Currently, the LED fluorescent lamp market is very active, and manufacturers are mainly divided into three categories:
First, the factory that originally made LED chips , infiltrated into the downstream, and did not know much about circuit knowledge and LED fluorescent lamp power;
Second, the factory that used to be ordinary lighting entered a new field and learned some about circuit knowledge;
Third, the completely new factory, they used to do other products or new ventures, have some understanding of LED power, and some do not understand.
The LED fluorescent lamp power supply is the most important component of the LED fluorescent lamp. If the LED fluorescent lamp is not properly selected, the LED fluorescent lamp cannot perform its performance or even function normally. In the process of cooperation with customers, I found some misunderstandings, and here are some suggestions for customers to choose.
1. Why must constant current: The characteristics of LED semiconductors determine that they are greatly affected by the environment. For example, if the temperature changes, the current of the LED increases, and the voltage increases, and the current of the LED also increases. Long-term operation beyond the rated current will greatly shorten the service life of the LED. The LED constant current is to ensure that its operating current does not change when environmental factors such as temperature and voltage change.
2. LED fluorescent lamp power supply and light board matching: Some customers first design the light board, then find the power supply, and find that it is difficult to have a suitable power supply, or the current is too large, the voltage is too small (such as I>350mA, V<40V); The current is too small and the voltage is too high (such as I<40mA, V>180V), resulting in severe heat generation, low efficiency, or insufficient input voltage range. In fact, choosing the best string parallel connection method, the voltage and current applied to each LED is the same, and the power supply effect can achieve the best performance. The best way is to communicate with the power supply manufacturer and tailor it.
3. LED working current: The rated working current of the general LED is 20 mA. Some factories use it at the beginning, and design 20 mA. In fact, the working heat at this current is very serious. After many comparison tests, it is designed into 16-18 mA is ideal. The total current of the N parallel connection = 17 * N;
4. LED working voltage: The recommended working voltage of general LED is 3.0-3.5V. After testing, most of the work is 3.125V, so it is reasonable to calculate according to 3.125V. Total voltage of M lamp beads in series = 3.125* M
5. Series and Parallel Connection of LED Light Board and Wide Voltage: In order to make the LED fluorescent lamp work in the wide range of input voltage range AC85-265V, the LED series and parallel connection of the light board is very important. Since the current power supply is generally a non-isolated buck power supply, when a wide voltage is required, the output voltage should not exceed 72V, and the input voltage range can reach 85-265V. In other words, the number of series is no more than 23 strings. Do not use too many parallels, otherwise the operating current is too large and the heat is severe. It is recommended to be 6 and /8 and /12. The total current does not exceed 240 mA.
There is also a wide voltage scheme, which is to first raise the voltage to 400V with L6561/7527, and then step down, which is equivalent to two switching power supplies, which is twice as expensive. This solution is not cost-effective and has no market.
6. The relationship between series and parallel connection of LED and PFC power factor and wide voltage; currently there are three kinds of power supply PFC on the market: one is without PFC dedicated circuit, its PFC is generally around 0.65; one is with passive PFC circuit The PFC is generally around 0.92. It is also made of an active active 7527/6561 circuit. The PFC can reach 0.99, but the cost of this solution is twice that of the second solution. . So the second option is more.
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