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LED lighting systems are generally designed to step
LED lighting system is designed in accordance with the determined lighting needs, determine the design goals, estimated efficiency of the optical, thermal and electrical systems, the number of calculations required LED, to select the best design, and the final step 6 step.
First, determine lighting needs
LED lighting must meet or exceed the target application's lighting requirements. Prior to the establishment of the design goals must determine lighting requirements. For some applications, the presence of existing lighting standards, the requirements can be directly determined. For other applications, to determine the characteristics of the existing lighting is a good way.
Second, determine the design goals
Well, after determining lighting requirements, you can determine the LED lighting design goals. When defining the lighting requirements, the key design objectives and related light output and power consumption. Be sure to include the target application may also be important for other design goals, including the work environment, bill of materials (BOM) cost and service life.
Third, the estimated efficiency of the optical system, heating system and electrical system
The design process is the most important parameter is the number of LED need to meet design goals. Other design decisions revolve around the number of LED start because a direct impact on the number of LED light output, power and lighting costs. Typical flux LED datasheet view listed, except with the number of design goals lumens, this method is very attractive. However, this method is too idealistic, so the design will not meet the lighting requirements of the application.
LED luminous flux depending on many factors, including the drive current and junction temperature. To accurately calculate the number needed, you must first estimate the efficiency of the optical, thermal and electrical systems.
1, the optical efficiency of the system is estimated by examining the efficacy of the optical system of the optical loss. To estimate the loss of light There are two main sources:
First, secondary optics, secondary optics itself is not part of all the LED optical system, such as a lens or a diffusion sheet on the LED. Associated with the secondary optics loss depending on the specific element used varies. Typical optical efficiency through each of the secondary optical element is 85% to 90% in between.
Second, the loss of light fixtures inside, when the light before reaching the target, hit the hood when the lamp, the lamp produces light loss. Some light is absorbed lamp covers, and some is reflected back to the lamp. Lighting fixture efficiency is determined by the layout, lighting fixtures shell shape and cover material.
2, the relative flux of heat loss LED junction temperature rise with the output decreases. Most LED data sheet lists the typical luminous flux values at 25 ℃, while most LED applications use higher junction temperature. When the junction temperature Tj> 25 ℃, the flux is certainly worse than the LED data sheet value given. LED data sheet has a curve, given the relative light output and the junction temperature of the relationship, such as white XLamp XR-E LED, the curve by selecting a specific relative light output or a specific junction temperature, gives the other property values, 85% relative luminous flux is in this case the effect of the estimated value of the heat lighting.
3, the electrical loss LED drive electronics to the available power source (such as an AC wall outlet or batteries) is converted into a stable current source. This process is the same with all power, efficiency does not reach 100%. Drive electrical losses reduce the overall illumination efficiency, because the input power to the heating of the waste, but not used in the light emission. At the beginning of the design of LED systems should take into account the electrical losses. Typical LED driver system should take into account the electrical losses. A typical LED driver efficiency between 80% to 90%. Cost efficiency is higher than 90% of the drive is much higher. Note that the drive efficiency may vary with the output load.
For indoor applications, drive efficiency of 87% is more appropriate valuation. Outdoor life is very long or drive, efficiency may be lower.
Four, the number of calculations required LED
1, the actual flux flux required for the actual needs of the target flux = / (optical efficiency × thermal efficiency)
2, the operating current operating current is very important in determining the effectiveness and longevity of LED lighting. Increased operating current, the light output of each LED becomes large, thus reducing the required number of LED. But it also brings increased operating current number of disadvantages, such as the effect of reduced life expectancy shortened.
3. After the LED current to determine the number of jobs, you can calculate the flux of each LED. As the LED's heat loss has been taken into account in calculating the actual needs of the flux to, so the number of vendor documentation given LED can be used directly. LED quantity is calculated as follows
= The number of LED's actual desired flux / flux of each LED
Fifth, consider all design and choose the best design possible
After calculating the required number of LED Well, then it should be considered to meet the design goals of all design possibilities. Designers can take advantage of the directional LED light and a lot of available secondary optics to construct the original design.
The so-called secondary optics means in addition to the primary optics LED additional optical elements for shaping the LED light output. General types of secondary optics for reflection (light reflected back from a surface), or refraction (bending of light by refraction material, refractive material, usually glass or plastic). Secondary optics can buy standard parts, ready-made parts or lighting model by ray tracing simulation to design custom.
Six, the last step
After selecting an optimal design, the final work needs to be done: the circuit board layout, prototyping, testing prototypes for the design objectives, finalized design, write observations and suggestions for improvement and so on.
First, determine lighting needs
LED lighting must meet or exceed the target application's lighting requirements. Prior to the establishment of the design goals must determine lighting requirements. For some applications, the presence of existing lighting standards, the requirements can be directly determined. For other applications, to determine the characteristics of the existing lighting is a good way.
Second, determine the design goals
Well, after determining lighting requirements, you can determine the LED lighting design goals. When defining the lighting requirements, the key design objectives and related light output and power consumption. Be sure to include the target application may also be important for other design goals, including the work environment, bill of materials (BOM) cost and service life.
Third, the estimated efficiency of the optical system, heating system and electrical system
The design process is the most important parameter is the number of LED need to meet design goals. Other design decisions revolve around the number of LED start because a direct impact on the number of LED light output, power and lighting costs. Typical flux LED datasheet view listed, except with the number of design goals lumens, this method is very attractive. However, this method is too idealistic, so the design will not meet the lighting requirements of the application.
LED luminous flux depending on many factors, including the drive current and junction temperature. To accurately calculate the number needed, you must first estimate the efficiency of the optical, thermal and electrical systems.
1, the optical efficiency of the system is estimated by examining the efficacy of the optical system of the optical loss. To estimate the loss of light There are two main sources:
First, secondary optics, secondary optics itself is not part of all the LED optical system, such as a lens or a diffusion sheet on the LED. Associated with the secondary optics loss depending on the specific element used varies. Typical optical efficiency through each of the secondary optical element is 85% to 90% in between.
Second, the loss of light fixtures inside, when the light before reaching the target, hit the hood when the lamp, the lamp produces light loss. Some light is absorbed lamp covers, and some is reflected back to the lamp. Lighting fixture efficiency is determined by the layout, lighting fixtures shell shape and cover material.
2, the relative flux of heat loss LED junction temperature rise with the output decreases. Most LED data sheet lists the typical luminous flux values at 25 ℃, while most LED applications use higher junction temperature. When the junction temperature Tj> 25 ℃, the flux is certainly worse than the LED data sheet value given. LED data sheet has a curve, given the relative light output and the junction temperature of the relationship, such as white XLamp XR-E LED, the curve by selecting a specific relative light output or a specific junction temperature, gives the other property values, 85% relative luminous flux is in this case the effect of the estimated value of the heat lighting.
3, the electrical loss LED drive electronics to the available power source (such as an AC wall outlet or batteries) is converted into a stable current source. This process is the same with all power, efficiency does not reach 100%. Drive electrical losses reduce the overall illumination efficiency, because the input power to the heating of the waste, but not used in the light emission. At the beginning of the design of LED systems should take into account the electrical losses. Typical LED driver system should take into account the electrical losses. A typical LED driver efficiency between 80% to 90%. Cost efficiency is higher than 90% of the drive is much higher. Note that the drive efficiency may vary with the output load.
For indoor applications, drive efficiency of 87% is more appropriate valuation. Outdoor life is very long or drive, efficiency may be lower.
Four, the number of calculations required LED
1, the actual flux flux required for the actual needs of the target flux = / (optical efficiency × thermal efficiency)
2, the operating current operating current is very important in determining the effectiveness and longevity of LED lighting. Increased operating current, the light output of each LED becomes large, thus reducing the required number of LED. But it also brings increased operating current number of disadvantages, such as the effect of reduced life expectancy shortened.
3. After the LED current to determine the number of jobs, you can calculate the flux of each LED. As the LED's heat loss has been taken into account in calculating the actual needs of the flux to, so the number of vendor documentation given LED can be used directly. LED quantity is calculated as follows
= The number of LED's actual desired flux / flux of each LED
Fifth, consider all design and choose the best design possible
After calculating the required number of LED Well, then it should be considered to meet the design goals of all design possibilities. Designers can take advantage of the directional LED light and a lot of available secondary optics to construct the original design.
The so-called secondary optics means in addition to the primary optics LED additional optical elements for shaping the LED light output. General types of secondary optics for reflection (light reflected back from a surface), or refraction (bending of light by refraction material, refractive material, usually glass or plastic). Secondary optics can buy standard parts, ready-made parts or lighting model by ray tracing simulation to design custom.
Six, the last step
After selecting an optimal design, the final work needs to be done: the circuit board layout, prototyping, testing prototypes for the design objectives, finalized design, write observations and suggestions for improvement and so on.
