At present, LED fluorescent lamp market is very active, the manufacturer is divided into three categories: one is the original LED chip factory, homeopathic downstream infiltration, the knowledge of the circuit and LED fluorescent power is not much; second is the original lighting Factory, into a new field, understand some of the circuit knowledge; three are completely new to the factory, they used to do other products or new business, LED power supply some understanding, and some do not understand. LED fluorescent power is the most important LED fluorescent parts, improper selection, LED fluorescent lamp can not play a performance, or even not normal use.
1, Why must constant current:
LED semiconductor characteristics determine its greater impact on the environment. For example, the temperature changes, LED current increases, the voltage increases, LED current will increase. Long over the rated current work, will greatly shorten the LED life. The LED constant current is in the temperature and voltage and other environmental factors change, to ensure that its working current unchanged.
2, LED fluorescent power and light board match:
(Such as I> 350mA, V <40V); either the current is too small, the voltage is too high (such as I <350V), the current is too small, the voltage is too high (such as I < 40mA, V> 180V), the result is a serious heat, low efficiency, or the input voltage range is not enough. In fact, choose a best string and parallel way, plus the voltage and current on each LED is the same, and the power of the effect can play the best performance. The best way is to first communicate with the power supply manufacturers, tailor-made.
3, LED operating current:
General LED rated current of 20 mA, and some factories began to use, the design of 20 mA, in fact, this work under the current heat is very serious, after several comparative tests, designed to 17 mA is ideal The N-way parallel current = 17 * N;
4, LED operating voltage:
General LED recommended working voltage is 3.0-3.5V, tested, most of the work in 3.125V, so by 3.125V formula is more reasonable. M lamp beads in series with the total voltage = 3.125 * M
5, LED light board series and parallel with wide voltage:
To make the LED fluorescent lamp work in a wide range of input voltage range AC85-265V, then the light board LED string parallel way is very important. As the current power supply is generally non-isolated step-down power supply, in the requirements of a wide voltage, the output voltage should not exceed 72V, the input voltage range can reach 85-265V. In other words, the number of series does not exceed 23 strings. The number of parallel not too much, otherwise the working current is too large, serious heat, recommended as 6 and / 8 and / 12 and. The total current does not exceed 240 mA as well. There is also a wide voltage program, that is, first with the L6561 / 7527 voltage elevation to 400V, and then buck, the equivalent of two switching power supply, the cost of double, this program is not high cost, no market.
6, LED series and parallel with the PFC power factor and the relationship between the wide voltage:
Currently there are three kinds of power supply PFC on the market: one is not with PFC dedicated circuit, the PFC is generally around 0.65; one is with a passive PFC circuit, light board well, PFC is generally around 0.92; also With an active active 7527/6561 circuit, the PFC can reach 0.99, but the cost of this solution is twice as expensive as the second option. So the second program more. For passive PFC circuits: also known as paddle-type PFC circuits, the operating voltage range is half the peak of the AC input voltage. If the input is 180V, the peak is 180 * 1.414 = 254V, half of the peak voltage is 127V, minus the step-down pressure difference of 30V, the maximum output is 90V, so the number of LED lamp beads series up to 28 string. Therefore, in order to get a relatively large power factor, the number of lamp beads can not be too much, otherwise, it can not meet the requirements of low voltage.
7, constant current accuracy:
Some of the power supply on the market of poor current accuracy, like the popular PT4107 / HV9910 / BP2808 / SMD802 program and other constant current program, the error of ± 8% or ± 10%, constant current error is too large. General requirements in ± 3% on it. According to 3% of the error, 6-way parallel, the error of each road about ± 0.5%, if it is 12-way parallel, each road error of about ± 0.25%, the accuracy is enough. Accuracy is too high, the cost will be greatly increased. And the LED is concerned, 17 mA and 17.5 mA little effect.
8, isolated / non-isolated:
General isolation power supply such as made 15W, on the LED tube, the transformer size is very large, it is difficult to put in. Especially for the T6 / T8 lamp, almost impossible, so the isolation can only be done in general 15W, more than 15W very little, and the price is very expensive Therefore, the isolation of the price is not high, generally non-isolated accounted for more mainstream, the volume can be done smaller, the minimum can be high 8 mm, in fact, non-isolated security measures done, there is no problem.
9, 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 out; if installed in the lamp will produce a very high temperature, coupled with our LED a luminous efficiency than the The heat will be superimposed to produce higher temperatures, and the life of all electronic parts inside our power supply will be shortened with the rise of temperature, so that efficiency is the most fundamental factor in determining the power life, the efficiency can not be too low, otherwise consumed The heat on the power supply is too big. Generally more than 80% on it, but the efficiency of the matching with the light board connection.
Height is the main factor limiting, generally used for T6 tube / T8 size requirements can not be too high height ≤ 9 mm. T10 tube height ≤15 mm. Length can be long, easier to heat.