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LED lighting drive solution selection
In the design of LED lighting, there are two kinds of driving schemes: linear drive and switch type drive.
Linear drive application is one of the most simple and the most direct drive applications. In the application of white LED lighting level, although there are many problems, such as low efficiency, poor adjustment and so on, but because of its simple circuit, small size, can meet some specific occasions more applications.
And switch mode driver can obtain good current control accuracy and higher overall efficiency, the main application is divided into two categories of the buck and boost. Buck switch driver is for the power supply voltage is higher than the LED of the terminal voltage or the use of multiple LED parallel driver. Boost switch driver is for the power supply voltage is lower than the LED of the terminal voltage or the use of multiple LED series driver.
It is generally believed that the isolation type drive safety, but the efficiency is low, the non isolation type drive efficiency is higher, should be based on the actual use of the requirements to choose.
At present, the design of the basic LED driver lighting applications is relatively simple, but if you still need other features such as phase control dimming and power factor correction (PFC), the design becomes complex. The non dimming LED driver without power factor correction function usually contains an off-line switching power supply, which is used to adjust the output under constant current.
The back end of the LED driver contains a current regulation circuit with a short circuit protection function. The linear regulator circuit can be used to achieve this goal, however, this method is inefficient, so it is suitable for low output current, which is usually not applied to multi level architecture. Alternative is to use a simple, with a current feedback voltage regulator circuit, in order to limit the output current exceeds the desired LED drive current. The variation of the total LED forward voltage with the temperature and the tolerance of the device is offset, and the current is limited by the occurrence of short circuit or other fault conditions, thereby protecting the driver from damage.