日期：2012年7月25日

Analysis of circuits for LED drives

With the rapid development of LED technology, the annual sales of LED lighting products have sharply increased in recent years. In order to survive from fierce competitions, LED manufacturers from all over the world are striving to improve their products and meanwhile reduce the cost. There is no doubt that improving circuits for LED drives can reduce costs dramatically.

 With the rapid development of LED technology, the annual sales of LED lighting products have sharply increased in recent years.

Circuits for LED drives:

Some LED lighting products need to use several decades or even hundreds of LED chips, such as LED Panels, high power LED Street Lights. Cascading these LEDs require a huge output voltage from LED drivers. If designers connect them all in parallel, LED drivers have to provide a very large output current. Connecting all LED chips in single way (either in series or in parallel) is unreasonable, which will not only restrict the number of drivers but also add to their burden. One more reasonable way is mixing these connections up, half in cascade and half in parallel. This is a simple solution which can evenly distribute voltage and current on each LED chips (if they have quite similar electronic properties). However, this is not an optimal solution, since different applications require different drive circuit designs.

 

Let us think about the following scenario: if one LED chip in a series branch causes short circuit due to its bad quality, no matter of kind of driver circuit this lamp used (neither constant voltage nor constant current), the current running on this series branch will increase. All LED lights chips in this branch will be easily destroyed. In most conditions, this branch will be cut off from the entire circuit. If constant voltage power suppliers are used, the output current will be dropped, with no influence on the rest circuit. But conditions will be different for constant current power suppliers. The current will remain unchanged. When one of branches are failed to work, the output current for the rest branches will be raised. LED chips can be easily destroyed under such circumstance. An effective solution for this situation is connecting LEDs in parallel. Cutting off anyone of them will not having any effect on other components. The entire circuit still can work in a normal condition.


Second Chapter: Several major development trends in the led lighting industry of network marketing

Low-carbon energy-saving lamps, green led lights marketing

Low-carbon economy has become the development direction of all walks of life. The lighting industry, of course popular energy-saving light source, led lighting industry become the new darling of the lighting industry. Shanghai World Expo. Guangzhou Asian Games major venues in the lighting system, highlights the rapid development of the lighting industry. Europe, America, Japan and South Korea launched by countries of  out of incandescent, energy saving lamps, LED lamps, the popularity of programs are being implemented. China is also developing new light in the street lights and interior lighting. The green lighting is changing people’s concept of lighting. “Two sessions” further clarified the low-carbon, the implementation of the national low-carbon subsidies, home lighting industry has ushered in new opportunies for development. Internet marketing also draw support from the green marking trend, in order to play a greater advantage.

Second Chapter: Several major development trends in the led lighting industry of network marketing

Knowledge of marketing, let me tell you quietly

In a network environment, the nature of the market has undergone profound changes, manufacturers and consumers can chat directly through the network for information exchange, commodities trading. The marketing will become more diversified, personalized and though market segmentation. And the consumer’s behavior also have some changes. Consumers will be more extensively involved in the marketing process. Consumer behavior will become more rational, individualized. Liu Dongming Internet marketing mentioned that the led lighting industry is still relatively scarce industry. The public are lacking of LED knowledge, which is a good opportunity for LED industry marketing. In the name of the company to publish LED literacy, timely and properly respond to customer issues, and receive customer e-mail and customer make the right reply, enhance customer understanding of lighting products are to enhance customer retention and brand awareness in order to motivate an effective means of consumption.

Communication to be good by social media

The communication method between Lighting businesses and consumers are very different. The traditional  marketing model may only need a customer service hot line, site service can be carried out through the service network. But the network marketing companies need to understand three points: First,  how the consumers know your brand and products, second, how to let them to buy your products, third, how to make the consumer for the dissemination of positive information. These need to constantly sum up and continue moving forward.

 

 

specifications of led and led street light

In recent years,  a lot of suppliers in Taiwan and the mainland China are planning also a lot of LED demonstration road works case, for the LED lights industry into the power of technology to continue to grow.

specifications of led and led street light

2008 LED street lights 45Lm / W luminous efficiency, and progress to the end of 2009 the factory is now published 80Lm / W luminous efficiency of the lighting standards Regardless of 80lm / W luminous efficiency product quality, whether it can be notice by the end of 2008 the CNS15233 the standard specifications, but also because of the timely support of the Governments of expanding domestic demand, the luminous efficiency of LED lamp products in advanced from all walks of life, fought to enter the LED street light industry, which makes the R & D capabilities, significant progress, I believe in In the near future, the luminous efficiency of LED street lights can progress to completely replace the traditional form of the existing high pressure sodium street light.

All LED lamp products in the design of cooling the processor, generally can be summarized in the aluminum extrusion heat processor, fin-type heat processor and the heat pipe combination of heat processor, in which the aluminum heat processors are mostly processor exposed lighting appearance, this approach has the advantage in the cost of cooling the processor can be relatively cheap, especially mold development costs more competitive, but during the product development of high-wattage, weight is a must pay attention to factors, because the public regulation of the poles on the tolerance of the stress there will be certain restrictions, but also in the high-wattage products generally are using fin type radiator, or the way of the application of heat pipe design thermal treatment plant.

In addition to the heat processor R & D LED lamp structure is another important role is the power supply, because the prevailing LED products for a DC-driven light, and therefore on the manufacturers of the power supply must be customized based the development of a dedicated power supply for various styles of LED lamp products, but also have differences in accordance with national product safety norms for the adjustment of the circuit, to comply with the specification of the safety of the product re-sold throughout the world. We have the experience of the three places the case of LED street lamp project in recent years, LED lights dead lights phenomenon accounted for most of the ratio are caused by the instability of the power supply, power supply stability, will also affect the LED lights on the outdoor use, is it possible to maintain good light decay control within three years.

Secondly, the LED lights in the product development important technical threshold capacity of optical design, good lighting with light features, allows the LED street light evenly distributed in the way of the illuminated surface, Taiwan’s the NS15233 standard specification, only for street lights in a vertical 80-degree angle and 90 degree angle should be less than 30 and 10 of the glare quality requirements. On level 65 ~ 95 degree angle is greater than the specific brightness limit, the rest of the lighting technology, optical design capacity of each product, because some of the engineering case will require the road surface illuminance level limit, then a good optical design can make the light efficiency is slightly worse LED lamp products, the actual level of illuminance of the road surface was good.

Conditions of quality and reliability problems, the LED street lamp Competition to see the rest of the soft lighting to show performance, existing LED lamp products, most of them have adopted the German company OSRAM for street products, bat wings wide-angle two to light distribution design, optical design, each vendor has its own know-how and do not necessarily accept, you can still continue to try to make the street lights road lighting more to improve the efficiency.

spectra led grow light and LED PCB

1 Introduction

With the rising awareness of global environmental protection, energy saving has become the trend. The LED lights industry is one of the industries most attention in recent years. Now, LED products are energy saving, energy-saving, high efficiency, fast response time, long life cycle, and does not contain mercury, with environmental benefits and advantages. General, however, LED high power input power of approximately 20% can be converted into light, and the remaining 80% of electrical energy is converted into heat.

In general, the heat generated by LED light can not export, will make the LED junction surface temperature, thereby affecting the product life cycle, luminous efficiency, stability, and the LED junction surface temperature, luminous efficiency and life relationship, the following diagram for further instructions.

spectra led grow light and LED PCB

2, the LED thermal path

Depending on the packaging technology, the cooling method also is different from the LED variety of thermal path method can approximate Figure III indicate the:

In general, the LED grain (Die) to fight the golden thread, eutectic or flip chip way to link its substrate (Substrate of LED Die) and the formation of an LED chip (chip), then then the LED chip is fixed on the system circuit board (System circuit board). LED possible thermal path for heat directly from the air (shown in three ways 1), or by the LED die substrate to the system board to the atmospheric environment. Heat from the system board to the rate of the atmospheric environment depends on the entire LED lighting system design.

However, at this stage of the cooling of the entire system bottlenecks, mostly dominated in the heat conduction from the LED die to the substrate to the system board. Possible in this part of the cooling channels: one for direct by grains substrate cooling to the system board (Figure 3 ways 2), this thermal path, heat dissipation capability of the LED die and the substrate materials is quite important parameters. On the other hand, the LED generated by the heat will be through the electrode metal wire to the system board, in general, the use of gold thread to do the cooling by the metal wire electrode junction, more slender geometry limited (such as three way 3); Therefore, the eutectic (Eutectic) or flip chip (Flip chip) bonding recently, this design significantly reduce wire length, and a substantial increase in wire cross-sectional area, this way, by the LED electrode the cooling efficiency of the wires to the system board will effectively improve (Figure 3 way and 4 below).

Explained through the thermal path above, learned that the choice of the heat the substrate material and its LED die packages accounted for a very important part in the management of LED street lights heat dissipation, and back outline for LED heat dissipation substrate.

spotlight led flashlight and RGB LED

Do you believe, the color is actually a living: they have the Smart, can make all kinds of space, color affect our mood. However, in most people’s living space, pale or warm light, we are generally accustomed to. The new LED lights change color, that is, LED lamps with dimming, color mechanisms can produce the effect of altered space atmosphere.

spotlight led flashlight and RGB LED

LED lights change color by the capacitor step-down power supply, LED controller and G and R, B tricolor LED array. Its shape and milky white incandescent bulbs, but after the light change color automatically at a certain time interval. Back to the enclosure to issue green, yellow, green, purple, blue, red, white light. When the lights change color of the color was originally the three primary colors LED lights up two LEDs, which can issue a yellow, purple, blue (such as red, blue LED light issued by the purple light); if red, green and blue LED At the same time, when lit, it will produce white light. If the circuit can make the red, green, blue LED lights, a separate light and three-color LED is lit at the same time, issued in seven different colors of light. Outer bulb must be milky white. In order to better blending, non-transparent materials.

LED lights change color for the family birthday party, holiday parties, festive New Year to add a festive atmosphere to the festival: it can also be used for entertainment and advertising lamp, etc.. For example, blue light halo off the 6:00 in the morning, fresh and soft, warm yellow, cute pink, light green, applied to the comfortable scene. Romantic lilac people to think of wonderful memories, home or commercial space in accordance with need to match the color of the atmosphere, you do not need to change the interior decoration or lighting.

However, these lamps have a troublesome shortcomings is to control the color change of the circuit of the cost is high, the life of the drive circuit will be a problem, the industry, there are many kinds of solutions to cope with the expected in 2009 class of applications will be more and more, LED mood lighting market take-off of state in 2010.

The chief components of LED panel lights

LED lights diffusers:

LED diffuser is just a tin plate between LED LGP and the cover. It can evenly guild the light generated by LGP and evenly transmitted them to the cover. It also can be seen as a kind of shield for LGP, blocking or frosting the grid. Normally, diffusers use sheets of acrylic 2.0 or other materials like PC. Acrylic sheets have a higher luminousness but cost much less. In anti-aging aspect, PC materials have a better performance than acrylic sheets. Manufacturers for LED panel lights often take tradeoff between them, finding a suitable balance. Rich and powerful LED giants may even develop their owner LED diffusers, while small and medium sized companies still relies on other LED diffuser factories. After LED diffusers being mounted, most grids on LGP should be covered (totally unseen) and meanwhile designers still need to keep the luminousness as much as 90%. The luminousness of acrylic sheets is around 92%, while that of PC materials is around 88%. Manufacturers selected suitable diffusers materials depending on their specific needs. Currently, most LED manufacturers preferred acrylic sheets.

 LED diffuser is just a tin plate between LED LGP and the cover. It can evenly guild the light generated by LGP and evenly transmitted them to the cover.

Reflector:

Not all light can pass though LGPs and diffusers. Some of them will slip into the backside of LED panel lights. Reflectors can reflect more than 90% of backward light, which can dramatically increase the lighting efficiency.

 

Covers:

Covers for LED panel lights are usually made by aluminum alloy (1060) and also can be considered as part of cooling section. A good cover can effectively reduce the light attenuation and extend the service life of product.

 

LED derivers:

LED lighting products work under DC. They are pretty vulnerable to voltage fluctuations. Even tiny change in voltage may cause violent vibration to LED current. As we all know, LEDs need very rigid working environment – a constant current. High-frequency Derivers are typically developed for LED lighting products, using constant current power suppliers. This module has higher efficiency. PF can reach 0.95. Another module applies constant voltage/current power suppliers, which provide both constant voltage and constant current. This type of drivers have higher stabilities, but cost more than the former, and also have lower efficiency. Constant voltage/current power suppliers are mostly used in export products.