不知(zhi)道你(ni)是否和我(wo)(wo)一樣，經常混用充(chong)電(dian)線，這不有天當(dang)我(wo)(wo)向另一個AI借用他(ta)的平板充(chong)電(dian)線給我(wo)(wo)的手機充(chong)電(dian)時，他(ta)義正言辭地拒絕了！

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（過高電流有可能導(dao)致關鍵電容擊穿！）。”

嚇死人了，真的嗎？

相信(xin)經常混(hun)用(yong)充(chong)電線的人為數(shu)(shu)不少，看到這篇標題后，是否會覺得(de)心(xin)頭一(yi)緊？其實(shi)完全不用(yong)擔(dan)心(xin)。以(yi)上(shang)的“科普(pu)知識”的作(zuo)者(zhe)大(da)概并不真正懂得(de)電子知識，只(zhi)是單純依據充(chong)電器的參數(shu)(shu)，想當(dang)然地得(de)出了這樣一(yi)個錯誤的結論。

想弄清楚為什么iPad充電器可(ke)以為iPhone充電，得先真正(zheng)了解(jie)充電器的工作原理。

充電過程是怎樣的？

充電器插頭一(yi)端插在220V交(jiao)流(liu)電(dian)(dian)(dian)的(de)(de)插座上(shang)，另(ling)一(yi)端用蘋(pin)果專用的(de)(de)數據線接到(dao)iPhone/iPad上(shang)。220V交(jiao)流(liu)電(dian)(dian)(dian)先通(tong)過(guo)(guo)整流(liu)電(dian)(dian)(dian)路變(bian)(bian)成高壓直(zhi)流(liu)電(dian)(dian)(dian)，再經(jing)過(guo)(guo)開關管變(bian)(bian)成高頻(pin)高壓脈沖，然(ran)后通(tong)過(guo)(guo)變(bian)(bian)壓器轉換為(wei)低(di)(di)壓（比如5V）脈沖。5V的(de)(de)低(di)(di)壓脈沖再經(jing)過(guo)(guo)一(yi)個(ge)整流(liu)、穩壓電(dian)(dian)(dian)路，變(bian)(bian)成5V穩定的(de)(de)直(zhi)流(liu)電(dian)(dian)(dian)。在從220V交(jiao)流(liu)電(dian)(dian)(dian)變(bian)(bian)為(wei)5V直(zhi)流(liu)電(dian)(dian)(dian)的(de)(de)整個(ge)過(guo)(guo)程中，變(bian)(bian)壓器、整流(liu)電(dian)(dian)(dian)路、穩壓電(dian)(dian)(dian)路只是起到(dao)一(yi)個(ge)改變(bian)(bian)電(dian)(dian)(dian)能形態的(de)(de)作用（從高壓交(jiao)流(liu)電(dian)(dian)(dian)變(bian)(bian)為(wei)低(di)(di)壓直(zhi)流(liu)電(dian)(dian)(dian)）。

在(zai)充電(dian)這件事(shi)情上，只(zhi)有充電(dian)器可是一巴掌拍不(bu)(bu)響(xiang)的。如果穩壓電(dian)路(lu)輸出5V的一端（USB接口）沒(mei)有接上iPad或(huo)者iPhone（術語稱為負載），就(jiu)不(bu)(bu)會(hui)有電(dian)流(liu)流(liu)過，也就(jiu)不(bu)(bu)會(hui)消(xiao)耗電(dian)能。

接上負(fu)載(zai)(zai)(zai)之后，充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)才開始工作，流(liu)(liu)(liu)過(guo)充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)大小取決于負(fu)載(zai)(zai)(zai)的狀態(tai)：只要(yao)(yao)在力所能及的范圍(wei)內(nei)，負(fu)載(zai)(zai)(zai)（也就是iPad或者iPhone）需(xu)要(yao)(yao)多大的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)就提(ti)供(gong)多大的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。如(ru)果(guo)負(fu)載(zai)(zai)(zai)需(xu)要(yao)(yao)的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)超過(guo)了充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)能夠提(ti)供(gong)的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)上限，那(nei)么充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)就會(hui)一直輸出這個最(zui)大的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。這是因為(wei)，充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)內(nei)部(bu)通常(chang)會(hui)設計保護電(dian)(dian)(dian)(dian)(dian)路，一旦(dan)輸出電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)過(guo)大，就會(hui)觸(chu)發保護機制(zhi)，暫停(ting)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)輸出。

不(bu)過，蘋果公司為了讓(rang)旗下的所有充電器(qi)和數(shu)碼產(chan)品能(neng)夠盡量混用，想出了一(yi)個奇招：

仔細觀(guan)察(cha)一下(xia)USB接(jie)口，你會發(fa)現一共有四個(ge)窄金屬條，稱為(wei)四個(ge)引腳(jiao)。這(zhe)四個(ge)引腳(jiao)分別連接(jie)5V電源、GND地、D+數(shu)據線(xian)正信號和(he)D-數(shu)據線(xian)負信號。

一般(ban)兼容(rong)USB接口(kou)的充(chong)電(dian)(dian)(dian)器(qi)，D+和D-兩(liang)個(ge)(ge)引腳(jiao)是懸(xuan)空(kong)的，任何設備(bei)只要插上這(zhe)樣(yang)的充(chong)電(dian)(dian)(dian)器(qi)，就會從5V和GND兩(liang)個(ge)(ge)引腳(jiao)獲得電(dian)(dian)(dian)能。而蘋果的充(chong)電(dian)(dian)(dian)器(qi)則在D+和D-兩(liang)個(ge)(ge)數(shu)(shu)據(ju)引腳(jiao)上增加了分壓電(dian)(dian)(dian)阻，使(shi)充(chong)電(dian)(dian)(dian)的設備(bei)能夠在充(chong)電(dian)(dian)(dian)時從這(zhe)兩(liang)條數(shu)(shu)據(ju)線(xian)上讀到兩(liang)個(ge)(ge)電(dian)(dian)(dian)壓。

網(wang)絡(luo)上的(de)(de)(de)創客經過(guo)實踐證明(ming)，iPhone或者(zhe)iPod對(dui)應(ying)的(de)(de)(de)5V1A充(chong)(chong)電(dian)(dian)(dian)器(qi)，D+上的(de)(de)(de)電(dian)(dian)(dian)壓(ya)是2V，D-也(ye)是2V；而(er)iPad使用的(de)(de)(de)5V2.1A的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)器(qi)，D+電(dian)(dian)(dian)壓(ya)2.7V，D-電(dian)(dian)(dian)壓(ya)2V。當(dang)iPad或者(zhe)iPhone接上充(chong)(chong)電(dian)(dian)(dian)器(qi)時，通過(guo)這兩個引(yin)腳上不同的(de)(de)(de)電(dian)(dian)(dian)壓(ya)就可以區(qu)分當(dang)前使用的(de)(de)(de)是哪種充(chong)(chong)電(dian)(dian)(dian)器(qi)，也(ye)就能對(dui)負載(zai)做出相應(ying)的(de)(de)(de)調整，從(cong)而(er)安(an)全地充(chong)(chong)電(dian)(dian)(dian)。

呵(he)呵(he)，想蒙(meng)充電(dian)器……AI笑而不語

用iPad充(chong)電器給iPhone充(chong)電，會怎樣？

iPad和(he)iPhone充(chong)電器的(de)(de)(de)(de)設計(ji)不同是有原因的(de)(de)(de)(de)。iPhone的(de)(de)(de)(de)電池容量較(jiao)小，只(zhi)需要1A的(de)(de)(de)(de)充(chong)電電流(liu)就能在一(yi)個合理(li)的(de)(de)(de)(de)時(shi)間內完成充(chong)電。雖然更(geng)大的(de)(de)(de)(de)充(chong)電電流(liu)能大幅縮(suo)短(duan)充(chong)電時(shi)間，但(dan)會(hui)帶來(lai)更(geng)大的(de)(de)(de)(de)發(fa)熱量，而高(gao)溫(wen)是鋰電池壽(shou)命縮(suo)短(duan)的(de)(de)(de)(de)頭號殺手(shou)，所以iPhone充(chong)電器的(de)(de)(de)(de)最(zui)大輸出電流(liu)被設計(ji)為(wei)1A。

iPad的(de)(de)(de)(de)充(chong)(chong)電器(qi)上標明了5V 2.1A，指(zhi)的(de)(de)(de)(de)是iPad的(de)(de)(de)(de)充(chong)(chong)電器(qi)最大只能輸出2.1A的(de)(de)(de)(de)電流。當(dang)你用iPad的(de)(de)(de)(de)充(chong)(chong)電器(qi)給iPhone充(chong)(chong)電時，雖然iPad的(de)(de)(de)(de)充(chong)(chong)電器(qi)最大能夠提供2.1A的(de)(de)(de)(de)電流，但由于iPhone只能接受1A的(de)(de)(de)(de)電流，iPad的(de)(de)(de)(de)充(chong)(chong)電器(qi)也只好遷(qian)就它。這就好比在4車道的(de)(de)(de)(de)公路上開車，遇到收(shou)費站(zhan)(zhan)的(de)(de)(de)(de)時候(hou)，只有1個收(shou)費亭開著，那么(me)同時通過收(shou)費站(zhan)(zhan)的(de)(de)(de)(de)汽車最多也就只有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(xing)充(chong)(chong)(chong)電(dian)(dian)，由于(yu)iPhone的(de)(de)充(chong)(chong)(chong)電(dian)(dian)器(qi)最(zui)大只(zhi)能提供1A的(de)(de)電(dian)(dian)流輸出，整個(ge)充(chong)(chong)(chong)電(dian)(dian)的(de)(de)時間會(hui)是原來的(de)(de)2.1倍左(zuo)右。由于(yu)蘋果在USB接(jie)口數(shu)據引腳上(shang)耍的(de)(de)小花招，iPad知道這(zhe)是iPhone的(de)(de)充(chong)(chong)(chong)電(dian)(dian)器(qi)，也就(jiu)不會(hui)“要求”超過1A的(de)(de)充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流，并不會(hui)使(shi)iPhone充(chong)(chong)(chong)電(dian)(dian)器(qi)過載而導(dao)致損壞。

這(zhe)也好(hao)比在公(gong)路(lu)上，雖然收(shou)費站(zhan)里有4個收(shou)費亭，但是由于(yu)修路(lu)的原因，實際通車的車道只有1條，那么同時通過這(zhe)個收(shou)費站(zhan)的汽(qi)車最多仍然只有1輛。

至于這條流(liu)言最后(hou)提到的(de)(de)，過(guo)高(gao)的(de)(de)電(dian)(dian)(dian)流(liu)可能(neng)導致關鍵電(dian)(dian)(dian)容(rong)擊穿，完全邏輯不通(tong)(tong)，也說明了微(wei)博作者缺(que)乏電(dian)(dian)(dian)學(xue)物理知識(shi)。電(dian)(dian)(dian)容(rong)的(de)(de)最基本功(gong)能(neng)是(shi)“通(tong)(tong)交(jiao)流(liu)，隔直流(liu)”。充(chong)電(dian)(dian)(dian)器(qi)輸(shu)出的(de)(de)是(shi)直流(liu)電(dian)(dian)(dian)，而無(wu)論多大的(de)(de)直流(liu)電(dian)(dian)(dian)流(liu)，都(dou)是(shi)無(wu)法通(tong)(tong)過(guo)電(dian)(dian)(dian)容(rong)的(de)(de)，并不能(neng)導致電(dian)(dian)(dian)容(rong)“擊穿”。能(neng)夠(gou)擊穿電(dian)(dian)(dian)容(rong)的(de)(de)，是(shi)過(guo)高(gao)的(de)(de)直流(liu)電(dian)(dian)(dian)壓(ya)，也就是(shi)“擊穿電(dian)(dian)(dian)壓(ya)”。

所(suo)以說，用iPad充(chong)電器(qi)為iPhone充(chong)電是完全可(ke)行的，對iPhone和充(chong)電器(qi)都不(bu)(bu)會(hui)有損傷。而(er)iPhone充(chong)電器(qi)為iPad充(chong)電也可(ke)以，只(zhi)不(bu)(bu)過所(suo)需的充(chong)電時間更長。

話說回來，如果這樣交(jiao)叉充電有危險的(de)話，以(yi)蘋果公司的(de)尿性(xing)……

他們根本不會把iPad和iPhone的充(chong)電(dian)線(xian)做成一(yi)樣(yang)的啊！