Accurate sampling circuit of direct-current brush motor of clothes airing machine

Abstract

The utility model discloses an accurate sampling circuit of a direct current brush motor of a clothes airing machine, output current of the direct current brush motor is processed by a voltage signal pickup module, an emitter following module, an automatic gain amplification module, a two-stage four-order low-pass filtering module and an ADC conversion module in sequence to form accurate sampling current, and the accurate sampling current is input into an MCU controller; the voltage signal pickup module comprises a sixth resistor serving as a voltage sampling resistor, an anti-aliasing filtering module and a differential equal-proportion operation module; the anti-aliasing filtering module comprises a first filtering branch and a second filtering branch; the differential equal-proportion operation module comprises a third operational amplifier, a third resistor, a first resistor and an eighth resistor; accurate current sampling of the direct-current brush motor of the clothes airing machine is realized through a hardware circuit, so that the MCU controller can obtain a current sampling value with low error, high smoothness and less harmonic quantity, and further the operation of the direct-current brush motor is controlled more accurately without delay.

Description

Technical Field

[0001] The utility model relates to an electric clothes dryer, in particular to an accurate sampling circuit for a DC brushed motor of a clothes dryer. The circuit accurately samples the output current of the DC brushed motor of the clothes dryer and inputs it to an MCU controller to detect motor overload and current when encountering resistance, and timely trigger a protection module. Background Technique

[0002] At present, most of the core power components of electric clothes dryers on the market adopt DC brushed motors. The change value of the current of a DC brushed motor can reflect the situation of driving a clothes drying rod assembly to move. Therefore, the MCU controller detects the output current of the DC brushed motor to judge whether there is motor overload or current when encountering resistance, and triggers the protection module to stop or reverse the rotation of the motor, so as to protect the motor and the clothes drying rod assembly.

[0003] However, due to the inherent characteristics of the DC brushed motor, the brushes and commutator segments of the motor are constantly commutating at high speed, resulting in an uneven current waveform, large fluctuations, and many harmonics, so that it is difficult for the MCU controller to detect the accurate motor output current value, and further resulting in insufficient control accuracy of the motor.

[0004] In view of the above problems, there are mainly two existing solutions:

[0005] The first one is to convert the output current signal of the motor into a voltage signal through a current sampling resistor, and then directly use the MCU controller for software filtering processing, as Figure 1 shown. Although this solution improves the smoothness of the current value detected by the MCU controller to a certain extent, there is a large error between the detected motor current value and the actual current value. In addition, restricted by the software operation speed of the MCU controller itself, there is a delay between the software filtering of the MCU controller and the triggering of the protection action, reducing the response timeliness of the entire detection and protection system.

[0006] The second method is to improve the accuracy of the sampled current by adding a sampling circuit and using a hardware circuit. For example, the published patent application No. CN118091241A provides a current sampling circuit, system, method, and drying machine, which relates to the technical field of circuit design. The current sampling circuit includes: a driving circuit, a filtering circuit, and a controller; the driving circuit includes a sampling resistor and is configured to drive the motor and control its speed; the first end of the sampling resistor is connected to the first voltage terminal, and the second end of the sampling resistor is used to be electrically connected to the motor; the filtering circuit has its first end electrically connected to the first end of the sampling resistor and its second end electrically connected to the second end of the sampling resistor, and is configured to filter the initial voltage corresponding to the second end of the sampling resistor to obtain a sampling voltage; the frequency of the sampling voltage is within a predetermined frequency range; the controller has its first end electrically connected to the third end of the filtering circuit and is configured to obtain the sampling voltage and convert it into a sampling current. Although this solution improves the accuracy of the sampling current by enhancing its anti-interference ability, it is difficult to completely eliminate the problem of uneven current caused by the inherent characteristics of the DC brushed motor, and the circuit is very complex, increasing the manufacturing cost of the electric drying machine, which will ultimately be reflected in the price decision of the drying machine. Utility Model Content

[0007] Regarding the detection circuit of the DC brushed motor of the existing electric drying machine, there are problems such as uneven current waveform, large fluctuations, and many harmonics, resulting in inaccurate current detected by the MCU controller. Moreover, the existing software solutions are difficult to eliminate errors, and there is a delay in software processing. The hardware solutions have complex circuits and are difficult to eliminate the problem of inaccurate current caused by the inherent characteristics of the DC brushed motor. The technical problem to be solved by this utility model is to provide an accurate sampling circuit for the DC brushed motor of the drying machine, which can achieve efficient and accurate sampling of the motor output current through a hardware circuit, so that the MCU controller can directly detect the accurate motor output current.

[0008] The technical solution adopted by this utility model to solve the above technical problems is: an accurate sampling circuit for the DC brushed motor of the drying machine, including a DC brushed motor, a voltage signal pickup module, an emitter follower module, an automatic gain amplification module, a second-order four-stage low-pass filtering module, an ADC conversion module, and an MCU controller, which are electrically connected in sequence;

[0009] The output current of the DC brushed motor is processed by the voltage signal pickup module, emitter follower module, automatic gain amplification module, second-order four-stage low-pass filtering module, and ADC conversion module in sequence to form an accurate sampling current and input it into the MCU controller. The MCU controller controls the operation of the DC brushed motor in a feedback manner according to the change of the accurate sampling current.

[0010] The voltage signal pickup module includes a sixth resistor serving as a voltage sampling resistor, an anti-aliasing filtering module, and a differential proportional operation module; one end of the sixth resistor is connected to the current output end of the DC brushed motor, and the other end is grounded;

[0011] The anti-aliasing filtering module includes a first filtering branch formed by series connection of a second resistor and a first capacitor, and a second filtering branch formed by series connection of a seventh resistor and a fourth capacitor; the resistor end of the first filtering branch is connected to the node between the sixth resistor and the current output end of the DC brushed motor, and the capacitor end of the first filtering branch is grounded; the resistor end of the second filtering branch is connected to the node between the sixth resistor and the ground end, and the capacitor end of the second filtering branch is grounded;

[0012] The differential proportional operation module includes a third operational amplifier, a third resistor, a first resistor, and an eighth resistor; the third resistor is connected between the middle node of the first filtering branch and the inverting input end of the third operational amplifier, the eighth resistor is connected between the middle node of the second filtering branch and the non-inverting input end of the third operational amplifier, and the first resistor is connected between the inverting input end and the output end of the third operational amplifier.

[0013] The preferred technical solution adopted by the present utility model to solve the above technical problems is that the resistance values of the second resistor, the seventh resistor, the third resistor, and the eighth resistor are equal; the resistance value of the first resistor is twice the resistance value of the third resistor.

[0014] The preferred technical solution adopted by the present utility model to solve the above technical problems is that the emitter follower module includes a second operational amplifier, the non-inverting input end of the second operational amplifier is connected to the output end of the third operational amplifier, and the inverting input end of the second operational amplifier is short-circuited to its output end; the output end of the second operational amplifier is connected to the input end of the automatic gain amplification module.

[0015] The preferred technical solution adopted by the present utility model to solve the above technical problems is that the automatic gain amplification module includes an automatic gain amplifier; the MCU controller inputs five high and low level digital signals to the automatic gain amplifier, and the MCU controller obtains at least four gain multiples by automatically adjusting the level of the five high and low level digital signals.

[0016] The preferred technical solution adopted by the present utility model to solve the above technical problems is that the second-order fourth-order low-pass filtering module includes a first-stage low-pass filtering module and a second-stage low-pass filtering module connected in series;

[0017] The first - stage low - pass filtering module includes a third filtering branch, a fourth filtering branch, and a first operational amplifier; the third filtering branch is formed by connecting a fourth resistor and a second capacitor in series, and the fourth filtering branch is formed by connecting a fifth resistor and a third capacitor in series; the resistor end of the third filtering branch is connected to the output end of the automatic gain amplification module, and the capacitor end of the third filtering branch is grounded; the resistor end of the fourth filtering branch is connected to the middle node of the third filtering branch, and the capacitor end of the fourth filtering branch is grounded; the non - inverting input terminal of the first operational amplifier is connected to the middle node of the fourth filtering branch, and the inverting input terminal of the first operational amplifier is short - circuited to its output terminal;

[0018] The second - stage low - pass filtering module includes a fifth filtering branch, a sixth filtering branch, and a fourth operational amplifier; the fifth filtering branch is formed by connecting a tenth resistor and a sixth capacitor in series, and the sixth filtering branch is formed by connecting a ninth resistor and a fifth capacitor in series; the resistor end of the fifth filtering branch is connected to the output end of the first operational amplifier, and the capacitor end of the fifth filtering branch is grounded; the resistor end of the sixth filtering branch is connected to the middle node of the fifth filtering branch, and the capacitor end of the sixth filtering branch is grounded; the non - inverting input terminal of the fourth operational amplifier is connected to the middle node of the sixth filtering branch, and the inverting input terminal of the fourth operational amplifier is short - circuited to its output terminal;

[0019] The output end of the fourth operational amplifier is connected to the input end of the ADC conversion module.

[0020] The preferred technical solution adopted by the present utility model to solve the above - mentioned technical problems is that: the input end of the ADC conversion module is connected to the output end of the second - order four - stage low - pass filtering module, and the output end of the ADC conversion module outputs the accurate sampling current and inputs it into the MCU controller.

[0021] Another technical solution adopted by the present utility model to solve the above - mentioned technical problems is that: an accurate sampling circuit for a DC brushed motor of a clothes dryer, which includes a DC brushed motor, a voltage signal pickup module, an emitter follower module, an automatic gain amplification module, a second - order four - stage low - pass filtering module, an ADC conversion module, and an MCU controller that are electrically connected in sequence;

[0022] The output current of the DC brushed motor is processed successively by the voltage signal pickup module, the emitter follower module, the automatic gain amplification module, the second - order four - stage low - pass filtering module, and the ADC conversion module to form an accurate sampling current signal and input it into the MCU controller. The MCU controller controls the operation of the DC brushed motor in a reverse - control manner according to the change of the accurate sampling current;

[0023] The voltage signal pickup module includes a sixth resistor serving as a voltage sampling resistor, an anti-aliasing filtering module, and a differential proportional operation module; one end of the sixth resistor is connected to the current output end of the DC brushed motor, and the other end is grounded;

[0024] The anti-aliasing filtering module includes a first filtering branch formed by series connection of a second resistor and a first capacitor, and a second filtering branch formed by series connection of a seventh resistor and a fourth capacitor; the resistor end of the first filtering branch is connected to the node between the sixth resistor and the current output end of the DC brushed motor, and the capacitor end of the first filtering branch is grounded; the resistor end of the second filtering branch is connected to the node between the sixth resistor and the ground end, and the capacitor end of the second filtering branch is grounded;

[0025] The differential proportional operation module includes a third operational amplifier, a third resistor, a first resistor, and an eighth resistor; the third resistor is connected between the middle node of the first filtering branch and the inverting input end of the third operational amplifier, the eighth resistor is connected between the middle node of the second filtering branch and the non-inverting input end of the third operational amplifier, and the first resistor is connected between the inverting input end and the output end of the third operational amplifier;

[0026] The automatic gain amplification module includes an automatic gain amplifier; the MCU controller inputs five high and low level digital signals to the automatic gain amplifier, and the MCU controller obtains at least four gain multiples by automatically adjusting the level of the five high and low level digital signals.

[0027] A preferred embodiment of another technical solution adopted by the present invention to solve the above technical problems is: the emitter follower module includes a second operational amplifier, the non-inverting input end of the second operational amplifier is connected to the output end of the third operational amplifier, and the inverting input end of the second operational amplifier is short-circuited to its output end; the output end of the second operational amplifier is connected to the input end of the automatic gain amplification module;

[0028] The resistances of the second resistor, the seventh resistor, the third resistor, and the eighth resistor are equal; the resistance of the first resistor is twice the resistance of the third resistor;

[0029] The input end of the ADC conversion module is connected to the output end of the second-order fourth-order low-pass filtering module, and the output end of the ADC conversion module outputs the accurate sampled current and inputs it to the MCU controller.

[0030] A preferred embodiment of another technical solution adopted by the present invention to solve the above technical problems is: the second-order fourth-order low-pass filtering module includes a first-stage low-pass filtering module and a second-stage low-pass filtering module connected in series;

[0031] The first - stage low - pass filtering module includes a third filtering branch, a fourth filtering branch, and a first operational amplifier; the third filtering branch is formed by connecting a fourth resistor and a second capacitor in series, and the fourth filtering branch is formed by connecting a fifth resistor and a third capacitor in series; the resistor end of the third filtering branch is connected to the output end of the automatic gain amplification module, and the capacitor end of the third filtering branch is grounded; the resistor end of the fourth filtering branch is connected to the middle node of the third filtering branch, and the capacitor end of the fourth filtering branch is grounded; the non - inverting input terminal of the first operational amplifier is connected to the middle node of the fourth filtering branch, and the inverting input terminal of the first operational amplifier is short - circuited to its output terminal.

[0032] A preferred embodiment of another technical solution adopted by the present utility model to solve the above - mentioned technical problems is as follows: the second - stage low - pass filtering module includes a fifth filtering branch, a sixth filtering branch, and a fourth operational amplifier; the fifth filtering branch is formed by connecting a tenth resistor and a sixth capacitor in series, and the sixth filtering branch is formed by connecting a ninth resistor and a fifth capacitor in series; the resistor end of the fifth filtering branch is connected to the output end of the first operational amplifier, and the capacitor end of the fifth filtering branch is grounded; the resistor end of the sixth filtering branch is connected to the middle node of the fifth filtering branch, and the capacitor end of the sixth filtering branch is grounded; the non - inverting input terminal of the fourth operational amplifier is connected to the middle node of the sixth filtering branch, and the inverting input terminal of the fourth operational amplifier is short - circuited to its output terminal;

[0033] The output end of the fourth operational amplifier is connected to the input end of the ADC conversion module;

[0034] The resistance values of the fourth resistor and the fifth resistor are equal, and the resistance values of the ninth resistor and the tenth resistor are equal.

[0035] Compared with the prior art, the advantages of the present utility model are as follows: the output current of the DC brushed motor is processed successively by the voltage signal pickup module, the emitter - follower module, the automatic gain amplification module, the second - stage fourth - order low - pass filtering module, and the ADC conversion module to form an accurately sampled current signal and input it into the MCU controller. The accurate sampling of the current of the DC brushed motor of the drying machine is realized by a hardware circuit, enabling the MCU controller to obtain a current sampling value with low error, high smoothness, and few harmonics, and further controlling the operation of the DC brushed motor more accurately and without delay.

[0036] Among them, the voltage signal pickup module converts the output current signal of the DC brushed motor into a voltage signal through a differential equal - ratio operation circuit, and an anti - aliasing filtering module is added in the front stage, which can effectively filter out the differential - mode and common - mode spike interference and burr signals, achieving a good filtering effect in the first stage.

[0037] The emitter follower module can play roles such as voltage buffering, reducing signal distortion, impedance matching to improve signal transmission efficiency, current gain, etc., so that the subsequent circuit module can pick up the signal of the previous circuit module more completely.

[0038] The automatic gain amplification module realizes that the MCU controller automatically adjusts the gain magnification according to different hanging weight sections, realizes segmented gain amplification, and satisfies good current sampling effects in the entire range from 0 hanging weight to the maximum hanging weight.

[0039] The second-order fourth-order low-pass filter module can further filter out the intermediate-frequency voltage signal to obtain a smoother voltage signal. The ADC conversion module converts the smoothed voltage signal processed by the second-order fourth-order low-pass filter module into a digital signal for accurately sampling current, and feeds it back to the MCU controller. Description of the Drawings

[0040] The following will further describe the present invention in detail with reference to the drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are only drawn for the purpose of explaining the preferred embodiments and should not be regarded as limiting the scope of the present invention. In addition, unless otherwise specified, the drawings only schematically show the composition or structure of the described object and may include exaggerated displays, and the drawings are not necessarily drawn to scale.

[0041] Figure 1 It is the circuit block diagram of the first existing solution in the background technology;

[0042] Figure 2 It is the overall block diagram of the precise sampling circuit of the DC brushed motor of the clothes dryer;

[0043] Figure 3 It is the overall circuit diagram of the precise sampling circuit of the DC brushed motor of the clothes dryer;

[0044] Figure 4 It is the circuit diagram of the voltage signal pickup module;

[0045] Figure 5 It is the voltage waveform diagram at both ends of the sixth resistor;

[0046] Figure 6 It is the voltage waveform diagram after being processed by the anti-aliasing filter module and the differential proportional operation module;

[0047] Figure 7 It is the circuit diagram of the emitter follower module and the automatic gain amplification module;

[0048] Figure 8 It is the circuit diagram of the second-order fourth-order low-pass filter module;

[0049] Figure 9It is the voltage waveform diagram processed by the second-order fourth-order low-pass filter module;

[0050] Figure 10 It is the circuit diagram of the ADC conversion module;

[0051] Figure 11 It is the circuit diagram of the MCU controller;

[0052] Description of the reference numerals:

[0053] Precise sampling circuit 100 of the DC brush motor of the clothes dryer, DC brush motor M1, voltage signal pickup module 101, sixth resistor R6, anti-aliasing filter module 10, second resistor R2, first capacitor C1, first filter branch L1, seventh resistor R7, fourth capacitor C4, second filter branch L2, differential equal-ratio operation module 20, third operational amplifier IC3A, third resistor R3, first resistor R1, eighth resistor R8, emitter follower module 102, second operational amplifier IC2A, automatic gain amplification module 103, automatic gain amplifier U1, second-order fourth-order low-pass filter module 104, first-stage low-pass filter module 30, third filter branch L3, fourth resistor R4, second capacitor C2, fourth filter branch L4, fifth resistor R5, third capacitor C3, first operational amplifier IC1A, second-stage low-pass filter module 40, fifth filter branch L5, tenth resistor R10, sixth capacitor C6, sixth filter branch L6, ninth resistor R9, fifth capacitor C5, fourth operational amplifier IC4A, ADC conversion module 105, MCU controller 106. Detailed implementation manners

[0054] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Those skilled in the art will appreciate that these descriptions are only descriptive and exemplary, and should not be construed as limiting the protection scope of the present invention.

[0055] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. The terms "first" and "second" are only for descriptive convenience and have no other directional meaning, and should not be construed as limiting the present invention.

[0056] As Figure 2 and Figure 3Shown is the precise sampling circuit 100 of the DC brushed motor of the clothes dryer provided in this embodiment, which includes a DC brushed motor M1, a voltage signal pickup module 101, an emitter follower module 102, an automatic gain amplification module 103, a second-order four-stage low-pass filter module 104, an ADC conversion module 105, and an MCU controller 106 that are electrically connected in sequence.

[0057] Among them, the DC brushed motor M1 is supplied with a DC power supply VCC1 by the power supply module of the clothes dryer (not shown in the figure). Its output current Io is processed by the voltage signal pickup module 101, the emitter follower module 102, the automatic gain amplification module 103, the second-order four-stage low-pass filter module 104, and the ADC conversion module 105 in sequence to form a precise sampling current signal Ii and input it into the MCU controller 106. The MCU controller 106 controls the operation of the DC brushed motor M1 in a feedback manner according to the change of the precise sampling current Ii.

[0058] As Figure 11 shown, for the MCU controller chip adopted in this embodiment, its pin 5 and pin 3 respectively output a control signal CTL1 and CTL2 to the DC brushed motor M1.

[0059] For example, when too many or too heavy clothes are hung on the clothes drying rod assembly, the hanging weight may exceed the rated load when the DC brushed motor M1 drives the clothes drying rod assembly to rise. A rated load current value I1 is preset in the MCU controller 106. When it is detected that Ii > I1, the MCU controller 106 triggers overload protection, sends a stop operation command to the DC brushed motor M1, and issues a warning at the same time.

[0060] Another example is that for an electric clothes dryer embedded in the ceiling, the situation may occur that the DC brushed motor M1 drives the clothes drying rod assembly to rise and collide with the ceiling. A rising resistance encounter current value I2 is preset in the MCU controller 106. When it is detected that Ii > I2, the MCU controller 106 triggers rising resistance encounter protection, sends a stop operation command and a start reverse command to the DC brushed motor M1, and drives the clothes drying rod assembly to descend a certain distance, thereby protecting the clothes drying rod assembly and the ceiling.

[0061] As Figure 4 shown, the voltage signal pickup module 101 includes a sixth resistor R6 serving as a voltage sampling resistor, an anti-aliasing filter module 10, and a differential equal-ratio operation module 20. One end of the sixth resistor R6 is connected to the current output end of the DC brushed motor M1, and the other end is grounded to GND.

[0062] The anti-aliasing filter module 10 is connected in parallel across the two ends of the sixth resistor R6, and includes a first filter branch L1 formed by series connection of a second resistor R2 and a first capacitor C1, and a second filter branch L2 formed by series connection of a seventh resistor R7 and a fourth capacitor C4. The resistor end of the first filter branch L1 is connected to the node between the sixth resistor R6 and the current output end of the DC brushed motor M1, and the capacitor end of the first filter branch L1 is grounded to GND. The resistor end of the second filter branch L2 is connected to the node between the sixth resistor R6 and the ground end GND, and the capacitor end of the second filter branch L2 is grounded to GND.

[0063] The differential equal-ratio operation module 20 includes a third operational amplifier IC3A, a third resistor R3, a first resistor R1, and an eighth resistor R8. The third resistor R3 is connected between the intermediate node of the first filter branch L1 and the inverting input terminal (pin 2) of the third operational amplifier IC3A, the eighth resistor R8 is connected between the intermediate node of the second filter branch L2 and the non-inverting input terminal (pin 3) of the third operational amplifier IC3A, and the first resistor R1 is connected between the inverting input terminal (pin 2) and the output terminal (pin 1) of the third operational amplifier IC3A. Among them, the differential equal-ratio operation module 20 is a 1:1 operation circuit.

[0064] Among them, the resistance values of the second resistor R2, the seventh resistor R7, the third resistor R3, and the eighth resistor R8 are equal, that is, R2 = R7 = R3 = R8, and the resistance value of the first resistor R1 is twice the resistance value of the third resistor R3, that is, R1 = 2×R3.

[0065] As Figure 5 shown is the voltage waveform across the two ends of the sixth resistor R6. As Figure 6 shown is the voltage waveform after being processed by the anti-aliasing filter module 10 and the differential equal-ratio operation module 20. It can be seen that the voltage signal pickup module 101 converts the output current Io signal of the DC brushed motor M1 into a voltage signal through a differential equal-ratio 1:1 operation circuit, and adds the anti-aliasing filter module 10 composed of the first filter branch L1 and the second filter branch L2 at the front stage, which can effectively filter out the differential-mode and common-mode spike interference and burr signals, and has a good filtering effect in the first stage.

[0066] As Figure 7 shown, the emitter follower module 102 includes a second operational amplifier IC2A. The non-inverting input terminal (pin 3) of the second operational amplifier IC2A is connected to the output terminal (pin 1) of the third operational amplifier IC3A, and the inverting input terminal (pin 2) of the second operational amplifier IC2A is short-circuited to its output terminal (pin 1). The output terminal (pin 1) of the second operational amplifier IC2A is connected to the input terminal of the automatic gain amplification module 103.

[0067] The emitter follower module 102 can function as a voltage buffer, reduce signal distortion, perform impedance matching to improve signal transmission efficiency, provide current gain, etc., enabling the subsequent circuit module to pick up the signal from the previous circuit module more completely.

[0068] As Figure 7 shown, the automatic gain amplification module 103 includes an automatic gain amplifier U1. In this embodiment, the automatic gain amplifier U1 directly uses an automatic gain amplification chip. Among them, pin 14 is the input terminal, connected to the output terminal (pin 1) of the second operational amplifier IC2A of the previous emitter follower module 102. Pin 15 is grounded to GND. Pin 9 is the output terminal, connected to the subsequent second-order four-stage low-pass filter module 104. Pins 3 - 7 are digital signal input terminals, corresponding to five high and low level digital signals G4 - G0 respectively. The MCU controller 106 inputs five high and low level digital signals G0 - G4 to the automatic gain amplifier U1. The MCU controller 106 adjusts the levels of the five high and low level digital signals G0 - G4 automatically to obtain at least four gain multiples.

[0069] When the laundry pole assembly has 0 hanging weight and the maximum hanging weight, the output current Io of the DC brush motor M1 differs significantly. To achieve good current sampling effects throughout the range from 0 hanging weight to the maximum hanging weight, the automatic gain amplification module 103 is adopted. The MCU controller 106 automatically adjusts the gain multiple according to different hanging weight sections to achieve segmented gain amplification.

[0070] For example, in this embodiment, the maximum hanging weight is set to 40 kg. Therefore, the gain multiple is preset to be adjusted in segments every 10 kg as follows: when the hanging weight is 0 kg - 10 kg, it is automatically amplified by A times; when the hanging weight is 10 kg - 20 kg, it is automatically amplified by B times; when the hanging weight is 20 kg - 30 kg, it is automatically amplified by C times; when the hanging weight is 30 kg - 40 kg, it is automatically amplified by D times.

[0071] The preferred multiples and the corresponding combinations of the high and low level digital signals G0 - G4 are as follows:

[0072] ① A = 20, G0, G1, G2, G3, G4 = 1, 1, 1, 0, 0;

[0073] ② B = 10, G0, G1, G2, G3, G4 = 0, 1, 1, 0, 0;

[0074] ③ C = 5, G0, G1, G2, G3, G4 = 0, 0, 1, 0, 0;

[0075] ④ D = 0.5, G0, G1, G2, G3, G4 = 0, 0, 0, 0, 0.

[0076] In other embodiments, according to the size of the maximum hanging weight, the number of sections and the segmentation intervals can be adjusted, and correspondingly, the ports and combination modes of the high and low level digital signals can be increased or decreased to correspond to the gain ratios of different sections.

[0077] As Figure 8 shown, the second-order fourth-order low-pass filter module 104 includes a first-stage low-pass filter module 30 and a second-stage low-pass filter module 40 connected in sequence. Among them, the first-stage low-pass filter module 10 includes a third filter branch L3, a fourth filter branch L4, and a first operational amplifier IC1A. The third filter branch L3 is formed by connecting a fourth resistor R4 and a second capacitor C2 in series, and the fourth filter branch L4 is formed by connecting a fifth resistor R5 and a third capacitor C3 in series. The resistor terminal of the third filter branch L3 is connected to the output terminal of the automatic gain amplification module 103, that is, the pin 9 of the automatic gain amplifier U1, and the capacitor terminal of the third filter branch L3 is grounded to GND. The resistor terminal of the fourth filter branch L4 is connected to the middle node of the third filter branch L3, and the capacitor terminal of the fourth filter branch L4 is grounded to GND. The non-inverting input terminal (pin 3) of the first operational amplifier IC1A is connected to the middle node of the fourth filter branch L4, and the inverting input terminal (pin 2) of the first operational amplifier IC1A is short-circuited to its output terminal (pin 1).

[0078] Further, the second-stage low-pass filter module 40 includes a fifth filter branch L5, a sixth filter branch L6, and a fourth operational amplifier IC4A. The fifth filter branch L5 is formed by connecting a tenth resistor R10 and a sixth capacitor C6 in series, and the sixth filter branch L6 is formed by connecting a ninth resistor R9 and a fifth capacitor C5 in series. The resistor terminal of the fifth filter branch L5 is connected to the output terminal (pin 1) of the first operational amplifier IC1A, and the capacitor terminal of the fifth filter branch L5 is grounded to GND. The resistor terminal of the sixth filter branch L6 is connected to the middle node of the fifth filter branch L5, and the capacitor terminal of the sixth filter branch L6 is grounded to GND. The non-inverting input terminal (pin 3) of the fourth operational amplifier IC4A is connected to the middle node of the sixth filter branch L6, and the inverting input terminal (pin 2) of the fourth operational amplifier IC4A is short-circuited to its output terminal (pin 1). The output terminal of the fourth operational amplifier IC4A is connected to the input terminal of the ADC conversion module 105.

[0079] Preferably, the resistance values of the fourth resistor R4 and the fifth resistor R5 are equal. In this embodiment, R4 = R5 = 107 kΩ is selected. The resistance values of the ninth resistor and the tenth resistor are equal. In this embodiment, R9 = R10 = 49.9 kΩ is selected.

[0080] As Figure 9 shown is the voltage waveform after being processed by the second-order fourth-order low-pass filter module 104. It can be seen that the second-order fourth-order low-pass filter module 104 can further filter out the intermediate-frequency voltage signal to obtain a smoother voltage signal.

[0081] As Figure 10 shown, for the ADC chip adopted by the ADC conversion module 105 in this embodiment, its pin 8 is the input terminal, pin 6 is grounded to GND, pin 3 is the power input terminal, and is supplied with the DC power supply VCC2 by the power supply module of the drying machine. Pin 4 is the output terminal. Among them, the input terminal (pin 8) of the ADC conversion module 105 is connected to the output terminal of the second-order four-stage low-pass filter module 104, that is, the output terminal (pin 1) of the fourth operational amplifier IC4A. The output terminal (pin 4) of the ADC conversion module 105 outputs the accurate sampling current Ii and inputs it to pin 6 of the MCU controller 106.

[0082] So far, after the last analog-to-digital conversion by the ADC conversion module 105, the smoothed voltage signal processed by the second-order four-stage low-pass filter module 104 is converted into a digital signal of the accurate sampling current Ii, and fed back to the MCU controller 106, thereby realizing the accurate sampling of the current of the DC brushed motor M1 of the drying machine, enabling the MCU controller 106 to obtain a current sampling value with low error, high smoothness, and few harmonics, and further controlling the operation of the DC brushed motor M1 more accurately and without delay.

[0083] It should be noted that similar reference numerals represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it may not be further defined and explained in subsequent drawings.

[0084] The above introduces the accurate sampling circuit of the DC brushed motor of the drying machine provided by the present utility model. Specific examples are used herein to elaborate on the principle and implementation manner of the present utility model. The description of the above embodiments is only used to help understand the present utility model and its core idea. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present utility model, several improvements and modifications can be made to the present utility model, and these improvements and modifications also fall within the protection scope of the claims of the present utility model.

Claims

1. The precise sampling circuit of the DC brushed motor of the clothes drying machine is characterized by: It includes a DC brushed motor, a voltage signal pickup module, an emitter follower module, an automatic gain amplifier module, a secondary fourth-order low-pass filter module, an ADC conversion module and an MCU controller which are electrically connected in sequence; The output current of the DC brush motor is processed by the voltage signal pickup module, the emitter follower module, the automatic gain amplifier module, the secondary fourth-order low-pass filter module, and the ADC conversion module in sequence to form an accurate sampling current input to the MCU controller. The MCU controller reversely controls the operation of the DC brush motor through electrical connection according to the change of the accurate sampling current; The voltage signal pickup module includes a sixth resistor as a voltage sampling resistor, an anti-aliasing filter module and a differential proportional operation module; one end of the sixth resistor is connected to the current output end of the DC brushed motor, and the other end is grounded; The anti-aliasing filter module comprises a first filter branch formed by a second resistor and a first capacitor connected in series, and a second filter branch formed by a seventh resistor and a fourth capacitor connected in series; The resistance end of the first filtering branch is connected to the node between the sixth resistor and the current output end of the DC brushed motor, and the capacitance end of the first filtering branch is grounded; The resistance end of the second filtering branch is connected to a node between the sixth resistor and the ground end, and the capacitance end of the second filtering branch is grounded; The differential proportional operation module includes a third operational amplifier, a third resistor, a first resistor and an eighth resistor; the third resistor is connected between the middle node of the first filter branch and the inverting input terminal of the third operational amplifier, the eighth resistor is connected between the middle node of the second filter branch and the non-inverting input terminal of the third operational amplifier, and the first resistor is connected between the inverting input terminal and the output terminal of the third operational amplifier.

2. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 1, characterized in that: The resistance values ​​of the second resistor, the seventh resistor, the third resistor and the eighth resistor are equal; the resistance value of the first resistor is twice the resistance value of the third resistor.

3. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 1, characterized in that: The emitter follower module includes a second operational amplifier, the in-phase input terminal of the second operational amplifier is connected to the output terminal of the third operational amplifier, the inverting input terminal of the second operational amplifier and its output terminal are short-circuited; the output terminal of the second operational amplifier is connected to the input terminal of the automatic gain amplifier module.

4. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 1, characterized in that: The automatic gain amplification module includes an automatic gain amplifier; the MCU controller inputs five high and low level digital signals to the automatic gain amplifier, and the MCU controller automatically adjusts the levels of the five high and low level digital signals to obtain at least four gain ratios.

5. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 1, characterized in that: The two-stage fourth-order low-pass filter module includes a first-stage low-pass filter module and a second-stage low-pass filter module connected front and back; The first-stage low-pass filter module includes a third filter branch, a fourth filter branch and a first operational amplifier; the third filter branch is formed by a fourth resistor and a second capacitor connected in series, and the fourth filter branch is formed by a fifth resistor and a third capacitor connected in series; the resistor end of the third filter branch is connected to the output end of the automatic gain amplifier module, and the capacitor end of the third filter branch is grounded; The resistor end of the fourth filter branch is connected to the middle node of the third filter branch, and the capacitor end of the fourth filter branch is grounded; the non-inverting input end of the first operational amplifier is connected to the middle node of the fourth filter branch, and the inverting input end of the first operational amplifier and its output end are short-circuited; The second-stage low-pass filter module includes a fifth filter branch, a sixth filter branch and a fourth operational amplifier; the fifth filter branch is formed by connecting a tenth resistor and a sixth capacitor in series, and the sixth filter branch is formed by connecting a ninth resistor and a fifth capacitor in series; the resistance end of the fifth filter branch is connected to the output end of the first operational amplifier, and the capacitance end of the fifth filter branch is grounded; The resistor end of the sixth filter branch is connected to the middle node of the fifth filter branch, and the capacitor end of the sixth filter branch is grounded; the non-inverting input end of the fourth operational amplifier is connected to the middle node of the sixth filter branch, and the inverting input end of the fourth operational amplifier and its output end are short-circuited; The output end of the fourth operational amplifier is connected to the input end of the ADC conversion module.

6. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 1, characterized in that: The input end of the ADC conversion module is connected to the output end of the secondary fourth-order low-pass filter module, and the output end of the ADC conversion module outputs the precise sampling current and inputs it into the MCU controller.

7. The precise sampling circuit of the DC brushed motor of the clothes drying machine is characterized by: It includes a DC brushed motor, a voltage signal pickup module, an emitter follower module, an automatic gain amplifier module, a secondary fourth-order low-pass filter module, an ADC conversion module and an MCU controller which are electrically connected in sequence; The output current of the DC brush motor is processed by the voltage signal pickup module, the emitter follower module, the automatic gain amplifier module, the secondary fourth-order low-pass filter module, and the ADC conversion module in sequence to form an accurate sampling current signal which is input into the MCU controller. The MCU controller reversely controls the operation of the DC brush motor through electrical connection according to the change of the accurate sampling current; The voltage signal pickup module includes a sixth resistor as a voltage sampling resistor, an anti-aliasing filter module and a differential proportional operation module; one end of the sixth resistor is connected to the current output end of the DC brushed motor, and the other end is grounded; The anti-aliasing filter module comprises a first filter branch formed by a second resistor and a first capacitor connected in series, and a second filter branch formed by a seventh resistor and a fourth capacitor connected in series; The resistance end of the first filtering branch is connected to the node between the sixth resistor and the current output end of the DC brushed motor, and the capacitance end of the first filtering branch is grounded; The resistance end of the second filtering branch is connected to a node between the sixth resistor and the ground end, and the capacitance end of the second filtering branch is grounded; The differential proportional operation module includes a third operational amplifier, a third resistor, a first resistor and an eighth resistor; the third resistor is connected between the middle node of the first filtering branch and the inverting input terminal of the third operational amplifier, the eighth resistor is connected between the middle node of the second filtering branch and the non-inverting input terminal of the third operational amplifier, and the first resistor is connected between the inverting input terminal and the output terminal of the third operational amplifier; The automatic gain amplification module includes an automatic gain amplifier; the MCU controller inputs five high and low level digital signals to the automatic gain amplifier, and the MCU controller automatically adjusts the levels of the five high and low level digital signals to obtain at least four gain ratios.

8. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 7, characterized in that: The emitter follower module comprises a second operational amplifier, the in-phase input terminal of the second operational amplifier is connected to the output terminal of the third operational amplifier, the inverting input terminal of the second operational amplifier and its output terminal are short-circuited; the output terminal of the second operational amplifier is connected to the input terminal of the automatic gain amplifier module; The resistance values ​​of the second resistor, the seventh resistor, the third resistor and the eighth resistor are equal; the resistance value of the first resistor is twice the resistance value of the third resistor; The input end of the ADC conversion module is connected to the output end of the secondary fourth-order low-pass filter module, and the output end of the ADC conversion module outputs the precise sampling current and inputs it into the MCU controller.

9. The precise sampling circuit of the DC brushed motor for clothes drying machine according to claim 7, characterized in that: The two-stage fourth-order low-pass filter module includes a first-stage low-pass filter module and a second-stage low-pass filter module connected front and back; The first-stage low-pass filter module includes a third filter branch, a fourth filter branch and a first operational amplifier; the third filter branch is formed by a fourth resistor and a second capacitor connected in series, and the fourth filter branch is formed by a fifth resistor and a third capacitor connected in series; the resistor end of the third filter branch is connected to the output end of the automatic gain amplifier module, and the capacitor end of the third filter branch is grounded; The resistance end of the fourth filter branch is connected to the middle node of the third filter branch, and the capacitance end of the fourth filter branch is grounded; the non-inverting input end of the first operational amplifier is connected to the middle node of the fourth filter branch, and the inverting input end of the first operational amplifier and its output end are short-circuited.

10. The precise sampling circuit of the DC brushed motor of the clothes drying machine according to claim 9, characterized in that: The second-stage low-pass filter module includes a fifth filter branch, a sixth filter branch and a fourth operational amplifier; the fifth filter branch is formed by connecting a tenth resistor and a sixth capacitor in series, and the sixth filter branch is formed by connecting a ninth resistor and a fifth capacitor in series; the resistance end of the fifth filter branch is connected to the output end of the first operational amplifier, and the capacitance end of the fifth filter branch is grounded; The resistor end of the sixth filter branch is connected to the middle node of the fifth filter branch, and the capacitor end of the sixth filter branch is grounded; the non-inverting input end of the fourth operational amplifier is connected to the middle node of the sixth filter branch, and the inverting input end of the fourth operational amplifier and its output end are short-circuited; The output end of the fourth operational amplifier is connected to the input end of the ADC conversion module; The resistance values ​​of the fourth resistor and the fifth resistor are equal, and the resistance values ​​of the ninth resistor and the tenth resistor are equal.

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