談起想必大家都比較熟悉了，作為主流的快充協議，USB PD協議可最高實現100W的充電功率。無論是高電壓低電流充電模式還是高電流低電壓充電模式，充電速度有多塊，本質還是看充電的功率有的大。很多體驗過pd快充的人，給出的體驗反饋就是感覺真的是充電飛快，但是細心的人也發現當充電沖到85%之后，充電速度便會下降。85%之后的這段充電耗時，占據了近整個充滿時長的三分之一。這讓大家開始疑惑，為什么Pd快充開始充電飛快，快充滿時速度卻下降了呢？

其實(shi)這是pd快(kuai)(kuai)充(chong)(chong)(chong)(chong)的(de)(de)一種防止過(guo)充(chong)(chong)(chong)(chong)保(bao)護功(gong)能(neng)，我們把(ba)整個(ge)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程分為(wei)(wei)三個(ge)階(jie)(jie)段(duan)(duan)(duan)，分別(bie)是預(yu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)階(jie)(jie)段(duan)(duan)(duan)、快(kuai)(kuai)充(chong)(chong)(chong)(chong)階(jie)(jie)段(duan)(duan)(duan)以(yi)及(ji)恒壓充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)階(jie)(jie)段(duan)(duan)(duan)。在預(yu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)階(jie)(jie)段(duan)(duan)(duan)，始(shi)終處于供電(dian)(dian)(dian)(dian)(dian)(dian)階(jie)(jie)段(duan)(duan)(duan)的(de)(de)鋰電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)開始(shi)減少供電(dian)(dian)(dian)(dian)(dian)(dian)，恢復自身狀態為(wei)(wei)接下(xia)來的(de)(de)快(kuai)(kuai)充(chong)(chong)(chong)(chong)階(jie)(jie)段(duan)(duan)(duan)做準備。之(zhi)后(hou)進(jin)(jin)入(ru)快(kuai)(kuai)充(chong)(chong)(chong)(chong)階(jie)(jie)段(duan)(duan)(duan)，pd快(kuai)(kuai)充(chong)(chong)(chong)(chong)自身的(de)(de)快(kuai)(kuai)充(chong)(chong)(chong)(chong)協議智能(neng)匹配(pei)最適合的(de)(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)模式(shi)進(jin)(jin)行快(kuai)(kuai)充(chong)(chong)(chong)(chong)。最后(hou)當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進(jin)(jin)入(ru)85%之(zhi)后(hou)快(kuai)(kuai)充(chong)(chong)(chong)(chong)滿的(de)(de)時候，pd快(kuai)(kuai)充(chong)(chong)(chong)(chong)開始(shi)把(ba)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓穩(wen)定，然后(hou)開始(shi)減少充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流，直到電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)滿。這樣在充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)結束階(jie)(jie)段(duan)(duan)(duan)進(jin)(jin)入(ru)恒壓低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)模式(shi)有助(zhu)于降低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)損耗(hao)，延長電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)壽命。

雖然如(ru)果不進(jin)入恒壓(ya)充(chong)(chong)(chong)(chong)電(dian)(dian)階段，一(yi)般(ban)(ban)電(dian)(dian)子設備內(nei)部(bu)都會有(you)(you)相應的(de)保(bao)護板或者保(bao)護電(dian)(dian)阻用來一(yi)定程度(du)上緩(huan)解過充(chong)(chong)(chong)(chong)帶來的(de)危害，但(dan)是這(zhe)種保(bao)護裝置是有(you)(you)壽命的(de)，長(chang)期(qi)如(ru)此不但(dan)會損(sun)壞色被內(nei)部(bu)，也會損(sun)傷電(dian)(dian)池。其實一(yi)般(ban)(ban)的(de)正規充(chong)(chong)(chong)(chong)電(dian)(dian)器也是具備這(zhe)種恒壓(ya)充(chong)(chong)(chong)(chong)電(dian)(dian)保(bao)護的(de)，但(dan)是由于充(chong)(chong)(chong)(chong)電(dian)(dian)速(su)度(du)本身比(bi)(bi)較(jiao)慢(man)，所以感覺(jue)不到什么(me)明(ming)顯(xian)(xian)變(bian)化。而pd快(kuai)充(chong)(chong)(chong)(chong)的(de)充(chong)(chong)(chong)(chong)電(dian)(dian)速(su)度(du)比(bi)(bi)較(jiao)快(kuai)，就讓人感覺(jue)變(bian)化比(bi)(bi)較(jiao)明(ming)顯(xian)(xian)罷了。