All the LED lamps have this fatal flaw, but so far, no one ever made a good solution. Engaged in LED power supply, or engage in the lighting of LED products, on this issue avoided, pretended not to know, however, the actual production, the problem is endless, of course, there are more pe ople do not know much. totally do not understand how the matter.
Description of the phenomenon: The most common problem is to do a project, hundreds of lamps, damage often for no reason, like a street filled with LED lights, from time to time does not shine, always bad, bad repair. LED lamps, with non-isolated power supply, production, often found in fried bad, the root cause here. Are surge voltage caused by common outdoor lightning, or a large load on the shutdown voltage noise and the like. According to the written argument is a very high voltage, and instantly added to the input supply then transduction to the output from the input supply.
We know that the PWM adjustment of the switching power supply, a number of clock cycles are needed, and if the input voltage transient changes, and time is very short (when the switching power supply did not have time to adjust, when the performance is an instant high-pressure conduction because the load is a string in the 300V high-voltage circuit, 300V, high-pressure moment larger, the high-pressure moment on the added output to the output, especially the step-down circuit for LED fluorescent, isolated power supply would have been better, but many are escape.
Some people say that TVS, Chokes, X-capacitor, in fact, use is not large. Work in the normal current of the LED is very sensitive to voltage changes. We know, in a stable current, the LED work, such as straw hat lights at both ends of the voltage increase to 0.1V, the current at both ends is not increased by a few percent, but may be increased by tens of percent increase of 0.5V nor the tens of percent, but increased by several hundred percent, that is, several times, although several components, or more than 400V, the voltage is still to make the output current fierce increase, then the output is equivalent to a short circuit, or even switch to a direct result of the LED annihilated, the phenomenon of isolated power supply is fried to a bad switch, this is the root cause. This is determined by the LED characteristics.
A lot of constant voltage power supply, like the common constant voltage power supply 12V, with some other load, but the same power used three a bunch, often find a lot of fried bad, because here, because the load characteristics of the LED its easier to damage and damage power.
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