阅读说明：本技术 一种低功耗智能电流传感器及其工作模式控制方法 (Low-power-consumption intelligent current sensor and working mode control method thereof ) 是由 闵祥 匡成效 邹锦华 樊文露 于 2021-09-06 设计创作，主要内容包括：本发明公开了一种低功耗智能电流传感器及其工作模式控制方法,包括磁芯、与磁芯绕接的副边线圈、设置于磁芯中的磁传感器和电流检测电路,电流检测电路包括电源模块、驱动模块、微控制器、温度检测模块以及信号输入/输出接口模块。磁传感器的信号输出端与驱动模块的信号输入端连接,驱动模块分别与副边线圈的两端供电连接,微控制器分别与电源模块、驱动模块、温度检测模块和信号输入/输出接口模块信号连接,电源模块分别与驱动模块、微控制器、温度检测模块和信号输入/输出接口模块供电连接。本发明降低闭环电流传感器的发热量和待机功耗,同时将供电电压调理成稳定的符合要求的电压,来实现增大传感器的量程的目的。(The invention discloses a low-power-consumption intelligent current sensor and a working mode control method thereof. The signal output end of the magnetic sensor is connected with the signal input end of the driving module, the driving module is respectively in power supply connection with two ends of the secondary coil, the microcontroller is respectively in signal connection with the power supply module, the driving module, the temperature detection module and the signal input/output interface module, and the power supply module is respectively in power supply connection with the driving module, the microcontroller, the temperature detection module and the signal input/output interface module. The invention reduces the heating value and the standby power consumption of the closed-loop current sensor, and simultaneously regulates the power supply voltage into stable voltage meeting the requirements, thereby achieving the purpose of increasing the measuring range of the sensor.)

1. A low-power consumption intelligent current sensor comprises a magnetic core, a secondary coil wound with the magnetic core and a magnetic sensor arranged in the magnetic core, and is characterized by further comprising a current detection circuit, wherein the current detection circuit comprises a power module, a driving module, a microcontroller, a temperature detection module and a signal input/output interface module, the signal output end of the magnetic sensor is connected with the signal input end of the driving module, the driving module is respectively connected with the two ends of the secondary coil in a power supply mode, the microcontroller is respectively connected with the power module, the driving module, the temperature detection module and the signal input/output interface module in a signal connection mode, the power module is respectively connected with the driving module, the microcontroller, the temperature detection module and the signal input/output interface module in a power supply mode, and the input end and the output end of the signal input/output interface module are respectively connected with client end signals, the temperature detection module is arranged in the current sensor and used for detecting the temperature of the current sensor.

2. The low-power consumption intelligent current sensor according to claim 1, wherein the power module comprises a DC-DC converter, a first linear regulator and a second linear regulator, the input terminals of the DC-DC converter, the first linear regulator and the second linear regulator are all connected to the current sensor input terminal voltage Vcc, the output voltage U1 of the DC-DC converter is connected to the secondary winding through a driving module, the output voltage U2 of the first linear regulator is respectively connected to the driving module, the temperature detection module and the signal input/output interface module, the output voltage U3 of the second linear regulator is connected to the microcontroller, and three power supply circuits in the power module are controlled by the microcontroller.

3. The low-power consumption intelligent current sensor is characterized in that the signal input/output interface module is replaced by a signal output interface module, and a wake-up port is also arranged and is in signal connection with the microcontroller.

4. The method for controlling the working mode of the low-power-consumption intelligent current sensor as claimed in any one of claims 1 to 3, is characterized by comprising a normal working mode, a low-power-consumption mode, a standby mode and a sleep mode, and the specific control method comprises the following steps:

and (3) a normal working mode: the current sensor enters a normal working mode after being electrified, at the moment, the microcontroller controls the power supply module to uninterruptedly supply power to the secondary coil, monitors the temperature of the current sensor in real time through the temperature detection module, acquires current information of a sampling resistor in the driving module in real time, calculates the magnitude of primary current according to the acquired current information, outputs a current measurement result to a client through the signal input/output interface module or the signal output interface module, and controls the current sensor to exit the normal mode to enter other modes according to an external instruction or an internal trigger condition;

low power consumption mode: in the temperature rising process, when the temperature detection module detects that the temperature of the current sensor is greater than a preset temperature threshold value T₁When the current sensor enters a low-power-consumption mode, the microcontroller controls the power supply module to carry out power-on or power-off operation on the secondary coil in each preset current measurement period, and the current sensor is powered off immediately after the current measurement is finished in the power-on time of the secondary coil; in the temperature reduction process, when the temperature detection module detects that the temperature of the current sensor is lower than a preset temperature threshold value T₂When the current sensor is in the normal working mode, the microcontroller controls the current sensor to enter the standby mode;

standby mode: when the current sensor is in a normal working mode or a low power consumption mode, when the absolute value of the primary current is smaller than a preset current threshold I₁After a certain time t, the current sensor enters a standby mode, the temperature sensor monitors the temperature of the current sensor in real time in the standby mode, the microcontroller monitors the primary current but does not send a signal to the client, and when the absolute value of the primary current is greater than a current threshold I₁The current sensor automatically restores to a normal working mode, and the microcontroller externally sends a current measurement result;

a sleep mode: when the standby mode is carried out for a period of time t', the current sensor enters the sleep mode, the microcontroller controls the power supply module to cut off the power of the secondary coil, the temperature sensor and the driving module, the signal input/output interface module or the awakening port is in the monitoring mode, the microcontroller controls the power supply module to work in the sleep mode, monitors the signal input/output interface module or the awakening port only, receives a client instruction, the client inputs the awakening instruction through the signal input/output interface module or the awakening port, and the microcontroller controls the current sensor to enter the normal working mode according to the awakening instruction.

Technical Field

The invention belongs to the technical field of current sensors, and particularly relates to a low-power-consumption intelligent current sensor and a working mode control method thereof.

Background

Conventional closed-loop control based current sensors typically include a magnetic sensor, a secondary winding, and a drive circuit. The magnetic sensor includes, for example, a hall effect probe, a magnetoresistance effect probe, a fluxgate probe, and the like. The secondary winding is provided with a soft magnetic core with high magnetic permeability. When the current in the primary conductor generates a magnetic field around the conductor, the magnetic sensor converts the sensed magnetic field signal into an electric signal, drives the secondary compensation secondary coil to generate a magnetic field with the direction opposite to the direction of the primary current magnetic field and the magnitude equal to the primary current magnetic field in the soft magnetic core, and the magnitude of the obtained secondary current is related to the primary current amplitude. According to the principle, the current sensor can realize primary side-secondary side high-voltage insulation design and high-precision measurement, and the technology is widely applied to current measurement of robots, new energy vehicles and other industrial fields.

However, the current sensor based on the closed-loop control needs to consume current to generate a magnetic field on the secondary side for balancing the magnetic field generated by the primary side current when measuring current, so that heat is generated, and the heat increases with the increase of the primary side current. In order to reduce the temperature rise of the current sensor and ensure that the current sensor can reliably work for a long time, the current sensor is usually immersed in glue with good heat-conducting property for heat dissipation. But the adoption of the heat-conducting glue not only increases the production cost and the dead weight of the current sensor, but also increases the environmental protection pressure. In addition, such current sensors still consume current when there is no primary current, and the standby power consumption is high, causing unnecessary waste of energy. In addition, in some applications, the supply voltage of the current sensor fluctuates in a large voltage range, and the range of the current sensor is limited by the lower limit of the supply voltage on the premise of not increasing the size of the sensor.

Disclosure of Invention

The invention discloses a low-power consumption intelligent current sensor and a working mode control method thereof, aiming at the problems of overheating, high standby power consumption and the limitation of the measuring range to the minimum power supply voltage of the current sensor based on closed-loop control, and aiming at reducing the heating value and standby power consumption of the closed-loop current sensor and regulating the power supply voltage into stable voltage meeting the requirements to realize the purpose of increasing the measuring range of the sensor.

The invention mainly adopts the technical scheme that:

a low-power consumption intelligent current sensor comprises a magnetic core, a secondary coil wound with the magnetic core, a magnetic sensor arranged in the magnetic core and a current detection circuit, wherein the current detection circuit comprises a power module, a driving module, a microcontroller, a temperature detection module and a signal input/output interface module, the signal output end of the magnetic sensor is connected with the signal input end of the driving module, the driving module is respectively connected with the two ends of the secondary coil in a power supply manner, the microcontroller is respectively connected with the power module, the driving module, the temperature detection module and the signal input/output interface module in a signal manner, the power module is respectively connected with the driving module, the microcontroller, the temperature detection module and the signal input/output interface module in a power supply manner, and the input end and the output end of the signal input/output interface module are respectively connected with a client end in a signal manner, the temperature detection module is arranged in the current sensor and used for detecting the temperature of the current sensor.

Preferably, the power module comprises a DC-DC converter, a first linear regulator and a second linear regulator, the input ends of the DC-DC converter, the first linear regulator and the second linear regulator are all connected with the input end voltage Vcc of the current sensor, the output voltage U1 of the DC-DC converter is connected with the secondary coil through a driving module, the output voltage U2 of the first linear regulator is respectively connected with the driving module, the temperature detection module and the signal input/output interface module, the output voltage U3 of the second linear regulator is connected with the microcontroller, and three power supply circuits in the power module are controlled by the microcontroller to be switched on and off.

Preferably, the signal input/output interface module is replaced by a signal output interface module, and a wake-up port is further provided, and the wake-up port is in signal connection with the microcontroller.

A working mode control method of a low-power consumption intelligent current sensor is characterized by comprising a normal working mode, a low-power consumption mode, a standby mode and a sleep mode, and the specific control method comprises the following steps:

and (3) a normal working mode: the current sensor enters a normal working mode after being electrified, at the moment, the microcontroller controls the power supply module to uninterruptedly supply power to the secondary coil, monitors the temperature of the current sensor in real time through the temperature detection module, acquires current information of a sampling resistor in the driving module in real time, calculates the magnitude of primary current according to the acquired current information, outputs a current measurement result to a client through the signal input/output interface module or the signal output interface module, and controls the current sensor to exit the normal mode to enter other modes according to an external instruction or an internal trigger condition;

low power consumption mode: in the temperature rising process, when the temperature detection module detects that the temperature of the current sensor is greater than a preset temperature threshold value T₁When the current sensor enters a low-power-consumption mode, the microcontroller controls the power supply module to carry out power-on or power-off operation on the secondary coil in each preset current measurement period, and the current sensor is powered off immediately after the current measurement is finished in the power-on time of the secondary coil; in the temperature reduction process, when the temperature detection module detects that the temperature of the current sensor is lower than a preset temperature threshold value T₂When the current sensor is in the normal working mode, the microcontroller controls the current sensor to enter the standby mode;

standby mode: when the current sensor is in a normal working mode or a low power consumption mode, when the absolute value of the primary current is smaller than a preset current threshold I₁After a certain time t, the current sensor enters a standby mode, the temperature sensor monitors the temperature of the current sensor in real time in the standby mode, the microcontroller monitors the primary current but does not send a signal to the client, and when the absolute value of the primary current is greater than a current threshold I₁The current sensor automatically restores to a normal working mode, and the microcontroller externally sends a current measurement result;

a sleep mode: when the standby mode is carried out for a period of time t', the current sensor enters the sleep mode, the microcontroller controls the power supply module to cut off the power of the secondary coil, the temperature sensor and the driving module, the signal input/output interface module or the awakening port is in the monitoring mode, the temperature sensor stops working, the microcontroller controls the power supply module to work in the sleep mode, monitors only the signal input/output interface module or the awakening port, receives a client instruction, the client inputs the awakening instruction through the signal input/output interface module or the awakening port, and the microcontroller controls the current sensor to enter the normal working mode according to the awakening instruction.

Has the advantages that: the invention provides a low-power consumption intelligent current sensor and a working mode control method thereof, which have the following advantages:

(1) a proper control strategy is adopted to reduce the heat productivity of the closed-loop current sensor, so that the overheating problem is solved;

(2) the working state of the components is controlled by the microcontroller, so that the power consumption is reduced;

(3) the purpose of increasing the range is realized by introducing a DC-DC (direct current to direct current) converter to condition the power supply voltage into stable voltage meeting the requirement;

(4) the microcontroller is adopted to control the power supply module to respectively supply power to each component, thereby being beneficial to realizing the intelligent control of the current sensor.

Drawings

FIG. 1 is a schematic view of the internal structure of a current sensor according to embodiment 1;

FIG. 2 is a schematic view of the operation mode of embodiment 1;

FIG. 3 is a schematic view of the normal operation mode of embodiment 1;

FIG. 4 is a schematic view of the standby mode of embodiment 1;

FIG. 5 is a comparison of power consumption of the current sensor of example 1 and that of a conventional current sensor;

fig. 6 is a circuit configuration diagram of a driving module in embodiment 1;

FIG. 7 is a schematic view of the internal structure of a current sensor according to embodiment 2;

in the figure: magnetic core 1, secondary winding 2, magnetic sensor 3, primary side conductor 4.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Example 1

As shown in fig. 1, a low power consumption intelligent current sensor comprises a magnetic core 1, a secondary coil 2 wound with the magnetic core 1, a magnetic sensor 3 disposed in the magnetic core 1, and a current detection circuit, wherein the current detection circuit comprises a power module, a driving module, a microcontroller, a temperature detection module, and a signal input/output interface module, a signal output end of the magnetic sensor 3 is connected with a signal input end of the driving module, the driving module is respectively connected with two ends of the secondary coil 2 for power supply, the microcontroller is respectively connected with the power module, the driving module, the temperature detection module, and the signal input/output interface module for signal connection, an input end and an output end of the signal input/output interface module are respectively connected with a client end for signal connection, the temperature detection module is installed in current sensor for detect current sensor temperature, power module includes DC-DC converter, first linear voltage regulator and second linear voltage regulator, the input of DC-DC converter, first linear voltage regulator and second linear voltage regulator all is connected with current sensor input voltage Vcc, the output voltage U1 of DC-DC converter pass through drive module with secondary winding 2 power supply is connected, the output voltage U2 of first linear voltage regulator respectively with drive module, temperature detection module and signal input/output interface module power supply are connected, the output voltage U3 of second linear voltage regulator with microcontroller power supply is connected.

In embodiment 1, the current sensor input terminal voltage Vcc fluctuates between Vcc1 and Vcc2 (Vcc 1 ≠ Vcc 2), and the secondary winding 2The magnitude of the supply voltage U1 depends on the maximum current of the secondary windingIp _max And driving module voltage dropU _drop The size of U1 can be adjusted according to equation (1), and thus the current sensor's range is not limited by the current sensor input voltage Vcc.

U1≥R _c *Ip _max +U _drop （1）；

In the formula (1), the reaction mixture is,R _c the maximum secondary coil resistance.

The circuit structure of the driving module in embodiment 1 is shown in fig. 6, and includes a first operational amplifier OP1, a second operational amplifier OP2, and an operational amplifier M₁A first NPN transistor Q1, M₂A first PNP triode Q2, M₃A second NPN transistor Q4, M₄A second PNP transistor Q3 and a sampling resistor Res1, M₁、M₂、M₃、M₄The current sampling circuit comprises a first operational amplifier OP1, a first NPN triode Q1, a second NPN triode Q4, a sampling resistor Res1 and an external sampling circuit (which belongs to the conventional technology and is not described in detail), wherein the input end of the first operational amplifier OP1 is connected with the signal output end of the magnetic sensor 3, the emitter of the first NPN triode Q1 is connected with the emitter of the first PNP triode Q2 at the end a and then is connected with the end b of the secondary coil 2, the emitter of the second NPN triode Q4 and the emitter of the second PNP triode Q3 are connected with the end d and then are connected with the end c of the secondary coil 2, and the sampling resistor Res1 is connected with the external sampling circuit (which belongs to the conventional technology and is not described in detail), and the sampling circuit transmits the collected current signal to the microcontroller to calculate the primary current.

The working principle of example 1 is as follows:

during measurement, the primary side current is conducted in the primary side conductor 4I _p The magnetic field is generated by penetrating through the magnetic core 1, then the magnetic sensor 3 converts the magnetic signal into an electric signal and outputs the electric signal to the driving module for triggering the driving module to work, the power supply module outputs U1 to supply power to the secondary coil 2 through the driving module, so that a magnetic field which is equal to the primary current magnetic field in magnitude and opposite to the primary current magnetic field is generated in the magnetic core 1, and the magnetic induction intensity in the magnetic core 1 is kept to be equal toAnd (4) zero. The microcontroller samples the secondary current through a sampling resistor of the driving module, calculates the acquired secondary current signal to obtain the magnitude of the primary current, and then sends the signal to the client through the signal input/output interface module. The client also inputs instructions to the microcontroller through the signal input/output interface module, and the microcontroller controls the current sensor to enter a corresponding working mode according to the instructions. The voltage Vcc of the input end of the current sensor fluctuates between Vcc1 and Vcc2, and a DC-DC converter in the power module converts the voltage Vcc of the input end of the current sensor into U1 to supply power to the secondary coil 2; meanwhile, the power supply module supplies power to the driving module, the signal input/output interface module and the temperature detection module through a first linear regulator (LDO) output U2. The power module supplies power to the microcontroller through a second linear regulator (LDO) output U3, the temperature controller detects the working temperature of the current sensor in real time and transmits the collected temperature signal to the microcontroller, and the microcontroller controls the current sensor to enter a corresponding working mode according to the received temperature signal. And the power supply circuit of the power supply module is controlled to be switched on and off by the microcontroller.

As shown in fig. 2, the control method of the four operation modes of embodiment 1 is as follows:

and (3) a normal working mode: the current sensor enters a normal working mode after being electrified, at the moment, the microcontroller controls the power supply module to uninterruptedly supply power to the secondary coil 2, monitors the temperature of the current sensor through the temperature detection module, outputs a current measurement result through the signal input/output interface, and controls the driving module to exit the normal mode and enter other modes according to an external instruction or an internal trigger condition;

as shown in fig. 3, at t₀At the moment, the voltage Vcc at the input end of the current sensor is electrified, and the microcontroller controls the driving module to supply power U1 to the secondary coil 2₁The moment driving module starts to output the collected current signal to the microcontroller, t₂And the measurement is started at the moment, the microcontroller calculates the magnitude of the primary current according to the collected secondary current signal, and outputs a primary current measurement value to the client through the signal input/output interface module. The wholeIn the measuring process, the driving module, the secondary coil 2, the temperature detection module, the microcontroller and the signal input/output interface module are electrified all the time.

Low power consumption mode: in the temperature rising process, when the temperature detection module detects that the temperature of the current sensor is greater than a preset temperature threshold value T₁When the current sensor enters a low-power-consumption mode, the microcontroller controls the power supply module to carry out power-on or power-off operation on the secondary coil 2 in each preset current measurement period, and the current sensor is powered off immediately after the current measurement is finished within the power-on time of the secondary coil 2; in the temperature reduction process, when the temperature detection module detects that the temperature of the current sensor is lower than a preset temperature threshold value T₂When the current sensor is in the normal working mode, the microcontroller controls the current sensor to enter the standby mode;

standby mode: when the current sensor is in a normal working mode or a low power consumption mode, when the absolute value of the primary current is smaller than a preset current threshold I₁After a certain time t (which is preset), the current sensor enters a standby mode, the temperature sensor monitors the temperature of the current sensor in real time in the standby mode, the microcontroller monitors the primary current but does not send a signal to the client, and when the absolute value of the primary current is greater than a current threshold I₁The current sensor automatically restores to a normal working mode, and the microcontroller externally sends a current measurement result; i is₁The value is very small, so that in the working mode, the primary conductor 4 has almost no primary current, and the output port of the signal input/output interface module of the current sensor does not work, so that part of the power consumption of the module is saved.

As shown in FIG. 4, a predetermined current measurement period is from t₀Time of day start, t₅End of time at t₀At the moment, the voltage Vcc at the input end of the current sensor is electrified, t₁At the moment of time the primary current, t, is input in the primary conductor 4₂The time microcontroller controls the drive module to supply power to the secondary coil 2 until t₃The microcontroller finishes the acquisition of the secondary current signal and the calculation of the primary current at the moment until t₄And (6) finishing the output of the measured current result at the moment.t₆-t₁₀For the next current measuring period (t)₅And t₆Whether the interval exists can be set according to actual conditions). In each measurement cycle, only t₂-t₃The voltage U1 is applied to the time driving module and the secondary winding 2, and is off at other times, so that no power is consumed. Input time t of primary current₂May be t₀-t₁At any time in between, including t₀And t₁。

A sleep mode: when the standby mode is carried out for a period of time t', the current sensor enters the sleep mode, the microcontroller controls the power supply module to cut off the power of the secondary coil 2, the driving module and the temperature sensor, the signal input/output interface module or the awakening port is in the monitoring mode, the microcontroller controls the power supply module to work in the sleep mode, monitors the signal input/output interface module only, receives a client instruction, the client inputs the awakening instruction through the signal input/output interface module, and the microcontroller controls the current sensor to enter the normal working mode according to the awakening instruction.

In embodiment 1, the power consumption of the current sensor is determined by the power consumption of the magnetic sensorP _sense Power consumption of driving moduleP _drive Secondary side coil power consumptionP _coil Power consumption of signal input/output interface moduleP _com Microcontroller power consumptionP _mcu And the efficiency eta of the power module (the power consumption of the temperature sensor is low and can be ignored), and the power consumption of the current sensorP _sum The specific calculation formula is as follows:

P _sum =(P _sense +P _drive +P _coil +P _com +P _mcu )/η （2）。

in the normal working mode, all modules of the current sensor are in the power-on working state, and the maximum power consumption isP ₁ 。

When entering the low power consumption mode, because the power supply time is largeReduced, magnetic sensor 3 power consumptionP _sense Power consumption of driving moduleP _drive And secondary winding 2 power consumptionP _coil Greatly reduced power consumption of signal input/output interface moduleP _com And microcontroller power consumptionP _mcu No change occurs, when the total power consumption of the current sensor isP ₂ And is andP ₂ <P ₁ ；

when entering standby mode, the current sensor is only on the input tiny primary side (smaller thanI ₁ ) The current is monitored and is not sent to the outside, namely, the power consumption of the output port of the signal input/output interface module is 0, thenP _com Greatly reducing the cost. Because of the fact thatI ₁ Is very small, so that the total power consumption of the current sensor isP ₃ And is andP ₃ <P ₂ ；

when the current sensor enters a sleep mode, the driving module is not powered, no current exists on the secondary coil 2, the microcontroller works in a sleep state and monitors only the input signal on the signal input/output interface module, and therefore the total power consumption of the current sensor at the momentP ₄ At a minimum, i.e.P ₄ <P ₃ <P ₂ <P ₁ 。

As shown in fig. 5, the power consumption of the current sensor in embodiment 1 is compared as follows: in the same current detection environment and scheme, the temperature rise of the current sensor in a normal working mode and a low-power consumption intelligent control mode can be found by comparing:

in this embodiment 1, the temperature rise of the current sensor only in the normal operation mode reaches 65 ℃ after the temperature is stabilized. In this embodiment 1, after the current sensor starts the low power consumption intelligent control mode, the current sensor works in the normal mode after being powered on, the temperature in the current sensor rapidly rises, and by 600s, the temperature detected by the temperature sensor in the current sensor is greater than the preset temperature threshold T₁Trigger micro-controlIn the low power consumption mode of the starting system (the microcontroller can also be triggered by the input of a control signal of an external client), the temperature of the current sensor is reduced to 42 ℃, and compared with the temperature rise of the traditional sensor, the temperature rise is reduced by about 23 ℃ and about 35.3%.

Example 2

As shown in fig. 7, the low-power consumption intelligent current sensor includes a magnetic core 1, a secondary winding 2 wound around the magnetic core 1, a magnetic sensor 3 disposed in the magnetic core 1, and a current detection circuit, where the current detection circuit includes a power module, a driving module, a microcontroller, a temperature detection module, a signal output interface module, and a wake-up port. The difference between the embodiment 2 and the embodiment 1 is that the signal input/output interface module is replaced by an output interface module, that is, the output interface module does not have the capability of receiving an external input signal, and a wake-up port is added, the wake-up port is in signal connection with the microcontroller, and the structures and the connection relations of other devices are the same as those of the embodiment 1. After the wake-up port is added, the four working modes of the current sensor are unchanged, but the wake-up of the current sensor in the sleep mode needs to be carried out through the wake-up port.

The temperature detection module in the technical solutions described in embodiments 1 and 2 may be replaced by a microcontroller having a temperature detection function, that is, the temperature detection module is integrated in the microcontroller, which belongs to the prior art. The control method of the operation mode is the same as that in embodiment 1 or 2.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.