10 Knowledge Points of Led Flood Light Technology
October 20, 2022
1. Why does the voltage of LED Outdoor Flood Light need constant current?
The characteristics of LED lighting materials determine that they are greatly affected by the environment. For example, if the temperature changes, the current of the LED will increase, and the voltage will increase, and the current of the LED will also increase. Exceeding the rated current for a long time will greatly shorten the service life of the LED lamp beads. The LED constant current is to ensure that its operating current value remains unchanged when environmental factors such as temperature and voltage change. 2. LED outdoor Flood Light power constant current accuracy
Some power supplies on the market have poor constant current accuracy. For constant current solutions such as popular recommended solutions on the market, the error reaches ±8%, and the constant current error is too large. The general requirement is ±3%. According to the 3% design scheme. The production power supply needs to be fine-tuned to achieve ±3% error. 3. Working voltage of LED outdoor flood light power supply
Generally, the recommended working voltage of LED is 3.0-3.5V. After testing, most of them work at 3.2V, so it is more reasonable to calculate according to 3.2V. The total voltage of N lamp beads in series = 3.2*N 4. What is the appropriate unit for the working current of the LED outdoor flood light power supply?
For example, the rated working current of the LED is 350 mA. Some lighting design factories use it up at the beginning and design 350 mA. In fact, the working heat is very serious under this current. After many comparison tests, the design of 320 mA is relatively ideal. Minimize heat generation and allow more electrical energy to become visible light energy.
5. How wide is the series-parallel and wide voltage of the LED outdoor flood light power board?
In order to make the LED street lamp power supply work in the range of AC85-265V with a wide input voltage range, the series-parallel mode of the LEDs of the lamp board is very important. Try not to use a wide voltage, and it can be divided into AC220V and AC110V as much as possible, so as to ensure the reliability of the power supply. Since the current power supply is generally a non-isolated step-down constant current power supply, when the required voltage is 110V, the output voltage should not exceed 70V, and the number of series connections should not exceed 23 strings. When the input voltage is 220V, the output voltage can reach 156V. That is to say, the number of concatenations does not exceed 45 strings. The number of parallel connections should not be too many, otherwise the working current will be too large and the power supply will heat up seriously. There is also a wide voltage solution, APFC active power compensation is to use L6561/7527 to raise the voltage to 400V first, and then step down, which is equivalent to two switching power supplies. This program is only used under certain conditions. 6. Isolation/non-isolation
Generally, the isolated power supply is made into 15W and placed in the power tube of the Led Street Light. The transformer is very large and difficult to put in. It mainly depends on the space structure and depends on the specific situation. Generally, the isolation can only achieve 15W, and there are few more than 15W, and the price is very expensive. Therefore, the cost-effectiveness of isolation is not high. Generally, non-isolation is more mainstream, and the volume can be made smaller, and the minimum height can be 8 mm. In fact, there is no problem with non-isolation safety measures. It can also be used as an isolated power supply if space permits. 7. How can the power supply of Led Flood Light be matched with the lamp bead board?
Some customers design the light board first, 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 7X1WI>350mA, or V<20V); or the current is too small and the voltage is too high (such as I<200mA or V>25V), the result is severe heat generation, low efficiency, or insufficient input voltage range. In fact, if you choose an optimal series-parallel connection method, the voltage and current applied to each LED are the same, and the effect of the power supply can exert the best performance. The best way is to communicate with the power supply manufacturer first and customize it. Or produce your own power supply. 8. LED series and parallel connection and PFC power factor
The capacity of the isolated input AC220V high-voltage terminal electrolytic capacitor is generally based on the input power of 1W=1UF, and AC110V1W=2UF. There are three cases of power supply PFC on the market: One is without PFC and no power factor compensation special circuit, and its PF value is generally around 0.65; The second type is the passive power factor compensation PFC circuit, that is, the passive power factor compensation lamp, also known as the flow-by-current circuit board, which is currently the most widely used and has the best reliability, and the PF value is generally around 0.92; There are also three types of lighting projects that use active 7527/6561 circuits, that is, active power factor compensation, which is called AC220V in APFC circuits, and AC110V can use electrolytic capacitors of the same capacity, choose 1W=1.5UF. The PF value can reach 0.99, but the cost of this scheme is twice as expensive as that of the second scheme, and the reliability is slightly worse. So the second option is used more. For passive PFC circuits: also known as valley-filling PFC circuits, the DC operating voltage range is half of the peak value of the AC input voltage. If the input is 220V, the peak value is 220*1.414=312V, half of the peak voltage is 156V, and the output wave is the upper half wave without the lower half wave on the basis of non-isolation. 9. Power efficiency of LED flood light power supply
Input power minus output power value, this parameter is particularly important, the larger the value, the lower the efficiency, which means that a large part of the input power is converted into heat and dissipated; if it is installed in the lamp, it will generate a very high temperature , coupled with the heat emitted by a light efficiency ratio of our LED, it will be superimposed to generate a higher temperature. And the life of all electronic parts inside our power supply will be shortened as the temperature rises, so efficiency is the most important factor in determining the life of the power supply. The fundamental factor, the efficiency can not be too low, otherwise the heat consumed on the power supply is too large. The efficiency of the non-isolated type is higher than that of the isolated type, generally more than 80%. However, the efficiency is related to the matching connection method of the lamp board. 10. Power dissipation of LED outdoor flood light
The main factor of the heat dissipation scheme is that the LED street lamp power beads can greatly prolong the life when they are not overheated. Generally, aluminum alloy is used, which is easier to dissipate heat. That is, the LED street lamp power supply beads are attached to the aluminum substrate, and the external heat dissipation area is expanded as much as possible.
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