1082 results about "Phase locking" patented technology

A frequency determination circuit generating a clock signal phase-locking with an external clock signal at a coarse precision and a fine adjust circuit generating an internal synchronizing signal phase-locking with the external clock signal at a fine precision are provided. The fine adjust circuit has a function of adjusting the phase of the frequency determination circuit when phase synchronization is to be carried out exceeding the adjust range thereof. The frequency determination circuit and the fine adjust circuit receive a clock power supply voltage. A clock reproduction circuit is provided which generates an internal clock signal phase-locking with an external clock signal or a reference clock signal stably even when the operating environment changes.

Plasma distribution is controlled in a plasma reactor by controlling the phase differences between different RF coil antennas, in accordance with a desired or user-selected phase difference, by a phase-lock feedback control loop.

The present invention provides an improved method and apparatus for independently controlling phase and frequency using an oscillator having a plurality of stages in combination with a phase selector within a digitally controlled phase-locked loop, preferably, a read phase locked loop. The present invention provides a digitally controlled variable phase of the read timing loop in read channel integrated circuits associated with data storage devices. The phase selector has a digitally controlled fine interpolator with 12 states for further fine interpolation between at least two multiplexer phase outputs to provide a single phase output selected from a range comprising at least 2pi in selectable variable phase increments of 2pi/96 radian. The combined oscillator with the phase selector within a phase locked loop controls phase by exact fractional increments of equally space phases of the operating frequency within the phase locked loop, therein controlling phase at all operating frequencies.

A clock system includes a digital phase/frequency detector (DPFD), a buffer, a digitally-controlled oscillator (DCO) including a sigma-delta modulator (SDM), an adder, a first frequency divider. The DPFD may have a first input for a reference input clock and a second input for a feedback signal, and outputting a difference signal representing a phase and/or frequency difference between the reference input clock and the feedback signal. The buffer may be coupled to the DPFD for accumulating the difference signal over time. The sigma-delta modulator (SDM) may have a control input coupled to the buffer. The adder may have inputs coupled to the (SDM) and a source of an integer control word. The first frequency divider may have an input for a clock signal and a control input coupled to the adder, the DCO generating an output clock signal having an average frequency representing a frequency of the input clock signal divided by (N+F/M), wherein N is determined by the integer control word and F/M is determined by an output of the SDM. The system clock also may include a phase-locked loop (PLL) including a phase/frequency detector that has a first input coupled to the output of the DCO and a second input that is phase-locked to the first input, and a second frequency divider coupled from the second input of the PLL to the second input of the DPFD.

A parallel redundant power system and a method for control the same, wherein the power system is composed by UPS modules with outputs coupled in parallel to supply power to a load through a bus. The control method employs the P-omega and Q-V slope lines of the droop method to perform phase locking and current sharing. Moreover, the method further utilizes the internal impedance of the UPS in accompaniment with a current shift method to simulate an actual inductor being coupled to the output of the UPS module so as to satisfy the droop method. Therefore, the drawbacks otherwise caused from actual inductors such as the large size and heave weight are eliminated.

A bias generation method or apparatus defined by any one or any practical combination of numerous features that contribute to low noise and/or high efficiency biasing, including: having a charge pump control clock output with a waveform having limited harmonic content or distortion compared to a sine wave; having a ring oscillator to generating a charge pump clock that includes inverters current limited by cascode devices and achieves substantially rail-to-rail output amplitude; having a differential ring oscillator with optional startup and/or phase locking features to produce two phase outputs suitably matched and in adequate phase opposition; having a ring oscillator of less than five stages generating a charge pump clock; capacitively coupling the clock output(s) to some or all of the charge transfer capacitor switches; biasing an FET, which is capacitively coupled to a drive signal, to a bias voltage via an “active bias resistor” circuit that conducts between output terminals only during portions of a waveform appearing between the terminals, and/or wherein the bias voltage is generated by switching a small capacitance at cycles of said waveform. A charge pump for the bias generation may include a regulating feed back loop including an OTA that is also suitable for other uses, the OTA having a ratio-control input that controls a current mirror ratio in a differential amplifier over a continuous range, and optionally has differential outputs including an inverting output produced by a second differential amplifier that optionally includes a variable ratio current mirror controlled by the same ratio-control input. The ratio-control input may therefore control a common mode voltage of the differential outputs of the OTA. A control loop around the OTA may be configured to control the ratio of one or more variable ratio current mirrors, which may particularly control the output common mode voltage, and may control it such that the inverting output level tracks the non-inverting output level to cause the amplifier to function as a high-gain integrator.

A clock generator including a frequency multiplier, a phase lock circuit and a frequency divider. The frequency multiplier generates a frequency multiplied clock by multiplying the frequency of an input clock. The phase lock circuit detects a phase difference between the input clock and a frequency divided clock, and generates, by delaying the frequency multiplied clock by an amount corresponding to the phase difference, a phase-locked clock with its phase locked with the input clock. The frequency divider detects in every fixed cycle a particular pulse of the phase-locked clock, and generates the frequency divided clock by dividing the phase-locked clock with reference to the particular pulse of the phase-locked clock. In particular, the frequency divider detects the particular pulse immediately previous to a falling edge of the input clock. This can reduce the phase difference between the input clock and the phase-locked clock, and hence to solve a problem of a conventional clock generator in that a delay time of a digital delay line in a phase lock circuit must be lengthened with a reduction in the multiplication number of the frequency multiplied clock, which requires a greater number of delay elements because of a large occupying area of the delay elements and a decoder, thereby increasing the circuit scale and cost of a chip to reduce the multiplication number of the frequency multiplied clock.

The invention belongs to the technical field of gas detection and relates to a laser infrared gas analyzer based on TDLAS-WMS (tunable diode laser absorption spectroscopy-wavelength modulation spectroscopy) for detecting hydrogen chloride, methane, carbon monoxide, water vapor and other gases. The laser infrared gas analyzer comprises a laser, a laser driving circuit, a temperature control circuit, an optical system with an optical cavity, a main detector, a reference detector, an intensity modulation and canceling circuit, a phase-locking and amplification circuit and a data acquisition and display circuit, wherein the laser driving circuit and the temperature control circuit are used for controlling the laser to emit light, the two ends of the optical system are respectively connected with the laser and the detector, the intensity modulation and canceling circuit is used for canceling the influence of intensity modulation in the system, the phase-locking and amplification circuit is used for extracting harmonic signals, and the data acquisition and display circuit is used for displaying the concentration of the gas to be detected. Compared with other detection instruments, the laser infrared gas analyzer has the advantages that division operation is introduced into the intensity modulation and canceling circuit, and the laser infrared gas analyzer is combined with a space double-optical path differential detection method, so that the influence of the intensity modulation can be fundamentally canceled.

The device and method for phase-locking brain stimulation to electroencephalographic rhythms improves the accuracy, specificity, and effectiveness of non-invasive brain stimulation devices by timing pulses of brain stimulation to occur in synchrony with naturally occurring brain rhythms measured at the scalp of a patient in order to treat an assortment of neurological and psychiatric conditions. The device and method provided herein improve non-invasive brain stimulation techniques by time-locking the onset of brain stimulation to the phase of naturally-occurring rhythmic oscillations of brain activity that can be recorded with electroencephalography (EEG). The device and method perform real-time signal analysis of a specified EEG rhythm, extract frequency-domain phase information to estimate the next occurrence of a desired EEG rhythm phase, and trigger a brain stimulation pulse so as to align precisely with this predicted EEG phase.

The invention relates to a precise tracking and measuring method of a high dynamic signal of an air fleet link, belonging to the technical field of aeronautical data links and radio navigation, and aiming at providing a precise tracking and measuring method of the high dynamic signal the an air fleet link and an implementation structure to solve the problems in the prior art. The invention provides a system framework of the precise tracking and measuring method of the high dynamic signal of the air fleet link, which can be implemented on a digital signal processor (DSP) and a FPGA (field programmable gate array) of a circuit board, and overcomes the defects of the unfavorable precision of a traditional high dynamic receiver by utilizing a double-loop structure of a frequency tracking loop of carrier tracking and a phase locking loop as well as a code phase locking loop to realize the high precise tracking under a high dynamic condition. The method can be widely applied to satellite navigation receivers, range measurement systems and communication systems based on a quiescent carrier modulation direct sequence spread spectrum system.

The invention discloses a fire scene multi-parameter laser wavelength modulation spectrum detection method and a device thereof, wherein, fire smoke products are treated through a smoke pre-treatment device and then pumped into a white cell through an air extracting pump; a multi-channel laser controller scans and modulates the wavelengths of a plurality of DFB lasers according to the time-sharing and multiplexing working mode, and all waves of laser share an optical fiber and are outputted sequentially through a wave combiner, then are aligned by a fiber collimator and sent to the white cell to detect the fire smoke products; a photoelectric detector converts light intensity signals of laser repeatedly reflected and absorbed by the white cell into electrical signals which are sent to two phase-locking magnifier modules for frequency selecting magnification so as to obtain a fundamental frequency component and a second harmonic component; a multi-channel data acquisition card converts output voltage signals of the phase-locking magnifiers into digital signals which are sent to a micro-computer for real-time data processing, so that the fire scene multi-parameter information containing the oxygen concentration of the fire scene, concentrations of various toxic gases and smoke concentration is obtained. The detection method and device can realize real-time on-line monitoring to fire scene multi-parameters, and have the advantages of being real-time, multi-component and highly sensitive, good selectivity of gas, high reliability and strong environmental disturbance resistance ability.

A method for effective injection seeding is based on continuous wavelength sweeping for matching the injected seeds with one or more longitudinal mode(s) of the slave oscillator in every pulse. This is achieved through rapidly varying laser drive current, as a result of RF modulation. Depending on the modulation parameters, the seeder may be operated in CW or quasi-CW or pulsed mode, with a narrow or broad bandwidth, for injection seeding of single longitudinal mode or multimode. The wavelength and bandwidth of the laser output can be tuned according to the needs. Injection seeding of high repetition rates is achievable. From pulse to pulse, the master-slave resonance persists though may occur at different longitudinal modes upon cavity length fluctuations. Cavity length control and phase locking schemes are consequently not required. The present invention also encompasses an injection seeding laser system, which is constructed in accordance with the inventive method, and a novel application of RF modulated laser diode to spectrum/wavelength control and to producing high power Gaussian beam with narrow pulse width in a stable, reliable, and cost-effective manner.

The invention relates to a portable SF6 gas resolvent photoacoustic spectrum detecting device and method which have the advantages of being high in sensitivity, capable of automatically achieving detection and concentration conversion, fast in detection speed, high in accuracy, easy to carry and suitable for online monitoring. A paraboloid column mirror is arranged in a casing, and an infrared source is arranged on the paraboloid column mirror. A chopper, an optical filter wheel and a photoacoustic cell are arranged in front of the paraboloid column mirror, and a plurality of optical filters are evenly distributed on the optical filter wheel along the circumferential direction. The photoacoustic cell comprises a microtone device, an air pressure sensor and a temperature sensor and connected with an air pipe and a vacuum pipeline which is connected with a vacuum pump. The chopper is connected with a chopper controller, the optical filter wheel is connected with a singlechip microcomputer, the microtone device is connected with a phase-locking amplification module, the air pressure sensor is connected with the singlechip microcomputer, the temperature sensor is connected with an analog/digital (A/D) converter which is connected with the phase-locking amplification module, and the singlechip microcomputer is further connected with a liquid crystal driving and display screen and a working power source.

A method, comprising detecting, in at least a first brain region of a patient, an electrical activity relating to an epileptic activity; determining a first regularity index of said electrical activity; and applying at least one first electrical stimulation to at least one neural target of said patient for treating said epileptic event, in response to said first regularity index being within a first range. A non-transitive, computer-readable storage device for storing instructions that, when executed by a processor, perform the method. A medical device system suitable for use in the method.

The invention discloses a control method of a three-phase grid-connected inverter based on a modified proportional resonant regulator. The method comprises the following steps of: firstly, computing according to given active and reactive powers of the inverter and a voltage of a power grid to obtain required d-axis and q-axis currents under a synchronous coordinate system, and performing coordinate transformation by combining with phase information which is measured by a phase locking loop and a measured three-phase voltage signal of the power grid to obtain a current reference signal under a stationary alpha-beta coordinate system; secondly, performing coordinate transformation on an output current signal of the inverter to the alpha-beta coordinate system, controlling and tracking the current reference signal by the modified proportional resonant regulator with a harmonic compensator; and finally, returning to an abc coordinate system by coordinate transformation to generate a pulse-width modulation (PWM) pulse-control three-phase full-bridge inverter output, so as to make a distributed generation system grid-connected for power generation. By the method, a large number of complicated computation processes are eliminated, and a control structure is simplified. The control method of the three-phase grid-connected inverter based on the modified proportional resonant regulator is an accurate and high-efficiency novel inverter control method and has a bright development future.

The invention relates to a rapid locking method for a full digital phase-locked loop, which is used for locking the frequency of the full digital phase-locked loop comprising a phase detection discriminator, a time-to-digit converter, a digital filter, a digital controlled oscillator and a frequency divider in a short time. The method is characterized by comprising the following steps: finding a control word controlling the frequency of the digital controlled oscillator by a designed algorithm; dividing the frequency of a clock output by the digital controlled oscillator which is controlled bythe control word to obtain a divided-frequency clock with the frequency approximate to a reference clock frequency; and then, controlling the digital controlled oscillator to lock based on a phase difference between the reference clock and the divided-frequency clock which are distinguished by the phase detection discriminator. The full digital phase-locked loop is provided with a rapid frequencycapture loop and a phase-locked loop which alternately work, i.e. firstly, the rapid frequency capture loop finishes frequency capture, and then, the phase-locked loop finishes accurate locking.

A robust scalable laser. The laser includes plural fiber laser resonators. A cavity that is external to the fiber laser resonators combines plural laser beams output from the plural fiber laser resonators into a single output laser beam. In a specific embodiment, the plural fiber laser resonators are eye-safe double-clad Er:YAG laser resonators that are pumped via laser diode arrays.

The invention discloses a stable photoelectric oscillator. The stable photoelectric oscillator comprises a laser device, an electro-optical modulator, a long optical fiber, a photoelectric detector, an amplifier, an electric band-pass filter, an electrically-controlled microwave phase shifter, a high-stability microwave source, a 2*1 wave combiner or directional coupler, a first 1*2 power divider or directional coupler, a second 1*2 power divider or directional coupler, a third 1*2 power divider or directional coupler and a phase locking control module, wherein the phase locking control module comprises a frequency mixer, an electric low pass filter and a servo control module, the output end of the frequency mixer is connected to the input end of the electric low pass filter, and the output end of the electric low pass filter is connected to the input end of the servo control module. According to the stable photoelectric oscillator, an electric injection of the external high-stability microwave source and a phase locking control mechanism are added based on a traditional single-loop OEO structure. Compared with the prior art, the stable photoelectric oscillator has the advantages that insertion loss of an optical link in a resonant cavity is not increased, the high signal to noise ratio of the photoelectric resonant cavity is maintained, and the structural complexity of the stable photoelectric oscillator is lower than that of an existing scheme. The stable photoelectric oscillator is easy to obtain.

The invention discloses a sine-wave modulation photo plethysmo graphy measuring device and method. A microprocessor is used for outputting sine waves which are at different frequencies and are in a twifold rate relation; the sine waves are used for driving at least four light-emitting diodes; light emitted by the light-emitting diodes is received by a light-sensitive device after passing through a tested finger; the light-sensitive device is used for converting the received light into a voltage signal; the voltage signal is converted into a preset amplitude voltage signal by using a current/voltage conversion amplifier; an analog to digital converter is used for converting the preset amplitude voltage signal into a digital signal; the microprocessor is used for processing the digital signal to obtain photo plethysmo graphy and a valley value and a peak value of the photo plethysmo graphy; and a spectrum value is obtained according to the valley value and the peak value. The method comprises the following steps of: performing phase locking computation and separation processing on the digital signal to obtain photo plethysmo graphy and eliminating the interference of background light by using the microprocessor; acquiring the valley value and the peak value according to the photo plethysmo graphy; and computing the valley value and the peak value to obtain an absorbency difference value and obtaining a spectrum value according to the absorbency difference value. A circuit is simple, and the digital signal is concise.

Feedback loops can be used to shift and stabilize the carrier-envelope phase of a frequency comb from a mode-locked fibers laser or other optical source. Compared to other frequency shifting and stabilization techniques, feedback-based techniques provide a wideband closed-loop servo bandwidth without optical filtering, beam pointing errors, or group velocity dispersion. It also enables phase locking to a stable reference, such as a Ti:Sapphire laser, continuous-wave microwave or optical source, or self-referencing interferometer, e.g., to within 200 mrad rms from DC to 5 MHz. In addition, stabilized frequency combs can be coherently combined with other stable signals, including other stabilized frequency combs, to synthesize optical pulse trains with pulse durations of as little as a single optical cycle. Such a coherent combination can be achieved via orthogonal control, using balanced optical cross-correlation for timing stabilization and balanced homodyne detection for phase stabilization.

The invention discloses an ultrasonic ranging method, belonging to the technical field of electronic measurements. The ultrasonic ranging method comprises the following steps that: an ultrasonic transmitter and a pulse laser are located at a transmitting end, the transmitting end receives a measuring command, subsequently, the pulse laser triggers a beam of pulse laser and the ultrasonic transmitter triggers an ultrasonic wave at the same time, and phase locking is carried out on the triggered ultrasonic wave and an external clock source; an ultrasonic receiver and a photodiode are located at a receiving end, after the photodiode receives the pulse laser, a timer is started, after the ultrasonic receiver acquires the received ultrasonic wave, the timer is stopped to acquire transition time; the transition time multiplies by a revised sound velocity to acquire a rough measurement value of a measured distance; and a phase difference is obtained, a fine measurement part is lambda delta omega/2phi, and an actually measured distance d' is acquired, wherein d'=Nlambda+lambda delta omega/2phi. The ultrasonic ranging method has the advantages that the receiver is easily interfered by the transmitter, a measurement blind zone is greatly reduced, the ultrasonic distance measuring directivity is improved, the distance measuring precision is improved within one ultrasonic wavelength; and the ultrasonic ranging method is particularly suitable for distance measurement in a single station type space orientation and measurement system.

Since a continuous movie effect is created at 24 frames/second, a TV or a movie screen capable of displaying 48 frames/second can alternate the frames from two different programs, so that the frames of each program will have the rate of 24 frames/second. Two viewers wearing eye-pieces with phase locking strobe, running at 24 frames/second, can each lock on different set of alternating frames, and block the other set. The strobe is synchronized with the display, so that each of the viewers gets to see only the 24 frames/sec that is relevant to the program that viewer is watching. One embodiment allows other viewer to view another program at 24 frames/second. Each viewer also has a separate audio feed associated with his or her viewing program.

The invention discloses a signal tracing algorithm of a GNSS receiver. The signal tracing algorithm is capable of overcoming the phase-locked loop lock loosing problem by means of a frequency locking/phase locking cascade tracking loop, after the phase-locked loop is unlocked, a frequency locking loop helps the phase-locked loop to restore quickly, and moreover, a loop filter reset scheme is designed to control the error between the output value of the loop filter and the Doppler observed value at the last time, so that the phase-locked loop is fastened to restore from the lock loos state. The signal tracing algorithm automatically switches between a vector tracking loop and a scalar tracking loop according to the signal environment so as to improve the usability and dynamic property of the receiver. Whether the signal to noise ratio is low or the signal is momently interrupted due to shield, the performance of the receiver is not lower than the ordinary GNSS receiver, the influence of the accumulative error caused by the signal failure or interference of a satellite on the other satellite signal processing channels is avoided, and the system stability and the location output reliability are improved.

The invention discloses a high-energy-efficiency low-jitter single loop clock data recovery circuit. The circuit comprises an 1/N rate Bang-Bang phase discriminator with a 1:N demultiplexer function, a voltage-current converter, a loop filter and a multi-phase clock generator. An orthogonal clock signal generated by an orthogonal voltage control oscillator in the multi-phase clock generator is synthesized into a needed (N+2) phase recovery clock signal through a cascaded digital phase interpolator. And then the 1/N rate Bang-Bang phase discriminator receives input data and a phase clock signal, detects a phase relationship between the two to generate a lead/lag voltage signal and recovers N paths of parallel 1/N rate data signals. Then, the lead/lag voltage signal is converted into a current signal through the voltage-current converter. A current passes through loop filter filtering and then controls an output clock frequency and a phase relationship of the multi-phase clock generator so as to reduce a frequency deviation so that phase locking of a clock data recovery loop is reached. Jitter performance of the clock data recovery loop is effectively improved.

The invention relates to a method for online monitoring the content of gas in transformer oil and a system thereof. A gas optoacoustic spectroscopy is adopted to measure the gas dissolved in the transformer oil, namely, after the gas is sent into an opto-acoustic pond, a gas circuit valve is closed, laser sent by a laser is used for radiating sample gas in the opto-acoustic pond, sound wave is generated by the gas which passes through light-absorbing pulse, and the intensity of the sound wave is detected by a rheomicrophone; then, a signal is amplified by preposing and phase locking, and the data of the signal is collected by a high-accuracy digital-analog converter and a DSP data transmitter and stored; at the same time, opto-acoustic phase drift analysis is carried out by a lock-in amplifier, and the running quality or fault category and fault severity of an electrical power unit is exactly judged according to the sorts and the concentration of the gas, thus judging the running state or the property and degree of fault of the electrical power unit with high accuracy. The invention has simple structure and stable running, and can realize online monitoring for a long time.

The invention provides a subsynchronous oscillation suppression device and method based on a phase-locked loop error. The subsynchronous oscillation suppression device comprises a three-phase inverter, a control module and a signal detection module, wherein a first input end of the signal detection module is used for receiving the three-phase AC voltage of a synchronizer port, a second input end is used for receiving the three-phase AC voltage of a device port, a third input end is used for receiving the three-phase AC current of the device port, a first input end of the control module is connected to a first output end of the signal detection module, a second input end of the control module is used for receiving a DC bus voltage, a third input end of the control module is connected to a third output end of the signal detection module, a fourth input end of the control module is connected to a fourth output end of the signal detection module, a fifth input end of the control module is connected with a second output end of the signal detection module, the control module is used for further adjusting electrical damping size through control of reactive current according to a phase-locked error signal obtained by the signal detection module, so that the subsynchronous oscillation of a system is suppressed.

The invention provides a digital PLL (Phase-Locked Loop) based phase noise measuring device. The digital PLL based phase noise measuring device comprises a frequency power measuring unit, a phase discrimination unit, a filtering unit, a DC (Direct Current) bias compensation unit, a low-noise amplification unit, an acquisition, frequency discrimination and phase discrimination unit, a digital loop filtering unit, a phase discrimination constant detection unit, a self-adaptive digital gain control unit, a reference source unit, and a signal processing and displaying unit. According to the digital PLL based phase noise measuring device, a double-balanced mixer is adopted as a phase discriminator, the phase noise of a measured source is extracted through a digital PLL, the specific noise extraction mode is divided into frequency mixer phase discrimination and digital delay line frequency discrimination, and DC caused by a loop circuit is counteracted through a DC bias compensation circuit, so that too big DC after amplification, induced ADC saturation and induced loop lock-losing are prevented. The implementation scheme of the digital PLL based phase noise measuring device is simple, totally excellent phase noise measuring sensitivity can be realized, the realized analysis frequency spectrum range is also very wide, and phase noise testing demands of most signal sources can be satisfied.

The embodiment of the invention discloses a resonance wave detecting and phase-locking method and a resonance wave detecting and phase-locking method for an active power filter. The method comprises the following steps of: carrying out phase shift filtering to a sampled three-phase voltage signal to obtain a first-grade processing signal; substituting the first-grade processing signal into an sequence-dividing formula to obtain a three-phase voltage fundamental positive sequence component; and adopting a dq synchronous coordinate system to lock phase of the three-phase voltage fundamental positive sequence component. The embodiment of the invention extracts the three-phase voltage fundamental positive sequence component in an unbalanced grid by using a way of dividing sequence first and locking phase consequently, locks phase of the positive sequence component by using a dq synchronous coordinate system phase-locking algorithm to obtain a positive sequence fundamental phase angle and eliminate the influence of grid imbalance on the phase locking link, so that the phase locking precision is wholly improved and the technical effect that the real-time and precise phase locking can also be carried out in the situation of unbalanced voltage in the grid is achieved.

The invention discloses a zero-crossing-point accurate detection method for AC voltage signals. The method includes the following steps: firstly selecting a comparatively large hardware filtering time constant to ensure that harmonic waves and random noises which may be included in the AC voltage signals can be filtered comparatively well; using large-time-constant software PQ filtering to extract and eliminate DC drift generated by software and hardware; setting a software judgment advancing quantity so as to offset zero-crossing-point delay caused by hardware filtering; accurately calculating random errors t caused by sampling intervals; and at last, using capture and comparison functions of an embedded microcontroller to realize accurate information of an AC voltage frequency and phase so that accurate phase locking of the AC signals can be realized. The detection method solves a problem of zero drift and phase delay caused by a hardware detection circuit and a software algorithm when zero-crossing-point detection is carried out on the AC voltage signals.