LED is the abbreviation of English "LIGHTEMITTINGDIODE", Chinese abbreviated as light-emitting diode, because it has many advantages such as environmental protection, long life, high photoelectric efficiency (current light efficiency has reached 100LM/W), earthquake resistance, etc., it has been rapidly developed in various industries in recent years. In theory, the service life of LED is about 100,000 hours. However, in the actual application process, some LED lamp designers have insufficient understanding or improper selection of LED driver power or blindly pursue low cost. As a result, the life of LED lamp products is greatly shortened. Poor LED lamps have a lifespan of less than 2,000 hours, and some are even lower. As a result, the advantages of LED lamps are not well developed.
Due to the particularity of LED processing and manufacturing, the current and voltage characteristics of LEDs produced by different manufacturers and even the same manufacturer in the same batch of products have large individual differences. Taking the typical specification of high-power 1W white LED as an example, according to the current and voltage variation rules of LED, a brief description is given. Generally, the forward voltage of 1W white light application is about 3.0-3.6V, that is, when it is labeled as 1W LED. When the current flows through 350 mA, the voltage across it may be 3.1V, or 3.2V or 3.5V may be other values. To ensure the life of 1WLED, the general LED manufacturer recommends that the lamp factory use 350mA current. Drive, when the forward current through the LED reaches 350 mA, the small increase in the forward voltage across the LED will cause the LED forward current to rise sharply, causing the LED temperature to rise linearly, thereby accelerating LED light decay. To shorten the life of the LED and even burn out the LED when it is serious. Due to the particularity of the voltage and current changes of the LED, strict requirements are imposed on the power supply for driving the LED.
Constant current source driving is the best LED driving method. It is driven by constant current source. It does not need to connect current limiting resistors in the output circuit. The current flowing through the LED is not affected by external power supply voltage changes, ambient temperature changes, and discrete LED parameters. The effect is to keep the current constant and give full play to the various excellent characteristics of the LED.
LED constant current power supply is used to supply power to LED lamps. Since the current flowing through the LEDs is automatically detected and controlled during power supply operation, there is no need to worry that excessive current flows through the LEDs at the moment of power-on, and there is no need to worry about short-circuiting of the load. Bad power supply.
Some manufacturers are worried that the choice of electrolytic capacitors on the power driver board will affect the life of the power supply. In fact, it is a misunderstanding. For example, if 105 degrees is used, the high temperature electrolytic capacitor with a life of 8000 hours will be reduced by 10 degrees according to the current life expectancy of electrolytic capacitors. , the life expectancy doubled, then it has a working life of 16,000 hours in a 95 degree environment, a working life of 32,000 hours in a 85 degree environment, and a working life of 64,000 hours in a 75 degree environment. If the actual operating temperature is lower, Then life will be longer! From this point of view, as long as the choice of high-quality electrolytic capacitors has no effect on the life of the drive power!
Another point worthy of attention for LED lighting companies: Since the LED will release a large amount of heat during the working process, the junction temperature of the tube rises rapidly, and the higher the LED power, the greater the heating effect. The increase of the temperature of the LED chip will lead to the change of the performance of the light-emitting device and the attenuation of the electro-optical conversion efficiency. In severe cases, it may even fail. According to the experimental test, the luminous flux decreases by 3% for every 5 degrees Celsius increase of the LED's own temperature, so the LED lamp must pay attention to the LED. The heat dissipation of the light source itself, if possible, increase the heat dissipation area of ​​the LED light source as much as possible, and try to reduce the operating temperature of the LED itself. If conditions permit, it is better to separate the power supply part from the light source part and pursue a small volume blindly. It is not advisable to ignore the operating temperature of the lamps and power supplies.
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