Electrical characteristics of LED light-emitting diodes

LED light-emitting diode

The LED is in the forward working state. When it reaches its luminous voltage value, the LED starts to emit light. When the voltage is continuously increased, the brightness of the LED light increases sharply. If the voltage is increased slightly, the LED may burn out instantly. It can be seen that the LED belongs to a kind. Current devices, it is this characteristic that determines that LEDs must work safely under constant current conditions. This is the main aspect of LED devices that are inconsistent with other light sources in use, and is also a key factor in the safe use of LEDs. The main points.

The figure below shows the relationship between the forward drive current and the output brightness of an LED chip with a power of 1W. It can be seen that the drive current and the lumen output exhibit a significant linear relationship in the range of 350 mA.

However, as the forward current increases, a nonlinear relationship gradually emerges between the two. When the drive current exceeds the linear range, the lumen efficiency per watt will decrease, while in the linear range, the lumens produced per watt will show an upward trend. When the drive current exceeds the linear range, the output power is converted from LED to thermal energy. This thermal energy becomes a burden on the LED driver, increases the complexity of the thermal design, and reduces the LED lifetime. Therefore, for a 1W power LED device, the forward drive current does not exceed 350mA. For the current 5 low-power LED lamp beads, the forward current does not exceed 20mA. For 3W high power LED chips, the forward current should not exceed 700mA.