CN115767814A - LED optical illumination curve calibration method and device and computer equipment - Google Patents
LED optical illumination curve calibration method and device and computer equipment Download PDFInfo
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Abstract
The invention discloses a method and a device for calibrating an LED optical illumination curve and computer equipment, wherein the method comprises the following steps: acquiring the maximum current flowing through the LED light source according to the waveform of the current flowing through the LED light source, and determining a first dimming gray level, wherein the first dimming gray level is the maximum dimming gray level of the current climbing section; calculating a first actual output power curve of the current climbing section according to the first dimming gray level, calculating a second actual output power curve of the constant current section according to the average current of the constant current section, and converting the first actual output power curve and the second actual output power curve into an actual optical illumination curve output by the LED light source in an equal proportion manner; and adjusting the dimming current according to the actual optical illumination curve so as to enable the LED light source to emit light accurately. The actual output power curve is calculated in a segmented mode in the current climbing section and the constant current section, so that the theoretical optical illumination curve is calibrated, the color mixing and color drifting of the LED light source are avoided, and the LED light source can emit light accurately.
Description
Technical Field
The invention relates to the field of circuits, in particular to a method and a device for calibrating an LED optical illuminance curve and computer equipment.
Background
At present, with the popularization of LED light sources, applications pursuing high-quality optical quality are increasing, and requirements for LED color mixing and dimming technologies are also increasing. The general method for dimming and color mixing of color LEDs is as follows: the method comprises the steps of firstly setting a linear or nonlinear theoretical optical illumination curve, converting the theoretical optical illumination curve into a digital PWM (pulse width modulation) signal which is in direct proportion to dimming gray level, driving a switch type LED constant-current driving circuit to enable an LED light source to emit light, realizing an energy conversion process that the dimming gray level signal is in direct proportion to LED input current, and further realizing the purposes of digital dimming and color mixing. The method for realizing color mixing for LED dimming by using the digital PWM modulation signal assumes that the average value of the current flowing through the LED is constant within the time range of 0-100% pulse width modulation, namely the PWM pulse width time is in absolute direct proportion to the output power of the constant current driver.
However, when the PWM pulse width is small, for example, 1/1000 or less, or the pulse width is less than 10us, the switching type constant current driving circuit is in the start-up operation state, and the current flowing through the LED is a pulse current generated by a switching surge response, and cannot reach the maximum average value of the constant current.
The current will have a ramp-up phase, in which the PWM pulse width is not directly proportional to the current flowing through the LED light source, which is the main reason why the color LED light source generates color mixing color drift during dimming at low brightness. The mixed color drift is a technical problem in the application of LED dimming, and the fundamental reason for generating low brightness color cast is that the response speed of the switch type constant current driving circuit to a narrow pulse signal is limited, the switch type constant current driving circuit is influenced by a choke inductance, and nonlinear current is output in a current climbing section, and the fundamental problem cannot be solved by a method for improving the circuit characteristic. The invention provides a method for adjusting an actual output optical curve of a current climbing section aiming at the current climbing section of a switch type constant current driving circuit, which realizes that the input PWM pulse width is 0-100% in direct proportion to the output power of a light source, thereby solving the problem of color mixing and color drift of LED low-brightness dimming.
In the existing LED dimming method, although the excitation signal set is adjusted by subdividing the dimming gray scale set according to the theoretical optical illuminance curve to realize the ideal undistorted optical curve effect, the current climbing stage generated by the pulse current is not considered, and the PWM pulse width and the current flowing through the LED light source are not in a direct proportion relation, so that the color mixing and color drift of the color LED light source are easily generated during low-brightness dimming.
Disclosure of Invention
The invention provides a method and a device for calibrating an LED optical illuminance curve and computer equipment, which are used for solving the technical problems that the PWM pulse width and the current flowing through an LED light source are not in a direct proportion relation in a current climbing stage, and color mixing and color drift are easy to generate.
In order to solve the above technical problem, in a first aspect, an embodiment of the present invention provides a method for calibrating an optical illuminance curve of an LED, including:
acquiring the maximum current flowing through the LED light source according to the current waveform flowing through the LED light source, and determining a first dimming gray level, wherein the first dimming gray level is the maximum dimming gray level of the current climbing section;
calculating a first actual output power curve of the current climbing section according to the first dimming gray level, calculating a second actual output power curve of the constant current section according to the average current of the constant current section, and converting the first actual output power curve and the second actual output power curve into an actual optical illumination curve output by the LED light source in an equal proportion manner;
and adjusting dimming current according to the actual optical illumination curve so as to enable the LED light source to emit light accurately.
According to the invention, the actual output power curve is calculated by segmenting the current climbing section and the constant current section, and the actual output power curve is converted into the actual optical illuminance curve through the direct proportional relation so as to calibrate the theoretical optical illuminance curve, so that the color mixing and color drift of the LED light source caused by the fact that the PWM pulse width of the current climbing section is not in the direct proportional relation with the current flowing through the LED light source are avoided, and the LED light source can accurately emit light.
Further, the calculating a first actual output power curve of the current climbing section according to the first dimming grayscale specifically includes:
inputting the first gray scale into a theoretical optical illumination curve to obtain first theoretical optical illumination;
obtaining the maximum current of a current climbing section according to a current waveform, and calculating a current change curve according to the maximum current and the first theoretical optical illuminance;
and calculating a first actual output power curve of the current climbing section according to the current change curve, wherein the first actual output power curve is a curve of the actual output power changing along with the change of the dimming gray level when the dimming gray level is less than or equal to the first gray level.
According to the invention, the current climbing section and the constant current section are distinguished through the first gray scale, and the current change curve of the climbing section is calculated according to the maximum current by utilizing the characteristic of the current waveform of the climbing section, so that the output power curve of the climbing section is obtained according to the current and power change relation, and the actual output power of the LED light source of the current climbing section is obtained.
Further, the calculating a second actual output power curve of the constant current section according to the average current of the constant current section specifically includes:
acquiring the average current of the constant current section according to the current waveform;
and calculating a second actual output power curve of the constant current section according to the average current and the first theoretical optical illuminance, wherein the second actual output power curve is a curve of which the actual output power changes along with the change of the dimming gray level when the dimming gray level is greater than the first gray level.
According to the invention, the average current of the constant current section is measured through the current waveform, and the output power curve of the constant current section is calculated through the current change curve of the constant current section so as to obtain the actual output power of the LED light source of the constant current section along with the current change.
Further, the proportionally converting the first actual output power curve and the second actual output power curve into an actual optical illuminance curve output by the LED light source specifically includes:
combining the first actual output power curve and the second actual output power curve to obtain a target actual output power curve, wherein the target actual output power curve is a curve that the actual output power changes along with the change of the dimming gray level within the theoretical dimming gray level;
and acquiring the proportional relation between the LED output power and the optical illumination, and converting a target actual output power curve according to the proportional relation to acquire an actual optical illumination curve.
According to the invention, the actual output power is calculated in a segmented manner, and the actual optical illuminance curve is obtained according to the proportional relation between the output power and the optical illuminance, so that the problems of LED light source color mixing and color drift caused by the fact that the PWM pulse width in the current climbing segment is not in direct proportional relation with the current flowing through the LED light source in dimming according to the optical illuminance curve are solved.
Further, before the obtaining a maximum current flowing through the LED light source according to a waveform of a current flowing through the LED light source and determining the first dimming grayscale, the method further includes:
acquiring a theoretical optical illumination curve output by the LED light source, and acquiring a theoretical optical illumination set according to the theoretical gray scale and the theoretical optical illumination curve;
and inputting the theoretical optical illumination set into a PWM modulator, driving a switch type constant current driver to output dimming current, and acquiring the waveform of the dimming current through a current oscilloscope, wherein the dimming current is the current flowing through an LED light source.
The invention drives the switch type constant current driver to output dimming current by taking the theoretical optical illumination set as an input value of the PWM modulator, so as to observe the waveform of the pulse current and obtain the data of a current climbing section and a constant current section.
Further, the adjusting of the dimming current according to the actual optical illuminance curve to enable the LED light source to emit light accurately specifically is:
acquiring an actual dimming gray scale corresponding to the theoretical optical illumination according to the theoretical optical illumination curve and the actual optical illumination curve;
and acquiring actual optical illumination according to the actual dimming gray scale, and driving a switch type constant current driver to output dimming current according to the actual optical illumination so as to enable the LED light source to emit light accurately.
Further, the obtaining of the actual dimming grayscale level corresponding to the theoretical optical illuminance according to the theoretical optical illuminance curve and the actual optical illuminance curve specifically includes:
inputting the theoretical dimming gray scale into a theoretical optical illumination curve to obtain a theoretical optical illumination set;
and inputting the theoretical optical illumination set into an actual optical illumination curve to obtain actual dimming gray levels corresponding to the theoretical optical illuminations in the theoretical optical illumination set.
Further, the actual optical illuminance is obtained according to the actual dimming grayscale, and the switching type constant current driver is driven according to the actual optical illuminance to output the dimming current, so that the LED light source emits light accurately, specifically:
inputting the actual dimming gray scale corresponding to each theoretical optical illumination into an actual optical illumination curve to obtain the actual optical illumination corresponding to the actual dimming gray scale;
and inputting the actual optical illumination into a PWM (pulse-width modulation) modulator to drive a switch type constant current driver to output an actual dimming current corresponding to the theoretical optical illumination so as to enable the LED light source to emit light accurately.
According to the invention, the actual optical illuminance curve is obtained by calibrating the theoretical optical illuminance curve, and the dimming current is driven and output by the PWM modulator according to the change of the actual optical illuminance curve, so that the problems of color mixing and color drift of the LED light source caused by the fact that the current is output according to the theoretical optical illuminance curve are solved.
In a second aspect, an embodiment of the present invention provides an apparatus for calibrating an optical illuminance curve of an LED, including: the device comprises a current data acquisition module, an optical illumination curve calculation module and a driving module;
the current data acquisition module is used for acquiring the maximum current flowing through the LED light source according to the current waveform flowing through the LED light source and determining a first dimming gray level, wherein the first dimming gray level is the maximum dimming gray level of the current climbing section;
the optical illumination curve calculation module is used for calculating a first actual output power curve of the current climbing section according to the first dimming gray level, calculating a second actual output power curve of the constant current section according to the average current of the constant current section, and converting the first actual output power curve and the second actual output power curve into an actual optical illumination curve output by the LED light source in an equal proportion manner;
and the driving module is used for adjusting dimming current according to the actual optical illumination curve so as to enable the LED light source to emit light accurately.
In a third aspect, an embodiment of the present invention provides a computer device, including: the LED optical illumination curve calibration device comprises a processor, a communication interface and a memory, wherein the processor, the communication interface and the memory are connected with each other, executable program codes are stored in the memory, and the processor is used for calling the executable program codes and executing the LED optical illumination curve calibration method.
Drawings
Fig. 1 is a schematic flowchart of a method for calibrating an optical illuminance curve of an LED according to an embodiment of the present invention;
fig. 2 is a schematic current waveform diagram of a method for calibrating an optical illuminance curve of an LED according to an embodiment of the present invention;
fig. 3 is a graph of an optical illuminance at step 103 according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an LED optical illuminance curve calibration apparatus according to an embodiment of the present invention;
fig. 5 is a schematic flowchart of a method for calibrating an optical illuminance curve of an LED according to a second embodiment of 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 derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
Referring to fig. 1, fig. 1 is a schematic flow chart of a method for calibrating an optical illuminance curve of an LED according to an embodiment of the present invention, which includes steps 101 to 103, and specifically includes the following steps:
step 101: acquiring the maximum current flowing through the LED light source according to the waveform of the current flowing through the LED light source, and determining a first dimming gray level, wherein the first dimming gray level is the maximum dimming gray level of the current climbing section;
in this embodiment, before the obtaining the maximum current flowing through the LED light source according to the waveform of the current flowing through the LED light source and determining the first dimming grayscale, the method further includes:
acquiring a theoretical optical illumination curve output by the LED light source, and acquiring a theoretical optical illumination set according to a theoretical gray scale and the theoretical optical illumination curve;
and inputting the theoretical optical illumination set into a PWM modulator, driving a switch type constant current driver to output dimming current, and acquiring the waveform of the dimming current through a current oscilloscope, wherein the dimming current is the current flowing through an LED light source.
In this embodiment, the theoretical gray scale is input into a theoretical optical illuminance curve to obtain a theoretical optical illuminance.
In the present embodiment, a theoretical optical illuminance mapping curve equation Y (x) of the LED light source output is preset, and the LED light source output illuminance is expected to change along with the curve equation Y (x). Y (x) may be a straight line or a non-linear curve type, and the value of Y (x) represents a proportional relationship with the actual illuminance L (x), provided that L (x) is the actual optical illuminance equation, L (x) = Y (x) × η, η is a proportionality constant. The value range of the curve equation Y (x) is Y (x) epsilon (0, ymax), and the maximum value Ymax =65535. Wherein the variable x is an input dimming gray level, x ∈ (0, gmax), and the maximum gray level Gmax =255, Y (x), x and the related constant jointly generate an optical illuminance curve equation Y (x); inputting variable x values of 0-255, generating a data set Y [ x ] by a curve equation Y (x), wherein for calculation convenience, Y (x) = Y [ x ] obtained by table lookup of values corresponding to Y (x), and the Y [ x ] is a theoretical optical illumination set.
In this embodiment, the MCU controller sets PWM input variable to PWM range, PWM range PWM belongs to (0, ymax), and the PWM range is the same as the value range of the curve equation Y (x).
In this embodiment, by looking up a table, a theoretical optical illumination set yx is queried according to a dimming gray level x, a corresponding illumination value yx is found, the yx value is assigned to a PWM pulse width modulator as a dimming sub-level, a PWM pulse width modulation signal is generated to drive a switching constant current driving circuit, and the switching constant current driving circuit outputs a dimming current in proportion to the PWM pulse width modulation signal.
Referring to fig. 2, fig. 2 is a schematic current waveform diagram of a method for calibrating an LED optical illuminance curve according to an embodiment of the present invention.
In this embodiment, a current oscilloscope is used to measure and record dimming gray level x = N required by a current climbing section, where N is a first dimming gray level, the dimming gray level is smaller than N, the current climbing section is used, and the dimming gray level is larger than N, the current climbing section is used as a constant current driving section; and searching N to obtain a corresponding illuminance curve set Y [ x ] with a value Y [ N ], wherein Y [ N ] is a PWM input value of the current rising to the maximum value Imax.
In this embodiment, the theoretical power equation output by the LED driver is specifically as follows:
P(x)＝Uf*Imax*Pwm(x) (1)
wherein Pwm (x) is a pulse width modulation function, pwm (x) = Y (x)/Ymax, uf is the LED light source voltage drop, imax is the driving output average current, x is the dimming gray-scale variable, Y (x) is the PWM modulator input variable value, and Ymax is the PWM modulation maximum amplitude.
Then the LED driver output power equations can be combined as:
P(x)＝(Uf*Imax*/Ymax)*Y(x) (2)
P(x)＝μ*Y(x) (3)
wherein μ = Uf max/Ymax, μ is constant.
In this embodiment, the LED driver output power P (x) varies in direct proportion to the curve equation Y (x). Then the power equation can be converted to:
P(x)＝(Uf/Ymax)*S (4)
wherein S = Imax × Y (x), S is a rectangular area formed by the average current Imax and the pulse width modulation input variable Y (x), and the S area reflects a process in which the output power is accumulated as the pulse width modulation input variable Y (x) changes.
Step 102: calculating a first actual output power curve of the current climbing section according to the first dimming gray level, calculating a second actual output power curve of the constant current section according to the average current of the constant current section, and converting the first actual output power curve and the second actual output power curve into an actual optical illumination curve output by the LED light source in an equal proportion;
in this embodiment, it is necessary to generate the actual optical illuminance mapping curve equation YA (x) of the LED light source output. And respectively calculating an actual output power curve equation P (x) of the current climbing section and the constant current section, and converting the power curve equation P (x) into an actual optical illumination mapping curve equation YA (x) output by the equal-proportion LED light source.
In this embodiment, the calculating a first actual output power curve of the current climbing segment according to the first dimming grayscale specifically includes:
inputting the first gray scale into a theoretical optical illumination curve to obtain first theoretical optical illumination;
obtaining the maximum current of a current climbing section according to a current waveform, and calculating a current change curve according to the maximum current and first theoretical optical illuminance;
and calculating a first actual output power curve of the current climbing section according to the current change curve, wherein the first actual output power curve is a curve of the actual output power changing along with the change of the dimming gray level when the dimming gray level is less than or equal to the first gray level.
In the present embodiment, the current waveform approximates a perfect triangular waveform before the current climbs to the maximum value Imax in the current climbing section, so that the current curve is the hypotenuse of a right triangle. And (3) measuring the maximum value Imax of the average current, wherein the output current I (x) of the constant-current driver in the current climbing section is changed along with the PWM modulation variable Y (x), and the specific formula of I (x) is as follows:
I(x)＝(Imax/Y(N))*Y(x)，x<＝N (5)
since the drive output current I (x) is now varied, it is no longer a constant Imax. Equation 4 yields:
P1(x)＝(Uf/Ymax)*S1 (6)
S1＝I(x)*Y(x)/2；x<＝N (7)
wherein S1 is the triangular area formed by the variable current I (x) and the pwm input variable Y (x).
Namely, the first actual output power curve is specifically:
P1(x)＝(Uf/Ymax)*Imax*Y(x)*Y(x)/Y(N)/2；x<＝N (8)
P1(x)＝μ*(Y(x)*Y(x)/Y(N)/2)；x<＝N (9)
in this embodiment, since the current of the constant current section is constant at Imax, equation 4 can obtain a power equation of the constant current section, specifically:
P2(x)＝(Uf/Ymax)*S2 (10)
S2＝Imax*(Y(x)-Y(N)),x>N (11)
namely, the second actual output power curve is specifically:
P2(x)＝(Uf/Ymax)*Imax*(Y(x)-Y(N))；x>N (12)
P2(x)＝μ*(Y(x)-Y(N))；x>N (13)
in this embodiment, the proportionally converting the first actual output power curve and the second actual output power curve into an actual optical illuminance curve output by the LED light source specifically includes:
combining the first actual output power curve and the second actual output power curve to obtain a target actual output power curve, wherein the target actual output power curve is a curve that the actual output power changes along with the change of the dimming gray level within the theoretical dimming gray level;
and acquiring the proportional relation between the LED output power and the optical illumination, and converting a target actual output power curve according to the proportional relation to acquire an actual optical illumination curve.
In the present embodiment, the actual optical illuminance mapping curve YA (x) of the LED light source output is calculated.
Combining the first actual output power curve and the second actual output power curve, the following can be obtained:
according to equation 3: p (x) = μ × Y (x), and since μ = Uf × Imax/Ymax are all fixed constants after circuit parameters are fixed, the values of Uf, imax, ymax are all fixed constants, so μ is also a fixed constant, and μ is assumed to be 1 for convenience of calculation. The actual optical illuminance mapping curve YA (x) output by the actual LED light source is specifically:
power equation (6):
inputting variable x values of 0-255, and generating an actual illumination set YA [ x ] by a curve equation YA (x);
step 103: and adjusting dimming current according to the actual optical illumination curve so as to enable the LED light source to emit light accurately.
In this embodiment, the adjusting the dimming current according to the actual optical illuminance curve to enable the LED light source to emit light accurately includes:
acquiring an actual dimming gray scale corresponding to the theoretical optical illumination according to the theoretical optical illumination curve and the actual optical illumination curve;
and acquiring actual optical illumination according to the actual dimming gray level, and driving a switch type constant current driver to output dimming current according to the actual optical illumination so as to enable the LED light source to emit light accurately.
In this embodiment, the obtaining an actual dimming grayscale level corresponding to the theoretical optical illuminance according to the theoretical optical illuminance curve and the actual optical illuminance curve specifically includes:
inputting the theoretical dimming gray scale into a theoretical optical illumination curve to obtain a theoretical optical illumination set;
and inputting the theoretical optical illumination set into an actual optical illumination curve to obtain actual dimming gray levels corresponding to each theoretical optical illumination in the theoretical optical illumination set.
In this embodiment, the obtaining of the actual optical illuminance according to the actual dimming grayscale level and the driving of the switching type constant current driver according to the actual optical illuminance to output the dimming current so as to enable the LED light source to emit light accurately specifically include:
inputting the actual dimming gray scale corresponding to each theoretical optical illumination into an actual optical illumination curve to obtain the actual optical illumination corresponding to the actual dimming gray scale;
and inputting the actual optical illumination into a PWM (pulse-width modulation) modulator to drive a switch type constant current driver to output an actual dimming current corresponding to the theoretical optical illumination so as to enable the LED light source to emit light accurately.
As a specific example of the embodiment of the present invention, referring to fig. 3, fig. 3 is a graph of an optical illuminance curve in step 103 according to the embodiment of the present invention.
In this embodiment, the set YA [ x ] of the actual optical illuminance curve values is back-checked by the theoretical optical illuminance set Y [ x1] to obtain the accurate dimming gray-level value x2.
In this embodiment, a theoretical dimming grayscale is input into a theoretical optical illumination curve to obtain a theoretical optical illumination set Y [ x ], and then a dimming grayscale x = x1 is input into the theoretical optical illumination set Y [ x ], so as to obtain a mapping illumination value Y [ x1]; inputting the mapping illumination value Y [ x1] into an actual optical illumination curve data set YA [ x ], and reversely checking a corresponding dimming gray scale level x = x2 on the mapping curve data set YA [ x ] where the mapping illumination value Y [ x1] is located; inputting x = x2 into an actual mapping curve data set YA [ x ], obtaining an actual mapping illumination value YA [ x2], inputting YA [ x2] into a PWM (pulse-width modulation) pulse-width modulator, and obtaining accurate illumination of an actual full-power section, thereby solving the problem of color drift of low-brightness mixed color.
In the embodiment, the actual output power curve is calculated in a segmented manner by the current climbing section and the constant current section, and the actual output power curve is converted into the actual optical illuminance curve through the direct proportional relationship to calibrate the theoretical optical illuminance curve, so that the color mixing and color drift of the LED light source caused by the fact that the PWM pulse width of the current climbing section is not in the direct proportional relationship with the current flowing through the LED light source are avoided, and the LED light source can emit light accurately.
Referring to fig. 4, fig. 4 is a schematic structural diagram of an LED optical illuminance curve calibration apparatus according to an embodiment of the present invention, which mainly includes a current data obtaining module 401, an optical illuminance curve calculating module 402, and a driving module 403;
the current data obtaining module 401 is configured to obtain a maximum current flowing through the LED light source according to a waveform of the current flowing through the LED light source, and determine a first dimming grayscale, where the first dimming grayscale is a maximum dimming grayscale of a current climbing section;
the optical illuminance curve calculating module 402 is configured to calculate a first actual output power curve of the current climbing section according to the first dimming grayscale, calculate a second actual output power curve of the constant current section according to the average current of the constant current section, and proportionally convert the first actual output power curve and the second actual output power curve into an actual optical illuminance curve output by the LED light source;
the driving module 403 is configured to adjust a dimming current according to the actual optical illuminance curve, so that the LED light source emits light accurately.
An embodiment of the present invention further provides a computer device, including: the LED optical illuminance curve calibration device comprises a processor, a communication interface and a memory, wherein the processor, the communication interface and the memory are connected with each other, the memory stores executable program codes, and the processor is used for calling the executable program codes and executing the LED optical illuminance curve calibration method.
Example two
As a specific example of the embodiment of the present invention, referring to fig. 5, fig. 5 is a schematic flow chart of a method for calibrating an optical illuminance curve of an LED according to the embodiment of the present invention, which mainly includes steps 501 to 502, and specifically includes the following steps:
step 501: preset theoretical optical illuminance mapping equation Y (x):
Y(x)＝a*x*x； (16)
wherein the coefficient a =1.007843, x ∈ (0, 255).
In the present embodiment, a theoretical optical illuminance mapping equation data set (in integers) Y [ x ] = {1,4,9,16,25,36,49,65,82,101,122,145,170,198 \8230;, 65535} is generated from equation Y (x).
Step 502: the switching type constant current driver is driven to output dimming current. Inputting the dimming gray scale x into the data set Yx, changing the gray variable x from 0-255, finding out the value corresponding to Yx, and inputting Yx into the PWM modulator to drive the switch type constant current driver to output the dimming current.
Step 503: acquiring a current waveform flowing through the LED light source by using an oscilloscope, and recording a dimming gray level x = N value required by the current to climb to the maximum value, wherein if N =30, a current climbing section is the dimming gray value smaller than 30, and a constant current section is the dimming gray value larger than 30. Look up data set Y [ x ], Y [30] =907.
Step 504: and calculating an actually output optical illumination mapping equation data set. According to the actual optical illuminance mapping curve equation YA (x):
in this embodiment, an optical illuminance mapping equation data set that is actually output is calculated, where the optical illuminance mapping equation data set specifically includes:
YA[x]＝{0.0006,0.01,0.05,0.14,0.35,0.73,1.34,2.29,3.67,5.60,8.20,11.61,…,65535}
since the YA [ Gmax ] value does not reach the maximum value 65535 when x = Gmax maximum gray scale, but the PWM pulse width reaches 100%, the driving output current waveform is a straight line without falling edges, so x = Gmax, and YA [ Gmax ] is forcibly assigned 65535.
Step 505: and driving the LED light source to emit light according to the actual optical illumination. First, a dimming gray level x1=40 is input into a theoretical optical illuminance mapping curve set Y [ x ], Y [40] =1613 is obtained, then the dimming gray level is input into a set YA [ x ] =1613, a gray value x2 corresponding to an actual illuminance mapping curve set YA [ x ], YA [45] =1588, YA [46] =1680 is obtained by reversely checking that the gray value x2 is between 45 and 46, the gray value x2 can be further subdivided into 16-bit gray values, and a two-dimensional array of two bytes is used to represent the gray value: d [ x, ux ]; where x2 is a lower integer part corresponding to a point on the YA [ x ], x =45, and ux is a ratio value obtained by dividing the YA [ x ] and YA [ x +1] by 255. The calculation formula of the ux value is as follows:
ux＝(Y[x1]-YA[x2])*255/(YA[x+1]-YA[x])；ux∈(0,255) (18)
ux＝(Y[40]-YA[45])*255/(YA[46]-YA[45])＝69 (19)
thus, the dimming grayscale x2 can be represented as D [45, 69] by a two-dimensional array D [ x, ux ]; therefore, the dimming process is to convert the input dimming gray scale x1 into another gray scale x2, x2 is represented by a two-dimensional array D [ x, ux ], then the gray scale D [ x, ux ] is input into a data set YA [ x ], a corresponding YA [ x2] value is obtained, and the YA [ x2] value is input into a PWM (pulse-width modulation) for dimming output of the switch type constant current driving circuit. The gray value D [ x, ux ] input data set YA [ x ] calculation formula specifically comprises:
YA[x2]＝(YA[x+1]-YA[x])*ux/255 (20)
in the present embodiment, D [45, 69] is input to the actual illuminance curve set YA [ x ], and YA [ x2] =1613 is calculated; the value YA x2 is input to the PWM pulse width modulator to drive the LED light source to emit light, and the LED light source can output 1613 mapping illumination value which is the same as the value of the theoretical optical illumination curve Y (x).
In this embodiment, an input gray value x1=40 is obtained by performing look-up table and calculation conversion on the input gray value x2= D [45, 69], a value YA [ x2] is obtained by looking up an actual illuminance curve set YA [ x ] from the gray value x2, the value YA [ x2] is input to a PWM pulse width modulator, a PWM pulse width modulation signal is generated to drive a switching type constant current circuit, and a dimming current is output to drive an LED light source to emit light.
In this embodiment, the output current of the constant current driver is calculated in two stages, i.e., a current ramp-up stage and a constant current stage, within one PWM period. And the current climbing section and the constant current section use different power calculation equations to finally synthesize a constant current driver output power calculation equation which is consistent with the actual output power in a PWM period. Because the output optical illumination of the LED light source is in a direct proportional relation with the input power, the LED input power equation is the equation of the LED output optical illumination curve. And then, the actually output optical illumination curve table is inversely checked according to the required optical illumination to obtain the actually required PWM (pulse width modulation) gray level, so that accurate dimming is realized.
The above-mentioned embodiments are provided to further explain the objects, technical solutions and advantages of the present invention in detail, and it should be understood that the above-mentioned embodiments are only examples of the present invention and are not intended to limit the scope of the present invention. It should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. An LED optical illumination curve calibration method is characterized by comprising the following steps:
acquiring the maximum current flowing through the LED light source according to the current waveform flowing through the LED light source, and determining a first dimming gray level, wherein the first dimming gray level is the maximum dimming gray level of the current climbing section;
calculating a first actual output power curve of the current climbing section according to the first dimming gray level, calculating a second actual output power curve of the constant current section according to the average current of the constant current section, and converting the first actual output power curve and the second actual output power curve into an actual optical illumination curve output by the LED light source in an equal proportion manner;
and adjusting the dimming current according to the actual optical illuminance curve so as to enable the LED light source to emit light accurately.
2. The method for calibrating an LED optical illuminance curve according to claim 1, wherein the calculating a first actual output power curve of a current ramp segment according to the first dimming grayscale level specifically comprises:
inputting the first gray scale into a theoretical optical illumination curve to obtain first theoretical optical illumination;
obtaining the maximum current of a current climbing section according to a current waveform, and calculating a current change curve according to the maximum current and the first theoretical optical illuminance;
and calculating a first actual output power curve of the current climbing section according to the current change curve, wherein the first actual output power curve is a curve of the actual output power changing along with the change of the dimming gray level when the dimming gray level is less than or equal to the first gray level.
3. The method for calibrating an optical illuminance curve of an LED according to claim 2, wherein the calculating a second actual output power curve of the constant current section according to the average current of the constant current section specifically comprises:
acquiring the average current of the constant current section according to the current waveform;
and calculating a second actual output power curve of the constant current section according to the average current and the first theoretical optical illuminance, wherein the second actual output power curve is a curve of which the actual output power changes along with the change of the dimming gray level when the dimming gray level is greater than the first gray level.
4. The method for calibrating an LED optical illuminance curve as claimed in claim 3, wherein the step of converting the first actual output power curve and the second actual output power curve into the actual optical illuminance curve output by the LED light source in an equal proportion specifically comprises:
combining the first actual output power curve and the second actual output power curve to obtain a target actual output power curve, wherein the target actual output power curve is a curve that the actual output power changes along with the change of the dimming gray level within the theoretical dimming gray level;
and acquiring the proportional relation between the LED output power and the optical illumination, and converting a target actual output power curve according to the proportional relation to acquire an actual optical illumination curve.
5. The method for calibrating an LED optical illuminance curve as claimed in claim 1, further comprising, before the step of obtaining the maximum current flowing through the LED light source according to the waveform of the current flowing through the LED light source and determining the first dimming gray scale level:
acquiring a theoretical optical illumination curve output by the LED light source, and acquiring a theoretical optical illumination set according to a theoretical gray scale and the theoretical optical illumination curve;
and inputting the theoretical optical illumination set into a PWM (pulse-width modulation) modulator, driving a switch type constant current driver to output dimming current, and acquiring the waveform of the dimming current through a current oscilloscope, wherein the dimming current is the current flowing through an LED light source.
6. The method for calibrating an LED optical illuminance curve according to claim 1, wherein the adjusting the dimming current according to the actual optical illuminance curve to make the LED light source emit light accurately comprises:
acquiring an actual dimming gray level corresponding to the theoretical optical illumination according to the theoretical optical illumination curve and the actual optical illumination curve;
and acquiring actual optical illumination according to the actual dimming gray level, and driving a switch type constant current driver to output dimming current according to the actual optical illumination so as to enable the LED light source to emit light accurately.
7. The method for calibrating an LED optical illuminance curve according to claim 6, wherein the obtaining an actual dimming grayscale level corresponding to a theoretical optical illuminance according to the theoretical optical illuminance curve and the actual optical illuminance curve specifically includes:
inputting the theoretical dimming gray scale into a theoretical optical illumination curve to obtain a theoretical optical illumination set;
and inputting the theoretical optical illumination set into an actual optical illumination curve to obtain actual dimming gray levels corresponding to the theoretical optical illuminations in the theoretical optical illumination set.
8. The method for calibrating an LED optical illuminance curve according to claim 7, wherein the obtaining an actual optical illuminance according to the actual dimming grayscale level and driving a switching type constant current driver to output a dimming current according to the actual optical illuminance so as to enable an LED light source to emit light accurately includes:
inputting the actual dimming gray scale corresponding to each theoretical optical illumination into an actual optical illumination curve to obtain the actual optical illumination corresponding to the actual dimming gray scale;
and inputting the actual optical illumination into a PWM (pulse-width modulation) modulator to drive a switch type constant current driver to output an actual dimming current corresponding to the theoretical optical illumination so as to enable the LED light source to emit light accurately.
9. An LED optical illuminance curve calibration device, comprising: the device comprises a current data acquisition module, an optical illumination curve calculation module and a driving module;
the current data acquisition module is used for acquiring the maximum current flowing through the LED light source according to the current waveform flowing through the LED light source and determining a first dimming gray level, wherein the first dimming gray level is the maximum dimming gray level of the current climbing section;
the optical illumination curve calculation module is used for calculating a first actual output power curve of the current climbing section according to the first dimming gray level, calculating a second actual output power curve of the constant current section according to the average current of the constant current section, and converting the first actual output power curve and the second actual output power curve into an actual optical illumination curve output by the LED light source in an equal proportion manner;
and the driving module is used for adjusting the dimming current according to the actual optical illuminance curve so as to enable the LED light source to emit light accurately.
10. A computer device, comprising: a processor, a communication interface and a memory, the processor, the communication interface and the memory being interconnected, wherein the memory stores executable program code, and the processor is configured to invoke the executable program code to perform the LED optical luminance curve calibration method as claimed in any one of claims 1 to 8.
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