Technologies Archive
Technology
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Dec 30, 1969
Off-Line LED Control Circuit
Resonant mode topologies offer many benefits over traditional buck, boost and flyback solutions. These include soft-switching, higher operating frequencies, higher power density and higher efficiency. Electronic ballast designs for fluorescent lighting applications have already been taking advantage of these benefits for many decades. Much can be learned from electronic ballast circuits and applied to LED driver circuits. This article compares the load requirements for fluorescent lamps and LEDs, explains the functionality of a new dimming electronic ballast control IC, and describes a new resonant mode control circuit for LEDs that uses the new IC. Experimental results of the new circuit are also presented and summarized to show final performance.
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Technology
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Dec 30, 1969
Electrical Considerations of LED Bulbs
Governments all over the world regulated the future use of the inefficient incandescent lamps. For example, the member states of the European Union agreed to a phasing out of incandescent lamps by 2012. The initial European-wide ban applies the first step to “nondirectional” light bulbs. The first types of bulbs to be banned are frosted (non-clear) bulbs and clear bulbs over 100 W, which will be phased out completely by September 2009. The power limit will be moved down to lower wattages, and the efficiency levels raised by the end of 2012.
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Technology
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Dec 30, 1969
High Quality GaN Substrates for Modern LED Technology
It is well known that modern III-nitride based technologies for light emitting diode (LED) production include (as an initial inevitable step) the preparation of GaN templates. Such GaN templates are usually delivered on foreign substrates possessing high lattice mismatch with respect to GaN layers, e.g., sapphire or silicon carbide substrates. The growth of GaN layers on highly mismatched substrates occurs via the formation of 3D islands with their following coalescence [1]. Such growth mode results in an extremely high density of threading dislocations (TDs) up to 1010–1011 cm–2 in the layer interior [1]. These TDs are known as main sources for the deleterious performance of LEDs and other GaN based electronic and optoelectronic devices [2]. Therefore there exists an ultimate necessity in the developing of effective and low-cost recipes for low TD density GaN template manufacturing.
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Technology
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Dec 30, 1969
Microstructured Optics for LED Applications
Optics for use with Light Emitting Diodes are described. Microstructured optics are available and customizable for a wide variety of applications. A few of these will be touched on. A methodology of designing these optics and the photometrics of the typical technology is overviewed.
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