不知道你是否和我(wo)一(yi)樣，經常混用充電(dian)(dian)線(xian)，這不有(you)天當我(wo)向另一(yi)個(ge)AI借用他(ta)的平板充電(dian)(dian)線(xian)給我(wo)的手(shou)機(ji)充電(dian)(dian)時，他(ta)義正言(yan)辭地拒絕(jue)了(le)！

還跟我“科普”道：在非快充模式下，雖然兩種充電線長得一樣，電壓都是5V，但iPhone的充電電流是1A，而iPad卻是2.1A，根據P=UI可得iPhone充電器的功率為5W，而iPad為10.2W。這樣做的后果是既傷iPhone又傷iPad 充電器（過高電流有可能(neng)導致(zhi)關鍵(jian)電容擊穿！）。”

嚇死人了，真的嗎？

相信經常混用(yong)充電線的(de)人為數不少(shao)，看到這篇標題后(hou)，是(shi)否會覺(jue)得(de)(de)心(xin)頭(tou)一(yi)(yi)緊？其實完全不用(yong)擔心(xin)。以上的(de)“科普知識(shi)”的(de)作者大概并(bing)不真(zhen)正懂得(de)(de)電子知識(shi)，只是(shi)單純依據充電器的(de)參數，想當(dang)然(ran)地得(de)(de)出了這樣一(yi)(yi)個錯(cuo)誤的(de)結論。

想弄清楚為(wei)什么iPad充電器(qi)可(ke)以為(wei)iPhone充電，得(de)先(xian)真正了解充電器(qi)的(de)工作原理。

充電過程是怎樣的？

充電器插頭一端(duan)插在220V交流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)的(de)(de)插座上，另一端(duan)用蘋果專用的(de)(de)數據線(xian)接到(dao)(dao)iPhone/iPad上。220V交流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)先通過(guo)(guo)整流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)路(lu)變(bian)(bian)(bian)成高(gao)壓(ya)(ya)直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)，再經(jing)過(guo)(guo)開關(guan)管變(bian)(bian)(bian)成高(gao)頻高(gao)壓(ya)(ya)脈沖，然后通過(guo)(guo)變(bian)(bian)(bian)壓(ya)(ya)器轉(zhuan)換(huan)為低壓(ya)(ya)（比如5V）脈沖。5V的(de)(de)低壓(ya)(ya)脈沖再經(jing)過(guo)(guo)一個整流(liu)(liu)(liu)(liu)、穩壓(ya)(ya)電(dian)(dian)(dian)路(lu)，變(bian)(bian)(bian)成5V穩定的(de)(de)直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)。在從(cong)220V交流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)變(bian)(bian)(bian)為5V直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)的(de)(de)整個過(guo)(guo)程中(zhong)，變(bian)(bian)(bian)壓(ya)(ya)器、整流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)路(lu)、穩壓(ya)(ya)電(dian)(dian)(dian)路(lu)只是起到(dao)(dao)一個改(gai)變(bian)(bian)(bian)電(dian)(dian)(dian)能形態的(de)(de)作用（從(cong)高(gao)壓(ya)(ya)交流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)變(bian)(bian)(bian)為低壓(ya)(ya)直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)）。

在(zai)充電(dian)(dian)(dian)(dian)這件事情上，只有(you)充電(dian)(dian)(dian)(dian)器可是(shi)一巴掌拍不(bu)響的。如果穩壓(ya)電(dian)(dian)(dian)(dian)路輸出5V的一端（USB接口(kou)）沒(mei)有(you)接上iPad或者(zhe)iPhone（術(shu)語稱為負(fu)載），就(jiu)不(bu)會有(you)電(dian)(dian)(dian)(dian)流流過(guo)，也就(jiu)不(bu)會消耗電(dian)(dian)(dian)(dian)能。

接上負(fu)載(zai)之后，充電(dian)(dian)(dian)(dian)器(qi)才開始工作，流(liu)(liu)過充電(dian)(dian)(dian)(dian)器(qi)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)大(da)小(xiao)取(qu)決(jue)于負(fu)載(zai)的(de)狀態：只(zhi)要在力(li)所能及的(de)范(fan)圍內，負(fu)載(zai)（也(ye)就(jiu)是iPad或者iPhone）需(xu)要多(duo)大(da)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)，充電(dian)(dian)(dian)(dian)器(qi)就(jiu)提供(gong)多(duo)大(da)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)。如果(guo)負(fu)載(zai)需(xu)要的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)超過了(le)充電(dian)(dian)(dian)(dian)器(qi)能夠提供(gong)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)上限，那么充電(dian)(dian)(dian)(dian)器(qi)就(jiu)會(hui)一(yi)直輸出這個(ge)最大(da)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)。這是因為，充電(dian)(dian)(dian)(dian)器(qi)內部通(tong)常會(hui)設(she)計保護電(dian)(dian)(dian)(dian)路，一(yi)旦輸出電(dian)(dian)(dian)(dian)流(liu)(liu)過大(da)，就(jiu)會(hui)觸發保護機制，暫停電(dian)(dian)(dian)(dian)流(liu)(liu)輸出。

不(bu)過，蘋果(guo)公司為了(le)讓旗下的所(suo)有充電器和數碼產品能夠(gou)盡量(liang)混用，想出(chu)了(le)一個(ge)奇招：

仔細觀察(cha)一(yi)下USB接(jie)口，你會發現一(yi)共有(you)四個(ge)窄金屬條，稱為四個(ge)引腳。這四個(ge)引腳分別(bie)連接(jie)5V電源、GND地、D+數據線正信號和D-數據線負信號。

一般兼容(rong)USB接口的(de)(de)充(chong)(chong)電(dian)(dian)(dian)器(qi)，D+和(he)D-兩(liang)個(ge)引(yin)腳(jiao)是懸(xuan)空的(de)(de)，任何設備(bei)只(zhi)要插(cha)上(shang)這樣(yang)的(de)(de)充(chong)(chong)電(dian)(dian)(dian)器(qi)，就(jiu)會從(cong)5V和(he)GND兩(liang)個(ge)引(yin)腳(jiao)獲得(de)電(dian)(dian)(dian)能。而蘋果的(de)(de)充(chong)(chong)電(dian)(dian)(dian)器(qi)則在D+和(he)D-兩(liang)個(ge)數(shu)據(ju)引(yin)腳(jiao)上(shang)增(zeng)加(jia)了分壓電(dian)(dian)(dian)阻(zu)，使充(chong)(chong)電(dian)(dian)(dian)的(de)(de)設備(bei)能夠(gou)在充(chong)(chong)電(dian)(dian)(dian)時從(cong)這兩(liang)條數(shu)據(ju)線上(shang)讀到兩(liang)個(ge)電(dian)(dian)(dian)壓。

網絡上(shang)(shang)的創客經過實踐證明，iPhone或者(zhe)iPod對(dui)應的5V1A充(chong)電(dian)(dian)(dian)(dian)(dian)器，D+上(shang)(shang)的電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)是2V，D-也是2V；而iPad使用(yong)的5V2.1A的充(chong)電(dian)(dian)(dian)(dian)(dian)器，D+電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)2.7V，D-電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)2V。當iPad或者(zhe)iPhone接上(shang)(shang)充(chong)電(dian)(dian)(dian)(dian)(dian)器時，通過這兩個(ge)引腳上(shang)(shang)不同的電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)就(jiu)可以(yi)區分當前(qian)使用(yong)的是哪種充(chong)電(dian)(dian)(dian)(dian)(dian)器，也就(jiu)能對(dui)負載(zai)做(zuo)出(chu)相應的調(diao)整，從而安全地充(chong)電(dian)(dian)(dian)(dian)(dian)。

呵(he)呵(he)，想(xiang)蒙充電(dian)器……AI笑(xiao)而不語

用iPad充電器給iPhone充電，會怎樣？

iPad和iPhone充(chong)電(dian)(dian)(dian)器的(de)(de)(de)設計不同是有原因的(de)(de)(de)。iPhone的(de)(de)(de)電(dian)(dian)(dian)池容量較小，只需要1A的(de)(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)就能在一個合理的(de)(de)(de)時(shi)間內完(wan)成充(chong)電(dian)(dian)(dian)。雖(sui)然更大(da)的(de)(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)能大(da)幅縮短(duan)充(chong)電(dian)(dian)(dian)時(shi)間，但會帶來更大(da)的(de)(de)(de)發(fa)熱量，而(er)高溫是鋰電(dian)(dian)(dian)池壽命縮短(duan)的(de)(de)(de)頭號殺手，所以(yi)iPhone充(chong)電(dian)(dian)(dian)器的(de)(de)(de)最大(da)輸(shu)出(chu)電(dian)(dian)(dian)流(liu)(liu)被設計為1A。

iPad的(de)充(chong)(chong)(chong)電(dian)(dian)器上(shang)標明了5V 2.1A，指(zhi)的(de)是iPad的(de)充(chong)(chong)(chong)電(dian)(dian)器最(zui)大只能(neng)輸(shu)出(chu)2.1A的(de)電(dian)(dian)流。當(dang)你用iPad的(de)充(chong)(chong)(chong)電(dian)(dian)器給iPhone充(chong)(chong)(chong)電(dian)(dian)時(shi)(shi)，雖然iPad的(de)充(chong)(chong)(chong)電(dian)(dian)器最(zui)大能(neng)夠提(ti)供2.1A的(de)電(dian)(dian)流，但由于iPhone只能(neng)接受1A的(de)電(dian)(dian)流，iPad的(de)充(chong)(chong)(chong)電(dian)(dian)器也只好遷就(jiu)它。這就(jiu)好比在4車道的(de)公路(lu)上(shang)開(kai)車，遇(yu)到(dao)收(shou)費(fei)站(zhan)的(de)時(shi)(shi)候，只有1個收(shou)費(fei)亭開(kai)著，那么(me)同(tong)時(shi)(shi)通過收(shou)費(fei)站(zhan)的(de)汽車最(zui)多(duo)也就(jiu)只有1輛。

iPad的電池設計成充電電流為2.1A時充電時間最合適。如果用iPhone的電池充電器給iPad進行充(chong)電，由于(yu)iPhone的(de)充(chong)電器最大(da)只能提供1A的(de)電流輸(shu)出，整個充(chong)電的(de)時(shi)間會(hui)是原(yuan)來的(de)2.1倍(bei)左右。由于(yu)蘋果在USB接口數據引腳上耍的(de)小(xiao)花招(zhao)，iPad知(zhi)道這是iPhone的(de)充(chong)電器，也就不(bu)會(hui)“要求”超過1A的(de)充(chong)電電流，并不(bu)會(hui)使iPhone充(chong)電器過載而導(dao)致損壞。

這(zhe)也(ye)好(hao)比在公路(lu)上，雖然(ran)收費站里(li)有(you)4個收費亭，但是由于修(xiu)路(lu)的原因，實(shi)際通車的車道只有(you)1條，那么同時通過這(zhe)個收費站的汽(qi)車最多仍(reng)然(ran)只有(you)1輛。

至于這條流(liu)(liu)(liu)(liu)言最后(hou)提到(dao)的(de)，過(guo)高的(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)可(ke)能導致關(guan)鍵電(dian)(dian)(dian)容(rong)(rong)擊(ji)穿(chuan)，完(wan)全邏輯不(bu)通，也說明(ming)了微博作(zuo)者缺乏電(dian)(dian)(dian)學物理知識。電(dian)(dian)(dian)容(rong)(rong)的(de)最基本(ben)功能是“通交流(liu)(liu)(liu)(liu)，隔直(zhi)(zhi)流(liu)(liu)(liu)(liu)”。充電(dian)(dian)(dian)器輸出的(de)是直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)，而(er)無論多(duo)大的(de)直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)，都(dou)是無法通過(guo)電(dian)(dian)(dian)容(rong)(rong)的(de)，并(bing)不(bu)能導致電(dian)(dian)(dian)容(rong)(rong)“擊(ji)穿(chuan)”。能夠擊(ji)穿(chuan)電(dian)(dian)(dian)容(rong)(rong)的(de)，是過(guo)高的(de)直(zhi)(zhi)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)壓，也就是“擊(ji)穿(chuan)電(dian)(dian)(dian)壓”。

所以說，用(yong)iPad充(chong)(chong)(chong)電(dian)器(qi)為(wei)(wei)iPhone充(chong)(chong)(chong)電(dian)是(shi)完(wan)全可行(xing)的，對iPhone和充(chong)(chong)(chong)電(dian)器(qi)都(dou)不會有損(sun)傷。而iPhone充(chong)(chong)(chong)電(dian)器(qi)為(wei)(wei)iPad充(chong)(chong)(chong)電(dian)也可以，只不過(guo)所需的充(chong)(chong)(chong)電(dian)時(shi)間(jian)更長。

話(hua)說(shuo)回(hui)來，如果這樣交叉(cha)充(chong)電有(you)危(wei)險的話(hua)，以蘋(pin)果公司的尿(niao)性……

他們根本不會把iPad和iPhone的充電(dian)線做成一樣(yang)的啊！