High-power LEDs require thermal management, which greatly increases the cost of LEDs. In the design process, the expensive addition is the heat sink. The heat sink can be made of a variety of metal materials. These materials include both relatively inexpensive aluminum and better conductive but more expensive materials (such as copper and silver). These expensive materials may cause the cost of high-power products to increase by 1 to 10 dollars, and standard LED devices can avoid this cost increase.

      Similarly, the high-power LEDs of lighting manufacturers also need to use MCPCB as another passive cooling technology to control the junction temperature. Because the material of MCPCB has better thermal conductivity, compared to the cheaper FR4PCB used in standard LEDs, these circuit boards have higher heat dissipation efficiency. However, its cost may be as high as 5 times the cost of FR4PCB. Using a cheaper FR4PCB, eliminating the need for expensive heat sinks, and simplifying design considerations, can save up to 60% of the cost.

 When a forward voltage is applied, at the beginning of the forward characteristic, the forward voltage is very small, not enough to overcome the blocking effect of the electric field in the PN junction, and the forward current is almost zero. This section is called the dead zone. This forward voltage that cannot make the diode conduct is called the dead zone voltage. When the forward voltage is greater than the dead zone voltage, the electric field in the PN junction is overcome, the diode is turned on, and the current rises rapidly as the voltage increases. In the current range of normal use, the terminal voltage of the diode remains almost unchanged when it is turned on. This voltage is called the forward voltage of the diode. When the forward voltage across the diode exceeds a certain value, the internal electric field is quickly weakened, the characteristic current increases rapidly, and the diode is forward-conducted. Called the threshold voltage or threshold voltage, the silicon tube is about 0.5V, and the germanium tube is about 0.1V. The forward voltage drop of a silicon diode is about 0.6 to 0.8V, and the forward voltage drop of a germanium diode is about 0.2 to 0.3V.

      When the applied reverse voltage does not exceed a certain range, the current through the diode is the reverse current formed by the drifting movement of minority carriers. Since the reverse current is very small, the diode is in an off state. This reverse current is also called reverse saturation current or leakage current. The reverse saturation current of the diode is greatly affected by temperature. Generally, the reverse current of silicon tube is much smaller than that of germanium tube. The reverse saturation current of low-power silicon tube is on the order of nA, and that of low-power germanium tube is on the order of μA. When the temperature rises, the semiconductor is excited by heat, the number of minority carriers increases, and the reverse saturation current also increases.

      When the applied reverse voltage exceeds a certain value, the reverse current will suddenly increase. This phenomenon is called electrical breakdown. The critical voltage that causes electrical breakdown is called the diode reverse breakdown voltage. The diode loses unidirectional conductivity during electrical breakdown. If the diode is not overheated due to electrical breakdown, the unidirectional conductivity may not be permanently destroyed. After removing the applied voltage, its performance can still be restored, otherwise the diode will be damaged. Therefore, avoid excessively high reverse voltage applied to the diode during use.

      A diode is a two-terminal device with unidirectional conduction. It is divided into electronic diodes and crystal diodes. Electronic diodes are less efficient than crystal diodes due to the heat loss of the filament, so they are rarely seen, and they are more common and commonly used. It is a crystal diode. The unidirectional conductivity of the diode is used in almost all electronic circuits. It plays an important role in many circuits. It is one of the earliest semiconductor devices and its application is also very extensive.

      Diode voltage drop: silicon diode (non-luminous type) forward tube voltage drop is 0.7V, germanium tube forward tube voltage drop is 0.3V, light-emitting diode forward tube voltage drop will vary with different light-emitting colors. There are mainly three colors. The specific voltage drop reference values are as follows: the voltage drop of the red light-emitting diode is 2.0-2.2V, the voltage drop of the yellow light-emitting diode is 1.8-2.0V, and the voltage drop of the green light-emitting diode is 3.0-3.2V, the rated current is about 20mA during normal lighting. The voltage and current of the diode are not linear, so when connecting different diodes in parallel, it is necessary to connect a suitable resistance.