Why do LED bulbs with the same wattage have different brightness?

The reasons for this phenomenon are generally as follows:

①The efficiency of the light source is different

LED lamps consume electricity and emit light. This involves the problem of conversion efficiency. The expression of light efficiency index is lm/w. This refers to how many lumens of luminous flux can be converted into watts of electrical power. LEDs were just born with a light effect of only a few tenths of a lumens per watt. Now good quality LED lamp beads can reach 180lm/w, a difference of several thousand times. Until now, the luminous efficacy of LED has been continuously refreshed every year. Therefore, it is not surprising that light bulbs of the same specification assembled with lamp beads of different periods or different manufacturers have different brightness.

②The power efficiency is different

LED lamp beads are nonlinear components with negative temperature and are extremely sensitive to changes in temperature and voltage. Therefore, neither the AC nor the DC power supply can directly supply power to the LED, but must be driven by a constant current to work. The efficiency of different quality constant current drives varies greatly, ranging from 50% to 90%. Therefore, even if a light source with high luminous efficiency is selected, such as the low efficiency of constant current drive, it will also lead to insufficient brightness.

③The power is marked according to different

At present, the power labeling in the LED lighting market is rather chaotic. Some are based on the actual power consumption of the whole lamp, while others are based on the power of the lamp beads. Since the efficiency of the power supply cannot be 100%, the LED bulbs with the same power may be marked with different powers by different manufacturers.

④The area of ​​the light-emitting part is different

Two bulbs of different shapes with the same wattage can sometimes appear to be very different in brightness. For example, a small light bulb will appear brighter than a large light bulb. Bulbs look brighter than tubes, etc.

This is because the area of ​​the light-emitting portion is different. Since the same light energy is distributed in different areas, the luminous intensity per unit area is inversely proportional to the area. Therefore, although the brightness of the light source itself is different due to the different light-emitting area, the lighting effect is still very close.

⑤The color temperature is different

Color temperature is an important indicator of lighting fixtures. What is color temperature? In layman's terms, it is like a heated iron block (actually an idealized black body) that starts out red, then gradually turns yellow, white and finally blue as the temperature increases. Therefore, we call the light with a reddish color as a low color temperature and a bluish light as a high color temperature.

This makes it possible to express "hue" in terms of temperature. The unit of color temperature is "K", which is 273.15 different from our commonly used "℃". That is: 0°C is equivalent to 273.15K.

The human eye perceives light with different color temperatures differently. Under the premise of the same luminous flux, the high color temperature light will appear brighter.