太陽能電池板的便攜式充電器是解(jie)決通信(xin)設備、田間(jian)測量儀器等移(yi)動(dong)式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子產品供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)問題的最佳解(jie)決方(fang)案之(zhi)一。采用(yong)TPS5430 降壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)和MAX167 4 升壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，由LM393、ICL7660 等元件構(gou)成的切換(huan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)為(wei)控制(zhi)核心(xin)，設計具有自(zi)啟(qi)動(dong)功能(neng)(neng)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)(neng)收集(ji)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器。充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器能(neng)(neng)夠根(gen)據充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的不同，自(zi)動(dong)切換(huan)到(dao)不同的DC-DC 變換(huan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，實(shi)現高(gao)效、快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。測試表(biao)明，當充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源內(nei)(nei)阻Rs為(wei)100 Ω，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓Es在(zai)10～20 V 范圍(wei)內(nei)(nei)，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)勢Ec為(wei)3.6 V、內(nei)(nei)阻Rc為(wei)0.1 Ω 時，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)Ic>58 mA，自(zi)動(dong)啟(qi)動(dong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)3.6 V，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)為(wei)3 mA；而當充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源內(nei)(nei)阻Rs為(wei)1 Ω，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓Es在(zai)1.2～3.6 V 范圍(wei)內(nei)(nei)時，最大(da)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)可(ke)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)源模擬當太陽能電(dian)(dian)(dian)池板的輸出電(dian)(dian)(dian)壓大范圍變化時(shi)，實現(xian)(xian)充(chong)電(dian)(dian)(dian)器(qi)的自動(dong)啟動(dong)并盡(jin)可能地增大充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流來實現(xian)(xian)充(chong)電(dian)(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。可充電池的電(dian)動勢(shi)Ec恒定為3.6 V，內阻(zu)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(you)此可得，當(dang)Rs=100 Ω，Es=10 V 時(shi)(shi)，Ps=0.25 W，Ic>64 mA，η >92.16%；當(dang)Es=20 V 時(shi)(shi)，Ps=1 W，Ic>160 mA，η>57.6%。為(wei)了盡可能提高(gao)高(gao)電(dian)壓(ya)時(shi)(shi)的(de)充(chong)電(dian)效(xiao)率(lv)(lv)(lv)，除選用TPS5430 構成(cheng)降(jiang)壓(ya)電(dian)路外，應盡量降(jiang)低切換電(dian)路的(de)開關頻(pin)(pin)率(lv)(lv)(lv)。電(dian)路中主(zhu)(zhu)要功耗元件是(shi)功率(lv)(lv)(lv)場效(xiao)應管（FET），在(zai)低頻(pin)(pin)情(qing)(qing)況下，功率(lv)(lv)(lv)FET 主(zhu)(zhu)要是(shi)傳導損(sun)(sun)(sun)耗，在(zai)高(gao)頻(pin)(pin)情(qing)(qing)況下，傳導損(sun)(sun)(sun)耗維持不變，同頻(pin)(pin)率(lv)(lv)(lv)有(you)關的(de)損(sun)(sun)(sun)耗會增大。較(jiao)高(gao)或(huo)較(jiao)低的(de)開關頻(pin)(pin)率(lv)(lv)(lv)均會使效(xiao)率(lv)(lv)(lv)降(jiang)低，綜合(he)考慮各(ge)因素并結(jie)合(he)試驗(yan)，測得開關頻(pin)(pin)率(lv)(lv)(lv)為(wei)500 kHz 時(shi)(shi)效(xiao)率(lv)(lv)(lv)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工(gong)作(zuo)(zuo)(zuo)和降(jiang)(jiang)壓工(gong)作(zuo)(zuo)(zuo)兩(liang)種(zhong)模式。設(she)定切換的閾(yu)值電(dian)(dian)(dian)(dian)壓為3.6 V，閾(yu)值電(dian)(dian)(dian)(dian)壓由可(ke)調電(dian)(dian)(dian)(dian)阻設(she)定并可(ke)調。充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓超過閾(yu)值電(dian)(dian)(dian)(dian)壓時降(jiang)(jiang)壓電(dian)(dian)(dian)(dian)路(lu)工(gong)作(zuo)(zuo)(zuo)，低于閾(yu)值電(dian)(dian)(dian)(dian)壓時升壓電(dian)(dian)(dian)(dian)路(lu)工(gong)作(zuo)(zuo)(zuo)。切換電(dian)(dian)(dian)(dian)路(lu)由場效應(ying)管、電(dian)(dian)(dian)(dian)壓比較(jiao)器等分立元件構(gou)成，原理圖如圖3 所示。

　　圖3 中， 輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)VIN （P1） 接(jie)(jie)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)， 輸(shu)(shu)出端(duan)(duan)P2 接(jie)(jie)MAX167 4升壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路的輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)，肖特基二極管(guan)VD1用(yong)于防止(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流倒灌。穩壓(ya)器(qi)TL431 為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)比(bi)較器(qi)LM393 的負輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)提供參考電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)VIN（P1）通過(guo)濾波后接(jie)(jie)入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)比(bi)較器(qi)LM393 的正輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)。調節R_ad可調電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，使(shi)(shi)輸(shu)(shu)入(ru)(ru)(ru)小于3.6 V 時電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)比(bi)較器(qi)LM393 輸(shu)(shu)出負電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，P 溝(gou)道(dao)MOS 管(guan)IRLM16402VQ1、VQ2和VQ3導通，VQ1，VQ2的漏極連接(jie)(jie)升壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路， 使(shi)(shi)切換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路輸(shu)(shu)入(ru)(ru)(ru)、輸(shu)(shu)出端(duan)(duan)短接(jie)(jie)，使(shi)(shi)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)接(jie)(jie)至升壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路。當(dang)輸(shu)(shu)入(ru)(ru)(ru)大于3.6 V 時，輸(shu)(shu)出高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，VQ1、VQ2和VQ3截(jie)止(zhi)，此時MAX167 4升壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路無輸(shu)(shu)入(ru)(ru)(ru)。VD2、VD3的作用(yong)是當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)大于3.6 V 時，LM393的負電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)端(duan)(duan)接(jie)(jie)地； 當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)小于5.5 V 時，LM393 負電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)通過(guo)VQ3接(jie)(jie)ICL7660 的負電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)輸(shu)(shu)出引(yin)腳。

　　2.2 升壓/降壓電路設計

　　升(sheng)壓電路主要由升(sheng)壓式(shi)DC-DC 電源轉換器MAX167 4組成，升(sheng)壓后(hou)輸(shu)出4 V 直(zhi)接對(dui)電池進行充電。MAX167 4升(sheng)壓電路如圖4 所(suo)示(shi)。

　　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(yi)削弱紋(wen)波對輸出電壓的影響。

　　降(jiang)壓(ya)(ya)電路(lu)主要由降(jiang)壓(ya)(ya)DC-DC 轉換器(qi)TPS5430 組成(cheng)，降(jiang)壓(ya)(ya)后直(zhi)接對電池進行(xing)充電。TPS5430 降(jiang)壓(ya)(ya)電路(lu)如圖(tu)5 所示。

　　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(ke)得所(suo)需的(de)(de)(de)電(dian)感值是(shi)15.8 μH，選取內徑30 mm 的(de)(de)(de)鐵(tie)硅(gui)鋁磁(ci)芯自行繞制的(de)(de)(de)電(dian)感值為(wei)18 μH，以(yi)保(bao)證(zheng)在(zai)額定的(de)(de)(de)工作狀況下(xia)不會出(chu)(chu)現磁(ci)飽(bao)和。電(dian)阻R1、R2和R3構成反(fan)饋網絡， 將輸(shu)出(chu)(chu)電(dian)壓(ya)反(fan)饋到芯片的(de)(de)(de)VSNS 引腳，該芯片自動調節輸(shu)出(chu)(chu)電(dian)壓(ya)，保(bao)證(zheng)充(chong)電(dian)器輸(shu)出(chu)(chu)端輸(shu)出(chu)(chu)電(dian)壓(ya)恒定。

　　3 試驗結果及分析

　　1）電源內阻Rs=100 Ω，調整Es的大(da)小(xiao)，使其(qi)在(zai)10～20 V范圍內變化，記錄數據如表1 所示。

　　由表1 可見，在Es為(wei)10 V 時，實(shi)測充(chong)電(dian)電(dian)流與(yu)理論值存(cun)在5.9 mA 的(de)(de)偏差，充(chong)電(dian)電(dian)流低、充(chong)電(dian)器的(de)(de)轉換(huan)(huan)效率不高可能與(yu)芯片(pian)的(de)(de)轉換(huan)(huan)效率和輸入電(dian)壓(ya)有關，由TPS5430 的(de)(de)數(shu)據(ju)資料可知，在輸入電(dian)壓(ya)為(wei)10 V 左(zuo)右，輸出電(dian)流約(yue)為(wei)60 mA 時，其工作效率約(yue)為(wei)92%。而在12～20 V 范圍內，實(shi)測充(chong)電(dian)電(dian)流大(da)于理論計(ji)算充(chong)電(dian)電(dian)流值。

　　2）逐漸降低Es，直到充(chong)電(dian)(dian)電(dian)(dian)流Ic略(lve)大于0 時，記錄對(dui)應的(de)電(dian)(dian)源電(dian)(dian)壓(ya)Es，該(gai)電(dian)(dian)壓(ya)即為最低可充(chong)電(dian)(dian)電(dian)(dian)壓(ya)。為保證(zheng)準確性，對(dui)多個不(bu)同的(de)電(dian)(dian)源電(dian)(dian)壓(ya)值(zhi)進行(xing)測試，選取最優3 組數據(ju)記錄如表2 所示。

　　由表2 可見，當Es下降到3.6 V 時，充(chong)電(dian)電(dian)流(liu)為0，充(chong)電(dian)器不(bu)能再對電(dian)池進行充(chong)電(dian)，故最低可充(chong)電(dian)電(dian)壓為3.6 V。

　　3）從0 開始逐(zhu)漸升高(gao)Es，Rs為(wei)(wei)(wei)0.1 Ω；當Es升高(gao)到高(gao)于1.1 V 時，更換Rs為(wei)(wei)(wei)1 Ω。然后繼續升高(gao)Es，直到充電(dian)電(dian)流(liu)略大于0，記錄此時的電(dian)源(yuan)電(dian)壓值，該電(dian)壓即為(wei)(wei)(wei)自動(dong)啟動(dong)充電(dian)功能的啟動(dong)電(dian)壓。為(wei)(wei)(wei)保證(zheng)準確性，對(dui)多(duo)個不同的電(dian)源(yuan)電(dian)壓值進行(xing)測試，選取最優(you)4 組(zu)數(shu)據記錄如表(biao)3 所示。

　　由(you)(you)表3 可見，當Es小(xiao)于3.6 V 時，充(chong)(chong)電(dian)(dian)電(dian)(dian)流持(chi)續為0，一旦Es上升到3.6 V 后(hou)，充(chong)(chong)電(dian)(dian)電(dian)(dian)流由(you)(you)0 開(kai)始增加，即自動(dong)啟動(dong)充(chong)(chong)電(dian)(dian)電(dian)(dian)壓為3.6 V。

　　4）Es降(jiang)低(di)到不能向(xiang)電(dian)(dian)池充電(dian)(dian)，最低(di)至0 時，檢測放電(dian)(dian)電(dian)(dian)流(liu)。為保證準確性，對多個不同的(de)電(dian)(dian)源電(dian)(dian)壓值進(jin)行測試(shi)，選取最優(you)3 組數據記錄如表4 所示。

　　由(you)表(biao)4 可(ke)知(zhi)， 當電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)動勢下降到最低(di)可(ke)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)時(shi)，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)流為3 mA。考慮到放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流受倒灌電(dian)(dian)(dian)(dian)阻Rd影響，改(gai)變(bian)Rd的(de)大小(xiao)可(ke)改(gai)變(bian)放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流。試驗表(biao)明，Rd=15 Ω 時(shi)放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流最小(xiao)。

　　5）接上電源內阻Rs=1 Ω，調整Es，使其(qi)在1.2～3.6 V 范圍內變(bian)化。數據記錄如(ru)表(biao)5 所(suo)示。

　　由(you)表5 可見，隨著電(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)勢(shi)的增加(jia)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流也(ye)隨著增加(jia)，直到當Es達到3.2 V 時，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流不(bu)再跟(gen)隨電(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)勢(shi)變化。當電(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)勢(shi)為3.2 V 時，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流最大，為256 mA。導(dao)致充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流突(tu)變的原因是升(sheng)壓器件(jian)MAX1* 在不(bu)同輸(shu)入電(dian)(dian)(dian)(dian)壓下轉換(huan)效率不(bu)同。由(you)于MAX1* 在超過3 V 電(dian)(dian)(dian)(dian)壓下工作時轉換(huan)效率低，所(suo)以充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流出現(xian)非(fei)線性的突(tu)變。

　　6）當(dang)Es≥1.1 V 時，取Rs =1 Ω；當(dang)Es＜1.1 V 時，取Rs=0.1 Ω。測量向電(dian)池(chi)充電(dian)的Es，記錄數據如表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。