平衡低亮度led系統(tǒng)的復(fù)雜性、效率和成本

　　固態(tài)照明占據(jù)了頭條新聞。然而，低功耗LED仍然是該部門的工作母機(jī)，功能從簡單的指示燈用于便攜式設(shè)備的背光顯示。雖然這種LED設(shè)備已經(jīng)很好地建立，開發(fā)適銷對路的產(chǎn)品需要徹底了解技術(shù)和所涉及的權(quán)衡。

　　該系統(tǒng)的一個(gè)重要組成部分是驅(qū)動(dòng)電路。權(quán)衡影響決定使用一個(gè)簡單的電阻電源，線性穩(wěn)壓器，或額外的復(fù)雜的開關(guān)穩(wěn)壓器（見圖1）。

　　Figure 1： Used with an adjustable power supply， the BCR 320 family of linear regulators can drive 0.5-W LEDs with a power dissipation of just 1 W. （Image courtesy of Infineon）。

　　The optimal driver circuitry choice depends on the requirements—and balancing the design complexity， efficiency， and cost.

　　Basic current， light， and cooling needs

　　By definition， LEDs are light emitting diodes. That is， the current into the LED must be regulated to avoid failure. One popular technique to regulate current is to design a resistor into the driver. The LED driver also controls both LED output quality and luminous flux—and extends the life of the system.

　　Temperature management is also vital to consistent color and lighting because output wavelength varies with temperature. Also， as with most electronics， elevated temperature reduces life expectancy. Incandescent bulbs radiate heat off of the glass bulb， but LEDs generate most of their heat off the back side of the chip， limiting cooling options to less efficient conductive cooling. As a result， designing drivers for low heat dissipation is important not just for high-efficiency applications， but also for those requiring extreme reliability.