Heat dissipation of high-power LEDs
LED is an optoelectronic device, only 15%~25% of the electrical energy will be converted into light energy during its operation, and the rest of the electrical energy is almost are converted into heat energy, making the temperature of the LED higher. In high-power LEDs, heat dissipation is a major issue that requires special investigation. For example, if the photoelectric conversion efficiency of a 10W white LED is 20% as mentioned above, that is, 8W of electrical energy is converted into heat energy. If no heat dissipation measures are added, the core temperature of the high-power LED will rise rapidly. When its TJ value When the rise exceeds the maximum allowable temperature (usually 150 ℃), the high-power LED will be damaged due to overheating. Therefore, in the design of high-power ED lamps, the most important design work is the heat dissipation design.
In addition, in the heat dissipation calculation of general power devices (such as power supply 1C), as long as the junction temperature is less than the maximum allowable junction temperature (generally 125°C), it is enough. But in high-power LED heat dissipation design, the TJ VALUE requirement is much lower than 125℃. The reason is that TJ has a great influence on the light extraction rate and lifespan of the LED: the higher the TJ, the lower the light extraction rate and the shorter the lifespan of the LED.
Heat dissipation path of high power LED.
High-power LEDs attach great importance to heat dissipation in structural design. Some designers have a large metal heat dissipation pad under the die, which can make the heat of the die spread to the outside through the heat dissipation pad. High-power LEDs are soldered on a printed board (PCB). The bottom surface of the heat dissipation pad is welded with the copper-clad surface of the PCB, and the larger copper-clad layer is used as the heat dissipation surface. In order to improve the heat dissipation efficiency, a double-layer copper-clad PCB is used. This is one of the simplest heat dissipation structures.
Post time: Mar-02-2022