CN109302177A - A kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies - Google Patents
A kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies Download PDFInfo
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- CN109302177A CN109302177A CN201811424787.9A CN201811424787A CN109302177A CN 109302177 A CN109302177 A CN 109302177A CN 201811424787 A CN201811424787 A CN 201811424787A CN 109302177 A CN109302177 A CN 109302177A
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- 230000010363 phase shift Effects 0.000 claims abstract description 19
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/081—Details of the phase-locked loop provided with an additional controlled phase shifter
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
- H03L7/093—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using special filtering or amplification characteristics in the loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
- H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
- H03L7/183—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number
- H03L7/193—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number the frequency divider/counter comprising a commutable pre-divider, e.g. a two modulus divider
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Abstract
The invention discloses a kind of digital control square wave phase shifters based on two frequency multiplication two divided-frequencies, the square wave that input duty cycle is 50% is rectified by differential by square-wave signal frequency multiplication, by determining pulse stretcher circuit for differentiated pulse width broadening to certain width, it is integrated to obtain sawtooth wave to width pulse wave is determined, sawtooth wave is input to comparator, the output voltage size adjustment comparative level that CPU controls DAC realizes phase shift, then the output two divided-frequency of comparator is obtained the phase shift square wave that duty ratio is 50%.The principle of the invention is easily understood, and circuit structure is easily achieved, and practical value is high.
Description
Technical field
The present invention relates to a kind of digital feedback precision square waves based on two frequency multiplication two divided-frequencies for Lightning Warning field
Phase shifter.
Background technique
Lightening activity can cause the significant changes of ground electric field, very big to the effect of human activity, especially building, defeated
For wire mesh etc., is hit once meeting with, may cause heavy losses.According to the incomplete statistics of department of State Grid, in
State's ultra-high-tension power transmission line is because account for the total tripping times of electric system by electric system tripping times caused by lightening strikes
40%-70%, in the higher place of the regional thunder and lightning probability of happening such as western part of China, overhead transmission line caused by lightening strikes is jumped
Lock rate can be higher.According to China national electric system electric power netting safe running recent years situation, in 110kv-500kv electric power facility
In failure, power department trip event proportion caused by lightening strikes has reached the first of the conveying total tripping times of electric system
Name, the abnormal stoppage in transit number of the caused conveying electric system of lightening strikes are number two.Lightening strikes transmission line of electricity can not only cause
The trip accident on transportion wire road has huge shadow to the safety of Operation of Electric Systems, economy, reliability and stability
It rings.Therefore, the development of lightning monitoring early warning system is of great significance to China's power network safety operation.
Lightning Warning technology is the technical problem studied extensively both at home and abroad at present, is primarily present two difficult points: first is that ground
Face electric field instrument sensor current signal is faint, second is that the input impedance of sensor is especially high, and electromagnetic interference is serious, generally to use phase
Quick detection technique measures faint signal.The square-wave signal that duty ratio is 50% is needed to carry out during phase-sensitive detection same
Step, synchronization signal block the acquisition of transmission-type optocoupler, after optocoupler fixes, the phase of square wave often through the movable plate of sensor
Position just secures, and the detection signal of sensor output is AC signal, generates phase shift during amplification, filtering, optocoupler
The synchronization square wave and sensor output signal of output are unable to precise synchronization, bring biggish error to phase sensitive detector, it is necessary to right
The square-wave signal of optocoupler output carries out accurate phase shift, the accuracy of synchronization signal is improved, to improve the detection accuracy of system.
Summary of the invention
It is anti-the purpose of the invention is to overcome the deficiencies of the prior art and provide a kind of number based on two frequency multiplication two divided-frequencies
Feedback formula precision square wave phase shifter, can obtain the accurate synchronization signal of phase sensitive detector.
Realizing a kind of technical solution of above-mentioned purpose is: a kind of digital feedback precision square wave based on two frequency multiplication two divided-frequencies
Phase shifter, including differential circuit, full-wave rectifying circuit, waveform shaping circuit, determine pulse stretcher circuit, integrating circuit, reverse phase and put
Big device circuit, cpu circuit, D/A converting circuit, comparator circuit and frequency-halving circuit；
Differential circuit described in square wave input；The differential circuit, the full-wave rectifying circuit, the waveform shaping circuit,
It is described to determine pulse stretcher circuit, the integrating circuit and inverting amplifier circuit and be sequentially connected；The cpu circuit and the digital-to-analogue
Conversion circuit is sequentially connected；The output end of the output end of the inverting amplifier circuit and the D/A converting circuit is respectively connected to
The comparator circuit, the comparator circuit export phase shift to the frequency-halving circuit output signal, the frequency-halving circuit
Square wave.
Further, the differential circuit is made of capacitor C1 and resistance R1, carries out differential to the square wave of input；It is described complete
Wave rectification circuit is made of diode D1, diode D2, diode D3 and diode D4, and differentiated waveform inputs the full-wave rectification
Circuit realizes two frequency multiplication of signal；It is described to determine pulse stretcher circuit for 74HC14, after two frequency-doubled signals carry out waveform shaping and reverse phase
It is output to the integrating circuit；The integrating circuit is NE555 monostable circuit, carries out pulse stretcher to signal；Broaden waveform
It is input to comparator circuit A3 by integrating circuit and inverting amplifier circuit, comparator circuit A3 exports inverting amplifier A2
Output with d convertor circuit is compared, with output pulse signal；The frequency-halving circuit is d type flip flop circuit, arteries and veins
It rushes signal input d type flip flop circuit and carries out two divided-frequency.
Further, the value of the numeral input Di of the d convertor circuit DAC is adjusted just to realize square wave phase shift
Function, phase shift angle are
Wherein n is the bit length of Digital To Analog Convert DAC, and UREF is the voltage reference of DAC, square-wave cycle T, pulse broadening width
Degree is t, and the amplitude peak of sawtooth wave is V.
Further, switch K in parallel on the capacitor of the integrating circuit is simulated photoelectric switch, the comparator electricity
Road A3 uses LM219, the amplifier A1 of the amplifier circuit to use OP27 using AD823, amplifier A2.
The beneficial effects of the present invention are: digital feedback square wave phase shifter of the present invention can make the side of duty ratio position 50%
Wave carries out accurate phase shift, achievees the purpose that raising system synchronization accuracy.The principle of the invention is easily understood, and circuit structure is easy to real
Existing, practical value is high.
Detailed description of the invention
Fig. 1 is a kind of principle of work and power of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies of the invention
Figure；
Fig. 2 is a kind of wave of the signal in digital control square wave phase shifter each stage based on two frequency multiplication two divided-frequencies of the invention
Shape figure；
Fig. 3 is a kind of structural representation of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies of the invention
Figure.
Specific embodiment
In order to preferably understand technical solution of the present invention, below by specifically embodiment and in conjunction with attached drawing
It is described in detail:
Referring to Fig. 1, a kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies, including differential electricity
Road, full-wave rectifying circuit, waveform shaping circuit, determine pulse stretcher circuit, integrating circuit, inverting amplifier circuit, cpu circuit,
D/A converting circuit, comparator circuit and frequency-halving circuit.
Differential circuit described in square wave input；The differential circuit, the full-wave rectifying circuit, the waveform shaping circuit,
It is described to determine pulse stretcher circuit, the integrating circuit and inverting amplifier circuit and be sequentially connected；The cpu circuit and the digital-to-analogue
Conversion circuit is sequentially connected；The output end of the output end of the inverting amplifier circuit and the D/A converting circuit is respectively connected to
The comparator circuit, the comparator circuit export phase shift to the frequency-halving circuit output signal, the frequency-halving circuit
Square wave.
Referring to Fig. 2, it is square-wave signal A that T duty ratio is 50% in the period that input square wave, which is, square-wave signal A output is sent to
Differential circuit obtains positive and negative narrow pulse signal B by differential circuit.Positive and negative narrow pulse signal B is input to full-wave rectification electricity
Rood is to two times of frequency input signal of narrow pulse signal C.By two times of frequency input signal of narrow pulse signal C by shaping and
Reverse phase obtains waveform E.Waveform E is input to stretch circuit, the width of pulse broadening is its waveform F of t (0 < t < T/2).
The waveform F of broadening is input to integrator circuit, obtains sawtooth wave H.If the height of sawtooth wave H is V, CPU controls DAC output electricity
Pressure is VDAC, and as shown in G in Fig. 2, sawtooth signal and DAC output voltage VDAC are sent to the input terminal of comparator simultaneously, is compared
Device exports square wave as shown in J in Fig. 2, and J waveform in figure is carried out two divided-frequency, so that it may which obtaining duty ratio is 50% phase shift square wave K.
Assuming that DAC selects n Digital To Analog Converts, the voltage reference of DAC is UREF, square-wave cycle T, and pulse broadening width is
T, the amplitude peak of sawtooth wave are V, and square-wave pulse phase shift angle is Δ θ, and the phase shift time is Δ t, according to fig. 2, then:
360:T=Δ θ: Δ t (2)
Square wave phase shift angle can be obtained by formula (1) (2) (3) are as follows:
It can make Δ θ linear change, realization pair according to the value of the numeral input Di of the adjustable digital analog converter DAC of formula (4)
The accurate phase shift of square wave.
Referring to Fig. 3, a kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies.The rotation of sensor movable plate
Raw synchronization signal of changing the line of production is input in phase shifter.The differential circuit is made of capacitor C1 and resistance R1, to the square wave of input
Differential is carried out, waveform B is obtained.The full-wave rectifying circuit is made of diode D1, D2, D3 and D4, described in differentiated waveform input
Full-wave rectifying circuit realizes two frequency multiplication of signal, obtains waveform C.It is described determine pulse stretcher circuit be 74HC14, two frequency-doubled signals into
After row waveform shaping and reverse phase, waveform E is obtained, is output to the integrating circuit.The integrating circuit is NE555, resistance R2, electricity
Hold the monostable flipflop that C2 and capacitor C3 is constituted, waveform E is sent into monostable flipflop, the failing edge triggering of waveform E is monostable
State circuit, generates high level output, and high level lasting time t is determined that i.e. t=1.1RC is obtained by the value of resistance R2 and capacitor C2
To waveform F.Amplifier A1, resistance R3, capacitor C4, phase inverter and switch K constitute integrating circuit, and switch K is simulated photoelectric switch,
When high level inputs, phase inverter exports low level, and switch K is disconnected, integrating circuit reverse phase integral, when low level input, reverse phase
Device output is high level, and switch K conducting, the output of integrator returns to zero, so that one reverse phase sawtooth wave of generation, passes through amplifier
Circuit (A2, R4, R5) reverse phase is obtained such as the waveform H in Fig. 2.Waveform H is sent into comparison circuit A3, DAC output is controlled by CPU
Voltage changes the comparative level of comparison circuit A3, adjusts phase shift size, waveform J in comparison circuit A3 output waveform such as figure, then pass through
It crosses d type flip flop two divided-frequency and obtains phase shift square wave, the waveform K in waveform such as Fig. 2.
The comparator circuit A3 uses LM219, the amplifier A1 of the amplifier circuit to use AD823, amplifier A2
Using OP27.
Those of ordinary skill in the art it should be appreciated that more than embodiment be intended merely to illustrate the present invention,
And be not used as limitation of the invention, as long as the change in spirit of the invention, to embodiment described above
Change, modification will all be fallen within the scope of claims of the present invention.
Claims (4)
1. a kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies, including differential circuit, full-wave rectification electricity
Road, waveform shaping circuit, determine pulse stretcher circuit, integrating circuit, inverting amplifier circuit, cpu circuit, D/A converting circuit,
Comparator circuit and frequency-halving circuit；It is characterized by:
Differential circuit described in square wave input；It is the differential circuit, the full-wave rectifying circuit, the waveform shaping circuit, described
Determine pulse stretcher circuit, the integrating circuit and inverting amplifier circuit to be sequentially connected；The cpu circuit and the digital-to-analogue conversion
Circuit is sequentially connected；The output end of the output end of the inverting amplifier circuit and the D/A converting circuit is respectively connected to described
Comparator circuit, the comparator circuit export phase shift square wave to the frequency-halving circuit output signal, the frequency-halving circuit.
2. a kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies according to claim 1, special
Sign is that the differential circuit is made of capacitor C1 and resistance R1, carries out differential to the square wave of input；The full-wave rectifying circuit
It is made of diode D1, diode D2, diode D3 and diode D4, differentiated waveform inputs the full-wave rectifying circuit and realizes letter
Number two frequencys multiplication；It is described to determine pulse stretcher circuit for 74HC14, it is output to after the progress waveform shaping of two frequency-doubled signals and reverse phase described
Integrating circuit；The integrating circuit is NE555 monostable circuit, carries out pulse stretcher to signal；It broadens waveform and passes through integral electricity
Road and inverting amplifier circuit are input to comparator circuit A3, and comparator circuit A3 is exported to inverting amplifier A2 and digital-to-analogue conversion
The output of device circuit is compared, with output pulse signal；The frequency-halving circuit is d type flip flop circuit, and pulse signal inputs D
Flip-flop circuit carries out two divided-frequency.
3. a kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies according to claim 2, special
Sign is, adjusts the value of the numeral input Di of the d convertor circuit DAC just to realize square wave phase shift function, phase shift angle
For
Wherein bit length of the n for Digital To Analog Convert DAC, voltage reference of the UREF for DAC, square-wave cycle T, pulse broadening width are
T, the amplitude peak of sawtooth wave are V.
4. a kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies according to claim 2, special
Sign is that switch K in parallel is simulated photoelectric switch on the capacitor of the integrating circuit, and the comparator circuit A3 is used
The amplifier A1 of LM219, the amplifier circuit use OP27 using AD823, amplifier A2.
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| CN201811424787.9A CN109302177A (en) | 2018-11-27 | 2018-11-27 | A kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies |
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| CN201811424787.9A CN109302177A (en) | 2018-11-27 | 2018-11-27 | A kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113300205A (en) * | 2021-05-20 | 2021-08-24 | 上海瀚宇光纤通信技术有限公司 | Fiber laser protection system and device |
| CN113595530A (en) * | 2021-07-26 | 2021-11-02 | 国电南瑞科技股份有限公司 | Operation monitoring control circuit suitable for electric power secondary equipment |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0697789A (en) * | 1993-04-02 | 1994-04-08 | Casio Comput Co Ltd | Phase shift circuit |
| CN2185959Y (en) * | 1993-08-04 | 1994-12-21 | 罗锰镍 | Quasi-synchronous pulse generator |
| CN2239101Y (en) * | 1995-06-21 | 1996-10-30 | 中国科学院物理研究所 | Wide band 0-360 degree phase shifter |
| US6417707B1 (en) * | 1997-07-07 | 2002-07-09 | Toric Limited | Noise reduction circuits |
| CN202586873U (en) * | 2012-05-18 | 2012-12-05 | 深圳Tcl新技术有限公司 | Frequency multiplier circuit and Bluetooth three dimensional glasses phase tester |
| CN104917489A (en) * | 2015-06-26 | 2015-09-16 | 武汉工程大学 | High-precision digital phase shifter |
| CN208939922U (en) * | 2018-11-27 | 2019-06-04 | 国网上海市电力公司 | A kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies |
-
2018
- 2018-11-27 CN CN201811424787.9A patent/CN109302177A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0697789A (en) * | 1993-04-02 | 1994-04-08 | Casio Comput Co Ltd | Phase shift circuit |
| CN2185959Y (en) * | 1993-08-04 | 1994-12-21 | 罗锰镍 | Quasi-synchronous pulse generator |
| CN2239101Y (en) * | 1995-06-21 | 1996-10-30 | 中国科学院物理研究所 | Wide band 0-360 degree phase shifter |
| US6417707B1 (en) * | 1997-07-07 | 2002-07-09 | Toric Limited | Noise reduction circuits |
| CN202586873U (en) * | 2012-05-18 | 2012-12-05 | 深圳Tcl新技术有限公司 | Frequency multiplier circuit and Bluetooth three dimensional glasses phase tester |
| CN104917489A (en) * | 2015-06-26 | 2015-09-16 | 武汉工程大学 | High-precision digital phase shifter |
| CN208939922U (en) * | 2018-11-27 | 2019-06-04 | 国网上海市电力公司 | A kind of digital feedback precision square wave phase shifter based on two frequency multiplication two divided-frequencies |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113300205A (en) * | 2021-05-20 | 2021-08-24 | 上海瀚宇光纤通信技术有限公司 | Fiber laser protection system and device |
| CN113595530A (en) * | 2021-07-26 | 2021-11-02 | 国电南瑞科技股份有限公司 | Operation monitoring control circuit suitable for electric power secondary equipment |
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