First, AC LED is not a fundamental change in the device
That is to say, there is actually no LED chip for the working mechanism of the alternating electric field. The AC LED that is now available is a special arrangement of internal chip sets, which is only a change in the internal structure of the LED device. Of course, this level of technology is required. Not easy.
Most of the introductions to AC LEDs are quoted from Seoul Semiconductor . It can be seen that it uses the traditional rectifier bridge circuit to solve the problem of AC to the so-called DC Led Power Supply. It seems that the advantage is that the rectifier diode is omitted, but the reverse voltage withstand voltage of the LED is limited. If the surge peak of the power grid is large, it will not be beneficial.
Because it is a simulated rectifier bridge circuit, only half of the current flows through the four bridge arms, and the DC load terminal flows through the entire current, causing the current distribution on each group of LEDs to be quite uneven. For example, the undercurrent will affect the luminous lumen value. And luminous efficiency, such as overcurrent, causes light decay and affects life.
To solve the problem is also simple, just remove the DC terminal directly after the short circuit, the remaining four bridge arm current can be consistent. Looking closely at the circuit, it has now become a parallel connection of the forward and reverse LEDs of each group. In fact, it didn't have to be too complicated in the first place. As long as the forward and reverse parallels, the exchange can pass both positive and negative for half a week.
Second, AC LED can not avoid the essential constant current control technology
From the introduction, the current LED LED light efficiency is not high enough compared with the usual LED. It is said to be the development stage and will be higher in the future. The author believes that the basis of the same kind of LED chip itself is the same, and the main limitation of the wattage per watt is the rectifier bridge circuit type. Imagine that only one of the five groups of LEDs can work normally, and the light effect is fully utilized. The remaining four groups of 80% work in the under-current state with poor light efficiency. How to develop along with it, it is also inherently better than the ordinary LED's luminous efficiency. The method of improvement is to abandon the unusable rectifier bridge, and the direct forward and reverse parallel connections can all work in the state with the best luminous efficiency.
There is no constant current protection function in the AC LED. When using it, an external current limiting resistor must be connected. However, when the current is limited to the upper limit of the Power Supply voltage, it will work in the low light efficiency state of undercurrent at normal or low voltage. Resistor current limiting is a poor protection method. It not only has functional defects, but also relies on energy consumption to make the power utilization rate lower.
If you want to add a PTC to solve the LED constant current problem, it is not comprehensive enough to understand the performance of the component. The PTC is mainly used in overcurrent protection and thermal protection. When the current in the circuit is too large and the PTC reaches the Curie point temperature after heating, the resistance value rises sharply and approaches the open circuit. The degaussing circuit in the color TV uses it to generate a large current attenuation amplitude. Degaussing.
Dimmable Class 2 Led Driver is the most compact 12V/24V DC Dimmable Led Driver on the market with UL 8750 listed. The series led driver is class 2 rated and designed to operate with any standard MLV/Incandescent TRIAC (Leading edge) dimmer switch. Encased in a low profile coated metal box that includes 2 knock-outs, one on each side, to enable easy installation that complies with electrical code requirements.
Dimmable Class 2 Led Driver
Waterproof Led Driver,Led Driver Zf120A,75W Dimmable Led Driver,Led Driver Dimmer 220V
Shenzhenshi Zhenhuan Electronic Co Ltd , http://www.szzhpower.com