为LED串提供高电压

　　为LED串提供高电压

　　发光二极管是电流驱动元件与适度的电压降-低于2 V -那么为什么你需要担心高电压源时，供应LED？LED是电流驱动的设备，和一个单独的LED需要20和50 mA的电流，而高亮度LED（HB LED）可能需要100毫安或以上。高电压是必要的，因为LED往往串联，并联，串联/并联阵列（图1），和串串的LED将需要一个电压源，是在一个稍高的电位比他们的个别二极管下降的总和。

　　Figure 1： An array of multiple LEDs can be wired in many combinations of series， parallel， and series/parallel configurations; each configuration brings trade-offs in voltage and current requirements， current and color balance， and impact of short-circuit or open-mode LED failure.

　　Why not just drive the LEDs directly from a low-voltage current source？ There are several reasons：

　　If you have multiple LEDs in parallel， you would need a driver for each LED; alternatively， if you use a single source directly shared by all， then the current through each LED would differ depending on its individual characteristics， so the output intensity of each LED would differ from its neighbors.

　　In contrast， when a single driver is used for LEDs all wired in parallel， the driver needs to be a low-voltage， higher-current source， but such sources tend to be inefficient in DC/DC conversion compared to higher-voltage ones， and high-current IR loss also degrades efficiency.

　　By wiring the LEDs in a series string， the current through each LED will be identical. This helps ensure uniform illumination but does not guarantee it （there are other factors involved， as well）.