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AB20-7 Datasheet(PDF) 4 Page - Lumileds Lighting Company |
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AB20-7 Datasheet(HTML) 4 Page - Lumileds Lighting Company |
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4 / 16 page  2. Determine the SuperFlux LED luminous flux, and forward voltage categories to be used for the signal lamp. Category ranges for SuperFlux LEDs are discussed in AB207. Your local LumiLeds Lighting or Agilent Technologies Field Sales Engineer should be consulted to determine which category ranges should be used for a given model year design. 3. Complete the optical design of the outer lens and secondary optics (i.e., lens or reflectors mounted over each LED emitter). AB205 provides some useful guide lines on the different options available for secondary optic designs. Estimate the percentage of optical flux coupled through the secondary optics and pillow lens and the percentage of optical flux transmitted through the outer lens and any other optical surfaces. For a discus sion of optical flux losses, please see the following section of this application note titled Estimating the Number of SuperFlux LEDs Needed For a Signal Lamp. 4. Complete the thermal design of the LED signal lamp and estimate the overall thermal resistance, Rθja, of the signal lamp. Some useful thermal design guidelines and a thorough discussion of the measurement techniques and typical ranges for Rθja are provided in AB204. 5. Estimate the maximum DC forward current per SuperFlux LED based on the overall thermal resistance, Rθja, of the LED signal lamp, and maximum ambient temperature, using Figure 4 on the SuperFlux LED Data Sheet. 6. Estimate the number of SuperFlux LED emitters needed for the signal lamp. This topic will be covered in the section titled Estimating the Number of SuperFlux LEDs Needed For a Signal Lamp contained in this application note. 7. Pick the circuit topology. Circuit topology refers to the electronic circuit schematic without the electronic component values. The key factors of circuit topology for an LED signal lamp include the following considerations: • Dimensions of the LED array (i.e., number of strings of SuperFlux LEDs and how many seriesconnected SuperFlux LEDs per string). • Interconnection scheme for the LED emitters within the LED array. • Current limiting method (i.e., resistive or active current limiting). • EMC transient protection circuit (if any). • Dimming circuit (such as for a Stop/Tail signal lamp). Please refer to AB203 for a detailed discussion of electrical design considerations. 8. Calculate the nominal values of circuit components [i.e., current limiting resistor(s)] using nominal values for the LED forward voltage. A simple linear model for the forward voltage of SuperFlux LEDs is given in AB203. 9. Estimate the effects of overvoltage and EMC transients on maximum forward current through the SuperFlux LEDs as desired. A discussion of EMC transient protec tion circuits is given in AB203. 10. Calculate expected values of luminous flux at 25°C and over operating temperature as desired. A discussion of how luminous flux varies over temperature is given in AB203 and AB204. SuperFlux LEDs in Automotive Application Brief AB201 (5/04) 4 Figure 1.1 LED Signal Lamp Design Process. |
Similar Part No. - AB20-7 |
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Similar Description - AB20-7 |
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