[Interpretation] Comprehensive efficiency of LED lighting

Generally speaking, the overall efficiency of LED lighting refers to the ratio of the total luminous flux of the lighting fixture to the overall power consumption of the appliance. Under normal circumstances, because the LED lighting will be affected by power loss and temperature rise, the overall luminous efficiency (comprehensive efficiency) of the lighting fixture is 30 to 50% lower than the LED luminous efficiency. Recently, products with an overall efficiency of 80 lm/W or more have become commonplace. Although it is not yet comparable with high-efficiency high-frequency (HF) fluorescent lamps with a total efficiency of approximately 100 lm/W, the back of fluorescent lamps has been seen.

Taking the white LED as an example, the reason why the overall efficiency of the LED lighting apparatus is lower than the luminous efficiency of the LED single body is as follows. First, when white LEDs are used in lighting fixtures, the luminous efficiency will be reduced to a much lower value than that of the white LEDs. This is because the catalog value is mostly the input pulse current, and the luminous efficiency in an ideal state where the temperature of the light emitting portion (active layer) of the LED hardly rises. However, lighting fixtures are often used in a state where a constant current is input to the LEDs. Actually, the temperature of the active layer rises.

Taking this into consideration, the luminous efficiency will be reduced by about 20%. In addition, in the power conversion circuit that converts AC power into DC power and supplies power to the LEDs, power is reduced by about 10 to 15%. Reflectors and lenses are provided in the lighting fixture to direct the light in the desired direction. Nearly 10% of the light is lost during this process. By adding these together, the overall luminous efficiency of the lighting fixture will be reduced by about 40% compared to the catalog value of only the light source.

When white LEDs are used in lighting fixtures, the luminous efficiency is much lower than that of white LEDs. Most of the catalog values ​​are luminous efficiencies measured in an ideal state where almost no increase in temperature occurs in the light emitting portion (active layer) of the LED after the input of the pulse current. However, since lighting fixtures are used in a state where a constant current is input to the LEDs, the temperature of the active layer actually rises. And the light emitted by the light source will not be entirely emitted outside the appliance. The overall luminous efficacy of a lighting fixture is reduced by about 40% compared to the catalog value of the light source.