1, LED street lamp power supply why must constant it?
The characteristics of LED lighting materials determine its impact by the environment, such as temperature changes, LED current will increase, the voltage increases, LED current will increase. Long over the rated current work, will greatly shorten the LED lamp life. The LED constant current is in the temperature and voltage and other environmental factors change, to ensure that its working current value unchanged.
2, LED street lamp power constant current accuracy
Some of the power supply on the market constant current accuracy is poor, like the popular recommendation of the market and other constant current program, the error of ± 8%, constant current error is too large. General requirements in ± 3% on it. Press 3% of the design. Production power to be fine-tuned to achieve ± 3% error.
3, LED street lamp power supply voltage
General LED recommended operating voltage is 3.0-3.5V, tested, most of the work in 3.2V, so the calculation by 3.2V more reasonable. N lamp beads in series with the total voltage = 3.2 * N.
4, LED street lamp power supply current is how much is the most appropriate?
For example, LED rated current 350 mA, and some lighting design plant used to do, the design of 350 mA, in fact, this work under the current heat is very serious, after several comparative tests, designed to 320 mA is the comparison ideal. Try to reduce the amount of heat, so that more energy into visible light.
5, LED lights power board in series with the wide voltage to how wide it?
To make LED street lamp power supply in the wide range of input voltage range AC85-265V, then the light board LED string parallel way is very important. Try not to use wide voltage, can be divided into AC220V, AC110V as much as possible classification, so as to ensure power supply reliability. As the current power supply is generally non-isolated step-down constant current power supply, the required voltage 110V, the output voltage should not exceed 70V, the series number does not exceed 23 string. Input voltage 220V output voltage can reach 156V. In other words, the number of series does not exceed 45 strings. Parallel number not too much, otherwise the working current is too large, power fever 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 buck, the equivalent of two switching power supply. This program is used under certain conditions.
6, isolated / non-isolated
General isolation power supply such as made 15W, on the LED lights in the power supply, the transformer is very large, it is difficult to put into. Mainly to see the spatial structure, depending on the specific circumstances, the isolation can only be done in general 15W, more than 15W very little, and the price is very expensive Therefore, the isolation of the price is not high, generally non-isolated accounted for more mainstream, the volume can be done smaller, the minimum can be high 8 mm, in fact, non-isolated security measures done, there is no problem. Space allows you to do the isolation power supply.
7, LED street lamp power to what can be done with the lamp beads board match?
(Such as 7X1WI> 350mA, or V <20v); or the current is too small, the voltage is too high (such as the current is too small, the voltage is too high I <200ma or v> 25V), the result is severe heat, low efficiency, or insufficient input voltage range. In fact, choose a best string and parallel way, plus the voltage and current on each LED is the same, and the power of the effect can play the best performance. The best way is to first communicate with the power supply manufacturers, tailor-made. Or self-produced power.
8, LED series and parallel with the PFC power factor
Isolated input AC220V high voltage side of the electrolytic capacitor capacity is generally the input power 1W = 1UF, AC110V1W = 2UF currently on the market power PFC there are three cases:
One is without PFC power factor compensation dedicated circuit, the PF value is generally around 0.65;
Two are passive power factor compensation PFC circuit, that is, passive power factor compensation lamp, also known as flow-through circuit board is currently the most widely used the best reliability, PF value is generally around 0.92;
There are three active active 7527/6561 circuit to do the lighting project, that is, active power factor compensation, known as the APFC circuit AC220V, AC110V can use the same capacity electrolytic capacitors, use 1W = 1.5UF. PF value can reach 0.99, but the cost of this program than the second program twice the reliability of slightly worse.
So the second program with more. For passive PFC circuits: also known as padded PFC circuits, the DC operating voltage range is half the peak of the AC input voltage. If the input is 220V, the peak is 220 * 1.414 = 312V, half of the peak voltage is 156V, on the basis of non-isolated output wave for the first half of the wave is not the second half of the wave.
So the LED street lamp power pin series up to 45 string below is appropriate. Therefore, in order to get a relatively large power factor, the number of series of lamp beads can not be too little, otherwise it will not reach the best working condition, the number of isolated power supply in series with the number of secondary winding number, must be done Power supply to meet the output power. Electronic components in the rated voltage range of working current, the smaller the heat the end of life, the longer the life expectancy will be shorter. LED street lamp power beads are very sensitive to the exchange of weight, the higher the amount of communication, the worse the light comfort. Generally use electrolytic capacitors to maintain the voltage, as far as possible to reduce the output voltage AC component, the bottom voltage side of the electrolytic capacitor capacity can not be too small, the capacity and output current ratio of 1UF <1.5ma otherwise led will appear flashing. Non-isolated input high-voltage electrolytic capacitor selection and isolation of the same, the output capacitor selection 1uf <6ma. Dimming led power supply in the output electrolytic capacitor to meet 1uf <0.5ma.
9, LED street lamp power supply efficiency
Input power minus the output power value, this parameter is particularly important, the greater the value of the lower efficiency, it means that a large part of the input power into heat out; if installed in the lamp will produce a very high temperature , Plus our LED a luminous efficiency than the heat, will be superimposed to produce a higher temperature, and our internal power supply of all electronic parts will increase with the temperature rise, so that efficiency is to determine the power life of the most The fundamental factor, the efficiency can not be too low, otherwise consumed in the power of the heat is too large. Non-isolated efficiency is higher than the isolation type, generally more than 80% can, but the efficiency of the matching with the light board connection.
10, LED lights power supply cooling
Cooling program is the main factor is the LED street lamp power beads in the use of thermal conditions can greatly extend the life, generally with aluminum, easier to heat. That is, LED street lamp power beads posted on the aluminum plate, the external as far as possible to expand the cooling area. The face of such a broad LED market is full of vitality, the main scientific development, a few areas of technology can achieve a leading position, I believe that China's LED enterprises will be more powerful.