engineers explain led fluorescent lamp power often appear in several major categories of problems
Currently, LED fluorescent lamp market is very active, manufacturers are mainly divided into three categories: one is the original LED chip factory, homeopathic infiltration to the downstream knowledge of the circuit and LED fluorescent power supply is not much; the second is to do ordinary lighting Factories, to enter a new field, to understand some of the circuit knowledge; three are completely new to the factory, they do other products or new business before, some understanding of the LED power supply, and some do not understand. LED fluorescent lamp power is the most important parts of LED fluorescent lamp, improper selection, LED fluorescent lamp can not play a performance, or even normal use.Why must constant current?LED semiconductor characteristics determine its impact by the environment. For example, the temperature increase, LED current increases, the voltage increases, LED current will increase. Long-term work than the rated current, will greatly shorten the LED life. The LED constant current is the temperature and voltage and other environmental factors change, to ensure that its operating current unchanged.LED fluorescent lamp power and light board match:(Such as I> 350mA, V40V); or the current is too small, the voltage is too high (such as I40mA, V> V40V), the current is too small, the voltage is too small (such as I40mA, V> 180V), the result is a serious fever, low efficiency, or input voltage range is not enough. In fact, choose one of the best string and parallel connection, plus the voltage and current on each LED is the same, while the power supply effect is able to play the best performance. The best way is to communicate with the power supply manufacturers, tailored.LED operating current:General LED rated current 20 mA, and some factories used to start to do, the design of 20 mA, in fact, this current is very serious fever, after repeated comparison test, designed to 17 mA is ideal . Total current in parallel N = 17 * N;LED operating voltage:General LED recommended operating voltage is 3.0-3.5V, the test, most of the work in 3.125V, so by 3.125V calculation formula is reasonable. The total voltage of M lamp beads in series = 3.125 * MLED light board series and parallel and wide voltage:To make the LED fluorescent lamp work in the input voltage range of a wide range of AC85-265V, the light board of the LED string and parallel mode is very important. As the current power supply is generally non-isolated step-down power supply, wide voltage requirements, the output voltage should not exceed 72V, the input voltage range can reach 85-265V. That is, the concatenation number does not exceed 23 strings. Parallel number not too much, otherwise the working current is too large, fever serious, recommended for the 6 and / 8 and / 12 and. The total current does not exceed 240 mA as well. There is a wide voltage program, first with the L6561 / 7527 to raise the voltage to 400V, and then buck, which is equivalent to two switching power supply, cost twice as expensive, this program cost is not high, there is no market. LED series and parallel and PFC power factor and the relationship between wide voltage:PFC on the market today there are three situations: one is not with PFC dedicated circuit, the PFC is generally around 0.65; one is with a passive PFC circuit, light board well prepared, PFC generally around 0.92; also One is to use active active 7527/6561 circuit, PFC can reach 0.99, but the cost of this program than the second program twice as expensive. So more of the second program. For the passive PFC circuit: also called valley-filling PFC circuit, the operating voltage range is the AC input voltage peak half. If the input is 180V, the peak is 180 * 1.414 = 254V, half of the peak voltage is 127V, minus the pressure drop of 30V, the maximum output is 90V, so the number of LED lamp beads in series up to 28 strings. Therefore, in order to get a larger power factor, the number of lamp beads in series can not be too much, otherwise, it can not meet the requirements of low voltage.Constant current accuracy:
On the market some of the power supply constant current accuracy is too poor, the market popular PT4107 / HV9910 / BP2808 / SMD802 program constant current program, the error of ± 8% or ± 10%, constant current error is too large. General requirements in ± 3% on it. 3% of the error, 6 parallel, the error of each channel of about ± 0.5%, if it is 12 parallel, each error of about ± 0.25%, the accuracy is sufficient. Accuracy is too high, the cost will be greatly increased. And the LED is concerned, 17 mA and 17.5 mA has little effect.Isolated / Non-Isolated:General isolation power, such as made of 15W, on the LED tube, the transformer volume is very large, very difficult to put in. Especially for T6 / T8 lamp, almost impossible, so the isolation can only be done in general 15W, more than 15W of the very few, and the price is very expensive. Therefore, the cost of isolation is not high, generally non-isolated more mainstream, the volume can be done smaller, the minimum can be high 8 mm, in fact, non-isolated security measures well, there is no problem.Power efficiency:Output power (output LED voltage * output current) / input power. This parameter is particularly important if the low efficiency means that a large part of the input power into heat emitted; if it is installed in the lamp will produce a very high temperature, coupled with an LED light efficiency than our The heat is distributed, it will stack to produce a higher temperature. The life of all the electronic parts inside our power supply will be shortened with the temperature rise. So efficiency is to determine the most fundamental factor in power life, efficiency can not be too low, otherwise the heat consumed on the power too. Generally more than 80% can be, but the efficiency and light board matching connection law.size:Height is the main limiting factor, generally with T6 tube / T8 size requirements can not be too high ≤ 9 mm. T10 tube height ≤ 15 mm. Length can be long, more easy to heat.