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Most of us know lumen can be used as a measure of brightness. It means the total amount of visible lights from an emitting... How to measure efficiency of LED driving light?

Most of us know lumen can be used as a measure of brightness. It means the total amount of visible lights from an emitting source, such as a LED lamp, reflecting the sensitivity of human eyes to lights of different wavelengths. American National Standards Institute established a procedure for testing light output with lumen. However, data received by this means is not very precise. And due to the limitations of production workmanship, some merchandise are labeled with the higher luminous flux than its real brightness. To obtain a competitive lumen, some factories choose to sacrifice other technical advantages, such as increasing lumen at the cost of color changes.

7 inches CREE LED driving lightA red LED light can generate more photons of long wavelength, but the illumination effect will never be satisfactory. What we need most are lights with color temperature from 4300K to 6500K. For example, the color temperature of most Auxbeam LED driving lights is controlled at pure white 6000K, similar to sunshine.

Another way to measure the LED efficacy is called white efficiency, the ratio of optical watt and electrical watt, according to Aurelien David, an American scientist. Here involves the operating principle of LED. LED is composed of semi-conductor chip with p-n junction. After connecting to the electrodes, electron is stimulated with high energy and among the current flows, it releases energy in the form of photon. The input electrical power is converted to lights through the light emitting diode.

However, the conversion to light is not complete because there exists a loss of electrical power, which mostly is used on generating heat. There are several causes leading to heat, the phosphor conversion, pump LED’ imperfect efficiency and optical absorption in the package. The heat has to be dissipated lest it will infringe the function of lamps and even burn. That is why Auxbeam has designed the heat sink of massive fins. There also exists another factor that limits the LED’s white efficiency—the capacity of input electrical power. Many vehicles are configured with an operating voltage of 24V and a small ampere with a relay. Therefore the input power cannot be very huge and so do the optical watts.

fins heat sinkActually, this two metrics are sometimes incompatible. The red or purple lights are of low lumens due to the matter of wavelength, but the white efficiency can be very high if it has been designed with good system of heat sinks, wires, connectors and so on.

The LED market is filled with products of high lumens in accord with customers’ demands. The white efficiency is much more a business engineers concerned about.  In the long run, technical improvement may solve these problems to produce LED driving lights with high white efficiency, high lumens as well as optimal heat generation and dispersion.


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Celia CAO

AuxBeam is one of the leading manufacturers and suppliers of vehicle led lights and vehicle accessories. It focuses on providing cheap but fine products which have won certificates of CE & ECE & ROSH.