便(bian)攜式電源應用領域(yu)寬(kuan)泛而(er)多樣。產(chan)品(pin)涵蓋了從(cong)平均功(gong)耗僅幾 μW 的無線(xian)傳(chuan)感器節點到采用好幾百瓦(wa)時(shi)電池(chi)(chi)組的車載(zai)式醫療(liao)或數據采集系統等眾多門(men)類。然(ran)而(er)，盡管品(pin)種繁多，但它(ta)們(men)卻(que)呈現出(chu)了相對(dui)一致的發展(zhan)趨(qu)勢(shi) ━━ 設(she)計人員(yuan)不斷地要(yao)求其產(chan)品(pin)擁有(you)較(jiao)高的功(gong)率以支持(chi)更(geng)多的功(gong)能，并指望能從(cong)任(ren)何可用的電源來給(gei)電池(chi)(chi)充電。第一個(ge)趨(qu)勢(shi)要(yao)求增加(jia)電池(chi)(chi)容(rong)量(liang)。不幸的是，用戶常(chang)常(chang)缺(que)乏耐心，而(er)且(qie)增加(jia)的電池(chi)(chi)容(rong)量(liang)必須(xu)要(yao)在合理的時(shi)間之內完成充電，這(zhe)就必然(ran)導(dao)致充電電流的增大。第二個(ge)趨(qu)勢(shi)則要(yao)求電池(chi)(chi)充電解決方(fang)案具有(you)巨大的靈活性。我們(men)將對(dui)這(zhe)些問題(ti)逐個(ge)進行較(jiao)為詳細的探究。

　　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 鋰離子電池以降低電(dian)(dian)(dian)(dian)流需求，但廉價的(de)(de) 5V 電(dian)(dian)(dian)(dian)源管理 IC 的(de)(de)面市(shi)使得越來(lai)越多的(de)(de)手持式設(she)(she)備轉而采用較低電(dian)(dian)(dian)(dian)壓架構。平板電(dian)(dian)(dian)(dian)腦很(hen)好地體現(xian)了(le)這一(yi)點 ━━ 標(biao)準的(de)(de)平板電(dian)(dian)(dian)(dian)腦擁(yong)有豐富的(de)(de)功能(neng)以及非常大 (用于便攜式設(she)(she)備) 的(de)(de)屏(ping)幕。當(dang)采用一(yi)個 3.7V 電(dian)(dian)(dian)(dian)池來(lai)供電(dian)(dian)(dian)(dian)時，電(dian)(dian)(dian)(dian)池的(de)(de)容量必(bi)須達到幾(ji)千mAh。為了(le)能(neng)夠在幾(ji)個小時之(zhi)內完成此類電(dian)(dian)(dian)(dian)池的(de)(de)充電(dian)(dian)(dian)(dian)，需要幾(ji)千mA的(de)(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流。

　　然而，消費者同樣希望能(neng)夠(gou)在沒有可(ke)用的大(da)(da)電(dian)(dian)(dian)流(liu)(liu)墻(qiang)上(shang)(shang)適(shi)配(pei)器(qi)(qi)時從一個 USB 端(duan)口來為其高(gao)(gao)功(gong)率設備充電(dian)(dian)(dian)，這(zhe)種愿望并未因(yin)為上(shang)(shang)述的高(gao)(gao)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)而被遏制。為了滿足這(zhe)些要求，在可(ke)以(yi)使用墻(qiang)上(shang)(shang)適(shi)配(pei)器(qi)(qi)時，電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器(qi)(qi)必須要能(neng)夠(gou)以(yi)高(gao)(gao)電(dian)(dian)(dian)流(liu)(liu) (>2A) 進(jin)行充電(dian)(dian)(dian)，但仍然可(ke)以(yi)高(gao)(gao)效地利用 USB 端(duan)口所(suo)提供的 2.5W 至 4.5W 功(gong)率。此外，產(chan)品(pin)還必需避免敏感的下(xia)游低(di)電(dian)(dian)(dian)壓(ya)組件遭受(shou)有可(ke)能(neng)造成損壞的過(guo)壓(ya)，將高(gao)(gao)電(dian)(dian)(dian)流(liu)(liu)從一個 USB 輸入、一個墻(qiang)上(shang)(shang)適(shi)配(pei)器(qi)(qi)或電(dian)(dian)(dian)池(chi)無縫地引導(dao)至負載，并最(zui)大(da)(da)限度地降低(di)功(gong)率損耗。與(yu)此同時，IC 必須安全地管(guan)理電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)算(suan)法(fa)并監(jian)視關鍵的系統參數。

　　解決(jue)單(dan)節電(dian)(dian)池(chi)供電(dian)(dian)型便(bian)攜式產品的電(dian)(dian)源難題(ti)

　　盡管似乎(hu)無法找到單(dan)個(ge) IC 來滿(man)足(zu)上(shang)(shang)述要求，但不妨考慮一(yi)下(xia)(xia) LTC4155，這是一(yi)款高(gao)功率、I2C 控(kong)制(zhi)、高(gao)效(xiao)率 PowerPathTM管理器(qi)(qi)、理想(xiang)二極管控(kong)制(zhi)器(qi)(qi)和鋰離子電(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)器(qi)(qi)。該器(qi)(qi)件(jian)設計用于從多種 5V 電(dian)(dian)源高(gao)效(xiao)地(di)輸(shu)送(song)(song)高(gao)達 3A 的電(dian)(dian)流，可為電(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)及系(xi)統用途提供(gong) 3.5A 以上(shang)(shang)的電(dian)(dian)流。即使在這些高(gao)電(dian)(dian)流水平下(xia)(xia)，LTC4155 的 88% ~ 94% 效(xiao)率仍然(ran)可使熱預算限制(zhi)條件(jian)有(you)所放寬。LTC4155 的開關 PowerPath 拓撲(pu)結構(gou)可對從兩個(ge)輸(shu)入(ru)電(dian)(dian)源 (比如：墻上(shang)(shang)適配器(qi)(qi)和 USB 端口(kou)) 至設備的可再充(chong)(chong)電(dian)(dian)鋰離子電(dian)(dian)池(chi)的功率輸(shu)送(song)(song)進行無縫管理，并在輸(shu)入(ru)功率有(you)限時優先(xian)向系(xi)統負(fu)載供(gong)電(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(bu)同，LTC4155 具(ju)有(you)“即(ji)時接通(tong)”操(cao)作(zuo)能力，以確保在插(cha)入電(dian)(dian)源時可立即(ji)獲得(de)系統功率，即(ji)使所采用的(de)是一(yi)個失效的(de)電(dian)(dian)池或深度(du)放電(dian)(dian)的(de)電(dian)(dian)池也不(bu)例(li)外。

　　在對電(dian)(dian)池(chi)(chi)進行高速充電(dian)(dian)時(shi)，監(jian)視電(dian)(dian)池(chi)(chi)的(de)安全性(xing)(xing)是很重要(yao)的(de)。LTC4155 將(jiang)在電(dian)(dian)池(chi)(chi)溫(wen)(wen)度(du)下(xia)降至 0℃ 以(yi)(yi)(yi)下(xia)或上升至 40℃ 以(yi)(yi)(yi)上 (由一(yi)個外(wai)部負溫(wen)(wen)度(du)系數(shu)(shu) [NTC] 熱敏(min)電(dian)(dian)阻負責測量(liang)) 時(shi)自(zi)動停止(zhi)充電(dian)(dian)。除了(le)這種(zhong)自(zi)主(zhu)特性(xing)(xing)之(zhi)外(wai)，LTC4155 還提(ti)供了(le)一(yi)個 7 位擴展標度(du)模(mo)數(shu)(shu)轉換器 (ADC)，用(yong)(yong)(yong)于(yu)以(yi)(yi)(yi)大約 1℃ 的(de)分辨率來監(jian)視電(dian)(dian)池(chi)(chi)的(de)溫(wen)(wen)度(du)。結合 4 種(zhong)可(ke)用(yong)(yong)(yong)的(de)浮置電(dian)(dian)壓設定(ding)值和 15 種(zhong)電(dian)(dian)池(chi)(chi)充電(dian)(dian)電(dian)(dian)流設定(ding)值，該 ADC 能夠用(yong)(yong)(yong)于(yu)建(jian)立基于(yu)電(dian)(dian)池(chi)(chi)溫(wen)(wen)度(du)的(de)定(ding)制充電(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(zhuang)(zhuang)態和故障(zhang)狀(zhuang)(zhuang)態。USB OTG (On-The-Go) 支(zhi)持能(neng)力可在未采(cai)用(yong)任何附(fu)加組件的情況下提供一個(ge)返回 USB 端口的 5V 電(dian)源(yuan)。

　　LTC4155 的(de)雙(shuang)輸(shu)入(ru)、優(you)(you)先級多(duo)路(lu)復用(yong)器(qi)(qi)可根據用(yong)戶定義的(de)優(you)(you)先級 (適(shi)配(pei)器(qi)(qi)輸(shu)入(ru)是默認的(de)優(you)(you)先選(xuan)擇) 自主(zhu)選(xuan)擇最合適(shi)的(de)輸(shu)入(ru) (墻(qiang)上適(shi)配(pei)器(qi)(qi)或(huo) USB)。過(guo)壓保(bao)護(hu) (OVP) 電路(lu)用(yong)于同時保(bao)護(hu)兩個輸(shu)入(ru)免遭因意外施(shi)加高電壓或(huo)反向電壓而造成的(de)損壞。LTC4155 的(de)理想二極管控(kong)制器(qi)(qi)可確保(bao)始終能夠向 VOUT 提供(gong)足(zu)(zu)夠的(de)功(gong)(gong)率，即使輸(shu)入(ru)功(gong)(gong)率不足(zu)(zu)或(huo)缺失也不例外。

　　對于諸如平板電(dian)腦或(huo)工業條形碼掃描儀等許多便(bian)攜(xie)(xie)式應用而言，管(guan)理兩(liang)個輸入(ru) (例如：USB和墻上適配器) 就足(zu)夠了。不過，便(bian)攜(xie)(xie)式設備的設計人員仍(reng)在繼續(xu)探尋能(neng)夠從任何可(ke)用電(dian)源來給電(dian)池(chi)充(chong)電(dian)的方法。

　　多種輸入電源

　　諸多(duo)(duo)原因(yin)導(dao)(dao)致用(yong)(yong)(yong)戶希望(wang)從(cong)多(duo)(duo)種輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。某些應用(yong)(yong)(yong)有(you)可(ke)能需要(yao)脫離電(dian)(dian)(dian)(dian)(dian)(dian)網并指(zhi)望(wang)由(you)太陽能板(ban)(ban)來供電(dian)(dian)(dian)(dian)(dian)(dian)。其他的(de)(de)應用(yong)(yong)(yong)則希望(wang)擁(yong)有(you)能夠從(cong)墻上(shang)適配(pei)器、汽車電(dian)(dian)(dian)(dian)(dian)(dian)池或(huo)者(zhe)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)工業(ye)或(huo)電(dian)(dian)(dian)(dian)(dian)(dian)信電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)進行充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)便利(li)。不(bu)管(guan)是什么原因(yin)，這種要(yao)求都給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)系統施加(jia)了一(yi)個(ge)沉重的(de)(de)負擔。大多(duo)(duo)數(shu)電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器均利(li)用(yong)(yong)(yong)一(yi)種降壓(ya)(ya) (開關或(huo)線(xian)性(xing)(xing)) 架(jia)構從(cong)一(yi)個(ge)高(gao)于(yu)最(zui)大電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。早先的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器產品通常被限(xian)制于(yu)大約 30V 的(de)(de)輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。此類局限(xian)性(xing)(xing)導(dao)(dao)致設計(ji)人員無法考慮將電(dian)(dian)(dian)(dian)(dian)(dian)信電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)作為可(ke)行的(de)(de)輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，或(huo)者(zhe)采用(yong)(yong)(yong)具有(you) 42V 開路電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)太陽能板(ban)(ban)。在某些場合(he)中，期望(wang)輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)范(fan)圍既會升至電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以上(shang)也會降至電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以下。設計(ji)旨在應對上(shang)述難題的(de)(de)解(jie)決(jue)方(fang)案通常需要(yao)整合(he)高(gao)精(jing)度的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)檢測放大器、ADC、用(yong)(yong)(yong)于(yu)控制充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)操作的(de)(de)微處(chu)理(li)器、高(gao)性(xing)(xing)能的(de)(de) DC/DC 轉換(huan)器以及理(li)想二(er)極管(guan)或(huo)多(duo)(duo)路復用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)路。凌力(li)爾特公(gong)司推(tui)出了一(yi)款更加(jia)優越(yue)的(de)(de)解(jie)決(jue)方(fang)案。

　　功(gong)能強大且擁有無可比擬(ni)之(zhi)靈(ling)活性(xing)的充電(dian)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(you) PowerPathTM 控制功能(neng)。LTC4000 能(neng)夠驅動的(de)常(chang)用DC/DC 轉換器(qi)(qi)拓撲結構包(bao)括 (但不限于) 降壓(ya)、升壓(ya)、降壓(ya)-升壓(ya)、SEPIC 和(he)反激(ji)式。該器(qi)(qi)件(jian)提供了(le)精準的(de)輸入(ru)(ru)電(dian)(dian)(dian)流和(he)充電(dian)(dian)(dian)電(dian)(dian)(dian)流調節，并可(ke)在(zai)一個 3V 至 60V 的(de)寬輸入(ru)(ru)和(he)輸出電(dian)(dian)(dian)壓(ya)范圍內運作(zuo)，因(yin)而(er)與多種不同的(de)輸入(ru)(ru)電(dian)(dian)(dian)壓(ya)電(dian)(dian)(dian)源、電(dian)(dian)(dian)池(chi)組尺寸和(he)化(hua)學組成(cheng)相(xiang)兼(jian)容(rong)。由于這款器(qi)(qi)件(jian)采用了(le)通用型(xing)配置，因(yin)此其典型(xing)應用范圍十分廣泛，包(bao)括高功率電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器(qi)(qi)系(xi)(xi)統(tong)、高性(xing)能(neng)便攜式儀器(qi)(qi)、電(dian)(dian)(dian)池(chi)后備系(xi)(xi)統(tong)、配備電(dian)(dian)(dian)池(chi)的(de)工(gong)業設備以及筆記(ji)本電(dian)(dian)(dian)腦(nao) / 小型(xing)筆記(ji)本電(dian)(dian)(dian)腦(nao)等(deng)。

　　除(chu)了(le)可(ke)支持多種(zhong)不同的(de) DC/DC 拓(tuo)(tuo)撲(pu)結構之外(wai)(wai)，LTC4000 的(de)高電(dian)壓能(neng)(neng)力(li)還使其能(neng)(neng)夠利(li)用(yong)幾乎任何輸(shu)入(ru)(ru)電(dian)源(yuan)來形成功(gong)能(neng)(neng)強(qiang)大的(de)電(dian)池充電(dian)解決方案。為(wei)了(le)確(que)保(bao)來自(zi)這些輸(shu)入(ru)(ru)的(de)功(gong)率能(neng)(neng)輸(shu)送至(zhi)合(he)適(shi)的(de)負載，LTC4000采用(yong)了(le)一種(zhong)智(zhi)能(neng)(neng) PowerPathTM 拓(tuo)(tuo)撲(pu)結構，當輸(shu)入(ru)(ru)功(gong)率有限時，該拓(tuo)(tuo)撲(pu)結構將優先向系統負載供(gong)電(dian)。LTC4000 通過控(kong)制外(wai)(wai)部 PFET 來提供(gong)低損耗(hao)反(fan)向電(dian)流(liu)保(bao)護、電(dian)池的(de)低損耗(hao)充電(dian)和放(fang)電(dian)以及(ji)“即時接(jie)通型”操作，以確(que)保(bao)在(zai)插入(ru)(ru)電(dian)源(yuan)時可(ke)立即獲得系統功(gong)率，即使所采用(yong)的(de)是一個失效的(de)電(dian)池或深度放(fang)電(dian)的(de)電(dian)池也不例外(wai)(wai)。外(wai)(wai)部檢測電(dian)阻器(qi)可(ke)提供(gong)輸(shu)入(ru)(ru)電(dian)流(liu)和電(dian)池充電(dian)電(dian)流(liu)信息，從而使得 LTC4000 能(neng)(neng)夠與功(gong)率范圍從幾毫瓦到幾千瓦的(de)轉(zhuan)換器(qi)一起使用(yong)。

　　LTC4000 的(de)全功(gong)能電(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)控制(zhi)器可對多種電(dian)(dian)(dian)(dian)(dian)池化學組成進行充電(dian)(dian)(dian)(dian)(dian)，包括鋰(li)離子電(dian)(dian)(dian)(dian)(dian)池 / 鋰(li)聚合物電(dian)(dian)(dian)(dian)(dian)池 / 磷酸鐵鋰(li)電(dian)(dian)(dian)(dian)(dian)池、密(mi)封鉛酸電(dian)(dian)(dian)(dian)(dian)池 (SLA) 和鎳電(dian)(dian)(dian)(dian)(dian)池等。另外，電(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)器還具有(you)高精度的(de)電(dian)(dian)(dian)(dian)(dian)流檢(jian)測功(gong)能，可為高電(dian)(dian)(dian)(dian)(dian)流應用提供(gong)較(jiao)低的(de)檢(jian)測電(dian)(dian)(dian)(dian)(dian)壓。

　　新式便(bian)攜產品(pin)的(de)設計師從事著(zhu)極富挑戰性的(de)工(gong)作 ━━ 特(te)別(bie)當其面對電(dian)(dian)源時。客(ke)戶不(bu)斷地追逐需要消耗更多(duo)功(gong)率的(de)功(gong)能，因而必需使用更大的(de)電(dian)(dian)池。與(yu)此同時，客(ke)戶還希望擁(yong)有從幾(ji)乎(hu)所有的(de)可用電(dian)(dian)源來給這些電(dian)(dian)池充電(dian)(dian)的(de)便(bian)利。雖然便(bian)攜式電(dian)(dian)源的(de)上述(shu)發展(zhan)趨(qu)勢帶來了設計難題，但 LTC4155 和 LTC4000 則使設計工(gong)作大為簡化。在低電(dian)(dian)壓系(xi)統中，LTC4155 可高效提供(gong)高達 3.5A 的(de)充電(dian)(dian)電(dian)(dian)流(liu)，并具有諸多(duo)高性能特(te)性。LTC4000 能夠(gou)利用幾(ji)乎(hu)任何輸入來實現一款(kuan)功(gong)能強(qiang)大的(de)充電(dian)(dian)解決方案，且擁(yong)有無與(yu)倫比的(de)性能及靈活性。