With the rapid development of LED technology, the annual sales of LED lighting products have sharply increased in recent years. In order to survive from fierce competitions, LED manufacturers from all over the world are striving to improve their products and meanwhile reduce the cost. There is no doubt that improving circuits for LED drives can reduce costs dramatically.
Circuits for LED drives:
Some LED lighting products need to use several decades or even hundreds of LED chips, such as LED Panels, high power LED Street Lights. Cascading these LEDs require a huge output voltage from LED drivers. If designers connect them all in parallel, LED drivers have to provide a very large output current. Connecting all LED chips in single way (either in series or in parallel) is unreasonable, which will not only restrict the number of drivers but also add to their burden. One more reasonable way is mixing these connections up, half in cascade and half in parallel. This is a simple solution which can evenly distribute voltage and current on each LED chips (if they have quite similar electronic properties). However, this is not an optimal solution, since different applications require different drive circuit designs.
Let us think about the following scenario: if one LED chip in a series branch causes short circuit due to its bad quality, no matter of kind of driver circuit this lamp used (neither constant voltage nor constant current), the current running on this series branch will increase. All LED lights chips in this branch will be easily destroyed. In most conditions, this branch will be cut off from the entire circuit. If constant voltage power suppliers are used, the output current will be dropped, with no influence on the rest circuit. But conditions will be different for constant current power suppliers. The current will remain unchanged. When one of branches are failed to work, the output current for the rest branches will be raised. LED chips can be easily destroyed under such circumstance. An effective solution for this situation is connecting LEDs in parallel. Cutting off anyone of them will not having any effect on other components. The entire circuit still can work in a normal condition.