Low-frequency pulse width modulation signal demodulating equipment and demodulation method fast
Technical field
The invention belongs to electronic technology field, relate to pulse-width signal demodulation.More particularly, the present invention relates to a kind of quick low-frequency pulse width modulation signal demodulation method of new high-performance low price.
Background technology
In illuminator, especially, in LED illuminator, requirement of light regulation has become a basic demand.Its dim signal normally transmits in pulse-width signal mode, for example, and the controllable silicon dimmer of conventional incandescent lamp.Controllable silicon dimmer transmits 50 hertz of low frequencies or 60 hertz determines the alternating signal of frequency, and its pulsewidth is to change with the angle of flow of controllable silicon dimmer, that is to say the given controlling value of its pulsewidth reflection controllable silicon dimmer.How extracting this pulse width information of determining the low-frequency pulse width modulation signal of frequency has some ready-made methods, but has the problem in application.As shown in Figure 1, for a low-frequency pulse width modulation signal, its frequency spectrum is made up of with its fundamental frequency and high order harmonic component the DC component of its corresponding pulsewidth.The specifically output for 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 (zero hertz) of fundamental frequencies.Extract the DC component in this low-frequency pulse width modulation signal, this needs the very low pass filter of arrowband to carry out its fundamental frequency of filtering, i.e. 50,60 hertz or 100,120 hertz and all high order harmonic components.From the characteristic of low pass filter, the dynamic responding speed of its low pass filter is to be directly proportional to its bandwidth, that is, the bandwidth of low pass filter is narrower, and its dynamic responding speed is slower.
In actual applications, normally hope is when the controlling value of controllable silicon dimmer is after artificial change, and its corresponding illuminator should be able to promptly change the effect of its corresponding brightness with the corresponding controlling value of feedback 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 its corresponding brightness to feed back the effect of corresponding controlling value of 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 meet the requirement of practical application.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of quick low-frequency pulse width modulation 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 rapidly.
In order to solve the problems of the technologies described above, the invention provides a kind of low-frequency pulse width modulation signal demodulating equipment fast: comprise phase-locked loop circuit and synchronous extraction circuit; Phase-locked loop circuit comprises the phase discriminator, loop filter, voltage controlled oscillator and the frequency divider that are connected successively and form closed loop; Synchronous extraction circuit comprises successively connected unit period integrator and sampling holder; Frequency divider is connected with sampling holder with unit period integrator respectively, and the line between frequency divider and phase discriminator is connected with unit period integrator.
Improvement as quick low-frequency pulse width modulation signal demodulating equipment of the present invention: unit period integrator is combined by the output signal of the frequency divider in switched-capacitor integrator and 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 modulation signal demodulation method that utilizes said apparatus to carry out simultaneously: phase-locked loop circuit for generation of with determine frequency low-frequency pulse width modulation signal with the frequently square-wave signal of homophase and the square-wave signal of corresponding multiple frequency;
Determine frequency low-frequency pulse width modulation signal through unit period integrator integration in unit period; The output signal of unit period integrator is sampled retainer sampling in all end of term of unit period integration and keeps output, and the i.e. sampling taking d. c. voltage signal form as sampling holder of pulsewidth of determining frequency low-frequency pulse width modulation signal keeps output.
Whole circuit of the present invention can be divided into two parts: first phase-locked loop circuit, and it is by phase discriminator, loop filter, voltage controlled oscillator and frequency divider composition; It two is synchronous extraction circuits, and it is made up of unit period integrator and sampling holder.Phase-locked loop circuit be for generation of with determine frequency low-frequency pulse width modulation signal with the frequently square-wave signal of homophase and the square-wave signal of corresponding multiple frequency.Phase-locked loop circuit produce with determine frequency low-frequency pulse width modulation signal and can be combined with integrator and form unit period integrator with the frequently square-wave signal of homophase and the square-wave signal of corresponding multiple frequency.Unit period integrator is to make the integral constant of this integrator be proportional to the cycle of unit period integration,, determines the cycle of pulse-width signal frequently that is.
Determine frequency low-frequency pulse width modulation signal through this unit period integrator integration in unit period.Its output signal is sampled retainer sampling in all end of term of unit period integration and keeps output, and this i.e. sampling taking d. c. voltage signal form as sampling holder of pulsewidth of determining frequency low-frequency pulse width modulation signal keeps output.
Advantage of the present invention is not need low pass filter (although there is loop filter in phase-locked loop circuit, but when determining the square-wave signal frequency of the same frequency homophase that frequency low-frequency pulse width modulation signal frequency produces with phase-locked loop circuit when identical, the exporting change of this loop filter is quite little) just can extract the pulse width information of determining frequency low-frequency pulse width modulation signal.
Advantage of the present invention be it that can make the extracted pwm value of determining frequency low-frequency pulse width modulation signal after the cycle of a unit period integration, change, the pwm value information of determining frequency low-frequency pulse width modulation signal of, extracting 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 dynamic responding speed much larger than employing narrowband low-pass filter.
Brief description of the 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 modulation signal demodulating equipment of the present invention.
Fig. 3 is the instantiation circuit diagram of quick low-frequency pulse width modulation signal demodulating equipment of the present invention.
Embodiment
The quick low-frequency pulse width modulation signal demodulation method instantiation circuit of high-performance low price of the present invention as shown in Figure 3.Whole circuit can be divided 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 are connected 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 is connected 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 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 be for generation of with determine frequency low-frequency pulse width modulation signal with the frequently square-wave signal of 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 4 of taking from phase-locked loop circuit 100.Can make the integral constant of switched-capacitor integrator be proportional to the cycle of this unit period integration, that is, determine the cycle of pulse-width signal frequently.Determine frequency low-frequency pulse width modulation signal through switched-capacitor integrator integration in unit period.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 i.e. sampling taking d. c. voltage signal form as sampling holder 6 of pulsewidth of determining frequency low-frequency pulse width modulation signal keeps output.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 complete.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, the error being caused that some complicated circuits keep introducing with the sampling of solution sampling holder and switched-capacitor integrator resets.
In the quick low-frequency pulse width modulation signal demodulation method of high-performance low price of the present invention, owing to there is no low pass filter (although there is loop filter 2 in phase-locked loop circuit 100, but identical when determining the square-wave signal frequency of the same frequency homophase that frequency low-frequency pulse width modulation signal frequency produces with phase-locked loop circuit 100, the exporting change of loop filter 2 is quite little), this can change the pwm value of determining frequency low-frequency pulse width modulation signal that the quick low-frequency pulse width modulation signal demodulation method of high-performance low price of the present invention extracts after the cycle of a unit period integration, , the pwm value of determining frequency low-frequency pulse width modulation signal extracting only lags behind a pulse width signal cycle.Therefore in the dynamic responding speed of the quick low-frequency pulse width modulation 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.
Finally, it is also to be noted that, what more than enumerate is only a specific embodiment of the present invention.Obviously, the invention is not restricted to above embodiment, can also have many distortion.All distortion that those of ordinary skill in the art can directly derive or associate from content disclosed by the invention, all should think protection scope of the present invention.