The heat dissipation problem of high-power LED lamp beads is a key issue that designers must consider. The light decay of high-power LED lamp beads is related to the working time and current of high-power LED lamp beads and the temperature of high-power LED lamp beads when they work. The working life of high-power LED lamp beads can reach at least 50,000 hours under correct working conditions. Generally, it is very easy to reach 100,000 or even hundreds of thousands. However, once the ambient temperature is too high and the working current is too large, it will cause large The lifespan of the power led lamp bead drops sharply, and even causes permanent damage. Generally, low-power LED lamp beads do not need to consider the problem of heat dissipation, but at present, medium-power LED lamp beads with a working current of 60-150mA have appeared. At this time, designers are required to consider the heat dissipation of LED lamp beads during normal operation. The problem is, fortunately, a white LED lamp with an outer diameter of 8mm and a working current of 150mA has relatively thick pins, which can basically be used to dissipate heat. LEDs with 3W, 5W or even more than 10W must be added with heat sinks to be regarded as a normal working environment.

Most electronics hobbyists know that after the PN junction semiconductor device is conducting, the junction voltage VF decreases with the rise of the ambient temperature, that is: -2mv/℃, which is called the negative temperature effect of the PN junction, and this characteristic can be used to make a temperature sensor , but this feature is a fatal flaw in luminous applications, which directly affects its luminous efficiency. Luminous brightness, luminous chromaticity. For example, when the room temperature is 25°C, the best working current of the high-power LED lamp bead is 20mA. When the ambient temperature rises to 85°C, the junction voltage VF drops, and the working current increases sharply to 35-37mA. In the experiment, the temperature drops to - At 40°C, the junction voltage VF rises, and the optimal working current will decrease from 20mA to 8-10mA. The luminous brightness will also decrease with the decrease of the current, which cannot reach the illumination required by the place.