Various reasons for the LED in use cause the current to increase. At this time, protective measures need to be taken to ensure that the LED will not be damaged because the increased current exceeds a certain time and amplitude. The use of circuit protection devices is the most basic and most economical protection measure. The most commonly used protection component for LED lamp circuit protection is a varistor.
The varistor is used to protect the LED lamp itself. It can be said that no matter what kind of power supply the LED lamp uses, switching power supply, linear power supply, all need this kind of protection. It is used to protect the surge voltage that often occurs on the mains network. The so-called surge voltage is mainly a short-term high-voltage pulse caused by lightning strikes or the start and stop of high-power electrical equipment. Among them, lightning strikes are the main reason. Lightning strikes can be divided into direct lightning strikes and indirect lightning strikes. Direct lightning strikes refer to lightning strikes directly on the power supply network. This possibility is rare, and most large-scale power supply grid systems have their own lightning protection measures. Indirect lightning strikes refer to surges induced by lightning and transmitted on the grid. This kind of surge is very likely to occur, because there are 1,800 thunderstorms all over the world and 600 lightning strikes per second. Each lightning strike will induce a surge voltage on the nearby power grid. The width of the surge pulse is usually only a few microseconds or even shorter, and the amplitude of the pulse may be as high as several thousand volts. Mainly because of its high amplitude, it has the greatest impact on the damage of electronic equipment. Without protection, various electronic devices are easily damaged. Fortunately, the surge protection is very simple, just add an anti-surge varistor, usually it is connected in parallel before the rectifier.
The principle of this varistor is this. There is a non-linear resistor whose resistance is close to an open circuit within a specified threshold range. Once the applied voltage exceeds the threshold, its resistance immediately approaches zero. This makes it easy to absorb this surge. And the varistor is a recoverable device, after the surge is absorbed, it can continue to play a protective role.
In order to ensure continuous and stable light, the operating power of the LED power supply has been increased accordingly, and the price of the varistor that meets the high operating frequency has also increased. This is not conducive to reducing the cost of high-volume civilian products such as LED lights. In addition to the protection characteristics of ordinary varistors, varistors can take into account the needs of power and size at the same time, and the price is not expensive. LED lights The best choice for circuit protection devices.