太陽能電池板的便攜式充電器是(shi)解決通信設(she)備、田(tian)間測量儀器等移動(dong)式電(dian)(dian)(dian)(dian)子(zi)產(chan)品供電(dian)(dian)(dian)(dian)問題的(de)最(zui)佳(jia)解決方案之一。采用TPS5430 降壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)(lu)和MAX167 4 升壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)(lu)，由LM393、ICL7660 等元件(jian)構成的(de)切(qie)換電(dian)(dian)(dian)(dian)路(lu)(lu)為(wei)(wei)(wei)控制核心(xin)，設(she)計具有自(zi)(zi)啟動(dong)功能的(de)電(dian)(dian)(dian)(dian)能收(shou)集充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器。充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器能夠(gou)根據(ju)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)不同，自(zi)(zi)動(dong)切(qie)換到不同的(de)DC-DC 變換電(dian)(dian)(dian)(dian)路(lu)(lu)，實現高效、快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。測試表(biao)明，當(dang)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源內(nei)阻(zu)Rs為(wei)(wei)(wei)100 Ω，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)Es在10～20 V 范圍內(nei)，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)動(dong)勢Ec為(wei)(wei)(wei)3.6 V、內(nei)阻(zu)Rc為(wei)(wei)(wei)0.1 Ω 時，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)Ic>58 mA，自(zi)(zi)動(dong)啟動(dong)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)為(wei)(wei)(wei)3.6 V，電(dian)(dian)(dian)(dian)池放(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為(wei)(wei)(wei)3 mA；而當(dang)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源內(nei)阻(zu)Rs為(wei)(wei)(wei)1 Ω，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)Es在1.2～3.6 V 范圍內(nei)時，最(zui)大充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)可達(da)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(you)可調(diao)直流(liu)電(dian)源模擬(ni)當太(tai)陽能電(dian)池板的(de)輸出電(dian)壓大范圍(wei)變化時，實現充電(dian)器的(de)自動(dong)啟動(dong)并盡可能地(di)增大充電(dian)電(dian)流(liu)來實現充電(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(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。由此可(ke)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%。為了盡(jin)可(ke)能提高(gao)(gao)高(gao)(gao)電(dian)壓時的充(chong)電(dian)效(xiao)率(lv)(lv)(lv)，除選用(yong)TPS5430 構成降(jiang)壓電(dian)路外，應盡(jin)量降(jiang)低(di)切(qie)換(huan)電(dian)路的開關(guan)頻(pin)(pin)率(lv)(lv)(lv)。電(dian)路中(zhong)主(zhu)要功(gong)耗(hao)元件是(shi)功(gong)率(lv)(lv)(lv)場效(xiao)應管（FET），在低(di)頻(pin)(pin)情(qing)況下(xia)，功(gong)率(lv)(lv)(lv)FET 主(zhu)要是(shi)傳導損(sun)耗(hao)，在高(gao)(gao)頻(pin)(pin)情(qing)況下(xia)，傳導損(sun)耗(hao)維持不變(bian)，同頻(pin)(pin)率(lv)(lv)(lv)有關(guan)的損(sun)耗(hao)會增大(da)。較(jiao)高(gao)(gao)或較(jiao)低(di)的開關(guan)頻(pin)(pin)率(lv)(lv)(lv)均會使(shi)效(xiao)率(lv)(lv)(lv)降(jiang)低(di)，綜合考慮各因素(su)并結(jie)合試驗，測得開關(guan)頻(pin)(pin)率(lv)(lv)(lv)為500 kHz 時效(xiao)率(lv)(lv)(lv)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)工作和降壓(ya)(ya)工作兩種模式。設(she)定切換(huan)的閾值電(dian)(dian)壓(ya)(ya)為3.6 V，閾值電(dian)(dian)壓(ya)(ya)由(you)可(ke)調(diao)電(dian)(dian)阻設(she)定并(bing)可(ke)調(diao)。充電(dian)(dian)電(dian)(dian)壓(ya)(ya)超(chao)過閾值電(dian)(dian)壓(ya)(ya)時(shi)降壓(ya)(ya)電(dian)(dian)路(lu)工作，低于閾值電(dian)(dian)壓(ya)(ya)時(shi)升壓(ya)(ya)電(dian)(dian)路(lu)工作。切換(huan)電(dian)(dian)路(lu)由(you)場效應管、電(dian)(dian)壓(ya)(ya)比較器(qi)等分立(li)元件構(gou)成，原(yuan)理(li)圖(tu)如圖(tu)3 所示(shi)。

　　圖3 中， 輸入(ru)(ru)端(duan)(duan)(duan)VIN （P1） 接(jie)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)， 輸出(chu)端(duan)(duan)(duan)P2 接(jie)MAX167 4升(sheng)(sheng)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)的輸入(ru)(ru)端(duan)(duan)(duan)，肖特(te)基二極(ji)管VD1用于(yu)(yu)防止電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流倒灌。穩壓(ya)(ya)(ya)(ya)器TL431 為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)比較(jiao)器LM393 的負(fu)輸入(ru)(ru)端(duan)(duan)(duan)提供參考電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。輸入(ru)(ru)端(duan)(duan)(duan)VIN（P1）通過濾波(bo)后接(jie)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)比較(jiao)器LM393 的正輸入(ru)(ru)端(duan)(duan)(duan)。調節(jie)R_ad可調電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，使輸入(ru)(ru)小于(yu)(yu)3.6 V 時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)比較(jiao)器LM393 輸出(chu)負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)，P 溝道(dao)MOS 管IRLM16402VQ1、VQ2和VQ3導通，VQ1，VQ2的漏極(ji)連接(jie)升(sheng)(sheng)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)， 使切換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)輸入(ru)(ru)、輸出(chu)端(duan)(duan)(duan)短接(jie)，使充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)接(jie)至升(sheng)(sheng)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。當(dang)(dang)輸入(ru)(ru)大(da)于(yu)(yu)3.6 V 時(shi)，輸出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，VQ1、VQ2和VQ3截止，此時(shi)MAX167 4升(sheng)(sheng)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)無輸入(ru)(ru)。VD2、VD3的作(zuo)用是當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)大(da)于(yu)(yu)3.6 V 時(shi)，LM393的負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)端(duan)(duan)(duan)接(jie)地； 當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)小于(yu)(yu)5.5 V 時(shi)，LM393 負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)通過VQ3接(jie)ICL7660 的負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)輸出(chu)引腳(jiao)。

　　2.2 升壓/降壓電路設計

　　升壓電路主要由升壓式DC-DC 電源轉換器MAX167 4組成，升壓后輸出4 V 直接(jie)對(dui)電池進(jin)行充電。MAX167 4升壓電路如圖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，以削弱紋波對(dui)輸(shu)出電壓(ya)的影響。

　　降(jiang)壓電(dian)路(lu)主要(yao)由(you)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(lu)如(ru)圖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的取值按公式計算(suan)， 可得所(suo)需的電(dian)感值(zhi)是(shi)15.8 μH，選取內徑(jing)30 mm 的鐵硅鋁(lv)磁芯自(zi)行繞制(zhi)的電(dian)感值(zhi)為18 μH，以保證(zheng)在額(e)定的工作(zuo)狀況下不會出(chu)(chu)現(xian)磁飽和。電(dian)阻R1、R2和R3構成反(fan)饋網絡， 將輸(shu)(shu)出(chu)(chu)電(dian)壓反(fan)饋到(dao)芯片的VSNS 引(yin)腳，該(gai)芯片自(zi)動調節輸(shu)(shu)出(chu)(chu)電(dian)壓，保證(zheng)充電(dian)器(qi)輸(shu)(shu)出(chu)(chu)端輸(shu)(shu)出(chu)(chu)電(dian)壓恒定。

　　3 試驗結果及分析

　　1）電源內(nei)阻(zu)Rs=100 Ω，調整(zheng)Es的大小，使其在10～20 V范圍內(nei)變化，記錄數據如(ru)表1 所示(shi)。

　　由表1 可(ke)(ke)見，在Es為(wei)10 V 時(shi)，實(shi)測充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)與理論(lun)值存(cun)在5.9 mA 的偏差(cha)，充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)低(di)、充電(dian)(dian)(dian)器的轉(zhuan)換效(xiao)率不高可(ke)(ke)能與芯片的轉(zhuan)換效(xiao)率和輸入電(dian)(dian)(dian)壓(ya)有關，由TPS5430 的數據資料(liao)可(ke)(ke)知，在輸入電(dian)(dian)(dian)壓(ya)為(wei)10 V 左右，輸出電(dian)(dian)(dian)流(liu)約為(wei)60 mA 時(shi)，其(qi)工(gong)作效(xiao)率約為(wei)92%。而在12～20 V 范(fan)圍內，實(shi)測充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)大于理論(lun)計算充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)值。

　　2）逐漸(jian)降低(di)Es，直到充(chong)電(dian)(dian)電(dian)(dian)流Ic略大(da)于(yu)0 時，記錄(lu)對應的(de)電(dian)(dian)源電(dian)(dian)壓(ya)Es，該電(dian)(dian)壓(ya)即為最低(di)可充(chong)電(dian)(dian)電(dian)(dian)壓(ya)。為保證(zheng)準確性，對多(duo)個不(bu)同的(de)電(dian)(dian)源電(dian)(dian)壓(ya)值進行測試，選取最優(you)3 組(zu)數(shu)據(ju)記錄(lu)如表2 所(suo)示。

　　由表2 可見，當(dang)Es下(xia)降到3.6 V 時，充電(dian)電(dian)流為0，充電(dian)器不(bu)能再對電(dian)池進行充電(dian)，故最低可充電(dian)電(dian)壓(ya)為3.6 V。

　　3）從0 開始逐漸升(sheng)高(gao)Es，Rs為0.1 Ω；當Es升(sheng)高(gao)到(dao)高(gao)于1.1 V 時，更換(huan)Rs為1 Ω。然后(hou)繼續升(sheng)高(gao)Es，直到(dao)充電(dian)電(dian)流略大于0，記(ji)(ji)錄此時的電(dian)源電(dian)壓值，該電(dian)壓即(ji)為自動啟動充電(dian)功能的啟動電(dian)壓。為保(bao)證準確性，對多個不(bu)同(tong)的電(dian)源電(dian)壓值進行測試，選取最優(you)4 組(zu)數據記(ji)(ji)錄如(ru)表3 所(suo)示。

　　由(you)表3 可見，當(dang)Es小于3.6 V 時，充(chong)電電流(liu)持續(xu)為0，一(yi)旦(dan)Es上升到3.6 V 后，充(chong)電電流(liu)由(you)0 開始增加，即(ji)自動啟動充(chong)電電壓為3.6 V。

　　4）Es降低到不(bu)能(neng)向(xiang)電(dian)(dian)池充(chong)電(dian)(dian)，最低至(zhi)0 時(shi)，檢測放電(dian)(dian)電(dian)(dian)流。為保證準(zhun)確性，對多(duo)個不(bu)同的電(dian)(dian)源電(dian)(dian)壓(ya)值進行測試，選取最優3 組數據記錄如表4 所示(shi)。

　　由表4 可(ke)知， 當電源電動勢下降到最低可(ke)充電電壓時(shi)，電池開始放(fang)(fang)電，放(fang)(fang)電電流為3 mA。考慮到放(fang)(fang)電電流受倒灌電阻Rd影響，改變Rd的(de)大小可(ke)改變放(fang)(fang)電電流。試驗(yan)表明，Rd=15 Ω 時(shi)放(fang)(fang)電電流最小。

　　5）接(jie)上(shang)電(dian)源(yuan)內(nei)阻Rs=1 Ω，調整Es，使其在1.2～3.6 V 范圍內(nei)變化(hua)。數據記錄如(ru)表5 所(suo)示。

　　由表5 可見，隨(sui)(sui)著電(dian)源(yuan)(yuan)電(dian)勢的(de)增加，充(chong)電(dian)電(dian)流(liu)也隨(sui)(sui)著增加，直到(dao)當Es達到(dao)3.2 V 時，充(chong)電(dian)電(dian)流(liu)不再(zai)跟隨(sui)(sui)電(dian)源(yuan)(yuan)電(dian)勢變化(hua)。當電(dian)源(yuan)(yuan)電(dian)勢為3.2 V 時，充(chong)電(dian)電(dian)流(liu)最大，為256 mA。導致充(chong)電(dian)電(dian)流(liu)突變的(de)原因是(shi)升壓器件MAX1* 在不同輸入電(dian)壓下(xia)轉換效率不同。由于MAX1* 在超過3 V 電(dian)壓下(xia)工(gong)作時轉換效率低，所(suo)以充(chong)電(dian)電(dian)流(liu)出現非線性(xing)的(de)突變。

　　6）當(dang)(dang)Es≥1.1 V 時，取(qu)Rs =1 Ω；當(dang)(dang)Es＜1.1 V 時，取(qu)Rs=0.1 Ω。測(ce)量向電(dian)池(chi)充電(dian)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。