鑒于市場上鎳鎘電池和鋰電池共存的局面，本文設計的充電器可以對這兩種電(dian)池(chi)(chi)進(jin)行充(chong)(chong)電(dian)，對鎳鎘電(dian)池(chi)(chi)組(zu)(zu)采用脈沖充(chong)(chong)電(dian)方式，對鋰(li)電(dian)池(chi)(chi)組(zu)(zu)采用恒流充(chong)(chong)電(dian)方式，這是依據電(dian)池(chi)(chi)的(de)不同機(ji)理而設(she)計(ji)的(de)，真正(zheng)做到(dao)了一(yi)機(ji)兩用，此(ci)為(wei)該充(chong)(chong)電(dian)器(qi)的(de)創新點(dian)，也(ye)是設(she)計(ji)的(de)難點(dian)。充(chong)(chong)電(dian)器(qi)的(de)寬屏(ping)LCD可以同時(shi)顯示(shi)4組(zu)(zu)充(chong)(chong)電(dian)器(qi)的(de)充(chong)(chong)電(dian)狀態，也(ye)可單(dan)獨顯示(shi)一(yi)組(zu)(zu)充(chong)(chong)電(dian)器(qi)上電(dian)池(chi)(chi)的(de)各項參數(shu)，做到(dao)了對電(dian)池(chi)(chi)充(chong)(chong)電(dian)過程的(de)實時(shi)監測。

　　系統整體設計

　　系統設計目標是：

　　1．可(ke)同時(shi)對4組8.4V的鋰離子(zi)電(dian)(dian)池或9.2V的鎳鎘電(dian)(dian)池進行(xing)充放電(dian)(dian)。

　　2．可(ke)與電(dian)池組中的(de)芯片(pian)通信，判斷電(dian)池的(de)化學性質。

　　3．對于不(bu)同化(hua)學性質的(de)電池，將采(cai)用相應的(de)充電方(fang)式(shi)。

　　4．可與(yu)電池(chi)組中(zhong)的芯片(pian)通信，得到(dao)該(gai)電池(chi)組的電壓、充電電流(liu)、容(rong)量等參數。

　　5．充電(dian)器帶有LCD，可顯示電(dian)池的各(ge)項數據。

    系統硬(ying)件設計

　　總控單元的設計與實現

　　總控(kong)單(dan)(dan)元(yuan)(yuan)是由微(wei)控(kong)制(zhi)器PIC16F873和鍵盤控(kong)制(zhi)芯片(pian)ZLG7289A構成的。主要任務是負責(ze)(ze)與(yu)各個(ge)充(chong)(chong)電(dian)(dian)(dian)(dian)單(dan)(dan)元(yuan)(yuan)通(tong)信(xin)，并(bing)處理用(yong)戶(hu)輸入與(yu)LCD顯示信(xin)息。鍵盤控(kong)制(zhi)芯片(pian)在(zai)這(zhe)里負責(ze)(ze)6個(ge)按鍵和12個(ge)LED的控(kong)制(zhi)。ZLG7289A與(yu)微(wei)控(kong)制(zhi)器之間通(tong)過SPI總線進行雙(shuang)向通(tong)信(xin)。主控(kong)單(dan)(dan)元(yuan)(yuan)每秒(miao)查詢一次各個(ge)充(chong)(chong)電(dian)(dian)(dian)(dian)單(dan)(dan)元(yuan)(yuan)，獲取當(dang)前充(chong)(chong)電(dian)(dian)(dian)(dian)單(dan)(dan)元(yuan)(yuan)的信(xin)息，如有無電(dian)(dian)(dian)(dian)池(chi)、電(dian)(dian)(dian)(dian)池(chi)性質、電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓等。之后由LCD模塊向用(yong)戶(hu)顯示。

　　充電(dian)單(dan)元的設(she)計與實現

　　LTC4002鋰離子電(dian)池充電(dian)控制芯(xin)片

　　LTC4002是一款(kuan)高效獨(du)立(li)開關模(mo)式(shi)鋰離子(zi)電(dian)池充(chong)(chong)電(dian)控(kong)(kong)制器(qi)(qi)。該控(kong)(kong)制器(qi)(qi)有4.2V和8.4V兩個(ge)版本。LTC4002-8.4具有500kHz開關頻率(lv)，是高效電(dian)流模(mo)式(shi)的(de)PWM控(kong)(kong)制器(qi)(qi)。通過驅動一個(ge)外部P溝道MOSFET，它(ta)可以提(ti)供4A的(de)充(chong)(chong)電(dian)電(dian)流，而(er)效率(lv)可高達90％。輸出電(dian)壓設置為(wei)8.4V，最終浮(fu)動電(dian)壓并具1％的(de)精度，而(er)充(chong)(chong)電(dian)準確(que)度為(wei)5％。此外，該器(qi)(qi)件可在9V～22V范圍內的(de)多種墻上(shang)適配器(qi)(qi)上(shang)運行(xing)(xing)。與遲(chi)滯拓撲結構充(chong)(chong)電(dian)器(qi)(qi)相比，LTC4002-8.4的(de)快速運行(xing)(xing)頻率(lv)與電(dian)流模(mo)式(shi)架構使之能夠使用小型電(dian)感器(qi)(qi)和電(dian)容器(qi)(qi)。

　　鋰離子／鎳鎘(ge)電(dian)池兩用充電(dian)單(dan)元的總體設計

　　從前面對LTC4002的分析可知，該芯片是針對鋰離子電池的充電控制器，要實現對鎳鎘電池充電需要解決以下問題：首先，LTC4002對電池電壓進行監測，保證電池電壓不超過8.4V。但對于鎳鎘電池組，充電截止電壓可以達到9.2V。其次，鎳鎘電池充電即將結束時，需要對電池進行以正常電流30％和10％的涓流充電。所以，第二個需要解決的問題是如何控制恒流充電的電流大小。此外，對鎳鎘電池充電應使用脈沖充電方式。即以1s為周期，95％的時間用來充電，1％的時間用來放電，其余時間不充電也不放電。最后，如何判斷某一個電池是鋰離子電池還是(shi)鎳(nie)鎘電(dian)(dian)(dian)池，因(yin)為若把鋰離(li)子(zi)(zi)電(dian)(dian)(dian)池誤(wu)判(pan)為鎳(nie)鎘電(dian)(dian)(dian)池，會使充電(dian)(dian)(dian)電(dian)(dian)(dian)壓高于8.4V，這對鋰離(li)子(zi)(zi)電(dian)(dian)(dian)池是(shi)十分危險的，而將鎳(nie)鎘電(dian)(dian)(dian)池誤(wu)判(pan)為鋰離(li)子(zi)(zi)電(dian)(dian)(dian)池，則(ze)可能造成電(dian)(dian)(dian)池充電(dian)(dian)(dian)不(bu)足(zu)。因(yin)此(ci)，必須(xu)保證極低的誤(wu)判(pan)率。

　　本部分根據LTC4002的工作原理，設計了既可以對鋰離子電池進行恒流-恒壓充電，又可以對鎳鎘電池進行脈沖式充電的電路。充電單元的總體功能框圖如圖2所示。其中，信號調理電路使充電器既可以(yi)對(dui)8.4V的鋰電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)，又可以(yi)對(dui)9.2V的鎳鎘電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)，同時也起到控制充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流大小的作用。

　　利用微控制器控制LTC4002的工作狀態，配合放電電路使充電器可(ke)以對鎳鎘電(dian)池(chi)進行脈沖方式(shi)充電(dian)。

　　微控制器通過一定的通信協議(HDQ16)與智能電池通信，確(que)定其(qi)容量、化學性質等關鍵參(can)數(shu)。

　　信號(hao)調理電路的設計

　　為了使LTC4002可對(dui)高于8.4V的電(dian)(dian)池(chi)進行恒流(liu)充(chong)電(dian)(dian)，并可調(diao)節(jie)充(chong)電(dian)(dian)電(dian)(dian)流(liu)，在LTC4002的BAT和SENSE端(duan)與采(cai)樣電(dian)(dian)阻(zu)之間加(jia)入一級(ji)信(xin)(xin)號調(diao)理電(dian)(dian)路。該電(dian)(dian)路的主要(yao)功(gong)能(neng)是對(dui)采(cai)樣電(dian)(dian)阻(zu)兩端(duan)的信(xin)(xin)號進行運算，針(zhen)對(dui)不(bu)同(tong)化(hua)學性質的電(dian)(dian)池(chi)，將相應的信(xin)(xin)號送給LTC4002。該信(xin)(xin)號調(diao)理電(dian)(dian)路如圖3所示。

 　這里定(ding)義采樣電(dian)(dian)阻(zu)兩(liang)(liang)端(duan)的(de)(de)電(dian)(dian)壓值(zhi)是VBAT和Vsense，那(nei)么(me)(me)充(chong)電(dian)(dian)電(dian)(dian)流在采樣電(dian)(dian)阻(zu)上的(de)(de)壓降VRS為(wei)(wei)：VRS=Vsense-VBAT，該信號為(wei)(wei)減法(fa)器(qi)的(de)(de)輸(shu)出(chu)(chu)。設乘(cheng)法(fa)器(qi)的(de)(de)乘(cheng)系數為(wei)(wei)K，那(nei)么(me)(me)乘(cheng)法(fa)器(qi)的(de)(de)輸(shu)出(chu)(chu)為(wei)(wei)KVRS。對于鋰子電(dian)(dian)池(chi)，二(er)(er)(er)(er)選(xuan)(xuan)一開(kai)關(guan)將選(xuan)(xuan)通(tong)(tong)電(dian)(dian)池(chi)電(dian)(dian)壓VBAT；對于鎳鎘電(dian)(dian)池(chi)，二(er)(er)(er)(er)選(xuan)(xuan)一開(kai)關(guan)將選(xuan)(xuan)通(tong)(tong)7V恒(heng)定(ding)電(dian)(dian)壓。這里設二(er)(er)(er)(er)選(xuan)(xuan)一模(mo)擬開(kai)關(guan)的(de)(de)輸(shu)出(chu)(chu)為(wei)(wei)V1，那(nei)么(me)(me)加法(fa)器(qi)的(de)(de)輸(shu)出(chu)(chu)Vs應(ying)為(wei)(wei)：Vs=KVRS+V1，這樣一來，送到LTC4002的(de)(de)BAT和SENSE兩(liang)(liang)端(duan)的(de)(de)電(dian)(dian)壓之差應(ying)為(wei)(wei)KVRS。只要正確控制(zhi)K值(zhi)，就可(ke)(ke)以(yi)(yi)使充(chong)電(dian)(dian)電(dian)(dian)流為(wei)(wei)正常充(chong)電(dian)(dian)電(dian)(dian)流的(de)(de)1／K。因(yin)此，可(ke)(ke)以(yi)(yi)通(tong)(tong)過二(er)(er)(er)(er)選(xuan)(xuan)一開(kai)關(guan)控制(zhi)電(dian)(dian)流為(wei)(wei)恒(heng)流充(chong)電(dian)(dian)時的(de)(de)10％或30％。

　　對于LTC4002的BAT端輸入值，當開關選通鋰離子電池時，BAT的輸入即是電池電壓。此時，LTC4002可以控制整個鋰離子的充電過程。不需任何外界的干預。

　　當(dang)開(kai)關(guan)選通了(le)7V恒(heng)定(ding)(ding)電(dian)(dian)(dian)壓(ya)后，BAT端的(de)輸入恒(heng)定(ding)(ding)為7V，此時(shi)，LTC4002無法(fa)知道電(dian)(dian)(dian)池(chi)(chi)的(de)真實電(dian)(dian)(dian)壓(ya)，只認為電(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)壓(ya)為7V。所以(yi)，盡(jin)管(guan)電(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)壓(ya)高于8.4V，仍會以(yi)恒(heng)定(ding)(ding)電(dian)(dian)(dian)流(liu)對電(dian)(dian)(dian)池(chi)(chi)進(jin)行充電(dian)(dian)(dian)。在這種情況下，需要微控制(zhi)(zhi)器(qi)的(de)干預，否則，會造成(cheng)電(dian)(dian)(dian)池(chi)(chi)的(de)過充。由于微控制(zhi)(zhi)器(qi)內部帶(dai)有(you)ADC，可以(yi)監測電(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)壓(ya)的(de)變化。當(dang)電(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)壓(ya)達到指定(ding)(ding)值時(shi)，減小充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)，直至電(dian)(dian)(dian)池(chi)(chi)充滿。這樣就可以(yi)對9.2V的(de)鎳鎘電(dian)(dian)(dian)池(chi)(chi)進(jin)行充電(dian)(dian)(dian)了(le)。

　　脈(mo)沖充(chong)放電電路的設計

　　由于LTC4002是恒流充電(dian)控(kong)制芯片，因此，必(bi)須使(shi)(shi)用(yong)微(wei)控(kong)制器(qi)控(kong)制其(qi)充電(dian)使(shi)(shi)能引(yin)腳(jiao)COMP。當需要LTC4002輸(shu)出(chu)充電(dian)脈沖(chong)時(shi)，使(shi)(shi)控(kong)制COMP引(yin)腳(jiao)的端口(kou)變(bian)為高阻態，使(shi)(shi)COMP引(yin)腳(jiao)自行升至360mV以(yi)上時(shi)，便有充電(dian)電(dian)流輸(shu)出(chu)。放電(dian)時(shi)，必(bi)須將(jiang)COMP引(yin)腳(jiao)拉低(di)，使(shi)(shi)LTC4002關斷充電(dian)電(dian)流。之后，再打開放電(dian)電(dian)路。微(wei)控(kong)制器(qi)選用(yong)PIC16F873，它(ta)是一款(kuan)基于Flash的8位(wei)微(wei)控(kong)制器(qi)。內部有定時(shi)器(qi)、看門狗電(dian)路、10位(wei)ADC等(deng)模塊。

　　微控制器以1s為周(zhou)期對(dui)鎳(nie)鎘電池進行脈沖充放電。

　　系統軟件設計

　　系統軟件總體設計

　　充(chong)(chong)(chong)電(dian)(dian)單元(yuan)(yuan)中的(de)微控制(zhi)器(qi)主(zhu)要負責(ze)充(chong)(chong)(chong)電(dian)(dian)過程(cheng)的(de)控制(zhi)和與(yu)總控板(ban)的(de)通信，程(cheng)序流程(cheng)如圖4所示(shi)。充(chong)(chong)(chong)電(dian)(dian)單元(yuan)(yuan)首先判斷是否(fou)有電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)，如果有電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)放(fang)入，則判斷充(chong)(chong)(chong)放(fang)電(dian)(dian)狀(zhuang)態(tai)，默認是充(chong)(chong)(chong)電(dian)(dian)狀(zhuang)態(tai)，該狀(zhuang)態(tai)可由總控單元(yuan)(yuan)改變。若充(chong)(chong)(chong)電(dian)(dian)單元(yuan)(yuan)處于充(chong)(chong)(chong)電(dian)(dian)狀(zhuang)態(tai)，則繼(ji)續判斷電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)的(de)化學性質，針(zhen)對不同(tong)(tong)的(de)電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)采用不同(tong)(tong)的(de)充(chong)(chong)(chong)電(dian)(dian)方式。若處于放(fang)電(dian)(dian)狀(zhuang)態(tai)，則對電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)組進行放(fang)電(dian)(dian)，直到電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)電(dian)(dian)壓(ya)低于閾值電(dian)(dian)壓(ya)后，轉為充(chong)(chong)(chong)電(dian)(dian)狀(zhuang)態(tai)。

　　除主程(cheng)序(xu)外，總(zong)控單(dan)(dan)元與充電(dian)(dian)(dian)單(dan)(dan)元的(de)通信(xin)是在中斷服(fu)務程(cheng)序(xu)中實現的(de)。當充電(dian)(dian)(dian)單(dan)(dan)元收到總(zong)控單(dan)(dan)元的(de)指令(ling)后，進入中斷。若指令(ling)是查(cha)詢(xun)數(shu)據(ju)指令(ling)，則向總(zong)控單(dan)(dan)元發送需要的(de)數(shu)據(ju)。若是充電(dian)(dian)(dian)狀態(tai)設(she)置指令(ling)，則依據(ju)指令(ling)設(she)置充電(dian)(dian)(dian)單(dan)(dan)元的(de)充電(dian)(dian)(dian)狀態(tai)。

　　通信協議的實現

　　通過與電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)組(zu)(zu)中(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)能計(ji)量(liang)芯片通信的(de)方(fang)法來(lai)判(pan)斷(duan)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)性(xing)質。本系統可(ke)以與遵循(xun)HDQ16接口協(xie)議的(de)智能電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)組(zu)(zu)進(jin)行通信，除了電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)組(zu)(zu)的(de)化(hua)學性(xing)質外，還可(ke)以將電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)組(zu)(zu)的(de)容量(liang)、電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)、充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流、編(bian)號(hao)等數據一并讀取(qu)，供充電(dian)(dian)(dian)(dian)(dian)(dian)器顯(xian)示之用。

　　充電單元(yuan)可以通過HDQ總線對(dui)智能電池進(jin)行讀(du)操作。HDQ16接(jie)口協(xie)議是基(ji)于指(zhi)令(ling)的(de)(de)協(xie)議。一個處理(li)器(qi)發送8位(wei)指(zhi)令(ling)碼(ma)(ma)給智能電池，這個8位(wei)的(de)(de)指(zhi)令(ling)碼(ma)(ma)由(you)兩部分組成(cheng)，7位(wei)HDQ16指(zhi)令(ling)碼(ma)(ma)(位(wei)0～6)和1位(wei)讀(du)／寫(xie)指(zhi)令(ling)。讀(du)／寫(xie)指(zhi)令(ling)指(zhi)示智能 電池存(cun)儲接(jie)下來(lai)的(de)(de)16位(wei)數(shu)(shu)據(ju)到一個指(zhi)定的(de)(de)寄存(cun)器(qi)，或者從指(zhi)定的(de)(de)寄存(cun)器(qi)輸出16位(wei)數(shu)(shu)據(ju)。在HDQ16里，數(shu)(shu)據(ju)字節(指(zhi)令(ling))或者字(數(shu)(shu)據(ju))的(de)(de)最不重(zhong)要(yao)的(de)(de)位(wei)會優先傳輸。

　　一個塊(kuai)的(de)傳輸(shu)包括三個不同的(de)部分(fen)。第一部分(fen)經由主(zhu)機或者(zhe)智(zhi)能電池把HDQ16引腳置邏輯低狀態一個tSTRH：B時間后開(kai)始發送。接下來(lai)的(de)部分(fen)是真正的(de)數據(ju)傳輸(shu)，數據(ju)位(wei)在tDSU:B時間間隔(ge)里是有效的(de)，負邊界用來(lai)開(kai)始通信。數據(ju)位(wei)被保持一個tDH:DV時間間隔(ge)，以便允(yun)許主(zhu)機或智(zhi)能電池采樣(yang)數據(ju)位(wei)。

　　在負邊界(jie)開始(shi)通(tong)信后，最后一部分通(tong)過(guo)返回給HDQ16引腳一個邏(luo)輯(ji)高狀態，至(zhi)少保(bao)持tSSU:B時間(jian)間(jian)隔來停(ting)止(zhi)傳輸。最后一個邏(luo)輯(ji)高狀態必(bi)須保(bao)持一個tCYCH:B時間(jian)間(jian)隔，以便有時間(jian)讓塊傳輸完全(quan)停(ting)止(zhi)。

　　如果發(fa)生通信錯誤(wu)(e.g.，tCYCB>250μs)，主機就發(fa)送給智能電池一(yi)個BREAK信號(hao)，讓其控制串行接(jie)(jie)口。當HDQ16引腳(jiao)在一(yi)個時(shi)間(jian)(jian)間(jian)(jian)隔，或者更長時(shi)間(jian)(jian)里為邏輯低狀態(tai)(tai)時(shi)，智能電池就會偵測(ce)BREAK。然(ran)后(hou)，HDQ16引腳(jiao)回到其正常預設高邏輯狀態(tai)(tai)一(yi)個tBR時(shi)間(jian)(jian)間(jian)(jian)隔。然(ran)后(hou)，智能電池就準備(bei)從主機那里接(jie)(jie)收指(zhi)令(ling)。

　　HDQ16引腳是開(kai)漏的，需要一(yi)個外部的上拉電阻(zu)。

　　圖5是用邏輯分析儀顯示的一次HDQ總線上的通信波形。本文提出的充電系統從技術上很好地解決了上述問題，通過LCD顯示屏可以清晰便捷地讀出電源的剩余容量、已有充放電次數、充電及放電電流、電池電壓、容量統計和電池特性等重要內容，并且通過設定，可以判斷電源是否達到報廢標準，及時提醒操作者更新電源。為電源維護保養工作提供明確的參考數據，降低了對操作人員專業技術水平的要求，保證了列車尾部電源的安全使用。