LED lamp fatal flaws - surge voltage

All LED luminaires have this fatal flaw, and so far no one has proposed a good solution. All those who engage in LED power supply or LED finished lamps have avoided talking about this issue. They don’t know what to pretend. However, in actual mass production, this problem is constantly emerging. Of course, there are more people who don’t understand much. I don't understand what is going on.

The most common problem is to do a project, hundreds of lights, often without any reason for damage, the common is like a street LED street lights, 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. All of them are caused by surge voltage. There are many reasons for surge voltage. The common ones are outdoor lightning strikes, or large load turn-on, turn-off, voltage clutter and the like. According to the written method, it is a very high voltage, often reaching thousands of volts, which is applied to the input power terminal instantaneously, and then transferred from the input power terminal to the output terminal.

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 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 in the 300V high-voltage circuit, the 300V high voltage instantly becomes larger, this high voltage instant is added at the output. Isolated power supplies will be better, but many are hard to escape.

Some people say that TVS, chokes, and X capacitors are actually not very useful. Because LEDs operating at normal currents are sensitive to voltage changes. We know that when the LED is working at a steady current, such as a straw hat lamp, when it is working at 20MA, the stable voltage is about 3.1V. When the voltage applied to both ends is increased by 0.1V, the current at both ends is not increased by a few percent. But it may increase by tens of percent, increase by 0.5V, or increase by tens of percent, but increase by a few hundred percent, that is several times, although the above components can play a role, However, the voltage filtered by TVS is still more than 400V. This voltage will still increase the current at the output terminal. 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. Directly leading to the LEDs completely annihilated, the phenomenon of isolating the power supply is to destroy the switch tube, causing the light to not light, this is the root cause. This is determined by the characteristics of the LED.

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.