Ten problems affecting LED lighting power supply (two)

How wide is the series and parallel voltage of the 5.LED lamp board?

In order to make the LED fluorescent lamp work in a wide range of input voltage range (full voltage) AC85 ~ 265V, then the LED series is very important. Due to the current power supply is generally non isolated buck power supply, when the demand for a wide voltage, the output voltage does not exceed 72V, the input voltage range is up to 85 ~ 265V. In other words, no more than 23 string series.

The number of parallel do not too much, otherwise the working current is too large, severe fever, recommended for 6 and /8 and /12 and. The total current does not exceed 240 ma. There is also a wide voltage program, is the first to use L6561/7527 to raise the voltage to 400V, and then buck, equivalent to two switching power supply, the cost of double the cost of this program is not high, there is no market.

What is the relationship between 6.LED series parallel and PFC power factor and wide voltage?

The current PFC power supply on the market there are three types: one is PFC without a dedicated circuit, the PFC is generally around 0.65; one with passive PFC circuit board, the light horse prepared well, PFC is generally around 0.92; also used one is the use of an active 7527/6561 circuit. PFC can reach 0.99, but this program costs more than twice as expensive as second schemes.

So more than second programs. For a passive PFC circuit, also known as a valley filled PFC circuit, the operating voltage range is half the peak of the AC input voltage. If the input is 180V, the peak value is 180*1.414=254V, half peak voltage is 127V, minus the step-down pressure 30V, the maximum output is 90V, so LED lamp series number 28 series.

Therefore, in order to get the power factor is relatively large, the series number can not be too much light, otherwise, it is not up to the requirements of low voltage.

7.LED fluorescent lamp power supply constant current accuracy is the most appropriate?

Some of the market power supply constant current accuracy is too poor, like the popular PT4107/HV9910/BP2808/SMD802 programs on the market, such as the constant flow of the program, the error of 8% + or + + +, the constant current error is too large. General requirements in + 3% on it.

According to the error of 3%, parallel to the road, the error of each road is about + 0.5%, if it is in parallel with the road, the error of each road is about + 0.25%, the accuracy of the is enough. Accuracy is too high, the cost will be greatly increased. And speaking of LED, 17 Ma Pei and 17.5 Ma culture little impact.

8 isolation / non isolation

General isolation power such as made of 15W, placed in the LED lamp, the transformer volume is very large, it is difficult to put into. In particular, the T6/T8 lamp, almost impossible, so the general isolation can only do 15W, more than 15W, and the price is very expensive. So, isolation of the price is not high, generally non mainstream more isolated, the volume can be made smaller, the minimum can be 8 mm high, in fact, the security measures of non isolated well, there is no problem.

9.LED fluorescent lamp power efficiency

Output power (output LED voltage * output current / 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 is installed in the lamp will produce a very high temperature, a light effect of our LED plus than the heat, will produce higher temperature superposition.

And the life of all electronic parts in our power supply will be shortened with the increase of temperature. So efficiency is the most fundamental factor to determine the life of the power supply, efficiency can not be too low, otherwise consumed on the power of the heat is too large. Generally more than 80% on it, however, the efficiency of the lamp plate and the matching method.

10.LED fluorescent lamp power supply size

The height is the main factor limiting, generally used for T6 tube /T8 size less than or equal to 9 mm height is not too high. T10 tube height less than or equal to 15 mm. Length can be longer, more easily heat.