What are the characteristics of LED light sources? What are the types of LED light sources?

Light-emitting diode is a new light source for indoor lighting, referred to as LED. LEDs are commonly used for lighting on video recorders (VCRs) and car dashboards. With a lifespan of up to 100,000 hours, LEDs have no filament, so they do not generate heat or burn out.

Most of the electricity is converted directly into light energy, which effectively reduces the demand for electricity.

LEDs are also small in size and often have a large number of LED light sources concentrated in a larger bubble shell in indoor applications due to their relatively low light output.

The light emitted by LEDs is commonly amber, blue, green, red and cool white, and can also be changed by a combination of different colors, but it requires the cooperation of a lighting control system. LEDs are often used for decorative lighting, or to accentuate changes in the flat design, such as the edges of steps, counters, and light fixtures.

The types of light sources are as follows: 1. Dichromatic phosphor converts white LED light source Dichromatic white LED is made of blue LED chips and YAG phosphors. The generally used blue light chip is the Ingan chip, but the A1Ingan chip can also be used.

The advantages of the blue chip LED with YAG phosphor method are: simple structure, low cost, relatively simple manufacturing process, and YAG phosphor has been used in fluorescent lamps for many years, and the process is relatively mature. The disadvantage is that the efficiency of blue LEDs is not high enough to make the efficiency of LEDs low; There is an energy loss in phosphors themselves; Phosphors and encapsulants age over time, resulting in color temperature drift and shortened lifespan.

2. Trichromatic phosphor converts white LED light source to effectively improve the color rendering of LED under the premise of high efficiency. The most common way to obtain trichromatic white LEDs is to use ultraviolet LEDs to excite a set of trichromatic phosphors that can be effectively irradiated. This type of white LED has high color rendering, the light color and color temperature are adjustable, and the use of high conversion efficiency phosphors can improve the light efficiency of the LED.

However, there are still some shortcomings in the method of ultraviolet LED + trichromatic phosphor, such as the low efficiency of phosphor in converting ultraviolet radiation; Powder mixing is more difficult; Encapsulation materials are easy to age under ultraviolet light irradiation, and have a short lifespan. 3. Multi-chip white LED light source The red, green, and blue LED chips are packaged together, and the light emitted by them is mixed together, and white light can also be obtained. This type of white LED light source is called a multi-chip white LED light source.

Compared with phosphor conversion white LED, the advantage of this type of LED is that it avoids the energy loss of phosphor in the light conversion process, and can obtain higher light efficiency; Moreover, the light intensity of LEDs of different light colors can be controlled separately to achieve the effect of full-color color change, and better color rendering can be obtained through the selection of LED wavelength and intensity. The disadvantages of this method are that the semiconductor materials of LED chips with different light colors are very different, the quantum efficiency is different, the light color is inconsistent with the driving current and temperature, and the decay speed is also different over time. In order to maintain the stability of the color, it is necessary to compensate and adjust the feedback circuit of the three colors of LEDs separately, which makes the circuit too complicated.

In addition, heat dissipation is also a major problem that plagues multi-chip white LED light sources.

The application of LED light source, in terms of projectors, the main significance is to open up a new way for the miniaturization of the fuselage. Due to the small size of the LED light source and the advantages of many display technologies, it is more suitable for the development of small projectors and even originals, so that the user's projection is more "portable" and "free".

LEDs are used for projection lighting, which not only increases the lifespan, but also changes the projector structure, due to the reduced heat dissipation demand, and the shortening of the optical path system, so the heat dissipation and noise have better performance.

At present, the LED light source is mainly used in two kinds of projection products, the integrated small projection element and the pocket small computer, the integrated small projection element is not made into an independent model, which is mainly integrated with micro display devices such as mobile phones, digital cameras, notebook computers, battery power, can project about A4 paper or standard letter paper size of the image, convenient to share the picture with others.

The pocket-sized handheld projector is a complete stand-alone model, small and lightweight, easy to pick up with one hand, easy to carry, can be placed in a file bag, and the future development direction is business applications. It can be used for both AC and DC, the projection screen can be larger than 17 inches, the screen brightness is 15 to 200 lumens, and with the development of technology, the display effect is still improving.

The point light source is a professional lighting LED lamp launched by Sobo Optoelectronics; Built-in microcomputer chip, multiple point light sources can be controlled by combination and programming, which can display various patterns, **, text and animation effects. Sobo Optoelectronics is a leading brand manufacturer of lighting lamps and lanterns in China, providing a full range of LED point light source products and integrated solutions for control systems. The main products are:

Point light source, secondary packaging point light source, full-color point light source, RGBW point light source, DMX512 point light source, grid screen point light source, etc. Sobo point light source is widely used in advertising** and landscape lighting projects. For example:

Large-scale roof dot matrix screens, wall lighting of building facades, outline of buildings, bridges and other buildings, lighting decoration and interior decoration lighting projects of parks, rivers and squares, etc.

The LED light source is a light-emitting diode light source. What are the types of LED light sources? Today, PCHOUSE will answer them for you one by one.

Ring light source: Directly irradiates the top of the test object.

Bar light source: There are three types of illumination effects: direct, oblique and metering.

Linear light source: Spotlight effect, high brightness shortens camera time.

Retro light source: The angle can be adjusted to match the DUT with different characteristics and the working distance.

Backlight: Illuminated from the back of the DUT.

External coaxial reflection light source: The lateral light source can be irradiated parallel to the DUT through the beamsplitter.

Internal coaxial point light source: It needs to be used with a coaxial lens.

Hemispherical ridge cover light source: The light source can be diffused by the diffuser hood to form a uniform irradiation area.

Category: Electronic Digital.

Analysis: Characteristics of LEDs.

1 Significance of limit parameters.

1) Allowable power consumption PM: The maximum value of the product of the forward DC voltage and the current flowing through the two ends of the LED. Above this value, the LED will heat up and be damaged.

2) Maximum forward DC current ifm: the maximum forward DC current allowed to be added. Exceeding this value can damage the diode.

3) Maximum reverse voltage vrm: the maximum reverse voltage allowed to be added and bridged. Above this value, the LED may be damaged by breakdown.

4) Working environment TOPM: The ambient temperature range within which the LED can work normally. Below or above this temperature range, the LED will not work properly and the efficiency will be greatly reduced.

2 Significance of electrical parameters.

1) Spectral distribution and peak wavelength: The light emitted by a certain light-emitting diode is not a single wavelength, and its wavelength is as shown in Figure 2.

As can be seen from the figure, the light emitted by the light-emitting tube has the largest intensity of a certain wavelength 0, which is the peak wavelength.

2) Luminous intensity iv: The luminous intensity of a light-emitting diode usually refers to the luminous intensity in the direction of the normal (for cylindrical light-emitting tubes, its axis). If the radiant intensity in this direction is (1 683) W Sr, it emits light 1 candela (symbol cd).

Due to the small luminous intensity of LEDs, the luminous intensity is often used as a unit of candela (MCD).

3) Spectral half-width δ : It indicates the spectral purity of the luminescent tube. It refers to the separation between the two wavelengths corresponding to the 1 2 peak light intensity in Figure 3.

4) Half value angle 1 2 and angle of view: 1 2 refers to the angle between the direction where the luminous intensity value is half of the axial intensity value and the luminous axial (normal) direction.

2 times the half-value angle is the angle of view (or half-power angle).

Figure 3 shows the angular distribution of the luminous intensity of two different types of LEDs. The coordinates of the perpendicular (normal) ao are the relative luminous intensity (i.e., the ratio of the luminous intensity to the maximum luminous intensity). Obviously, in the direction of the normal line, the South Minions Yuan is full of money?

The greater the angle away from the normal direction, the smaller the relative luminous intensity. From this graph, you can get the half-value angle or angle of view value.

5) Forward working current if: It refers to the forward current of the light-emitting diode when it emits light normally. In actual use, if should be selected as needed.

6) Forward working voltage vf: The working voltage given in the parameter table is obtained under a given forward current. It is generally measured at if=20mA.

The forward operating voltage of the LED is vf. When the outside temperature increases, the VF will decrease.

7) V-I characteristics: The relationship between voltage and current of a light-emitting diode can be shown in Figure 4.

When the forward voltage is less than a certain value (called the threshold), the current is very small and does not emit light. When the voltage exceeds a certain value, the forward current increases rapidly with the voltage and emits light. From the V-i curve, the forward voltage, reverse current and reverse voltage of the light-emitting tube can be obtained.

The reverse leakage current IR of the forward light-emitting tube is less than < 10 A.

Features: 1. Long service life: the semiconductor chip is light, no filament, no glass bulb, not afraid of vibration, not easy to break, and the service life can reach 50,000 hours (the average incandescent lamp life is only 1,000 hours, and the average energy-saving bulb life is only 8,000 hours).

2. High light efficiency: low heat, 90% of electrical energy is converted into visible light (80% of ordinary incandescent lamp energy is converted into heat energy, and only 20% of electrical energy is converted into light energy).

3. Health: Healthy light does not contain ultraviolet and infrared rays, and has no radiation (normal light contains ultraviolet and infrared rays).

4. Vision protection: DC drive, no strobe (ordinary lights are AC drive, which will inevitably produce strobe).

5. Green environmental protection: it does not contain harmful elements such as mercury and antimony, which is conducive to the use of mercury and will not produce electromagnetic interference, (ordinary lamps have elements such as mercury and lead, and the electronic ballasts in energy-saving lamps will cause electromagnetic interference).

6. High safety factor: less voltage and current required, less heat, no potential safety hazards, mines and other dangerous places.

7. High efficiency and energy saving: only a few hours of electricity are needed in 1,000 hours (ordinary 60W incandescent lamps consume 1 kWh in 17 hours, and ordinary 10W energy-saving lamps consume 1 kWh in 100 hours).

8. Market potential: low voltage, DC power supply, battery, solar power supply, lack of electricity, power in remote mountainous areas and outdoor lighting.

LED features:

Pros:1Small size. LEDs are basically very small wafers encapsulated in epoxy resin, so it's very small, very light.

2.Low power consumption. LED power consumption is very low, generally speaking, the working voltage of LED is: The operating current is. That is to say: it consumes no more electricity.

3.Long service life. With the right current and voltage, LEDs can last up to 100,000 hours.

4.High brightness, low heat. LED technology is advancing with each passing day, and its luminous efficiency is making amazing breakthroughs, and it is also constantly decreasing.

5.Environmental protection. LEDs are made of non-toxic materials, unlike fluorescent lamps that contain mercury that can cause pollution, and LEDs can also be reused.

6.Rugged. LEDs are completely encapsulated in epoxy resin, which is stronger than bulbs and fluorescent tubes. There are no loose parts in the lamp body, which makes the LED not easy to damage.

Disadvantages: 1. It is expensive, needs constant current drive, and the heat dissipation treatment is not good, and it is easy to fade.

2. The brightness of the lighting is small, and it is not suitable for large-area lighting.

3. LED lights will also heat up and need to dissipate heat.

4. In the initial stage, LED lighting is mainly used in large-scale landscape lighting, which is not suitable for high-eye environments, and is currently mainly experimental.

5. LED cannot be used as an ordinary light source; Its use is to drive the power supply, optical and thermal conduction coordination.

6. LED small lamp beads will slowly wear out and cannot be replaced after a few years of use, which is easy to cause the entire table lamp to be scrapped.

LED is the abbreviation of English Light Emitting Diode (light-emitting diode), its basic structure is an electroluminescent semiconductor material chip, cured to the bracket with silver glue or white glue, and then connected to the chip and circuit board with silver wire or gold wire, and then sealed with epoxy resin around to protect the internal core, and finally install the shell, so the LED lamp has good seismic performance.

Energy saving, high efficiency, green environmental protection, anti-vibration, convenient light distribution, high color rendering index.

The only power saving, long life, little influence by temperature. However, the power supply provided has radiation, and due to poor heat dissipation problems, the aging rate is fast.