CN111312180A - PWM compensation method and device for ultra-long service life LED backlight source controlled by MCU - Google Patents
PWM compensation method and device for ultra-long service life LED backlight source controlled by MCU Download PDFInfo
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- CN111312180A CN111312180A CN202010198868.2A CN202010198868A CN111312180A CN 111312180 A CN111312180 A CN 111312180A CN 202010198868 A CN202010198868 A CN 202010198868A CN 111312180 A CN111312180 A CN 111312180A
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/3406—Control of illumination source
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
Abstract
A PWM compensation method and device for an ultra-long service life LED backlight source controlled by an MCU (microprogrammed control Unit) are characterized in that on the basis of a normal backlight source brightness attenuation curve, according to the input backlight source accumulation time of a display MCU, bright X0 … X70 corresponding to each month is collected on the attenuation curve, and corresponding brightness Y0 … Y70 is stored in a FLASH of the MCU; decay rate for each day: the attenuation rate is converted into a value Bn corresponding to a 16-bit register, an MCU of the display mediates a current compensation value I of the PWM according to the value Bn corresponding to each time, and the I is increased in proportion with the increase of the Bn; the larger Bn is, the larger current compensation value I of PWM is, so that the compensated backlight source attenuation curve keeps straight. The algorithm automatically compensates the attenuation of the backlight source (inverse attenuation curve of the backlight source) through PWM, so that the backlight source keeps constant brightness for a long time and the brightness of the backlight source is more stable compared with other backlight sources with long service life.
Description
Technical Field
The invention relates to the technical field of liquid crystal displays, in particular to a PWM (pulse-width modulation) compensation method and device for an LED backlight source with an ultra-long service life controlled by an MCU (microprogrammed control Unit).
Background
The display can be regarded as a 'face' of an electronic product, along with the trend of more portability of the electronic product, the frequency of the liquid crystal display is higher and higher in the application occasions of portable communication equipment, portable instruments and meters, ship equipment and the like, and meanwhile, the requirement on the service life of the display is higher and higher. The main factors influencing the display are the service life of the backlight source, the service life of the backlight source is defined as the duration of the brightness reduced to 50 percent of the original brightness when the rated current works, the conventional service life is 2 ten thousand hours, 5 to 10 ten thousand hours are required for industrial control and vehicle-mounted display screens, the conventional realization scheme adopts the measures of selecting a brand wick, adopting materials with good heat conduction area, increasing the heat dissipation area and the like, and the display has the advantages of complex physical structure, large volume and high mold opening cost.
Disclosure of Invention
In order to solve the technical problems in the background art, the invention provides a PWM compensation method and device for an LED backlight source with an ultra-long service life controlled by an MCU (microprogrammed control Unit). The algorithm automatically compensates the attenuation of the backlight source (the attenuation curve of the inverse backlight source) through PWM so that the backlight source keeps constant brightness for a long time, and the brightness is more stable compared with other backlight sources with a long service life.
In order to achieve the purpose, the invention adopts the following technical scheme:
a PWM compensation method for an LED backlight source with an ultra-long service life controlled by an MCU comprises the following steps:
1) collecting brightness Y0 … Y70 corresponding to each month of X0 … X70 on the attenuation curve and storing the brightness Y0 … Y70 into a FLASH of the MCU according to the input backlight accumulated time of the display MCU on the basis of a normal backlight brightness attenuation curve;
the brightness corresponding to each month is cut out from the curve, the X axis is the month, the Y axis is the brightness, and n is the month, and the following table is established:
2) with (X)n，Yn) The coordinates of each point are connected by straight lines to form 70 straight line segments, and the brightness change of each month is approximately considered to be linear;
3) decay rate for each day:
An＝(Yn-1-Yn)/(Y0*30)
4) the decay rate is translated into a value corresponding to a 16-bit register:
Bn＝An*65535
5) the MCU of the display calculates the Bn corresponding to each time according to the acquisition time, and the Bn value is unchanged within 30 days;
the MCU of the display mediates a current compensation value I of the PWM according to a Bn value corresponding to each time, wherein the I is increased in proportion with the increase of the Bn; the larger Bn is, the larger current compensation value I of PWM is, so that the compensated backlight source attenuation curve keeps straight.
The PWM duty ratio is initially set to be 50%, the PWM duty ratio is increased from 50% to 100% within 70 months of compensation time, and backlight source attenuation is compensated.
The number of lamp wicks of the backlight source adopts an excess design, namely the number of the lamp wicks is 50% more than that of the common backlight source, the backlight source is ensured to work under the condition of lower than rated current, the target brightness is realized, so that a regulating space is reserved for PWM regulation, and when the PWM is regulated to the top limit of 100%, the regulation is stopped and the backlight source enters the natural attenuation of the common backlight source along with the time lapse.
The backlight control device for realizing the MCU-controlled ultra-long-life LED backlight PWM compensation method comprises an MCU controller with a real-time clock, an LED driver and an LED backlight, wherein the output end of the MCU controller is connected with the LED driver and is connected to the LED backlight through the LED driver. The MCU controller also comprises an ambient light sensor, and the ambient light sensor is connected with the input port of the MCU controller.
Compared with the prior art, the invention has the beneficial effects that:
1) the algorithm of the invention automatically compensates the attenuation of the backlight source (the attenuation curve of the inverse backlight source) through PWM, so that the backlight source keeps constant brightness for a long time, and the brightness is more stable compared with other long-life backlight sources, meanwhile, the backlight source can adopt an excess design, the number of lamp wicks is 50% more than that of a common backlight source, the backlight source is ensured to work under the condition of lower than rated current, the target brightness is realized, so that a mediation space is reserved for PWM regulation, and when the PWM is regulated to the uppermost limit along with the time lapse, the regulation is stopped, and the natural attenuation of the common backlight source is;
2) a real-time clock is arranged in the MCU and can record and accumulate the working time of the backlight source;
3) the PWM function of the MCU is adopted, a 16-bit register is arranged inside the MCU, the precision is 1/65535, and the precision can reach 0.2 ten-thousandth.
Drawings
FIG. 1 is a graph of the luminance decay of a normal backlight provided in a PWM compensation method for an ultra-long-life LED backlight controlled by an MCU according to the present invention;
FIG. 2 is a comparison graph of front and rear PWM compensation current curves of the MCU-controlled ultra-long-life LED backlight PWM compensation method of the present invention;
FIG. 3 is a block diagram of a circuit structure of a backlight control device of the MCU-controlled ultra-long life LED backlight PWM compensation method of the present invention.
Detailed Description
The following detailed description of the present invention will be made with reference to the accompanying drawings.
A PWM compensation method for an LED backlight source with an ultra-long service life controlled by an MCU comprises the following steps:
1) collecting brightness Y0 … Y70 corresponding to X0 … X70 every month on the attenuation curve and storing the brightness Y0 … Y70 into FLASH of the MCU according to the input backlight accumulated time of the display MCU on the basis of the normal backlight brightness attenuation curve of the figure 1;
the brightness corresponding to each month is cut out from the curve, the X axis is the month, the Y axis is the brightness, and n is the month, and the following table is established:
| month of the year | Brightness value | Rate of decay |
| X0 | Y0 | (Y0-0)/Y0 |
| X1 | Y1 | (Y0-Y1)/Y0 |
| Xn | Yn | (Yn-1-Yn)/Y0 |
| X70 | Y70 | (Y69-Y70)/Y0 |
2) With (X)n，Yn) The coordinates of each point are connected by straight lines to form 70 straight line segments, and the brightness change of each month is approximately considered to be linear;
3) decay rate for each day:
An＝(Yn-1-Yn)/(Y0*30)
4) the decay rate is translated into a value corresponding to a 16-bit register:
Bn＝An*65535
5) the MCU of the display calculates the Bn corresponding to each time according to the acquisition time, and the Bn value is unchanged within 30 days;
as shown in fig. 2, the MCU of the display adjusts the current compensation value I of the PWM according to the value of Bn corresponding to each time, I increases proportionally with the increase of Bn; the larger Bn is, the larger current compensation value I of PWM is, so that the compensated backlight source attenuation curve keeps straight.
As shown in fig. 2, the PWM duty cycle is initially set to 50%, increasing from 50% to 100% during 70 months of compensation time, compensating for backlight decay.
The number of lamp wicks of the backlight source adopts an excess design, namely the number of the lamp wicks is 50% more than that of the common backlight source, the backlight source is ensured to work under the condition of lower than rated current, the target brightness is realized, so that a regulating space is reserved for PWM regulation, and when the PWM is regulated to the top limit of 100%, the regulation is stopped and the backlight source enters the natural attenuation of the common backlight source along with the time lapse.
As shown in fig. 3, the backlight control device for implementing the MCU-controlled PWM compensation method for the LED backlight with ultra-long lifetime includes an MCU controller with a real-time clock, an LED driver, and an LED backlight, wherein an output terminal of the MCU controller is connected to the LED driver and connected to the LED backlight through the LED driver. The MCU controller also comprises an ambient light sensor, and the ambient light sensor is connected with the input port of the MCU controller.
The ambient light sensor can sense the intensity of ambient light, quantize the intensity of the ambient light and transmit the quantized ambient light to the MCU controller with the real-time clock through an I2C bus, and adjust the duty ratio of PWM through an internal algorithm program so as to adjust the brightness of the LED backlight source, so that the intelligent adjustment function is achieved, the electric energy can be saved, and the service life of the backlight source is prolonged; the optical film has the functions of anti-reflection and anti-reflection, can effectively compensate reflection and refraction caused by an air layer, and has the optical overall effect equal to that of glue full lamination (optical binding). The MCU controller with the real-time clock has the advantages that the program running (with a battery) is arranged in the MCU controller, the working time of the backlight can be recorded and calculated, the algorithm compensation is arranged in the MCU controller, the algorithm compensation is the inverse compensation of the attenuation curve of the backlight, and the brightness is always kept unchanged. When the PWM output is compensated to the maximum, the process of the overall brightness attenuation of the conventional backlight is finally entered. The LED backlight source is designed in an interference design, the brightness under rated current is higher than a design target value, the purpose is to provide real-time clock control of a debugging space for PWM adjustment, compensation is carried out by utilizing an attenuation curve of the LED backlight source, meanwhile, the brightness of the backlight is automatically adjusted by combining a light induction sensor, and the attenuation of the backlight source is compensated by adopting a program algorithm, so that the purpose of prolonging the service life of the backlight is achieved.
The above embodiments are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the above embodiments. The methods used in the above examples are conventional methods unless otherwise specified.
Claims (5)
1. A PWM compensation method for an LED backlight source with an ultra-long service life controlled by an MCU is characterized by comprising the following steps:
1) collecting brightness Y0 … Y70 corresponding to each month of X0 … X70 on the attenuation curve and storing the brightness Y0 … Y70 into a FLASH of the MCU according to the input backlight accumulated time of the display MCU on the basis of a normal backlight brightness attenuation curve;
the brightness corresponding to each month is cut out from the curve, the X axis is the month, the Y axis is the brightness, and n is the month, and the following table is established:
2) With (X)n，Yn) The coordinates of each point are connected by straight lines to form 70 straight line segments, and the brightness change of each month is approximately considered to be linear;
3) decay rate for each day:
An＝(Yn-1-Yn)/(Y0*30)
4) the decay rate is translated into a value corresponding to a 16-bit register:
Bn＝An*65535
5) the MCU of the display calculates the Bn corresponding to each time according to the acquisition time, and the Bn value is unchanged within 30 days;
the MCU of the display mediates a current compensation value I of the PWM according to a Bn value corresponding to each time, wherein the I is increased in proportion with the increase of the Bn; the larger Bn is, the larger current compensation value I of PWM is, so that the compensated backlight source attenuation curve keeps straight.
2. The MCU controlled ultra-long life LED backlight source PWM compensation method of claim 1, wherein the PWM duty cycle is initially set to 50%, the PWM duty cycle is increased from 50% to 100% within 70 months of compensation time, and the backlight source attenuation is compensated.
3. The MCU-controlled ultra-long-life LED backlight PWM compensation method of claim 1, wherein the number of lampwicks of the backlight is over-designed, that is, the number of lampwicks is 50% more than that of a common backlight, so that the backlight is ensured to work under the lower than rated current, the target brightness is realized, so as to reserve a regulation space for PWM regulation, and when the PWM is regulated to the upper limit of 100%, the regulation is stopped along with the lapse of time, and the PWM enters the natural attenuation of the common backlight.
4. The backlight control device for realizing the MCU controlled ultra-long life LED backlight PWM compensation method of claim 1, comprising an MCU controller with a real-time clock, an LED driver and an LED backlight, wherein the output end of the MCU controller is connected with the LED driver and is connected to the LED backlight through the LED driver.
5. The backlight control device of the PWM compensation method for the ultra-long service life LED backlight controlled by the MCU of claim 4, further comprising an ambient light sensor, wherein the ambient light sensor is connected with the input port of the MCU controller.
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| CN202010198868.2A CN111312180A (en) | 2020-03-19 | 2020-03-19 | PWM compensation method and device for ultra-long service life LED backlight source controlled by MCU |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111883071A (en) * | 2020-08-12 | 2020-11-03 | 深圳创维－Rgb电子有限公司 | Backlight compensation method and device, display equipment and readable storage medium |
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Application publication date: 20200619 |
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