Previously, the LED fluorescent lighting market was relatively active, and LED drive power supply manufacturers were mainly divided into three major types:
The first category is to develop factories that make LED chips or LED lights, and penetrate into the downstream;
The second category is factories that were originally used for general lighting;
The third category is completely new factories, they used to do power supply or other products or new ventures.
LED fluorescent lamp power supply is a very important part of LED fluorescent lamp. If selected improperly, LED fluorescent lamp will not play its proper performance, and it may not even be used normally. Below I made some small suggestions on LED fluorescent lighting for your reference.
1. Why must LED fluorescent lamp power supply have constant current?
The characteristics of the LED semiconductor determine that it is greatly affected by the environment. For example, when the temperature increases, the current of the LED will increase; when the voltage increases, the current of the LED will also increase. Long-term work exceeding the rated current will greatly shorten the service life of the LED. The LED constant current is to ensure that its working current remains unchanged when environmental factors such as temperature and voltage change.
2. How can the LED fluorescent lamp power supply be matched with the lamp board?
Some customers design the lamp board first, and then find the power supply, and find it difficult to have a suitable power supply. Either the current is too large and the voltage is too small (such as I> 350mA, V <40V); or 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, choose the best serial-parallel connection, the voltage and current applied to each LED are the same, but the effect of the power supply can play the best performance. The best way is to first communicate with the power supply manufacturer, tailor-made.
3. What is the most suitable working current of LED fluorescent lamp power supply?
Generally, the rated working current of LED is 20 mA, and some factories are exhausted from the beginning. The design is 20 mA. In fact, the working heat at this current is very serious. After many comparison tests, the design is 17 to 19 mA. Ideally, the recommended design is 18 mA.
4. What is the working voltage of LED fluorescent lamp power supply?
The recommended working voltage of general LED is 3.0-3.5V. After testing, most of them work at 3.125V, so the calculation formula of 3.125V is more reasonable. The total voltage of M lamp beads in series = 3.125 * M
5. How wide is the series-parallel connection and wide voltage of the LED lamp board?
To make the LED fluorescent lamp work in a relatively wide input voltage range (full voltage) AC85 ~ 265V, the LED series and parallel mode of the lamp board is very important. Since the current power supply is generally a non-isolated step-down power supply, when a wide voltage is required, the output voltage should not exceed 72V, and the input voltage range can reach 85 to 265V. In other words, the number of series does not exceed 23 strings. The number of parallel connections should not be too large, otherwise the working current will be too large and the heat will be severe. It is recommended to use 6 parallel / 8 parallel / 12 parallel. The total current should not exceed 240 mA. There is also a wide voltage solution, which is to use L6561 / 7527 to increase the voltage to 400V, and then step down, which is equivalent to two switching power supplies, and the cost is doubled. This solution is not cost-effective and has no market.
6. What is the relationship between series and parallel LEDs, PFC power factor and wide voltage?
There are three cases of power supply PFC currently on the market: one is without a PFC dedicated circuit, and its PFC is generally around 0.65; one is with a passive PFC circuit, the lamp board is well prepared, and the PFC is generally around 0.92; also Using one is made with active active 7527/6561 circuit, PFC can reach 0.99, but the cost of this scheme is twice as expensive as the second scheme. Therefore, the second option is more. For passive PFC circuits: also called valley-filled PFC circuits, the operating voltage range is half of the peak value of the AC input voltage. If the input is 180V, the peak value is 180 * 1.414 = 254V, half of the peak voltage is 127V, and the maximum output is 90V minus the voltage drop of the step-down type, so the maximum number of LED lamp beads in series is 28 strings. Therefore, in order to obtain a relatively large power factor, the number of lamp beads in series cannot be too large, otherwise, the low voltage requirement cannot be achieved.
7. What is the most suitable constant current accuracy of LED fluorescent lamp power supply?
The constant current accuracy of some power supplies on the market is too bad. For example, the constant current scheme such as the popular PT4107 / HV9910 / BP2808 / SMD802 scheme on the market has an error of ± 8% or ± 10%, and the constant current error is too large. The general requirement is within ± 3%. According to the 3% error, 6 channels are connected in parallel, and the error of each channel is about ± 0.5%. If it is 12 channels in parallel, the error of each channel is about ± 0.25%. This accuracy is enough. If the precision is too high, the cost will increase greatly. And for LEDs, 17 mA and 17.5 mA have little effect.
8. Isolation / non-isolation
Generally, if the isolated power supply is made of 15W, it is placed in the LED lamp tube, and its transformer is very large and difficult to put in. Especially for T6 / T8 lamps, it is almost impossible, so the isolation can generally only be 15W, less than 15W, and the price is very expensive. Therefore, the cost performance of isolation is not high. Generally, non-isolation is more dominant, and the volume can be made smaller. The minimum can be as high as 8 mm. In fact, there is no problem if the non-isolation safety measures are completed.
9. LED fluorescent lamp power efficiency
Output power (voltage output LED * output current / input power). This parameter is particularly important. If the efficiency is low, it means that a large part of the input power is converted into heat. If it is installed in the lamp, it will generate a very high temperature, plus a light efficiency ratio of our LED. If heat is dissipated, a higher temperature will be added. And the life of all electronic parts inside our power supply will shorten with the increase of temperature. Therefore, efficiency is the most fundamental factor that determines the life of the power supply. The efficiency cannot be too low, otherwise the heat consumed on the power supply is too large. Generally more than 80% is enough, but the efficiency is related to the matching connection of the lamp board.
10. LED fluorescent lamp power supply size
Height is the main factor of limitation. Generally, the size of T6 tube / T8 requires that the height should not be too high ≤ 9 mm. The height of the T10 tube is ≤15 mm. The length can be longer, making it easier to dissipate heat.
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