AC leds could not avoid essential analysis of the constant current control technology

A, ACLED is not essentially change

that is to say, actually there is no ac electric field working mechanism of the LED chips, now available ACLED internal chip set is a kind of special arrangement device, is only the LED device of the internal structure change, of course, to do this craft level is not easy.

introduction to ACLED now most of them are quoted Seoul semiconductor released information. We can find that it is used for the traditional bridge rectifier circuit, to solve the problem of communication for the so-called dc LED power supply. Look good is to eliminate the rectifier diode, LED reverse pressure is limited, but encounter power surge rush is large, such as damage, it is not necessarily good.

it is follow the bridge rectifier circuit, so the four flows through only half bridge arm current, while the dc load flow through the entire copy of the current, caused each LED on the current distribution is uneven, such as less flows affect luminescence lumens value and luminous efficiency, such as flow to droop and impact longevity.

to solve simple also, just the LED on the dc side short circuit directly, after removal of the remaining four bridge arm current can agree. Again carefully look at the circuit, and now has become each group forward and reverse leds connected in parallel. Actually when you don't have to do is too complicated, as long as the forward and reverse parallel, communication can through positive and negative half cycle.

2, ACLED failed to avoid essential constant current control technology

from the introduction, now ACLED and often LED lighting ratio is not high enough, is said to be the stage of development, will be high. The author thinks that the similar LED light-emitting chip itself is the same, the basis of the restricted amount per watt light mainly this type rectifier bridge circuit. Think only a set of five groups LED to work, give full play to the photosynthetic efficiency, accounting for 80% of all the rest of the four groups in poor lighting owe current working status. Again how to follow the development together, also born than ordinary LED luminous efficiency is lower. Improvement in the method or reject impractical rectifier bridge road, straight forward and reverse parallel connection can all work in the best luminous efficiency.

ACLED no constant current protection function, must be an external current limiting resistor, but limited to the supply voltage on the limits of current, is going to work in normal or low voltage in less current state of low light efficiency. Current-limiting resistance is poor protection method and function not only has a defect, but also rely on energy consumption to be effective, the lower the power utilization is the energy efficiency.

want to add a PTC will solve the problem of the LED constant current, is the understanding of the performance of the component comprehensive enough. PTC is mainly used in over-current protection and thermal protection, when electricity flows through the circuit is large, PTC, Curie point temperature is reached after heat resistance is a sharp rise in close circuit, can use it to produce the degaussing circuit of colour television large current attenuation amplitude degaussing.

when PTC resistance affected by heat around the body, make it more than Curie point temperature in open state, when they can switch type thermal protection effect.

if you want to rely on PTC characteristics of positive temperature coefficient of resistance to the LED constant current protection and the thought of:

1, PTC resistance by current, to heat up and there is a process of heating time, when the resistance is not added to a high enough, probably more than current has been damaged LED.

2, PTC resistance body spontaneous hot temperature can control constant current, then the environment the influence of high and low temperature may change a few degrees will make the constant current value change is meaningless.

can by extension, is it not now usually LED device also can be so simple to constant current? It's a pity that can't. And usually ac constant current is more trouble than dc constant current.

in fact can have such as energy consumption province, constant current circuit, precise control precision, surge resistance, high reliability, small volume, low cost of adaptive grid LED constant current drive and a number of LED driver manufacturer of all kinds of excellent products. LED manufacturer and its focus on not professional circuit technology, it is better to focus in the development of low cost, high photosynthetic efficiency of LED lighting products will can meet the market's desire for more.