At present, the LED fluorescent lamp market is very active, and the manufacturer is mainly divided into three categories: one is the factory that is the factory that is the LED chip, the situation is penetrating downstream, and there is not much to understand the circuit knowledge and LED fluorescent lamp; the second category is originally a normal lighting Factory, enter a new field, understand circuit knowledge; three categories are completely new factory, they used to do other products or new entrepreneurship, understanding the LED power, some don't know. LED fluorescent lamps are the most important components in the LED fluorescent lamp, and the LED fluorescent lamps cannot be played, and they cannot be used normally.
1. Why do you have to constant:
The characteristics of the LED semiconductor determine that it is affected by the environment. For example, the temperature changes, the current of the LED increases, the voltage increases, and the current of the LED will increase. Long-term exceeding the rated current work, it will greatly reduce the life of LEDs. The LED constant current is when the temperature and voltage is changed, and its operating current is unchanged.
2, LED fluorescent lamp power and light board match:
Some customers first design the light board, then find the power supply, find it difficult to have a suitable power supply, either current, too small (such as I "350mA, v" 40V); either current is too small, the voltage is too high (such as I " 40mA, v "180V), resulting in severe heating, low efficiency, or insufficient input voltage range. In fact, choose a stringent string and plug-in, the voltage of the voltage on each LED is the same, and the effect of the power supply can play the best performance. The best way is to communicate with power vendors, tailor.
3, LED working current:
General LED's rated working current 20 mA, some factory uses the same, design 20 mA, in fact, the work is very serious under this current, and it is more conceived by multiple comparison experiments. . The total current of the N road = 17 * n;
4, LED working voltage:
General LED recommended operating voltage is 3.0-3.5V, tested, mostly working in 3.125V, so it is reasonable in 3.125V. M bullet beads total voltage = 3.125 * m
5, the string of the LED light board parallel and wide voltage:
To make the LED fluorescent lamp work in a wide range AC85-265V in the input voltage range, the LED string of the light board is important. Since the current power supply is generally non-isolated bug power, the output voltage should not exceed 72V when requiring a wide voltage, and the input voltage range is from 85 to 265V. That is, the number of series is not more than 23 strings. There is not too much in parallel, otherwise the operating current is too large, the fever is severe, recommended to 6 and / 8 and / 12 and. The total current does not exceed 240 mAh. There is also a wide voltage plan, just use the L6561 / 7527 to raise the voltage to 400V, then step down, equivalent to two switching power supplies, double cost, this program is not high, no market.
6. The relationship between LED string parallel and PFC power factors and wide voltage:
At present, there are three cases of power supply PFC in the market: one is not a PFC-specific circuit, and its PFC is generally about 0.65; one is to carry a passive PFC circuit, the light board is well received, the PFC is generally about 0.92; In one is made with an active active 7527/6561 circuit, the PFC can reach 0.99, but the cost of this program is doubled than the second solution. So there is a lot of second programs. For passive PFC circuitry: also is also called a gradient PFC circuit, its operating voltage range is half of the peak of AC input voltage. If the input is 180V, its peak is 180 * 1.414 = 254V, half of the peak voltage is 127V, and then subtract a step-down pressure difference 30V, and the maximum output is 90V, so the LED lamp beads are connected in series with up to 28 strings. Therefore, in order to get a relatively large power factor, the number of string of the lamp beads cannot be too much, otherwise, it will not reach the low voltage requirements.
7, constant current accuracy:
The current constant current accuracy of the power supply is too poor, and the constant current of the PT4107 / HV9910 / BP2808 / SMD802 program in the market is ± 8% or ± 10%, and the constant current error is too large. It is generally required to be ± 3%. According to 3% error, the 6-way parallel, the error per path is about ± 0.5%, and if it is 12 ways, the error is about ± 0.25%, which is sufficient. The precision is too high and the cost will increase. And for LEDs, 17 mA and 17.5 mA are not affected.
8, isolation / non-isolation:
Generally, the power supply is made of 15W, placed in the LED tube, its transformer is large, it is difficult to put it. Especially for T6 / T8 lamps, it is almost impossible, so isolating can only be achieved by 15W, more than 15W is very small, and the price is very expensive. Therefore, the cost of isolation is not high, generally non-isolated mainstream, the volume can do smaller, minimum can do 8 mm, in fact, non-quarantined security measures is done, there is no problem.
9, power efficiency:
Output power (output LED voltage * output current) / input power. This parameter is especially important. If the efficiency is low, it means that the input power is partially converted to heat. If it is installed in the lamp tube, it will generate a very high temperature, plus the light effect ratio of our LED. Reissue heat, it will superimpose a higher temperature. The life of all electronic parts inside our power supply will be shortened with temperature. Therefore, the efficiency is the most fundamental factor that determines the life life, and the efficiency cannot be too low, otherwise the heat is consumed too much on the power supply. It is generally more than 80%, but the efficiency is related to the matching method of the light board.
10, size:
The height is the main factor of restrictions, and the size requirements for T6 tube / T8 are generally not too high ≤9mm. The t10 tube is ≤15 mm. The length can be relatively long and easier to heat dissipation.
Editor in charge: CT
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