為LED串提供高電壓

　　發(fā)光二極管是電流驅(qū)動(dòng)元件與適度的電壓降-低于2 V -那么為什么你需要擔(dān)心高電壓源時(shí)，供應(yīng)LED？LED是電流驅(qū)動(dòng)的設(shè)備，和一個(gè)單獨(dú)的LED需要20和50 mA的電流，而高亮度LED（HB LED）可能需要100毫安或以上。高電壓是必要的，因?yàn)長(zhǎng)ED往往串聯(lián)，并聯(lián)，串聯(lián)/并聯(lián)陣列（圖1），和串串的LED將需要一個(gè)電壓源，是在一個(gè)稍高的電位比他們的個(gè)別二極管下降的總和。

　　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）.