太陽能電池板的便攜式充電器是(shi)解決(jue)通信設(she)備、田間測(ce)量儀器等(deng)移動(dong)式電(dian)(dian)(dian)(dian)(dian)子(zi)產品供電(dian)(dian)(dian)(dian)(dian)問(wen)題的(de)最佳(jia)解決(jue)方(fang)案之一。采用TPS5430 降壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)和MAX167 4 升壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，由LM393、ICL7660 等(deng)元件(jian)構成的(de)切(qie)換電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)為(wei)(wei)控制核心，設(she)計(ji)具(ju)有自(zi)啟動(dong)功(gong)能(neng)的(de)電(dian)(dian)(dian)(dian)(dian)能(neng)收集充(chong)電(dian)(dian)(dian)(dian)(dian)器。充(chong)電(dian)(dian)(dian)(dian)(dian)器能(neng)夠(gou)根據充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)不同，自(zi)動(dong)切(qie)換到不同的(de)DC-DC 變換電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，實現高效(xiao)、快速充(chong)電(dian)(dian)(dian)(dian)(dian)。測(ce)試表明，當充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源內(nei)(nei)阻(zu)Rs為(wei)(wei)100 Ω，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)Es在(zai)10～20 V 范(fan)圍內(nei)(nei)，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)動(dong)勢Ec為(wei)(wei)3.6 V、內(nei)(nei)阻(zu)Rc為(wei)(wei)0.1 Ω 時，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流Ic>58 mA，自(zi)動(dong)啟動(dong)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)(wei)3.6 V，電(dian)(dian)(dian)(dian)(dian)池放(fang)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流為(wei)(wei)3 mA；而(er)當充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源內(nei)(nei)阻(zu)Rs為(wei)(wei)1 Ω，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)Es在(zai)1.2～3.6 V 范(fan)圍內(nei)(nei)時，最大充(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， 由可調直流電(dian)(dian)(dian)源模(mo)擬當太陽能(neng)(neng)電(dian)(dian)(dian)池板的(de)輸出電(dian)(dian)(dian)壓大范圍變(bian)化時(shi)，實現充(chong)電(dian)(dian)(dian)器(qi)的(de)自動啟動并盡可能(neng)(neng)地(di)增大充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流來實現充(chong)電(dian)(dian)(dian)效(xiao)率(lv)的(de)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)電動勢(shi)Ec恒定為3.6 V，內(nei)阻Rc為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。由此可得，當(dang)Rs=100 Ω，Es=10 V 時，Ps=0.25 W，Ic>64 mA，η >92.16%；當(dang)Es=20 V 時，Ps=1 W，Ic>160 mA，η>57.6%。為了盡可能提高(gao)(gao)高(gao)(gao)電壓(ya)時的充電效率，除選用TPS5430 構成降壓(ya)電路外(wai)，應(ying)盡量降低(di)(di)切換電路的開(kai)(kai)關(guan)頻(pin)率。電路中(zhong)主要功耗(hao)元件是功率場效應(ying)管（FET），在(zai)低(di)(di)頻(pin)情況(kuang)下，功率FET 主要是傳導損耗(hao)，在(zai)高(gao)(gao)頻(pin)情況(kuang)下，傳導損耗(hao)維(wei)持不變(bian)，同(tong)頻(pin)率有關(guan)的損耗(hao)會增大。較高(gao)(gao)或較低(di)(di)的開(kai)(kai)關(guan)頻(pin)率均會使效率降低(di)(di)，綜合考慮各因素并結合試(shi)驗(yan)，測得開(kai)(kai)關(guan)頻(pin)率為500 kHz 時效率為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)工作(zuo)和(he)降壓(ya)(ya)工作(zuo)兩種模(mo)式(shi)。設(she)(she)定切換的閾(yu)值電(dian)(dian)(dian)壓(ya)(ya)為(wei)3.6 V，閾(yu)值電(dian)(dian)(dian)壓(ya)(ya)由(you)可調電(dian)(dian)(dian)阻設(she)(she)定并可調。充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)超過閾(yu)值電(dian)(dian)(dian)壓(ya)(ya)時(shi)降壓(ya)(ya)電(dian)(dian)(dian)路工作(zuo)，低于閾(yu)值電(dian)(dian)(dian)壓(ya)(ya)時(shi)升壓(ya)(ya)電(dian)(dian)(dian)路工作(zuo)。切換電(dian)(dian)(dian)路由(you)場效應管、電(dian)(dian)(dian)壓(ya)(ya)比較器(qi)等分立(li)元(yuan)件構成，原理圖(tu)如(ru)圖(tu)3 所示(shi)。

　　圖3 中， 輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端VIN （P1） 接(jie)(jie)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)， 輸(shu)(shu)(shu)(shu)(shu)(shu)出端P2 接(jie)(jie)MAX167 4升(sheng)(sheng)(sheng)(sheng)壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端，肖特基(ji)二極管VD1用于防(fang)止(zhi)電(dian)(dian)(dian)(dian)(dian)流倒(dao)灌。穩壓(ya)(ya)(ya)(ya)(ya)器TL431 為電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)比較器LM393 的(de)(de)(de)負(fu)(fu)輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端提供(gong)參考電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)。輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端VIN（P1）通過(guo)濾(lv)波(bo)后(hou)接(jie)(jie)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)比較器LM393 的(de)(de)(de)正(zheng)輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端。調(diao)節R_ad可(ke)調(diao)電(dian)(dian)(dian)(dian)(dian)阻，使輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)小于3.6 V 時電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)比較器LM393 輸(shu)(shu)(shu)(shu)(shu)(shu)出負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)，P 溝道MOS 管IRLM16402VQ1、VQ2和(he)VQ3導(dao)通，VQ1，VQ2的(de)(de)(de)漏極連接(jie)(jie)升(sheng)(sheng)(sheng)(sheng)壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)， 使切(qie)換(huan)電(dian)(dian)(dian)(dian)(dian)路(lu)輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)、輸(shu)(shu)(shu)(shu)(shu)(shu)出端短接(jie)(jie)，使充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)接(jie)(jie)至升(sheng)(sheng)(sheng)(sheng)壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)。當(dang)(dang)輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)大于3.6 V 時，輸(shu)(shu)(shu)(shu)(shu)(shu)出高電(dian)(dian)(dian)(dian)(dian)平，VQ1、VQ2和(he)VQ3截止(zhi)，此時MAX167 4升(sheng)(sheng)(sheng)(sheng)壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)無輸(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)。VD2、VD3的(de)(de)(de)作用是當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)大于3.6 V 時，LM393的(de)(de)(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)源(yuan)端接(jie)(jie)地(di)； 當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)小于5.5 V 時，LM393 負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)源(yuan)通過(guo)VQ3接(jie)(jie)ICL7660 的(de)(de)(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)輸(shu)(shu)(shu)(shu)(shu)(shu)出引腳。

　　2.2 升壓/降壓電路設計

　　升壓電(dian)(dian)路(lu)主(zhu)要由升壓式DC-DC 電(dian)(dian)源轉換(huan)器MAX167 4組成，升壓后輸出4 V 直(zhi)接對電(dian)(dian)池進行充電(dian)(dian)。MAX167 4升壓電(dian)(dian)路(lu)如圖4 所示。

　　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(xue)弱(ruo)紋波對輸出電(dian)壓的影響(xiang)。

　　降(jiang)壓(ya)(ya)電路主要由(you)降(jiang)壓(ya)(ya)DC-DC 轉換(huan)器TPS5430 組(zu)成，降(jiang)壓(ya)(ya)后直接對(dui)電池進行充電。TPS5430 降(jiang)壓(ya)(ya)電路如圖5 所(suo)示。

　　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的取值按公式計算， 可得(de)所需的(de)電感(gan)值是(shi)15.8 μH，選取內徑30 mm 的(de)鐵硅(gui)鋁磁(ci)芯(xin)自(zi)行繞制的(de)電感(gan)值為(wei)18 μH，以保證在額定(ding)的(de)工(gong)作(zuo)狀況下不會出(chu)現磁(ci)飽和(he)(he)。電阻(zu)R1、R2和(he)(he)R3構成反饋網絡， 將輸(shu)出(chu)電壓(ya)反饋到芯(xin)片的(de)VSNS 引腳，該芯(xin)片自(zi)動調節(jie)輸(shu)出(chu)電壓(ya)，保證充電器輸(shu)出(chu)端輸(shu)出(chu)電壓(ya)恒定(ding)。

　　3 試驗結果及分析

　　1）電源內(nei)阻Rs=100 Ω，調整Es的大小，使其在10～20 V范(fan)圍(wei)內(nei)變化，記錄數據如表(biao)1 所示。

　　由表1 可(ke)見，在(zai)Es為10 V 時，實測(ce)充(chong)電(dian)(dian)電(dian)(dian)流與理論值(zhi)存在(zai)5.9 mA 的偏差，充(chong)電(dian)(dian)電(dian)(dian)流低、充(chong)電(dian)(dian)器的轉(zhuan)換效(xiao)率(lv)不(bu)高可(ke)能與芯片(pian)的轉(zhuan)換效(xiao)率(lv)和輸(shu)入電(dian)(dian)壓有關，由TPS5430 的數(shu)據資料可(ke)知，在(zai)輸(shu)入電(dian)(dian)壓為10 V 左右，輸(shu)出(chu)電(dian)(dian)流約為60 mA 時，其(qi)工作效(xiao)率(lv)約為92%。而在(zai)12～20 V 范圍內，實測(ce)充(chong)電(dian)(dian)電(dian)(dian)流大于理論計算充(chong)電(dian)(dian)電(dian)(dian)流值(zhi)。

　　2）逐漸降低Es，直到(dao)充電(dian)(dian)電(dian)(dian)流Ic略大(da)于0 時，記錄(lu)對應(ying)的電(dian)(dian)源(yuan)電(dian)(dian)壓(ya)(ya)Es，該電(dian)(dian)壓(ya)(ya)即為最低可充電(dian)(dian)電(dian)(dian)壓(ya)(ya)。為保證準確性，對多個不同的電(dian)(dian)源(yuan)電(dian)(dian)壓(ya)(ya)值進行測試，選(xuan)取(qu)最優3 組(zu)數據記錄(lu)如表(biao)2 所示。

　　由表2 可(ke)見，當Es下降(jiang)到3.6 V 時，充(chong)電(dian)電(dian)流為0，充(chong)電(dian)器不能再對電(dian)池(chi)進行充(chong)電(dian)，故最低可(ke)充(chong)電(dian)電(dian)壓為3.6 V。

　　3）從0 開始逐漸升(sheng)高Es，Rs為(wei)0.1 Ω；當Es升(sheng)高到高于1.1 V 時，更換(huan)Rs為(wei)1 Ω。然后繼(ji)續(xu)升(sheng)高Es，直到充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流略(lve)大于0，記錄(lu)此時的電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)壓(ya)值，該電(dian)(dian)(dian)(dian)壓(ya)即為(wei)自動啟動充電(dian)(dian)(dian)(dian)功能的啟動電(dian)(dian)(dian)(dian)壓(ya)。為(wei)保證準確性，對多個(ge)不同的電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)壓(ya)值進(jin)行測試，選取最(zui)優4 組數據記錄(lu)如表3 所(suo)示。

　　由(you)表3 可見(jian)，當Es小于(yu)3.6 V 時，充電電流持(chi)續為(wei)0，一旦Es上升到3.6 V 后，充電電流由(you)0 開始增(zeng)加(jia)，即(ji)自動(dong)啟動(dong)充電電壓為(wei)3.6 V。

　　4）Es降低到(dao)不(bu)(bu)能向電(dian)(dian)(dian)池充電(dian)(dian)(dian)，最(zui)低至0 時，檢測放電(dian)(dian)(dian)電(dian)(dian)(dian)流。為保(bao)證準確(que)性，對多個不(bu)(bu)同的電(dian)(dian)(dian)源電(dian)(dian)(dian)壓值(zhi)進行(xing)測試，選(xuan)取最(zui)優3 組數據記錄(lu)如表4 所示。

　　由表(biao)4 可(ke)知(zhi)， 當電(dian)(dian)源電(dian)(dian)動勢(shi)下降到(dao)最(zui)低(di)可(ke)充(chong)電(dian)(dian)電(dian)(dian)壓時(shi)，電(dian)(dian)池開(kai)始放電(dian)(dian)，放電(dian)(dian)電(dian)(dian)流(liu)為3 mA。考慮到(dao)放電(dian)(dian)電(dian)(dian)流(liu)受倒灌電(dian)(dian)阻(zu)Rd影響，改(gai)變(bian)Rd的大小可(ke)改(gai)變(bian)放電(dian)(dian)電(dian)(dian)流(liu)。試(shi)驗表(biao)明，Rd=15 Ω 時(shi)放電(dian)(dian)電(dian)(dian)流(liu)最(zui)小。

　　5）接上(shang)電源內阻Rs=1 Ω，調(diao)整Es，使其在1.2～3.6 V 范圍內變化。數據記錄(lu)如表(biao)5 所(suo)示。

　　由表5 可(ke)見(jian)，隨(sui)著電(dian)(dian)源電(dian)(dian)勢的(de)增加(jia)，充(chong)電(dian)(dian)電(dian)(dian)流也隨(sui)著增加(jia)，直(zhi)到當Es達到3.2 V 時(shi)(shi)(shi)，充(chong)電(dian)(dian)電(dian)(dian)流不再跟隨(sui)電(dian)(dian)源電(dian)(dian)勢變化。當電(dian)(dian)源電(dian)(dian)勢為3.2 V 時(shi)(shi)(shi)，充(chong)電(dian)(dian)電(dian)(dian)流最大，為256 mA。導致充(chong)電(dian)(dian)電(dian)(dian)流突變的(de)原因是升(sheng)壓器件MAX1* 在(zai)不同(tong)輸入電(dian)(dian)壓下轉換效率(lv)(lv)不同(tong)。由于MAX1* 在(zai)超過3 V 電(dian)(dian)壓下工作時(shi)(shi)(shi)轉換效率(lv)(lv)低，所以充(chong)電(dian)(dian)電(dian)(dian)流出現(xian)非線性的(de)突變。

　　6）當Es≥1.1 V 時，取(qu)Rs =1 Ω；當Es＜1.1 V 時，取(qu)Rs=0.1 Ω。測量向(xiang)電池充電的Es，記錄數據如表(biao)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(di)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。