Led display screen

The United States department of energy (DOE) "energy star (ENERGYSTAR?) Solid-state lighting (SSL) specification regulations mandatory any power grade all provide power factor correction (IC simplifies PFC). This standard applies to a series of specific products, such as embedded lights, ambry led tube lamp, among them, and the residential applications must be greater than LED drive power factor, and commercial application of 0.7 is required to more than 0.9; However, this standard belong to voluntary standards. Eu IEC61000-3-2 harmonic content is stipulated in the standard power of more than 25 W total harmonic distortion of lighting applications, the maximum equivalent performance total harmonic distortion (THD) < 35%, and power factor (PF) > 0.94. Although not all countries have absolutely compulsory for lighting applications to improve the power factor, but certain application may have the requirements, such as utilities institutions vigorously promote the products with high power factor in public facilities of business application, in addition, utilities institutions when purchased/maintenance streetlights, can also according to their wishes to decide whether to ask have high power factor (usually > 0.95 +). '| d (<. [

IC simplifies PFC technology including the passive and active IC simplifies PFC IC simplifies PFC two kinds. The volume of passive IC simplifies PFC scheme is larger, need to increase additional components to better change current waveform, can achieve about 0.8 or higher power factor. Which, in less than five W to 40 W low power applications, is almost standard choice of flyback type topology structure only need to adopt a passive components and alter, than can be realized circuit 0.7 power factor. Active IC simplifies PFC is usually as a special power conversion section increase to circuits to change the input current waveform. Active IC simplifies PFC usually offer booster, communication 100 to 277 wide input range Vac, IC simplifies PFC output voltage range of dc 450 to 48 Vdc. If properly design IC simplifies PFC section, can provide 91% to 95 percent of the energy efficiency. But increased active IC simplifies PFC, still need special DC - DC conversion to provide current stablized. G r
Four, energy efficiency problem
LED bulb lighting applications with power output energy efficiency need to consider. The United States "energy star solid-state lighting standard stipulated the lighting appliance efficiency, but not level involving the energy-efficiency requirements LED drive alone. As mentioned previously, using AC - DC power LED parlight application can use two sections of distribution topology, so may adopt external AC - DC adapter power supply. While "energy star indeed contains information about the single output external power source codes, its version 2.0 external power supplies norms in effect since November 2008, the required standard work mode, and minimum energy efficiency up to 87% low-voltage work mode minimum energy efficiency of 86%; In this specification, power greater than 100 W IC simplifies PFC. Don't demand
And in using AC - DC power LED spotlight application, to provide higher AC - DC conversion efficiency, it involves the cost, size and performance standards and factors such as a compromise between the energy efficiency. For example, if use higher quality components, the more low conduction impedance (RDSon), can reduce loss and improve energy efficiency; Lower switching frequency general will improve energy efficiency, but will increase system size. So the new topological structures such as resonance, but also provide more energy-efficient increased the complexity of the design and components. If we will design limited within a narrow power and voltage range, can help to optimize efficiency.
Five, drives standards
LED drive itself is in continuous evolution, focuses on further improving energy efficiency, increase function and power density. The United States "energy star" solid-state lighting standard proposed is lighting appliance efficiency, involving level restrictions, including power factor of a specific product requirements. The eu's IEC used 2-13 (5/2006) standard in view of the dc or ac powered LED module requirements including:
?Maximum safety, low voltage (SELV) work output voltage Vrms (more than 25 35.3 Vdc), different fault conditions "appropriate" security work, fault when not smoke or flammable.

In addition, ANSI C82. XXX LED drive criterion still in developed. And in safety, need to follow UL, CSA standard, such as UL1310 (2), UL scale-up 60950, UL1012. LED tube lighting design also related to product life cycle and reliability problems