便攜式電(dian)(dian)(dian)(dian)源應用領(ling)域(yu)寬(kuan)泛而多樣。產品(pin)涵(han)蓋了從(cong)平均功(gong)耗僅幾 μW 的(de)(de)無線(xian)傳感器(qi)節(jie)點(dian)到(dao)采(cai)用好幾百瓦時(shi)電(dian)(dian)(dian)(dian)池組的(de)(de)車載式醫(yi)療或數據采(cai)集系統(tong)等(deng)眾多門類。然(ran)而，盡管品(pin)種繁多，但它們(men)卻呈現出(chu)了相對(dui)一(yi)致的(de)(de)發展趨勢 ━━ 設計人員(yuan)不斷地要(yao)求(qiu)其產品(pin)擁有較高的(de)(de)功(gong)率以支持(chi)更多的(de)(de)功(gong)能，并指望能從(cong)任何可用的(de)(de)電(dian)(dian)(dian)(dian)源來給電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)。第(di)一(yi)個(ge)趨勢要(yao)求(qiu)增加電(dian)(dian)(dian)(dian)池容量。不幸的(de)(de)是，用戶常常缺乏(fa)耐(nai)心，而且增加的(de)(de)電(dian)(dian)(dian)(dian)池容量必(bi)須要(yao)在合理(li)的(de)(de)時(shi)間之內完成充(chong)電(dian)(dian)(dian)(dian)，這就(jiu)必(bi)然(ran)導致充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)(de)增大。第(di)二個(ge)趨勢則要(yao)求(qiu)電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)解(jie)決方(fang)案具有巨大的(de)(de)靈活性。我們(men)將對(dui)這些(xie)問(wen)題逐個(ge)進行較為詳細的(de)(de)探究。

　　更高的功率

　　新式的手持設備 (無論是消費類設備還是工業設備) 都有可能包括一個蜂窩電話調制解調器、一個WiFi模塊、一個藍牙模塊、一個大型的背面照明顯示器等等。許多手持式設備的電源架構都可通過蜂窩電話反映出來。通常，3.7V 的鋰離子電池因其很高的重量 (Wh/kg) 和體積 (Wh/m3) 能量密度而被用作主電源。過去，不少高功率密度設備都采用一個 7.4V 鋰離子電池以降低(di)電(dian)(dian)(dian)流需求，但廉(lian)價的(de)(de) 5V 電(dian)(dian)(dian)源管理 IC 的(de)(de)面(mian)市(shi)使得越來越多的(de)(de)手(shou)持(chi)式設備轉而(er)采用較低(di)電(dian)(dian)(dian)壓架構。平板電(dian)(dian)(dian)腦(nao)(nao)很好地(di)體現了這(zhe)一點 ━━ 標準(zhun)的(de)(de)平板電(dian)(dian)(dian)腦(nao)(nao)擁有豐(feng)富(fu)的(de)(de)功能以及非(fei)常大 (用于(yu)便攜式設備) 的(de)(de)屏(ping)幕。當采用一個 3.7V 電(dian)(dian)(dian)池(chi)(chi)來供電(dian)(dian)(dian)時，電(dian)(dian)(dian)池(chi)(chi)的(de)(de)容量必須(xu)達到(dao)幾(ji)千mAh。為了能夠在幾(ji)個小(xiao)時之內(nei)完成此類(lei)電(dian)(dian)(dian)池(chi)(chi)的(de)(de)充電(dian)(dian)(dian)，需要幾(ji)千mA的(de)(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)流。

　　然而，消費者(zhe)同樣(yang)希望能夠(gou)在沒有可(ke)用(yong)(yong)的(de)(de)(de)(de)大電(dian)(dian)(dian)流(liu)(liu)墻(qiang)上(shang)適(shi)配器(qi)時從(cong)一(yi)(yi)個(ge) USB 端口來為其(qi)高(gao)功(gong)率(lv)設備充電(dian)(dian)(dian)，這種愿望并未因為上(shang)述的(de)(de)(de)(de)高(gao)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)而被遏制。為了(le)滿足(zu)這些要求，在可(ke)以使用(yong)(yong)墻(qiang)上(shang)適(shi)配器(qi)時，電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器(qi)必(bi)須要能夠(gou)以高(gao)電(dian)(dian)(dian)流(liu)(liu) (>2A) 進(jin)行充電(dian)(dian)(dian)，但仍然可(ke)以高(gao)效地(di)利(li)用(yong)(yong) USB 端口所提供(gong)的(de)(de)(de)(de) 2.5W 至 4.5W 功(gong)率(lv)。此外，產(chan)品還必(bi)需避免敏感的(de)(de)(de)(de)下游低電(dian)(dian)(dian)壓組件遭受(shou)有可(ke)能造成損壞的(de)(de)(de)(de)過壓，將高(gao)電(dian)(dian)(dian)流(liu)(liu)從(cong)一(yi)(yi)個(ge) USB 輸(shu)入(ru)、一(yi)(yi)個(ge)墻(qiang)上(shang)適(shi)配器(qi)或電(dian)(dian)(dian)池(chi)無縫地(di)引導(dao)至負(fu)載(zai)，并最大限度地(di)降低功(gong)率(lv)損耗。與此同時，IC 必(bi)須安全(quan)地(di)管理電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)算法(fa)并監視關鍵的(de)(de)(de)(de)系統(tong)參數。

　　解決單節(jie)電池(chi)供電型便(bian)攜(xie)式產品的(de)電源難(nan)題(ti)

　　盡(jin)管(guan)似乎無法找到單(dan)個 IC 來滿(man)足上(shang)述要求(qiu)，但不妨考慮一下 LTC4155，這是(shi)一款高功率、I2C 控(kong)制(zhi)(zhi)、高效率 PowerPathTM管(guan)理器、理想二極管(guan)控(kong)制(zhi)(zhi)器和鋰離(li)子電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)器。該器件(jian)設計用于從多種(zhong) 5V 電(dian)(dian)(dian)(dian)源高效地(di)輸(shu)送高達 3A 的(de)(de)電(dian)(dian)(dian)(dian)流(liu)，可(ke)為電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)及系(xi)統(tong)用途提(ti)供 3.5A 以上(shang)的(de)(de)電(dian)(dian)(dian)(dian)流(liu)。即使在這些高電(dian)(dian)(dian)(dian)流(liu)水(shui)平下，LTC4155 的(de)(de) 88% ~ 94% 效率仍然可(ke)使熱預算限(xian)制(zhi)(zhi)條件(jian)有所(suo)放寬。LTC4155 的(de)(de)開關 PowerPath 拓撲結構(gou)可(ke)對從兩個輸(shu)入(ru)電(dian)(dian)(dian)(dian)源 (比(bi)如：墻(qiang)上(shang)適配器和 USB 端(duan)口) 至設備的(de)(de)可(ke)再充(chong)(chong)電(dian)(dian)(dian)(dian)鋰離(li)子電(dian)(dian)(dian)(dian)池的(de)(de)功率輸(shu)送進行無縫(feng)管(guan)理，并在輸(shu)入(ru)功率有限(xian)時優先向系(xi)統(tong)負載(zai)供電(dian)(dian)(dian)(dian)。

　　LTC4155 的開關穩壓器起一個變壓器的作用，允許 VOUT 上的負載電流超過輸入電源所吸收的電流，與常用的線性模式充電器相比，大幅度地改善了電池充電可用功率的使用效率。如前面的例子所示，LTC4155 能夠以高達 3.5A 的電流進行高效充電，從而縮短充電時間。與普通的開關電池充電器不同，LTC4155 具有(you)“即(ji)時接(jie)通”操(cao)作(zuo)能力，以確保在插入(ru)電(dian)源時可(ke)立即(ji)獲(huo)得(de)系統(tong)功率，即(ji)使所采用的是一個失(shi)效的電(dian)池或深度放(fang)電(dian)的電(dian)池也不例外。

　　在(zai)(zai)對電(dian)(dian)(dian)池(chi)進行(xing)高速充(chong)(chong)電(dian)(dian)(dian)時，監視電(dian)(dian)(dian)池(chi)的(de)(de)安全性是很重(zhong)要的(de)(de)。LTC4155 將在(zai)(zai)電(dian)(dian)(dian)池(chi)溫(wen)度(du)(du)下降(jiang)至 0℃ 以下或上(shang)(shang)升至 40℃ 以上(shang)(shang) (由一個外(wai)部負溫(wen)度(du)(du)系數 [NTC] 熱敏電(dian)(dian)(dian)阻負責測量) 時自(zi)動停止充(chong)(chong)電(dian)(dian)(dian)。除(chu)了這種(zhong)自(zi)主(zhu)特性之外(wai)，LTC4155 還提(ti)供了一個 7 位擴展(zhan)標度(du)(du)模數轉換器(qi) (ADC)，用于(yu)以大約 1℃ 的(de)(de)分(fen)辨率來監視電(dian)(dian)(dian)池(chi)的(de)(de)溫(wen)度(du)(du)。結合 4 種(zhong)可用的(de)(de)浮(fu)置(zhi)電(dian)(dian)(dian)壓(ya)設(she)定(ding)值(zhi)和 15 種(zhong)電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)設(she)定(ding)值(zhi)，該 ADC 能(neng)夠用于(yu)建立基于(yu)電(dian)(dian)(dian)池(chi)溫(wen)度(du)(du)的(de)(de)定(ding)制充(chong)(chong)電(dian)(dian)(dian)算法。

　　通過一個簡單的二線式 I2C 端口可獲得 NTC ADC 結果，從而據此調整充電電流和電壓設定值。該I2C 端口還通過控制 16 種輸入電流限制設定值 (包括可兼容 USB 2.0 和 3.0 規格的設定值) 提供了與 USB 規范的兼容性。通信總線允許 LTC4155提供額外的狀態指示信息，例如：輸入電源狀態、充電器狀態(tai)和(he)故障狀態(tai)。USB OTG (On-The-Go) 支持(chi)能力可在(zai)未采用任何附(fu)加組件(jian)的(de)情況下提(ti)供一個返回 USB 端口(kou)的(de) 5V 電源(yuan)。

　　LTC4155 的(de)(de)雙(shuang)輸(shu)入、優(you)先級(ji)多路復用器可(ke)根據用戶定義的(de)(de)優(you)先級(ji) (適(shi)配器輸(shu)入是默認的(de)(de)優(you)先選擇) 自主選擇最合適(shi)的(de)(de)輸(shu)入 (墻上(shang)適(shi)配器或(huo)(huo) USB)。過壓(ya)(ya)保護 (OVP) 電(dian)(dian)路用于(yu)同時保護兩個輸(shu)入免遭因意(yi)外(wai)施加(jia)高電(dian)(dian)壓(ya)(ya)或(huo)(huo)反向電(dian)(dian)壓(ya)(ya)而(er)造成的(de)(de)損壞。LTC4155 的(de)(de)理想二(er)極管控制器可(ke)確保始終能夠向 VOUT 提供足(zu)(zu)夠的(de)(de)功率，即使輸(shu)入功率不(bu)足(zu)(zu)或(huo)(huo)缺失也不(bu)例(li)外(wai)。

　　對于(yu)諸如平板電(dian)腦(nao)或工業條(tiao)形(xing)碼掃描儀等許多便(bian)攜(xie)式(shi)(shi)應用(yong)而言，管理兩個輸入 (例如：USB和墻上適配器) 就足夠(gou)了(le)。不過，便(bian)攜(xie)式(shi)(shi)設(she)備的設(she)計(ji)人員(yuan)仍在繼續(xu)探尋(xun)能夠(gou)從任何可用(yong)電(dian)源來給電(dian)池充電(dian)的方法(fa)。

　　多種輸入電源

　　諸多(duo)原因(yin)導致用戶希(xi)望(wang)從多(duo)種(zhong)(zhong)(zhong)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)源來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。某些應(ying)(ying)用有可能需(xu)要(yao)(yao)脫(tuo)離電(dian)(dian)(dian)(dian)(dian)(dian)網(wang)并(bing)指望(wang)由太(tai)陽能板(ban)來供電(dian)(dian)(dian)(dian)(dian)(dian)。其他(ta)的(de)(de)(de)應(ying)(ying)用則希(xi)望(wang)擁有能夠從墻上適配器、汽車電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)或(huo)(huo)者高電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)工業或(huo)(huo)電(dian)(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)(dian)源進行充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)便利。不管是什么原因(yin)，這種(zhong)(zhong)(zhong)要(yao)(yao)求都給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)系統施加了一(yi)(yi)(yi)個沉重的(de)(de)(de)負(fu)擔。大多(duo)數電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器均利用一(yi)(yi)(yi)種(zhong)(zhong)(zhong)降壓(ya)(ya) (開關(guan)或(huo)(huo)線性) 架構從一(yi)(yi)(yi)個高于最(zui)大電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)源來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。早先(xian)的(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器產品通(tong)(tong)常被(bei)限制于大約 30V 的(de)(de)(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。此類局(ju)限性導致設計人員(yuan)無法考慮將電(dian)(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)(dian)源作(zuo)為可行的(de)(de)(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)源，或(huo)(huo)者采用具(ju)有 42V 開路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)太(tai)陽能板(ban)。在(zai)某些場合中，期望(wang)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)范圍既會(hui)升(sheng)至電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以上也會(hui)降至電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以下(xia)。設計旨(zhi)在(zai)應(ying)(ying)對(dui)上述難(nan)題(ti)的(de)(de)(de)解決方案通(tong)(tong)常需(xu)要(yao)(yao)整(zheng)合高精(jing)度(du)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流檢(jian)測放(fang)大器、ADC、用于控制充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)操(cao)作(zuo)的(de)(de)(de)微處理器、高性能的(de)(de)(de) DC/DC 轉(zhuan)換器以及理想二極(ji)管或(huo)(huo)多(duo)路(lu)(lu)復用電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)。凌力爾特公司推出了一(yi)(yi)(yi)款更加優越的(de)(de)(de)解決方案。

　　功(gong)能強大(da)且擁有無(wu)可比(bi)擬之(zhi)靈活性的(de)充電解決方案

　　LTC4000 可將任何在外部補償的 DC/DC 電源轉換為一個全功能的電池充電器，并具有 PowerPathTM 控(kong)制功能(neng)(neng)。LTC4000 能(neng)(neng)夠驅動的(de)(de)常用(yong)DC/DC 轉換(huan)器(qi)拓撲結構包(bao)括 (但不限于) 降(jiang)壓(ya)(ya)、升壓(ya)(ya)、降(jiang)壓(ya)(ya)-升壓(ya)(ya)、SEPIC 和反激式(shi)。該器(qi)件提供(gong)了精準的(de)(de)輸(shu)入(ru)(ru)電(dian)(dian)(dian)流和充電(dian)(dian)(dian)電(dian)(dian)(dian)流調節，并可(ke)在一個 3V 至(zhi) 60V 的(de)(de)寬輸(shu)入(ru)(ru)和輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)范(fan)圍內運作，因(yin)而與多種不同的(de)(de)輸(shu)入(ru)(ru)電(dian)(dian)(dian)壓(ya)(ya)電(dian)(dian)(dian)源(yuan)、電(dian)(dian)(dian)池組尺(chi)寸和化(hua)學組成相兼容。由于這款器(qi)件采用(yong)了通用(yong)型配(pei)置，因(yin)此其典型應用(yong)范(fan)圍十(shi)分廣泛，包(bao)括高功率(lv)電(dian)(dian)(dian)池充電(dian)(dian)(dian)器(qi)系統、高性能(neng)(neng)便攜(xie)式(shi)儀器(qi)、電(dian)(dian)(dian)池后(hou)備系統、配(pei)備電(dian)(dian)(dian)池的(de)(de)工(gong)業(ye)設備以及(ji)筆(bi)記本電(dian)(dian)(dian)腦 / 小(xiao)型筆(bi)記本電(dian)(dian)(dian)腦等。

　　除了(le)可(ke)支持多種不同的(de)(de) DC/DC 拓(tuo)撲(pu)結構之外(wai)，LTC4000 的(de)(de)高電(dian)(dian)(dian)壓能(neng)力還(huan)使(shi)(shi)其能(neng)夠利用幾乎任何輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)源來形(xing)成功(gong)(gong)能(neng)強(qiang)大的(de)(de)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)解決方案。為了(le)確(que)(que)保來自(zi)這些輸(shu)(shu)入(ru)(ru)的(de)(de)功(gong)(gong)率能(neng)輸(shu)(shu)送(song)至合適(shi)的(de)(de)負載，LTC4000采用了(le)一種智能(neng) PowerPathTM 拓(tuo)撲(pu)結構，當(dang)輸(shu)(shu)入(ru)(ru)功(gong)(gong)率有(you)限時，該拓(tuo)撲(pu)結構將優先向(xiang)(xiang)系(xi)統(tong)(tong)負載供電(dian)(dian)(dian)。LTC4000 通過控(kong)制外(wai)部(bu)(bu) PFET 來提供低(di)(di)損耗反向(xiang)(xiang)電(dian)(dian)(dian)流保護、電(dian)(dian)(dian)池(chi)的(de)(de)低(di)(di)損耗充(chong)電(dian)(dian)(dian)和放(fang)電(dian)(dian)(dian)以及“即時接通型”操作(zuo)，以確(que)(que)保在插入(ru)(ru)電(dian)(dian)(dian)源時可(ke)立即獲得系(xi)統(tong)(tong)功(gong)(gong)率，即使(shi)(shi)所采用的(de)(de)是(shi)一個失(shi)效的(de)(de)電(dian)(dian)(dian)池(chi)或深(shen)度(du)放(fang)電(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)池(chi)也不例外(wai)。外(wai)部(bu)(bu)檢測電(dian)(dian)(dian)阻器(qi)可(ke)提供輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)流和電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流信息，從而(er)使(shi)(shi)得 LTC4000 能(neng)夠與功(gong)(gong)率范圍從幾毫(hao)瓦(wa)到(dao)幾千瓦(wa)的(de)(de)轉換器(qi)一起使(shi)(shi)用。

　　LTC4000 的(de)(de)全功(gong)能電(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)控(kong)制器可(ke)對多種(zhong)電(dian)(dian)池(chi)(chi)(chi)化學組成進行充(chong)電(dian)(dian)，包括(kuo)鋰離子電(dian)(dian)池(chi)(chi)(chi) / 鋰聚合物電(dian)(dian)池(chi)(chi)(chi) / 磷酸鐵鋰電(dian)(dian)池(chi)(chi)(chi)、密封(feng)鉛酸電(dian)(dian)池(chi)(chi)(chi) (SLA) 和(he)鎳(nie)電(dian)(dian)池(chi)(chi)(chi)等。另外，電(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)器還具有高精度的(de)(de)電(dian)(dian)流檢測(ce)功(gong)能，可(ke)為高電(dian)(dian)流應用(yong)提(ti)供較低的(de)(de)檢測(ce)電(dian)(dian)壓。

　　新式(shi)便攜(xie)產品的(de)(de)設計(ji)師從(cong)事著極富挑戰性(xing)(xing)的(de)(de)工(gong)作 ━━ 特別當其(qi)面對電(dian)(dian)(dian)源(yuan)時。客戶(hu)不斷(duan)地追逐需要消耗(hao)更(geng)多(duo)功率的(de)(de)功能(neng)，因而必需使用更(geng)大的(de)(de)電(dian)(dian)(dian)池(chi)。與此同時，客戶(hu)還希望擁(yong)有(you)從(cong)幾(ji)乎所有(you)的(de)(de)可用電(dian)(dian)(dian)源(yuan)來(lai)給這些電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)的(de)(de)便利。雖(sui)然便攜(xie)式(shi)電(dian)(dian)(dian)源(yuan)的(de)(de)上述發展(zhan)趨勢帶來(lai)了設計(ji)難(nan)題，但 LTC4155 和 LTC4000 則使設計(ji)工(gong)作大為(wei)簡化。在低電(dian)(dian)(dian)壓系統中，LTC4155 可高(gao)效提(ti)供高(gao)達(da) 3.5A 的(de)(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)流，并具有(you)諸多(duo)高(gao)性(xing)(xing)能(neng)特性(xing)(xing)。LTC4000 能(neng)夠利用幾(ji)乎任何輸入(ru)來(lai)實現一款功能(neng)強(qiang)大的(de)(de)充電(dian)(dian)(dian)解決方案，且擁(yong)有(you)無與倫比的(de)(de)性(xing)(xing)能(neng)及靈(ling)活(huo)性(xing)(xing)。