Industry new
Ten Knowledge Points about LED Street Light
The lighting engineering of LED lighting industry is not only influenced by the global environment, but also has its industry particularity. LED street lamp power supply is the most important part of the current led development. There are a variety of schemes and unique design methods for the relevant design of LED technology. These are basic knowledge. Let's learn about them.
1. D working voltage of street lamp power supply
Generally, the recommended working voltage of LED is 3.0-3.5v. After testing, most of them work at 3.2V, so the calculation formula of 3.2V is reasonable. Total voltage of N lamp beads in series = 3.2 * n LED street lamp
2. D constant current accuracy of street lamp power supply
The constant current accuracy of some power sources on the market is poor, such as the popular recommended scheme and other constant current schemes. The error is up to ± 8%, and the constant current error is too large. The general requirement is ± 3%. According to 3% design plan. The production power supply needs to be adjusted to achieve ± 3% error.
3. How wide is the series parallel connection and wide voltage of D street lamp power board?
In order to make the LED street lamp power supply work in a wide range of input voltage AC85-265V, the LED series parallel connection mode of the lamp board is very important. Try not to use wide voltage. It can be divided into AC220V and AC110V, so as to ensure the reliability of power supply. As the current power supply is generally non isolated step-down constant current power supply, when the required voltage is 110V, the output voltage shall not exceed 70V, and the number of series connection shall not exceed 23. When the input voltage is 220V, the output voltage can reach 156v. That is to say, the serial number shall not exceed 45. The number of parallel connection should not be too much, otherwise the working current is too large and the power supply is heated seriously. There is also a wide voltage scheme, APFC active power compensation is to use L6561 / 7527 to raise the voltage to 400V, and then reduce the voltage, equivalent to two switching power supplies. This plan is only used under certain conditions.
4. Why does D street lamp power supply have to be constant current?
The characteristics of LED lighting materials determine that they are greatly affected by the environment. For example, when the temperature changes, the current of LED will increase, the voltage will increase, and the current of LED will also increase. Long term operation over rated current will greatly shorten the service life of LED lamp beads. The constant current of LED is to ensure that the working current value is constant when the environmental factors such as temperature and voltage change.
5. D series parallel connection and PFC power factor
In general, the electrolytic capacitance capacity of isolated input AC220V high-voltage terminal is 1W = 1uF, and ac110v1w = 2uF. At present, there are three types of power PFC in the market:
One is without PFC, and its pf value is about 0.65;
Two are passive PFC circuit, that is, passive PFC lamp, also known as the current by current circuit board is the most widely used and the best reliability, PF value is generally around 0.92;
There are also three kinds of lighting engineering with active active 7527 / 6561 circuit, that is, active power factor compensation, called AC220V in APFC circuit, AC110V can use the same capacity of electrolytic capacitor, 1W = 1.5uf. The PF value can reach 0.99, but the cost of this scheme is a little less than twice the reliability of the second scheme.
So the second one is more used. For passive PFC circuit: also known as valley filling PFC circuit, its DC working voltage range is half of the peak value of AC input voltage. If the input is 220V, its peak value is 220 * 1.414 = 312v, half of the peak voltage is 156v, and the output wave is the upper half without the lower half on the basis of non isolation.
Therefore, the number of LED street lamp power beads in series should be no more than 45 strings. Therefore, in order to get a larger power factor, the number of lamp beads in series should not be too small, otherwise it will not reach the best working state. The number of series connected on the isolated power supply is related to the number of turns of the secondary winding, and the power supply must meet the output power. The lower the working current of the electronic components in the rated voltage working range, the longer the bottom heating life, and the shorter the life. LED street lamp power bead is very sensitive to AC weight, the higher the AC weight, the worse the light comfort. Generally, the electrolytic capacitor should be used to maintain the voltage and reduce the AC component of the output voltage as much as possible. The capacity of the electrolytic capacitor at the bottom pressure end should not be too small. The ratio of the capacity to the output current is 1uF < 1.5mA, otherwise the LED will flash. The selection of high-voltage electrolytic capacitor at the input of non isolation type is the same as that of isolation type, and the selection of capacitor at the output is 1uF < 6mA. The electrolytic capacitance of dimming LED power supply at the output end shall meet 1uF < 0.5mA.
6. What is the most appropriate working current of D street lamp power supply?
For example, the rated working current of LED is 350 ma. Some lighting design factories use it up at the very beginning. In fact, the working heat is very serious under this current. After many comparative tests, the design of 320 Ma is ideal. Reduce the heat as much as possible, and make more electric energy into visible light energy.
7. non isolation
Generally, if the isolated power supply is made of 15W, it is placed in the LED street lamp power pipe, and the transformer is very large, so it is difficult to put it in. It mainly depends on the specific situation of the space structure. Generally, only 15W can be achieved for the isolated ones, and few are more than 15W, and the price is very expensive. Therefore, the cost performance of isolation is not high. Generally, non isolation accounts for a large proportion of the mainstream. The volume can be smaller, and the minimum height can be 8mm. In fact, there is no problem when the non isolation safety measures are done. The space allowed can also be used for isolated power supply.
8. How can d street lamp power supply match with lamp bead board?
Some customers first design the lamp board, then find the power supply, and find it difficult to have a suitable power supply, either 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), resulting in serious heating, low efficiency, or transmission