Refers to the use of white LED car headlights. The worldâ€™s first high-tech hybrid Lexus LS600h, released on May 17, 2007, is equipped with white LED headlamps for the first time in the world. Life of up to 10,000 hours, lighting time does not exceed 0.1 seconds. The power consumption is lower than that of HID lamps, which is equivalent to the high-end products of HID lamps. If further improvements are made in the future, the power consumption is expected to be lower.
Increased Brightness, Reduced Power Consumption White LED technology has achieved remarkable progress. There are currently more than fluorescent lamps and HID lamps, and products with luminous efficiency of 100 lm/W are available. Products with a luminous flux of more than 100 lm for a single white LED are also emerging, and applications in the lighting field are accelerating. The Lexus LS600h's automotive headlamp uses five white LEDs with a luminous flux of 400lm to achieve the necessary brightness for the Low Beam. The product was developed by Kosaka Manufacturing.
The auxiliary lamp uses 5 white LEDs
Developed by Kosaka Seisakusho, the headlamps on Toyota's Lexus LS600h are equipped with five white LEDs for the auxiliary lights. One white LED module is used for each white LED lamp.
During the development process, problems such as ensuring brightness, reducing power consumption, and taking measures against heat were encountered. The brightness needs at least the same 20Mcd/m2 as the halogen lamp, and the white LED has only several Mcd/m2. For this purpose, four large-sized blue LED chips of about 1mm square are provided in the package, and each chip can input 2.5W ( The input current is 700mA) and the LED headlamp encapsulates a total of 10W of power. As a result, a brightness of 25 Mcd/m 2 was obtained.
However, providing large power to each chip will reduce the luminous efficiency. Compared with the HID lamp, the headlight of the Lexus LS600h actually has a luminous efficiency of only 40lm/W, which means that the power consumption is greater. For this reason, the use of light by the Kosaka Manufacturing Office has been improved. The specific method is to give different light distribution characteristics to a plurality of white LED lamps equipped to make a light distribution pattern. Compared to when a complicated light distribution pattern is made on one lamp, light loss is reduced.
The Kosaka Factory has also improved the construction of white LED lamps when high-beam light is shining. The high beam needs to illuminate the light distribution pattern below the horizontal line. The original method was to shading and form a pattern, and this time a mirror called a "beam shaper" was used to change the direction of light rays directed above the horizontal line. Through the above measures, more than half of the total luminous flux emitted by the white LED can be provided to the headlight. Compared with HID lamps and halogen lamps that can only extract about 1/3 of the total luminous flux, the efficiency is greatly improved. The same power consumption as when the "Lexus LS460" uses a high-end HID lamp as a headlight is achieved.
There is a problem of heat generation In order to ensure the longevity, Minori Manufacturing Co., Ltd. has also carefully studied the fever measures. The LED headlamp module of this time must be installed in the same space as when using the HID lamp of the LS460. Therefore, it is necessary to take measures against heat in a limited shape. Therefore, the LED chip is first improved so that it can be used even at a bonding temperature of up to 150Â°C.
Second, glass is used as the material for the package on the top of the chip, which suppresses deterioration caused by heat generated when the LED is lit. This type of glass material is harder to deteriorate than the epoxy resin and silicone resin commonly used for packaging materials. Even when the bonding temperature is 115Â°C, the brightness does not decrease even if it is continuously lighted for 8000 hours. The products of other companies will deteriorate by more than 10% after lighting for 5,000 hours.
In addition, in order to dissipate the heat emitted by the white LED, heat sinks and heat pipes are provided on the lamp housing. Many of the LED headlamp prototypes use heat sinks and cooling fans to dissipate heat. However, setting the cooling fan will increase the size of the headlamp module. For this reason, a heat-dissipating tube filled with purified water is used in this time, so that heat can be dissipated without using a cooling fan.