LED lamp power supply is the most important component in the LED daylight lamp, improper selection can not let LED fluorescent lamp play performance, and can’t even normal use. In cooperation with the customer process, when you found some errors, then you should give some suggestions and reference for customer selection.
1 why must be constant: the characteristics of LED semiconductor decided their environments that are affected. For example, when the temperature increases, the LED current will be increased, the increase of the voltage, the electric current will increase LED. Long term exceeds the rated current, so the service life will be greatly reduced LED. While LED is in constant temperature and voltage variations and other environmental factors, in order to ensure the constant working current.
2 LED lamp power supply and the lamp board: some customers design the light board, then to find power. Finally, they find it very difficult to have the appropriate power supply, voltage or current is too large, too small (such as I, 350mA, V < 40V); or the current is too small, the voltage is too high (such as I 40mA, V > 180V), the result is made is a serious fever, low efficiency, or the input voltage range is not enough. In fact, choose one of the most excellent series-parallel connection mode and in each of the LED on the voltage and current are the same, but the power’s effect is to play the best performance. The best way is to communicate with power supply manufacturers to be tailored.
3 LED operating current: rated working current LED is 20 mA, some factories began to use as much as 20 mA, design, in fact this current work under the heating is very serious, after repeated experiments, designed 16-18 Ma is the ideal. The total current =17 * N parallel N;
4 LED: recommended working voltage of LED is 3.0-3.5V, after testing, most of the work in 3.125V, so according to the formula of 3.125V. The total voltage =3.125* M M lamp series Series-parallel and wide voltage
5 LED lamp board: the range of AC85-265V to make the LED fluorescent lamp is wide in the input voltage range, the lamp panel LED series and parallel modes is very important. Due to the current power supply for step-down power non-isolated, at the request of wide voltage, output voltage shall not exceed 72V; the input voltage range can reach 85-265V. That is to say, the series number should be no more than 23 strings. Parallel number is not too much, otherwise the working current is too large, serious fever, recommended for 6 and /8 and /12 and. The total current does not exceed 240 Ma as well.
There is a wide voltage scheme. That is the first to use L6561/7527 voltage up to 400V, and then the buck, the equivalent of two switching power supply, twice times expansive, if the price is not high, there is no market.
6 the current power PFC on the market there are three situations: one is without PFC special circuit, the PFC in general is about 0.65; one with the passive PFC circuit, lamp panel was prepared, PFC in general is about 0.92; it also used one active 7527/6561 circuit, PFC can reach 0.99, but the project cost more than twice as expensive as second kinds of scheme.
For passive PFC circuit: it also called the valley-fill circuit of PFC, half of the AC input voltage peak is the working voltage range. If the input is 220V, the peak value is 220*1.414=310V, half peak voltage is 155V, minus two series capacitor divider 1/2, the maximum output is 77V, so the LED lamp series number 24 on. This is why light board on the market generally made of 23 series or 24 series. If the input is 110V, the output power is PFC: 110*1.414*1/4=38V, number of beads with the 12 string. So, in the area of 110V, with PFC is more troublesome, the number of no more than 12 strings of beads. Therefore, to get the power factor is relatively large, series number cannot too much, otherwise, and it can not reach the low voltage requirements.
7 constant current accuracy: some power supply constant current accuracy in the market is poor, like the popular PT4107/HV9910/BP2808/SMD802 scheme of constant flow scheme, error is ± 8% and ± 10%, error constant is too large. General requirements can be within ± 3%. According to the 3% errors, 6 parallel, error of each road about ± 0.5%, if 12 parallel, error of each road about is ± 0.25%, the accuracy is enough. Precision is high, the cost will increase greatly. But for LED, 16 Ma and 18 Ma has little effect.
8 isolation / non-isolated power supply such as: general isolation is 15W, in the LED tube, the volume of the transformer is very big, and it is difficult to put in. Especially for T6/T8 lamp, it is almost impossible, so in general it can only be isolated to 10W, rarely more than 10W, and the price is very expensive. So, isolation of the price is not high, the general is not isolated mainstream more, the volume can be made smaller, the minimum can be 8 mm high, in fact, safety measures and non-isolated ready, there is no problem.
9 power efficiency and power factor: power factor is the ratio of the active power and total power (PHI), wattless power the rest of the mutual transformation in power system, the electric meter can not measure the wattless power meter, the user will not have any impact, only the power supply bureau does not receive the user who has no power of money. While the efficiency (y) is the ratio of the output power and input power, output power (voltage output LED output current) / input power, this parameter is very important, which relates to the product and the interests of users, if the low efficiency means that a large part of the input power is converted to heat emitted; if it is installed in the lamp, it will be produced in a high temperature, a light efficiency of our LED plus than the heat, and it will obtain higher temperature. We all electronic parts of the life will be shortened with increasing temperature. High efficiency, conversion into light efficiency will be high, and the heating power and the tube reduction, equivalent to saving, product performance and life will improve. So that the efficiency is the most fundamental power life factor, efficiency is too low, or consumption in power on the heat is too large. It is generally above 0.8-0.9.
The power factor, the two indicators of efficiency sometimes restrict each other, and is related to the output current products, in order to improve the efficiency, output as high voltage, low current. Internal control standard of our company is generally 0.80-0.90 of power factor, efficiency is 0.82-0.90. Our existing customers in the power factor and efficiency trade-offs, they tend to improve the efficiency, and power factor is above 0.80.
10 dimensions: height is the main factor limiting, generally used for T6 /T8 size ≤ 9 mm, the height can not be too high. T10 tube high = 15 mm.
11 CE authentications: the LED fluorescent lamps exports more abroad, so they are generally required to achieve CE certification. CE includes two parts, one is the low voltage directive, it is the main insulation and pressure resistant performance, it generally can reach; another part is the electromagnetic compatibility directives, mainly refers to the EMC, electromagnetic interference and anti-interference, this part is difficult to achieve. Whether it is passed CE certification or not, just look at the power input part, the input filter capacitor and a ring of common mode inductors, may through the CE products, if there is no common mode inductors through CE, it certainly is a lie.