太陽能電池板的便攜式充電器是解決通信設備、田(tian)間測(ce)量儀器等移動(dong)(dong)式(shi)電(dian)(dian)(dian)(dian)(dian)子產(chan)品供(gong)電(dian)(dian)(dian)(dian)(dian)問題的(de)(de)最(zui)佳解決方(fang)案(an)之一。采用TPS5430 降壓(ya)電(dian)(dian)(dian)(dian)(dian)路和(he)MAX167 4 升壓(ya)電(dian)(dian)(dian)(dian)(dian)路，由LM393、ICL7660 等元件(jian)構成的(de)(de)切換電(dian)(dian)(dian)(dian)(dian)路為(wei)控(kong)制核心，設計具有(you)自(zi)啟動(dong)(dong)功(gong)能的(de)(de)電(dian)(dian)(dian)(dian)(dian)能收集(ji)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器。充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器能夠根據充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)不(bu)同，自(zi)動(dong)(dong)切換到(dao)不(bu)同的(de)(de)DC-DC 變換電(dian)(dian)(dian)(dian)(dian)路，實現高效、快速(su)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。測(ce)試表明，當充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源內(nei)阻Rs為(wei)100 Ω，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)Es在10～20 V 范(fan)圍內(nei)，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)動(dong)(dong)勢(shi)Ec為(wei)3.6 V、內(nei)阻Rc為(wei)0.1 Ω 時，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流Ic>58 mA，自(zi)動(dong)(dong)啟動(dong)(dong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)3.6 V，電(dian)(dian)(dian)(dian)(dian)池(chi)放電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流為(wei)3 mA；而當充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源內(nei)阻Rs為(wei)1 Ω，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)Es在1.2～3.6 V 范(fan)圍內(nei)時，最(zui)大充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流可達256 mA。

　　太陽能的開發及利用在大力提倡發展低碳經濟的時代背景下日益受到矚目。我國光伏產業以每年30%的速度增長， 最近三年全球太陽能電池總產量平均年增長率高達49.8%以上。而通信設備、田間測量儀器等便攜式電子產品的普及使得以太陽能電池板為基礎的便攜式充電裝置倍受青睞，不受地域限制，能夠在傳統充電器無法工作的場合進行應急或可持續充電。目前，充電電池的充電技術主要有電壓負增量控制、時間控制、溫度控制、最高電壓控制技術等。假設充電電池的電壓保持恒定的條件下， 利用LM393、ICL7660等元件構成的切換電路控制， 由TPS5430 降壓電路和MAX167 4 升壓電路組成智能充電器， 由可調(diao)直流(liu)電(dian)(dian)源模擬當太(tai)陽能電(dian)(dian)池板的輸(shu)出電(dian)(dian)壓大范(fan)圍變化時，實(shi)(shi)現充電(dian)(dian)器(qi)的自動啟動并盡可能地增大充電(dian)(dian)電(dian)(dian)流(liu)來(lai)實(shi)(shi)現充電(dian)(dian)效率的提高。

　　1 理論分析與計算

　　充電器的測試原理示意圖如圖1 所示。假定太陽能電池板的輸出功率有限，電動勢Es在一定范圍內緩慢變化，監測和控制電路采用間歇工作方式，以降低能耗。可充電池的(de)電(dian)動(dong)勢Ec恒(heng)定為(wei)3.6 V，內(nei)阻(zu)Rc為(wei)0.1 Ω。

　　直流電源電動勢為Es，電源內阻為Rs，可充電池電動勢為Ec，可充電池內阻為Rc，充電電流為Ic，為防止電流倒灌，在可充電池兩端并聯電阻Rd。理想情況下，充電器的輸入阻抗與電源內阻匹配，此時直流電源輸出功率為，充電器輸出功率為，則效率為。由此可(ke)得(de)，當(dang)Rs=100 Ω，Es=10 V 時(shi)，Ps=0.25 W，Ic>64 mA，η >92.16%；當(dang)Es=20 V 時(shi)，Ps=1 W，Ic>160 mA，η>57.6%。為(wei)了盡(jin)可(ke)能提高(gao)高(gao)電(dian)壓時(shi)的(de)(de)(de)充電(dian)效(xiao)率，除選用TPS5430 構成降壓電(dian)路外，應盡(jin)量降低(di)(di)切換電(dian)路的(de)(de)(de)開(kai)(kai)關(guan)(guan)頻率。電(dian)路中主要(yao)(yao)功(gong)耗(hao)元件是功(gong)率場效(xiao)應管（FET），在低(di)(di)頻情(qing)況(kuang)下，功(gong)率FET 主要(yao)(yao)是傳導損耗(hao)，在高(gao)頻情(qing)況(kuang)下，傳導損耗(hao)維持不變(bian)，同頻率有關(guan)(guan)的(de)(de)(de)損耗(hao)會增(zeng)大。較高(gao)或較低(di)(di)的(de)(de)(de)開(kai)(kai)關(guan)(guan)頻率均會使效(xiao)率降低(di)(di)，綜合(he)考慮各因素并結合(he)試驗，測得(de)開(kai)(kai)關(guan)(guan)頻率為(wei)500 kHz 時(shi)效(xiao)率為(wei)94.35%。

　　2 硬件電路設計

　　充電器硬件電路組成框圖如圖2 所示。充電器由切換電路自動判斷直流電源輸入電壓， 選擇升壓或降壓電路，實現在工作電壓范圍內自動切換， 模擬對充電電池的充電效果。

　　2.1 切換電路設計

　　切換電路用于切換充電器升壓(ya)(ya)(ya)工(gong)(gong)作和降壓(ya)(ya)(ya)工(gong)(gong)作兩種模式。設(she)定(ding)切(qie)(qie)換的(de)閾(yu)值(zhi)電(dian)(dian)(dian)壓(ya)(ya)(ya)為3.6 V，閾(yu)值(zhi)電(dian)(dian)(dian)壓(ya)(ya)(ya)由可調(diao)電(dian)(dian)(dian)阻(zu)設(she)定(ding)并可調(diao)。充電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)(ya)超過閾(yu)值(zhi)電(dian)(dian)(dian)壓(ya)(ya)(ya)時(shi)降壓(ya)(ya)(ya)電(dian)(dian)(dian)路(lu)工(gong)(gong)作，低于閾(yu)值(zhi)電(dian)(dian)(dian)壓(ya)(ya)(ya)時(shi)升壓(ya)(ya)(ya)電(dian)(dian)(dian)路(lu)工(gong)(gong)作。切(qie)(qie)換電(dian)(dian)(dian)路(lu)由場效應(ying)管、電(dian)(dian)(dian)壓(ya)(ya)(ya)比較(jiao)器等分立元件構成(cheng)，原理(li)圖如(ru)圖3 所示。

　　圖3 中， 輸(shu)(shu)(shu)(shu)入(ru)端(duan)VIN （P1） 接(jie)(jie)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源， 輸(shu)(shu)(shu)(shu)出(chu)端(duan)P2 接(jie)(jie)MAX167 4升壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路的輸(shu)(shu)(shu)(shu)入(ru)端(duan)，肖(xiao)特基(ji)二極管(guan)VD1用于(yu)防止(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流倒(dao)灌。穩壓器(qi)TL431 為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓比較(jiao)器(qi)LM393 的負(fu)輸(shu)(shu)(shu)(shu)入(ru)端(duan)提供參考電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓。輸(shu)(shu)(shu)(shu)入(ru)端(duan)VIN（P1）通(tong)過濾波后(hou)接(jie)(jie)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓比較(jiao)器(qi)LM393 的正輸(shu)(shu)(shu)(shu)入(ru)端(duan)。調節(jie)R_ad可調電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，使輸(shu)(shu)(shu)(shu)入(ru)小(xiao)于(yu)3.6 V 時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓比較(jiao)器(qi)LM393 輸(shu)(shu)(shu)(shu)出(chu)負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，P 溝道MOS 管(guan)IRLM16402VQ1、VQ2和VQ3導通(tong)，VQ1，VQ2的漏極連(lian)接(jie)(jie)升壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路， 使切換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路輸(shu)(shu)(shu)(shu)入(ru)、輸(shu)(shu)(shu)(shu)出(chu)端(duan)短接(jie)(jie)，使充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓接(jie)(jie)至(zhi)升壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路。當輸(shu)(shu)(shu)(shu)入(ru)大于(yu)3.6 V 時(shi)，輸(shu)(shu)(shu)(shu)出(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，VQ1、VQ2和VQ3截止(zhi)，此時(shi)MAX167 4升壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路無輸(shu)(shu)(shu)(shu)入(ru)。VD2、VD3的作用是當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓大于(yu)3.6 V 時(shi)，LM393的負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源端(duan)接(jie)(jie)地； 當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓小(xiao)于(yu)5.5 V 時(shi)，LM393 負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源通(tong)過VQ3接(jie)(jie)ICL7660 的負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓輸(shu)(shu)(shu)(shu)出(chu)引腳。

　　2.2 升壓/降壓電路設計

　　升壓(ya)(ya)電(dian)路主要由升壓(ya)(ya)式DC-DC 電(dian)源轉換器MAX167 4組成，升壓(ya)(ya)后輸出(chu)4 V 直(zhi)接對電(dian)池進行充電(dian)。MAX167 4升壓(ya)(ya)電(dian)路如圖(tu)4 所(suo)示。

　　圖4 中， 升壓芯片的儲能電感L1接MAX167 4的LX 引腳，電阻R1、R2和R3構成反饋網絡，將輸出電壓反饋至FB 引腳，芯片內部保持輸出電壓恒定。選取25 μH 電感和680 μF電容組成一階低通濾波器，截止頻率，以削弱紋波(bo)對輸出電壓的影響(xiang)。

　　降壓(ya)(ya)電(dian)(dian)路主(zhu)要由降壓(ya)(ya)DC-DC 轉換器TPS5430 組成，降壓(ya)(ya)后直(zhi)接對電(dian)(dian)池進(jin)行(xing)充電(dian)(dian)。TPS5430 降壓(ya)(ya)電(dian)(dian)路如圖(tu)5 所示(shi)。

　　經測試，綜合考慮效率因素，選定開關頻率為500 kHz，輸入端的電容C6和C7為旁路電容和降壓濾波電容， 由于轉換器中開關在導通瞬間需要較大電流，通過旁路電容吸收瞬間大電流和濾除高頻噪聲信號使芯片保持穩定工作。電路輸出功率越大，工作頻率越低，對應的電容值也應越大。選取等效串聯電阻阻值低，容值為10 μF 的電解電容。根據芯片數據資料， 輸出端電感L1的取值按公式計(ji)算(suan)， 可得(de)所需的(de)電(dian)(dian)感(gan)值(zhi)是15.8 μH，選取內徑30 mm 的(de)鐵硅鋁磁(ci)芯(xin)自行(xing)繞(rao)制的(de)電(dian)(dian)感(gan)值(zhi)為18 μH，以保證在額定的(de)工作狀(zhuang)況下(xia)不會(hui)出(chu)(chu)現磁(ci)飽和(he)。電(dian)(dian)阻R1、R2和(he)R3構成(cheng)反饋網絡， 將輸出(chu)(chu)電(dian)(dian)壓(ya)反饋到(dao)芯(xin)片(pian)的(de)VSNS 引腳(jiao)，該芯(xin)片(pian)自動調節(jie)輸出(chu)(chu)電(dian)(dian)壓(ya)，保證充電(dian)(dian)器輸出(chu)(chu)端輸出(chu)(chu)電(dian)(dian)壓(ya)恒(heng)定。

　　3 試驗結果及分析

　　1）電(dian)源內阻(zu)Rs=100 Ω，調整Es的(de)大小，使其(qi)在10～20 V范圍內變化，記錄數據(ju)如表1 所示。

　　由(you)表1 可見(jian)，在Es為10 V 時(shi)，實測充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)與(yu)理論值存在5.9 mA 的偏差，充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)低、充(chong)電(dian)(dian)(dian)(dian)器的轉換效(xiao)率(lv)(lv)不(bu)高(gao)可能與(yu)芯片的轉換效(xiao)率(lv)(lv)和輸(shu)入電(dian)(dian)(dian)(dian)壓有(you)關，由(you)TPS5430 的數據資料可知，在輸(shu)入電(dian)(dian)(dian)(dian)壓為10 V 左(zuo)右，輸(shu)出電(dian)(dian)(dian)(dian)流(liu)約為60 mA 時(shi)，其工作效(xiao)率(lv)(lv)約為92%。而在12～20 V 范圍內，實測充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)大于理論計算充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)值。

　　2）逐漸(jian)降低Es，直到充電(dian)電(dian)流Ic略(lve)大于0 時，記錄對(dui)應的電(dian)源(yuan)電(dian)壓Es，該電(dian)壓即(ji)為最(zui)(zui)低可充電(dian)電(dian)壓。為保證準確性，對(dui)多個(ge)不(bu)同(tong)的電(dian)源(yuan)電(dian)壓值進行測試(shi)，選取最(zui)(zui)優3 組數據記錄如表2 所示。

　　由表(biao)2 可見，當Es下降到3.6 V 時，充(chong)(chong)電(dian)(dian)電(dian)(dian)流為0，充(chong)(chong)電(dian)(dian)器(qi)不能再對電(dian)(dian)池進(jin)行充(chong)(chong)電(dian)(dian)，故(gu)最(zui)低可充(chong)(chong)電(dian)(dian)電(dian)(dian)壓(ya)為3.6 V。

　　3）從0 開始逐漸升(sheng)高(gao)(gao)Es，Rs為(wei)0.1 Ω；當Es升(sheng)高(gao)(gao)到高(gao)(gao)于1.1 V 時，更換Rs為(wei)1 Ω。然后(hou)繼續升(sheng)高(gao)(gao)Es，直(zhi)到充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流略大于0，記錄此(ci)時的(de)電(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)壓(ya)(ya)值，該電(dian)(dian)(dian)壓(ya)(ya)即為(wei)自動(dong)啟動(dong)充(chong)電(dian)(dian)(dian)功能的(de)啟動(dong)電(dian)(dian)(dian)壓(ya)(ya)。為(wei)保證準確性，對(dui)多個(ge)不同的(de)電(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)壓(ya)(ya)值進行測試，選取最優4 組數據記錄如表3 所示。

　　由表(biao)3 可見，當Es小于3.6 V 時，充(chong)電(dian)(dian)電(dian)(dian)流(liu)持續為0，一旦(dan)Es上升到3.6 V 后，充(chong)電(dian)(dian)電(dian)(dian)流(liu)由0 開始增加，即自動(dong)啟動(dong)充(chong)電(dian)(dian)電(dian)(dian)壓為3.6 V。

　　4）Es降低到不能(neng)向電(dian)(dian)(dian)池充電(dian)(dian)(dian)，最(zui)低至0 時，檢測(ce)放電(dian)(dian)(dian)電(dian)(dian)(dian)流。為(wei)保(bao)證準確性，對多個不同的電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)值(zhi)進行測(ce)試，選取(qu)最(zui)優3 組數據記錄(lu)如表4 所示。

　　由表(biao)4 可知， 當電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)動勢下降(jiang)到最低可充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓時，電(dian)(dian)(dian)(dian)池開始放電(dian)(dian)(dian)(dian)，放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)為3 mA。考慮(lv)到放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)受(shou)倒(dao)灌電(dian)(dian)(dian)(dian)阻Rd影(ying)響，改變(bian)Rd的大小(xiao)可改變(bian)放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)。試(shi)驗(yan)表(biao)明，Rd=15 Ω 時放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)最小(xiao)。

　　5）接(jie)上電源內阻Rs=1 Ω，調整Es，使其在1.2～3.6 V 范圍(wei)內變化。數(shu)據記錄如表5 所示。

　　由表5 可見，隨(sui)著電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)勢(shi)的增加，充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)也(ye)隨(sui)著增加，直(zhi)到當(dang)Es達到3.2 V 時(shi)，充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)不(bu)再跟隨(sui)電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)勢(shi)變化。當(dang)電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)勢(shi)為3.2 V 時(shi)，充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)最大，為256 mA。導致充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)突(tu)變的原因是(shi)升壓器件MAX1* 在不(bu)同(tong)輸(shu)入電(dian)(dian)(dian)(dian)壓下轉(zhuan)換(huan)效率不(bu)同(tong)。由于MAX1* 在超(chao)過3 V 電(dian)(dian)(dian)(dian)壓下工作時(shi)轉(zhuan)換(huan)效率低，所以充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)出現非線性的突(tu)變。

　　6）當(dang)Es≥1.1 V 時(shi)，取(qu)Rs =1 Ω；當(dang)Es＜1.1 V 時(shi)，取(qu)Rs=0.1 Ω。測(ce)量向電池充(chong)電的Es，記(ji)錄數據(ju)如表6 所示。

　　由表6 可知，逐漸降低電源電勢Es時，充電電流也隨著下降。當Es到達0.4 V 時輸出電壓已經在0 V 附近變化，因此能向電池充電的最低Es為0.4 V。

　　4 結論

　　本設計以切換電路為控制核心，控制升壓型電路和降壓型電路對電池進行充電。該充電器輸出電壓能夠恒定在4 V，自動啟動充電功能的Es為3.6 V，Es降低到不能向電池充電時，電池放電電流為3 mA，電路適合由輸出電壓波動較大的太陽能電池板供電的便攜式充電器，且充電效率高于傳統的充電器。