太陽能電池板的便攜式充電器是解決(jue)通信設備、田間(jian)測(ce)量儀器(qi)(qi)等(deng)移動(dong)式電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子產(chan)品(pin)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)問題(ti)的(de)(de)最(zui)佳解決(jue)方案之(zhi)一(yi)。采用TPS5430 降(jiang)壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)和MAX167 4 升壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，由LM393、ICL7660 等(deng)元件構(gou)成的(de)(de)切換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)為控(kong)制核心，設計具有自啟動(dong)功能(neng)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)收集充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)。充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)能(neng)夠(gou)根據充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)不同(tong)，自動(dong)切換到不同(tong)的(de)(de)DC-DC 變換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，實現(xian)高(gao)效(xiao)、快速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。測(ce)試(shi)表明，當充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源內(nei)(nei)(nei)阻Rs為100 Ω，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)Es在10～20 V 范(fan)圍內(nei)(nei)(nei)，充(chong)(chong)(chong)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)勢Ec為3.6 V、內(nei)(nei)(nei)阻Rc為0.1 Ω 時(shi)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流Ic>58 mA，自動(dong)啟動(dong)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為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3 mA；而當充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源內(nei)(nei)(nei)阻Rs為1 Ω，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)Es在1.2～3.6 V 范(fan)圍內(nei)(nei)(nei)時(shi)，最(zui)大充(chong)(chong)(chong)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(ke)調直流電(dian)源模擬當太陽能電(dian)池板的(de)輸出電(dian)壓大范(fan)圍變化時，實現充(chong)電(dian)器(qi)的(de)自動啟(qi)動并盡可(ke)能地增(zeng)大充(chong)電(dian)電(dian)流來實現充(chong)電(dian)效率的(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Ec恒定(ding)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%。為了盡可能提高高電(dian)壓(ya)時的充電(dian)效率(lv)，除選用TPS5430 構成(cheng)降(jiang)壓(ya)電(dian)路(lu)外，應盡量降(jiang)低切換電(dian)路(lu)的開關頻(pin)(pin)率(lv)。電(dian)路(lu)中(zhong)主(zhu)要(yao)功耗元件(jian)是功率(lv)場(chang)效應管（FET），在(zai)低頻(pin)(pin)情況(kuang)(kuang)下(xia)，功率(lv)FET 主(zhu)要(yao)是傳導(dao)(dao)損耗，在(zai)高頻(pin)(pin)情況(kuang)(kuang)下(xia)，傳導(dao)(dao)損耗維持不變，同頻(pin)(pin)率(lv)有關的損耗會增大。較高或較低的開關頻(pin)(pin)率(lv)均會使(shi)效率(lv)降(jiang)低，綜合考(kao)慮各因素(su)并結合試驗，測(ce)得開關頻(pin)(pin)率(lv)為500 kHz 時效率(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(gong)(gong)(gong)作(zuo)和降壓(ya)(ya)工(gong)(gong)(gong)作(zuo)兩種模(mo)式。設定(ding)切(qie)換的閾(yu)(yu)值電(dian)(dian)壓(ya)(ya)為3.6 V，閾(yu)(yu)值電(dian)(dian)壓(ya)(ya)由可(ke)調(diao)電(dian)(dian)阻設定(ding)并可(ke)調(diao)。充電(dian)(dian)電(dian)(dian)壓(ya)(ya)超過閾(yu)(yu)值電(dian)(dian)壓(ya)(ya)時降壓(ya)(ya)電(dian)(dian)路工(gong)(gong)(gong)作(zuo)，低(di)于(yu)閾(yu)(yu)值電(dian)(dian)壓(ya)(ya)時升壓(ya)(ya)電(dian)(dian)路工(gong)(gong)(gong)作(zuo)。切(qie)換電(dian)(dian)路由場(chang)效(xiao)應管、電(dian)(dian)壓(ya)(ya)比較器等分立元(yuan)件構成(cheng)，原(yuan)理圖如圖3 所示。

　　圖3 中， 輸(shu)(shu)(shu)入(ru)端(duan)(duan)VIN （P1） 接(jie)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)源， 輸(shu)(shu)(shu)出端(duan)(duan)P2 接(jie)MAX167 4升壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)的(de)輸(shu)(shu)(shu)入(ru)端(duan)(duan)，肖(xiao)特基二極(ji)管VD1用于防(fang)止(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)流倒灌(guan)。穩壓(ya)(ya)(ya)(ya)(ya)器TL431 為電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)比(bi)較器LM393 的(de)負(fu)(fu)輸(shu)(shu)(shu)入(ru)端(duan)(duan)提供參考電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)。輸(shu)(shu)(shu)入(ru)端(duan)(duan)VIN（P1）通(tong)過(guo)濾波后接(jie)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)比(bi)較器LM393 的(de)正(zheng)輸(shu)(shu)(shu)入(ru)端(duan)(duan)。調(diao)節(jie)R_ad可調(diao)電(dian)(dian)(dian)(dian)(dian)(dian)阻，使(shi)輸(shu)(shu)(shu)入(ru)小于3.6 V 時電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)比(bi)較器LM393 輸(shu)(shu)(shu)出負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)，P 溝道MOS 管IRLM16402VQ1、VQ2和VQ3導(dao)通(tong)，VQ1，VQ2的(de)漏(lou)極(ji)連接(jie)升壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)， 使(shi)切換電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)輸(shu)(shu)(shu)入(ru)、輸(shu)(shu)(shu)出端(duan)(duan)短(duan)接(jie)，使(shi)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)接(jie)至升壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。當(dang)(dang)輸(shu)(shu)(shu)入(ru)大(da)于3.6 V 時，輸(shu)(shu)(shu)出高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，VQ1、VQ2和VQ3截止(zhi)(zhi)，此時MAX167 4升壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)無輸(shu)(shu)(shu)入(ru)。VD2、VD3的(de)作用是當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)大(da)于3.6 V 時，LM393的(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)(dian)源端(duan)(duan)接(jie)地； 當(dang)(dang)電(dian)(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)(dian)源通(tong)過(guo)VQ3接(jie)ICL7660 的(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)輸(shu)(shu)(shu)出引腳。

　　2.2 升壓/降壓電路設計

　　升壓(ya)(ya)電(dian)路(lu)主(zhu)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4 V 直(zhi)接(jie)對電(dian)池(chi)進行充電(dian)。MAX167 4升壓(ya)(ya)電(dian)路(lu)如(ru)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(yi)削弱紋波(bo)對輸出電壓的影響。

　　降壓電路主要由降壓DC-DC 轉換器TPS5430 組成(cheng)，降壓后(hou)直接對電池進行充(chong)電。TPS5430 降壓電路如(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， 可得所(suo)需的(de)電(dian)(dian)(dian)(dian)感值是15.8 μH，選取內徑30 mm 的(de)鐵硅鋁磁芯(xin)(xin)自行(xing)繞制的(de)電(dian)(dian)(dian)(dian)感值為18 μH，以保(bao)證在(zai)額定的(de)工作狀況下(xia)不會出(chu)(chu)現磁飽和。電(dian)(dian)(dian)(dian)阻(zu)R1、R2和R3構成(cheng)反饋(kui)網絡， 將輸出(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)反饋(kui)到芯(xin)(xin)片的(de)VSNS 引(yin)腳，該芯(xin)(xin)片自動(dong)調節輸出(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)，保(bao)證充電(dian)(dian)(dian)(dian)器輸出(chu)(chu)端(duan)輸出(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)恒定。

　　3 試驗結果及分析

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

　　由表1 可見，在Es為(wei)10 V 時，實測充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)與理論值(zhi)存在5.9 mA 的(de)偏差，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)低、充(chong)電(dian)(dian)(dian)(dian)(dian)器的(de)轉(zhuan)(zhuan)換(huan)效率(lv)不高可能(neng)與芯片的(de)轉(zhuan)(zhuan)換(huan)效率(lv)和輸入電(dian)(dian)(dian)(dian)(dian)壓有(you)關，由TPS5430 的(de)數據資料可知(zhi)，在輸入電(dian)(dian)(dian)(dian)(dian)壓為(wei)10 V 左右，輸出電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)約(yue)為(wei)60 mA 時，其工作效率(lv)約(yue)為(wei)92%。而在12～20 V 范(fan)圍內，實測充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)大于理論計(ji)算(suan)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)值(zhi)。

　　2）逐漸降(jiang)低Es，直到充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流Ic略(lve)大于0 時，記(ji)錄對應的電(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)壓(ya)(ya)Es，該(gai)電(dian)(dian)(dian)壓(ya)(ya)即為(wei)最低可充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)。為(wei)保證準(zhun)確性，對多個不同(tong)的電(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)壓(ya)(ya)值(zhi)進(jin)行測試，選取(qu)最優(you)3 組數據記(ji)錄如(ru)表(biao)2 所示(shi)。

　　由表2 可見(jian)，當(dang)Es下降(jiang)到3.6 V 時，充電電流為0，充電器不能(neng)再對(dui)電池進行充電，故最低可充電電壓(ya)為3.6 V。

　　3）從0 開始(shi)逐漸升(sheng)高(gao)Es，Rs為(wei)0.1 Ω；當Es升(sheng)高(gao)到(dao)高(gao)于1.1 V 時(shi)，更換(huan)Rs為(wei)1 Ω。然(ran)后繼續升(sheng)高(gao)Es，直到(dao)充電(dian)(dian)電(dian)(dian)流略大于0，記錄此時(shi)的電(dian)(dian)源電(dian)(dian)壓(ya)(ya)值(zhi)，該(gai)電(dian)(dian)壓(ya)(ya)即(ji)為(wei)自動啟動充電(dian)(dian)功(gong)能的啟動電(dian)(dian)壓(ya)(ya)。為(wei)保證準確(que)性，對多個不同(tong)的電(dian)(dian)源電(dian)(dian)壓(ya)(ya)值(zhi)進行(xing)測試，選取最優4 組(zu)數據記錄如表3 所(suo)示(shi)。

　　由表3 可見，當Es小于3.6 V 時，充(chong)電電流(liu)持續為(wei)0，一旦Es上(shang)升到3.6 V 后，充(chong)電電流(liu)由0 開(kai)始增加，即(ji)自(zi)動啟動充(chong)電電壓為(wei)3.6 V。

　　4）Es降低到不能(neng)向電池充電，最(zui)低至0 時，檢測(ce)放電電流。為保證準確性，對多(duo)個不同的電源電壓值進行測(ce)試，選取(qu)最(zui)優3 組數據記錄如表4 所示。

　　由表(biao)4 可(ke)知(zhi)， 當電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)動勢下降到(dao)最低(di)可(ke)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓時，電(dian)(dian)(dian)(dian)池開始放(fang)(fang)電(dian)(dian)(dian)(dian)，放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流為3 mA。考慮(lv)到(dao)放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流受倒灌電(dian)(dian)(dian)(dian)阻(zu)Rd影響，改變Rd的大小(xiao)可(ke)改變放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流。試驗表(biao)明，Rd=15 Ω 時放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流最小(xiao)。

　　5）接上電源內阻(zu)Rs=1 Ω，調整Es，使其在1.2～3.6 V 范圍內變化。數據記錄如表5 所示(shi)。

　　由(you)表5 可見(jian)，隨著(zhu)電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)勢(shi)的(de)增加，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)也隨著(zhu)增加，直到當(dang)Es達到3.2 V 時(shi)，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)不再跟隨電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)勢(shi)變(bian)化。當(dang)電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)勢(shi)為3.2 V 時(shi)，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)最大(da)，為256 mA。導致充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)突(tu)變(bian)的(de)原因(yin)是升壓(ya)器件MAX1* 在不同輸入(ru)電(dian)(dian)(dian)壓(ya)下轉換效(xiao)率不同。由(you)于MAX1* 在超過3 V 電(dian)(dian)(dian)壓(ya)下工(gong)作時(shi)轉換效(xiao)率低，所以充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)出現非線性的(de)突(tu)變(bian)。

　　6）當Es≥1.1 V 時，取Rs =1 Ω；當Es＜1.1 V 時，取Rs=0.1 Ω。測量(liang)向(xiang)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。