Motor control circuit of food processor

Abstract

The invention provides a motor control circuit of a food processor, which comprises a power supply module, a control module, a zero cross detection module, a motor, a driving module and a common mode inductor connected in series in the motor control circuit, a first sampling point and a second sampling point which are connected with the control module are arranged on the current inflow side and the current outflow side of the common mode inductor respectively, a first voltage value is obtained through sampling of the first sampling point, and a second voltage value is obtained at the second sampling point through resistive partial pressure of the common mode inductor. And a voltage drop value between the first sampling point and the second sampling point is obtained according to a difference value between the first voltage value and the second voltage value, and the control module obtains a current value of the motor according to the voltage drop value.

Description

Technical Field

[0001] The invention belongs to the field of food processing machines, and in particular relates to a motor protection circuit of a food processing machine. Background Art

[0002] Existing food processing machines usually have a current detection circuit to detect the load current, such as Figure 1 As shown, the current detection circuit includes a sampling resistor and an operational amplifier. The operational amplifier and the sampling resistor are relatively expensive, which increases the manufacturing cost of the food processor. The operational amplifier usually amplifies the collected signal. While amplifying the signal, the interference signal is also amplified, resulting in low reliability of the collected signal. Due to the difference in control frequency, the filter matching of the operational amplifier is also more complicated, and the filtering frequency band is single, resulting in unsatisfactory signal acquisition effect. When the amplification factor of the operational amplifier is high, the accuracy requirements for the resistors used are also high, so the process consistency control is relatively complex. In addition, in order to reduce interference, the design and wiring of the peripheral circuits of the operational amplifier are also difficult, and the design cost, manufacturing cost and quality control cost are all high.

[0003] The patent application number CN201821908775.9 discloses a food processor overcurrent detection circuit and a food processor. The food processor overcurrent detection circuit includes a power supply circuit, an inductance filter circuit and a controller. The controller includes a current detection port electrically connected to the rear end of the inductance filter circuit. The controller integrates an operational amplifier module electrically connected to the current detection port. The controller detects the electrical signal input to the power supply circuit through the current detection port and amplifies the electrical signal through the operational amplifier module. This arrangement still requires the operational amplifier module to participate in current detection, so it is impossible to avoid the problem that the operational amplifier module amplifies the interference signal and causes the collected signal to be inaccurate. Summary of the invention

[0004] The object of the present invention is to provide a motor control circuit for a food processing machine which has low cost, stable acquisition signal value and accurate detection.

[0005] In order to solve the above technical problems, the present invention provides a motor control circuit of a food processing machine, comprising a power module, a control module, a zero-crossing detection module, a motor and a drive module, and also comprising a common-mode inductor connected in series in the motor control circuit, wherein a first sampling point and a second sampling point connected to the control module are respectively provided on a current inflow side and a current outflow side of the common-mode inductor, the first sampling point samples and obtains a first voltage value, and a second voltage value is obtained at the second sampling point by utilizing the resistive voltage division of the common-mode inductor, and then a voltage drop value between the first sampling point and the second sampling point is obtained according to the difference between the first voltage value and the second voltage value, and the control module obtains the current value of the motor according to the voltage drop value.

[0006] Further, Vcc is connected to the first sampling point, the first voltage value is the nominal voltage value, and the second voltage value is the divided voltage value after the common-mode inductor resistive voltage division; or, Vcc is connected to the second sampling point, the second voltage value is the nominal voltage value, and the first voltage value is the divided voltage value before voltage division.

[0007] Furthermore, obtaining the current value of the motor includes the control module calculating the current value of the motor according to the voltage drop value and the resistance value of the common mode inductor.

[0008] Furthermore, the resistance of the common mode inductor is R, 10mΩ≤R≤60mΩ.

[0009] Furthermore, the control module performs AD conversion on the voltage drop value to collect the current value of the motor or determine whether the motor has current.

[0010] Furthermore, the control module has a built-in AD threshold, and the control module compares the collected AD value with the built-in AD threshold, and determines whether the motor has current according to the relationship between the AD value and the AD threshold.

[0011] Furthermore, the driving module includes a thyristor, and when the control module determines that the motor has current, the magnitude of the current value is determined by the thyristor chopping point.

[0012] Furthermore, the driving module includes a thyristor, and the control module obtains a current resolution of I0 according to the voltage drop value of the common-mode inductor. The control module determines that the motor has current, and the current value of the motor is I. When I>I0, the control module directly obtains the current value of the motor. When I≤I0, the size of the current value is determined by the thyristor chopping point.

[0013] Furthermore, the AD conversion signal value of the first sampling point is a, the AD value is b, the AD threshold is c, the current value of the motor is I, and I=(ab) / c.

[0014] Furthermore, the control module matches the control mode according to the current value of the motor, and the control module includes a speed detection unit. The control mode matching according to the current value of the motor includes controlling the motor to speed up, slow down, stop, and reverse, or any combination thereof.

[0015] The beneficial effects of the present invention are:

[0016] 1. The motor control circuit of the food processing machine does not have an operational amplifier and a sampling resistor, but uses the common-mode inductor in the control circuit as a current acquisition device, and uses the resistive voltage divider of the common-mode inductor to set sampling points on the current inflow side and the current outflow side of the common-mode inductor, respectively, to obtain two sampled voltage values ​​and calculate the difference between the two sampling points to obtain the voltage drop value, and the control module obtains the current value of the motor according to the voltage drop value. Setting the motor control circuit in this way is equivalent to using the original common-mode inductor device in the circuit for circuit detection, removing the sampling resistor, operational amplifier and peripheral circuit, reducing the cost of circuit components, simplifying the motor control circuit, reducing the design difficulty of the control circuit, and reducing the layout and process difficulty of the circuit board. Obtaining the current of the motor through the common-mode inductor can avoid signal interference caused by the operational amplifier, making the signal acquisition more accurate, and the control module can flexibly adjust the control program according to the current value to protect the motor and extend the service life of the motor.

[0017] 2. Connect Vcc as the first sampling point on the current inflow side of the common-mode inductor, and set it to the nominal voltage value. The current outflow side is the second sampling point, which is the divided voltage value after voltage division. The nominal voltage value can be connected either on the current inflow side or on the current outflow side, so as to obtain the absolute value of the difference between the first sampling point and the second sampling point. The current value of the motor includes the current value of the motor calculated by the control module according to the voltage drop value and the resistance value of the common-mode inductor. The resistance range of the common-mode inductor is between 10mΩ and 60mΩ. The control module performs AD conversion on the voltage drop value to collect the current value of the motor or determine whether the motor has current. The drive module includes a thyristor. When the control module determines that the motor has current, it determines the size of the current value through the thyristor chopping point, so as to better match the control mode of the motor.

[0018] 3. The control module has a built-in AD threshold. The control module compares the collected AD value with the built-in AD threshold, and determines whether the motor has current based on the relationship between the AD value and the AD threshold. When it is determined that current is flowing through the motor, the current size is determined by the position of the thyristor chopping point, thereby accurately obtaining the current value of the motor. The detection is accurate and the circuit is simple.

[0019] 4. When the control module detects that the motor has current flowing through it, it compares the current resolution I0 of the common mode inductor with the motor current value. When the motor current value I is greater than I0, the control module can directly obtain the motor current value through the resistance and voltage drop of the common mode inductor. When the motor current value I is less than or equal to I0, the current value is determined by the opening angle of the thyristor, thereby obtaining the precise current value of the motor when the current is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The figure is a general block diagram of a motor control circuit of an existing food processor in the background technology.

[0022] Figure 2 This is a general block diagram of the motor control circuit of the food processor described in Example 1.

[0023] Figure 3 This is the motor control circuit of the food processor described in Example 1.

[0024] Figure 4 This is the zero-crossing detection circuit of the food processor described in the first embodiment.

[0025] Figure 5 This is a waveform diagram after the alternating current conversion in Example 1.

[0026] Figure 6 This is a current curve diagram of the control module in Example 1. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0028] The present invention provides a motor control circuit of a food processing machine, comprising a power module, a control module, a zero-crossing detection module, a motor and a drive module, and also comprising a common-mode inductor connected in series in the motor control circuit, wherein a first sampling point and a second sampling point connected to the control module are respectively provided on a current inflow side and a current outflow side of the common-mode inductor, wherein a first voltage value is sampled and obtained at the first sampling point, a second voltage value is obtained at the second sampling point by utilizing the resistive voltage division of the common-mode inductor, and then a voltage drop value between the first sampling point and the second sampling point is obtained according to a difference between the first voltage value and the second voltage value, and the control module obtains a current value of the motor according to the voltage drop value.

[0029] The motor control circuit of the food processing machine does not have an operational amplifier and a sampling resistor, but uses the common-mode inductor in the control circuit as a current acquisition device, and uses the resistive voltage divider of the common-mode inductor to set sampling points on the current inflow side and the current outflow side of the common-mode inductor respectively, so as to obtain two sampled voltage values ​​and calculate the difference between the two sampling points to obtain the voltage drop value, and the control module obtains the current value of the motor according to the voltage drop value. Setting the motor control circuit in this way is equivalent to using the original common-mode inductor device in the circuit for circuit detection, removing the sampling resistor, operational amplifier and peripheral circuit, reducing the cost of circuit components, simplifying the motor control circuit, reducing the design difficulty of the control circuit, and reducing the layout and process difficulty of the circuit board. Obtaining the current of the motor through the common-mode inductor can avoid signal interference caused by the operational amplifier, making the signal acquisition more accurate, and the control module can flexibly adjust the control program according to the current value to protect the motor and extend the service life of the motor.

[0030] After the common mode inductor flows through, the control module is given the same calibration value, the first sampling point is set to collect the first voltage value before the flow, and the second sampling point is set to collect the second voltage value after the flow, and the first voltage value and the second voltage value are input to the control module, and the control module compares the voltage drop value before and after the flow through the common mode inductor to obtain the current value in the current load circuit. Further, the current value is judged, the large current is directly obtained, and the small current is determined by the thyristor common mode inductor. The control module matches different control modes according to the current value to protect the motor.

[0031] As a preference, Figure 2 As shown, Vcc is connected at the first sampling point, the first voltage value is the nominal voltage value, and the second voltage value is the divided voltage value after the common-mode inductor resistive voltage division. Obtaining the current value of the motor includes the control module calculating the current value of the motor according to the voltage drop value and the resistance value of the common-mode inductor, the resistance value of the common-mode inductor is R, 10mΩ≤R≤60mΩ, preferably R is 40mΩ.

[0032] Vcc is connected to the common-mode inductor current inflow side as the first sampling point, and is set to the nominal voltage value. The current outflow side is the second sampling point, which is the divided voltage value after voltage division. The nominal voltage value can be connected either to the current inflow side or to the current outflow side, so as to obtain the absolute value of the difference between the first sampling point and the second sampling point. The current value of the motor includes the current value of the motor calculated by the control module according to the voltage drop value and the resistance value of the common-mode inductor. The resistance range of the common-mode inductor is between 10mΩ and 60mΩ. The control module performs AD conversion on the voltage drop value to collect the current value of the motor or determine whether the motor has current. The drive module includes a thyristor. When the control module determines that the motor has current, it determines the size of the current value through the thyristor chopping point, so as to better match the control mode of the motor.

[0033] The control module has a built-in AD threshold, and the control module compares the collected AD value with the built-in AD threshold, and determines whether the motor has current according to the magnitude relationship between the AD value and the AD threshold. The drive module includes a thyristor, and when it is determined that current is flowing through the motor, the current magnitude is determined by the position of the thyristor chopping point, so as to accurately obtain the current value of the motor. The detection is accurate and the circuit is simple, and no operational amplifier is required, which reduces the cost while eliminating the interference signal caused by the operational amplifier. At the same time, the sampling resistor is omitted, and the current magnitude fluctuation caused by the sampling resistor due to the difference in resistance accuracy is also eliminated. The operational amplifier and its peripheral devices are also omitted, which reduces the difficulty of circuit design and process difficulty.

[0034] The driving module includes a thyristor, and the current resolution obtained by the control module according to the voltage drop value of the common mode inductor is I0. The control module determines that the motor has current, and the current value of the motor is I. When I>I0, the control module directly obtains the current value of the motor. When I≤I0, the magnitude of the current value is determined by the thyristor chopping point. The AD conversion signal value of the first sampling point is a, the AD value is b, the AD threshold is c, and the current value of the motor is I, then I=(ab) / c can be calculated. The control module matches the control mode according to the current value of the motor. The control module includes a speed detection unit. The control mode matches the current value of the motor, including controlling the motor to increase speed, decrease speed, stop, reverse or any combination thereof, so as to protect the motor according to the processing conditions of the food processor and extend the service life of the motor.

[0035] Specifically, Figure 3 As shown, the motor control circuit includes a power input module, a switching power module, a zero-crossing detection module, a common-mode inductor module and a drive module. The power input module is a switching power supply, which is responsible for providing power to the control circuit of the food processor. The switching power supply mainly provides 5V DC power to the control module, the zero-crossing detection module and the drive module. Figure 4 As shown, the zero-crossing detection module converts the AC signal into a square wave signal that can be recognized by the control module. Specifically, the control module is a chip. When the AC power is input, the base voltage of the transistor is greater than the turn-on voltage, the transistor is turned on, and ZT outputs a low level. When the transistor is in the cut-off state, ZT outputs a high level. The waveform of the AC power conversion is as follows Figure 5 shown.

[0036] like Figure 3As shown, in this embodiment, the load is specifically a motor, the resistance of the common-mode inductor is R, the current flows from ACL into the load, flows into one end of the common-mode inductor through the thyristor, and flows back to the ACN end. The flowing current is I, and the voltage V of the I_IN end is V=5-IR. When the current flows from AN through the common-mode inductor, the thyristor, the load, and then flows into ACL, the voltage V of the I_IN end is V=5+IR. Due to the clamping diode, the clamping voltage is not greater than 5.7V. The current curve input to the control module, that is, the chip end, is as shown in Figure 6 As shown. The load is controlled by thyristor, which is a half-controlled switch device, that is, it only needs to be turned on and automatically turned off when it passes through zero. The larger the area that is turned on, the more output is given to the load. Common mode inductor resistance power P = I 2 R, when the resistance is smaller, the heat generated by the common-mode inductor is smaller, and the corresponding temperature rise is lower. High temperature rise will weaken the characteristics of the common-mode inductor, so under normal circumstances, the resistance of the common-mode inductor is relatively small. In this embodiment, R = 40mΩ. When the current flowing through the load is 1A, the average voltage detected by the negative half-wave is V = 5-IR = 5-2*0.02 = 4.96V. The control module performs AD conversion on the voltage signal and converts the voltage signal into an AD signal that can be recognized by the control module for processing. The 5V voltage corresponds to 4096 AD values, and the 1A current flowing through the load is converted to 4063 AD values. Since the clamping diode clamps the positive half-wave, the voltage waveform is an incomplete waveform and cannot be used. Therefore, when using the common-mode inductor for current signal acquisition, the negative half-wave is used for current detection.

[0037] Specifically, the current resolution obtained by the control module according to the voltage drop value of the common-mode inductor is I0. If the current is greater than I0, the control module directly obtains it. If it is less than I0, it is first determined whether there is current. If there is current, a high-precision algorithm is used to calculate the precise current value through the thyristor chopping point. In this embodiment, I0 is 1A, and the control module determines that the motor has current. The current value of the motor is I. When I>I0, the control module directly obtains the current value of the motor through the voltage drop value and the common-mode inductor resistance R. When I≤I0, the current value is lower than the current resolution. Under the premise of judging that there is current, the size of the current value is determined by the thyristor chopping point. Since the motor driving mode is thyristor chopping drive, at the same speed, the closer the chopping point is, the larger the corresponding driving current is, and the closer the chopping point is, the lower the corresponding driving current is.

[0038] The food processor is a wall-breaking machine. Compared with the traditional sampling resistor, the accuracy of the common-mode inductor itself is poor. After the circuit board is manufactured, the common-mode inductor resistance is calibrated through a precise load with a resistance value of R1=220Ω. When U1=220V, R1 is fully driven. The current at this time is I=U1 / R1=1A. At this time, the AD value collected by the chip is the AD threshold, that is, c=1A. The AD threshold c is recorded in the control module as the basic current value.

[0039] When the motor of the food processor starts working and is in a constant speed processing state, the detected AD value is b, then the corresponding motor current value I=(4096-b) / c, and the motor current at this time can be obtained. After adding materials to the processing cup of the food processor, during the normal startup process, the motor current value I is small and cannot meet the resolution requirement. Each common frequency half-wave is divided into 1000 parts according to the power, and the motor drive current can be divided into 1000 parts. The AD value collected by the current determines that there is current flowing through the motor, and then the motor current size at this time is determined by the thyristor chopping point. The food processor has a soft start process when it starts. When the motor starts to the current of 1A, the opening angle at this time is recorded. In this embodiment, the opening angle of the motor current of 1A is 82 parts, and the current corresponding to each part is 0.012A. According to the opening number of the thyristor opening angle, the motor current I=0.012*the opening number of parts is accurately confirmed.

[0040] It is understandable that Vcc may be connected to the second sampling point, the second voltage value is a nominal voltage value, and the first voltage value is a divided voltage value before voltage division.

[0041] It can be understood that the load also includes a heating module. Since the heating power is relatively high and the current value is greater than I0, the current value can be directly measured through the voltage drop value at the first sampling point and the second sampling point of the common-mode inductor and the resistance value of the common-mode inductor.

[0042] In addition to the above preferred embodiments, the technical solutions protected by the present invention are not limited to the above embodiments. It should be pointed out that the combination of multiple technical solutions in any one embodiment, and the combination of the technical solution of any one embodiment with the technical solutions in one or more other embodiments, are within the protection scope of the present invention. Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to it based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A motor control circuit for a food processing machine, characterized in that: The invention comprises a power supply module, a control module, a zero-crossing detection module, a motor and a drive module, and also comprises a common-mode inductor connected in series in the motor control circuit, wherein the current inflow side and the current outflow side of the common-mode inductor are respectively provided with a first sampling point and a second sampling point connected to the control module, the first sampling point samples to obtain a first voltage value, and the second voltage value is obtained at the second sampling point by using the resistive voltage division of the common-mode inductor, and then the voltage drop value between the first sampling point and the second sampling point is obtained according to the difference between the first voltage value and the second voltage value, and the control module obtains the current value of the motor according to the voltage drop value.

2. The motor control circuit according to claim 1, characterized in that: When Vcc is connected to the first sampling point, the first voltage value is a nominal voltage value, and the second voltage value is a divided voltage value after common-mode inductor resistive voltage division; or, when Vcc is connected to the second sampling point, the second voltage value is a nominal voltage value, and the first voltage value is a divided voltage value before voltage division.

3. The motor control circuit according to claim 1, characterized in that: Acquiring the current value of the motor includes the control module calculating the current value of the motor according to the voltage drop value and the resistance value of the common mode inductor.

4. The motor control circuit according to claim 1, characterized in that: The resistance of the common mode inductor is R, 10mΩ≤R≤60mΩ.

5. The motor control circuit according to claim 1, characterized in that: The control module performs AD conversion on the voltage drop value to collect the current value of the motor or determine whether the motor has current.

6. The motor control circuit according to claim 5, characterized in that: The control module has a built-in AD threshold, and the control module compares the collected AD value with the built-in AD threshold, and determines whether the motor has current according to the magnitude relationship between the AD value and the AD threshold.

7. The motor control circuit according to claim 6, characterized in that: The driving module includes a thyristor, and when the control module determines that the motor has current, the magnitude of the current value is determined by the thyristor chopping point.

8. The motor control circuit according to claim 6, characterized in that: The driving module includes a thyristor, and the current resolution obtained by the control module according to the voltage drop value of the common-mode inductor is I0. The control module determines that the motor has current, and the current value of the motor is I. When I>I0, the control module directly obtains the current value of the motor. When I≤I0, the size of the current value is determined by the thyristor chopping point.

9. The motor control circuit according to claim 6, characterized in that: The AD conversion signal value of the first sampling point is a, the AD value is b, the AD threshold is c, the current value of the motor is I, and I=(ab) / c.

10. The motor control circuit according to claim 1, characterized in that: The control module matches the control mode according to the current value of the motor, and the control module includes a speed detection unit. The control mode matches the current value of the motor, including controlling the motor to increase speed, decrease speed, stop, reverse or any combination thereof.

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