An LED street light, lighting 40 1W LEDs, take this ratio, and several solutions to compare advantages.
The first way, non-isolated buck drive, a series of constant current, the biggest advantage of this way is the highest efficiency, 40 strings, 350MA constant current, but the reliability is not so, because non-isolated circuits have this Weakness, although high efficiency and high efficiency, is also because a large part of the energy in the power grid is directly added to the LED, and the role of the power supply is to temporarily store a part of the energy and then release it when appropriate, so what is the interference in the power grid? It is easy to add to the LED, and the LED is a kind of non-linear load. When the current is stable, the voltage is at a certain value. This voltage is generally about 3. 3V. When there is an instantaneous high voltage in the power grid. Generally speaking, when it is called surge voltage, because the LED load is in the series of 300V filter electrolysis, the high voltage coming in will be directly applied to the two ends of the LED. At this time, because of this characteristic of the LED, there will be a big moment. When the current flows, it is equivalent to a short circuit, and the detection part of the constant current power supply or even the chip of the constant current source is destroyed in an instant. So now many of the step-down circuits will damage the switch tube, especially with the 9910. Many people say that in fact, the buck power supply drives the LEDs with such limitations, so the non-isolated circuit, although high efficiency and low cost, However, it can only be used in low-cost occasions, where the consumer goods can bear the risk of bad. So this method is the most efficient, but it is definitely the first to be PASS.
The second, isolated, high-voltage constant current source, this method is slightly better, but the efficiency will be lower than non-isolated, but the most important point is that the output voltage is too high, the voltage is too high, the problem is always a little, like In this part of the power supply, the short circuit is easy to blow up, and its anti-input surge performance is relatively poor. It turns out that the high-voltage output of the LED driver power supply , but the low-voltage output of the LED power supply is highly reliable, but the low-voltage output of the LED power supply, although the reliability has gone up, but the efficiency is down. Reliability and efficiency are contradictory, and only one balance point can be chosen.
Just because the high voltage is not working, I think of the low voltage, but the low voltage will be the number of branches, so there will be a third type, first constant pressure, and then shunt constant current, this reliability is of course higher than Both are better, but the efficiency is of course lower. However, the risk of street lamps is too great. First of all, of course, reliability is high, and efficiency is second.
But in fact, this method is not the best, and it is completely suspicion of painting. The mistake is wrong in the latter stage and still constant flow. For example, these forty LEDs, how do you want to do it, first reduce the voltage to 50V, and then do four constant currents, ten each. Increase the cost, let's not say, let go, let's talk about efficiency first, generally DC/DC, 350MA, it is 90%, right, if you use a constant voltage power supply, ten voltages will be about 33V, then one more 5R's resistance, the voltage value is only less than 2V, the precise setting voltage, let the current reach about 350MA, so the efficiency will not be lower than DC/DC. Let's talk about reliability, a resistor, as long as the power is large enough, it is definitely much more reliable than your circuit. Also, the LED driver circuit, which is most afraid of the surge voltage of the input stage, directly adds a resistor, which is good for suppressing the surge. Otherwise, the surge is transmitted to the DC constant current part, and the possibility of damaging the DC part is also increased. Big. In fact, the first constant pressure, the constant current, divided into several strings, there is no need at all, it is not as direct constant pressure, resistance current limit, more convenient, efficiency is not low, more reliable.
The above, just from the principle, then look at the actual situation of the power supply. This basic needless to say, that is because of LED, so many people began to study, making constant current power, but in general, these constant current sources, whether non-isolated, isolated, high-voltage, or low-voltage, its technology Maturity, or the richness of application experience, is far less than the constant voltage power supply. Especially in the conventional constant voltage power supply, you have to be reliable. You can use the industrial power supply. You can use the 36V industrial power supply. If you use the good brand, you can use the famous latitude or something. Certification, what certification is there, UL has it. Which constant current power supply you see now, which one is certified? This is very important, the conventional constant voltage power supply is mature, and the constant current power supply is not mature.
Therefore, no matter from the principle analysis, or the actual situation of the switching power supply industry, taking into account the reliability and efficiency, it can be said that the reliability is the best, the actual feasibility is the highest, the best LED street light driving power supply is: Conventional 36V industry Level constant voltage power supply!
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