升壓和開(kāi)關(guān)穩(wěn)壓器驅(qū)動(dòng)高亮度LED

　　在這三部分關(guān)于發(fā)光二極管（LED）驅(qū)動(dòng)程序的第一部分中，我們討論了降壓型升壓開(kāi)關(guān)穩(wěn)壓器、開(kāi)關(guān)電容變換器和反激變換器。該系列產(chǎn)品首先從低亮度LED系統(tǒng)的復(fù)雜性、效率和成本平衡入手，并繼續(xù)使用降壓調(diào)節(jié)器驅(qū)動(dòng)高亮度LED。最后一部分是關(guān)于駕駛性能。

　　從LED獲得最佳性能需要正確的驅(qū)動(dòng)程序。線性穩(wěn)壓器為低功率LED提供了一種簡(jiǎn)單而經(jīng)濟(jì)的解決方案。然而，它們將系統(tǒng)功率的很大一部分消耗在熱量上，使它們成為大功率LED的一個(gè)不良選擇。開(kāi)關(guān)穩(wěn)壓器提供了更有效的解決方案。降壓（降壓）開(kāi)關(guān)穩(wěn)壓器是一個(gè)很好的開(kāi)始，但只有當(dāng)LED驅(qū)動(dòng)電壓低于電源。當(dāng)LED需要更高或不同的電壓時(shí)，升壓（升壓）或降壓開(kāi)關(guān)穩(wěn)壓器提供更好的選擇。

　　發(fā)光二極管的光輸出隨電壓的變化呈非線性變化。更復(fù)雜的是，正向電壓（VF）也隨著溫度和年齡的增加而漂移。幸運(yùn)的是，LED輸出與電流近似線性。恒流驅(qū)動(dòng)程序提供最好的結(jié)果，尤其是在當(dāng)前匹配能力增強(qiáng)的情況下。

　　LEDs can be linked together in series or in parallel， but neither configuration is always better. The best choice varies from case to case， depending on the parameters of the devices and the needs of the application. When wired in series， LEDs in a string continue to operate even if one or more fail by short circuiting. The series configuration also provides current matching， which ensures consistent output. On the downside， series connections require higher voltages， which limit driver options and increases regulatory requirements. Also if an LED fails open， the entire string goes dark.

　　The alternative， parallel configuration operates with lower voltages. However， it does not provide current matching， which is important to consider， given the random device-to-device variation among LEDs that can cause inconsistent light output between LEDs.