Analysis of the difference and disadvantage between LED lamps and traditional lamps

At present, LED lamps and traditional light source lamps have many different places in terms of performance, evaluation and design.

1, in the performance evaluation of LED lamps

a) Color space uniformity evaluation to evaluate the difference in viewing angle color of the presence of LED luminaires.

The characteristics of a single illuminant of a conventional light source are different. The LED lamp used in the LED luminaire is composed of a plurality of illuminants and emits light. There is a color difference between the illuminants in the LED luminaire, and the color space uniformity evaluation is needed to evaluate the color of the LED illuminator. Spatial distribution.

b) Use the life to evaluate the durability of LED luminaires.

The measurement and evaluation of the life performance of traditional light sources has been standardized and interchangeable, so the life of traditional light source lamps can be met by replacing the damaged light source and the control device of the lamp designed for 10 years of life, so it is generally not evaluated. The life of traditional light source lamps. The life of an LED luminaire is related to the life of the LED itself, the LED driver and the environment in which the luminaire is supplied to the LED. Moreover, there are many LED lamps in the current form. Except for the LED with the standard lamp head, the other LED lamps are not interchangeable. The life of different LED luminaires can only be determined by the relevant life evaluation. When evaluating the life of an LED luminaire, it is necessary to claim not only the lumen maintenance life (LX) but also the failure rate (FX).

c) The evaluation parameters of the luminous flux ratio that can be utilized by the luminaire are different from those of conventional luminaires. Traditional lighting fixtures are evaluated with luminaire efficiency, while LED luminaires are evaluated for efficacy.

d) Unlike traditional illumination sources, photometric tests can be performed separately. Relative methods can be used for photometric measurement. LED light sources are extremely sensitive to temperature. It is not suitable to separate LED light sources from the lamps. Separate measurement should be used for photometric measurements. The photometric test was performed as a whole.

2, in the design of LED lamps

LED luminaires are clearly distinguished from traditional light source luminaires in terms of optical system design, electrical components, heat dissipation measures, and structural design.

a) Optical system

The optical system in the luminaire is the soul of the luminaire, and the luminaire optical system that meets the specific lighting requirements is designed according to the characteristics of the selected light source. Generally, the optical system of a conventional light source luminaire consists of a light source, a lamp holder, a reflector, and a translucent cover. Since some LED units have a photometric characteristic of 2Ï€ luminescence, the luminosity system of the luminaire is quite different from the conventional illuminating lamp. The specific performance characteristics are as follows:

(1) LED lighting system consists of an optical lens and an LED chip or an LED array consisting of LED module array is sometimes arranged on a flat aluminum plate, the substrate may also be formed on raised or recessed, luminaires, with or without Translucent cover. The luminaire manufacturer can combine multiple LED units or dozens of LED units on the substrate according to lighting requirements. Attention should be paid to control the consistency of the color of the LED unit after the combination, and the color space uniformity of the LED luminaire should be evaluated.

(2) Since the photoelectric characteristics of the LED are very sensitive to the change of the PN junction temperature; the encapsulating resin will rapidly deteriorate under high temperature and strong light irradiation; the long-term optical radiation will gradually reduce the photoconversion rate of the phosphor and lead to the color seat. The target offset.

In the life evaluation of LED lamps, the lumen maintenance rate of LED lamps is usually evaluated under the condition of limiting color shift.

b) electrical accessories

LED driver power is a key element in the performance of LED lamps, and it is also one of the lighting selection or design requirements.

The electrical design of LED luminaires should consider the characteristics and quantity of LEDs used in the luminaire, the location where the luminaires are installed, and the location of the luminaires in the grid to consider electrical safety, constant current drive, immunity and EMI, and select or design a suitable LED drive power supply.

Since the LED is driven by a low voltage constant current source of 2V to 3V, unlike ordinary incandescent bulbs, which can directly connect 220V AC mains, it is necessary to design power and control circuits to drive the LEDs. In addition, the electrical connection of the LED module is also an important part of the electrical system of the LED lamp. Safety should be fully considered, and standard connectors, adequate insulation, and protection against electric shock should be used.

c) heat dissipation measures

Like traditional light source luminaires, LED luminaires are also hot. The heat of LED luminaires comes from the loss of LED photoelectric conversion and the LED drive power. Different from the principle of traditional electric light source illumination (heat radiation of incandescent lamps and gas discharges such as fluorescent lamps), the illumination of LEDs is electroluminescence. Due to the problem of conversion efficiency, most of the energy output is mainly lattice generated by non-radiative recombination. The form of vibration converts thermal energy. The way heat is transferred within the LED is not radiation but conduction. The main goal in the LED lamp heat dissipation design is to effectively conduct the heat of the LED chip effectively and effectively control the LED junction temperature in the LED lamp.

For LED luminaires, in addition to the LED is a heat-generating component, the driver in the LED luminaire is also a heat-generating component. In order to ensure the life with the LED light source, the thermal control of the LED driver is also very important. If the built-in driving power source is used, the luminaire should be based on it. The internal ambient temperature selects the drive labeled with the corresponding tc. When the drive is installed separately, the corresponding tc driver should be selected according to the possible ambient temperature of the installation site.

d) mechanical components and structures

The function of the machine is to determine the position and relationship of the optical system, electrical system and thermal system of the luminaire through structural design, so that the luminaire can be fixed and safely used in the set environment.

The mechanical system of the traditional luminaire consists of the structure of the fixed light source, the reflector, the control device of the lamp, the cable structure of the flexible cable or the flexible wire, the sealing structure, the mechanical protection structure, the fixed structure of the lamp and the adjustment structure of the lamp, etc. It consists of lamp holder or light source connector, lamp holder mounting bracket, cord holder, terminal block, housing, lamp cover and lamp mounting bracket. Due to the characteristics of the LED light source, the LED lamp has several forms such as a package, a module, an LED light engine, an integral LED lamp, and a non-integrated LED lamp, except that the last two forms may have an internal structure similar to that of a conventional light source lamp. LED lights do not have a standard lamp head. In this case, the LED lamp has the following structural features:

There is no lamp holder in the LED lamp, but the electrical connection between the LED lamp and the lamp is completed by the connecting member, and the LED lamp is fixed to the main body of the lamp by other means.

In order to derive the heat generated by the LED chip, the LED lamp has a large number of heat sinks. The volume and weight of the lamp are much larger than those of the conventional light source lamp. The installation structure of the lamp should be considered accordingly to ensure the safety and reliability of the installation. At the same time, the heat sink should be designed to be easy to clean or not easy to accumulate, otherwise the efficiency of the heat sink will be quickly reduced.

When the LED luminaire uses a power cord and the power cord is detachable for maintenance, it is a non-Z type connection. Like a conventional light source that is not a Z-type connection, the LED luminaire should also use a cord holder.

Second, the problem of LED lighting problems LED lighting problems Due to the multiple specialities of LED, we are full of expectations for its bright future, and should not evade its current shortcomings.

1. The luminosity distribution of most street lamps produced in China is unreasonable.

The SSL luminaires published by the US Department of Energy (DOE) meet the ENERGY STAR qualification criteria. We evaluated 200 LED road illuminance data from 2007 to 2009 and found that only 3 LED street lights can meet DOE regulations. The road light distribution and energy efficiency related requirements, the pass rate is only 1.5%. The measured LED street light quality is far from the DOE benchmark requirement and needs to be greatly improved.

2. The insulation withstand voltage problem is common in LED street lamps with anti-surge interference.

The EMS design of LED street lamps only considers the function of anti-surge interference, neglects the requirements for electrical strength in the safety standards of lamps, and should emphasize the adequacy of LED street lamp design input, and consider other functions on the basis of meeting safety requirements.

3. There are some products with very poor quality on the market, which are not bright, short life and poor color.

4. The claimed performance is inaccurate.

5. The information on the product label is insufficient.

6. There are many problems in color quality, such as color rendering.

7. Lighting designers still don't trust SSL products. They said they needed more standards.

8. The cost is still too high, but the government is highly motivated to use SSL products.

In the current situation where LED lighting is not fully mature, we should not blindly reject conventional lighting. On the contrary, we should seek cooperation with conventional lighting, effectively utilize the various technologies and markets accumulated in conventional lighting for many years to develop together. Mutual benefit, after the LED lamps are really mature, I believe that LEDs have their own sky.