混用iPad的充電器為iPhone充電
不(bu)知道你是否和我(wo)一(yi)樣,經常(chang)混用充(chong)電線,這不(bu)有天當我(wo)向另一(yi)個AI借用他的(de)平板充(chong)電線給我(wo)的(de)手機(ji)充(chong)電時,他義正(zheng)言辭(ci)地拒絕(jue)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(zhi)關鍵電容擊穿!)。”
嚇死人了,真的嗎?
相(xiang)信經常混(hun)用(yong)充(chong)電(dian)線(xian)的人為數(shu)不少,看到這(zhe)篇(pian)標(biao)題后,是(shi)否會覺(jue)得(de)心(xin)頭一緊(jin)?其實完全不用(yong)擔心(xin)。以上的“科普知(zhi)識(shi)”的作者大概并不真正懂(dong)得(de)電(dian)子知(zhi)識(shi),只是(shi)單純依據充(chong)電(dian)器的參(can)數(shu),想當然地得(de)出了這(zhe)樣(yang)一個錯(cuo)誤的結論。
想弄清(qing)楚為(wei)(wei)什(shen)么(me)iPad充電器(qi)可以為(wei)(wei)iPhone充電,得先真正了(le)解充電器(qi)的工(gong)作原(yuan)理(li)。
充電過程是怎樣的?
充電器插(cha)頭一端(duan)插(cha)在(zai)220V交(jiao)流(liu)(liu)電(dian)(dian)(dian)的(de)插(cha)座上,另一端(duan)用蘋果專用的(de)數據線接(jie)到iPhone/iPad上。220V交(jiao)流(liu)(liu)電(dian)(dian)(dian)先通(tong)過(guo)(guo)整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路變(bian)(bian)(bian)成高壓(ya)(ya)直流(liu)(liu)電(dian)(dian)(dian),再(zai)經過(guo)(guo)開關管變(bian)(bian)(bian)成高頻高壓(ya)(ya)脈(mo)(mo)沖,然后通(tong)過(guo)(guo)變(bian)(bian)(bian)壓(ya)(ya)器轉(zhuan)換為低(di)壓(ya)(ya)(比如(ru)5V)脈(mo)(mo)沖。5V的(de)低(di)壓(ya)(ya)脈(mo)(mo)沖再(zai)經過(guo)(guo)一個(ge)整(zheng)(zheng)流(liu)(liu)、穩(wen)壓(ya)(ya)電(dian)(dian)(dian)路,變(bian)(bian)(bian)成5V穩(wen)定(ding)的(de)直流(liu)(liu)電(dian)(dian)(dian)。在(zai)從220V交(jiao)流(liu)(liu)電(dian)(dian)(dian)變(bian)(bian)(bian)為5V直流(liu)(liu)電(dian)(dian)(dian)的(de)整(zheng)(zheng)個(ge)過(guo)(guo)程中,變(bian)(bian)(bian)壓(ya)(ya)器、整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路、穩(wen)壓(ya)(ya)電(dian)(dian)(dian)路只是起到一個(ge)改變(bian)(bian)(bian)電(dian)(dian)(dian)能(neng)形態的(de)作用(從高壓(ya)(ya)交(jiao)流(liu)(liu)電(dian)(dian)(dian)變(bian)(bian)(bian)為低(di)壓(ya)(ya)直流(liu)(liu)電(dian)(dian)(dian))。
在充(chong)電(dian)這件事情(qing)上(shang),只有充(chong)電(dian)器可是一巴掌拍不響的。如果穩壓電(dian)路輸出(chu)5V的一端(USB接口)沒有接上(shang)iPad或者iPhone(術(shu)語(yu)稱為負載),就不會有電(dian)流流過,也就不會消耗電(dian)能。
接上負(fu)載(zai)之后(hou),充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)才開(kai)始工作,流(liu)(liu)(liu)(liu)過充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)的(de)(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)大小取(qu)決于負(fu)載(zai)的(de)(de)狀態:只要在力所能及的(de)(de)范圍內,負(fu)載(zai)(也就是iPad或者iPhone)需要多(duo)大的(de)(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu),充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)就提供多(duo)大的(de)(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)。如(ru)果負(fu)載(zai)需要的(de)(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)超過了充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)能夠(gou)提供的(de)(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)上限,那么(me)充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)就會一直輸(shu)出這(zhe)個最大的(de)(de)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)。這(zhe)是因(yin)為,充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)內部通(tong)常(chang)會設計保(bao)(bao)護(hu)電(dian)(dian)(dian)路,一旦輸(shu)出電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)過大,就會觸發保(bao)(bao)護(hu)機制(zhi),暫(zan)停電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)輸(shu)出。
不過,蘋果(guo)公司為了讓旗下的所有充電器和數(shu)碼產品能(neng)夠盡(jin)量混用(yong),想出了一(yi)個奇招:
仔細觀(guan)察一下(xia)USB接口,你會發現一共有四(si)個窄金(jin)屬條,稱為(wei)四(si)個引腳。這四(si)個引腳分別連(lian)接5V電源、GND地、D+數(shu)據線正信號和(he)D-數(shu)據線負信號。
一般(ban)兼容(rong)USB接口的(de)(de)(de)充電(dian)(dian)(dian)器(qi),D+和(he)D-兩(liang)(liang)個引(yin)腳是(shi)懸空的(de)(de)(de),任(ren)何設備只(zhi)要插(cha)上這樣的(de)(de)(de)充電(dian)(dian)(dian)器(qi),就(jiu)會(hui)從(cong)5V和(he)GND兩(liang)(liang)個引(yin)腳獲得電(dian)(dian)(dian)能。而蘋果的(de)(de)(de)充電(dian)(dian)(dian)器(qi)則(ze)在D+和(he)D-兩(liang)(liang)個數據(ju)引(yin)腳上增加了分壓(ya)電(dian)(dian)(dian)阻,使充電(dian)(dian)(dian)的(de)(de)(de)設備能夠(gou)在充電(dian)(dian)(dian)時從(cong)這兩(liang)(liang)條數據(ju)線上讀(du)到(dao)兩(liang)(liang)個電(dian)(dian)(dian)壓(ya)。
網(wang)絡上(shang)的(de)(de)(de)創客經過(guo)(guo)實踐證明,iPhone或者iPod對應的(de)(de)(de)5V1A充(chong)電器(qi)(qi),D+上(shang)的(de)(de)(de)電壓是(shi)2V,D-也(ye)是(shi)2V;而iPad使(shi)用(yong)的(de)(de)(de)5V2.1A的(de)(de)(de)充(chong)電器(qi)(qi),D+電壓2.7V,D-電壓2V。當iPad或者iPhone接上(shang)充(chong)電器(qi)(qi)時,通過(guo)(guo)這(zhe)兩個引腳上(shang)不同的(de)(de)(de)電壓就可以區分當前使(shi)用(yong)的(de)(de)(de)是(shi)哪種充(chong)電器(qi)(qi),也(ye)就能對負載做出(chu)相應的(de)(de)(de)調整,從而安全地充(chong)電。
呵呵,想蒙(meng)充電器……AI笑而不(bu)語
用iPad充(chong)電器給iPhone充(chong)電,會怎樣?
iPad和iPhone充(chong)電(dian)(dian)(dian)器的(de)(de)設(she)計(ji)不同是有原(yuan)因的(de)(de)。iPhone的(de)(de)電(dian)(dian)(dian)池容(rong)量(liang)較(jiao)小,只(zhi)需要1A的(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流就能在一個合理的(de)(de)時間內完成充(chong)電(dian)(dian)(dian)。雖然更大(da)(da)的(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流能大(da)(da)幅縮短充(chong)電(dian)(dian)(dian)時間,但會帶(dai)來更大(da)(da)的(de)(de)發熱量(liang),而高溫是鋰電(dian)(dian)(dian)池壽命(ming)縮短的(de)(de)頭號殺手,所以iPhone充(chong)電(dian)(dian)(dian)器的(de)(de)最大(da)(da)輸出電(dian)(dian)(dian)流被設(she)計(ji)為1A。
iPad的(de)(de)(de)充(chong)電器(qi)(qi)(qi)上(shang)標明了5V 2.1A,指的(de)(de)(de)是(shi)iPad的(de)(de)(de)充(chong)電器(qi)(qi)(qi)最(zui)大只(zhi)能(neng)輸(shu)出2.1A的(de)(de)(de)電流(liu)。當你用iPad的(de)(de)(de)充(chong)電器(qi)(qi)(qi)給iPhone充(chong)電時,雖然iPad的(de)(de)(de)充(chong)電器(qi)(qi)(qi)最(zui)大能(neng)夠提供2.1A的(de)(de)(de)電流(liu),但由于iPhone只(zhi)能(neng)接受1A的(de)(de)(de)電流(liu),iPad的(de)(de)(de)充(chong)電器(qi)(qi)(qi)也(ye)只(zhi)好遷(qian)就(jiu)它。這就(jiu)好比(bi)在4車(che)道的(de)(de)(de)公路上(shang)開車(che),遇到收費站的(de)(de)(de)時候,只(zhi)有1個收費亭開著,那么同時通過(guo)收費站的(de)(de)(de)汽(qi)車(che)最(zui)多也(ye)就(jiu)只(zhi)有1輛(liang)。
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)(chong)(chong)電,由于(yu)(yu)iPhone的充(chong)(chong)(chong)電器最大(da)只能提供1A的電流輸出,整個充(chong)(chong)(chong)電的時間(jian)會(hui)是原來的2.1倍左右(you)。由于(yu)(yu)蘋果在USB接口數據引(yin)腳上耍的小花招,iPad知道這(zhe)是iPhone的充(chong)(chong)(chong)電器,也就不(bu)會(hui)“要求”超過(guo)1A的充(chong)(chong)(chong)電電流,并(bing)不(bu)會(hui)使(shi)iPhone充(chong)(chong)(chong)電器過(guo)載而(er)導致損壞(huai)。
這(zhe)也好(hao)比在公路上,雖然收費站里有(you)(you)4個收費亭,但是由于修路的原(yuan)因,實際(ji)通(tong)車(che)(che)的車(che)(che)道只有(you)(you)1條(tiao),那么(me)同時通(tong)過(guo)這(zhe)個收費站的汽車(che)(che)最多仍然只有(you)(you)1輛。
至于(yu)這(zhe)條流言最后提到的(de),過高的(de)電(dian)(dian)流可(ke)能(neng)導(dao)致關鍵電(dian)(dian)容擊穿,完全邏輯不通(tong),也(ye)說明了微博作者缺乏電(dian)(dian)學物理知(zhi)識(shi)。電(dian)(dian)容的(de)最基本功能(neng)是“通(tong)交流,隔直(zhi)流”。充(chong)電(dian)(dian)器(qi)輸出(chu)的(de)是直(zhi)流電(dian)(dian),而無論(lun)多大的(de)直(zhi)流電(dian)(dian)流,都(dou)是無法通(tong)過電(dian)(dian)容的(de),并不能(neng)導(dao)致電(dian)(dian)容“擊穿”。能(neng)夠擊穿電(dian)(dian)容的(de),是過高的(de)直(zhi)流電(dian)(dian)壓,也(ye)就是“擊穿電(dian)(dian)壓”。
所以(yi)說,用iPad充(chong)電器為(wei)iPhone充(chong)電是完全可行(xing)的(de),對iPhone和(he)充(chong)電器都不(bu)會有損傷(shang)。而(er)iPhone充(chong)電器為(wei)iPad充(chong)電也可以(yi),只(zhi)不(bu)過所需的(de)充(chong)電時間更(geng)長(chang)。
話說回來,如果(guo)這(zhe)樣交(jiao)叉充電(dian)有危險的(de)話,以蘋果(guo)公司的(de)尿性……
他們根本不會把iPad和(he)iPhone的充(chong)電線做成一樣的啊(a)!