In LED lighting , the trend of replacing traditional fluorescent lamps is becoming more and more clear, so the LED market is very good. Manufacturers are mainly divided into three categories: one is the factory that makes LED chips, and there is not much knowledge about circuit knowledge and power supply ; the second is to do ordinary Lighting factory, know some about circuit knowledge ; the three types are just entering the factory of this industry, the LED power supply is not well understood. The power supply is the most important part. It is not properly selected and cannot perform well or even function properly. Here are some suggestions for your reference.
1. Why must we always have a constant flow:
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 , the power supply and the light board match:
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); or the current is too small, the voltage is too high ( such as I< 40mA, V>180V) , the result is severe heat, 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 ideal to design 17 mA. . The total current of the N parallel connection = 17 * N;
4 , LED working voltage:
The recommended operating voltage of general LED is 3.0-3.5V . After testing, most of the work is 3.125V , so the calculation according to 3.125V is more reasonable. Total voltage of M lamp beads in series = 3.125* M
5 , LED lamp board series and parallel and wide voltage:
In order to operate 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 use L6561/7527 to raise the voltage to 400V , and then step down, which is equivalent to two switching power supplies, which cost twice as much. This solution is not cost-effective and has no market.
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