1, LED street lamp power why must constant current?
The characteristics of LED lighting materials decide that it is greatly influenced by the environment. For example, the temperature changes will increase, the current of LED will increase, the voltage will increase, and the current of LED will also increase. Long exceed the rated current, will greatly shorten the service life of the LED lamp. And LED constant current is to change the temperature and voltage and other environmental factors, to ensure that the current value of the working current is constant.
Constant current precision of 2 and LED street lamp
The constant current accuracy of some power supplies on the market is poor, such as the constant current scheme, such as the popular recommendation scheme on the market, and the error is up to 8%, and the constant current error is too large. The general requirement is 3%. According to the 3% design. The production power should be adjusted to an error of 3%.
The working voltage of 3, LED street lamp power supply
The recommended working voltage of the general LED is 3.0-3.5V. After testing, most of the work is in the 3.2V, so it is more reasonable to calculate the 3.2V. The total voltage =3.2*N N lamp series
4, LED street lamp power supply current is what is the most suitable?
For example, the rated working current of LED is 350 Ma, and some lighting design factories are used at the very beginning, and the design is 350 ma. In fact, the heat generated under this current is very serious. It is ideal to design 320 Ma after many tests. Minimize the amount of heat, so that more electricity can be turned into visible light energy.
5, how wide is the series parallel and wide voltage of the power board of the LED street lamp?
In order to make the LED street light power supply working in a wide range of input voltage range AC85-265V, the LED series parallel mode of the lamp board is very important. Do not use wide voltage, can be divided into AC220V, AC110V as far as possible to classify, so as to ensure the reliability of the power. Since the current power is generally a non segregated step-down constant current power supply, the output voltage should not exceed 70V when the voltage is required to be 110V, and the number of series is not more than 23 series. When the input voltage is 220V, the output voltage can reach 156V. That is to say, the number of series is not more than 45 strings. Not too many parallel numbers, otherwise the work current is too large, the power supply is serious. There is also a wide voltage scheme, APFC active power compensation is to use L6561/7527 to raise the voltage to 400V, and then depressurization, equivalent to two switching power. The scheme is used under certain conditions.
6, isolation / non isolation
The general isolation power, such as 15W, is placed in the power pipe of the LED street lamp, and its transformer is very large and difficult to put in. The main view of the space structure depends on the specific situation, the isolation of the general only can only do 15W, more than the 15W is very little, and the price is very expensive. Therefore, the cost performance of isolation is not high. Generally, non isolation is the main source, and the volume can be smaller. The smallest can achieve 8 millimeters. In fact, there is no problem with the safety measures that are not isolated. Space allowed also can be used as an isolated power supply.
7, LED lighting power supply to what can be matched with the lamp board?
Some customers to design a good light board, and then find the power, find it difficult to have the right or power, the current is too large, the voltage is too small (such as 7X1WI>350mA or V<20V); or the current is too small, the voltage is too high (such as I<200mA or V>25V), the result is serious fever, low efficiency, or the input voltage the scope is not enough. In fact, the selection of the best series connection mode, the voltage and current added to each LED is the same, and the effect of the power supply can play the best performance. The best way is to communicate with the power supplier first, and to make it tailor - made. Or the power supply has been produced by itself.
8, LED series parallel and PFC power factors
Isolated input AC220V high voltage electrolytic capacitor capacity to input power 1W=1UF, AC110V1W=2UF power PFC currently on the market there are three types: one is without PFC power factor compensation special circuit, the PF value is generally about 0.65; the two is the passive power factor compensation circuit PFC, which is a passive power the compensation factor of light, also called by the current circuit board is currently the most widely used reliability best, PF value is generally about 0.92; there are three kinds of lighting engineering with an active 7527/6561 circuit, which is an active power factor compensation, known as the AC220V APFC circuit, AC110V can use the electrolytic capacitor with the same capacity, selection 1W=1.5UF. The PF value can reach 0.99, but the cost of the scheme is a little worse than the reliability of the second schemes. So the second schemes are used more. For passive PFC circuits, also called Valley filled PFC circuits, the DC operating voltage range is half the peak value of the AC input voltage. If the input is 220V, its peak value is 220*1.414=312V, and the peak voltage is half 156V, and the output wave on the non isolated mode is the upper half wave without the lower half wave. So the number of LED streetlights in series is up to 45 strings. Therefore, in order to get the power factor is relatively large, the series number can not be too little light, otherwise it is not up to the best working condition, and how many turns of secondary winding number related series in the isolated power supply, the power supply must be done to meet the output power. The smaller the working current of the electronic component is in the rated voltage working range, the longer the heating life is, the shorter the life will be. LED street lamp power beads are sensitive to the amount of communication, and the higher the amount of communication is, the worse the light is. In general, it is necessary to use electrolytic capacitor to maintain the voltage, as far as possible to reduce the exchange weight of the output voltage. The capacity of the electrolytic capacitor at the bottom pressure is not too small and the capacity is too small.