積極尋求更好的ORing解決方案

　　有源ORing提供顯著的好處在肖特基二極管的MOSFET，但它強加一些設(shè)計參數(shù)，工程師需要了解為了開發(fā)出最合適的解決方案

　　利用二極管主動組合多個或冗余電源是一項跨越半導(dǎo)體工業(yè)歷史的技術(shù)，因為二極管是當(dāng)今使用的最簡單和最有用的半導(dǎo)體之一。然而，由于正向偏置pn結(jié)的“撬棍”效應(yīng)，它的簡單性也在這一類應(yīng)用中失敗了。雖然現(xiàn)在有一系列不同的開關(guān)特性，選擇二極管，如功率肖特基二極管，基本功能是“開”或“關(guān)”，與一個半導(dǎo)體結(jié)的主要好處：控制。由于二極管pn結(jié)的基本物理特性，它們通過的電流越多，耗散的功率就越大。

　　用較先進的場效應(yīng)晶體管取代不起眼的二極管降低了功耗，并引入了二極管無法控制的水平，但也有其后果。了解這些后果使半導(dǎo)體產(chǎn)業(yè)發(fā)展的一系列控制解決方案的拓撲結(jié)構(gòu)采用有源ORing MOSFET。

　　Active ORing is now commonplace in power supply design， but is most relevant in applications that must match the needs of delivering significant levels of power with a high degree of ruggedness and reliability. Today， that typically points towards telecommunications， but it is equally valid in other applications where load sharing/balancing between power supplies is implemented， or where so-called ‘N+1’ redundancy is required.

　　Conceptually， replacing diodes with MOSFETs is relatively straightforward and brings instant benefits in terms of reliability. The power dissipated by a diode when it is conducting is significant and proportional to the current passing through it， so in high power applications， the diodes tend to dissipate higher power. In turn， this demands the use of larger diodes and heat sinks， or other cooling solutions such as forced air or convection. Wherever cooling becomes necessary， it represents a potential point of failure. So， as the heat dissipated by diodes increases， so too does the risk of failure. It is widely accepted that despite the efforts to lower the active power consumption of integrated devices， the power demand trend of today‘s applications is only increasing， thereby demanding ever more powerful power supplies and， in turn， larger diodes with their associated heat dissipation issues.