便攜式(shi)電源(yuan)應用(yong)(yong)領(ling)域(yu)寬泛而(er)多(duo)樣。產(chan)品(pin)涵蓋了(le)從平均功(gong)耗(hao)僅幾 μW 的(de)(de)無線傳感(gan)器節點到(dao)采用(yong)(yong)好幾百瓦時電池組的(de)(de)車載式(shi)醫療或數據(ju)采集系統(tong)等眾多(duo)門類。然而(er)，盡管品(pin)種繁多(duo)，但它們卻呈現出了(le)相對一(yi)(yi)致(zhi)的(de)(de)發展(zhan)趨勢(shi)(shi) ━━ 設計人員(yuan)不(bu)斷(duan)地要(yao)(yao)求(qiu)其產(chan)品(pin)擁有較高的(de)(de)功(gong)率以支持更多(duo)的(de)(de)功(gong)能，并指望能從任(ren)何可(ke)用(yong)(yong)的(de)(de)電源(yuan)來給電池充(chong)(chong)電。第(di)一(yi)(yi)個(ge)趨勢(shi)(shi)要(yao)(yao)求(qiu)增(zeng)加(jia)電池容(rong)(rong)量(liang)。不(bu)幸(xing)的(de)(de)是，用(yong)(yong)戶常常缺乏(fa)耐心，而(er)且增(zeng)加(jia)的(de)(de)電池容(rong)(rong)量(liang)必須要(yao)(yao)在合理的(de)(de)時間之(zhi)內(nei)完成充(chong)(chong)電，這(zhe)(zhe)就必然導致(zhi)充(chong)(chong)電電流的(de)(de)增(zeng)大(da)。第(di)二個(ge)趨勢(shi)(shi)則(ze)要(yao)(yao)求(qiu)電池充(chong)(chong)電解決方案具有巨大(da)的(de)(de)靈(ling)活性(xing)。我們將對這(zhe)(zhe)些問(wen)題逐(zhu)個(ge)進行(xing)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 鋰離子電池以降低電(dian)(dian)(dian)(dian)(dian)流(liu)需求(qiu)，但廉(lian)價的(de) 5V 電(dian)(dian)(dian)(dian)(dian)源(yuan)管理 IC 的(de)面市使得(de)越(yue)來越(yue)多的(de)手持式設備(bei)轉而采用較低電(dian)(dian)(dian)(dian)(dian)壓(ya)架構。平(ping)(ping)板電(dian)(dian)(dian)(dian)(dian)腦(nao)(nao)很好地體(ti)現了這(zhe)一點 ━━ 標準的(de)平(ping)(ping)板電(dian)(dian)(dian)(dian)(dian)腦(nao)(nao)擁有豐富的(de)功能以及非(fei)常大 (用于便(bian)攜式設備(bei)) 的(de)屏幕。當(dang)采用一個 3.7V 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)來供電(dian)(dian)(dian)(dian)(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)容量必(bi)須達到幾千mAh。為了能夠在幾個小時(shi)之內完成此類電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)充電(dian)(dian)(dian)(dian)(dian)，需要(yao)幾千mA的(de)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)。

　　然(ran)而，消費(fei)者同樣希(xi)望能夠在沒有可(ke)(ke)(ke)用(yong)的(de)(de)大(da)電(dian)(dian)(dian)(dian)流(liu)墻(qiang)上適(shi)配器時(shi)從(cong)一個 USB 端口來為其高(gao)功(gong)(gong)率(lv)設備充(chong)(chong)電(dian)(dian)(dian)(dian)，這種愿(yuan)望并未因為上述(shu)的(de)(de)高(gao)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)而被遏制(zhi)。為了滿足(zu)這些要求(qiu)，在可(ke)(ke)(ke)以使用(yong)墻(qiang)上適(shi)配器時(shi)，電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)器必須要能夠以高(gao)電(dian)(dian)(dian)(dian)流(liu) (>2A) 進(jin)行充(chong)(chong)電(dian)(dian)(dian)(dian)，但仍然(ran)可(ke)(ke)(ke)以高(gao)效地(di)利用(yong) USB 端口所(suo)提(ti)供(gong)的(de)(de) 2.5W 至 4.5W 功(gong)(gong)率(lv)。此(ci)外(wai)，產品(pin)還(huan)必需避免敏感的(de)(de)下游低(di)電(dian)(dian)(dian)(dian)壓(ya)組件遭受有可(ke)(ke)(ke)能造成(cheng)損壞的(de)(de)過壓(ya)，將高(gao)電(dian)(dian)(dian)(dian)流(liu)從(cong)一個 USB 輸入、一個墻(qiang)上適(shi)配器或電(dian)(dian)(dian)(dian)池無(wu)縫地(di)引導至負(fu)載，并最(zui)大(da)限(xian)度地(di)降低(di)功(gong)(gong)率(lv)損耗。與此(ci)同時(shi)，IC 必須安全(quan)地(di)管理電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)算法并監視(shi)關鍵的(de)(de)系統(tong)參數。

　　解決單(dan)節電池供電型便攜式產品(pin)的電源難題

　　盡管似乎無法找到單個 IC 來滿足(zu)上述要求，但不妨考慮一(yi)下(xia) LTC4155，這是一(yi)款高(gao)功率(lv)、I2C 控制、高(gao)效率(lv) PowerPathTM管理(li)(li)器、理(li)(li)想二(er)極管控制器和(he)鋰(li)離子電(dian)池充(chong)電(dian)器。該器件設計用(yong)于從多種 5V 電(dian)源(yuan)高(gao)效地輸送高(gao)達(da) 3A 的(de)電(dian)流(liu)，可(ke)(ke)為(wei)電(dian)池充(chong)電(dian)及系統用(yong)途提供 3.5A 以(yi)上的(de)電(dian)流(liu)。即使在(zai)這些高(gao)電(dian)流(liu)水(shui)平下(xia)，LTC4155 的(de) 88% ~ 94% 效率(lv)仍然(ran)可(ke)(ke)使熱預算限制條(tiao)件有所(suo)放寬。LTC4155 的(de)開(kai)關 PowerPath 拓撲結構可(ke)(ke)對從兩個輸入電(dian)源(yuan) (比(bi)如：墻上適(shi)配(pei)器和(he) USB 端口) 至設備的(de)可(ke)(ke)再充(chong)電(dian)鋰(li)離子電(dian)池的(de)功率(lv)輸送進(jin)行無縫管理(li)(li)，并在(zai)輸入功率(lv)有限時(shi)優先向(xiang)系統負載供電(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“即(ji)時接通”操作能(neng)力，以確保在插入電(dian)源時可(ke)立即(ji)獲得(de)系統功率，即(ji)使所采用的是一個失效的電(dian)池(chi)或深度放電(dian)的電(dian)池(chi)也不例外。

　　在對電(dian)池(chi)進行高速充(chong)電(dian)時，監視電(dian)池(chi)的(de)安全性是很重要的(de)。LTC4155 將在電(dian)池(chi)溫度(du)下降至 0℃ 以(yi)下或上升至 40℃ 以(yi)上 (由一(yi)個外部(bu)負溫度(du)系數 [NTC] 熱敏電(dian)阻負責測量(liang)) 時自動停止充(chong)電(dian)。除(chu)了(le)這種自主特性之外，LTC4155 還提供了(le)一(yi)個 7 位(wei)擴展標度(du)模數轉換器 (ADC)，用于以(yi)大約 1℃ 的(de)分辨率來(lai)監視電(dian)池(chi)的(de)溫度(du)。結合(he) 4 種可(ke)用的(de)浮置電(dian)壓設定值和 15 種電(dian)池(chi)充(chong)電(dian)電(dian)流設定值，該(gai) ADC 能(neng)夠用于建立基于電(dian)池(chi)溫度(du)的(de)定制(zhi)充(chong)電(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)和故障狀態(tai)。USB OTG (On-The-Go) 支持能(neng)力可在未采用任何附(fu)加組(zu)件的情況下提供一(yi)個返回 USB 端(duan)口的 5V 電(dian)源。

　　LTC4155 的雙輸(shu)入、優(you)先級多路(lu)復(fu)用器(qi)(qi)可(ke)根據用戶定義的優(you)先級 (適配器(qi)(qi)輸(shu)入是(shi)默認的優(you)先選(xuan)(xuan)擇) 自主選(xuan)(xuan)擇最合適的輸(shu)入 (墻(qiang)上適配器(qi)(qi)或 USB)。過壓保護 (OVP) 電(dian)路(lu)用于同時(shi)保護兩個輸(shu)入免遭(zao)因意外施加高電(dian)壓或反(fan)向(xiang)電(dian)壓而造成的損壞。LTC4155 的理想二(er)極(ji)管控制器(qi)(qi)可(ke)確(que)保始終能(neng)夠向(xiang) VOUT 提供足夠的功(gong)率，即使輸(shu)入功(gong)率不足或缺失也不例外。

　　對于(yu)諸(zhu)如(ru)平板電(dian)腦或工(gong)業條形碼(ma)掃描儀(yi)等許多便(bian)攜式應用而言，管理兩個輸入 (例如(ru)：USB和墻上適配器) 就足夠了。不過(guo)，便(bian)攜式設(she)備的設(she)計人員(yuan)仍在(zai)繼續(xu)探尋能(neng)夠從任何可(ke)用電(dian)源來給(gei)電(dian)池充(chong)電(dian)的方法。

　　多種輸入電源

　　諸多(duo)原因導(dao)致用戶希(xi)望(wang)(wang)從多(duo)種輸(shu)入電(dian)(dian)(dian)(dian)(dian)源來(lai)給(gei)(gei)(gei)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。某(mou)些應(ying)用有(you)可能需要脫離電(dian)(dian)(dian)(dian)(dian)網并指望(wang)(wang)由太陽能板來(lai)供電(dian)(dian)(dian)(dian)(dian)。其他的(de)(de)應(ying)用則希(xi)望(wang)(wang)擁有(you)能夠從墻(qiang)上適配(pei)器(qi)(qi)(qi)、汽車電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)或(huo)者高電(dian)(dian)(dian)(dian)(dian)壓(ya)工業或(huo)電(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)源進(jin)行充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)便(bian)利(li)。不管(guan)是什么(me)原因，這種要求都給(gei)(gei)(gei)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)系(xi)統施加了(le)一個沉重的(de)(de)負擔(dan)。大(da)(da)多(duo)數電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)均利(li)用一種降壓(ya) (開關或(huo)線性) 架構從一個高于(yu)最大(da)(da)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)電(dian)(dian)(dian)(dian)(dian)源來(lai)給(gei)(gei)(gei)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。早先的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)產品(pin)通常(chang)被限(xian)制(zhi)于(yu)大(da)(da)約 30V 的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)壓(ya)。此類(lei)局限(xian)性導(dao)致設計(ji)人員(yuan)無法考慮將電(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)源作為可行的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)源，或(huo)者采用具有(you) 42V 開路(lu)電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)太陽能板。在某(mou)些場合(he)中，期望(wang)(wang)輸(shu)入電(dian)(dian)(dian)(dian)(dian)源的(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)范圍既會(hui)升至(zhi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)以上也(ye)會(hui)降至(zhi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)以下。設計(ji)旨在應(ying)對上述(shu)難題(ti)的(de)(de)解(jie)決方案(an)通常(chang)需要整合(he)高精度的(de)(de)電(dian)(dian)(dian)(dian)(dian)流檢測放(fang)大(da)(da)器(qi)(qi)(qi)、ADC、用于(yu)控制(zhi)充(chong)電(dian)(dian)(dian)(dian)(dian)操作的(de)(de)微處理器(qi)(qi)(qi)、高性能的(de)(de) DC/DC 轉換器(qi)(qi)(qi)以及理想二極管(guan)或(huo)多(duo)路(lu)復用電(dian)(dian)(dian)(dian)(dian)路(lu)。凌力爾特公司(si)推出了(le)一款更(geng)加優越(yue)的(de)(de)解(jie)決方案(an)。

　　功能強大(da)且擁有無可(ke)比擬之靈活(huo)性的充電解決(jue)方案(an)

　　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 控制功能。LTC4000 能夠(gou)驅(qu)動的常用DC/DC 轉換器(qi)(qi)拓撲結(jie)構包括(kuo) (但不限于) 降壓(ya)(ya)、升(sheng)壓(ya)(ya)、降壓(ya)(ya)-升(sheng)壓(ya)(ya)、SEPIC 和反激式。該器(qi)(qi)件提供了精準的輸入(ru)電(dian)(dian)(dian)流和充電(dian)(dian)(dian)電(dian)(dian)(dian)流調(diao)節，并可在(zai)一個(ge) 3V 至 60V 的寬(kuan)輸入(ru)和輸出電(dian)(dian)(dian)壓(ya)(ya)范圍內運(yun)作(zuo)，因(yin)而(er)與多種不同的輸入(ru)電(dian)(dian)(dian)壓(ya)(ya)電(dian)(dian)(dian)源、電(dian)(dian)(dian)池(chi)組(zu)(zu)尺寸(cun)和化(hua)學組(zu)(zu)成相(xiang)兼容。由(you)于這款器(qi)(qi)件采用了通(tong)用型配置，因(yin)此其典型應用范圍十分廣泛(fan)，包括(kuo)高(gao)功率電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器(qi)(qi)系(xi)統、高(gao)性能便攜式儀器(qi)(qi)、電(dian)(dian)(dian)池(chi)后備系(xi)統、配備電(dian)(dian)(dian)池(chi)的工業(ye)設備以及筆(bi)記本電(dian)(dian)(dian)腦(nao) / 小型筆(bi)記本電(dian)(dian)(dian)腦(nao)等。

　　除了可(ke)(ke)支(zhi)持多種不同的(de)(de)(de)(de)(de)(de) DC/DC 拓(tuo)撲(pu)結(jie)構(gou)之外，LTC4000 的(de)(de)(de)(de)(de)(de)高電(dian)(dian)(dian)(dian)壓(ya)能(neng)(neng)力(li)還(huan)使(shi)其能(neng)(neng)夠利(li)用幾乎任何輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)源(yuan)來形成(cheng)功(gong)能(neng)(neng)強大的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)解決(jue)方案。為了確保來自這(zhe)些輸(shu)(shu)入(ru)的(de)(de)(de)(de)(de)(de)功(gong)率(lv)能(neng)(neng)輸(shu)(shu)送至合適(shi)的(de)(de)(de)(de)(de)(de)負載(zai)，LTC4000采(cai)用了一(yi)種智能(neng)(neng) PowerPathTM 拓(tuo)撲(pu)結(jie)構(gou)，當輸(shu)(shu)入(ru)功(gong)率(lv)有限時，該拓(tuo)撲(pu)結(jie)構(gou)將優先向系統負載(zai)供(gong)電(dian)(dian)(dian)(dian)。LTC4000 通(tong)過控制外部 PFET 來提(ti)供(gong)低損耗反向電(dian)(dian)(dian)(dian)流保護、電(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)(de)(de)低損耗充(chong)電(dian)(dian)(dian)(dian)和放電(dian)(dian)(dian)(dian)以及“即(ji)時接通(tong)型”操作(zuo)，以確保在(zai)插入(ru)電(dian)(dian)(dian)(dian)源(yuan)時可(ke)(ke)立即(ji)獲(huo)得系統功(gong)率(lv)，即(ji)使(shi)所采(cai)用的(de)(de)(de)(de)(de)(de)是一(yi)個失(shi)效的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)池(chi)或深度放電(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)池(chi)也(ye)不例外。外部檢測電(dian)(dian)(dian)(dian)阻器可(ke)(ke)提(ti)供(gong)輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)流和電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流信息，從而使(shi)得 LTC4000 能(neng)(neng)夠與(yu)功(gong)率(lv)范(fan)圍從幾毫瓦到(dao)幾千瓦的(de)(de)(de)(de)(de)(de)轉(zhuan)換器一(yi)起使(shi)用。

　　LTC4000 的(de)全功能(neng)電(dian)(dian)池充(chong)(chong)電(dian)(dian)控制器(qi)可對多種電(dian)(dian)池化學組成進(jin)行(xing)充(chong)(chong)電(dian)(dian)，包括(kuo)鋰離子電(dian)(dian)池 / 鋰聚合物(wu)電(dian)(dian)池 / 磷酸(suan)鐵鋰電(dian)(dian)池、密封鉛酸(suan)電(dian)(dian)池 (SLA) 和鎳電(dian)(dian)池等。另(ling)外，電(dian)(dian)池充(chong)(chong)電(dian)(dian)器(qi)還具有高精度的(de)電(dian)(dian)流(liu)檢測功能(neng)，可為(wei)高電(dian)(dian)流(liu)應(ying)用提供較低的(de)檢測電(dian)(dian)壓(ya)。

　　新式便(bian)攜產品的(de)(de)設計(ji)師(shi)從事(shi)著極富挑戰性(xing)(xing)的(de)(de)工(gong)(gong)作 ━━ 特(te)別當(dang)其面對電(dian)(dian)源時。客(ke)戶不斷(duan)地追逐需要消耗更多(duo)功率(lv)的(de)(de)功能(neng)，因而(er)必需使(shi)用更大(da)的(de)(de)電(dian)(dian)池。與此同時，客(ke)戶還希望擁(yong)有從幾乎所有的(de)(de)可用電(dian)(dian)源來給這些(xie)電(dian)(dian)池充(chong)電(dian)(dian)的(de)(de)便(bian)利。雖然便(bian)攜式電(dian)(dian)源的(de)(de)上(shang)述發(fa)展(zhan)趨勢帶來了設計(ji)難(nan)題，但 LTC4155 和 LTC4000 則使(shi)設計(ji)工(gong)(gong)作大(da)為簡化。在低(di)電(dian)(dian)壓系(xi)統中，LTC4155 可高效(xiao)提(ti)供高達(da) 3.5A 的(de)(de)充(chong)電(dian)(dian)電(dian)(dian)流，并具有諸(zhu)多(duo)高性(xing)(xing)能(neng)特(te)性(xing)(xing)。LTC4000 能(neng)夠(gou)利用幾乎任(ren)何輸(shu)入來實現一款功能(neng)強大(da)的(de)(de)充(chong)電(dian)(dian)解決方案，且擁(yong)有無與倫比的(de)(de)性(xing)(xing)能(neng)及(ji)靈活性(xing)(xing)。