voltage value finally output to the ac motor, for example, the driving signal is a PWM signal, which may change the duty ratio of the PWM signal, thereby changing the switching frequency of each group of switching tubes, and further changing the ac voltage value finally output to the ac motor, thereby implementing stepless speed regulation of the ac motor.

In another embodiment, the stepless speed regulating circuit of the ac motor may further include a power management circuit, and the power management circuit may be implemented by using an LDO (low dropout regulator), and step down the power voltage V1 to a second voltage V2 adapted to the operation of the integrated chip U2, so as to provide an operating voltage for the integrated chip U2. Through the arrangement, the whole circuit can meet the working voltage requirements of different electronic components, and the compatibility and expandability of the whole circuit are improved.

It should be noted that, in the control process of the existing ac motor, the detection of over-temperature and over-current is lacked, and the requirements of high-end users cannot be met.

In order to solve the above problem, referring to fig. 5, in an embodiment, the stepless speed regulating circuit of the ac motor further includes a temperature detecting circuit 50, and an output end of the temperature detecting circuit 50 is electrically connected to the main control circuit 10.

The temperature detection circuit 50 is configured to detect a temperature of the H-bridge control circuit 20 and output a temperature detection signal to the main control circuit 10. The main control circuit 10 is configured to stop driving the H-bridge control circuit 20 to stop the ac motor from rotating when it is determined that the temperature of the H-bridge control circuit 20 is higher than the preset alarm temperature according to the temperature detection signal.

In this embodiment, the temperature detection circuit 50 may be implemented by an infrared temperature sensor, which detects infrared radiation of the H-bridge control circuit 20 during operation, determines the current temperature of the H-bridge control circuit 20 according to the intensity of the infrared radiation, and converts the heat signal into an electrical signal to output to the main control circuit 10. Or, the NTC thermistor is used, the NTC thermal resistor is connected in series with the power source end and the fixed resistance resistor to form the temperature detection circuit 50 due to the change of the resistance of the NTC thermal resistor corresponding to the temperature change of the H-bridge control circuit 20, the resistance of the NTC thermistor also changes along with the change of the temperature of the H-bridge control circuit 20, the voltage on the fixed resistance resistor also changes along with the change of the resistance, and the main control circuit 10 can obtain the corresponding current temperature of the H-bridge control circuit 20 by detecting the voltage on the fixed resistance resistor.

Specifically, referring to fig. 5, taking the example that the device and the temperature detection circuit 50 in the above description are NTC thermistors, the integrated chip U1 further has a temperature detection input pin TEMP-DET and a power pin VCC, the power pin VCC is connected to the second voltage V2, the temperature detection circuit 50 includes thermistors NTC1 and a sixteenth resistor R16, a first end of the thermistor NTC1 is connected to the second voltage V2, a second end of the thermistor NTC1 and a first end of the sixteenth resistor R16 are respectively connected to the temperature detection input pin TEMP-DET, and a second end of the sixteenth resistor R16 is grounded. The NTC thermistor can be tightly attached to the MOS tubes in the H bridge of the H bridge control circuit 20, and in the working process of the H bridge control circuit 20, 4 MOS tubes in the H bridge are conducted in turn to generate certain heat. The integrated chip U1 may obtain the voltage value of the thermistor NTC1 according to the voltage value of the received temperature detection signal, that is, the voltage value of the sixteenth resistor, so as to calculate the current resistance value of the thermistor, and then obtain the current operating temperature of the H-bridge control circuit 20 according to the preset thermistor resistance value-temperature mapping table, for example, "at 50 ℃, the resistance value of the thermistor NTC1 is 5K", so as to determine whether the temperature of the H-bridge control circuit 20 is greater than the preset alarm temperature, and if the temperature is greater than the preset alarm temperature, immediately stop driving the H-bridge control circuit 20, so as to stop the ac motor from operating.

Through the arrangement, the automatic detection device can automatically detect the working temperature of the H-bridge control circuit 20, and timely stops the work of the H-bridge control circuit 20 and the alternating current motor when the temperature is too high, so that the damage to devices and the alternating current motor caused by the too high temperature is prevented, the use safety of a user is guaranteed, and the safety of the whole circuit is further improved. In addition, the NTC thermistor is adopted to form the temperature detection circuit 50, the circuit structure is simple, the layout area on the circuit board is small, the overall layout area of the stepless speed regulation circuit of the alternating current motor is favorably reduced, the miniaturization of the stepless speed regulation module of the alternating current motor is favorably promoted, and the integration of electrical equipment is improved.

Referring to fig. 5, in an embodiment, the stepless speed regulating circuit of the ac motor further includes a current detection circuit 40, a detection end of the current detection circuit 40 is electrically connected to the ac power supply, and an output end of the current detection circuit 40 is electrically connected to the main control circuit 10.

The current detection circuit 40 is configured to detect a working current flowing through the ac motor and output a current detection signal to the main control circuit 10, and the main control circuit 10 is configured to stop driving the H-bridge control circuit 20 according to the current detection signal when it is determined that the working current of the ac motor is greater than a preset alarm current, so as to stop the ac motor from rotating. The preset alarm current can be obtained and stored according to multiple experiments.

In this embodiment, the current detection circuit 40 may be implemented by using a current detection resistor, the current detection resistor is connected in series with the ac motor, the current detection resistor may use a differential resistor with a small resistance value, for example, 5m Ω, the voltage across the differential resistor may be obtained by detecting the voltage across the differential resistor, and then the current flowing through the differential resistor is calculated, so as to obtain the working current flowing through the ac motor, and when the detected working current is too large, the main control circuit 10 stops driving the H-bridge control circuit 20 to stop the rotation of the ac motor, so as to prevent the fault caused by the too large working current. A current transformer can also be used to form the current detection circuit 40, and after the alternating current is directly sampled, a current detection signal is output to the control main control circuit 10.

The current detection circuit 40 can also be formed by a current detection resistor and an operational amplifier, the operational amplifier detects the voltage difference value at two ends of the current detection resistor, namely the voltage value on the current detection resistor, and outputs the amplified signal to the main control circuit 10 as a current detection signal, the main control circuit 10 can calculate the voltage on the current detection resistor according to the model selection parameter of the operational amplifier and the current detection signal to calculate the working current of the alternating current motor, and when the detected working current is too large, the main control circuit 10 stops driving the H-bridge control circuit 20 to stop the alternating current motor from rotating, so as to prevent the fault caused by the too large working current.

Specifically, referring to fig. 5, the device and current detection circuit 40 in the above description are exemplified by using a current detection resistor and an operational amplifier, the integrated chip U1 further has a current detection pin C-SEN, the current detection circuit 40 includes a current detection resistor R11, an operational amplifier U2A, a twelfth resistor R12, a thirteenth resistor R13, a second end of a second pin, a fourth pin, and a twelfth resistor R12 of the operational amplifier U2A, the second ends of the eleventh resistor R11 are all grounded, the third pin of the operational amplifier U2A, the first end of the eleventh resistor R11, and the source end of the third switching tube Q3 are respectively connected to the source end of the fourth switching tube Q4, the eighth pin of the operational amplifier U2A is connected to the second voltage V2, the first pin of the operational amplifier U2A and the first end of the twelfth resistor R12 are respectively connected to the second end of the thirteenth resistor R13, and the first end of the thirteenth resistor R13 is connected to the current detection pin C-SEN of the integrated chip U1. As described above, the operational amplifier U2A detects the voltage across the eleventh resistor R11, amplifies the voltage across the eleventh resistor R11 according to the type of the selected parameter, and outputs the current detection resistor to the integrated chip U1, the integrated chip U1 calculates the current value across the current detection resistor R11 according to the preset and stored mapping table of the current-current detection signal voltage value of the operational amplifier U2A, so as to obtain the operating current of the ac motor, and when the operating current is greater than the preset alarm current, the H-bridge control circuit 20 is stopped to be driven to stop the ac motor from rotating.

Through the arrangement, the working current of the alternating current motor can be detected in real time, and when the working current is larger than the preset alarm current, the alternating current motor is stopped to rotate in time, so that overheating damage caused by the over-rotating speed of the alternating current motor in an over-current state is prevented, and damage of other devices caused by the over-large working current is prevented. The utility model improves the safety of the stepless speed regulation control process of the alternating current motor.

In another embodiment, the current detection circuit 40 is further configured to detect an operating current flowing through the ac motor, and output an overcurrent shutdown signal to the main control circuit 10 when determining that the operating current of the ac motor is greater than a preset alarm current. The main control circuit 10 is used for stopping driving the H-bridge control circuit 20 to stop the rotation of the alternating current motor when receiving an overcurrent shutdown signal, and the utility model can adopt an operational amplifier as a comparator to directly compare the current working current with the preset alarm current through hardware and directly output the result to the main control circuit 10, thereby avoiding the need of the main control circuit 10 to calculate and judge whether the current working current exceeds the preset alarm current value, and effectively preventing the situation that the main control circuit 10 cannot stop the alternating current motor when the working current is too large due to calculation deviation.

To illustrate the device and current detection circuit 40 in the above description using a current detection resistor and an operational amplifier, the operational amplifier may be a dual operational amplifier such as LM358AD, which is composed of an operational amplifier U2A and a second operational amplifier U2B. The current detection circuit 40 further includes a dual operational amplifier composed of an operational amplifier U2A and a second operational amplifier U2B, a fifteenth resistor R15 and a fourteenth resistor R14, the integrated chip U1 has an OVER-current detection pin C-OVER, a seventh pin of the second operational amplifier U2B is connected to the OVER-current detection pin C-OVER of the integrated chip U1, a fifth pin of the second operational amplifier U2B and a second end of the fifteenth resistor R15 are respectively connected to a first end of the fourteenth resistor R14, a second end of the fourteenth resistor R14 is connected to the second voltage V2, and a first end of the fifteenth resistor R15 is grounded.

The fourteenth resistor R14 and the fifteenth resistor R15 may divide the second voltage V2 according to a certain resistance ratio and output the divided voltage to the fifth pin of the second operational amplifier U2B, so as to serve as the reference voltage of the second operational amplifier U2B. The second operational amplifier U2B compares the current detection signal voltage with the reference voltage, and if the current detection signal voltage value is greater than the reference voltage value, it indicates that the current working current of the ac motor is excessive. The second operational amplifier U2B directly outputs a high level signal or a low level signal as an overcurrent shutdown signal to the integrated chip U1, and the integrated chip U1 directly stops the current ac motor when receiving the overcurrent shutdown signal.

As can be seen from the above, the integrated chip U1 stores a mapping table of current value-voltage value corresponding to the current detection signal, and it can be understood that the preset alarm current may also find the corresponding preset alarm voltage value in the mapping table, that is, when the voltage value of the current detection signal reaches the preset alarm voltage value, it represents that the working current value reaches the preset alarm current value.

In this embodiment, the reference voltage value set by adjusting the resistance ratio may be equal to the preset alarm voltage value, so that when the main control circuit 10 calculates a deviation of the working current due to a fault, the ac motor can be stopped in time under the condition that the working current is overcurrent. In another embodiment, if a plurality of ac motors are driven to operate simultaneously, the resistance ratio may be adjusted appropriately to make the reference voltage value smaller than the preset alarm voltage value, so as to prevent the main control circuit 10 from failing to stop the operation of the plurality of ac motors due to the calculation delay caused by the simultaneous increase of the operating currents of the plurality of ac motors when the operating components are failed.

Through the arrangement, the working current of the alternating current motor can be detected through hardware, and the overcurrent stop signal is directly fed back to the main control circuit 10 when overcurrent occurs, so that the main control circuit 10 is not required to calculate and determine whether the current working current exceeds the preset alarm current value, and the condition that the alternating current motor cannot be stopped when the working current is too large due to calculation deviation of the main control circuit 10 is effectively prevented. The utility model realizes the double protection of the work current overcurrent of the alternating current motor, and further improves the safety of the stepless speed regulation control process of the alternating current motor.

Referring to fig. 5, in an embodiment of the present invention, the stepless speed regulating circuit of the ac motor further includes an indicating circuit, and an input end of the indicating circuit is electrically connected to the main control circuit 10.

The main control circuit 10 is configured to adjust the control signal according to the rotation speed, and control the indicating circuit to indicate the rotation speed of the ac motor corresponding to the rotation speed adjustment control signal.

In this embodiment, the indicating circuit may be implemented by a nixie tube, and as described in the above-mentioned devices and the nixie tube as examples, the input end IND of the nixie tube is connected to the indicating control pin INS of the integrated chip U1, and the integrated chip U1 may control the nixie tube to display the current ac motor speed, for example, "1500", according to the speed adjusting control signal. The indicating circuit may also adopt a display, and the main control circuit 10 may control the display to display the current ac motor rotation speed according to the rotation speed adjusting control signal, for example, "rotation speed: 1500 rpm ".

Through the setting, the user can visually see the current working rotating speed, and the use convenience is improved.

In another embodiment, the indicating circuit may be additionally provided with an alarm, such as a buzzer, an LED lamp, etc., for controlling the alarm to give an alarm to prompt a user that a fault occurs currently when the temperature of the H-bridge control circuit 20 is too high and the working current of the ac motor is too large, so as to further improve the convenience of use.

The utility model also provides an alternating current motor stepless speed regulation module which comprises a circuit board and the alternating current motor stepless speed regulation circuit. The stepless speed regulating circuit of the alternating current motor is arranged on the circuit board.

Because the stepless speed regulation module of the alternating current motor is based on the stepless speed regulation circuit of the alternating current motor, the embodiment of the stepless speed regulation module of the alternating current motor comprises all technical schemes of all embodiments of the stepless speed regulation circuit of the alternating current motor, the achieved technical effects are completely the same, and the details are not repeated.

The utility model also provides electrical equipment which comprises the alternating current motor, a shell and the stepless speed regulation module of the alternating current motor. The alternating current motor stepless speed regulation module is accommodated in the shell and electrically connected with the alternating current motor so as to drive the alternating current motor to work.

Because the electrical equipment is based on the alternating current motor stepless speed regulation module and the alternating current motor stepless speed regulation circuit, the embodiment of the electrical equipment comprises all technical schemes of all embodiments of the alternating current motor stepless speed regulation module and the alternating current motor stepless speed regulation circuit, the achieved technical effects are completely the same, and the description is omitted.

The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the technical solutions of the present invention, which are made by using the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (7)

1. An alternating current motor stepless speed regulation circuit is characterized by comprising:

the rotating speed adjusting input end is used for accessing a rotating speed adjusting control signal;

the main control circuit is electrically connected with the rotating speed adjusting input end and is used for generating a corresponding driving signal according to the rotating speed adjusting control signal;

the H-bridge control circuit is used for performing power conversion on power supply voltage accessed by a power supply end according to the driving signal and outputting the power supply voltage to the alternating current motor so as to enable the alternating current motor to rotate at a rotating speed corresponding to the rotating speed adjusting control signal;

the main control circuit comprises a main control chip and a driving chip, the main control chip is respectively electrically connected with the rotating speed adjusting input end and the input end of the driving chip, and the output end of the driving chip is connected with the controlled end of the H-bridge control circuit;

the main control chip and the driving chip are integrated in the same integrated chip;

the stepless speed regulating circuit of the alternating current motor further comprises a zero-crossing detection circuit, wherein the input end of the zero-crossing detection circuit is connected with the power supply end, and the output end of the zero-crossing detection circuit is electrically connected with the main control circuit;

the zero-crossing detection circuit is used for detecting the voltage zero point of the power supply voltage accessed by the power supply end and outputting a zero-point detection signal to the main control circuit when the voltage zero point is detected;

and the main control circuit is used for driving the H-bridge control circuit to work according to the zero detection signal so as to enable the time of the voltage zero of the alternating current voltage output by the H-bridge control circuit to be consistent with the time of the voltage zero of the power supply voltage.

2. The ac motor stepless speed regulation circuit according to claim 1, further comprising a temperature detection circuit, an output end of the temperature detection circuit being electrically connected to the main control circuit, the temperature detection circuit being configured to detect the temperature of the H-bridge control circuit and output a temperature detection signal to the main control circuit;

and the main control circuit is used for stopping driving the H-bridge control circuit to work when the temperature of the H-bridge control circuit reaches a preset alarm temperature according to the temperature detection signal.

3. The ac motor stepless speed regulation circuit according to claim 1, characterized in that the ac motor stepless speed regulation circuit further comprises a current detection circuit, a detection end of the current detection circuit is electrically connected with the ac motor, and an output end of the current detection circuit is electrically connected with the main control circuit; the current detection circuit is used for detecting the working current flowing through the alternating current motor and outputting a current detection signal to the main control circuit;

and the main control circuit is used for controlling the H-bridge control circuit to stop driving the alternating current motor to rotate when the working current of the alternating current motor is determined to be larger than the preset alarm current according to the current detection signal.

4. The stepless speed regulating circuit of the alternating current motor as claimed in claim 3, wherein the current detection circuit is further configured to detect a working current flowing through the alternating current motor, and output an overcurrent protection signal to the main control circuit when it is determined that the working current of the alternating current motor is greater than the preset alarm current;

and the main control circuit is used for controlling the H-bridge control circuit to stop driving the alternating current motor to rotate when receiving the overcurrent protection signal.

5. The ac motor stepless speed regulation circuit according to claim 1, characterized in that the ac motor stepless speed regulation circuit further comprises an indication circuit, an input end of the indication circuit is electrically connected with the main control circuit; and the main control circuit is used for controlling the indicating circuit to indicate the rotating speed of the alternating current motor corresponding to the rotating speed adjusting control signal according to the rotating speed adjusting control signal.

6. A stepless speed regulation module of an AC motor is characterized by comprising a circuit board and the stepless speed regulation circuit of the AC motor as claimed in any one of the claims 1 to 5; wherein the content of the first and second substances,

the alternating current motor stepless speed regulating circuit is arranged on the circuit board.

7. An electrical apparatus, comprising an ac motor, a housing, and the ac motor stepless speed regulation module of claim 6; wherein the content of the first and second substances,

the alternating current motor stepless speed regulation module is accommodated in the shell and electrically connected with the alternating current motor so as to drive the alternating current motor to work.

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