53 results about "Pulse mode" patented technology

The invention discloses a fault signal dual-mode output method of a magnetic latching relay, particularly relates to the technical field of relay control, and is used for solving the problem of low mode switching efficiency caused by an existing physical jumper mechanism. The current mechanical state of the relay is detected by receiving a remote dual-mode switching instruction; applying a driving voltage sequence corresponding to the target mode according to the state; based on the iron core residual magnetism intensity and the dynamic margin of a target mode nominal value, judging and generating a driving enabling or degaussing trigger signal; when a driving enable signal is responded, the lag time difference between the voltage rising edge and the magnetic flux jump starting point is captured in real time, and the eddy current loss characterization quantity is generated by combining the product integration of the current differential and the temperature rise; adjusting the rising slope and the duty ratio of the driving voltage sequence according to the lag time difference and the over-limit condition of the eddy-current loss characterization quantity; and finally, the matching between an execution result and a target mode identifier is verified by controlling a coil current response waveform, and the continuous holding mode and the instantaneous pulse mode are remotely and reliably switched.

The present application relates to the technical field of mechanical fault diagnosis, and particularly relates to an engine main bearing quantitative diagnosis method based on adaptive filtering and impact enhancement; comprising the following steps: S1, using a pulse mode decomposition method, carrying out pulse mode extraction, and obtaining a residual signal of the extracted pulse mode; comprising the following steps: S11, assuming a pulse mode, obtaining a pulse mode sparsity quantitative index of the pulse mode; S12, constructing an adaptive filter set, extracting the pulse mode according to the adaptive filter set, and thus obtaining a residual signal; S2, based on the residual signal obtained in step S1, reconstructing a signal of a signal collected by the engine main bearing, and obtaining a reconstructed pulse envelope; S3, according to the pulse envelope, obtaining a standard decibel of the impact pulse value, and according to the standard decibel, evaluating the health state of the main bearing; the effectiveness of the diagnosis of the aero-engine main bearing is improved.

The application discloses a kind of parallel random number generation devices based on pulse driving micro-ring resonator cavity, by adopting pulse mode driving micro-ring resonator cavity, improve the instantaneous power level in cavity, enhance nonlinear effect, to effectively expand the effective bandwidth of chaotic entropy source, improve the complexity of entropy source.Meanwhile, using the characteristics that micro-ring resonator cavity naturally supports multi-wavelength output, and combining with filter demultiplexing structure, the parallel output of multiple chaotic entropy sources is realized, which is beneficial to improve the parallel generation ability of random number.Finally, by combining post-processing methods such as difference, quantization and decorrelation, the overall generation rate of random bits is improved while ensuring randomness quality.The application has relatively simple structure, is suitable for integrated implementation, and can meet the application requirements of high-speed parallel random number generation.

The invention provides a dynamic frequency scanning method based on a radio frequency power supply pulse mode and related equipment, and relates to the technical field of radio frequency power supplies. The method comprises the following steps: acquiring an initial control parameter; monitoring the operation mode of the radio frequency power supply in real time, and iteratively adjusting the output frequency of the radio frequency power supply based on the dynamically adjusted frequency step length when the radio frequency power supply is in a pulse mode so as to determine the optimal frequency which enables the radio frequency power supply to realize impedance matching and enables the reflection coefficient to be minimum; and controlling the radio frequency power supply to operate at the optimal frequency. The method aims at solving the problems that in the prior art, when a radio frequency power supply is in a pulse mode, dynamic change of load impedance causes that a traditional impedance matching method is difficult to adapt rapidly, and then power transmission efficiency is affected, reflection power is increased and energy consumption is increased, scanning can be completed rapidly and stably, impedance matching and low reflection power are achieved, and the power transmission efficiency is improved. And the excitation accuracy of the radio frequency plasma is improved.

Systems and methods for interrogating a plurality of backscatter node devices in a wireless backscatter communication system are provided. The method may include transmitting one or more interrogator pulse signals from an interrogator device; for each of the one or more interrogator pulse signals, receiving at the interrogator device a raw backscatter signal including individual backscatter signals from each of the plurality of backscatter node devices, wherein each individual backscatter signal includes a reflection of the interrogator pulse signal modulated based on an input modulation signal of the respective backscatter node device; processing the one or more raw backscatter signals to determine a mapping model between the input modulation signal of each of the plurality of backscatter node devices and the one or more raw backscatter signals; and extracting one or more signals of interest based on the mapping model, wherein each signal of interest corresponds to an input modulation signal of a backscatter node device.

The application discloses a semiconductor process equipment and a pulse-regulated plasma method thereof, and belongs to the technical field of semiconductor processes. The pulse-regulated plasma method comprises the following steps: setting a first pulse to control synchronous opening and closing of a high-frequency radio frequency power supply and a low-frequency radio frequency power supply through the first pulse; setting a second pulse to sequentially form a plurality of different power control periods in each radio frequency cycle of the low-frequency radio frequency power supply through the second pulse; and adjusting power amplitude of the high-frequency radio frequency power supply to different power values in the different power control periods to regulate plasma of the semiconductor process equipment. According to the technical scheme, the power amplitude of the high-frequency radio frequency power supply in different stages is changed to form different pulse modes in each radio frequency cycle of the low-frequency radio frequency power supply, so that different etching requirements of products can be met.

The system is used for detecting and evaluating the influence of a water film formed on the outer surface of the windshield glass on the definition of the windshield glass, and is characterized by comprising a water film thickness detection device arranged on the inner surface of the cockpit side of the windshield glass and used for detecting the thickness of the water film formed on the inner surface of the cockpit side of the windshield glass. The infrared detector can emit infrared light towards the outer surface side of the windshield glass in a pulse mode and receive reflected infrared light as a detection signal. The control device sends a control signal to the water film thickness detection device and can drive the water film thickness detection device to emit infrared light at a specified frequency through the control signal; and the calculation device receives the detection signal from the control device or the water film thickness detection device, and can determine a definition index capable of representing the definition of the windshield glass as a calculation result based on the detection signal. Therefore, the influence of the water film formed on the outer surface of the windshield glass on the definition of the windshield glass can be detected and evaluated in real time.

The application discloses a control method of a tubular PECVD film coating device, a solar cell film layer preparation method and a solar cell. The control method of the tubular PECVD film coating device comprises the following steps: during the common operation of a first radio frequency power supply and a second radio frequency power supply, the first radio frequency power supply and the second radio frequency power supply work in a pulse mode, a part of rising edges of the first radio frequency power supply does not coincide with at least a part of rising edges of the second radio frequency power supply, the transient electric field between two graphite boats can be avoided from being too large, and the process gas can be prevented from being ionized to form powder in the too large transient electric field, on the basis, the pulse width of the first radio frequency power supply and the pulse width of the second radio frequency power supply are partially overlapped, and the synergistic effect is enhanced.

This invention discloses a control method and system for permanent magnet synchronous motors based on adaptive weights in gradient prediction pulse modes. The method includes: 1) establishing a discretized current gradient prediction model considering delay compensation and motor DC voltage feedback, and reconstructing a reference current trajectory with harmonic characteristics using a nominal optimized pulse mode; 2) designing a degree-of-freedom control logic based on nonlinear mapping to address the performance mismatch problem caused by fixed weights in the prediction cost function; and 3) dynamically adjusting the weighting factor by evaluating the normalized composite index of motor torque and current in real time. During acceleration transients, low weights are used to release the degrees of freedom at the pulse switching moment of the three-phase inverter, accelerating motor torque establishment. During steady-state cruise, high weights are used to strengthen the inverter pulse position constraint, locking in the optimal harmonic distribution. This invention solves the problem of balancing dynamic response and steady-state harmonics in permanent magnet synchronous motors, significantly improving the transient quality and voltage disturbance robustness of the motor control system.

The application discloses a high-frequency pulse DC power output stability control device and belongs to the technical field of power supply control. The device proposes a state zeroing-knowledge injection control paradigm for the contradiction between overshoot and slow response after reset of the traditional controller in the pulse mode due to integral memory. At the starting moment of each pulse period, a pulse opening instruction is generated and a reset signal is generated with a delay, the integral capacitor is forced to discharge to make its output zero, and the overshoot risk is eliminated; according to the load current steady-state value collected during the last pulse off period and the current target duty cycle, a feedforward control value is determined; in the same control period when the integral value is zeroed, the feedforward value and the integral output value are added to generate a drive control signal, and finally the drive power switch output pulse current is modulated. Through the cooperation of physical state forced zeroing and system knowledge cross-period prediction injection, the application realizes the rapid and non-overshoot establishment of the pulse current, and effectively solves the dynamic performance bottleneck of the high-frequency pulse power supply.

The application discloses a kind of cooling method, device, magnetic suspension motor of magnetic suspension motor, storage medium and computer program product, motor winding of magnetic suspension motor is equipped with coolant pipeline, and electronic expansion valve is equipped on coolant pipeline;The method comprises: after magnetic suspension motor starts to work, the target opening of electronic expansion valve is determined according to the temperature of motor winding;Pulse mode is used to power on electronic expansion valve, and the energization time of electronic expansion valve is controlled according to the action frequency of electronic expansion valve, so that the opening of electronic expansion valve reaches the target opening while reducing the energization time of electronic expansion valve, reduce the heat at the place of electronic expansion valve.The scheme, by pulse mode to power on electronic expansion valve, and the energization time is controlled according to the action frequency of electronic expansion valve, so that the energization time of electronic expansion valve is reduced, the heat at the place of electronic expansion valve is reduced, avoid electronic expansion valve high temperature failure, ensure that magnetic suspension motor is stably operated.

The application provides a six-pulse positioning method, a motor driving control method, a module and a system, which comprise a motor control sequence generator, a programmable motor driver and an analog-to-digital converter; the motor control sequence generator outputs a preset six-pulse wave sequence one by one based on a first trigger signal output by the programmable motor driver in a six-pulse mode, and provides a duty cycle control signal and an upper and lower phase output mode control signal; the programmable motor driver is connected to the output end of the motor control sequence generator, and generates a corresponding PWM signal based on the output signal of the motor control sequence generator; and the analog-to-digital converter collects the total motor current of each cycle of the PWM signal in the six-pulse mode, and then calculates the current rotor position according to the current information. The application has low cost, short code length, small program complexity and simple operation steps.

The application relates to the field of sintering machine head electrostatic dust removal, and provides a sintering machine head electrostatic dust removal system which comprises an airflow homogenizing unit, an electric field dust removal unit, a high-frequency pulse power supply unit, an intelligent control unit and a dust concentration detector; the airflow homogenizing unit is arranged before the electric field dust removal unit; the high-frequency pulse power supply unit is signal-connected to the electric field dust removal unit; the intelligent control unit is signal-connected to the electric field dust removal unit and used for controlling the voltage of the electric field dust removal unit; the dust concentration detector is arranged at an outlet position of the electric field dust removal unit, the dust concentration detector is used for detecting the outlet dust concentration of flue gas at the outlet position of the electric field dust removal unit and sending the outlet dust concentration to the intelligent control unit; the intelligent control unit is signal-connected to the high-frequency pulse power supply unit, and when the outlet dust concentration is greater than 20 mg / Nm3, the pulse mode of the high-frequency pulse unit is activated; a sintering machine head electrostatic dust removal method is also provided; and the application has the effects of improving the efficiency and effect of electrostatic dust removal.

The invention discloses a double-wire double-pulse MIG welding power supply system based on fractional calculus. The double-wire double-pulse MIG welding power supply system comprises a host power supply, a slave power supply, a DSP control module, a master wire arc load and a slave wire arc load. One end of the host power supply is connected with a three-phase AC power grid, and the other end is connected with the main wire arc load. One end of the slave power supply is connected with the three-phase alternating current power grid, and the other end is connected with the slave wire arc load; the host power supply and the slave power supply are respectively connected with the same DSP control module, and the DSP control module is integrated with a fractional calculus control module; and the fractional calculus control module outputs four paths of pulse width modulation (PWM) signals to respectively control on and off of a switching tube of the host power supply and a switching tube of the slave power supply, so that the system enters a double-pulse mode to work. Complex nonlinear and time-varying dynamic characteristics of a welding arc and a molten pool system can be described and matched more accurately.

The invention discloses a Wi-Fi intelligent flowerpot based on an STM32 microcontroller and an intelligent plant maintenance method. The intelligent flowerpot comprises a pot body assembly, an environment sensing module, a main control unit, an execution mechanism module and a communication unit. The main control unit carries out calibration, filtering and compensation correction on the original data of the sensor through the data preprocessing module; calculating a soil humidity reduction rate, an evaporation trend and an illumination change gradient through a trend prediction module; and performing intelligent decision making by integrating the environmental parameter value and the change trend through a multi-factor coupling decision making module, and generating a control instruction. And the execution mechanism module carries out irrigation and segmented PWM light supplement execution according to a pulse mode. And the communication unit supports cloud interaction and is seamlessly switched to a local intelligent control mode when the network is disconnected. According to the invention, high-precision perception, feedforward prediction maintenance, multi-factor coupling intelligent decision and precise execution are realized, and the problems of rough perception, decision lag, extensive execution and dependence on the cloud end of the existing intelligent flowerpot are effectively solved.

The present invention discloses a two-degree-of-freedom predictive control method for an LCL filter-type three-phase grid-connected inverter system, belonging to the field of power electronic converter control. A predictive control reference instruction is obtained by sampling the parameters of the inverter-side current, capacitor voltage, grid-side current, and grid voltage at time k, and a continuous and discrete model of the LCL filter-type three-phase grid-connected inverter system is established. A control function based on the grid-side current reference tracking error and its gradient is designed, and a predictive model is established. A predictive cost function based on the control function is constructed, and the predictive control reference instruction is obtained using the minimum value of the predictive cost function. The optimal voltage vector and action duty cycle are then determined based on the predictive control reference instruction, and a control pulse signal is generated according to a symmetrical five-segment pulse mode. The control pulse signal acts on each switch tube in the inverter to achieve predictive control of the LCL filter-type three-phase grid-connected inverter system. The method has simple steps, is easy to use, has a constant switching frequency, and has good stability.

The invention belongs to the technical field of radiation detection, and particularly relates to a wide-range pulse radiation sensitive radiation detection unit which comprises a Si-PIN detector (1) provided with an N-type end and a P-type end, the N-type end is connected with a bias power supply (2) and a charge sensitive pre-amplifier (4), the P-type end is connected with the input end of a current amplifier (5), and an operational amplifier is arranged in the current amplifier (5); and the bias power supply (2) is used for providing working bias voltage for the Si-PIN detector (1). According to the invention, a single Si-PIN detector is adopted to work in a pulse mode and a current mode at the same time, and the charge-sensitive pre-amplifier (4) and the current amplifier (5) are matched to complete measurement of pulse signals and current signals at the same time, so that integration and miniaturization of wide-range dose rate measurement and pulse radiation measurement units are realized; the use of Si-PIN detectors is significantly reduced, and the manufacturing cost is further reduced.

An arc fault circuit interrupt (AFCI) tester device includes a housing and a circuit assembly disposed within the housing. The circuit assembly includes a first load switching circuit for creating a pulse pattern having a plurality of pulses. The circuit assembly includes a second load switching circuit for creating an overlay signal superimposed upon at least one pulse of the plurality of pulses. The AFCI tester device includes an interface receiving the plurality of pulses and the overlay signal. The interface extends outside of the housing and is adapted for electrically coupling the circuit assembly to the AFCI device under test (DUT). The interface is adapted to transmit the pulse pattern and the overlay signal to the AFCI DUT.

The invention relates to the technical field of mechanical fault diagnosis, in particular to an engine main bearing quantitative diagnosis method based on adaptive filtering and impact enhancement. Comprising the following steps: S1, performing pulse mode extraction by using a pulse mode decomposition method, and obtaining a residual signal of the extracted pulse mode; comprising the following steps: S11, assuming a pulse mode, and obtaining a pulse mode sparsity quantitative index of the pulse mode; s12, constructing a self-adaptive filter bank, and extracting a pulse mode according to the self-adaptive filter bank so as to obtain a residual signal; s2, based on the residual signal obtained in the step S1, performing signal reconstruction on a signal acquired by the main bearing of the engine to obtain a reconstructed pulse envelope; s3, obtaining the standard decibel of the impact pulse value according to the pulse envelope, and evaluating the health state of the main bearing according to the standard decibel; and the diagnosis effectiveness of the aero-engine main bearing is improved.

The invention relates to the technical field of predictive health management of electronic equipment, and discloses a cross-domain data analysis method and system for charger service life prediction.The cross-domain data analysis method for charger service life prediction.The method comprises the steps that high-frequency event stream data and charging stage identification in the fast charging process are obtained, generating an original event timestamp and amplitude data; converting the continuous signal into a pulse sequence by using a pulse encoder; integrating the time domain pulse mode and the frequency domain wavelet coefficient through a pulse-wavelet dual-channel fusion device, and outputting collaborative coding representation; inputting the collaborative features into a domain discriminator of stage perception, and generating stage transition probability distribution; and according to prediction error feedback, updating a pulse coding parameter and a wavelet basis selection strategy, and outputting an adaptive improved final prediction result. The technical problem that the influence of a transient event is difficult to transmit to long-term degradation prediction and the problem that the prediction precision is reduced due to domain offset in the charging stage are solved.

The application discloses a kind of double three-phase permanent magnet synchronous motor system low current ripple prediction control methods, belong to permanent magnet motor control technical field.First, construct the mathematical model of double three-phase permanent magnet synchronous motor based on vector space decoupling coordinate system;Using first-order forward Euler discrete method to establish discrete model;Pre-combine 12 candidate virtual voltage vector sets of inverter;Based on the least tracking target calculation voltage command, select the optimal voltage vector pair closest to it;Define the duty cycle of each vector, construct the prediction target function of stator current prediction tracking error;Solve the function, get the optimal duty cycle of optimal voltage vector pair and zero vector;Convert the optimal duty cycle into physical action time, generate PWM switching signal to drive inverter using symmetric 6 segment pulse mode.The application method is simple, the amount of calculation is small, can effectively suppress stator current ripple, reduce system current ripple, improve system steady control precision.

The utility model discloses a high-voltage power supply circuit for a double-pulse test. The high-voltage power supply circuit comprises a single-pulse generator, a high-voltage storage capacitor, a first IGBT, a second IGBT, a third IGBT, a fourth IGBT, a fifth IGBT, a sixth IGBT, a first inductor, a voltage source, a low-voltage energy storage capacitor, a second inductor, an insulated gate bipolar transistor and a diode. Through the above mode, the test power supply has a soft switching function effect, can realize automatic switching of the test power supply, avoids operation danger caused by manual switching, and does not need additional switching devices, so that the power supply is relatively compact in structure and relatively small in size, operates in a monopulse mode, reduces heat productivity, does not need heat dissipation, and is convenient to use. And the overall power supply volume can be further reduced.

The application is a control method of constant temperature circuit of sensor, comprising the following steps: the circuit controller acquires information including initial ambient temperature, sensor structure parameters and historical heating response curve, establishes a temperature rise prediction model based on the information, and outputs temperature rise rate at multiple power levels; in the temperature rise starting stage, the circuit controller selects a target power level according to the prediction model, controls the heating element to be alternately turned on and off in a pulse mode with a first period 1, and realizes stepwise temperature rise; the application has the beneficial effects that: by dividing the sensor heating process into three stages of exploratory preheating, stepwise temperature rise and steady state maintenance, and combining real-time temperature sampling, dynamic modeling and control function feedback control, the sensor temperature can be accurately and stably controlled in the target temperature zone, which is much better than the traditional single-link constant voltage control method, ensures that the sensor works under the best thermal conditions, and improves the detection accuracy and repeatability.

The invention relates to the technical field of DTP-PMSM pulse width modulation, and discloses a prediction model for smooth switching of different pulse modes, which is provided with a current impact mathematical model of a DTP-PMSM system in the switching process of different pulse modes and a current prediction model of the DTP-PMSM system on the basis of unified modeling of output voltages of SVPWM and OPP pulse modes. The current impact mathematical model is constructed based on a voltage-current relation of an ABC three-phase winding and an XYZ three-phase winding of the DTP-PMSM under a two-phase rotating coordinate system, the current prediction model is established based on a DTP-PMSM system transfer function comprising a single L filter, discretization processing is carried out by adopting a bilinear discretization method, common-mode voltage components are ignored, and the current impact mathematical model and the current prediction model are integrated. And a current iterative calculation formula under the two-phase rotating coordinate system is obtained. The invention also discloses a method for smoothly switching different pulse modes. According to the prediction model for smooth switching of different pulse modes and the switching method, the current impact during switching is minimized, and the system performance and reliability are improved.

A plurality of active buffer assemblies and a flexible protective cover are arranged on the collision face of an anti-collision frame of the anti-collision vehicle in an array mode, and an optical fiber strain sensor is arranged on the flexible protective cover; the active buffer assembly comprises a mounting seat; a magnetic field generating device; the explosion-proof bag is filled with magnetorheological fluid; the buffer controller is configured to determine a rear vehicle collision main area and collision side areas located on the two sides of the collision main area based on signals of the optical fiber strain sensors. A plurality of magnetic field generating devices corresponding to the impact main area are controlled to work in a first pulse mode, so that the rigidity of the corresponding anti-explosion bag is alternately switched between a first rigidity level and a second rigidity level, and the first rigidity level is higher than the second rigidity level; and synchronously controlling the plurality of dry magnetic field generating devices corresponding to the impact side areas on the two sides to work in a second pulse mode, wherein the first pulse mode and the second pulse mode are opposite in phase. According to the invention, dynamic buffering and transverse movement secondary impact prevention can be realized.

The application provides a kind of detector signal processing circuit and detector signal processing method, applied in nuclear technology application field, detector signal processing circuit, comprising: detector is used to generate detection signal;Pulse mode circuit is connected with detector, pulse mode circuit is used to pulse shaping to detection signal, obtains pulse signal;High-order mode circuit includes multiple parallelly connected Campbell modules, the input end of Campbell module is connected with detector, and Campbell module is used to convert detection signal into first-order signal;Current mode circuit is connected with detector, and current mode circuit is used to convert detection signal into current signal;Control module is connected with pulse mode circuit, current mode circuit, the output end of each Campbell module respectively.This embodiment can improve the accuracy of neutron flux detection result, and expand the measurement range of detector.

The embodiment of the present application provides a kind of power source control method and system based on adaptive sampling, by the original signal provided by the external signal source is detected by preset time period after the external signal source is opened, and signal sampling mode is adjusted to target signal sampling mode according to detection result, the signal sampling mode includes continuous wave mode, pulse mode.The original signal is sampled by the target signal sampling mode, and the sampling data of the original signal is obtained.According to the sampling data, the pre-configured signal processing parameter is calibrated, and the calibrated target signal processing parameter is obtained, the signal processing parameter includes signal amplification parameter, power adjustment parameter, timing control parameter.According to the target signal processing parameter, the original signal is processed, and target signal is obtained and output.Thereby, the adaptability and stability of power source control equipment in different working environments are improved.

The invention relates to the field of semiconductor equipment, and provides a pulse air supply type air floatation device and an air floatation control method.The pulse air supply type air floatation device comprises a base, an air floatation plate, a pulse electromagnetic valve array, a sensor and a controller, the air floatation plate is arranged on the base, and the air floatation plate is provided with an air hole array; the pulse electromagnetic valve array is arranged in the base, and an outlet of each pulse electromagnetic valve is in fluid connection with one or more air outlet holes in the air hole array; the at least one sensor is configured to detect floating state information of the glass substrate in real time, and the floating state information comprises at least one of height, vibration frequency and phase; the controller is in signal connection with the at least one sensor and the pulse electromagnetic valve array, and the controller is configured to control the pulse electromagnetic valve array to work in a preset pulse mode based on the floating state information so as to adjust the rigidity and thickness of an air film between the glass substrate and the air floating plate.

The present application belongs to the technical field of powder material conveying and metering, and in particular to a weight-reducing feeder anti-wall-sticking intelligent control system for viscous materials and a control method thereof; comprising: a material characteristic identification module for obtaining or inputting at least one characteristic parameter of the viscosity level, critical relative humidity or rest angle of the material to be fed; a pulse mode library module, which is pre-set with at least two pulse working modes with different pulse intensity levels, each mode corresponding to a set of pulse parameters, the pulse parameters including pulse period, pulse pressure and pulse waveform; through a partition control module, differentiated pulse control signals for the upper and lower regions of the hopper are respectively generated, realizing accurate management of the electrostatic adsorption dominant area and the shear bridging dominant area, the wall cleaning efficiency being improved by more than 40% compared with single-zone uniform control, and the adverse effects of global high-intensity impact on the material filling state being avoided.

A method for characterizing in pulse-mode a III-V semiconductor transistor (2) utilizes an associated test bench (1). An RF pre-pulse is applied to the gate (2a) of the transistor (2) with a power level NRF defined according to a first predetermined law of variation so as to fix the charge state of the traps in the transistor (2). Then a first DC pulse and a second DC pulse are applied to the gate (2a) and to the drain (2b) of the transistor (2), respectively. The first DC pulse and the second DC pulse have a first DC level N1 and a second DC level N2, respectively, defined according to a second predetermined law of variation.