LED candle bulb design points for crystal lighting

Energy photoelectric

Crystal decorative lights (hereinafter referred to as crystal lights) are often indoor lighting and decorative lighting, bringing noble and gorgeous feelings to residential or commercial space. Crystal lamp manufacturers can use a variety of crystal materials to design and manufacture a variety of beautiful crystal lamps; crystal lamps attract attention when light penetrates the crystal, different wavelengths (ie different colors) of light in the crystal The refractive index inside is different, so the crystal seen by the human eye will emit a color like a rainbow, which is the phenomenon of dispersion. Different crystal materials, the number of cutting surfaces and the degree of polishing will make the crystal lamps have different feelings when they are assembled.

Figure 1. Dispersion of crystals

Common crystal lamps use tungsten bulbs with E14 interface, or incandescent bulbs with halogen bulbs, collectively referred to as candle bulbs; a small crystal lamp may require 8-10 candle lights, medium and large crystal lamps It may be necessary to install more than 20-50 candle bulbs. The common traditional candle bulbs are 25W (200-250lm) and 40W (400-480lm). A small crystal light requires 250W (low brightness) to 400W (high brightness), power consumption is very large, if it is a large crystal lamp is more power; and lighting the crystal lamp, because the traditional candle bulb temperature is high, indirectly will cause the indoor temperature to rise, increase the cost of air conditioning electricity. Therefore, many consumers installed the crystal lamp, because it is too power-consuming, it will not always open, but lost the value of the crystal.

The use of LEDs instead of traditional candle lights can effectively solve the problem of power consumption of crystal lamps. With the same brightness, installing LED candle bulbs can save about 80% of electricity. However, the following five characteristics should be noted in the design of LED candle bulbs in order to maintain the original value of the crystal lamp:

1. The Color Rending Index (CRI) is high, and the spectrum in the visible light region is as complete as possible, so that the color of the crystal color is complete.

2. The angle of illumination is large, and the closer to 360 degrees, the better the crystal around the light source.

3. The light distribution needs to be uniform, the light distribution curve is approximately circular, and the difference between light and dark in the illumination angle is small.

4. Exquisite appearance, does not affect the artistic sense of crystal lamps.

5. Light is not flashing, power supply is safe and long life

Figure 2, Tungsten candle light spectrum Figure 3. Tungsten candle light CRI Index

Figure 4, tungsten wire candle light distribution curve

LED color rendering

In terms of improving the color rendering of LEDs, it is possible to achieve the level close to traditional tungsten lamps through various color mixing technologies. At present, LED components made of blue chips with two or three types of phosphor powder are common, and LEDs are lit for a long time. Light decay or color shift is also mild. The color rendering of the LED produced by this process technology has reached 95-97. LED light-emitting elements for LED candle bulbs must have a color rendering requirement of at least 80. If it is greater than 90, it is a higher-grade choice; general color renderings are about 70-75 LED components because the R9 score in CRI is too low. The red spectrum is insufficient, which is not suitable for making LED candle lights.

Figure 5. CRI=70/80/90 LED color rendering compared with traditional candle light

Large angle of illumination

At present, the mainstream specifications of LED candle light on the market are 3W (200lm) and 5W (300-400lm). It is mainly used to replace the traditional candle lamps of 25W and 40W. The brightness and the traditional candle light can already match; but because the LED is plane pointing Sexual light source, single LED illumination angle is about 120 degrees, in order to achieve the purpose of full-circumference, the common LED candle light design will increase the illumination angle by the following ways:

1. Solder the SMD LED (Surface Mounted Device) on a long strip board and insert it into the bulb base in several directions.

2. Remote Phosphor: Mixes the phosphor powder into the plastic and ejects the formed phosphor powder cap onto the LED component that emits blue light.

3. Light guide column technology: use various forms of light guides to scatter LED light in all directions

4. Mist lampshade: use a plastic or sandblasted glass containing a diffused ray filler to make the lampshade

Generally, LED elements that do not have a primary or secondary optical lens are usually Lambertian light type, and the illumination angle is about 120o (the brightness interval is 50 to 100%). This paper proposes a new LED light source design, which uses four light-emitting elements to form an inverted triangular pyramid-shaped illuminant, which can make the illuminant's illuminating angle 360 ​​degrees full-circumferential, and the illuminance obtained at each angle can be uniformized and bright. Dark area differences can be reduced to a minimum, as shown in Figure 7 below.

Figure 6. Illumination angle of LED components without primary or secondary optical lens

Figure 7. Inverted triangular pyramidal illuminator

The illuminant can be composed of various LED elements, wherein an LED component made by COB (Chip On Board) technology is a better choice. Since the COB LED component has a large illuminating area, it is a surface light source instead of a point light source, and can reduce the LED. The high single point brightness causes discomfort in the human eye glare; and the COB surface light source can make the light emitting surface as close to a triangle as possible, reducing the shadow problem caused by the non-light emitting area of ​​the LED element; further, the substrate of the COB element is more The thinner the better, the too thick the substrate may cause the un-lighted area after the combination to be too large, which will have a serious impact on the light distribution curve.

Generally, the LED substrate of COB is usually made of copper and aluminum substrate, and the metal has flexibility. If the thickness of the substrate is too thin, it is easy to cause warpage in the LED packaging process, resulting in unevenness of the bottom of the component and poor heat dissipation of the component. Generally, the thickness of the COB LED component substrate of the copper-aluminum substrate is about 0.8-2.0 mm; if the COB LED component fabricated by using the ceramic substrate can achieve the advantage of thinning the substrate, the thickness of the commonly used ceramic substrate can be 0.3-0.5 mm, without heat The process produces warpage and deformation (the coefficient of thermal expansion approaches 0), and the ceramic is made of insulating material, which is also beneficial for the High Voltage LED design to pass the hitot test.

Even light distribution

In addition to the large enough angle of illumination, uniform light distribution is a key point that LED candle lights are easily overlooked. The LED candle bulb with uniform light distribution is installed on the crystal lamp, so that there is no obvious bright and dark spot. The light distribution curve of the full wide-angle bulb looks like a butterfly with open wings. The bulb has a maximum illumination angle of about 300 degrees due to the base of the tail. Sometimes the bulb needs to be fitted with a taillight cover for modeling. Will affect the integrity of the light distribution curve at the top of a part of the bulb. In short, the light distribution curve looks like a butterfly's wings. The closer it is to a perfect circle, the better the light and dark distribution will be. If it can be within ±10%, there will be no obvious spot. The inverted triangular light source proposed in this paper is made into an LED candle bulb. The light curve at the bottom of the bulb is the same as that of the traditional candle lamp, up to 300o. The top of the bulb has a tail-tail design because the lamp housing has a tail-down design. If you use a non-tailed lampshade, you can achieve a light distribution curve that is very close to the tungsten candle light.

Figure 8. LED candle light distribution curve of inverted triangle light source

Figure 9. LED candle bulb with inverted triangle light source

Beautiful appearance

The exterior part has jumped away from the scope of LED technology, but the appearance is the first important factor for consumers to choose. After all, the LED candle light is installed on the art lamp, and it must take more effort on the appearance. Design and beautify without affecting functionality.

Drive power selection

LED candle bulbs require a built-in light source, heat sink and driver in a limited space, which is a complex design and process technology. Although the current drive is more commonly used with AC-DC linear drives, it is likely that other types of drive power sources may be used in LED candle bulbs in the future, with a focus on not flashing (not perceived on human eyes and digital photography equipment). High efficiency, safety and long-term effectiveness.

The use of LEDs to replace traditional light sources is an inevitable trend. However, when designing and manufacturing LED lamps, it is more important to take into account the feelings of those who use the light source. The ability to create comfortable and harmonious light is a part of LED lighting that needs more attention.

Author: the amount of energy photoelectric Ceraenergy Co., Ltd. R & D Office Chen Zhihui

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