CN108008175B - Current detection method of food processor - Google Patents
Current detection method of food processor Download PDFInfo
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- CN108008175B CN108008175B CN201711170985.2A CN201711170985A CN108008175B CN 108008175 B CN108008175 B CN 108008175B CN 201711170985 A CN201711170985 A CN 201711170985A CN 108008175 B CN108008175 B CN 108008175B
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- 238000001514 detection method Methods 0.000 title claims abstract description 97
- 235000013305 food Nutrition 0.000 title claims abstract description 35
- 238000005070 sampling Methods 0.000 claims abstract description 173
- 238000000034 method Methods 0.000 claims abstract description 42
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 9
- 239000011889 copper foil Substances 0.000 description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 4
- 235000010469 Glycine max Nutrition 0.000 description 3
- 244000068988 Glycine max Species 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 235000013336 milk Nutrition 0.000 description 3
- 239000008267 milk Substances 0.000 description 3
- 210000004080 milk Anatomy 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 230000005856 abnormality Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 235000013322 soy milk Nutrition 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
Abstract
The embodiment of the invention discloses a current detection method of a food processor, wherein the food processor comprises a load loop and a current sampling resistor, wherein the current sampling resistor is connected in series in the load loop and is used for carrying out current detection on the load loop; a load of a food processor comprising a heating device and a motor, the method comprising: and determining a sampling period T in the current detection according to the least common multiple of all the control periods of the load, and determining the sampling times m in the current detection according to the control chopping angle of the load. Through the scheme of the embodiment, the current detection precision is improved.
Description
Technical Field
The embodiment of the invention relates to the control technology of food processing machines, in particular to a current detection method of a food processing machine.
Background
If the phenomenon that the heating pipe does not work or the motor does not work occurs in the food processor, the food processing effect can be seriously influenced, and the user experience is damaged. In order to effectively identify the abnormity of the heating pipe and the motor of the food processor, the most effective method at present is to detect the current of the heating pipe and the motor in real time, judge the working state of the machine according to the detected current and timely process the abnormity of the machine. And the current can be detected in real time, so that the abnormality of the machine can be identified, and when the current of the heating pipe or the motor is too large, the heating pipe and the motor can be protected in time, and the machine is prevented from being damaged. Therefore, the current detection of the food processor has important significance for protecting the normal work of the machine and improving the user experience. However, the current detection technology is limited by the current control circuit structure or sampling mode, and the problem of poor current detection precision occurs in the related current detection technology, so that the normal work of the food processor is influenced, and poor use experience is brought to users.
Disclosure of Invention
The embodiment of the invention provides a current detection method of a food processor, which can improve the current detection precision.
The embodiment of the invention adopts the following technical scheme:
a current detection method of a food processor comprises a load loop and a current sampling resistor, wherein the current sampling resistor is connected in series in the load loop and is used for detecting the current of the load loop; a load of a food processor comprising a heating device and a motor, the method comprising:
and determining a sampling period T in the current detection according to the least common multiple of all the control periods of the load, and determining the sampling times m in the current detection according to the control chopping angle of the load.
Optionally, the least common multiple of all control periods of the load refers to:
the least common multiple of all control periods in all control modes of the heating device and the motor.
Optionally, the heating device is controlled in a wave dropping control mode, and the motor is controlled in a chopping control mode;
determining the number of samples m in the current sensing according to the controlled chopping angle of the load comprises:
and determining the sampling times m according to the wave dropping control mode and the minimum control chopping angle β in the chopping control mode.
Optionally, T-12/f;
wherein f is the AC power frequency.
Optionally, the method further comprises:
before current detection, the control current of all loads is turned off, and the standby current I is sampled0；
After the current detection, the current I1 and the standby current I are detected0And calculating the final detection current I by a preset first relational expression.
Optionally, the first relation comprises: I-I1-I0。
Optionally, the method further comprises: according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutCarrying out correction;
according to the actual sampling voltage value U 'obtained after correction'outAnd calculating the detection current I.
Optionally, according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutThe correcting comprises the following steps: according to the sampling coefficient of the circuit board
Current sampling voltage value UoutAnd calculating an actual sampling voltage value U 'by using a preset second relational expression'out；
Wherein the second relation comprises:
optionally, the method further comprises:
passing a fixed calibration current I through a sampling resistor of a food processorCalibrationAnd sampling the calibration voltage U on the sampling resistorCalibration；
According to the calibration voltage UCalibrationAnd a preset theoretical voltage UTheory of the inventionCalculating sampling coefficient of circuit board
Optionally, the method further comprises: calculating circuit board sampling coefficient when circuit board leaves factory
And sampling coefficient of circuit board
And (6) carrying out correction.
The embodiment of the invention has the beneficial effects that:
1. the food processor comprises a load loop and a current sampling resistor, wherein the current sampling resistor is connected in series in the load loop and is used for detecting the current of the load loop; the load of the food processor comprises a heating device and a motor, and the current detection method of the food processor comprises the following steps: and determining a sampling period T in the current detection according to the least common multiple of all the control periods of the load, and determining the sampling times m in the current detection according to the control chopping angle of the load. The scheme of the embodiment solves the problems that in the related art, the current detection precision is poor due to the fact that the sampling voltage is asymmetric by using the silicon controlled control circuit, the current detection precision is poor due to the fact that the offset voltage of the operational amplifier circuit of the current sampling circuit is required to be poor, and the like, and improves the current detection precision.
2. The least common multiple of all control cycles of the load in the embodiment of the invention refers to: the least common multiple of all control periods in all control modes of the heating device and the motor. The whole power gear of the heating device in the food processor, the control period of the motor and the control period for controlling the conduction and the closing are set as integral multiples of the alternating current period, so as to ensure that the positive half-wave and the negative half-wave of the conduction half-wave and the closing half-wave in the control period are symmetrical. Therefore, the sampling period T in the scheme of the embodiment is set to be the least common multiple of all the control periods, and the on and off alternating-current half-waves of all the control gears in the sampling period can be ensured to be symmetrical, so that the current detection error caused by the fact that the sampling voltage U is not completely symmetrical is eliminated.
3. the heating device is controlled in a wave dropping control mode, the motor is controlled in a chopping control mode, the step of determining the sampling times m in current detection according to the control chopping angle of the load comprises the step of determining the sampling times m according to the minimum control chopping angle β in the wave dropping control mode and the chopping control mode, and the current can be accurately detected only when the current can be sampled even at the minimum chopping angle due to the fact that the minimum chopping angle β exists in the chopping control of the main control unit MCU, and in addition, the current detection can be more reliable due to the fact that the micro current in the motor chopping process is ensured.
4. The method of the embodiment of the invention also comprises the following steps: before current detection, the control current of all loads is turned off, and the standby current I is sampled0(ii) a After the current detection, the current I1 and the standby current I are detected0And calculating the final detection current I by a preset first relational expression. The scheme of the embodiment can eliminate the current detection error caused by the offset voltage of the operational amplifier circuit.
5. The method of the embodiment of the invention also comprises the following steps: according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutCarrying out correction; according to the actual sampling voltage value U 'obtained after correction'outAnd calculating the detection current I. The embodiment scheme can eliminate the current detection error caused by the copper foil resistance of the PCB wiring.
6. The method of the embodiment of the invention also comprises the following steps: calculating circuit board sampling coefficient when circuit board leaves factory
And sampling coefficient of circuit board
And (6) carrying out correction. In the scheme of the embodiment, the sampling coefficient of the circuit board is adopted
The method is characterized in that the method is stored in an EEPROM (electrically erasable and Programmable Read Only Memory), Only one calibration is needed when a circuit board leaves a factory, and when the method is used, the MCU directly reads data in the EEPROM, so that the production cost is lower, and the process is simpler.
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a flowchart of an embodiment of a method for eliminating errors caused by a sampling voltage U that is not completely symmetrical according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a conventional current detection hardware structure;
FIG. 3 is a flowchart of a method for eliminating an error caused by an offset voltage of an operational amplifier circuit according to an embodiment of the present invention;
FIG. 4 is a flowchart of an embodiment of a method for eliminating errors due to PCB copper foil resistance according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.
Example one
A current detection method of a food processor comprises a load loop and a current sampling resistor, wherein the current sampling resistor is connected in series in the load loop and is used for detecting the current of the load loop; the load of the food processor comprises a heating device and a motor, as shown in fig. 1, the method may comprise the step S11:
and S11, determining a sampling period T in the current detection according to the least common multiple of all the control periods of the load, and determining the sampling times m in the current detection according to the control chopping angle of the load.
In the embodiment of the present invention, the current detection using the sampling resistor is the lowest cost in the current detection of the food processor, and the most common method, the specific circuit topology is shown in fig. 2: the sampling resistor R samples the current I in the heating device or the motor circuit 1, the sampling voltage U is I × R, and the amplifying circuit 2 amplifies U to the sampling voltage Uoutthe signal is amplified by alpha, and then is input into a main control unit MCU (microprogrammed control Unit) according to a sampling voltage value UoutThe current I is calculated. However, the current detection scheme has the following problems:
1. because the heating device or the motor is controlled by the silicon controlled rectifier at present, and the external voltage VCC can cause the conduction chopping point of the silicon controlled rectifier to be advanced or delayed, the sampling voltage U is not a completely symmetrical alternating current waveform (namely, the positive half wave and the negative half wave are different), and the actual sampling voltage Uout＝VCC±α×I×R-ΔU1The current value detection is inaccurate due to the fact that a general sampling algorithm is used for calculating the sampling current.
2. The amplifying circuits in the correlated sampling circuits generally use operational amplifiersThe offset voltage of the amplifier can cause the increase of current detection error, which affects the current detection precision and the sampling voltage Uout＝VCC±α×I×R-ΔU1-ΔU2。
3. In the circuit board production process, there can be tiny difference between different circuit boards, especially printed circuit board PCB copper foil resistance can lead to sampling resistance to appear the deviation, and current detection sampling signal is very little, receives the influence of circuit board parameter very easily, leads to current detection error to increase, and sampling voltage Uout＝VCC±α×I×(R+ΔR)-ΔU1-ΔU2。
In the embodiment of the present invention, based on the above problems, it is necessary to improve the current detection method to solve the problem of poor detection accuracy caused by various factors.
In the embodiment of the present invention, it can be known from the above that the MCU detects the voltage Uout＝VCC±α×I×(R+ΔR)-ΔU1-ΔU2where α is the amplification factor, I is the current flowing through the sampling resistor, R is the resistance of the sampling resistor, Δ R is the resistance of the PCB copper foil, Δ U1Is the error, Δ U, caused by the sampling resistor sampling voltage U not being perfectly symmetrical2The error is caused by offset voltage of the operational amplifier circuit, and the delta R is caused by the resistance of the copper foil of the PCB.
In the embodiment of the present invention, regarding the error caused by the sampling resistor that the sampling voltage U is not completely symmetrical, the scheme in step S11 may be adopted, that is, the sampling period T in the current detection is determined according to the least common multiple of all the control periods of the load, and the sampling number m in the current detection is determined according to the control chopping angle of the load, so as to eliminate the current detection error caused by the sampling voltage U that is not completely symmetrical, that is, eliminate the sampling voltage Uout＝VCC±α×I×(R+ΔR)-ΔU1-ΔU2Error in Δ U1. The embodiment is explained below by means of specific examples.
In the embodiment of the invention, most of the existing food processing machines use the silicon controlled rectifier to control the heating device or the motor, and in order to meet the requirements of the soybean milk making performance of the soybean milk maker and avoid overlarge disturbance of harmonic current, a wave dropping control mode is adopted for a heavy current load (the heating device), and a chopping control mode is adopted for a small current load (the motor).
In the embodiment of the invention, the food processor (such as a soybean milk machine) uses a wave-dropping control mode for heating, and the heating gear and the control period respectively comprise:
full power P1 Control period T 11/f, the two alternating half-waves are all on (f is the alternating frequency);
3/4 power P2Control period T2Turning on 6 alternating-current half waves and turning off 2 alternating-current half waves, wherein the number of the alternating-current half waves is 1/f multiplied by 4;
2/3 power P3Control period T3Turning on 4 alternating-current half waves and turning off 2 alternating-current half waves, wherein the frequency is 1/f multiplied by 3;
1/2 power P4Control period T4Turning on 2 alternating-current half waves and turning off 2 alternating-current half waves, wherein the frequency is 1/f multiplied by 2;
1/3 power P5Control period T5Turning on 2 alternating-current half waves and turning off 4 alternating-current half waves, wherein the frequency is 1/f multiplied by 3;
1/4 power P6 Control period T 62 ac half-waves are switched on and 6 ac half-waves are switched off, 1/f × 4.
In an embodiment of the invention, the motor of the food processor (e.g., a soymilk maker) uses a chopper control scheme, e.g., to control the period T7and (4) chopping the two half-waves at 1/f, controlling the chopping angle beta at the minimum, and enabling the chopping points of the silicon controlled rectifier on the alternating-current half-waves to be integral multiples of β.
In the embodiment of the present invention, the maximum control period of the heating gear of the food processor is set to be 4 times of the period of the alternating current, so as to prevent the risk of voltage flicker caused by an excessively large control period. The heating power gear and the motor control period are controlled to be set as integral multiples of the alternating current period, so that the positive half-wave and the negative half-wave of the conducting half-wave and the closing half-wave in the control period are symmetrical. E.g. 1/2 power P4: turn on 2 and exchange the half-wave, close 2 and exchange the half-wave, turn on 1 positive half-wave of half-wave and 1 negative half-wave, close the half-wave and also 1 positive half-wave and 1 negative half-wave. So as to ensure positive in the control periodThe negative half-wave is symmetrical because the sampling voltage U of the sampling resistor is not a completely symmetrical alternating current waveform, and if the sampling waveform only has a positive half-wave or a negative half-wave, or the positive half-wave and the negative half-wave are asymmetrical, the current detection result is larger or smaller.
In the embodiment of the invention, the current detection period T is set to be the least common multiple of all control periods, so as to ensure that the on and off alternating current half-waves of all control gears in the sampling period are symmetrical, and eliminate the current detection error caused by the sampling voltage U which is not completely symmetrical, namely eliminate the sampling voltage Uout＝VCC±α×I×(R+ΔR)-ΔU1-ΔU2Error in Δ U1。
Optionally, the least common multiple of all control periods of the load refers to: the least common multiple of all control periods in all control modes of the heating device and the motor.
In the embodiment of the present invention, a method for calculating the least common multiple of all control cycles in the above control mode embodiment is described in detail as follows:
the current sampling period T is the load control period T1、T2、T3、T4、T5、T6、T7Of a least common multiple of, wherein T2＝1/f×4、T2＝1/f×4、T3＝1/f×3、T4＝1/f×2、T5＝1/f×3、T6＝1/f×4、T 71/f, i.e. T12 × 1/f. For example, when the frequency of the alternating current is 50HZ, the sampling period of the current detection
Single ac half-wave current sampling times
i.e. each ac half-wave is n times the minimum control chopping angle β, the current sensing sampling times m, n, 12, 2, 24n during the sampling period.
in the embodiment of the invention, for example, when the minimum chopping angle beta of the thyristor is 0.5ms, the sampling times of a single alternating half-wave current are counted
Next, the current detection sampling number m in the sampling period is 480 times.
alternatively, when the heating device is controlled in a wave dropping control mode and the motor is controlled in a chopping control mode, determining the sampling times m in the current detection according to the control chopping angle of the load may include determining the sampling times m according to the minimum control chopping angle β in the wave dropping control mode and the chopping control mode.
in the embodiment of the invention, the MCU chopping control has the minimum chopping angle β, the current detection times n of a single alternating-current half-wave need to ensure that the current can be sampled even if the minimum chopping angle is ensured, the current can also be accurately detected, and the micro current can also be reliably detected when the motor is chopped, so that n is equal to the integral multiple of the minimum chopping angle β contained in the single alternating-current half-wave, namely the minimum chopping angle β is the same as the integral multiple of the number of the minimum chopping angle β contained in the single alternating-
Then the number of samples within the current sensing period T
Optionally, T-12/f;
wherein f is the AC power frequency.
In the embodiment of the present invention, based on the foregoing, the current detection period T may be 12/f, or may be an integral multiple of 12/f; the current detection times m can be selected
Can also select
Integer multiples of.
Example two
The embodiment provides an embodiment scheme for eliminating errors caused by offset voltage of the operational amplifier circuit.
Optionally, as shown in fig. 3, the method may further include S21-S22:
s21, before current detection, the control current of all loads is closed, and the standby current I is sampled0；
S22, after detecting the current, according to the current I1 and the standby current I0And calculating the final detection current I by a preset first relational expression.
Optionally, the first relation comprises: I-I1-I0。
In the embodiment of the invention, the scheme of the embodiment is substantially as follows: before sampling the load current I, sampling the reference current I0(i.e., the standby current I described above0) And calculating the final detection current I according to the reference current.
In the embodiment of the invention, the current detection precision can be improved and the error delta U caused by the sampling resistor sampling voltage U not being completely symmetrical in the current detection can be eliminated through the sampling period T and the sampling times m1. By sampling the reference current I0Based on the reference current I0Calculating the sampling current I ═ I1-I0Namely, the error delta U caused by the offset voltage of the operational amplifier circuit can be eliminated2。
In the embodiment of the present invention, since the load current I is 0 when the load is completely turned off, the reference current sample value U is0＝VCC-ΔU2＝I0*R0And the offset voltage of the operational amplifier circuit is more stable, so when the load works, the load current sampling value U is sampledoutSubtracting the reference current sample value U0Then there are: u shapeout-U0＝[VCC±α×I×(R+ΔR)-ΔU2]-[VCC-ΔU2]the sampling result of the final MCU is only related to the sampling resistor R, the load current I and the amplification factor α, and the error delta U caused by the offset voltage of the operational amplifier circuit is eliminated2。
EXAMPLE III
This example presents an example solution to eliminate errors due to PCB copper foil resistance.
Optionally, as shown in fig. 4, the method may further include S31-S32:
s31, sampling coefficient according to circuit board
For the current sampling voltage value UoutCarrying out correction;
s32, obtaining an actual sampling voltage value U 'according to the correction'outAnd calculating the detection current I.
In the embodiment of the invention, the technical scheme of the embodiment can improve the current detection precision by designing the sampling period T and the sampling times m, and eliminate the error delta U caused by the fact that the sampling voltage U of the sampling resistor is not completely symmetrical1(ii) a By sampling the reference current and calculating the sampling current according to the reference current, the error delta U caused by the offset voltage of the operational amplifier circuit can be eliminated2And finally the sampling value U of the MCUoutto eliminate the current detection error Δ R caused by the copper foil resistance of the PCB trace, the technical solution of the present embodiment uses the circuit board sampling coefficient
Calibrating the sampling value according to the sampling coefficient
And the load current is calculated, so that the current detection precision is improved.
Optionally, the method further comprises:
passing a fixed calibration current I through a sampling resistor of a food processorCalibrationAnd sampling the calibration voltage U on the sampling resistorCalibration；
According to the calibration voltage UCalibrationAnd a preset theoretical voltage UTheory of the inventionCalculating sampling coefficient of circuit board
In the embodiment of the present invention, U is known from the aboveoutwhen a fixed calibration current I is passed through the sampling resistor circuit, +/-x (R + Δ R)CalibrationTheory of time, MCUSampling value UTheory of the invention＝±α×ICalibrationX R, actual sampling value UCalibration＝±α×ICalibrationX (R + Δ R), coefficient
Optionally, according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutThe correcting comprises the following steps: according to the sampling coefficient of the circuit board
Current sampling voltage value UoutAnd calculating an actual sampling voltage value U 'by using a preset second relational expression'out；
Wherein the second relation comprises:
in the embodiment of the invention, when the MCU calculates the sampling current, the sampling value U is usedoutDivided by the sampling coefficient of the circuit board
I.e. the actual sampled value
Recalculating load current
And current detection errors caused by the resistance of the copper foil of the PCB are eliminated.
Optionally, the method further comprises: calculating circuit board sampling coefficient when circuit board leaves factory
And sampling coefficient of circuit board
And (6) carrying out correction.
In the embodiment of the invention, the sampling coefficient of the circuit board is calculated when the circuit board leaves the factory
Sampling coefficient of circuit board
The sampling coefficient of the circuit board can be only stored in EEPROM when the circuit board leaves factory
The calibration is carried out once, and the MCU directly reads the data in the EEPROM during use, so that the production cost is lower, and the process is simpler. In other embodiments, to further ensure the sampling coefficient of the circuit board
The accuracy of the method can also calculate the sampling coefficient of the circuit board at regular time
And utilizes the latest sampling coefficient of the circuit board
Correcting the sampling data in the current detection, and calculating the sampling coefficient of the circuit board at each timing
In time, the sampling coefficient of the original circuit board stored in the EEPROM can be calculated according to the factory
Sampling coefficient of newly calculated circuit board
Make correctionsAnd the current detection accuracy is further ensured.
The embodiment of the invention has the beneficial effects that:
1. the food processor comprises a load loop and a current sampling resistor, wherein the current sampling resistor is connected in series in the load loop and is used for detecting the current of the load loop; the load of the food processor comprises a heating device and a motor, and the current detection method of the food processor comprises the following steps: and determining a sampling period T in the current detection according to the least common multiple of all the control periods of the load, and determining the sampling times m in the current detection according to the control chopping angle of the load. The scheme of the embodiment solves the problems that in the related art, the current detection precision is poor due to the fact that the sampling voltage is asymmetric by using the silicon controlled control circuit, the current detection precision is poor due to the fact that the offset voltage of the operational amplifier circuit of the current sampling circuit is required to be poor, and the like, and improves the current detection precision.
2. The least common multiple of all control cycles of the load in the embodiment of the invention refers to: the least common multiple of all control periods in all control modes of the heating device and the motor. The whole power gear of the heating device in the food processor, the control period of the motor and the control period for controlling the conduction and the closing are set as integral multiples of the alternating current period, so as to ensure that the positive half-wave and the negative half-wave of the conduction half-wave and the closing half-wave in the control period are symmetrical. Therefore, the sampling period T in the scheme of the embodiment is set to be the least common multiple of all the control periods, and the on and off alternating-current half-waves of all the control gears in the sampling period can be ensured to be symmetrical, so that the current detection error caused by the fact that the sampling voltage U is not completely symmetrical is eliminated.
3. the heating device is controlled in a wave dropping control mode, the motor is controlled in a chopping control mode, the step of determining the sampling times m in current detection according to the control chopping angle of the load comprises the step of determining the sampling times m according to the minimum control chopping angle β in the wave dropping control mode and the chopping control mode, and the current can be accurately detected only when the current can be sampled even at the minimum chopping angle due to the fact that the minimum chopping angle β exists in the chopping control of the main control unit MCU, and in addition, the current detection can be more reliable due to the fact that the micro current in the motor chopping process is ensured.
4. The method of the embodiment of the invention also comprises the following steps: before current detection, the control current of all loads is turned off, and the standby current I is sampled0(ii) a After the current detection, the current I1 and the standby current I are detected0And calculating the final detection current I by a preset first relational expression. The scheme of the embodiment can eliminate the current detection error caused by the offset voltage of the operational amplifier circuit.
5. The method of the embodiment of the invention also comprises the following steps: according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutCarrying out correction; according to the actual sampling voltage value U 'obtained after correction'outAnd calculating the detection current I. The embodiment scheme can eliminate the current detection error caused by the copper foil resistance of the PCB wiring.
6. The method of the embodiment of the invention also comprises the following steps: calculating circuit board sampling coefficient when circuit board leaves factory
And sampling coefficient of circuit board
And (6) carrying out correction. In the scheme of the embodiment, the sampling coefficient of the circuit board is adopted
The method is characterized in that the method is stored in an EEPROM (electrically erasable and Programmable Read Only Memory), Only one calibration is needed when a circuit board leaves a factory, and when the method is used, the MCU directly reads data in the EEPROM, so that the production cost is lower, and the process is simpler.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A current detection method of a food processor comprises a load loop and a current sampling resistor, wherein the current sampling resistor is connected in series in the load loop and is used for carrying out current detection on the load loop; the load of the food processor comprises a heating device and a motor, characterized in that the method comprises: the heating device is controlled in a wave dropping control mode, and the motor is controlled in a chopping control mode;
determining a sampling period T in the current detection according to the least common multiple of all control periods of the load, determining the sampling times m in the current detection according to the control chopping angle of the load, determining the sampling times m according to the minimum control chopping angle β in the chopping control mode and the chopping control mode, wherein the sampling times m are determined according to the minimum control chopping angle β in the chopping control mode and the minimum control chopping angle T in the chopping control mode
Wherein, f is the AC power frequency, and T is 12/f.
2. The method of claim 1, wherein the least common multiple of all control cycles of the load is:
the least common multiple of all control periods in all control modes of the heating device and the motor.
3. The method of claim 1, further comprising:
before current detection, the control current of all loads is turned off, and the standby current I is sampled0；
After the current detection is carried out, the standby current I is detected according to the current I10And calculating the final detection current I by a preset first relation, wherein the first relation comprises: I-I1-I0。
4. The method of claim 1, further comprising:
according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutCarrying out correction;
according to the actual sampling voltage value U 'obtained after correction'outCalculating the detection current I according to the sampling coefficient of the circuit board
For the current sampling voltage value UoutThe correcting comprises the following steps: according to the sampling coefficient of the circuit board
The current sampling voltage value UoutAnd calculating the actual sampling voltage value U 'by using a preset second relational expression'out；
Wherein the second relation comprises:
5. the method of claim 4, further comprising:
passing a fixed calibration current I through a sampling resistor of the food processor in advanceCalibrationAnd sampling the calibration voltage U on the sampling resistorCalibration；
According to the calibration voltage UCalibrationAnd presetTheoretical voltage UTheory of the inventionCalculating the sampling coefficient of the circuit board
6. The method of claim 5, further comprising: calculating the sampling coefficient of the circuit board when the circuit board leaves the factory
And sampling coefficient of the circuit board
And (6) carrying out correction.
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| CN114631745A (en) * | 2020-12-16 | 2022-06-17 | 九阳股份有限公司 | Food processing machine |
| CN113687130A (en) * | 2021-09-13 | 2021-11-23 | 阳光电源股份有限公司 | Voltage measuring method and application device thereof |
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