Clarify the efficacy of LED light source and the efficacy of LED lamps

LED enters the new market and the application field is expanding. It has been widely used in traffic lights, display screens, landscape lighting and decorative lighting. The market share in the backlight industry has gradually increased. Many companies that used to work on traditional light sources have also launched LED projects. Industrial investment continued to heat up, and the light efficiency record was repeatedly refreshed. Recently, Cree Corporation of the United States announced that its white light power LED light efficiency has once again reached the highest record in the industry. The laboratory parameters have reached 231 lm/W, compared with 100 lm/W of white LEDs announced by Japan Nichia Chemical in June 2006. The effectiveness has more than doubled, and it is believed that the record will be broken as technology advances.

With the concept of light effect being used in LED lamps, many LED lamps have also been added to the torrent of light-effect competitions. Manufacturers are ignoring the differences in product functions between LED light sources and LED lamps, and only use light effects as a benchmark for lamp performance. Simply pursuing high-efficiency indicators, ignoring the characteristics of reliability, color quality and visual comfort that LED lamps should satisfy as a system, the current domestic LED lighting market is pursuing the trend of light effects, municipal engineering and semiconductor lighting pilot demonstration projects. The so-called "high-efficiency LED lamps" used in the invention often fail to achieve the effect of the intended use of energy saving and emission reduction, resulting in a large negative effect.

In view of the current lighting market, this paper describes the difference between LED light source and LED lighting performance. It reveals the reason why the wind of chasing light effects spreads LED lamps from LED light sources. It is emphasized that the luminaire performance of LED luminaire products should be coordinated with other performance requirements, and the luminaire performance should be based on the performance of LED luminaires.

First, the light effect is the classic performance index of the light source products

As far as the light source is concerned, the light effect is a classic indicator. The appearance of each new light source is directly related to the higher light efficiency achieved. Thus, the light effect has become an important indicator of the performance of the LED light source without exception. Of course, other performance indicators of the light source include color rendering index, chromaticity coordinates, color temperature and lifetime.

For lamps using traditional light sources, the light output of the lamps, that is, the ability of the lamps to convert the luminous flux of the lamps, is a classic indicator of the performance of the lamps. Since the performance parameters of LED light sources have not yet reached the standardization level, and the LED light sources used in many lamps are not replaceable, the concept of light effects has also been applied to LED lighting products.

Second, the efficacy of LED lamps is different from the efficacy of LED light sources

When both LED light source and LED luminaire use light efficiency as a performance evaluation index, we first understand the meaning and difference of the two to understand the performance of LED luminaires, and use the correct terminology to evaluate the efficacy of LED light sources and LED luminaires. efficacy.

1, LED light source efficacy and LED lighting efficiency concept

The luminous efficacy of a source is defined as the ratio of the luminous flux emitted by the source to the electrical power it consumes.

The luminaire efficacy definition is the ratio of the initial total luminous flux emitted by the luminaire to the power consumed by the luminaire under the claimed conditions of use, in lm/W.

"Light efficiency" is used to evaluate LED light source. "Efficacy" is used to evaluate LED lamps. LED light source efficacy and LED lamp efficiency both indicate the efficiency of conversion of electrical energy into light energy. It is an indicator to describe the energy-saving characteristics of lighting products, but its connotation is different.

2, different luminous flux

The luminous flux of the light source in the light source of the LED light source refers to the luminous flux emitted by the bare light source (the state not yet installed in the luminaire). The LED light source may be an integrated LED lamp or an integrated LED module, a semi-integrated LED lamp or a semi-integrated LED module or a non-integrated LED lamp or a non-integrated LED module.

The molecular luminous flux in the performance of an LED luminaire refers to the luminous flux emitted by the luminaire after the light source is installed in the luminaire and the power of the required LED control device or LED control device is used. The power supply of the LED control device or the LED control device may be integral, built-in or stand-alone. A luminaire using an LED light source may use a reflector or a diffuser.

The light source loaded into the luminaire may be a single light source or a collection of multiple light sources, but due to the efficiency loss caused by the interaction of thermal energy and electrical energy, and the efficiency of the optical system of the luminaire, the luminous flux of the LED luminaire is not equal to the luminous flux of the LED light source or its simple Accumulate.

The luminous flux in the efficacy of the LED source is different from the measurement of the luminous flux in the efficacy of the luminaire. The former is measured in the pulse state and the latter is measured in the steady state.

The light in the light effect of the LED light source is not directional, as long as the light can be emitted, the northeast and the northwest do not matter. The light in the efficacy of LED luminaires is directional, and light needs to be sent to useful areas.

In the case of using the same LED light source, the luminous flux of the LED luminaire is smaller than the luminous flux of the LED light source.

3, different input power

The denominator in the efficacy of LED light source is not the same as the denominator in the performance of LED lamps. For example, for a non-integrated LED module, the electric power consumed by the LED light source refers only to the power consumed by the LED module, and does not include the power consumed by the LED control device. The electric power consumed in the performance of an LED luminaire refers to the input power of the luminaire, including not only the LED light source, but also the power consumed by the LED control device. The electric power consumed by the LED luminaire is greater than the electric power consumed by the LED light source.

4, the relationship between the efficacy of LED lamps and the light efficiency of LED light source

Due to the different range of luminous flux and electric power involved, the light effect of the LED light source is different from that of the LED light fixture, and the light source light effect is much larger than the light fixture performance. First, because the LED enters the luminaire, the junction temperature increases, the light output decreases (heat loss); the second is because the light source enters the luminaire, and the system loss occurs after using the LED control device or its power supply; the third is that the light passes through the luminaire optical system. The loss after the luminaire efficiency (light loss).

Lamp performance = light source efficiency × (1 - heat loss after entering the lamp) % × (1 - system loss) × (1 - light loss after entering the lamp) %

It can be seen from the above analysis that the light source efficacy is completely different from the luminaire performance and cannot be confused.

Third, the LED light source to carry out the light effect competition, chasing the light effect of the wind from the LED light source to spread the LED lamps

As the LED light efficiency record is constantly being refreshed, there are the following misunderstandings in the ongoing LED light efficacy competition:

1, only light efficiency, no color temperature and color rendering index

It should be noted how much color temperature CCT and how much under the color rendering index Ra, the same light effect, low color temperature is obviously much more difficult than high color temperature.

US Energy Star requirements for color temperature requirements for solid-state lighting indoor luminaires: should be one of the following nominal correlated color temperatures (CCT): 2700K, 3000K, 3500K, 4000K, 5000K (commercial only). ENERGY STAR for solid-state lighting indoor lighting: 5700K, 6500K color temperature is not allowed.

2, only light efficiency, not mentioning lighting comfort

When the wind of the light effect race is scraped from the light source to the luminaire, another phenomenon that blindly pursues the luminaire's performance is saved by the added anti-glare diffuser, ignoring the comfort of the luminaire and not considering the glare control.

3, only light efficiency, not to talk about reliability

In order to blindly pursue the efficacy of the luminaire, the added protective cover of the outdoor luminaire is omitted, so that the parts that should not be exposed are exposed, and the reliability of the LED luminaire is neglected.

Fourth, the LED lamps are marked with the phenomenon of low power and high luminous flux.

Due to the efficiency, we pay attention to the deviation of the input power and the rated luminous flux and the measured value on the 276 LED downlight products. It is found that the phenomenon of low power and high luminous flux is common. This deviation will lead to the product's “light effect”. "Virtual high, pushing up the actual level of LED lighting performance.

1. The situation of low power and high luminous flux

The input power of the LED luminaire is the denominator in the formula for calculating the performance of the product. The lower input power of the same luminous flux indicates that the performance of the product is higher, and reducing the input power of the product can improve the performance of the product. When marking product characteristics, there may be a phenomenon in which the power is as low as possible.

Through the actual measurement, the input power of the LED luminaire can be obtained, and the percentage value of the input power of the luminaire mark is calculated by the formula (1), and the deviation ηP between the measured power and the nominal input power can be obtained.

ηP=(measured power/nominal power)*100% (1)

The meaning of the calculation results:

- ηP = 100%, the measured power is consistent with the nominal value, and the nominal value does not deviate.

- ηP <100%, the measured power is less than the nominal value, and the nominal value is high.

-ηP>100%, the measured power is greater than the nominal value, and the nominal value is low.

A low input power nominal value will make the calculated LED downlight performance too high.

In order to intuitively understand the distribution of the entire sample, we will visually represent the 276 luminaire data measured, as shown in Figure 1.

Figure 1 Scatter plot of measured power and nominal power deviation (%)

As can be seen from Figure 1, the data is mainly distributed in the interval of 90% to 120%. If the deviation limits allowed by the actual power and rated power are specified, the corresponding data of the deviation yield is shown in Table 1.

Table 1 Qualification data for different deviation limits

Analysis Table 1 can be seen:

In Table 1, ηP<100%, that is, 114 samples with measured power less than the nominal power, ηP=100%, that is, the sample with the measured power equal to the nominal power is 2, and ηP>100%, that is, the measured power is greater than There are 160 samples with nominal power and nominal power low, accounting for 57.98% of the total, indicating that there are a large number of low-power and misleading consumers on the market.

If 10% of the power is allowed to be low, that is, the deviation ≤110% calculated according to formula (1) is the deviation limit, 46 lamps will exceed the allowable deviation, and in the 276 group lamps, the failure rate is 16.7%.

2, luminous flux

The luminous flux of LED luminaires is the numerator in the formula of product performance. The higher luminous flux at the same input power indicates that the product has higher efficiency, and increasing the luminous flux of the product can improve the performance of the product. When marking product characteristics, there may be a phenomenon in which the luminous flux is as high as possible.

Through the actual measurement, the luminous flux of the LED lamp can be obtained, and the percentage value of the rated luminous flux of the lamp mark is calculated by the formula (2). We can obtain the deviation ηL between the measured luminous flux and the rated luminous flux, as shown in the formula 2:

ηL=(measured luminous flux/rated luminous flux)*100% (2)

The meaning of the calculation results:

- ηL = 100%, the measured luminous flux is consistent with the nominal value, and the nominal value does not deviate.

- ηL <100%, the measured luminous flux is less than the nominal value, and the nominal value is high.

-ηL>100%, the measured luminous flux is greater than the nominal value, and the nominal value is low.

A nominally high nominal luminous flux will result in a higher performance of the calculated LED luminaire.

In order to intuitively understand the distribution of the entire sample, we will visually represent the 276 luminaire data measured, as shown in Figure 1.

Luminous flux is an important indicator for evaluating the performance of LED downlights. The higher the rated luminous flux, the higher the luminous flux can be obtained at the same power. In order to sell products better, some manufacturers will have high rated luminous flux. In order to visually understand the distribution of the entire sample, Figure 2 gives a scatter plot of the measured luminous flux and the rated luminous flux.

Figure 2 Scatter plot of the ratio of measured luminous flux to nominal luminous flux

It can be seen from Fig. 2 that the data occupies a range from 40% to 140%, which is relatively scattered, indicating that the actual measured luminous flux has a large deviation from the rated luminous flux.

If the actual luminous flux and the allowable deviation of the rated luminous flux are specified, the corresponding data of the deviation yield is shown in Table 2.

Table 2 Qualified data of initial luminous flux at different deviation limits

Analysis Table 2 can be seen:

If a high standard 10% luminous flux is allowed, ie the deviation calculated according to formula (2) is ≥90% as the deviation limit, 91 are within the interval of <90%, exceeding the allowable deviation, in 276 sets of lamps The failure rate was 33.0%.

In Table 2, ηL <100%, that is, 160 samples with measured luminous flux smaller than the nominal luminous flux, accounting for 57.97% of the total. It shows that the actual measured luminous flux of the LED downlight is mostly smaller than the nominal rated luminous flux. At present, the LED downlight on the market has a phenomenon of high rated luminous flux, which will cause misleading to consumers and cause market confusion.

3, the actual performance level of LED downlight

Taking the measured "light performance" of LED downlight as an example, Figure 1 shows the scatter plot of the performance of 276 downlights after actual measurement. As can be seen from Figure 3, most of the data sets are distributed in the interval of 30 to 80, and there are few of them larger than 80.

Figure 3 scatter plot of measured performance

“Efficiency” is the energy-saving evaluation parameter of LED lamps, and Table 3 shows the yields under different performance (LE) limits.

Table 3 The pass rate of measured performance at different limits

As can be seen from Table 3, as the performance limit is increased, the proportion of products that meet the requirements is getting lower and lower. When the performance limit is 60, the required sample reaches 55.43% of the total number of samples; and when the performance limit is 80, the required sample only accounts for 3.26% of the total number of samples. Also marked. 0798 Star Specification

If 80% of the products are qualified, then the current level of performance is only about 40lm/W, which is obviously different from the energy-saving and high-efficiency characteristics claimed by LED lighting products. The actual measurement "performance" of LED downlights is not like The manufacturer advertised as high.

Luminaire performance is one of the performance requirements, it is subject to other performance requirements, such as glare control (comfort of ambient brightness when using), reliability, IP protection level and so on.

We can't neglect the comfort and reliability of lighting because we blindly pursue high "light effects". When considering the other parameters that affect the use, such as the color of light, color rendering, lighting comfort and product reliability, the lamps The performance will be reduced.

Taking the light effect of a non-integrated LED module with a luminous efficacy of 80 lm/W as an example, the heat loss after entering the lamp is 25%, the light loss is 20%, and the system loss is 15%, then the performance of the LED downlight is 80 lm/W× 75% × 80% × 85% = 40.8 lm / W (schematic see Figure 4).

Figure 4 LED lamp performance and LED light source light effect diagram

4. Product performance to ENERGY STAR qualified standards

ENERGY STAR requirements for luminaire performance for residential or commercial solid-state lighting downlights: 42 lm/W. An example of LED downlight performance, protection angle, correlated color temperature (CCT), and color rendering index (CRI) through the US Energy Star is shown in Table 4.

Table 4 US LED Downlight Performance, Protection Angle, CCT and CRI Examples

Fifth, explore the reasons for chasing light effects

The reasons for chasing the wind of light effects from LED light sources to spread LED lamps are as follows:

For a long time, LED downlights and LED street lights have been mistakenly regarded as LED light sources. The technical requirements or specifications formulated are almost the same as those of LED modules. This is mainly caused by the ambiguity of LED luminaires mixed with LED lights.

In general, "light" refers to the light source, and various types of lamps are named after the physical principle of illumination, such as incandescent lamps, high pressure sodium lamps, metal halide lamps, fluorescent lamps, ultraviolet lamps, electroluminescent lamps, tungsten halogens. Lights, etc., the naming and classification of the lights is independent of the location of the application and the type of fixture used. “Lamps” refers to illuminators, which include the accessories and circuits required to illuminate the light source, the optical components that redistribute the light from the source to meet the application requirements, and the assembly of the components required to install, secure, and adjust the luminaire. The classification and naming of lamps depends on the installation method or the location or purpose of the design, such as fixed ceiling lamps, portable table lamps, portable floor lamps, road lighting, tunnel lighting, garden lamps, floodlights. And emergency lighting, and more.

The term "light" is sometimes used in some types of luminaires, perhaps because of customary relationships. Many people refer to "road lighting fixtures" as "street lights" and "ceiling surface mount fixtures" as "ceiling lights". However, the street lamps and ceiling lamps here do not refer to the light source, but to the road lighting fixtures and the ceiling surface mounted lamps. Similarly, “embedded or fixed downlights” are referred to as “downlights”, “movable table lamps” are referred to as “table lamps”, and “movable floor lamps” are referred to as “floor lamps”. , "portable portable lighting" is called "hand lamp".

When everyone is used to picking up an LED light fixture, how much will it be called "light effect"? It seems that "light effect" is the only indicator. The use of "light effect" as the marketing of LED lamps is not comprehensive, its essence is to mistake it as an LED light source, and it is suspected of stealing the concept.

Sixth, the standardization of China's LED lighting products performance indicators is on the right track

Internationally, IEC TC34 has clarified that these LED luminaires are included in the standard category of luminaire products. It should be said that the country is beginning to reverse this orientation. The National Lighting Appliance Standardization Technical Committee recently put the "LED Downlight Performance Requirements" and "LED Downlight Performance Requirements Measurement Methods" into two national standards by the National Lighting Appliance Standardization Technical Committee Lighting Subcommittee, which is a good start and is conducive to In line with the international standards, manufacturers of LED lamps are less likely to take detours.

Simultaneously. The efficacy of LED downlights should be coordinated with other performance requirements.

The performance of LED downlights is only one of many performance requirements. It should be fully developed and should meet all the performance requirements of downlights, including luminosity, glare control, color, structure, thermal test, reliability, low temperature, Electrical performance, classification.

Seven, summary

LED light efficiency is different from LED lamp performance and cannot be confused. LED light efficiency as a light source indicator may be relatively simple, but LED lighting performance is one of many performance requirements, subject to other performance requirements, the performance indicators should be consistent, can not one-sided pursuit of LED lighting performance an indicator, should not be Sacrificing the indicators such as comfort and reliability of the lighting environment.

references

[1] Proceedings of the 4th China-Japan-Korea Lighting Forum, “Evaluation of Key Technical Parameters of LED Downlights”, Yang Wei, Shi Xiaohong

[2] GB/T XXXXX-201X "LED Downlight Performance Requirements"

[3] GB/T XXXXX-201X "Measurement Method of LED Downlight Performance"

[4] "The Similarities and Differences between Lamps and Lamps", Shi Xiaohong

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Edit: Nizi