The analysis of several problems often appear in the LED fluorescent lamp power supply

At present, the LED market is very active, the manufacturer is mainly divided into three categories: one category is the original LED chip factories, homeopathy to downstream penetration, not on thecircuit knowledge and understanding of LED fluorescent lamp power supply; the two category is the original do ordinary lighting factory, into a new field, understand some knowledge of circuit the three class is completely new; into the factory, they have other products or new business, to the LED power source and some understanding, some do not understand. LED fluorescent lamp power supply is the most important component in the LED fluorescent lamp, the choice is undeserved, LED fluorescent lamp can not play the performance, can't even normal use.

1, why must be constant current:

Properties of LED semiconductor decided its are influenced by the environment. For example,elevated temperature variation, LED current is increased, the increase of the voltage, the electric current will increase LED. Long term exceeds the rated current work, will greatly shorten the service life of LED. LED constant current is the changes in temperature and voltage and otherenvironmental factors, to ensure that the work of constant current.

Match 2, LED fluorescent lamp power supply and the lamp plate:

Some customers to design the lamp panel, then find the power, found it very difficult to have the appropriate power supply, voltage or current is too large, too small (such as I>350mA, V<40V); orthe current is too small, the voltage is too high (e.g. I<40mA, V>180V), the result is a serious fever,low efficiency, or the input voltage range is not enough. In fact, the choice of a most excellentseries parallel connection mode, and in each of the LED on the voltage and current are the same,but the effect of the power supply can play the best performance. The best way is to firstcommunication and power supply manufacturers, tailored.

The operating current of 3 and LED:

Rated working current is generally LED to 20 mA, some factories started to use as much as 20 mA,design, in fact this current work under the heating is very serious, after repeated contrast test,designed to be 17 Ma is the ideal. The total current =17*N N circuit parallel;

The working voltage of 4 and LED:

The recommended operating voltage of general LED 3.0-3.5V, tested, most of the work in 3.125V,so according to the formula of 3.125V reasonable. The total voltage =3.125*M M lamp series

Series parallel and wide voltage 5, an LED lamp panel:

The range of AC85-265V to make the LED fluorescent lamp at the input voltage range is relatively wide, then the lamp panel series parallel LED mode is very important. Due to the current power source for non isolated buck power, at the request of wide voltage, the output voltage is not more than 72V, the input voltage range is can reach 85-265V. That is to say, the series number no more than 23 series. Parallel number is not too much, otherwise the operating current is too large,serious fever, recommended for 6 and /8 and /12 and. The total current does not exceed 240 Maas well. There is a wide voltage scheme, is the first to use L6561/7527 to voltage up to 400V, and then the buck, the equivalent of two switching power supply, cost twice as expensive, this schemethe price is not high, there is no market.

Between the serial and parallel with the PFC power factor and wide voltage, the 6 LED:

At present, the power of PFC on the market there are three situations: one is the PFC withoutspecial circuit, the PFC in general about 0.65; one with passive PFC circuit board, light horseprepared well, PFC in general about 0.92; also used one is the use of an active 7527/6561 circuit,PFC can reach to 0.99, but the project cost more than twice as expensive as the second kind ofscheme. So the second schemes are more. For passive PFC circuit: also called the valley fill circuit PFC, half of the AC input voltage peak is the working voltage range. If the input is 180V, the peak value is 180*1.414=254V, half the peak voltage is 127V, minus the step-down pressure differenceof 30V, the maximum output is 90V, so the LED lamp series number 28 on. Therefore, to get thepower factor is relatively large, the number of beads in series can not be too much, otherwise, it is not up to the requirements of low voltage.

7, the precision of constant current:

Market some power supply constant current accuracy is poor, as the popularity of the scheme of PT4107/HV9910/BP2808/SMD802 constant current scheme, error reaches + 8% or + 10%, error constant too large. General requirements can be within + 3%. According to a 3% error, 6 roadparallel error of each road is about 0.5%, if the road is 12 parallel error of each road is about 0.25% and the precision is enough. Precision is too high, the cost will be increased greatly. But for LED, 17 Ma and 17.5 Ma has little effect.

8, isolation / non isolation:

The general power supply isolation as made of 15W, on the LED in the tube, the volume of the transformer is large, it is difficult to put in. Especially for T6/T8 lamp, almost impossible, so in general can only be isolated do 15W, rarely more than 15W, and the price is very expensive.Therefore, the isolation of the price is not high, the general non isolated mainstream more, the volume can be made smaller, the minimum can be 8 mm high, in fact, safety measures of non isolated well, there is no problem.

9, power supply efficiency:

Output power (voltage * output LED current output / input power). This parameter is very important,if the low efficiency means that a large part of the input power is converted into heat emitted; if it isinstalled in the lamp will be produced in a high temperature, a light efficiency of our LED plus than the radiating heat, will be superimposed to generate higher temperature and internal power supply.All of our electronic parts of the life will be shortened with the rising of temperature. So the efficiency is the most fundamental factor power life, efficiency is too low, otherwise the powerconsumption in the heat too high. In general more than 80% can, however, efficiency and the lamp plate matching connection related.

10, size:

Height is the main factor limiting, generally used for T6 tube /T8 size requirements can not be too high is less than or equal to 9 mm in height. T10 tube height less than or equal to 15 mm. The length can be too long, easy to heat.