How to increase the reliability of LED fluorescent tube
An important reason for the low lifespan of the LED driving power supply is the insufficient lifespan of the aluminum electrolytic capacitor required for the driving power supply. The main reason is that the ambient temperature inside the LED fluorescent tube is very high during long-term operation, which causes the electrolyte of the aluminum electrolytic capacitor to be quickly consumed. Dry, the life expectancy is greatly shortened, and generally only work for about 5,000 hours. The life of the LED light source is 50,000 hours, so the working life of the aluminum electrolytic capacitor has become the short rib of the life of the LED drive power supply.
In order to solve this problem, some suppliers have invented LED fluorescent tube drive power solutions without aluminum electrolytic capacitors. But not all LED fluorescent tube drive power suppliers approve of this approach. Chen Rong pointed out: "Currently, none of the mass-produced LED fluorescent tube drive power supplies uses a drive solution without electrolytic capacitors. Without it, many tests cannot be passed, such as EMI testing and flicker-free testing."
The LED fluorescent tube driving power solution that uses aluminum electrolytic capacitors can easily pass the above test. What if it is replaced by film capacitors and ceramic capacitors or tantalum capacitors? Film capacitors have to achieve the same capacitance (usually 100-220uF), they will be very large and cost too high. Ceramic capacitors generally have too small capacity. If multiple ceramic capacitors are used to achieve such a large capacity, it will occupy a board area. And the cost is too large. For tantalum capacitors to have such a large capacity, one is too expensive, but the withstand voltage is too low to meet the requirements. Therefore, if you replace it with any other type of capacitor, it is basically either too large or too expensive. If you replace these shortcomings with a capacitor with a smaller capacity, the effect of eliminating ripples will not be so good. Many export products cannot pass the strict certification test indicators. Therefore, the current high-quality LED fluorescent tube driving power supply is still commonly used in aluminum. Electrolytic capacitors.
The supplier’s declared non-electrolytic capacitor LED fluorescent tube drive power solution is likely to just remove the AC input aluminum electrolytic capacitor, and the constant current output aluminum electrolytic capacitor should be difficult to remove or replace.
NXP has introduced a TRIAC dimmable LED fluorescent tube with a built-in drive power. This SSL2102-based drive power solution uses aluminum electrolytic capacitors. When the author asked about the working life of the fluorescent lamp, the working life of the aluminum electrolytic capacitor will definitely affect the life of the entire LED fluorescent tube, but some physical methods can be taken to alleviate this problem, such as placing the aluminum electrolytic capacitor on the PCB close to the lamp. The tail, generally speaking, the temperature of the department closest to the LED light source is the highest, which can reach 100-200℃. The heat-dissipating metal shell department is the second, generally around 100℃, and the lamp tail is the lowest, generally around 70℃, so just pay attention to electrolyzing aluminum. The location of the capacitor is close to the end of the lamp, and its life will not be decayed too much. Our experiments show that its lifespan can reach about 10,000 hours, which is equivalent to 10 years of use. For general household users, it is basically acceptable to change the LED fluorescent tube once every ten years.
From the perspective of the architecture of the LED fluorescent tube drive power supply, Chen Rong said that Japan and the United States will adopt non-isolated solutions as the mainstream because their grid input voltage is only 110V. China and Europe will use isolated solutions as the mainstream. Since their grid input voltage is as high as 220V, the safety of the isolation solution is guaranteed, although the cost may be higher.
