CN210954156U

CN210954156U - Current detection circuit and household equipment

Info

Publication number: CN210954156U
Application number: CN201921302432.2U
Authority: CN
Inventors: 不公告发明人
Original assignee: Ningbo Tuobang Intelligent Control Co ltd
Current assignee: Ningbo Tuobang Intelligent Control Co ltd; Shenzhen Topband Co Ltd
Priority date: 2019-08-12
Filing date: 2019-08-12
Publication date: 2020-07-07
Anticipated expiration: 2029-08-12

Abstract

The utility model is suitable for an electronic circuit technical field provides a current detection circuit and domestic equipment, and this circuit is used for carrying out chopper current detection to AC motor, include: the power supply module is connected with the alternating current and used for converting the input alternating current into direct current and outputting the direct current; the zero-crossing detection module is used for detecting a zero-crossing signal of the alternating current and outputting the zero-crossing signal to the controller; the chopping driving module is used for controlling the working state of the alternating current motor according to the control signal output by the controller; the current detection module is used for collecting and detecting the current of the alternating current motor when the alternating current motor works and outputting the current to the controller; and the controller is used for outputting a control signal to the chopping driving module after preset time according to the zero-crossing signal detected by the zero-crossing detection module so as to enable the chopping driving module to control the driving alternating current motor to work and obtain the current collected by the current detection module in real time. The utility model provides a current inaccurate problem of measuring current.

Description

Current detection circuit and household equipment

Technical Field

The utility model belongs to the technical field of the electronic circuit, especially, relate to a current detection circuit and domestic equipment.

Background

Along with the development of electronic technology, more and more electronic products begin to be generally used by users, wherein household equipment with an alternating current motor, such as a blender and a wall breaking machine, often needs to detect the effective current value of the alternating current motor during working so as to avoid the problem of damage to the alternating current motor caused by the effective current value being higher than a current threshold value.

The current detection scheme of the alternating current motor commonly used at present is to convert alternating current into alternating voltage by using a precision resistor with small resistance value, and calculate the effective value of the current by detecting the peak value of the alternating voltage through a 51 single chip microcomputer during working.

However, the current 51 single chip microcomputer cannot always acquire a current value to calculate a current effective value, and only can calculate the current value by detecting the peak value of the alternating voltage, and under the condition of silicon controlled rectifier chopping, the same current can have different peak voltages under different chopping widths, so that the current calculation is inaccurate, meanwhile, the interference of the alternating current motor in working is very large, the interference of the alternating current motor in the peak of the voltage is large, the current acquisition is also inaccurate, and the current acquisition is inaccurate, so that the current acquisition needs to be performed for multiple times, and the acquisition time is long.

SUMMERY OF THE UTILITY MODEL

An object of the embodiment of the utility model is to provide a current detection circuit and domestic equipment aims at solving the not accurate problem of current detection current.

The embodiment of the utility model provides a realize like this, a current detection circuit for carry out chopper current detection to AC motor, the circuit includes:

the power supply module is connected with the alternating current and used for converting the input alternating current into direct current and outputting the direct current, a first end of the alternating current is connected with one end of the alternating current motor, and a second end of the alternating current is connected with the ground of the power supply module;

the zero-crossing detection module is respectively connected with the first end of the alternating current, the power supply module and the controller, and is used for detecting a zero-crossing signal of the alternating current and outputting the zero-crossing signal to the controller;

the chopping driving module is respectively connected with the other end of the alternating current motor, the power supply module and the controller and is used for controlling the working state of the alternating current motor according to a control signal output by the controller;

the current detection module is respectively connected with the second end of the alternating current, the power supply module, the chopping drive module and the controller, and is used for collecting and detecting the current of the alternating current motor when the alternating current motor works and outputting the current to the controller;

and the controller is respectively connected with the zero-crossing detection module, the chopping drive module, the power supply module and the current detection module, and is used for outputting the control signal to the chopping drive module after preset time according to the zero-crossing signal detected by the zero-crossing detection module so as to enable the chopping drive module to control and drive the alternating current motor to work and obtain the current collected by the current detection module in real time.

Further, the zero crossing detection module comprises:

the voltage dividing unit is connected with the first end of the alternating current and used for dividing the voltage of the alternating current;

and the first switch unit is respectively connected with the voltage division unit, the controller and the power module and is used for performing switch control according to the phase state of the alternating current so as to output different levels to the controller.

Still further, the chopper driver module includes:

the second switch unit is connected with the other end of the alternating current motor and is used for controlling the working state of the alternating current motor;

and the third switching unit is respectively connected with the second switching unit, the power supply module and the controller and is used for controlling the second switching unit to be switched on and off according to the control signal output by the controller.

Further, the current detection module includes:

the sampling unit is respectively connected with the second end of the alternating current and the chopping driving module and is used for collecting and detecting the current of the alternating current motor;

the power module is connected with the two ends of the sampling unit and the controller respectively, and is used for amplifying the current collected and detected by the sampling unit and outputting the current to the equidirectional amplification unit of the controller.

Furthermore, the voltage dividing unit comprises a first voltage dividing resistor and a second voltage dividing resistor which are sequentially connected with a first end of the alternating current, and the other end of the second voltage dividing resistor is connected with the first switch unit; the first switch unit is a first triode, the base of the first triode is connected with the voltage dividing unit, the emitting electrode of the first triode is grounded, and the collecting electrode of the first triode is connected with the controller and the power output end of the power module respectively.

Further, the zero crossing detection module further comprises:

the first filtering unit is connected with the voltage dividing unit and is used for filtering a first end of the alternating current;

the protection unit is connected with the voltage division unit and is used for carrying out reverse protection on reverse voltage input by the first end of the alternating current;

and the second filtering unit is connected between the first switching unit and the controller and is used for filtering the zero-crossing signal output to the controller.

Furthermore, the first filtering unit is a first capacitor, one end of the first capacitor is connected to the voltage dividing unit and the first switch unit, and the other end of the first capacitor is grounded; the protection unit is a first diode, the anode of the first diode is grounded, and the cathode of the first diode is respectively connected with the voltage division unit and the first switch unit; the second filtering unit comprises a first resistor and a second capacitor, one end of the first resistor is connected with a collector of the first triode, the other end of the first resistor is respectively connected with one end of the second capacitor and the controller, and the other end of the second capacitor is grounded; the collector of the first triode is also connected with one end of a first pull-up resistor, and the other end of the first pull-up resistor is connected with the power output end of the power supply module.

Furthermore, the second switch unit is a silicon controlled rectifier, main electrodes at two ends of the silicon controlled rectifier are respectively connected with the other end of the alternating current motor and the current detection module, a control electrode of the silicon controlled rectifier is connected with the third switch unit, the third switch unit is a second triode, a base electrode of the second triode is connected with the controller, a collector electrode of the second triode is respectively connected with the second switch unit and a power output end of the power module, and an emitting electrode of the second triode is grounded.

Still further, the chopping drive module further includes: connect gradually in the control pole of silicon controlled rectifier with first current-limiting resistor and coupling capacitance between the collecting electrode of second triode, connect in the collecting electrode of second triode with second pull-up resistance between the power output end of power module, and with discharge resistance, third electric capacity and the second current-limiting resistor that the base of second triode is connected, discharge resistance with the other end of third electric capacity all grounds, the other end of second current-limiting resistor with the controller is connected.

Furthermore, the sampling unit is a sampling resistor, the equidirectional amplification unit comprises an operational amplifier, a second resistor connected to the reverse input end of the operational amplifier, a third resistor connected to the equidirectional input end of the operational amplifier, and a fourth resistor connected between the reverse input end and the output end of the operational amplifier, the other end of the second resistor is connected with one end of the sampling resistor connected with the second end of the alternating current, the other end of the second resistor is connected with one end of the sampling resistor connected with the chopping driving module, the positive power supply of the operational amplifier is connected with the power supply output end of the power supply module, and the negative power supply of the operational amplifier is grounded.

Further, the current detection module further includes: the operational amplifier comprises a fourth capacitor and a clamping diode which are connected with the same-direction input end of the operational amplifier, a fifth capacitor which is connected with the positive power supply of the operational amplifier, and a fifth resistor and a sixth capacitor which are sequentially connected with the output end of the operational amplifier, wherein the other ends of the fourth capacitor, the fifth capacitor and the sixth capacitor are grounded, the negative electrode of the clamping diode is connected with the same-direction input end of the operational amplifier, the positive electrode of the clamping diode is grounded, and the other end of the fifth resistor is connected with the controller.

An embodiment of the utility model provides a still provides a household appliance, be equipped with AC motor on the household appliance and with what AC motor connected as above-mentioned current detection circuit, current detection circuit is used for right AC motor carries out the detection of chopper current.

The embodiment of the utility model provides a current detection circuit, detect the zero cross signal of alternating current through zero cross detection module, and send to the controller when zero cross detection module detects the zero cross signal of alternating current, the controller outputs control signal to chopping drive module after the preset time of zero cross signal delay according to zero cross detection module detection this moment, so that chopping drive module control drives the work of alternating current motor, through the control to the length of the preset time of controller delay this moment, make the pulse width of the chopping current controllable, furthermore, when alternating current motor is worked, its current detection module detects the electric current of alternating current motor during working in real time, and send the electric current information detected in real time to the controller, make the controller can calculate in a control cycle according to the electric current detected in real time by current detection module and obtain the electric current virtual value of alternating current motor during chopping work, the current effective value of the chopping current can be calculated quickly, effectively and accurately, and the problem that the current is not accurate is solved.

Drawings

Fig. 1 is a schematic block diagram of a current detection circuit according to an embodiment of the present invention;

fig. 2 is a schematic circuit diagram of a current detection circuit according to another embodiment of the present invention;

fig. 3 is a schematic circuit diagram of a current detection circuit according to another embodiment of the present invention;

fig. 4 is a flowchart of a current detection method 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 clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example one

Please refer to fig. 1, which is a schematic block diagram of a current detection circuit according to an embodiment of the present invention, the current detection circuit is used for detecting a chopping current of an ac motor, and the circuit includes:

a power module 110 connected to the alternating current 100 for converting the input alternating current 100 into direct current and outputting the direct current, wherein a first end AC1 of the alternating current 100 is connected to one end M1 of the alternating current motor 120, and a second end AC2 of the alternating current 100 is connected to the ground GND of the power module 110;

the zero-crossing detection module 140 is respectively connected with the first end AC1 of the alternating current 100, the power module 110 and the controller 130, and is used for detecting a zero-crossing signal of the alternating current 100 and outputting the zero-crossing signal to the controller 130;

a chopping driving module 150 respectively connected to the other end M2 of the ac motor 120, the power module 110, and the controller 130, and configured to control the operating state of the ac motor 120 according to a control signal output by the controller 130;

a current detection module 160 connected to the second end AC2 of the AC power 100, the power supply module 110, the chopper driving module 150, and the controller 130, respectively, and configured to collect and detect a current of the AC motor 120 when the AC motor 120 is in operation, and output the current to the controller 130;

and a controller 130, which is respectively connected to the zero-crossing detection module 140, the chopping drive module 150, and the current detection module 160, and configured to output a control signal to the chopping drive module 150 after a preset time according to the zero-crossing signal detected by the zero-crossing detection module 140, so that the chopping drive module 150 controls and drives the ac motor 120 to operate, and obtains a current collected by the current detection module 160 in real time.

In an embodiment of the present invention, it is specific, this power module 110 is an AD-DC power module 110, a voltage output is carried out to alternating current 100 conversion that is used for inputting, it is specific, the input of its power module 110 is connected with zero line end ACN and live wire end ACL of alternating current 100 respectively, the output of its power module 110 includes a power output VCC and a grounding terminal GND, wherein power output VCC is used for providing zero cross detection module 140, chopping drive module 150, current detection module 160, and the required direct current of controller 130 during operation, it is specific, this power output VCC exports 3.3V or 5V direct current, specifically can set up according to the actual use demand, do not limit here. Specifically, in this embodiment, the first end AC1 is a live line end ACL, and the second end AC2 is a zero line end ACN, that is, the zero line end ACN of the alternating current 100 is connected to the ground end GND, so that the zero line end ACN maintains a zero potential, and at this time, the live line end ACL of the alternating current 100 maintains a forward and reverse level change with respect to the zero line end ACN. Further, the live line end ACL of the alternating current 100 is further connected to one end M1 of the alternating current motor 120, and it can be understood that, in other embodiments of the present invention, the first end AC1 of the alternating current 100 may also be the neutral line end ACN, and the second end AC2 of the alternating current 100 may also be the live line end ACL, which are set according to actual use requirements, and are not limited herein.

The utility model discloses an embodiment, this Zero cross detection module 140 respectively with the first end AC1 of alternating current 100, power module 110's power output VCC, and the first input Zero of controller 130 is connected, its Zero cross detection module 140 is used for carrying out real-time detection to alternating current 100 according to the power supply that power output VCC provided, and when detecting alternating current 100's the signal that overflows, output this Zero cross signal to the first input Zero of controller 130, make controller 130 can determine the Zero cross time point of alternating current 100 according to the information that Zero cross detection module 140 detected, and control alternating current motor 120 work after alternating current 100 crosses the Zero.

In an embodiment of the present invention, the chopping driver module 150 is respectively connected to the other end M2 of the ac motor 120, the power output terminal VCC of the power module 110, and the first output terminal SCR of the controller 130, wherein the chopping driver module 150 is configured to control the operation of the chopping driver module 150 according to the control signal output by the first output terminal SCR of the controller 130, so that when the chopping driver module 150 is turned on, both ends of the ac motor 120 are turned on, thereby controlling the operation of the ac motor 120, and therefore, after the controller 130 obtains the zero-crossing signal detected by the zero-crossing detection module 140, the controller 130 outputs the control signal to the chopping driver module 150 after a preset time, so that the chopping driver module 150 controls the operation of the ac motor 120, and at this time, the controller 130 is set by the length of the preset time, so that the operation time of the ac motor 120 can be set, that is, the chopped pulse width, that is, for example, the period of the sine wave is 20ms when the ac power 100 operates, the first half period of the upper half wave is 10ms, when the controller 130 needs to chop the waveform of the first half wave, the controller 130 sends a control signal to the chopping drive module 150 after delaying 5ms when acquiring the zero-crossing signal of the upper half wave in the sine wave detected by the zero-crossing detection module 140, so that the ac motor 120 does not operate during the first 5ms of the upper half wave of the control cycle, and the ac motor 120 operates during the last 5ms of the upper half wave of the control cycle, and at this time, the controller 130 controls the chopped pulse width to control the rotation speed of the ac motor 120.

In an embodiment of the present invention, the current detecting module 160 is respectively connected to the zero line terminal ACN of the alternating current 100, the power output terminal VCC of the power module 110, the chopping driving module 150, and the second input terminal DMA of the controller 130, and the current detecting module 160 is used for collecting the current of the alternating current motor 120 and outputting the detected current to the second input terminal DMA of the controller 130 when the chopping driving module 150 drives the alternating current motor 120 to operate. The current detection module 160 is disposed between the zero line end ACN of the alternating current 100 and the chopping drive module 150, and when the chopping drive module 150 does not drive the other end M2 of the alternating current motor 120 to be conducted, the two ends of the alternating current motor 120 are not conducted, so that the alternating current motor 120 is in a non-working state; when the chopping drive module 150 drives the other end M2 of the ac motor 120 to be turned on, at this time, the other end M2 of the ac motor 120 is communicated with the neutral line terminal ACN of the ac motor 100 through the current detection module 160, and at this time, when the ac motor 100 is in the forward phase, the current flows from the live line terminal ACL through the one end M1 of the ac motor 120, and the other end M2 of the ac motor 120 flows to the neutral line terminal ACN of the ac motor 100, so that the two ends of the ac motor 120 are communicated, and therefore, the operation of the ac motor 120 can be controlled, and the operating current of the ac motor 120 during operation flows from the chopping drive module 150 to the current detection module 160, and therefore, the current detection module 160 can detect the current of the ac motor 120 during.

In an embodiment of the present invention, the controller 130 is respectively connected to the power output VCC of the zero-crossing detection module 140, the chopping driving module 150, the current detection module 160, and the power module 110, specifically, the controller 130 is an MCU, specifically, an STM32 microcontroller. After acquiring the Zero-crossing signal detected by the Zero-crossing detection module 140, the first input terminal Zero of the controller 130 outputs a control signal to the chopping drive module 150 through the first output terminal SCR within a preset time, so that the chopping drive module 150 drives the alternating current motor 120 to work, and the second input terminal DMA acquires the current acquired by the current detection module 160 in real time when the alternating current motor 120 works, and determines the effective current of the chopping current when the alternating current motor 120 works according to the current acquired in real time. It should be noted that the DMA module is disposed inside the controller 130, and the DMA module at the second input end of the controller 130 is connected to the DMA module inside the controller 130, so that the currents detected in real time by the current detection module 160 are all sent to the DMA module inside the controller for collection, and the DMA module in the controller 130 independently collects the currents in the current collection process, and can exchange data with an external module device at a high speed without being controlled by the controller 130, so that the resource of the controller 130 is not occupied.

In the embodiment, the zero-crossing detection module detects a zero-crossing signal of the alternating current and sends the zero-crossing signal to the controller when the zero-crossing detection module detects the zero-crossing signal of the alternating current, at the moment, the controller delays for a preset time according to the zero-crossing signal detected by the zero-crossing detection module and then outputs a control signal to the chopping drive module so that the chopping drive module controls the operation of driving the alternating current motor, at the moment, the pulse width of the chopping current can be controlled by controlling the length of the preset time delayed by the controller, further, when the alternating current motor operates, the current detection module detects the current of the alternating current motor in real time and sends the current information detected in real time to the controller, so that the controller can calculate the current effective value of the alternating current motor in chopping operation in a control period according to the current detected in real time by the current detection module, the current effective value of the chopping current can be calculated quickly, effectively and accurately, and the problem that the current is not accurate is solved.

Example two

Please refer to fig. 2, which is a schematic block diagram of a current detection circuit according to a second embodiment of the present invention, the second embodiment has a structure substantially the same as that of the first embodiment, for a brief description, the embodiments of the present invention do not refer to the corresponding contents in the first embodiment, and the difference is that in this embodiment, the zero-crossing detection module 140 includes:

a voltage dividing unit 141 connected to the first end AC1 of the alternating current 100 for dividing the voltage of the alternating current 100;

the first switch unit 142 is respectively connected to the voltage divider 141, the controller 130, and the power module 110, and configured to perform switching control according to a phase state of the alternating current 100 to output different levels to the controller 130.

Further, in an embodiment of the present invention, the chopping drive module 150 includes:

a second switching unit 151 connected to the other end M2 of the ac motor 120, for controlling the operating state of the ac motor 120;

and a third switching unit 152 respectively connected to the second switching unit 151, the power module 110, and the controller 130, and configured to control the second switching unit 151 to switch according to a control signal output by the controller 130.

Further, in an embodiment of the present invention, the current detection module 160 includes:

the sampling unit 161 is respectively connected with the second end AC2 of the alternating current 100 and the second switching unit 151 in the chopping drive module 150, and is used for collecting and detecting the current of the alternating current motor 120;

and the two ends of the sampling unit 161, the power module 110 and the controller 130 are respectively connected to amplify the current collected and detected by the sampling unit 161 and output the amplified current to the equidirectional amplifying unit 162 of the controller 130.

In an embodiment of the present invention, the voltage dividing unit 141 is used for dividing the voltage of the alternating current 100, so that most of the voltage drop of the alternating current 100 is loaded on the voltage dividing unit 141, and the smaller voltage and current is input into the first switch unit 142, and further, the first switch unit 142 is used for performing corresponding switch control according to the phase state of the alternating current 100, so as to output different levels to the controller 130. In this embodiment, specifically, when the alternating current 100 is in the forward phase (i.e. in the upper half wave of the sine wave), the first switch unit 142 is in the conducting state, and outputs a low level to the first input terminal Zero of the controller 130; when the alternating current 100 is in the reverse phase (i.e., in the lower half wave of the sine wave), the first switching unit 142 thereof is in the off state, and outputs a high level to the first input terminal Zero of the controller 130. Therefore, when the controller 130 acquires that the level input by the zero-crossing detection module 140 changes from the high level to the low level, it may be determined that the alternating current 100 is a zero-crossing point at which the reverse phase is changed into the forward phase; when the controller 130 acquires that the level input by the zero-crossing detection module 140 changes from low level to high level, it may determine that the alternating current 100 is a zero-crossing point at which the positive phase changes into the negative phase. It is understood that in other embodiments of the present invention, the first switch unit 142 may also output other different levels to the controller 130 according to the phase change of the alternating current 100, which is set according to the actual use requirement, and is not limited herein.

In an embodiment of the present invention, the second switch unit 151 is connected to the other end M2 of the ac motor 120, and is configured to control the on/off of the other end M2 of the ac motor 120, so that the operating state of the ac motor 120 can be controlled; the third switching unit 152 is respectively connected to the first output terminal SCR of the controller 130 and the second switching unit 151, and is configured to correspondingly control the switching of the second switching unit 151 according to a control signal output from the first output terminal SCR of the controller 130. Specifically, in this embodiment, when the controller 130 controls the first output terminal SCR to output a high level, the third switching unit 152 correspondingly controls the second switching unit 151 to be turned on; when the controller 130 controls the first output terminal SCR to output a low level, the third switching unit 152 thereof correspondingly controls the second switching unit 151 to turn off. It is understood that in other embodiments of the present invention, the third switching unit 152 may also be correspondingly controlled by other control signals output by the first output end SCR of the controller 130, so as to control the on or off of the second switching unit 151, which is set according to actual use requirements, and is not limited herein.

In an embodiment of the present invention, the sampling unit 161 is used for collecting the current of the ac motor 120, wherein when the chopping drive module 150 drives the ac motor 120 to work, the current of the ac motor 120 during working flows through the sampling unit 161, and the sampling unit 161 samples the current to collect and detect the current flowing through the ac motor 120; the equidirectional amplification unit 162 is configured to amplify the current collected and detected by the sampling unit 161 in the same direction, and output the current amplified by the amplification factor to the second input end DMA of the controller 130, so that the controller 130 can obtain the current detected by the current detection module 160 in real time, and calculate an effective current value of the chopping current according to the collected and detected current.

EXAMPLE III

The third embodiment of the present invention provides a current detection circuit whose structure is the same as that of the second embodiment, and for brief description, the embodiments of the present invention do not refer to the corresponding content in the first embodiment, and the difference lies in referring to fig. 3, in this embodiment, the zero-crossing detection module 140 further includes:

a first filtering unit 143 connected to the voltage dividing unit 141 for filtering the first terminal AC1 of the alternating current 100;

a protection unit 144 connected to the voltage dividing unit 141 for performing reverse protection on a reverse voltage input from the first terminal AC1 of the alternating current 100;

and a second filtering unit 145 connected between the first switching unit 142 and the controller 130, for filtering the zero-crossing signal output to the controller 130.

Further, in one embodiment of the present invention, the voltage dividing unit 141 includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2 sequentially connected to the first terminal AC1 of the alternating current 100, and the other end of the second voltage dividing resistor R2 is connected to the first switch unit 142; the first switch unit 142 is a first transistor Q1, a base B of the first transistor Q1 is connected to the voltage dividing unit 141, an emitter E of the first transistor Q1 is grounded GND, and a collector C of the first transistor Q1 is connected to the controller 130 and the power output terminal VCC of the power module 110, respectively.

Furthermore, in an embodiment of the present invention, the first filtering unit 143 is a first capacitor C1, one end of the first capacitor C1 is connected to the voltage dividing unit 141 and the first switching unit 142, and the other end of the first capacitor C1 is grounded to GND; the protection unit 144 is a first diode D1, an anode of the first diode D1 is grounded GND, and a cathode of the first diode D1 is connected to the voltage division unit 141 and the first switch unit 142 respectively; the second filtering unit 145 comprises a first resistor R3 and a second capacitor C2, one end of the first resistor R3 is connected to the collector C of the first triode Q1, the other end of the first resistor R3 is connected to one end of the second capacitor C2 and the controller 130, and the other end of the second capacitor C2 is grounded to GND; the collector C of the first transistor Q1 is further connected to one end of a first pull-up resistor R4, and the other end of the first pull-up resistor R4 is connected to the power output terminal VCC of the power module 110.

Furthermore, in an embodiment of the present invention, the second switch unit 151 is a silicon controlled rectifier SR1, two main electrodes of the silicon controlled rectifier SR1 are respectively connected to the other end M2 of the ac motor 120 and the current detection module 160, a control electrode G of the silicon controlled rectifier SR1 is connected to the third switch unit 152, the third switch unit 152 is a second triode Q2, a base B of the second triode Q2 is connected to the controller 130, a collector C of the second triode Q2 is respectively connected to the second switch unit 151 and the power output terminal VCC of the power module 110, and an emitter E of the second triode Q2 is grounded GND.

Further, in an embodiment of the present invention, the chopping drive module 150 further includes: the first current limiting resistor R5 and the coupling capacitor C3 are connected between the control electrode G of the controllable silicon SR1 and the collector C of the second triode Q2 in sequence, the second pull-up resistor R6 is connected between the collector C of the second triode Q2 and the power output end VCC of the power module 110, the discharging resistor R7, the third capacitor C4 and the second current limiting resistor R8 are connected with the base B of the second triode Q2, the other ends of the discharging resistor R7 and the third capacitor C4 are both grounded GND, and the other end of the second current limiting resistor R8 is connected with the controller 130.

Furthermore, in an embodiment of the present invention, the sampling unit 161 is a sampling resistor R9, the equidirectional amplifying unit 162 includes an operational amplifier U1A, a second resistor R10 connected to the inverting input terminal of the operational amplifier U1A, a third resistor R11 connected to the equidirectional input terminal of the operational amplifier U1A, and a fourth resistor R12 connected between the inverting input terminal and the output terminal of the operational amplifier U1A, the other end of the second resistor R10 is connected to the end of the sampling resistor R9 connected to the second end AC2 of the AC power 100, the other end of the second resistor R10 is connected to the end of the sampling resistor R9 connected to the chopper driving module 150, the positive power supply of the operational amplifier U1A is connected to the power output terminal VCC of the power module 110, and the negative power supply of the operational amplifier U1A is grounded.

Furthermore, in an embodiment of the present invention, the current detecting module 160 further includes: the operational amplifier U1 comprises a fourth capacitor C5 and a clamp diode D2 connected to the same-direction input end of the operational amplifier U1A, a fifth capacitor C6 connected to the positive power supply of the operational amplifier U1A, and a fifth resistor R13 and a sixth capacitor C7 sequentially connected to the output end of the operational amplifier U1A, wherein the other ends of the fourth capacitor C5, the fifth capacitor C6 and the sixth capacitor C7 are grounded GND, the negative electrode of the clamp diode D2 is connected to the same-direction input end of the operational amplifier U1A, the positive electrode of the clamp diode D2 is grounded GND, and the other end of the fifth resistor R13 is connected to the controller 130.

Furthermore, in an embodiment of the present invention, the first filtering unit 143 is used for filtering the fire wire end ACL of the alternating current 100, the second filtering unit 145 is used for filtering the Zero-crossing signal of the first input terminal Zero output to the controller 130, the protection unit 144 is used for reverse protection of the reverse voltage input to the fire wire end ACL of the alternating current 100, wherein the maximum voltage value of the alternating current 100 is 311V, and at this time, the voltage resistance of the voltage resistance can be improved by setting two voltage dividing resistors of the first voltage dividing resistor R1 and the second voltage dividing resistor R2, so that the problem of insufficient voltage resistance caused by adopting a single voltage dividing resistor is avoided. Meanwhile, when the alternating current 100 is in the forward phase, the base B of the first transistor Q1 is at a high level to drive the first transistor Q1 to be turned on, so that the level of the first input terminal Zero input to the controller 130 is at a low level, and at the same time, the current flows from the live end ACL of the alternating current 100 to the ground after flowing through the first diode D1, the second voltage-dividing resistor R2 and the first transistor Q1; when the ac power 100 is in the reverse phase, the base B of the first transistor Q1 is at a low level to turn off the first transistor Q1, so that the level of the first input terminal Zero input to the controller 130 is at a high level, and at the same time, the current flows to the live end ACL of the ac power 100 after flowing through the first diode D1, the second voltage-dividing resistor R2 and the first voltage-dividing resistor R1. It should be noted that, since a certain voltage condition is required for the conduction of the first transistor Q1, there is a time delay of several tens of nanoseconds for the zero-crossing detection module 140 every time the alternating current 100 makes a zero-crossing.

Furthermore, in an embodiment of the present invention, the second switch unit 151 is a thyristor SR1, and the third switch unit 152 is a second transistor Q2, wherein the discharge resistor R7 is used for discharging the electric energy stored in the third capacitor C4; the second current limiting resistor R8 is used for limiting the current input into the second triode Q2; the third capacitor C4 is used for filtering the control signal output by the first output terminal SCR of the controller 130 to realize interference resistance; the first current limiting resistor R5 is used for limiting the current input by the alternating current 100; the coupling capacitor C3 is used to couple and isolate the strong current provided by the ac power 100 and the weak current provided by the third switching unit 152, and prevent the low frequency current from entering the weak current system provided by the third switching unit 152. When the controller 130 is in use, when the first output terminal SCR of the controller 130 outputs a low level, the second triode Q2 is in a cut-off state, and at this time, due to the blocking of the coupling capacitor C3, the voltage of the control electrode G of the thyristor SR1 is 0V, so that the thyristor SR1 is in a turn-off state, and the ac motor 120 does not work; when the first output terminal SCR of the controller 130 outputs a high level, the second triode Q2 is in a conducting state, and at this time, the level of the end of the coupling capacitor C3 is pulled down to-VCC, i.e., -3.3V or-5V, so that there is a VCC voltage drop between the main electrode of the thyristor SR1 and the control electrode G, so that the thyristor SR1 is controlled to be conducting, and at this time, the other end M2 of the ac motor 120 is communicated with the zero line terminal ACN of the ac power 100 after passing through the current detection module 160, so that the ac motor 120 is controlled to operate.

Furthermore, in an embodiment of the present invention, the equidirectional amplifying unit 162 is used for equidirectionally amplifying the current collected by the sampling unit 161, wherein the amplification factor is: (fourth resistor R12/second resistor R10) + 1; the fourth capacitor C5 is used for filtering; the clamping diode D2 controls the voltage input to the equidirectional input end of the operational amplifier U1A, so as to avoid the voltage input to the operational amplifier U1A from being too large or too small; when the alternating current 100 is in the positive phase, the current flows from the live wire end ACL of the alternating current 100 through the end M1 of the alternating current motor 120 and flows from the other end M2 of the alternating current motor 120 to the zero line end ACN of the alternating current 100, so that the voltage at the end of the sampling resistor R9 connected with the thyristor SR1 is higher than the voltage at the end of the sampling resistor R9 connected with the zero line end ACN of the alternating current 100, and the sampling current can be amplified in the same direction by the same-direction amplifying unit 162 at this time, so that the amplified current is output to the second input end DMA of the controller 130; when the alternating current 100 is in the reverse phase, the current of the alternating current 100 flows from the zero line terminal ACN of the alternating current 100 through the other end M2 of the alternating current motor 120, and the one end M1 of the alternating current motor 120 flows through the fire line terminal ACL of the alternating current 100, so that the voltage of the end, connected with the silicon controlled rectifier SR1, of the sampling resistor R9 is lower than the voltage of the end, connected with the zero line terminal ACN of the alternating current 100, of the sampling resistor R9, and at this time, the output level of the output end of the equidirectional amplification unit 162 is 0 to the second input end DMA; the equidirectional amplification unit 162 can amplify the current of the forward phase of the ac motor 120 by the equidirectional amplification factor, but not amplify the current of the reverse phase of the ac motor 120.

The current detection process includes that the zero-crossing detection module 140 detects a zero-crossing signal of the alternating current 100, when the controller 130 obtains that the zero-crossing detection module 140 detects that the level of the alternating current is converted from a high level to a low level, the controller 130 determines that the alternating current is in a first half period of a control cycle at the moment, the controller 130 delays for a preset time and then sends a control signal to the chopping drive module 150, so that the chopping drive module 150 controls the conduction of the silicon controlled rectifier SR1 to control the alternating current motor 120 to work, when the alternating current motor 120 works, the current detection module 160 can detect the current of the alternating current motor 120 in real time, the DMA module connected with the current detection module 160 collects and stores the current of the alternating current motor 120 in real time, when the controller 130 obtains that the zero-crossing detection module 140 detects that the level of the alternating current is converted from the low level to the high level, the controller 130 determines that the period is, at this time, the internal resource of the controller 130 starts to read the current value of the ac motor 120 collected and stored by the DMA module, and calculates the current effective value of the chopping current in the control period.

This embodiment, through in control cycle's first half period, control DMA module gathers the current value in real time, in control cycle's second half period, read the current value that DMA module gathered in first half period, and calculate the electric current virtual value that obtains chopping current in the control cycle through root mean square value algorithm, make and to sample in a control cycle's first half period, carry out corresponding calculation in second half period, make the electric current virtual value that can be quick in a control cycle detect out in this control cycle, make the electric current virtual value that can be quick effective and accurate calculation chopping current, the inaccurate problem of current detection has been solved.

Example four

Please refer to fig. 4, which is a schematic flow chart of a current detection method according to a fourth embodiment of the present invention, wherein the current detection method is implemented by applying the current detection circuit according to any of the embodiments. The method comprises the following steps:

and step S41, in the first half period of a control period, controlling the DMA module to acquire and store the current value in real time when the first preset level of the zero-crossing signal is passed.

In an embodiment of the present invention, the method is applied to detecting the chopping current of an ac motor, wherein the ac motor is connected to an ac power, specifically, the ac motor is connected to a controller MCU (specifically, the MCU employs an STM32 microcontroller), and a driving module is connected between the controller and the ac motor, so that the ac motor is driven by a control signal from the controller.

Furthermore, the controller is also connected with a zero-crossing detection module, and the zero-crossing detection module is connected with the alternating current and used for detecting the zero-crossing signal when the alternating current crosses zero and sending the zero-crossing signal to the controller. Specifically, in this embodiment, when the alternating current is converted from the reverse phase to the forward phase (i.e., when the alternating current is switched to the first half of the control cycle), the level detected by the zero-crossing detection module is converted from the high level to the low level; when the alternating current is converted from the forward phase to the reverse phase (namely, when the first half period of the control period is switched to the second half period), the level detected by the zero-crossing detection module is converted from the low level to the high level. At the moment, the controller correspondingly controls the alternating current motor to work according to the zero-crossing signal, and when the zero-crossing detection module detects the zero-crossing signal of the alternating current in specific implementation, the controller delays preset time to send a starting signal to the silicon controlled rectifier, and the silicon controlled rectifier controls the alternating current motor to correspondingly start according to the starting signal. Correspondingly, when the controller sends a stop signal to the silicon controlled rectifier, the silicon controlled rectifier controls the alternating current motor to correspondingly stop working.

At this time, according to the preset time length delayed by the controller, the chopped pulse width can be determined correspondingly, for example, when the alternating current works, the cycle of the sine wave is 20ms, the first half cycle of the upper half wave is 10ms, when the controller needs to chop the waveform of the first half segment of the upper half wave, the controller sends a starting signal to the thyristor after delaying for 5ms when acquiring the zero-crossing signal of the upper half wave in the sine wave detected by the zero-crossing detection module, so that the thyristor controls the alternating current motor to work, correspondingly, the alternating current motor does not work in the first 5ms of the upper half wave in the control cycle, the alternating current motor works in the last 5ms of the upper half wave in the control cycle, and the chopped pulse width is controlled by the controller so that the rotating speed of the alternating current motor can be controlled. In particular, the chopping can realize symmetrical chopping of sine waves.

Furthermore, the controller is also connected with a current detection module, and the current detection module is also connected with the alternating current motor and used for detecting the current of the alternating current motor during working and sending the current to the controller, so that the controller realizes the acquisition and calculation of the current of the alternating current motor during working.

Thus, the present embodiment provides a method for detecting an effective current value of a chopped current when an ac motor is operating with the chopped current. Specifically, the controller indicated in this embodiment includes a DMA module, and the DMA module is connected to the current detection module, wherein in the first half period of the control period, whenever the first preset level of the zero-crossing signal is passed, the DMA module is controlled to collect and store the current value detected by the current detection module in real time, and the time period of the current signal collected by the DMA module is very small, specifically, ns level, so that the precision of collecting the chopping current of the ac motor is very dense, and the chopping current of the ac motor can be accurately collected in real time. And the DMA module in the controller is independently collected in the current collection process, and can exchange data with external module equipment at high speed without being controlled by the controller MCU, so that the resources of the controller MCU are not occupied.

Specifically, the controller determines the first half cycle and the second half cycle of the control cycle in the following manner: the determination is made based on a first preset level and a second preset level of the zero crossing signal. Wherein, first predetermined level and second predetermined level are relative level signal, and in this embodiment, first predetermined level specifically is the low level, and the second predetermined level is the high level, can understand the utility model discloses an in other embodiments, still can be for first predetermined level to the high level, the second predetermined level is the low level, and it specifically sets up according to the in-service use demand, does not do the restriction here.

Specifically, when the alternating current is converted from the reverse phase to the forward phase (in this embodiment, the high level detected by the zero-crossing detection module is converted into the low level), the controller acquires the zero-crossing signal detected by the zero-crossing detection module, and when the subsequent level is the low level, the controller determines that the alternating current is in the first half period of the control period, so that the DMA module is controlled to collect and store the current value in real time.

Specifically, the controlling the DMA module to acquire and store the current value in real time can be implemented by the following steps:

carrying out zero point detection on the alternating current motor in real time, and timing when the zero point of the alternating current motor is judged to be zero, so as to obtain timing time;

and (II) controlling the DMA module to acquire and store the current value in real time when the timing time is equal to the time threshold.

Wherein, in the chopping current of the AC motor, the chopped waveform is substantially the waveform of the first half section, so the current value of the chopped waveform of the first half section of the AC motor is 0, at the moment, the acquisition is carried out in real time through the DMA module, which causes resource waste, therefore, the current value of the chopped waveform can be detected through the DMA module, specifically, the controller controls the pulse width of the chopping of the AC motor, at the moment, when the controller obtains the zero-crossing signal detected by the zero-crossing detection module, the controller sends a stop signal to the silicon controlled rectifier to enable the silicon controlled rectifier to control the AC motor to stop working and start timing to obtain timing time, when the timing time is equal to a time threshold (namely the chopping time determined by the chopping pulse width), the controller sends a start signal to the silicon controlled rectifier to enable the silicon controlled rectifier to control the AC motor to start working and controls the DMA module to start to acquire and store the current value of the AC motor in, therefore, the DMA module collects current when the alternating current motor works in the first half period of the control period, and the resource utilization maximization of the DMA module is realized.

And step S42, in a second half period of the control period, reading each current value stored in the DMA module whenever a second preset level of the zero-crossing signal is passed, and calculating by using a root mean square value algorithm to obtain a current effective value of the chopping current in the control period.

Wherein, in the utility model discloses an embodiment, in the latter half cycle of a controller cycle, when passing through the second preset level of zero cross signal, the controller acquires the zero cross signal that zero cross detection module detected promptly, and acquires follow-up level and be the high level, the controller confirms that this alternating current is being in the latter half cycle of control cycle this moment, the controller reads each current value that the MDA module was gathered and was kept in the former half cycle through the inside resource of system this moment to calculate the electric current virtual value of obtaining the chopping current in the control cycle through root mean square value algorithm in the latter half cycle time of control cycle.

And step S43, displaying the calculated current effective value in the control period in real time.

Wherein, in an embodiment of the utility model, the controller still is connected with a display module, and is concrete, and this display module can be LED LCD screen, OLED display screen etc., and wherein, after the controller calculated the electric current virtual value of the interior chopper current of control cycle at control cycle, send the data of this electric current virtual value to display module to make display module show the electric current virtual value that obtains in the control cycle in real time, make the user look over the electric current virtual value of current alternating current motor during operation in real time according to display module.

In step S44, it is determined whether the current effective value is greater than the current threshold value, thereby causing a current overload.

When it is determined that the current overload occurs due to the effective value of the current being greater than the current threshold, step S45 is executed; otherwise, no operation is done.

And step S45, highlighting the mark to display and record the time of the current overload and the value of the overload current.

When the current effective value is judged to be larger than the current threshold value to generate current overload, the current effective value, the current time and other data are sent to the display module at the moment so that the display module highlights, marks and displays the current overload time and the overload current value, wherein in the specific implementation, the display module marks the current effective value in a normal color (such as black); when the current is overloaded, the display module displays the overload current value and the time of the current overload by a salient mark (such as red), so that a user can quickly check the overload current value and the time of the current overload according to the salient mark, and further, the display of the salient mark is recorded and uploaded, so that the user can determine the current overload phenomenon when the alternating current motor works and the position of the chopped pulse width according to the historical recorded information, and the management control of the alternating current motor is facilitated.

Further, after the steps S43-S45, the method may further include accurately calculating the effective current value of the ac motor, and protecting the ac motor during current overload, specifically including the following two implementation manners:

the first method is as follows: carrying out current detection on the alternating current motor for preset times, and judging whether the times that the current effective value is greater than the current threshold value is greater than the time threshold value or not;

and when the times that the current effective value is larger than the current threshold value are judged to be larger than the time threshold value, determining that the current is overloaded, and disconnecting the drive of the controllable silicon so as to control the AC motor to be closed.

The second method comprises the following steps: carrying out current detection on the alternating current motor for preset times, and carrying out smooth filtering on each current effective value to obtain a weighted average so as to obtain an average current effective value in a control period of the preset times;

judging whether the average current effective value is larger than a current threshold value or not;

and when the effective value of the average current is larger than the current threshold value, determining that the current is overloaded, and disconnecting the drive of the controllable silicon so as to control the AC motor to be closed.

Wherein, in the first mode: for example, the preset number of times is set to 5, that is, the current effective value of the alternating current motor detected by the controller is continuously obtained 5 times, and the number of times that the current effective value is greater than the current threshold is recorded, for example, the current of the alternating current motor is detected for the first time, the current is collected in real time through the DMA module in the first half period of the control period, the current value collected in the DMA module is calculated in the first half period of the control period to obtain the current effective value, at this time, the calculated current effective value is compared with the current threshold, and when it is determined that the current effective value obtained for the first time is greater than the current threshold, the controller sets 1 in the recorded number of times; when carrying out AC motor's current detection once more, when confirming the electric current virtual value that acquires is greater than the electric current threshold value once more, then the controller adds up in the number of times of record, analogizes in proper order, and it is judged after predetermineeing the accumulative total of number of times, and whether the number of times that the electric current virtual value is greater than the electric current threshold value this moment is greater than the number of times threshold value, and is concrete, in this embodiment, the number of times threshold value sets for 3, can understand, the utility model discloses a in other embodiments, the number of times threshold value can set up according to the in-service use needs, does not do the injecing.

When the frequency that the current effective value is larger than the current threshold value is judged to be not larger than the frequency threshold value, the alternating current motor is determined to be in a normal working state, and at the moment, the phenomenon that the current effective value of the alternating current motor is larger than the current threshold value but is not overload operation of the alternating current motor is caused due to external interference.

When the times that the effective value of the current is larger than the current threshold value is judged to be larger than the time threshold value, the fact that the alternating current motor is in an overload working state at present, namely the current is overloaded, is determined, and therefore the controller correspondingly cuts off the drive of the controllable silicon, the alternating current motor is controlled to be turned off, and the problem that the alternating current motor is damaged due to long-time overload work of the alternating current motor is solved. Wherein, in the utility model discloses an in other embodiments, the pulse width of chopping current can also be increased in its controller corresponding control for control reduces alternating current motor's rotational speed, makes and chops the peak of alternating current motor's electric current in the alternating current, realizes reducing the electric current virtual value among the alternating current motor, thereby controls alternating current motor virtual value and is less than the current threshold value.

Wherein, in the second mode: the current detection is carried out on the alternating current motor for preset times, for example, the preset times are set to 5 times, namely, the current effective value of the alternating current motor detected by the controller is continuously obtained for 5 times, and the 5 current effective values are subjected to smoothing filtering and weighted averaging to obtain the average current effective value in a control period of 5 times, at the moment, the current effective values of multiple times are averaged, so that the current state of the current alternating current motor during working can be more accurately determined.

And when the effective value of the average current is not larger than the current threshold value, the alternating current motor is in a normal working state, and no treatment is carried out on the alternating current motor at the moment.

When the average current effective value is judged to be larger than the current threshold value, the fact that the alternating current motor is in an overload working state at present is determined, namely the current of the alternating current motor is overloaded, therefore, the controller correspondingly cuts off the drive of the controllable silicon, the alternating current motor is controlled to be closed, and the problem that the alternating current motor is damaged due to long-time overload work of the alternating current motor is avoided. Wherein, in the utility model discloses an in other embodiments, the pulse width of chopping current can also be increased in its controller corresponding control for control reduces alternating current motor's rotational speed, makes and chops the peak of alternating current motor's electric current in the alternating current, realizes reducing the electric current virtual value among the alternating current motor, thereby controls alternating current motor virtual value and is less than the current threshold value.

In the embodiment, because in the first half period of the control period, the DMA module is controlled to acquire the current value in real time, in the second half period of the control period, the current value acquired by the DMA module in the first half period is read, and the current effective value of the chopping current in the control period is calculated through the root mean square value algorithm, so that the sampling can be performed in the first half period of the control period, and the corresponding calculation is performed in the second half period, so that the current effective value in the control period can be quickly detected in one control period, the current effective value of the chopping current can be quickly, effectively and accurately calculated, and the problem of inaccurate current detection is solved.

EXAMPLE five

The fifth embodiment of the present invention further provides a household appliance, which comprises an ac motor, a memory, a processor, and a current detection circuit connected to the ac motor and having any one of the first embodiment to the third embodiment, wherein the memory is used for storing a computer program, and the processor executes the computer program to implement the fourth embodiment of the current detection method.

Specifically, the household equipment can comprise a stirrer, a wall breaking machine, a chef machine and other equipment with an alternating current motor, the current detection circuit provided by the first embodiment to the third embodiment is adopted, and the current detection method in the fourth embodiment is adopted to detect the chopping current of the alternating current motor, so that the working current effective value of the alternating current motor can be calculated and determined, corresponding control can be performed when the alternating current motor is overloaded, and the alternating current motor is prevented from being damaged.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. A current sensing circuit for chopper current sensing of an ac motor, the circuit comprising:

2. The current sensing circuit of claim 1, wherein the zero-crossing detection module comprises:

3. The current sense circuit of claim 1, wherein the chopping drive module comprises:

4. The current sensing circuit of claim 1, wherein the current sensing module comprises:

5. The current detection circuit according to claim 2, wherein the voltage dividing unit includes a first voltage dividing resistor and a second voltage dividing resistor connected in sequence to a first end of the alternating current, and the other end of the second voltage dividing resistor is connected to the first switching unit; the first switch unit is a first triode, the base of the first triode is connected with the voltage dividing unit, the emitting electrode of the first triode is grounded, and the collecting electrode of the first triode is connected with the controller and the power output end of the power module respectively.

6. The current sensing circuit of claim 5, wherein the zero-crossing detection module further comprises:

7. The current detection circuit according to claim 6, wherein the first filtering unit is a first capacitor, one end of the first capacitor is connected to the voltage dividing unit and the first switching unit, and the other end of the first capacitor is grounded; the protection unit is a first diode, the anode of the first diode is grounded, and the cathode of the first diode is respectively connected with the voltage division unit and the first switch unit; the second filtering unit comprises a first resistor and a second capacitor, one end of the first resistor is connected with a collector of the first triode, the other end of the first resistor is respectively connected with one end of the second capacitor and the controller, and the other end of the second capacitor is grounded; the collector of the first triode is also connected with one end of a first pull-up resistor, and the other end of the first pull-up resistor is connected with the power output end of the power supply module.

8. The current detection circuit according to claim 3, wherein the second switch unit is a thyristor, two main electrodes of the thyristor are respectively connected to the other end of the ac motor and the current detection module, a control electrode of the thyristor is connected to the third switch unit, the third switch unit is a second triode, a base of the second triode is connected to the controller, a collector of the second triode is respectively connected to the second switch unit and the power output terminal of the power supply module, and an emitter of the second triode is grounded.

9. The current sense circuit of claim 8, wherein the chopping drive module further comprises: connect gradually in the control pole of silicon controlled rectifier with first current-limiting resistor and coupling capacitance between the collecting electrode of second triode, connect in the collecting electrode of second triode with second pull-up resistance between the power output end of power module, and with discharge resistance, third electric capacity and the second current-limiting resistor that the base of second triode is connected, discharge resistance with the other end of third electric capacity all grounds, the other end of second current-limiting resistor with the controller is connected.

10. The current detection circuit according to claim 4, wherein the sampling unit is a sampling resistor, the equidirectional amplification unit includes an operational amplifier, a second resistor connected to the inverting input terminal of the operational amplifier, a third resistor connected to the equidirectional input terminal of the operational amplifier, and a fourth resistor connected between the inverting input terminal and the output terminal of the operational amplifier, the other end of the second resistor is connected to the end of the sampling resistor connected to the second end of the alternating current, the other end of the second resistor is connected to the end of the sampling resistor connected to the chopper drive module, the positive power supply of the operational amplifier is connected to the power supply output terminal of the power supply module, and the negative power supply of the operational amplifier is grounded.

11. The current sensing circuit of claim 10, wherein the current sensing module further comprises: the operational amplifier comprises a fourth capacitor and a clamping diode which are connected with the same-direction input end of the operational amplifier, a fifth capacitor which is connected with the positive power supply of the operational amplifier, and a fifth resistor and a sixth capacitor which are sequentially connected with the output end of the operational amplifier, wherein the other ends of the fourth capacitor, the fifth capacitor and the sixth capacitor are grounded, the negative electrode of the clamping diode is connected with the same-direction input end of the operational amplifier, the positive electrode of the clamping diode is grounded, and the other end of the fifth resistor is connected with the controller.

12. A household appliance, characterized in that the household appliance is provided with an alternating current motor and a current detection circuit according to any one of claims 1 to 11 connected to the alternating current motor, wherein the current detection circuit is used for detecting chopped current of the alternating current motor.