一次性電池不能夠充電，完全放電后的電池即為報廢電池。二次電池可以多次充電，但不同的化學特性對充電的要求也不同，特別是“快充”控制。目前，最常用的可充電電池是Li+、鎳氫(NiMH)、鎳鎘(Nicd)和鉛酸電池，其它類型的電池還很多，但沒有大規模投入使用。因為本文僅討論利用交流適配器供電的充電器設計，沒有考慮汽車電源供電的SLI鉛酸電池或更大容量電池的充電器。

不同化學類型的電池對充電器的要求  

通常快速充電比涓流充電更受歡迎，但快速充電對電路的要求也復雜，鎳氫或鎳鎘電池的快速充電技術與其它電池也是不同的。鎳鎘和鎳氫電池通常在恒流狀態下快充，而不是恒壓狀態下。快充終止檢測基于電壓和溫度的變化率，充電器還應具備過壓保護和過熱保護功能。Li+和鉛酸電池充電器必須保證作用到電池上的電壓和電流最大值在規定的范圍內，當電池電壓維持在最大單節電池電壓，充電電流下降到一個較低值時，充電器終止充電。Li+和鉛酸電池充電器的區別在于所允許的充電電流、最大電池電壓，另外鉛酸電池充電器一般具有浮充能力(浮充是為了補充鉛酸電池的自放電，而對一個已經完全充滿的電池繼續輸入充電電流的技術)，Li+電池的自放電非常低(di)，所以不需要浮(fu)充。

Li+電池

為便攜式產(chan)品選擇(ze)電(dian)(dian)池(chi)時，最(zui)(zui)重要的(de)是高能(neng)量密度、尺寸、重量和(he)(he)價(jia)格(ge)。迄今為止(zhi)，Li+電(dian)(dian)池(chi)在最(zui)(zui)為流行的(de)電(dian)(dian)池(chi)中能(neng)夠提(ti)供最(zui)(zui)高的(de)體積和(he)(he)能(neng)量密度，但其(qi)每(mei)瓦(wa)時的(de)成(cheng)本也較高。鉛酸電(dian)(dian)池(chi)的(de)每(mei)瓦(wa)時成(cheng)本最(zui)(zui)低，但比較笨重。本文以Li+電(dian)(dian)池(chi)為例討論充電(dian)(dian)器(qi)的(de)設計，它在便攜式產(chan)品中已經被普(pu)遍使用。我們(men)選擇(ze)780mA的(de)充電(dian)(dian)電(dian)(dian)流和(he)(he)4.2V的(de)終止(zhi)電(dian)(dian)壓。

充電器無需微處理器干預，輸入電源可以采用全球范圍的任何交流電源，省去了大體積60Hz變壓器，而且可提供單節Li+電池所要求的精確的充電電壓和電流。充電器IC(U4)集(ji)成(cheng)了全面的(de)保(bao)護(hu)功能(電(dian)壓、電(dian)流和自保(bao)護(hu))，確保(bao)Li+電(dian)池的(de)安全充(chong)電(dian)。

假設Li+電(dian)池帶(dai)有(you)過(guo)(guo)流、過(guo)(guo)壓(ya)和過(guo)(guo)熱保(bao)護，這(zhe)些保(bao)護特性在(zai)電(dian)池包(bao)里是必需的，因為充電(dian)期間一旦(dan)電(dian)路出現(xian)故障，Li+電(dian)池將存在(zai)很大的危險性，過(guo)(guo)流、過(guo)(guo)壓(ya)或溫度過(guo)(guo)高都有(you)可能造(zao)成Li+電(dian)池爆炸。

包括兩顆主器(qi)件(U1和U4)、精密(mi)基準(zhun)(U3)和光(guang)耦(ou)(ou)(U2)。U1是離線式開關控(kong)制(zhi)(zhi)器(qi)，配合隔離變壓(ya)(ya)(ya)器(qi)、光(guang)耦(ou)(ou)和基準(zhun)產生隔離的(de)穩壓(ya)(ya)(ya)直流輸出。直流電(dian)(dian)(dian)壓(ya)(ya)(ya)供給電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)器(qi)(U4)，U4提供電(dian)(dian)(dian)流限制(zhi)(zhi)、電(dian)(dian)(dian)壓(ya)(ya)(ya)調(diao)節、電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)和充(chong)電(dian)(dian)(dian)指示(shi)等功能。本方案(an)中，U4是一款簡(jian)單的(de)線性(xing)充(chong)電(dian)(dian)(dian)器(qi)，內(nei)置(zhi)調(diao)整管，結合其熱控(kong)制(zhi)(zhi)環路(lu)提供快(kuai)速充(chong)電(dian)(dian)(dian)。

MAX5022的特性

U1(MAX5022)在寬輸(shu)入范(fan)圍(wei)的(de)(de)(de)應用中很(hen)容(rong)易設計，本(ben)文所提供的(de)(de)(de)方案(an)要(yao)求能夠(gou)滿(man)足(zu)全球(qiu)各地的(de)(de)(de)交流電(dian)源規格，這里假設通(tong)用的(de)(de)(de)輸(shu)入電(dian)源電(dian)壓范(fan)圍(wei)為85VAC至265VAC。MAX5022的(de)(de)(de)輸(shu)入范(fan)圍(wei)指標以及評估(gu)板(ban)(ban)電(dian)路的(de)(de)(de)輸(shu)入范(fan)圍(wei)恰好滿(man)足(zu)這一需(xu)求。對(dui)于圖1所示充電(dian)器的(de)(de)(de)電(dian)源端MAX5022評估(gu)板(ban)(ban)不需(xu)要(yao)作(zuo)任何(he)修改，隔離(li)端只需(xu)對(dui)評估(gu)板(ban)(ban)的(de)(de)(de)電(dian)阻(zu)值稍作(zuo)修改。

對于更(geng)大(da)功率(lv)(lv)的(de)應用(yong)，只需(xu)選(xuan)取功率(lv)(lv)較大(da)的(de)開關管(guan)和(he)能夠(gou)處理更(geng)大(da)功率(lv)(lv)的(de)變壓(ya)(ya)器即(ji)可。圖1所示電(dian)(dian)(dian)(dian)路要(yao)求(qiu)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流為(wei)780mA，最(zui)大(da)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)4.2V。對充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源(yuan)的(de)要(yao)求(qiu)與MAX5022評(ping)(ping)估板所提供的(de)輸(shu)出相吻合(he)：5V@1A，因(yin)此，不需(xu)要(yao)更(geng)換評(ping)(ping)估板的(de)晶體管(guan)和(he)變壓(ya)(ya)器。U4采(cai)用(yong)SOT23封(feng)裝(zhuang)，所以，充(chong)電(dian)(dian)(dian)(dian)器的(de)尺(chi)寸(cun)(cun)在很大(da)程(cheng)度上取決于應用(yong)對充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源(yuan)的(de)需(xu)求(qiu)。變壓(ya)(ya)器是電(dian)(dian)(dian)(dian)路中尺(chi)寸(cun)(cun)最(zui)大(da)的(de)元件(jian)，由于開關控制器的(de)工作頻率(lv)(lv)大(da)于250kHz，允許系統選(xuan)用(yong)小尺(chi)寸(cun)(cun)的(de)變壓(ya)(ya)器。

上電(dian)(dian)時(shi)(shi)，在(zai)開關(guan)控制(zhi)器(qi)工作之前，U1調節器(qi)直接通過(guo)泄漏電(dian)(dian)阻(zu)(zu)(zu)R1、R2從整流(liu)通路吸取少量(liang)的(de)(de)(de)電(dian)(dian)流(liu)，兩個(ge)電(dian)(dian)阻(zu)(zu)(zu)阻(zu)(zu)(zu)值(zhi)保證每個(ge)電(dian)(dian)阻(zu)(zu)(zu)上的(de)(de)(de)壓(ya)降不會(hui)超(chao)(chao)出每個(ge)電(dian)(dian)阻(zu)(zu)(zu)的(de)(de)(de)容限(xian)，Vin引(yin)(yin)腳電(dian)(dian)壓(ya)不會(hui)超(chao)(chao)出其(qi)28V額定(ding)值(zhi)(30V為絕對最大(da)(da)值(zhi))，U1在(zai)輸入(ru)電(dian)(dian)壓(ya)達到24V時(shi)(shi)開始(shi)開關(guan)操(cao)作，并吸取更大(da)(da)的(de)(de)(de)電(dian)(dian)流(liu)(高于R1、R2所(suo)能(neng)提供(gong)(gong)的(de)(de)(de)電(dian)(dian)流(liu))，在(zai)變(bian)壓(ya)器(qi)副(fu)邊(bian)線圈能(neng)夠(gou)(gou)(gou)提供(gong)(gong)足夠(gou)(gou)(gou)的(de)(de)(de)能(neng)量(liang)之前，額外的(de)(de)(de)電(dian)(dian)流(liu)由Vin引(yin)(yin)腳的(de)(de)(de)旁路電(dian)(dian)容供(gong)(gong)給。這(zhe)種處理方式能(neng)夠(gou)(gou)(gou)適合較寬的(de)(de)(de)輸入(ru)電(dian)(dian)壓(ya)范圍(wei)，對效率的(de)(de)(de)影響也(ye)很小，這(zhe)是因為在(zai)啟動過(guo)程中只需極小的(de)(de)(de)供(gong)(gong)電(dian)(dian)電(dian)(dian)流(liu)(典型值(zhi)為50uA)。  

為了防止(zhi)U1的(de)Vin引腳出(chu)現過(guo)壓，可以在(zai)Vin與地之間接一個26V至30V的(de)齊納(na)管，電壓值需(xu)要高(gao)于(yu)(yu)欠壓鎖(suo)存電壓的(de)最(zui)(zui)大值，低于(yu)(yu)該引腳所允(yun)許的(de)最(zui)(zui)大絕對(dui)電壓。如果(guo)器件沒(mei)有啟動正常(chang)的(de)開關操(cao)作，則(ze)可認(ren)為電路發生(sheng)了某(mou)些問題，所以，這一保護措施對(dui)于(yu)(yu)U1來(lai)說并不是必需(xu)的(de)。

U1是(shi)一款(kuan)電(dian)(dian)流模式(shi)PWM控制(zhi)(zhi)器(qi)，具有逐周期限(xian)流電(dian)(dian)路，必要時其占(zhan)(zhan)空比可(ke)以提高到(dao)75%，非常適(shi)合圖1所示的反激拓撲。原(yuan)邊開關電(dian)(dian)流檢(jian)測采用(yong)尺寸(cun)為1206的1.78Ω電(dian)(dian)阻(R7)，該(gai)電(dian)(dian)阻限(xian)制(zhi)(zhi)了(le)變壓器(qi)原(yuan)邊的最大電(dian)(dian)流。固定開關頻率(lv)和最大占(zhan)(zhan)空比限(xian)制(zhi)(zhi)使得最大限(xian)流具有輸出(chu)短路保護功能。  

一旦短(duan)路輸出(chu)造成電(dian)(dian)路達到了上(shang)述限制條件，第三(san)組線圈(quan)將無(wu)法(fa)提供10V以上(shang)的(de)電(dian)(dian)壓(UVLO的(de)低(di)電(dian)(dian)壓門限)，U1將再次進(jin)入啟動狀態，停止開關操作(zuo)。短(duan)路故障解(jie)除(chu)后系統(tong)會自動恢復正常的(de)工作(zuo)狀態。  

電壓調節
 
變壓(ya)器(qi)副(fu)邊的(de)電(dian)壓(ya)經過整流、濾波，然后由(you)R4、R5分壓(ya)在(zai)并聯型穩壓(ya)器(qi)U3的(de)調節(jie)點產生1.24V(對應于4.5V輸出(chu))的(de)反饋電(dian)壓(ya)。為(wei)保證電(dian)池充電(dian)器(qi)正常工(gong)作，4.5V是最(zui)低電(dian)壓(ya)(包括容(rong)差)。因為(wei)充電(dian)器(qi)采(cai)用的(de)是線性(xing)結構，充電(dian)效率與輸入、輸出(chu)電(dian)壓(ya)的(de)差值成(cheng)反比，用最(zui)低電(dian)壓(ya)為(wei)充電(dian)器(qi)供電(dian)有助于降(jiang)低功率損耗。  

當調節(jie)點(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高(gao)于(yu)1.24V時(shi)(shi)(shi)，并聯型穩壓(ya)(ya)(ya)器將吸入電(dian)(dian)(dian)(dian)(dian)流(liu)，導通光(guang)(guang)耦LED，原邊的(de)(de)(de)(de)(de)光(guang)(guang)敏晶(jing)體管將處于(yu)發光(guang)(guang)狀態(tai)。U1的(de)(de)(de)(de)(de)OPTO輸入引(yin)腳用于(yu)直接(jie)(jie)連接(jie)(jie)光(guang)(guang)敏晶(jing)體管，以極其簡單的(de)(de)(de)(de)(de)方式構成(cheng)閉(bi)合環路。光(guang)(guang)敏晶(jing)體管導通時(shi)(shi)(shi)，OPTO引(yin)腳被拉低(di)，內部(bu)比(bi)(bi)較器在它(ta)的(de)(de)(de)(de)(de)一(yi)(yi)個(ge)輸入端檢(jian)測到較低(di)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，比(bi)(bi)較器的(de)(de)(de)(de)(de)另一(yi)(yi)輸入電(dian)(dian)(dian)(dian)(dian)流(liu)檢(jian)測引(yin)腳(CS)的(de)(de)(de)(de)(de)峰值(zhi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，OPTO引(yin)腳的(de)(de)(de)(de)(de)低(di)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)將在每(mei)個(ge)周期直接(jie)(jie)限(xian)制功率MOSFETN1的(de)(de)(de)(de)(de)峰值(zhi)電(dian)(dian)(dian)(dian)(dian)流(liu)。由于(yu)U1是一(yi)(yi)個(ge)PWM控(kong)制器，電(dian)(dian)(dian)(dian)(dian)流(liu)限(xian)制使得電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)調節(jie)受(shou)作(zuo)用在N1上(shang)的(de)(de)(de)(de)(de)占空比(bi)(bi)(導通時(shi)(shi)(shi)間(jian)與斷開時(shi)(shi)(shi)間(jian)的(de)(de)(de)(de)(de)比(bi)(bi)值(zhi))的(de)(de)(de)(de)(de)影響(xiang)，環路穩定性(xing)通過調節(jie)R11和C12來保證。R10和C5(連接(jie)(jie)在U3的(de)(de)(de)(de)(de)第3和第4引(yin)腳)可消除(chu)穩定工(gong)作(zuo)情況下的(de)(de)(de)(de)(de)噪聲干擾。

U4的工作特點

U4是一款(kuan)用于單節Li+電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)、功能完備(bei)的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)，采(cai)用線(xian)性充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)模式，內置調整(zheng)管(guan)和電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)檢測電(dian)(dian)(dian)(dian)(dian)路。另外，它還集(ji)成了一個(ge)反向抑(yi)制二極(ji)管(guan)，在去掉輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)源時(shi)可防止電(dian)(dian)(dian)(dian)(dian)池方(fang)向放電(dian)(dian)(dian)(dian)(dian)。接入(ru)一個(ge)深度放電(dian)(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)(dian)池時(shi)，U4能夠檢測到(dao)低(di)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(低(di)于2.5V)，這樣，U4將首(shou)先啟(qi)動涓(juan)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過程，在快(kuai)充(chong)(chong)周期的1/10時(shi)間段對電(dian)(dian)(dian)(dian)(dian)池進行涓(juan)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，直到(dao)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓上(shang)升到(dao)2.5V以(yi)上(shang)。在涓(juan)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)到(dao)快(kuai)速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)轉換時(shi)，軟啟(qi)動電(dian)(dian)(dian)(dian)(dian)路迫使充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)在3ms時(shi)間內緩慢上(shang)升，避(bi)免較大的浪涌電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)拉低(di)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)源。

   上述功能(neng)(neng)的(de)(de)實施不需要微控制(zhi)(zhi)器的(de)(de)監管，而且，U4還具(ju)有可編程(cheng)的(de)(de)溫度限制(zhi)(zhi)功能(neng)(neng)，我們會在下(xia)面就(jiu)這一點進行(xing)詳細討論。用一個電(dian)(dian)(dian)(dian)阻(zu)(zu)設置(zhi)最(zui)大充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)，電(dian)(dian)(dian)(dian)阻(zu)(zu)兩端的(de)(de)電(dian)(dian)(dian)(dian)壓與(yu)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)成正(zheng)比，通(tong)過監視該電(dian)(dian)(dian)(dian)壓即可連(lian)續(xu)跟蹤(zong)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)，更為復(fu)雜的(de)(de)系統(tong)也可以采用ADC跟蹤(zong)監視充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)。

Maxim還提(ti)供有另一款(kuan)與(yu)MAX1507非常相似的充(chong)電(dian)器―MAX1555，這款(kuan)IC能(neng)夠在沒(mei)有交流電(dian)源(yuan)的情況下從USB主機獲得充(chong)電(dian)電(dian)源(yuan)。  

電流調節

如果把Li+電池直接與一個低阻電壓源連接，充電電流將不受任何限制，這種狀況會對電池及其周圍環境造成災難性的損害，從Li+電池的安全性考慮，必須將其充電電流限制在額定范圍以內。U4根據連接在ISET(第5引腳)的電阻限制充電電流，圖1電路中選用了一個1.87kΩ的(de)電阻，將最大電流設置(zhi)在780mA:

Ifast=1461V/Rset=1461/1870≈780mA

電池電壓(ya)最(zui)小時，由于輸入穩定(ding)在4.5V，U4輸入與輸出的壓(ya)差(cha)最(zui)大，如(ru)果此時電池是以最(zui)大電流充(chong)電，U4功(gong)耗將達(da)到最(zui)大值。例如(ru)，假設電池電壓(ya)為(wei)2.5V，則對應的功(gong)耗為(wei)：

P=IV=(0.78A)×(4.5V-2.5V)=1.56W

U4封裝(8引腳薄型DFN-EP，EP表示裸露焊盤)在溫度高達70℃時可以耗散的最大功率是1.951W，這樣，在整個電池電壓范圍內以780mA的電流充電應該沒有任何問題。但是，如果IC管芯由于較高的環境溫度或不良的散熱條件達到了70℃，U4內部的熱調節環路將自動降低充電電流，這一過程有別于其它充電IC中的“熱關斷”，“熱關斷”方式只是簡單地中止芯片中的所有電路工作，直到晶片溫度降至規定的數值。MAX1507所采用的方案能夠保證在芯片溫度不超出最大限制范圍的條件下提供最快的充電速率，隨著電池電壓的升高，充電電流在保持最高溫度的前提下逐漸升高，直到達到最大充電電流。在此之后，充電器在滿足芯片溫度限制的條件下將以最大充電電流對電池充電，直到(dao)電池電壓達(da)到(dao)內(nei)部(bu)設置的4.2V±1%。電池電壓達(da)到(dao)門限值后(hou)，U4將輸出電壓保持在4.2V，從而使充電電流(liu)開(kai)始(shi)下降。充電電流(liu)降低到(dao)快充電流(liu)的10%時，充電指示燈(deng)關閉，表示充電周期結束(shu)。

如(ru)(ru)果充(chong)(chong)電過(guo)程(cheng)中輸出負載增大(da)，例(li)如(ru)(ru)，用戶在電池(chi)充(chong)(chong)電時啟動了(le)其(qi)它電路，U4允許返回(hui)到限流模式。

測試結果

圖(tu)1電(dian)(dian)(dian)(dian)路(lu)(lu)輸(shu)(shu)入為110V交流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)源，輸(shu)(shu)出(chu)為4.14V、740mA負載，效(xiao)率可達到46%。當負載電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)增大(da)使電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)降(jiang)至(zhi)(zhi)2.7V時(shi)，電(dian)(dian)(dian)(dian)路(lu)(lu)將輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)限(xian)制在802mA，比設置的(de)780mA限(xian)流(liu)(liu)(liu)門限(xian)提高不(bu)到3%，在規定(ding)的(de)參數指標(biao)以(yi)內。MAX1507允許(xu)±8%的(de)變化(hua)。當電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)拉至(zhi)(zhi)2.5V時(shi)，輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)降(jiang)至(zhi)(zhi)76.1mA，在78mA(780mA的(de)1/10)的(de)3%以(yi)內。U4數據手冊中規定(ding)允許(xu)±5%的(de)范圍。輸(shu)(shu)出(chu)短路(lu)(lu)時(shi)電(dian)(dian)(dian)(dian)路(lu)(lu)還允許(xu)返回到該模(mo)式(shi)。

空載時，輸出穩定在4.2V左右，形成一個三角波，在U4輸出接一個負載電阻可以消除這個偏差，保持其連續性，但會降低系統效率，但對于交流電供電(dian)系統來說，效率并不重要(yao)。

利用電(dian)流(liu)(liu)模式PWM控(kong)(kong)制器(U1)構成隔離電(dian)源(yuan)，結合(he)Li+電(dian)池充(chong)電(dian)IC(U4)和其(qi)它元件(jian)可以構成一個(ge)由(you)通(tong)用的(de)(de)交流(liu)(liu)電(dian)源(yuan)供(gong)電(dian)的(de)(de)Li+電(dian)池充(chong)電(dian)器。該方案不需要任(ren)何(he)額外的(de)(de)控(kong)(kong)制電(dian)路(如微(wei)控(kong)(kong)制器的(de)(de)干預)，也不需要軟(ruan)件(jian)開發(fa)(fa)。硬件(jian)開發(fa)(fa)只需對Maxim提供(gong)的(de)(de)標準評估板稍作修改(gai)即可，具(ju)有成本低、開發(fa)(fa)周期短等優(you)勢。

由于系統(tong)沒有60Hz的隔離變壓器，具有尺寸(cun)小、輕(qing)便等特點，可用于手(shou)機或其它手(shou)持(chi)設備(bei)(bei)的充電。所有熱量(liang)均集中(zhong)在交流適配(pei)器內，與內置(zhi)充電器的手(shou)持(chi)設備(bei)(bei)相比，不需要(yao)過多考慮散熱問題。