CN112601330B - Linear adjustment method and system for light source brightness - Google Patents
Linear adjustment method and system for light source brightness Download PDFInfo
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Abstract
The invention provides a linear adjusting method and a system for light source brightness, wherein the method comprises the following steps: determining a target slope curve c0, wherein the target slope curve c0 corresponds to the PWM control frequency; according to the target slope curve c0 and the actually measured brightness curves under different duty ratiosSlope k of the line 1 Adjusting the PWM frequency; and creating a PWM mixing frequency equation between the PWM mixing frequency and the PWM comparison frequency as well as the PWM frequency regulating quantity, and calculating the PWM mixing frequency to obtain a PWM output signal so as to regulate the linearity of the brightness of the light source. The invention provides a linear regulation method of light source brightness, which regulates the linearity of the light source brightness by regulating the PWM frequency, and has the advantages of low cost, high response speed and good anti-interference performance.
Description
Technical Field
The invention relates to the technical field of mechanical vision light source adjustment, in particular to a linear adjustment method and system for light source brightness.
Background
The mechanical vision system mainly comprises three parts: illumination, lenses and cameras, wherein illumination is an important factor affecting machine vision system input, directly affecting the quality and application effect of input data.
In the industrial field of mechanical visual lighting adjustment, a linear adjustable range with higher requirements on the brightness of a visual light source is generally required. At present, medium and low power light sources can well meet the requirement of field application on the linear adjustable range of light source brightness, and high power light sources, especially light sources with the brightness adjusting linearity and the illumination uniformity of over one kilowatt, are subjected to power supply power, the electrical characteristics of electronic components and light source lamp beads V f The characteristics and the temperature of the light source have great influence, so the performance parameters of the light source in the aspect of linear adjustability of the brightness of the light source are inferior to those of light sources with medium and small power, and the design difficulty of the light source in the aspect of linearity is relatively great. After the high-power light source is adjusted to a certain brightness value, the brightness change of the high-power light source is no longer linear, and even sudden brightness change may occur.
In the prior art, there are various solutions to the problem of light source linearity in the high-power mechanical vision system, such as a constant current power supply control method, a switching power supply + digital constant current control method, a digital PWM control + brightness feedback compensation method, etc., where the adjustment of light source linearity controlled by a constant current power supply is a simpler and direct method, but the cost of a high-quality constant current power supply with linearly adjustable light source brightness in a certain range is higher than that of a common switching power supply, and the cost is related to the power of the power supply, and the stability is also reduced with the increase of the power supply power, thereby causing the fluctuation of the light source brightness; the switching power supply and digital constant current control method is adopted more, on one hand, the switching power supply is low in price compared with a constant current power supply, and the stability is better under the condition of high-power output, on the other hand, the digital constant current control module mainly controls the constant current of the light source, can overcome the adverse effect caused by the rise of the temperature of the light source, and is convenient for the linear adjustment of the brightness of the light source, but the method is influenced by the precision of electronic components, so that the range of the linear adjustment is limited; the digital PWM + brightness feedback compensation method has the advantages that the number of electronic components used is relatively small compared with the digital constant current control method, errors caused by the accuracy problem of the electronic components are relatively reduced, the cost is further reduced, the digital PWM mode can achieve the purpose of linear adjustment of the brightness of the light source from a zero point to the maximum output range under the condition of feedback compensation, the brightness feedback module is adopted for compensating the brightness, the linearity of brightness adjustment can be compensated, the influence of temperature change on the adjustment can be compensated, however, the installation position and compensation parameters of the brightness feedback module in the method are influenced by the illumination uniformity of the light source, and the design difficulty of the light source is directly increased. And the digital PWM brightness control mode mainly realizes brightness adjustment by adjusting the duty ratio under a fixed PWM frequency, namely the brightness is controlled by adjusting the time for turning on and off the light source, but under a single PWM frequency, the linear adjustment area is narrow, and the full-range linear adjustment cannot be met.
There is a need for a linear adjustment method of high-power light source brightness with low cost and fast response speed to meet the requirement of linear adjustment of light source brightness in mechanical vision application.
Disclosure of Invention
In view of the above problems, the present invention provides a linear adjustment method for brightness of a light source to improve the above problems.
In a first aspect, the present invention provides a method for linearly adjusting brightness of a light source, including the following steps:
s10: determining a target slope curve c0, wherein the target slope curve c0 corresponds to the PWM control frequency;
s20: according to a target slope curve c0 and the actually measured brightness curve slope k under different duty ratios 1 Adjusting the PWM frequency;
s30: and creating a PWM mixing frequency equation between the PWM mixing frequency and the PWM comparison frequency as well as the PWM frequency regulating quantity, and calculating the PWM mixing frequency to obtain a PWM output signal so as to regulate the linearity of the brightness of the light source.
More preferably, the steps between S20 and S30 further include,
secondarily adjusting the PWM frequency to compensate for the influence of the temperature change caused by the PWM frequency adjustment on the slope of the linear curve in step S20, based on the temperature negative feedback, wherein the PWM frequency adjustment amount in step S20 is a, the adjustment amount of the secondarily adjusted PWM frequency is B,
then, the PWM frequency adjustment amount in step S30 includes an adjustment amount a and a secondary adjustment amount B.
More preferably, step S10 includes:
s11: selecting an adjustable range of the PWM frequency according to actual requirements, and quantizing the adjustment level of the PWM frequency in the adjustable range;
s12: actually measuring a plurality of brightness curves of the light source from 0-100% under different quantization levels of the PWM frequency;
s13: determining a target slope curve c0 and a corresponding target slope k according to a plurality of actually measured brightness curves 0 。
More preferably, the target slope curve c0 has a target slope k 0 Step S20 includes:
s201: establishing a polynomial regression equation I reflecting the relation between the PWM frequency regulating quantity A and the PWM duty ratio;
s202: substituting a preset input PWM duty ratio into a polynomial regression equation I: a ═ q · (a) 1 +b 1 x+c 1 x 2 +d 1 x 3 +e 1 x 4 ) Determining a PWM frequency adjustment A, where a 1 、b 1 、c 1 、d 1 、e 1 Is the slope difference Δ k 1 And a polynomial regression statistical coefficient between the PWM duty ratio and the slope difference value delta k, wherein q is the PWM frequency value and the slope difference value delta k of different grades 1 Linear coefficient of between, Δ k 1 Is the slope k of the curve 1 And target slope k 0 The difference between them.
More preferably, the secondary adjustment PWM frequency process comprises:
s21: setting a temperature variation range, and quantizing the temperature grade in the temperature variation range;
s22: actually measuring the brightness curves corresponding to the different temperature levels, and determining the slope k of the curve corresponding to the brightness curves 2 Wherein the slope k of the curve 2 Determined by the value of temperature negative feedback;
s23: establishing a polynomial regression equation II reflecting the relation between the PWM frequency quadratic regulation quantity B and the temperature T, and obtaining the quadratic regulation quantity B according to the polynomial regression equation II, wherein the polynomial regression equation II satisfies the following conditions: b ═ a 2 T, wherein a 2 Is the product of m and n, m being the slope k of the curve 2 Slope k of the target curve 0 Difference value of (Δ k) 2 Linear coefficient with temperature T, n is PWM frequency regulation grade and slope difference value delta k 2 Linear coefficient in between.
More preferably, the second adjusting PWM frequency process comprises:
s21: setting a temperature variation range, and quantizing the temperature grade in the temperature variation range;
s22: actually measuring the brightness curves corresponding to the different temperature levels, and determining the slope k of the curve corresponding to the brightness curves 2 Wherein the slope k of the curve 2 Determined by the value of the temperature negative feedback;
s23: establishing a polynomial regression equation II reflecting the relation between the PWM frequency secondary regulation quantity B and the temperature T, and solving the secondary regulation quantity B according to the polynomial regression equation II, wherein the polynomial regression equation II satisfies a logistic curve formula: k/(1+ ae) -bT ) And K is the maximum PWM frequency regulating quantity, and the regression statistical coefficients a and b are obtained by combining the actually measured data according to the least square method.
More preferably, the PWM mixing frequency equation W ═ a 3 x+b 3 y+c 3 z, wherein x is the PWM reference frequency corresponding to the target slope curve c0, y is the PWM frequency adjustment quantity A, and z is the PWM frequency secondary adjustment quantity B, a 3 、b 3 、c 3 And carrying out weighted summation calculation according to the PWM mixing frequency equation to obtain the PWM output frequency W for the corresponding weighting coefficients.
Preferably, in step S30, the calculated PWM mixed frequency is output and then output together with the PWM duty ratio adjustment output value through the PWM output module, so as to obtain a PWM output signal.
In a second aspect, the present invention provides a linear adjusting system for light source brightness, including a parameter input port and a PWM frequency adjusting module, where the PWM frequency adjusting module includes a duty ratio/frequency conversion module, a target slope curve module, a frequency mixing analyzer, and a PWM output module, output ends of the duty ratio/frequency conversion module and the target slope curve module are respectively connected to the frequency mixing analyzer, an input end of the duty ratio/frequency conversion module is connected to the parameter input port, and an output end of the frequency mixing analyzer is connected to the PWM output module.
Preferably, the adjusting system further comprises a temperature sensing module, the PWM frequency adjusting module further comprises a temperature/frequency converting module, an input end of the temperature/frequency converting module is connected to the temperature sensing module, and an output end of the temperature/frequency converting module is connected to the frequency mixing analyzer.
The invention has the technical effects that: the invention provides a linear adjusting method of light source brightness, which has low cost, high response speed and good anti-interference performance by adjusting the linearity of the light source brightness through adjusting the PWM frequency;
the invention also obtains the adjusting method with wide linear adjusting range, high temperature feedback reliability and better anti-interference performance by adjusting the PWM frequency and the method of carrying out negative feedback secondary adjustment on the PWM frequency by temperature.
Drawings
FIG. 1 is a comparison graph of brightness curves at different PWM frequencies according to the present invention;
FIG. 2 is a comparison graph of brightness saturation at different temperatures according to the present invention;
FIG. 3 is a block diagram of a method for linear adjustment of brightness of a light source according to an embodiment of the present invention;
FIG. 4 is a block diagram of a method for linear adjustment of brightness of a light source according to another embodiment of the present invention;
FIG. 5 is a block diagram of a method for linear adjustment of brightness of a light source according to yet another embodiment of the present invention;
FIG. 6 is a system block diagram of a light source controller provided by the present invention;
fig. 7 is a system block diagram of a PWM frequency adjustment module according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
The invention provides a linear adjusting method of light source brightness, which comprises the following steps:
s10: determining a target slope curve c0, wherein the target slope curve c0 corresponds to the PWM control frequency; the objective of determining the target slope curve c0 is to preset a set of PWM frequency parameters for comparison, i.e., PWM comparison frequency. The process of determining the target slope curve c0 specifically includes:
s11: selecting an adjustable range of the PWM frequency according to actual requirements, and quantizing the adjustment grade of the PWM frequency in the adjustable range; in one embodiment, the adjustable range of the PWM frequency of a high-power light source is 50 KHz-150 KHz, and within the adjustable range of 50 KHz-150 KHz, the quantized PWM frequency is in three levels, namely 50KHz, 100KHz and 150KHz, wherein the finer the quantized level is, the better the adjustment result of the linearity is.
S12: measuring a plurality of brightness curves of the light source from 0-100% under different quantization levels of PWM frequency; namely, three luminance curves corresponding to the light source from 0 to 100% under the three quantization levels of 50KHz, 100KHz and 150KHz of the PWM frequency in step S11 are actually measured, as shown in fig. 1.
S13: determining a target slope curve c0 and a corresponding target slope k according to a plurality of actually measured brightness curves 0 (ii) a Specifically, the target slope curve c0, c0 is determined according to the respective intersections of the starting points and the end points of the three luminance curves obtained in step S12, c0 is shown by the dotted line in fig. 1, and the corresponding target slope k is obtained 0 And PWM versus frequency.
S20: according to the target slope curve c0 and the actually measured brightness curve slope k under different duty ratios 1 Adjusting the PWM frequency; it is mainly based on the actually measured slope k of the brightness curve under different duty ratios 1 And target slope k 0 The PWM frequency is adjusted by comparing the magnitude relation of the PWM frequency and the PWM frequency. Wherein, the adjustment quantity of the PWM frequency is a, and then obtaining the adjustment quantity a specifically includes:
s201: establishing a polynomial regression equation I reflecting the relation between the PWM frequency regulating quantity A and the PWM duty ratio, wherein PWM frequency values of different levels are PWM frequency initial values; the PWM duty ratio is input through a parameter input port after being set, and the target slope k 0 Determined by the plurality of actually measured brightness curves in step S13, wherein the actually measured brightness curves are mainly determined by the light source lamp beads V f Characteristics and power of the light source.
S202: and substituting the preset input PWM duty ratio into a polynomial regression equation I to obtain a PWM frequency regulating quantity A.
Specifically, the construction process of the polynomial regression equation I comprises the following steps:
build slope difference Δ k 1 And PWM duty cycle by a one-dimensional fourth order equation:
Δk 1 ＝a 1 +b 1 x+c 1 x 2 +d 1 x 3 +e 1 x 4
where x is the duty cycle, Δ k 1 Is the difference between the measured brightness curve slope k1 and the target slope k0 under different PWM frequency conditionsPolynomial regression statistic coefficient a 1 、b 1 、c 1 、d 1 、e 1 Then the least square method is used for solving;
further, the slope difference Δ k is further determined 1 Converting into PWM frequency regulating quantity A, and the difference value between the PWM frequency regulating quantity A and the slope 1 The relationship between them satisfies:
A＝q·Δk 1 ，
wherein q is a linear coefficient thereof, and the difference between the slope Δ k and the PWM frequency value with different quantization levels in step S12 1 Determining a corresponding curve of the measured data, and further determining a linear coefficient q;
then, the value of delta k 1 ＝a 1 +b 1 x+c 1 x 2 +d 1 x 3 +e 1 x 4 Substituting a ═ q · Δ k 1 The adjustment quantity A under different duty ratios can be obtained:
A＝q·(a 1 +b 1 x+c 1 x 2 +d 1 x 3 +e 1 x 4 )。
further, as can be seen from the luminance curve of 0-100% and the target slope curve c0 of the light source at different PWM frequencies shown in FIG. 1, adjusting the PWM frequency includes:
if k1< k0, increasing the PWM frequency;
if k1> k0, the PWM frequency is reduced.
Since the PWM brightness control method is sensitive to temperature variation, the slope of the linear curve after frequency modulation will increase due to temperature rise, and the maximum brightness will enter the saturation state in advance, as shown in fig. 2, if the brightness level is continuously increased, only the heat value of the high-power light source will be increased, and the brightness will not be increased. Further, the PWM frequency may be adjusted twice according to the temperature negative feedback to compensate the influence of the temperature change caused by the PWM frequency adjustment in step S20 on the slope of the linear curve, where the PWM frequency adjustment amount in step S20 is a, the PWM frequency adjustment amount in step S30 is B, and correspondingly, the PWM frequency adjustment amount in step S30 includes the adjustment amount a and the secondary adjustment amount is B. That is, the PWM frequency is adjusted by means of temperature negative feedback so as to keep the slope of the curve within a stable range, so as to compensate the influence of temperature variation on the slope of the luminance curve caused by the PWM frequency adjustment in step S20.
Wherein, secondarily adjusting the PWM frequency includes:
if the temperature rises, reducing the PWM frequency;
if the temperature decreases, the PWM frequency is increased.
Specifically, the specific process of determining the secondary adjustment amount B in the secondary adjustment of the PWM frequency includes:
s21: setting a temperature variation range, and quantizing the temperature grade in the temperature variation range; in one embodiment, the high power light source is in a temperature variation range of 25 ℃ to 75 ℃, and the temperature is specifically quantized into three grades, namely 25 ℃, 50 ℃ and 75 ℃.
S22: actually measuring brightness curves corresponding to the different temperature levels, and determining the slope k of the curve corresponding to the brightness curves 2 Wherein the slope k of the curve 2 Determined by the value of the temperature negative feedback; the corresponding brightness saturation curves at different temperatures are shown in fig. 2.
S23: and establishing a polynomial regression equation II reflecting the relation between the PWM frequency secondary regulating quantity B and the temperature T, and obtaining the secondary regulating quantity B according to the polynomial regression equation II.
First, the slope k of the luminance curve at different temperatures obtained by actual measurement 2 Slope k of the curve with respect to the target 0 Difference value of (Δ k) 2 Relationship with temperature T to build slope difference Δ k 2 Linear relationship with temperature T:
Δk 2 ＝mT；
substituting the measured data to determine a curve to obtain a linear coefficient m;
secondly, adjusting the grade and the slope difference value delta k according to the further constructed PWM frequency 2 The difference of the equations can be divided into different adjusting modes such as coarse adjustment, fine adjustment and the like to realize the calculation of the secondary adjusting quantity B;
specifically, during coarse tuning, the grade and the slope difference value delta k are further adjusted according to the PWM frequency 2 Corresponding measured data determination curveSlope n, then, the PWM frequency adjustment amount and the slope difference value delta k 2 The equation of (a) is:
B＝nΔk 2 ，
and will be Δ k 2 By substituting mT, the linear relationship between the PWM regulated quantity B and the temperature T can be determined: b ═ a 2 T, wherein a 2 Is the product of m and n;
specifically, at the time of fine adjustment, the PWM frequency adjustment level and the slope difference Δ k 2 Equation between and slope difference Δ k 2 And the equation Δ k between temperature T 2 After compounding mT, obtaining a S-shaped curve between PWM frequency regulating quantity B and temperature T, wherein the S-shaped curve is also called a growth curve:
the logistic curve formula is: k/(1+ ae) -bT ) And K is the maximum PWM frequency adjustment quantity, and the regression statistical coefficients a and B are obtained by combining the actually measured data according to a least square method, so that the relation between the PWM secondary adjustment quantity B and the temperature T is determined, and the corresponding PWM secondary adjustment quantity B can be obtained according to temperature negative feedback.
S30: and creating a PWM mixing frequency equation between the PWM mixing frequency and the PWM comparison frequency as well as the PWM frequency regulating quantity, and calculating the PWM mixing frequency to obtain a PWM output signal so as to regulate the linearity of the brightness of the light source. Let the PWM mixing frequency equation be: w ═ a 3 x+b 3 y+c 3 z, wherein x is the PWM comparison frequency corresponding to the target slope curve c0, the PWM comparison frequency is pre-stored in the target slope curve module, y is the PWM frequency adjustment quantity A, which is obtained by the duty ratio/frequency conversion module, and z is the PWM frequency secondary adjustment quantity B, a 3 、b 3 、c 3 Weighting and summing the corresponding weighting coefficients according to a PWM mixing frequency equation to obtain PWM mixing frequency, wherein the addition coefficient a is added because the PWM contrast frequency of the target slope curve can cause slight deviation of the output result due to the precision error of the electronic component 3 Correcting deviation in a small range; coefficient b 3 And coefficient c 3 The method aims to prevent the possible overshoot phenomenon of the PWM frequency regulation and the temperature feedback compensation regulation in the practical application process, thereby limiting the influence of the PWM frequency regulation amount and avoiding the over regulation.
As shown in fig. 3-4, fig. 3 is a block diagram of the method steps for adjusting the brightness linearity of the light source by PWM frequency adjustment in an embodiment, that is, when the temperature negative feedback duty ratio is 0; fig. 4 is a block diagram of a method for realizing linear adjustment of light source brightness by PWM frequency adjustment in another embodiment, in which a brightness curve of a high-power light source is corrected by the PWM frequency adjustment method, and the PWM frequency is adjusted by temperature negative feedback to eliminate the temperature influence caused by the change of the PWM frequency when the PWM frequency is initially adjusted. And further, the PWM mixed frequency and the PWM duty ratio regulation output value are output together through a PWM output module to obtain a PWM output signal, and the PWM output signal is transmitted to the high-power light source through the high-power driving module. Based on the fact that the brightness linearity of the light source is adjusted by utilizing the digital PWM duty ratio under the single PWM frequency, the slope of the brightness curve of the high-power light source is corrected by introducing the method for controlling the PWM frequency, so that the adjustment of the PWM duty ratio can be realized, meanwhile, the adjustment of the PWM frequency can be realized, under the combined action of the PWM duty ratio and the PWM frequency, the adjustment is carried out to the corresponding target value, the actually output brightness value is more close to the target slope curve, and the linear adjustment of the brightness in the full range is realized, and fig. 5 is a step block diagram of the method for realizing the linear adjustment of the brightness of the light source by combining the PWM duty ratio adjustment and the PWM frequency adjustment in the further embodiment.
Another aspect of the present invention further provides a linear adjusting system for light source brightness, as shown in fig. 6 to 7, the adjusting system is specifically a light source controller, and the light source controller includes a parameter input port, a PWM frequency adjusting module, a PWM duty ratio adjusting module, a PWM output module, an external trigger control module, an internal output control module, a high-power driving module, a high-power light source, and a temperature sensing module.
The output end of the parameter input port is connected with the input end of the PWM frequency adjusting module and the input end of the PWM duty ratio adjusting module respectively, the output end of the PWM frequency adjusting module and the output end of the PWM duty ratio adjusting module are connected with the PWM output module, and the PWM frequency adjusting module, the PWM duty ratio adjusting module, the PWM output module and the internal output control module form a single chip microcomputer or are integrated into a DSP chip. The output end of the external trigger control module and the output end of the internal output control module are both connected with the PWM output module, the output end of the PWM output module is connected with the input end of the high-power driving module, the output end of the high-power driving module is connected with the high-power light source, and the temperature sensing module is arranged at the high-power light source and connected with the PWM frequency adjusting module for negative feedback. The temperature sensing module is specifically a temperature sensor, consists of one or more contact temperature probes, is specifically connected with the input end of a temperature/frequency conversion module in the PWM frequency adjusting module, and provides temperature negative feedback for the PWM frequency control module. The PWM duty ratio adjusting module is used for setting the duty ratio of PWM, namely the ratio of the time of turning on and off a light source; the PWM output module can output a corresponding PWM output signal according to the PWM duty ratio and the PWM frequency parameter; the high-power driving module is a high-power output driving circuit mainly composed of MOSFET field effect transistors and used for driving a high-power supply; the parameter input port uses a conventional industrial communication interface to carry out parameter transmission control, and the interface can be a serial port, a network port, a 485 port and the like; the internal output control module is used for controlling the light source to be turned on or off; the external trigger control module allows the high-power light source to flash rapidly through an external trigger signal.
Further, the PWM frequency adjustment module includes a duty ratio/frequency conversion module, a target slope curve module, a temperature/frequency conversion module, and a frequency mixing analyzer, wherein an output end of the duty ratio/frequency conversion module, an output end of the target slope curve module, and an output end of the temperature/frequency conversion module are respectively connected to an input end of the frequency mixing analyzer, and an output end of the frequency mixing analyzer is connected to the PWM output module.
The digital PWM frequency regulation mode provided by the invention has the following advantages of regulating the linearity of the light source brightness:
1) the cost is low: compared with a constant current control mode, the digital PWM control mode uses fewer electronic components and is lower in hardware cost;
2) the response speed is high: the constant current control mode needs a short time delay to establish stable output, so that the output is correspondingly delayed, the time for establishing the stable output is short in the digital PWM control mode, and the corresponding output speed is higher than that in the constant current control mode;
3) the anti-interference performance is good: on one hand, the PWM frequency adjustment compensation is a digital compensation mode and is not greatly influenced by the precision of electronic components; on the other hand, the slope of the output curve is changed when the PWM frequency is adjusted, the slope of the output curve is also changed when the temperature change influence is changed, closed-loop negative feedback can be designed and formed by utilizing the PWM frequency adjustment and temperature negative feedback compensation, and the anti-interference capability is further improved.
4) The linear adjusting range is wide: although the constant current control mode has a wide brightness linear adjustment range, the full coverage of the output cannot be achieved from 0% to 100%, and the linear output full coverage can be achieved after the digital PWM control mode is compensated through temperature negative feedback;
5) the temperature feedback reliability is high: the temperature sensing technology is more mature than the optical sensing technology, the reliability is higher, and the design threshold of the temperature sensing technology is lower than that of the optical sensing technology, so that the temperature sensing technology is easier to realize.
In summary, the invention provides a linear adjustment method of light source brightness, which has low cost, high response speed and good anti-interference performance, and adjusts the linearity of the light source brightness by adjusting the PWM frequency; furthermore, an adjusting method which is wide in linear adjusting range, high in temperature feedback reliability and better in anti-interference performance is obtained by a method of adjusting PWM frequency and secondarily adjusting the PWM frequency through temperature negative feedback; the invention also provides a linear regulating system of the light source brightness, which has the advantages of low cost, high corresponding speed, wide linear regulating range, high temperature feedback reliability and good anti-interference performance.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not necessarily depart from the spirit and scope of the corresponding technical solutions.
Claims (9)
1. A linear regulation method for the brightness of a light source is characterized by comprising the following steps:
s10: determining a target slope curve c0, wherein the target slope curve c0 corresponds to the PWM control frequency;
s20: according to the target slope curve c0 and the actually measured brightness curve slope k under different duty ratios 1 Adjusting the PWM frequency;
s30: creating a PWM mixing frequency equation between the PWM mixing frequency and the PWM reference frequency as well as the PWM frequency regulating quantity, and calculating the PWM mixing frequency to obtain a PWM output signal so as to regulate the linearity of the light source brightness;
also included between the steps S20 and S30,
secondarily adjusting the PWM frequency according to temperature negative feedback to compensate for the influence of the temperature change caused by the PWM frequency adjustment on the slope of the linear curve in step S20, wherein the PWM frequency adjustment amount is a in step S20, the adjustment amount of the secondarily adjusted PWM frequency is B,
then, the PWM frequency adjustment amount in step S30 includes an adjustment amount a and a secondary adjustment amount B.
2. The linear adjustment method for brightness of light source according to claim 1, wherein step S10 comprises:
s11: selecting an adjustable range of the PWM frequency according to actual requirements, and quantizing the adjustment grade of the PWM frequency in the adjustable range;
s12: measuring a plurality of brightness curves of the light source from 0-100% under different quantization levels of PWM frequency;
s13: determining a target slope curve c0 and a corresponding target slope k according to a plurality of actually measured brightness curves 0 。
3. The method as claimed in claim 1, wherein the target slope curve c0 has a target slope k 0 Step S20 includes:
s201: establishing a polynomial regression equation I reflecting the relation between the PWM frequency regulating quantity A and the PWM duty ratio;
s202: substituting a preset input PWM duty ratio into a polynomial regression equation I: a ═ q · (a) 1 +b 1 x+c 1 x 2 +d 1 x 3 +e 1 x 4 ) Obtaining the PWM frequency adjustment quantity A, wherein a 1 、b 1 、c 1 、d 1 、e 1 Is the slope difference Δ k 1 And a polynomial regression statistical coefficient between the PWM duty ratio and the slope difference value delta k, wherein q is the PWM frequency value and the slope difference value delta k of different grades 1 Linear coefficient of between, Δ k 1 Is the slope k of the curve 1 And target slope k 0 The difference between them.
4. The linear adjustment method for brightness of light source according to claim 1, wherein the process of secondarily adjusting the PWM frequency comprises:
s21: setting a temperature variation range, and quantizing the temperature grade in the temperature variation range;
s22: actually measuring the brightness curves corresponding to the different temperature levels, and determining the slope k of the curve corresponding to the brightness curves 2 Wherein the slope k of the curve 2 Determined by the value of the temperature negative feedback;
s23: establishing a polynomial regression equation II reflecting the relation between the PWM frequency quadratic regulation quantity B and the temperature T, and solving the quadratic regulation quantity B according to the polynomial regression equation II, wherein the polynomial regression equation II satisfies the following conditions: b ═ a 2 T, wherein a 2 Is the product of m and n, m being the slope k of the curve 2 Slope k of the curve with respect to the target 0 Difference Δ k of 2 Linear coefficient with temperature T, n is PWM frequency regulation grade and slope difference value delta k 2 Linear coefficient in between.
5. The method of claim 1, wherein the step of adjusting the PWM frequency twice comprises:
s21: setting a temperature variation range, and quantizing the temperature grade in the temperature variation range;
s22: measured at different temperature levelsAnd determining the slope k of the curve corresponding to the respective luminance curve 2 Wherein the slope k of the curve 2 Determined by the value of the temperature negative feedback;
s23: establishing a polynomial regression equation II reflecting the relation between the PWM frequency secondary regulation quantity B and the temperature T, and solving the secondary regulation quantity B according to the polynomial regression equation II, wherein the polynomial regression equation II satisfies a logistic curve formula: k/(1+ ae) -bT ) And K is the maximum PWM frequency regulating quantity, and the regression statistical coefficients a and b are obtained by combining the actually measured data according to the least square method.
6. The method according to claim 1, wherein the PWM mixing frequency equation W ═ a 3 x+b 3 y+c 3 z, wherein x is the PWM reference frequency corresponding to the target slope curve c0, y is the PWM frequency adjustment quantity A, and z is the PWM frequency secondary adjustment quantity B, a 3 、b 3 、c 3 And carrying out weighted summation calculation according to the PWM mixing frequency equation to obtain the PWM output frequency W for the corresponding weighting coefficients.
7. The method for linearly adjusting the brightness of a light source according to any one of claims 1 to 6, wherein in step S30, the calculated PWM mixed frequency is outputted and then outputted together with the PWM duty ratio adjustment output value through the PWM output module, so as to obtain the PWM output signal.
8. A system for linearly adjusting the brightness of a light source, wherein the system for linearly adjusting the brightness of a light source is used to implement the method for linearly adjusting the brightness of a light source according to any one of claims 1 to 7, and the system for linearly adjusting the brightness of a light source includes a parameter input port and a PWM frequency adjustment module, the PWM frequency adjustment module includes a duty ratio/frequency conversion module, a target slope curve module, a frequency mixing analyzer and a PWM output module, output ends of the duty ratio/frequency conversion module and the target slope curve module are respectively connected to the frequency mixing analyzer, an input end of the duty ratio/frequency conversion module is connected to the parameter input port, and an output end of the frequency mixing analyzer is connected to the PWM output module.
9. The system of claim 8, wherein the system further comprises a temperature sensing module, the PWM frequency adjustment module further comprises a temperature/frequency conversion module, an input of the temperature/frequency conversion module is connected to the temperature sensing module, and an output of the temperature/frequency conversion module is connected to the frequency mixing analyzer.
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