太陽能電池板的便攜式充電器是(shi)解(jie)決(jue)通(tong)信設備(bei)、田間(jian)測量儀器等移動(dong)(dong)式電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)產品供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)問題(ti)的(de)(de)最佳解(jie)決(jue)方案之一(yi)。采用TPS5430 降(jiang)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路和MAX167 4 升壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路，由LM393、ICL7660 等元件(jian)構(gou)成的(de)(de)切換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路為(wei)(wei)控制核心，設計具有自(zi)啟動(dong)(dong)功能的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能收集充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器。充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器能夠根據(ju)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)不同，自(zi)動(dong)(dong)切換到不同的(de)(de)DC-DC 變換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路，實現高效、快速(su)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。測試(shi)表明，當(dang)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源內(nei)阻Rs為(wei)(wei)100 Ω，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)Es在10～20 V 范圍內(nei)，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)勢Ec為(wei)(wei)3.6 V、內(nei)阻Rc為(wei)(wei)0.1 Ω 時，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流Ic>58 mA，自(zi)動(dong)(dong)啟動(dong)(dong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)(wei)3.6 V，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流為(wei)(wei)3 mA；而當(dang)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源內(nei)阻Rs為(wei)(wei)1 Ω，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)Es在1.2～3.6 V 范圍內(nei)時，最大充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(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(zhi)流(liu)電(dian)源(yuan)模擬(ni)當(dang)太陽(yang)能(neng)電(dian)池板的(de)輸出電(dian)壓(ya)大(da)范圍變化時，實(shi)(shi)現充電(dian)器的(de)自(zi)動啟動并盡可能(neng)地增大(da)充電(dian)電(dian)流(liu)來實(shi)(shi)現充電(dian)效率的(de)提高(gao)。

　　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。可充電池的電動勢Ec恒定為(wei)3.6 V，內阻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(you)此(ci)可得，當Rs=100 Ω，Es=10 V 時，Ps=0.25 W，Ic>64 mA，η >92.16%；當Es=20 V 時，Ps=1 W，Ic>160 mA，η>57.6%。為(wei)了盡(jin)可能提高(gao)高(gao)電(dian)(dian)壓時的(de)充電(dian)(dian)效率，除選用TPS5430 構成(cheng)降(jiang)(jiang)壓電(dian)(dian)路外，應盡(jin)量降(jiang)(jiang)低切換(huan)電(dian)(dian)路的(de)開關(guan)頻(pin)(pin)率。電(dian)(dian)路中(zhong)主要功耗(hao)(hao)元件是功率場效應管（FET），在低頻(pin)(pin)情況(kuang)下，功率FET 主要是傳(chuan)導(dao)損耗(hao)(hao)，在高(gao)頻(pin)(pin)情況(kuang)下，傳(chuan)導(dao)損耗(hao)(hao)維持不(bu)變，同頻(pin)(pin)率有(you)關(guan)的(de)損耗(hao)(hao)會(hui)(hui)增大。較高(gao)或(huo)較低的(de)開關(guan)頻(pin)(pin)率均會(hui)(hui)使效率降(jiang)(jiang)低，綜合(he)考慮(lv)各因(yin)素并結合(he)試驗，測得開關(guan)頻(pin)(pin)率為(wei)500 kHz 時效率為(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)(ya)(ya)(ya)工(gong)作和降壓(ya)(ya)(ya)(ya)(ya)(ya)工(gong)作兩種模式。設定切換(huan)的閾(yu)值電壓(ya)(ya)(ya)(ya)(ya)(ya)為3.6 V，閾(yu)值電壓(ya)(ya)(ya)(ya)(ya)(ya)由可調(diao)電阻設定并可調(diao)。充電電壓(ya)(ya)(ya)(ya)(ya)(ya)超過閾(yu)值電壓(ya)(ya)(ya)(ya)(ya)(ya)時降壓(ya)(ya)(ya)(ya)(ya)(ya)電路工(gong)作，低(di)于閾(yu)值電壓(ya)(ya)(ya)(ya)(ya)(ya)時升壓(ya)(ya)(ya)(ya)(ya)(ya)電路工(gong)作。切換(huan)電路由場(chang)效應管、電壓(ya)(ya)(ya)(ya)(ya)(ya)比較器等(deng)分立元件構成(cheng)，原理圖(tu)如圖(tu)3 所(suo)示。

　　圖3 中， 輸(shu)(shu)(shu)入(ru)端(duan)VIN （P1） 接充電(dian)電(dian)源， 輸(shu)(shu)(shu)出(chu)端(duan)P2 接MAX167 4升壓(ya)(ya)(ya)(ya)(ya)電(dian)路(lu)(lu)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)入(ru)端(duan)，肖特基(ji)二極管VD1用于(yu)(yu)(yu)防止電(dian)流倒(dao)灌(guan)。穩壓(ya)(ya)(ya)(ya)(ya)器(qi)TL431 為電(dian)壓(ya)(ya)(ya)(ya)(ya)比較器(qi)LM393 的(de)(de)(de)(de)(de)負(fu)(fu)輸(shu)(shu)(shu)入(ru)端(duan)提(ti)供參考(kao)電(dian)壓(ya)(ya)(ya)(ya)(ya)。輸(shu)(shu)(shu)入(ru)端(duan)VIN（P1）通過(guo)濾波后接入(ru)電(dian)壓(ya)(ya)(ya)(ya)(ya)比較器(qi)LM393 的(de)(de)(de)(de)(de)正輸(shu)(shu)(shu)入(ru)端(duan)。調(diao)節R_ad可(ke)調(diao)電(dian)阻，使(shi)輸(shu)(shu)(shu)入(ru)小于(yu)(yu)(yu)3.6 V 時(shi)(shi)電(dian)壓(ya)(ya)(ya)(ya)(ya)比較器(qi)LM393 輸(shu)(shu)(shu)出(chu)負(fu)(fu)電(dian)壓(ya)(ya)(ya)(ya)(ya)，P 溝道MOS 管IRLM16402VQ1、VQ2和(he)VQ3導通，VQ1，VQ2的(de)(de)(de)(de)(de)漏極連接升壓(ya)(ya)(ya)(ya)(ya)電(dian)路(lu)(lu)， 使(shi)切換電(dian)路(lu)(lu)輸(shu)(shu)(shu)入(ru)、輸(shu)(shu)(shu)出(chu)端(duan)短接，使(shi)充電(dian)電(dian)壓(ya)(ya)(ya)(ya)(ya)接至(zhi)升壓(ya)(ya)(ya)(ya)(ya)電(dian)路(lu)(lu)。當(dang)輸(shu)(shu)(shu)入(ru)大于(yu)(yu)(yu)3.6 V 時(shi)(shi)，輸(shu)(shu)(shu)出(chu)高電(dian)平，VQ1、VQ2和(he)VQ3截止，此時(shi)(shi)MAX167 4升壓(ya)(ya)(ya)(ya)(ya)電(dian)路(lu)(lu)無輸(shu)(shu)(shu)入(ru)。VD2、VD3的(de)(de)(de)(de)(de)作(zuo)用是當(dang)電(dian)壓(ya)(ya)(ya)(ya)(ya)大于(yu)(yu)(yu)3.6 V 時(shi)(shi)，LM393的(de)(de)(de)(de)(de)負(fu)(fu)電(dian)源端(duan)接地； 當(dang)電(dian)壓(ya)(ya)(ya)(ya)(ya)小于(yu)(yu)(yu)5.5 V 時(shi)(shi)，LM393 負(fu)(fu)電(dian)源通過(guo)VQ3接ICL7660 的(de)(de)(de)(de)(de)負(fu)(fu)電(dian)壓(ya)(ya)(ya)(ya)(ya)輸(shu)(shu)(shu)出(chu)引腳。

　　2.2 升壓/降壓電路設計

　　升(sheng)壓電(dian)路主要由升(sheng)壓式DC-DC 電(dian)源(yuan)轉換器MAX167 4組成(cheng)，升(sheng)壓后輸(shu)出4 V 直接對電(dian)池進行(xing)充電(dian)。MAX167 4升(sheng)壓電(dian)路如圖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(yi)削弱紋波對輸出電壓(ya)的影響。

　　降(jiang)壓電(dian)路主要(yao)由降(jiang)壓DC-DC 轉換器TPS5430 組成，降(jiang)壓后直接對電(dian)池進行充電(dian)。TPS5430 降(jiang)壓電(dian)路如圖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， 可得所需的(de)電(dian)感值是15.8 μH，選取內徑30 mm 的(de)鐵(tie)硅鋁磁(ci)芯自行繞制(zhi)的(de)電(dian)感值為18 μH，以(yi)保(bao)證(zheng)在額(e)定的(de)工作狀況(kuang)下(xia)不(bu)會出現磁(ci)飽和(he)。電(dian)阻R1、R2和(he)R3構成(cheng)反(fan)饋(kui)網絡(luo)， 將輸(shu)(shu)出電(dian)壓反(fan)饋(kui)到芯片的(de)VSNS 引腳，該芯片自動調節輸(shu)(shu)出電(dian)壓，保(bao)證(zheng)充(chong)電(dian)器輸(shu)(shu)出端(duan)輸(shu)(shu)出電(dian)壓恒定。

　　3 試驗結果及分析

　　1）電(dian)源內(nei)阻Rs=100 Ω，調(diao)整Es的(de)大小(xiao)，使其在10～20 V范圍內(nei)變化，記錄數(shu)據如表(biao)1 所示。

　　由表1 可見，在(zai)(zai)Es為(wei)10 V 時，實測充(chong)(chong)電(dian)電(dian)流(liu)與理論值存在(zai)(zai)5.9 mA 的(de)(de)偏差，充(chong)(chong)電(dian)電(dian)流(liu)低、充(chong)(chong)電(dian)器的(de)(de)轉換效(xiao)率不(bu)高可能與芯(xin)片的(de)(de)轉換效(xiao)率和輸(shu)入(ru)電(dian)壓(ya)(ya)有關，由TPS5430 的(de)(de)數據資料可知，在(zai)(zai)輸(shu)入(ru)電(dian)壓(ya)(ya)為(wei)10 V 左右，輸(shu)出(chu)電(dian)流(liu)約為(wei)60 mA 時，其(qi)工作效(xiao)率約為(wei)92%。而在(zai)(zai)12～20 V 范(fan)圍內，實測充(chong)(chong)電(dian)電(dian)流(liu)大于(yu)理論計算充(chong)(chong)電(dian)電(dian)流(liu)值。

　　2）逐漸(jian)降低(di)Es，直到充(chong)電(dian)電(dian)流Ic略大(da)于0 時(shi)，記錄對(dui)應(ying)的電(dian)源電(dian)壓(ya)Es，該電(dian)壓(ya)即為最低(di)可充(chong)電(dian)電(dian)壓(ya)。為保證準確性，對(dui)多個(ge)不同(tong)的電(dian)源電(dian)壓(ya)值進行測試，選取最優3 組(zu)數據記錄如表(biao)2 所示。

　　由表(biao)2 可見，當Es下降到3.6 V 時(shi)，充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為(wei)0，充(chong)電(dian)(dian)(dian)(dian)器不能再對(dui)電(dian)(dian)(dian)(dian)池(chi)進行充(chong)電(dian)(dian)(dian)(dian)，故(gu)最(zui)低可充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)為(wei)3.6 V。

　　3）從0 開始逐漸升高(gao)Es，Rs為0.1 Ω；當Es升高(gao)到高(gao)于(yu)1.1 V 時，更換Rs為1 Ω。然后繼續升高(gao)Es，直到充電電流(liu)略大于(yu)0，記錄此時的電源(yuan)電壓(ya)值，該電壓(ya)即為自動(dong)啟(qi)動(dong)充電功能(neng)的啟(qi)動(dong)電壓(ya)。為保證準確性，對多個(ge)不同(tong)的電源(yuan)電壓(ya)值進行測試，選取最優4 組數據記錄如表3 所示。

　　由表3 可見(jian)，當(dang)Es小于(yu)3.6 V 時，充(chong)電(dian)(dian)電(dian)(dian)流(liu)持續為(wei)(wei)0，一旦Es上升(sheng)到3.6 V 后，充(chong)電(dian)(dian)電(dian)(dian)流(liu)由0 開始增加，即自動啟動充(chong)電(dian)(dian)電(dian)(dian)壓為(wei)(wei)3.6 V。

　　4）Es降(jiang)低(di)到不(bu)能向電(dian)(dian)池充電(dian)(dian)，最(zui)(zui)低(di)至0 時(shi)，檢測放電(dian)(dian)電(dian)(dian)流。為保證準確性，對(dui)多個不(bu)同的電(dian)(dian)源(yuan)電(dian)(dian)壓值進行測試(shi)，選取最(zui)(zui)優3 組數據記(ji)錄如表4 所示(shi)。

　　由表4 可(ke)知， 當電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)動勢下(xia)降到(dao)最(zui)低(di)可(ke)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓時，電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)開始放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)為3 mA。考慮到(dao)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)受倒灌電(dian)(dian)(dian)(dian)(dian)(dian)阻Rd影(ying)響，改變Rd的(de)大小可(ke)改變放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。試(shi)驗表明，Rd=15 Ω 時放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)最(zui)小。

　　5）接上電源(yuan)內阻Rs=1 Ω，調整(zheng)Es，使其在1.2～3.6 V 范圍內變(bian)化。數據記(ji)錄如表5 所(suo)示。

　　由表5 可(ke)見，隨(sui)著電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)勢(shi)的增加，充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流也隨(sui)著增加，直到當Es達到3.2 V 時(shi)，充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流不(bu)再跟(gen)隨(sui)電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)勢(shi)變(bian)化。當電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)勢(shi)為(wei)(wei)3.2 V 時(shi)，充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流最大(da)，為(wei)(wei)256 mA。導致充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流突(tu)變(bian)的原因是升壓器件(jian)MAX1* 在不(bu)同輸(shu)入電(dian)(dian)(dian)(dian)壓下轉(zhuan)換效率不(bu)同。由于MAX1* 在超(chao)過3 V 電(dian)(dian)(dian)(dian)壓下工作(zuo)時(shi)轉(zhuan)換效率低(di)，所(suo)以充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流出(chu)現非線(xian)性的突(tu)變(bian)。

　　6）當(dang)Es≥1.1 V 時，取(qu)Rs =1 Ω；當(dang)Es＜1.1 V 時，取(qu)Rs=0.1 Ω。測量向電池充電的(de)Es，記錄數據如(ru)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(di)Es為(wei)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。