428 results about "Lower limit" patented technology

Provided is an image forming apparatus including: an image forming unit configured to form an image on a recording material; an exhaust fan configured to exhaust air inside the image forming apparatus; a CPU configured to control rotation of the exhaust fan; and a memory configured to store in advance a first control setting value for rotating the exhaust fan at a first target rotation speed. The CPU rotates the exhaust fan based on the first control setting value, and permits the image forming unit to form an image when a rotation speed of the exhaust fan becomes equal to or faster than a lower limit rotation speed for suppressing a discharge amount of UFPs. When a predetermined time period has elapsed, the CPU performs feedback control for the exhaust fan such that the exhaust fan is rotated faster than the first target rotation speed.

The invention provides a data exception early warning method and device based on a dynamic threshold model. The method comprises the following steps: firstly, constructing an index time sequence library and an event library for storing index and event information; fusing the historical same-period base line, the trend term and the event influence value and generating a base line through a dynamic weight formula; calculating upper and lower limits of a dynamic threshold by combining the fluctuation acceleration and a basic fluctuation coefficient; and finally, comparing the real-time index value with a threshold range to judge whether to give an alarm, and optimizing the model or updating the event library according to a manual labeling result. According to the method, dynamic and accurate early warning of data exception can be realized, service scene changes can be adapted, the early warning accuracy is continuously improved through feedback optimization, and powerful support is provided for stable service operation and efficient exception disposal.

The invention discloses a motor control device and an air conditioner. The motor control device comprises an injection signal controller; the high-frequency pulse injection observer receives the high-frequency current and outputs a first observation angle; the IF and pulse injection switching controller is configured to receive a signal output by the rotating speed control part; when the acceleration of the motor reaches a lower limit value of a preset threshold value, switching an IF control mode and outputting a q-axis target current, when the current value of the motor reaches an upper limit value of a preset current value, reducing the q-axis target current, and when the acceleration reaches an upper limit value of the preset threshold value, keeping applying a pulse high-frequency voltage signal and enabling a rotating speed control part to output the q-axis target current; and the angle switching controller is configured to control and output a required observation angle according to the real-time rotating speed of the motor, a first observation angle observed by the high-frequency pulse injection observer and a second observation angle observed by the sliding-mode observer in the FOC speed current double-closed-loop architecture. Reliable starting and operation of the motor can be ensured.

To make it possible to set an appropriate threshold value for detecting a print defect by taking into consideration an impurity included in a sheet. A lower limit value of a threshold value used for detection of a print defect is found and stored in advance. Then, whether or not a threshold value for detecting a print defect, which is set based on user instructions, is an appropriate threshold value is determined by using the lower limit value stored in advance.

The invention relates to an equipment rotating speed monitoring-based equipment operation data full-amount storage method, which relates to the field of data processing, and comprises the following steps of: constructing a query fault-tolerant condition based on an equipment model of to-be-monitored bit number equipment, a transmission element model list and a transmission element service life list; searching a historical operation sample group meeting a query fault tolerance condition; counting a plurality of control mode starting completion rotation speed characteristic values of the historical operation sample group, setting the minimum value as a rated rotation speed upper limit value, counting a plurality of control mode stopping completion rotation speed characteristic values of the historical operation sample group, and setting the maximum value as a rated rotation speed lower limit value; when the equipment monitoring rotating speed at the first moment falls between the rated rotating speed lower limit value and the rated rotating speed upper limit value, full storage is started, otherwise, interval storage is executed according to a preset period, and the problems that key parameter changes in the equipment starting and stopping process are difficult to accurately capture, data storage efficiency is low, and important information is prone to being missed are solved. And maintenance and analysis are difficult to carry out.

The invention discloses an intelligent online monitoring method and system for a transformer, and the method comprises the steps: dividing historical data into a plurality of working condition intervals according to the historical working condition data, and enabling each working condition interval to have a numerical range corresponding to a working condition parameter; based on all historical operation data in the working condition interval, a dynamic reference range corresponding to the working condition interval is determined, and the dynamic reference range is a numerical value interval with an upper limit value and a lower limit value; obtaining a current operation parameter value and a corresponding current working condition parameter value of the target transformer in real time; determining a target working condition interval from the plurality of working condition intervals according to the current working condition parameter value; obtaining a target dynamic reference range corresponding to the target working condition interval; and when it is determined that the current operation parameter value is not located in the target dynamic reference range, it is determined that the transformer is abnormal, and an early warning signal is generated. The method is used for improving the early warning accuracy and reliability of transformer monitoring.

The invention provides a composite material bearing structure storage life evaluation method considering an acceleration stress lower limit, and the method comprises the steps: 1, carrying out the initialization modeling: enabling the service life of a product to obey the logarithmic normal distribution, and building a three-parameter inverse power law acceleration model of the service life feature theta and the stress level S; 2, estimating parameters: estimating unknown parameters by applying a maximum likelihood estimation method for the three-parameter inverse power law acceleration model; 3, model selection: comparing the calculated likelihood function values, wherein the larger the likelihood function value is, the more stable and more accurate the model is; meanwhile, the variation coefficients of the acceleration factors are calculated in combination with test data for comparison, and the model with the small variation coefficient is more accurate; and 4, accelerated life evaluation: giving reliability, and evaluating the storage life of the three-parameter inverse power law model. The method is suitable for accelerated test evaluation of a product with a threshold effect; the three-parameter inverse power law model provided by the invention can show a better model fitting effect when the acceleration effect does not meet the linear characteristic.

The invention relates to the technical field of FPC (Flexible Printed Circuit) laminated structure optimization, in particular to a module FPC laminated structure optimization system based on signal integrity, which comprises a laminated parameter sensitivity extraction module used for defining the thickness of a dielectric layer, the thickness of a copper foil and a dielectric constant as closed interval values with upper and lower boundaries according to FPC design specifications. According to the method, the accumulated deviation area and the normalized confidence score are obtained in combination with integral operation, conversion from a frequency domain to a time domain and from qualitative analysis to quantitative evaluation is achieved, tiny flaws of impedance continuity are captured, inferior paths are screened based on the confidence score, and a physical junction area is positioned. The geometric gravity center of the deviation area is calculated to be matched with the slope and the length of the gradient line, a smoothly-transited geometric figure is constructed, structural compensation can be achieved in areas where impedance is prone to sudden change such as a reinforcing plate junction and covering film pressing, and signal reflection caused by physical sudden change of a stacked structure is eliminated.

The invention discloses a reaction steam turbine through-flow method and system based on variable reaction degree optimization, and belongs to the technical field of steam turbine through-flow design. The method comprises the steps that an initial geometric model of a steam turbine through-flow part and thermal boundary conditions of all stages are obtained; inputting the initial geometric model and the thermal boundary conditions into a flow field solver, and solving a flow control equation to obtain an original flow field solution; constructing a functional taking through-flow efficiency as a target, and deducing an adjoint equation corresponding to the flow control equation; solving the adjoint equation to obtain gradient information of the target functional to each level of reaction degree; inputting the gradient information into a sequential quadratic programming optimizer, and iteratively updating the reactance of each stage by combining the maximum equivalent stress upper limit of the moving blade and the lower limit of the through-flow throat area to generate a variable reactance distribution scheme; and adjusting molded line geometric parameters of each stage of stationary blade and moving blade, and outputting optimized three-dimensional molded line data and a digital model file for numerical control machining. According to the method, the in-stage flow loss is reduced, and the design robustness is enhanced.

The invention discloses a big data real-time calculation abnormal value filtering method and a terminal. The method comprises the following steps: acquiring scene basic data, establishing a relevance rule of master data and slave data in the scene basic data, determining upper and lower limit parameters of the master data, the slave data and the scene basic data according to data attributes, and calculating a basic data value of the scene basic data; determining a preset range of the scene basic data by using machine learning in combination with upper and lower limit parameters of the master and slave data and the scene basic data; if the basic data value of the scene basic data is within the preset range, calculating the fluctuation range and the fluctuation value, and if the fluctuation value exceeds the fluctuation range, determining that the scene is abnormal; if the fluctuation value does not exceed the limit, the deviation proportion is calculated, and if the deviation proportion exceeds a preset abnormity judgment coefficient, abnormity is judged; if the deviation proportion does not exceed the limit, finally judging the deviation proportion through an abnormal rule in a preset decision tree; abnormal data are eliminated, filtered data and basic data values thereof are obtained, and the adaptability and reliability of abnormal value detection are improved.

An aerial work platform, and a method and apparatus for safety control of an aerial work platform, said method comprising: determining whether a work platform (100) is located at an upper limit position or a lower limit position; acquiring a first angle value of a scissor frame (200) corresponding to the upper limit position, and using the first angle value as an upper limit calibration value; or acquiring a second angle value of the scissor frame (200) corresponding to the lower limit position, and using the second angle value as a lower limit calibration value; acquiring a current angle value of the scissor frame (200) and a current inclination angle value of a chassis (300); and, on the basis of the current angle value of the scissor frame (200) and the current inclination angle value of the chassis (300), determining an angle compensation value for the work platform (100), and, on the basis of the difference between the angle compensation value and the upper limit calibration value or the lower limit calibration value, determining a limit position of the work platform (100). Thus, a limiting structure or a limiting switch can be replaced for limiting, operation is intelligent, the reliability is high, and fault alarms caused by a stroke switch being stuck can be prevented, so as to save operation costs.

The invention discloses a distributed current limiting method, device and system and a storage medium. The method comprises the following steps: periodically generating and broadcasting a concurrent suggestion interval based on a local operation state; concurrence suggestion intervals generated by the service instance and from other service instances are received, intersection operation is carried out, a global feasible interval is obtained, the upper limit is the minimum value of the upper limits of all the concurrence suggestion intervals, and the lower limit is the maximum value of the lower limits of all the concurrence suggestion intervals; and determining a local current limiting threshold based on the global feasible interval and the local dynamic weight. Each service instance receives the concurrence suggestion interval and then performs intersection operation to determine the global feasible interval, so that the upper limit is monotonically not increased and cannot be exceeded, the security invariant constraint chain is obtained, a central coordinator or a global synchronous clock is not needed, and the global concurrence quantity does not exceed the security upper limit under any network condition; and determining a local current-limiting threshold value based on the global feasible interval and the local dynamic weight, and realizing refined and adaptive current-limiting management.

The embodiment of the invention provides a rotor temperature prediction method and device and driving equipment, and belongs to the technical field of motor monitoring, and the method comprises the steps: inputting the obtained real-time working parameters of a motor into a pre-constructed temperature prediction model, and obtaining a temperature prediction result of a rotor; wherein the temperature prediction result comprises the real-time prediction temperature, the upper limit value of the real-time prediction temperature and the lower limit value of the real-time prediction temperature, and a temperature interval formed by the upper limit value of the real-time prediction temperature and the lower limit value of the real-time prediction temperature is used for representing the confidence coefficient of the real-time prediction temperature. According to the rotor temperature prediction method provided by the embodiment of the invention, the real-time predicted temperature of the rotor and the upper limit value and the lower limit value of the real-time predicted temperature are obtained by inputting the motor real-time working parameters of the rotor into the temperature prediction model, and the confidence coefficient of the real-time predicted temperature is represented through the upper limit value and the lower limit value of the real-time predicted temperature. Therefore, the accuracy of rotor temperature prediction is improved, and misjudgment caused by rotor temperature prediction errors is avoided.

Proposed are a method and an apparatus for inspecting weld quality using sensors and images. The method includes receiving a dataset consisting of sensor values from a sensor module that is installed in a welding device and measures at least one of voltage, current, and gas flow rate, determining defectiveness according to a number of sensor values smaller than a lower limit value based on the lower limit value calculated from an average of the sensor values included in the dataset, receiving, when the defectiveness is determined, an image of a weld bead corresponding to the dataset, detecting a region of interest corresponding to a weld bead in the image, calculating dimensions of horizontal and vertical lengths of the region of interest, and determining defectiveness depending on whether the dimensions of horizontal and vertical lengths of the region of interest exceed preset thresholds for the horizontal and vertical lengths.

The invention provides a robust model parameter uncertainty quantification method. The method comprises the following steps: constructing a plurality of priori implementation subsets of a priori implementation set; calculating an expected range of the priori implementation subset in the data space; evaluating all expectations in the expectation range to obtain a plurality of posterior expectations and corresponding subsets; obtaining an upper limit and a lower limit of the posterior expectations from the plurality of posterior expectations; the uncertainty of the geological parameter is measured based on the upper and lower limits of the posterior expectation. According to the method, in an expected range calculation stage, the expected range is calculated in a data space only based on a priori realized subset, and forward modeling does not need to be repeatedly operated along with parameter updating, so that the calculation amount is greatly reduced. In addition, by obtaining a plurality of posterior expectations and related subsets thereof, the data value is further mined, and the uncertainty information of the geological parameters is captured more comprehensively and accurately.

The invention relates to an early warning method and system based on power plant side big data operation and maintenance. The method comprises the steps of collecting time sequence data of a power plant side; performing trend monitoring on the change rate of the measuring point data, comparing the measuring point data with the corresponding upper limit value and lower limit value, and performing limit value monitoring to obtain an absolute alarm result; setting a plurality of measuring point objects according to the experience of an operator to compare amplitude intervals or variation amplitudes, and performing combination through judgment logic to obtain a combined early warning result; carrying out screening and correlation verification on the selected measuring point data, selecting various measuring point data with strong correlation as parameters, taking a historical operation working condition as a sample, obtaining an abnormal change interval of each parameter under the working condition same as the current working condition, and carrying out comparison to obtain a relative alarm result; and performing closed-loop adjustment on each step according to an alarm result. Compared with the prior art, equipment early warning is completed from three angles, and the early warning accuracy and reliability of the power plant equipment are greatly improved.

A heater power configuration method based on dual-objective collaborative optimization belongs to a heating optimization technology, and is characterized by comprising the following steps: firstly, establishing a three-dimensional geometric model of a heater; then performing grid division on the three-dimensional model, defining material attributes of each part and setting reasonable boundary conditions; determining a target temperature and a temperature uniformity index; constructing an optimization model which takes the target temperature as an optimization target function and takes the temperature uniformity as a constraint condition; determining an initial value range of the power density of the heater by using a parameterized scanning function; calling a parameter optimization module in the multi-physics field coupling simulation software, and carrying out iterative optimization on the power density parameter; after optimization calculation is completed, whether temperature uniformity meets set requirements or not is judged, if not, the upper limit and the lower limit of the power density are adjusted in combination with a simulation result, optimization is conducted again, and finally the optimal power parameter is output. Accurate configuration of the power of the heater is achieved, and the uniformity of a temperature field and the energy efficiency of the system are remarkably improved.

The invention belongs to an SDTW-IPAM-based short-term power load prediction method and system, electronic equipment and a storage medium. The method comprises the steps of data preprocessing, clustering analysis, single-class prediction model construction and future load prediction. The clustering analysis comprises setting of upper and lower limits of a cluster number, construction of a distance matrix, calculation of a Gap value and a standard error, selection of an optimal cluster number, generation of an initial center, clustering processing and normalization processing; according to the method, a distance measurement method is introduced into load clustering, so that the dynamic time sequence characteristics of a load curve can be described more accurately, the local time deformation of the load curve can be effectively identified, and the distinguishing capability of similar load days under the influence of weather, events or potential new energy fluctuation is improved; a clustering algorithm is improved by using statistics and an initialization strategy, so that the stability and the accuracy of performing mode recognition on complex load data are improved, and the load can be effectively divided into typical modes with different dynamic characteristics.

The invention provides an extruder control method, device and system and an extruder. The control method comprises the steps that the production outer diameter of a target cable is detected in real time through an outer diameter collecting device; comparing the production outer diameter with a standard outer diameter range in real time; when the production outer diameter is smaller than the lower limit value of the standard outer diameter range, the rotating speed value of an extrusion screw of the extruder is increased; when the production outer diameter is larger than the upper limit value of the standard outer diameter range, the rotating speed value of the extrusion screw is reduced; when the production outer diameter is larger than or equal to the lower limit value of the standard outer diameter range and smaller than or equal to the lower limit value of the standard outer diameter range, the rotating speed value of the extrusion screw is kept unchanged; and controlling an extrusion screw to extrude the material according to the rotating speed value. The production outer diameter of the target cable is compared with the standard outer diameter range in real time, and then the rotating speed value of the screw is dynamically adjusted according to the comparison result, so that the material extrusion speed of the extruder is changed, and the production outer diameter of the target cable meets the standard outer diameter range.

The invention discloses a refrigeration control method based on inverter compressor control, which relates to the technical field of refrigeration equipment control, and comprises the following steps: acquiring operation data of a refrigeration system according to a preset period, and extracting a thermal response characteristic representing a cooling rate attenuation acceleration by performing differential processing on an indoor temperature; and calculating a thermal rebound sensitivity characteristic by combining the frequency change gradient. A thermal inertia potential energy index representing the heat storage load of the enclosure structure is generated through time domain accumulation processing, a nonlinear drift modulation model is constructed accordingly, and a virtual set temperature and a dynamic frequency lower limit value are generated. And finally calculating a basic adjusting frequency based on the virtual set temperature, and selecting the maximum value of the basic adjusting frequency and the lower limit value of the dynamic frequency as a target driving frequency. Through cooperation of algorithm soft traction and physical hard lifting, the problem of overshoot oscillation in a complex thermal environment is solved, and temperature control stability and energy saving performance are improved.

An error rate measurement apparatus includes a provisional confidence level calculation unit that calculates a provisional confidence level CLx by using the sum x, an upper and lower limit value update unit that substitutes the sum x for the variable min_x in a case where the provisional confidence level CLx is equal to or lower than a target confidence level CLs, and substitutes the sum x for the variable max_x in a case where the provisional confidence level CLx is higher than the target confidence level CLs, and a measurement time calculation unit that calculates, in a case where changes in a value of the sum x calculated by the average value calculation unit are converged in a predetermined range, a value obtained by dividing the converged sum x by a product of a data rate and a target error rate ERs, as the measurement time.

The invention relates to a power system uncertainty optimization scheduling method and system considering safety risks, and the method comprises the steps: constructing a risk measurement model considering faults and system states at the same time, and enabling the risk measurement model to be used for quantifying and evaluating the safety of a system; constructing a scheduling optimization model, taking minimization of ground state power generation cost, expected power generation cost and expected wind curtailment load shedding cost as a target function, and taking an alternating current power flow constraint, a unit output upper and lower limit constraint, a unit climbing constraint and a system comprehensive risk constraint under an original scene set and a fault as constraint conditions; reducing the original scene set by adopting a scene reduction method based on a Wasserstein distance; solving a scheduling optimization model based on the subtracted optimal typical scene set and the corresponding probability distribution; and performing system scheduling according to a scheduling scheme obtained according to a solving result. The method has a more obvious indication effect on the safety state of the system, meanwhile, the calculation speed of the scheduling optimization model is increased, and the engineering application requirement is greatly met.

The application relates to the field of photoetching technology, and particularly relates to a method and device for rapidly screening overlay mark manufacturability and computer equipment, which comprises the following steps: inputting preset range of process window conditions, selecting upper limit value and lower limit value as extreme process window conditions; calculating initial process variation bandwidth value based on the extreme process window conditions, and performing first screening on the initial process variation bandwidth value based on a preset screening ratio; calculating to-be-processed process window values corresponding to the screened process variation bandwidth values; performing second screening on the to-be-processed process window values based on a preset standard range to obtain final process window values; and screening the overlay marks corresponding to the final process window values. The application further provides a device and computer equipment. The problems of time and labor consumption in screening overlay mark manufacturability are solved.

The application discloses a method for determining the quality proportion of each grade based on the maximum utilization rate of cement gobi material, and belongs to the technical field of cement stabilized base. Firstly, the aggregate with a particle size greater than the maximum screen hole of a target grading is removed from the original gobi material, and the passing rate is normalized. According to the particle size from small to large, when the normalized passing rate B a of the first determined screen hole p a is not within the range of the set upper limit and the set lower limit of the passing rate, the first grade is set. The passing rate of each screen hole is corrected. According to the particle size from small to large, when the once corrected passing rate B b of the first determined screen hole p b修正1 is not within the range of the set upper limit and the set lower limit of the passing rate, the second grade is set. The passing rate of each screen hole is corrected. The grading is continued or stopped. The quality proportion of each grade is determined. The application can quickly determine the grading screen hole size with the maximum utilization rate of gobi material and the quality proportion of each grade under the condition that the specification requirements of the mixture grading are met.

The embodiment of the invention discloses an electric leakage detection method, device and equipment, a medium and a program product. Comprising the steps of obtaining a to-be-processed signal in an electric leakage judgment period; according to the to-be-processed signal, waveform peak points in the electric leakage determination period and peak left edge points corresponding to the waveform peak points are determined; determining every two adjacent peak left edge points as a peak left edge point group, and counting the total sampling number and the trough sampling number corresponding to each peak left edge point group; according to each total sampling number, each trough sampling number, a preset correction wave period sampling number lower limit value, a preset correction wave period sampling number upper limit value and a preset trough sampling number threshold value, determining a leakage waveform from correction waveforms corresponding to each peak left edge point group; and determining an electric leakage detection result according to the distribution condition of each electric leakage waveform in the electric leakage judgment period. The complexity and the data operand of a circuit required by electric leakage detection are reduced, and the stability and the universality of electric leakage detection are improved.

The present application belongs to the field of cold-rolled strip steel, and particularly relates to a method for dynamically setting bending roll force in a cold-rolled strip passing process, which comprises the number N of racks, upper and lower limits of the bending roll force of the i-th rack, dividing the strip passing process into n sections according to time, collecting the strip passing speed v of the i-th rack in the j-th section ij , dividing the bending roll force of each rack into m sections according to an adjustable area, collecting the shape value L calculated by a virtual shape meter on site ijk , calculating a shape evaluation function and a shape target function, setting an optimal bending roll force value S i0 , collecting the shape distribution value l calculated by the virtual shape meter on site ijk , calculating a shape evaluation function and a shape target function, setting an optimal bending roll force value S 0ij , establishing a function corresponding to the optimal bending roll force S 0ij and the strip passing speed v ij , and solving function coefficients a i1 , a i2 . The method for dynamically setting the bending roll force in the cold-rolled strip passing process can accurately control the dynamic setting of the bending roll force of the cold-rolled strip steel in the strip passing process, improve the strip passing shape, and reduce the rolling fluctuation caused by the shape defects.

This invention provides a method, apparatus, and electronic device for generating a sub-Brønsted bar frequency control scheme, relating to the field of power system technology. The method for generating the sub-Brønsted bar frequency control scheme includes: processing the inverse cumulative distribution function in the uncertainty set and the first frequency security constraint using a Gaussian mixture model and Wasserstein distance to obtain the lower limit value of the first frequency security constraint; substituting the lower limit value of the first frequency security constraint into the first frequency security constraint to obtain the second frequency security constraint; and solving the objective function based on the dynamic equation of the target power grid frequency and the second frequency security constraint to obtain the target control measure quantity that minimizes the control measure cost of the target power grid. This invention can provide an efficient, accurate, and highly adaptable emergency frequency control scheme to perceive the power grid status in real time, quickly respond to various disturbances and faults, and effectively coordinate various frequency regulation resources to ensure the frequency security of the power grid.

A method, system and apparatus are disclosed. A UE (22) is provided. The UE (22) is configured to: determine a configured maximum output power range having a lower limit and upper limit that are not based on a delta power class, DPC; and transmit a power headroom report, PHR, that comprises, when a duty cycle exceeds a threshold, at least an indication of the configured maximum output power range, where the indication of the configured maximum output power range comprises a reporting of a M-Delta Power Class, M-DPC, value that maps to a power management-maximum power reduction, P-MPR, range.

The invention belongs to a price determination method, and provides a method for determining upper and lower limits of contract price fluctuation of a power market and a related device, aiming at the technical problems that a price limit mechanism for setting fixed upper and lower limits of prices is adopted in the current power transaction, a price discovery suppression function exists, and violent price swing within a day cannot be effectively coped with. Calculating a positive excess sample and / or a negative excess sample, then taking the positive excess sample and / or the negative excess sample as input, and obtaining a morphological parameter and a scale parameter when a log-likelihood value of the positive excess sample and / or a log-likelihood value of the negative excess sample converges through generalized Pareto distribution iterative calculation; and finally, positive tail risk measurement index expected loss and / or negative tail risk measurement index expected loss are / is obtained through calculation and serve as an upper limit and a lower limit of contract price fluctuation of the electricity market. And the technical problem of violent price swing within the day can be effectively solved.

The present invention can reduce phase noise while characteristics of an oscillation device are addressed.　This oscillation device comprises: a field effect transistor that outputs an oscillation signal through the drain thereof; and a control unit that controls the oscillation amplitude of the oscillation signal on the basis of the source potential of the field effect transistor. The field effect transistor may operate as a negative resistor of an LC oscillator. In the case in which the field effect transistor is an N-channel field effect transistor, the control unit may control the oscillation amplitude in a direction in which the lower limit value of the oscillation amplitude approaches the source potential of the N-channel field effect transistor.