功率因數(shù)校正在能量收集系統(tǒng)中最大化功率效率和質(zhì)量

　　在任何配電系統(tǒng)中，非電阻性負(fù)載會(huì)使電流和電壓發(fā)生相位偏移，導(dǎo)致無(wú)功功率損失。當(dāng)電流和電壓在純電阻性負(fù)載的情況下保持相位時(shí)，感性負(fù)載存儲(chǔ)無(wú)功功率并導(dǎo)致電流滯后電壓，而容性負(fù)載導(dǎo)致電流導(dǎo)通電壓。當(dāng)電流波形不跟隨電壓波形時(shí)，不僅失去功率，而且產(chǎn)生的諧波可以通過(guò)配電系統(tǒng)傳播，破壞其他連接的設(shè)備。

　　當(dāng)電流和電壓波形靠近時(shí)，所有的功率都包含在基波頻率中，諧波降到零。功率因數(shù)校正（PFC）的工作，以控制電流，以配合電壓的形狀和相位，最大限度地提高實(shí)際電源可從源有效地轉(zhuǎn)換負(fù)載到一個(gè)純粹的電阻之一。

　　在微觀層面上，功率因數(shù)校正為能量收集電路的設(shè)計(jì)者提供了直接的好處。用于從環(huán)境中獲取能量的功率調(diào)節(jié)電路通常會(huì)產(chǎn)生電流輸出中的諧波，從而導(dǎo)致功率損耗。在這種情況下，線性穩(wěn)壓器的使用會(huì)導(dǎo)致在最佳操作包絡(luò)外工作時(shí)的效率降低，而開(kāi)關(guān)穩(wěn)壓器的使用可能會(huì)帶來(lái)額外的設(shè)計(jì)挑戰(zhàn)，以解決可能限制最佳功率輸出的穩(wěn)定性問(wèn)題。PFC電路是為應(yīng)對(duì)這些挑戰(zhàn)而設(shè)計(jì)的。

　　As a result， power factor correction （PFC） plays a critical role in maximizing real power and maintaining its quality. The simplest way to control the harmonic current is to use a filter that passes current only at line frequency. This filter reduces the harmonic current， which means that the nonlinear device now looks like a linear load. At this point， the power factor can be brought to near unity using capacitors or inductors as required. This filter requires large-value， high-current inductors， which are bulky and can be expensive.

　　Unlike passive PFC methods， active methods achieve PFC with minimal component count and cost. Drawing on a wide selection of integrated devices， designers can easily implement PFC in energy-harvesting applications using ICs from manufacturers including Cirrus Logic，F(xiàn)reescale Semiconductor， Fremont Micro Devices， Linear Technology， ON Semiconductor， Renesas， STMicroelectronics， Texas Instruments， and Toshiba， among others.