有源旁路二極管提高太陽能電池板的效率和性能

　　在大多數基于電池的太陽能電池板上使用的肖特基旁路二極管作為一種保護機制，使面板在其一個電池線被遮蔽或損壞時繼續產生功率。然而，傳統二極管的特性造成了能量損耗，降低了太陽能系統的整體效率，在某些情況下，實際上可能造成昂貴的損害。為了解決這個問題，一些制造商推出了一類新的“有源二極管”，利用晶體管產生二極管類似的行為，同時使他們所保護的太陽能電池板具有更高的效率和更好的可靠性。本文將探討有源二極管的基礎技術，看看目前市場上的產品，看看它們是如何改變太陽能電池板的設計和制造方式的。

　　Figure 1： Solar arrays rely on bypass diodes to protect them from damage and minimize output power losses when a section of an individual panel or a larger part of the array experiences shading due to obstructions， clouds， snow， or other phenomena. （Courtesy of STMicroelectronics.）

　　Bypass diodes provide protection

　　To understand why bypass diodes are needed， let’s look at a typical solar power system. Each string in the system is typically comprised of 10 to 20 series-connected solar modules， each with 60 to 100+ （typically 72） cells that are， similarly， all connected in series. The result is a 1，000-odd cell string， with each cell attempting to produce current in direct proportion to the amount of sunlight it sees. If any of these cells become shaded， soiled or damaged， the entire string current is limited to that which the weakest link can support. Besides being susceptible to temporary performance losses when even a single cell is shaded， an array constructed using long-series strings can introduce other， more subtle problems into a solar-electric system.