All LED luminaires have this fatal flaw, and so far, no one has proposed a good solution. All the LED power supply, or the LED finished luminaire, will avoid this problem, pretend to pretend I don't know, but in actual production, this problem is endless. Of course, there are more people who don't understand much. I don't understand what is going on.
Phenomenon description: The most common problem is to do a project, hundreds of lights, often without any reason for damage, the common is like a street street LED street light, sometimes from time to time, often bad, repaired and broken, broken and repaired There are also LED fluorescent lamps , many use non-isolated power supplies, and often found to be blown up during mass production. The root cause is here. Both are caused by surge voltage. There are many reasons for surge voltage. Commonly, it is outdoor lightning strike, or It is a large load turn-on, turn-off, voltage clutter, etc. According to the written method, it is a very high voltage, often reaching thousands of volts, instantaneously applied to the input power terminal, and then transduced from the input power terminal to the output. end.
We know that the PWM adjustment of the switching power supply requires several clock cycles, and if the input voltage changes instantaneously (up to thousands of volts) and the time is very short (tens, hundreds of MS), then the switching power supply does not exist at all. Time to adjust, the performance at this time is the instantaneous high-voltage conduction to the output, especially the current step-down circuit for LED fluorescent lamps, because the load is stringed in the 300V high-voltage circuit, the 300V high voltage instantly becomes larger, this high-voltage moment is added At the output, the isolated power supply will be better, but many will not be able to escape.
Some people say that TVS, chokes, and X capacitors are of little use. Because LEDs operating at normal currents are sensitive to voltage changes. We know that LEDs work at steady currents, such as straw hats, working at 20MA. When the steady voltage is about 3.1V and the voltage applied across it increases by 0.1V, the current at both ends does not increase by a few percent, but may increase by several tens of percent, increase by 0.5V, or increase by one hundred. Dozens of points, but increase by a few hundred percent, that is several times, although the above components can play a role, but the voltage filtered by TVS still has more than 400V, this voltage will still make the output The current increases fiercely. At this time, the output is equivalent to a short circuit. The performance of the non-isolated power supply is to instantaneously blow up the constant current loop, and even the switch tube, which directly causes the LED to be completely destroyed. The phenomenon of isolating the power supply is to destroy the switch tube, resulting in the light not being Bright. This is the root cause. This is determined by the LED characteristics.
Many constant voltage power supplies, like the 12V ordinary constant voltage power supply, often have a low damage rate when carrying some other loads, but the same power supply is used for three strings, several strings and then LEDs. A lot of blown up, the reason is here, because of the load characteristics of the LED, it is more likely to damage itself and damage the power supply.
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