What Is a Super Bright LED?

Super-bright LED is a new type of LED that is nearly one hundred times brighter than ordinary LED light-emitting diodes. Its outer shell is a colorless transparent resin package. The light-emitting body itself can emit light of a certain wavelength, thereby showing a certain color. Super bright leds are widely used in outdoor billboards, electronic displays, traffic lights, signs, car taillights, LCD backlights, etc.

Super bright LED

Compared with traditional lighting, super bright leds have the following advantages: 1) long life, reliable and durable, extremely low maintenance costs led can be used continuously for 105h, 100 times longer than ordinary incandescent bulbs; 2) high efficiency can now be achieved 201m / w. It is expected to reach 501m / w by 2005], the spectrum of LED) is almost all concentrated in the visible light band, and its luminous efficiency can reach 80% to 90%, and LED can save 1/4 of energy compared to energy-saving lamps; 3) bright colors, light The color is simply a 12-inch red traffic light. For example, it uses a low-efficiency 140w incandescent lamp as the light source. After the 2000lm white light is passed through the red filter, the light loss is 90%, and only 2001m of red light is left. Among the lamps designed by lumileds lighting company using 18 red LED light sources, including the circuit loss, only the power consumption of 14w can produce the same light effect; 4) fast lighting car signal lights is an important application of LED light sources In the field, due to the fast response speed of LEDs (ns level), installing high-level LED brake lights on cars can reduce the occurrence of rear-end collisions. In recent years, high-brightness LEDs have been used in low beams of cars, such as Audi a86.o from German Audi, concept car Yak launched by Fioravanti from Italy at the 2003 Geneva Motor Show, and Ford from the United States recently at the Detroit Auto Show. The model u introduced on the beginning have all used the high-brightness led in the design of the headlight. Although super-bright LED has many advantages, it still has the following disadvantages: 1) Low power The single LED power on the market is generally below 5w, and no more powerful LED has appeared, which is currently difficult for LEDs to become the first choice for lighting. The biggest bottleneck; 2) The temperature needs to be strictly controlled. LED is a semiconductor material and has a pn junction like ordinary diodes. Because the power of the high-brightness diode is relatively large, it is the same as a power semiconductor device. It needs to consider heat dissipation. High will directly affect the life of the led, and will increase the light attenuation of the led, the situation will severely burn the led; 3) High price In addition to low power, the price is the main factor that LED is difficult to become a lighting, although led has been Most people know it and are optimistic about it, but its high price is difficult to be accepted by consumers. At present, the single yellow LED is about o. 6 yuan / pc, green and blue monomer LEDs are around 1.8 yuan / pc, the price of white LED has reached about 2.2 ~ 5.5 yuan / pc; if you combine dozens of individual LEDs, the cost will be greatly increased. For example, if a LED is installed in a lawn light, its unit price is equivalent to several times that of a general lawn light. If the LED is to become the mainstream light source for future lighting, it must be developed in the direction of large lumens. It is possible to break.

hpwa-xh00 is a kind of super bright led from lumileds lighting company. This article uses it as an example to analyze the characteristics of super bright led. Figure 1 shows the relationship between forward voltage drop (vf) and forward current (if). From the curve, it can be known that when the forward voltage exceeds a certain threshold (about 2v), which is generally called the on-voltage, it can be approximately considered , If is proportional to vf. Table 1 is the electrical characteristics of the current super-high-brightness leds. As can be seen from Table 1, the highest if of the currently super bright led can reach 1a, and vf is usually 3 to 4v. Because the light characteristics of LEDs are usually described as a function of current rather than a function of voltage, the relationship between the luminous flux (v) and if is shown in Figure 2. Therefore, using a constant current source drive can better control the brightness. In addition, according to Table 1, it can be seen that the forward voltage drop of LED has a large range (up to more than 1v), and according to the vf-if curve in Figure 1, it can be known that a small change in vf will cause a large if change, thus Causes large changes in brightness. Therefore, driving with a constant voltage source cannot guarantee the consistency of the brightness of the LED, and affects the reliability, life and light attenuation of the LED. Therefore, the super bright LED is usually driven by a constant current source. Figure 3 is the relationship between the temperature and luminous flux (v) of the hpwa-xh00 LED. From Figure 3, it can be seen that the luminous flux is inversely proportional to the temperature. The luminous flux at 85 ° C is half that at 25 ° C, and the light output at 40 ° C is 25 ° C. 1.8 times. The change in temperature also has a certain effect on the wavelength of the lfd. Therefore, good heat dissipation is a guarantee for the LED to maintain a constant brightness.

Super-bright LEDs are used in outdoor billboards, electronic displays, traffic lights, signs and other occasions. They are a combination of a large number of LEDs connected in series and parallel. Due to the large number of LEDs, damage to LEDs will inevitably occur during use, and measures must be taken to improve the reliability of the entire machine. Several issues should be paid attention to when designing the LED application circuit: 1. To extend the life of the LED, the forward current should be derated. When the grid voltage is 220v, it is generally taken about 15ma, and the maximum grid voltage cannot exceed 20ma. 2. Considering the consistency of the forward voltage drop, direct parallel use should be avoided as much as possible. Generally, serial or serial-to-parallel is used. 3. When a small amount of LEDs are damaged, the overall situation cannot be affected. For this reason, the light-emitting tube should be divided into multiple power supplies and measures should be taken to ensure that when the open-circuit damage of the light-emitting tube occurs in each channel, the undamaged light-emitting tube is lit as usual. 4. To ensure the reliability of the power supply circuit, a large number of LEDs cannot be damaged due to the failure of the power supply circuit. Because super-bright LEDs are very expensive, once a problem occurs, they will cause great economic losses. Therefore, various protection measures must be taken to ensure safe operation. When the super-bright LED is used in a traffic signal, a polyswitch self-recovery fuse is used in the power supply circuit to ensure that the current flowing through the LED does not exceed its limit value to prevent the LED from overcurrent damage. For low-voltage power supply, a serial connection method is adopted, and for high-voltage power supply, a serial-to-parallel connection method shown in FIG. 10 is adopted. The voltage stabilizing tube connected in parallel with each LED ensures that when there is open-circuit damage to the LED in one way, the undamaged LED is lit as usual to avoid large-area LED failure caused by a small amount of LED damage. The voltage stabilizing value of the Zener tube should be slightly higher than the forward voltage drop of the LED. In this way, when the LED is not open, there is almost no current flowing through the Zener tube. When the LED is open, the Zener voltage drop is very close. The normal on-state voltage drop of the LED ensures that the current in the branch where it is located is almost unchanged.

1. Static electricity can damage the super bright LED, especially the green, blue and white tubes. Take necessary antistatic measures when handling with your hands, such as wearing an antistatic wrist strap or gloves. 2. The soldering iron must have the necessary anti-static grounding protection measures when welding, especially when welding green, blue and white pipes. 3. As the super bright led has a relatively small viewing angle, generally 15 degrees to 30 degrees, and strong directivity, it must be installed vertically next to the circuit board during soldering assembly, otherwise the brightness will be greatly reduced.