Figure 1 System application scheme for DC drive LED light source
Seoul Semiconductor Co., Ltd., today's Seoul Semiconductor, invented AC LEDs that can be directly driven by AC in 2005, followed by III-N Technology in the US, and 3N technology to develop a gallium nitride substrate based on MOCVD growth technology. Improve lighting and sensor applications, reduce costs and increase productivity. Provides 6-inch production technology for large and small silicon LEDs. 3N invented the single-chip AC light-emitting diode (AC LED), which has established a comprehensive patent portfolio to protect and improve technology, firmly establishing its proprietary position, and is the premier large-scale commercial production of AC LED products. In 2008, the "Industrial Technology Research Institute" of Taiwan Province of China also completed AC LED products that can be industrially produced and have practical application system solutions. It can be directly plugged into AC 110V AC voltage of 60Hz or higher to make AC illumination. Indicator lights, neon lights, and low wattage lights can effectively solve the shortcomings of existing LEDs that cannot be used directly under AC sources, resulting in higher product application costs. Taiwan Industrial Technology Institute's On Chip AC LED (on-chip AC LED) won the 2008 R&D 100 Award, which is known as the American Industry Innovation Oscar. Nowadays, only the United States, South Korea and Taiwan have this technology in the world. The Taiwan Industrial Technology Research Institute has developed the process technology of white, blue and green AC LED, which is not only synchronized with the international market, but also one of the world leaders.
Advantages of AC LED lamps
Compared with incandescent lamps, halogen lamps, fluorescent fluorescent lamps, fluorescent energy-saving lamps, and DC LED lamps, AC LED lamps have more energy-saving, longer life, and more energy-efficient. AC LED illumination eliminates the need for costly AC/DC converters and constant current sources. The performance comparison between AC LED and existing lighting fixtures is shown in Table 1.
Table 1 Comparison of performance between AC LED and existing lighting fixtures
AC LED source ultra-fine grain with a special interlaced matrix arrangement
The major technological breakthrough of AC LED light source is the special arrangement and combination technology of ultra-fine LED die in packaging. At the same time, the diode characteristic of LED PN junction is used as rectification, and semiconductor process plays a very important role. AC LEDs are integrated into a stack of tiny grains through a semiconductor process, using a staggered matrix arrangement process, and adding a bridge circuit to the chip design, so that the AC current can be double-conducted to achieve illumination. The arrangement of the crystal grains is shown in Figure 2. The left picture shows the AC LED die in a staggered matrix arrangement. The right small picture shows the actual AC LED die arrangement photo. The AC LED die is illuminated after the AC is connected. Therefore, only two leads need to be introduced into the AC source to work.
Figure 2 AC LED die arrangement photo and schematic
How AC LED light sources work
The working principle of the AC LED light source is shown in Figure 3. The stack of LED micro-arrays is divided into five strings by an interlaced matrix arrangement. The AC LED die is composed of a rectifier bridge. The two ends of the rectifier bridge are connected to the AC source. The other end is connected with a string of LED dies. The positive half of the alternating current flows along the blue path, the three strings of LED illuminate, the negative half cycle flows along the green path, and three strings of LED dies are illuminated, on the four bridge arms. The LED dies are illuminated in turn, and the LED dies on the bridge arms are simultaneously illuminated. The middle string of LED dies are always illuminated due to sharing. In 60 Hz AC, it will be lit at a frequency of 60 times per second. The DC obtained by the rectifier bridge is pulsating DC, and the LED's illumination is also flashing. The LED has the characteristics of power-off afterglow, and the afterglow can be kept for tens of microseconds. Because the human eye is inert to the flow point memory, the result is The eye's interpretation of the working mode of the LED + light source + afterglow is continuous illumination. LEDs work half the time, half of the time is resting, so heat is reduced by 40% to 20%. Therefore, the life of the AC LED is longer than that of the DC LED.