Quick low frequency pulse-width signal demodulating equipment and demodulation method
Technical field
The invention belongs to electronic technology field, relate to the pulse-width signal demodulation.More particularly, the present invention relates to a kind of quick low frequency pulse-width signal demodulation method of new high-performance low price.
Background technology
In illuminator, especially in the LED illuminator, requirement of light regulation has become a basic demand.Its dim signal normally transmits in the pulse-width signal mode, for example, and the controllable silicon dimmer of incandescent lamp commonly used.Controllable silicon dimmer transmits 50 hertz of low frequencies or 60 hertz of alternating signals of deciding frequency, and its pulsewidth is that the angle of flow with controllable silicon dimmer changes, that is to say, its pulsewidth reflection controllable silicon dimmer given controlling value.How extracting this pulse width information of deciding the low frequency pulse-width signal of frequency has some ready-made methods, but has the problem on using.As shown in Figure 1, for a low frequency pulse-width signal, its frequency spectrum is made up of with its fundamental frequency and high order harmonic component the DC component of its corresponding pulsewidth.Specifically for the output of controllable silicon dimmer, its fundamental frequency is 50,60 hertz or 100,120 hertz.On frequency domain, 50,60 hertz or 100,120 hertz of very close DC component of fundamental frequencies (zero hertz).Extract the DC component in this low frequency pulse-width signal, these needs very low pass filter of arrowband come its fundamental frequency of filtering, i.e. 50,60 hertz or 100,120 hertz and all high order harmonic components.By the characteristic of low pass filter as can be known, the dynamic responding speed of its low pass filter is to be directly proportional with its bandwidth, that is, the bandwidth of low pass filter is narrow more, and its dynamic responding speed is slow more.
In actual applications, normally wish controlling value when controllable silicon dimmer after artificial change, its corresponding illuminator should be able to promptly change the effect of its corresponding brightness with the corresponding controlling value of feeding back controllable silicon dimmer.If the pulse width information of 50,60 hertz of low frequencies or 100,120 hertz of pulse-width signals is to be extracted by the unusual low pass filter of arrowband, pulse width information needs considerable time to extract, and can not promptly change the effect of its corresponding brightness with the corresponding controlling value of feeding back this controllable silicon dimmer so its corresponding illuminator has the hysteresis of long duration.Obviously the pulse width information that adopts narrowband low-pass filter to extract 50,60 hertz of low frequencies or 100,120 hertz of pulse-width signals can not satisfy requirement of actual application.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of quick low frequency pulse-width signal demodulation method of new high-performance low price, and it can extract the pulse width information of 50,60 hertz of low frequencies or 100,120 hertz of pulse-width signals apace.
In order to solve the problems of the technologies described above, the invention provides a kind of quick low frequency pulse-width signal demodulating equipment: comprise phase-locked loop circuit and synchronous extraction circuit; Phase-locked loop circuit comprises phase discriminator, loop filter, voltage controlled oscillator and the frequency divider that links to each other successively and form closed loop; Synchronous extraction circuit comprises unit period integrator and the sampling holder that links to each other successively; Frequency divider links to each other with sampling holder with the unit period integrator respectively, and frequency divider links to each other with the unit period integrator with line between the phase discriminator.
Improvement as quick low frequency pulse-width signal demodulating equipment of the present invention: the unit period integrator is combined by the output signal of the frequency divider in switched-capacitor integrator and the phase-locked loop circuit; The integral constant of switched-capacitor integrator is proportional to corresponding unit period.
The present invention also provides the quick low frequency pulse-width signal demodulation method that utilizes said apparatus to carry out simultaneously: phase-locked loop circuit is used to produce and decides frequency low frequency pulse-width signal with the square-wave signal of frequency homophase and the square-wave signal of corresponding multiple frequency;
Decide frequency low frequency pulse-width signal through the unit period integrator in the unit period integrates; The output signal of unit period integrator is sampled the retainer sampling in all end of term of unit period integration and keeps output, and the pulsewidth of deciding frequency low frequency pulse-width signal promptly is the sampling maintenance output of sampling holder with the d. c. voltage signal form.
But entire circuit separated into two parts of the present invention: first phase-locked loop circuit, it is by phase discriminator, loop filter, voltage controlled oscillator and frequency divider are formed; It two is synchronous extraction circuits, and it is made up of unit period integrator and sampling holder.Phase-locked loop circuit is to be used to produce and the square-wave signal of deciding the same frequency of frequency low frequency pulse-width signal homophase and the square-wave signal of corresponding multiple frequency.The square-wave signal with the square-wave signal of deciding the same homophase frequently of frequency low frequency pulse-width signal and corresponding multiple frequency that phase-locked loop circuit produced can combine with integrator and form the unit period integrator.The unit period integrator is to make the integral constant of this integrator be proportional to the cycle of unit period integration, that is, and and the fixed cycle of pulse-width signal frequently.
Decide frequency low frequency pulse-width signal through this unit period integrator in the unit period integrates.Its output signal is sampled the retainer sampling in all end of term of unit period integration and keeps output, and this pulsewidth of deciding frequency low frequency pulse-width signal promptly is the sampling maintenance output of sampling holder with the d. c. voltage signal form.
Advantage of the present invention is not need low pass filter (though loop filter is arranged in the phase-locked loop circuit, but when the square-wave signal frequency of deciding the same frequency homophase that frequency low frequency pulse-width signal frequency and phase-locked loop circuit produced was identical, the output of this loop filter changed quite little) just can extract the pulse width information of deciding frequency low frequency pulse-width signal.
Advantage of the present invention be it that pwm value of deciding frequency low frequency pulse-width signal that is extracted can be changed after the cycle of a unit period integration, that is the pwm value information of, being extracted of deciding frequency low frequency pulse-width signal only lags behind a pulse width signal cycle.
Advantage of the present invention is the dynamic responding speed of its demodulation method is extracted the pulse width information of 50,60 hertz of described low frequencies or 100,120 hertz of pulse-width signals much larger than the employing narrowband low-pass filter a dynamic responding speed.
Description of drawings
Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in further detail.
Fig. 1 is the pulse width information scheme that existing narrowband low-pass filter is extracted 50,60 hertz of this low frequencies or 100,120 hertz of pulse-width signals.
Fig. 2 is the block diagram of quick low frequency pulse-width signal demodulating equipment of the present invention.
Fig. 3 is the instantiation circuit diagram of quick low frequency pulse-width signal demodulating equipment of the present invention.
Embodiment
The quick low frequency pulse-width signal demodulation method instantiation circuit of high-performance low price of the present invention as shown in Figure 3.But entire circuit separated into two parts.First phase-locked loop circuit 100, it is made up of the phase discriminator 1, loop filter 2, voltage controlled oscillator 3 and the frequency divider 4 that link to each other successively and form closed loop.It two is synchronous extraction circuits 200, and it is made up of interconnective unit period integrator 5 and sampling holder 6.Frequency divider 4 links to each other with sampling holder 6 with unit period integrator 5 respectively.Unit period integrator 5 is combined by the output signal of the frequency divider 4 in switched-capacitor integrator and the phase-locked loop circuit 100; The integral constant of switched-capacitor integrator is proportional to corresponding unit period.
The operation principle of phase-locked loop circuit 100 can be with reference to " Phase Lock Technique " (publishing house of Xian Electronics Science and Technology University, the 14th printing of 2006 publication times.ISBN 7-5606-0292-4/TN*0075 (class)).
Phase-locked loop circuit 100 is to be used to produce and the square-wave signal of deciding the same frequency of frequency low frequency pulse-width signal homophase and the square-wave signal of corresponding multiple frequency, as the switch periods signal of switched-capacitor integrator.The switch periods signal of switched-capacitor integrator is the frequency divider of taking from the phase-locked loop circuit 100 4.Can make the integral constant of switched-capacitor integrator be proportional to the cycle of this unit period integration, that is, and the fixed cycle of pulse-width signal frequently.Decide frequency low frequency pulse-width signal through switched-capacitor integrator in the unit period integrates.The output signal of switched-capacitor integrator is sampled retainer 6 samplings in all end of term of unit period integration and keeps output, and this pulsewidth of deciding frequency low frequency pulse-width signal promptly is the sampling maintenance output of sampling holder 6 with the d. c. voltage signal form.And this switched-capacitor integrator is reset to next unit period integration in all end of term of unit period integration and prepares.
Certainly sampling holder 6 sampling maintenances and switched-capacitor integrator reset and all need the time to finish.Time is much smaller than the cycle of unit period integration as required, and the error that sampling holder 6 samplings keep and switched-capacitor integrator resets to be caused can be in the scope of acceptance.Otherwise some complicated circuits will be introduced to solve the error that the sampling holder sampling keeps and switched-capacitor integrator resets and caused.
In the quick low frequency pulse-width signal demodulation method of high-performance low price of the present invention, owing to do not have low pass filter (though loop filter 2 is arranged in the phase-locked loop circuit 100, but when the square-wave signal frequency that decide the same frequency homophase that frequency low frequency pulse-width signal frequency and phase-locked loop circuit 100 produced identical, the output of loop filter 2 changes quite little), this pwm value of deciding frequency low frequency pulse-width signal that makes the quick low frequency pulse-width signal demodulation method of high-performance low price of the present invention be extracted can change after the cycle of a unit period integration, that is the pwm value of deciding frequency low frequency pulse-width signal that, is extracted only lags behind a pulse width signal cycle.So in the dynamic responding speed of the quick low frequency pulse-width signal demodulation method of high-performance low price of the present invention much larger than adopting narrowband low-pass filter to extract the dynamic responding speed of the pulse width information of 50,60 hertz of this low frequencies or 100,120 hertz of pulse-width signals.
At last, it is also to be noted that what more than enumerate only is a specific embodiment of the present invention.Obviously, the invention is not restricted to above embodiment, many distortion can also be arranged.All distortion that those of ordinary skill in the art can directly derive or associate from content disclosed by the invention all should be thought protection scope of the present invention.