Explain the comprehensive efficiency of LED lighting

LED lighting The overall efficiency refers to the ratio of the total luminous flux of the lighting fixture to the overall power consumption of the fixture. Generally, since LED lighting is affected by power loss and temperature rise, the overall luminous efficiency (overall efficiency) of the lighting fixture is 30-50% lower than the luminous efficiency of the LED alone.

Taking white LED as an example, the reasons why the overall efficiency of LED lighting equipment is lower than the luminous efficiency of a single LED are as follows. First, when white LEDs are used in lighting equipment, the luminous efficiency often drops below the catalog value of white LEDs. This is because the catalog values ​​are often luminous efficiencies under ideal conditions where a pulsed current is input and the temperature of the light-emitting part (active layer) of the LED hardly rises. However, lighting equipment is often used in a state where a fixed current is input to the LED, and in reality the temperature of the active layer rises. Taking this into account, the luminous efficiency is reduced by about 20%. In addition, the power conversion circuit that converts AC power into DC power and supplies power to the LED reduces power by about 10 to 15%. Reflectors and lenses are installed in lighting equipment to direct light in the desired direction, and nearly 10% of the light is lost in this process. Adding these together, the overall luminous efficiency of the lighting equipment is reduced by about 40% compared to the catalog value of the light source alone.

When white LEDs are used in lighting fixtures, the luminous efficiency is much lower than the catalog value of white LEDs. Most catalog values ​​are measured under ideal conditions where the light-emitting part (active layer) of the LED hardly experiences a temperature rise after a pulsed current is input. However, lighting fixtures are used with a fixed current input to the LED, so the temperature of the active layer actually rises. In addition, not all the light emitted by the light source is emitted outside the fixture. The overall luminous efficiency of the lighting fixture is about 40% lower than the catalog value of the light source.

However, recently, products with an overall efficiency of 80lm/W or above have become common. Although they cannot yet compete with high-efficiency high-frequency (HF) fluorescent lamps with an overall efficiency of nearly 100lm/W, the fluorescent lamps are already gaining ground.