The broken power conversion loss possible HV LED will become the mainstream market?

DC current widely used light emitting diode (DCLED), through to electricity supply, plus the AC to DC rectifier (AC-DC), caused by the extra cost of materials and energy conversion loss, so the industry has developed to a direct drive AC high voltage LED (HV LED), which can greatly improve the LED lighting system. Energy efficiency and luminous efficiency.

In the traditional lighting source, the luminous efficiency is the best fluorescent lamp, the luminous efficiency of the light source is about 65lm/W. For energy loss additional circuit ballast will cause 13~20%, light source through the lamp reflector, the light source efficiency loss is about 30~40%, so in the actual application environment lighting, lighting fluorescent lamp luminous efficiency of about 35lm/W. Although the luminous efficiency of the light source is high, the light loss caused by the additional circuit and lamp structure will greatly reduce the luminous efficiency of the light source.

At present, it has been widely applied in the high power white light LED (DC) (1), and its luminous efficiency can reach 150lm/W. But DC LED is driven by DC power operation, if you want to use in the city, it is bound to the AC to DC rectifier (AC-DC), the energy loss caused by power conversion will be 20~30%, and the driving circuit volume is relatively large, relatively limited lighting design flexibility.

Taiwan high pressure independent R & D (HV) LED technology products, only the external drive circuit simple, can be directly to the electricity of 110 volts (V) /220V drive operation, with 90% high power factor (PF), the 95% advantages of high energy utilization, high luminous efficiency etc.. Now the international development opportunities, domestic manufacturers EPISTAR has been HV LED grain products shipped to foreign LED packaging and application of each plant, home also has developed a number of related manufacturers put HV LED lighting products, lighting for the future mainstream trend.

DC LED HV LED different driving characteristics and design very different

High voltage LED is a semiconductor process, will be a number of microcrystalline particles placed on the same substrate, and then connected in series, and the required process technology is very similar to the traditional LED. However, due to the different driving modes, especially under the alternating current driving conditions, the characteristics and design direction of the high voltage LED are significantly different from the traditional LED.

Figure 1 Schematic diagram of high voltage LED wafer. A plurality of microcrystalline grains which are made on the same substrate are connected in series by a metal wire, and the high voltage driving current is passed through the two wire pad on the end of the chip to enter the micro crystal string. From Figure 2 the microcrystal structure in a side view, you can find the difference of main structure of single particle and traditional LED, only in the different size, the other includes a transparent conductive layer, surface roughness, patterned sapphire substrate can enhance the efficiency of the traditional LED technology, is also suitable for high voltage LED.

Figure 1 high pressure LED structure view

Fig. 2 side view structure of GaN crystallites grown on sapphire substrate

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