無需昂貴散熱器的太陽能電池充電器
太陽能電池板的泄漏問題傳統上可以采用一個與太陽能電池板相串聯的肖特基二極管來解決,但肖特基二極管的正向電壓降使得它在高電流條件下會消耗大量的功率。因此,需要采用昂貴的散熱器和精細的布局來把肖特基二極管保持于低溫狀態。那么,有沒有低成本的解決方案?太陽能電池充電器設計最困(kun)擾(rao)設計師的“至滿充電(dian)電(dian)池(chi)的浮(fu)動電(dian)壓控制”和“在最佳發電(dian)點給電(dian)池(chi)板加(jia)載”問題(ti)又該(gai)如(ru)何解決?在下文中,Linear電(dian)源專家將為你介(jie)紹該(gai)公司最新的低成(cheng)本解決方案(an)。
作為在商業(ye)和(he)住(zhu)宅環境(jing)中均具實用性(xing)的一種發(fa)電(dian)方法而言(yan),太(tai)陽(yang)能電(dian)池板已經被人們所廣泛接(jie)受(shou)。然而,盡管在技術方面(mian)取得(de)了(le)進步,太(tai)陽(yang)能電(dian)池板的造價仍然很昂貴。這種高昂的成(cheng)(cheng)本有很大(da)部分來自于電(dian)池板本身,這里,電(dian)池板的尺寸(因(yin)而也包括(kuo)其(qi)成(cheng)(cheng)本)將隨著所需輸(shu)出(chu)功(gong)率的增加(jia)而增加(jia)。因(yin)此,為了(le)造就外形尺寸最(zui)小、成(cheng)(cheng)本效益性(xing)最(zui)佳的解(jie)決方案,最(zui)大(da)限度地提升電(dian)池板性(xing)能是很重要的。
一般而(er)言(yan),太(tai)陽(yang)(yang)(yang)能(neng)(neng)(neng)(neng)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)所獲取的(de)能(neng)(neng)(neng)(neng)量(liang)用于給電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian),電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)儲能(neng)(neng)(neng)(neng)反(fan)過(guo)來將(jiang)在(zai)沒(mei)有(you)陽(yang)(yang)(yang)光(guang)照射的(de)情況下為終端應用電(dian)(dian)(dian)(dian)路(lu)的(de)操(cao)作提供支持(chi)(chi)。如(ru)欲實(shi)現太(tai)陽(yang)(yang)(yang)能(neng)(neng)(neng)(neng)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)器的(de)最(zui)佳設(she)計,則必需對太(tai)陽(yang)(yang)(yang)能(neng)(neng)(neng)(neng)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)的(de)特(te)性(xing)有(you)所了解。首先,由于具有(you)很大的(de)結(jie)合區,因此太(tai)陽(yang)(yang)(yang)能(neng)(neng)(neng)(neng)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)會發生(sheng)泄漏,在(zai)黑暗條件下電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)將(jiang)通過(guo)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)放電(dian)(dian)(dian)(dian)。而(er)且,每塊太(tai)陽(yang)(yang)(yang)能(neng)(neng)(neng)(neng)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)都擁(yong)有(you)一個具最(zui)大功率點的(de)特(te)征IV曲線,所以(yi),當負載特(te)性(xing)與電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)特(te)性(xing)不(bu)相(xiang)匹配時,能(neng)(neng)(neng)(neng)量(liang)提取將(jiang)有(you)所減少。理想的(de)情況是:電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)將(jiang)在(zai)最(zui)大功率點上被(bei)持(chi)(chi)續(xu)加載,以(yi)充(chong)分地利用可用的(de)太(tai)陽(yang)(yang)(yang)能(neng)(neng)(neng)(neng),并(bing)由此最(zui)大限度地縮減電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)板(ban)(ban)成本。
一般(ban)情(qing)況下,可以(yi)采用一個與(yu)電(dian)池板相串聯的(de)(de)(de)肖(xiao)(xiao)特(te)基二(er)(er)(er)極管來解(jie)(jie)決電(dian)池板的(de)(de)(de)泄漏問(wen)題(ti)。反(fan)向(xiang)(xiang)(xiang)泄漏被(bei)減小至一個很低(di)的(de)(de)(de)數(shu)值(zhi);然(ran)而,肖(xiao)(xiao)特(te)基二(er)(er)(er)極管的(de)(de)(de)正向(xiang)(xiang)(xiang)電(dian)壓降(它(ta)在高電(dian)流條件下會消耗(hao)大量(liang)的(de)(de)(de)功(gong)率)仍(reng)然(ran)會造成能(neng)量(liang)損失。因此,需要采用昂貴的(de)(de)(de)散(san)熱(re)器和精(jing)細的(de)(de)(de)布局來把(ba)肖(xiao)(xiao)特(te)基二(er)(er)(er)極管保持于低(di)溫(wen)狀態。解(jie)(jie)決該功(gong)率耗(hao)散(san)問(wen)題(ti)的(de)(de)(de)一種更(geng)加有(you)效(xiao)方法是(shi)用一個基于MOSFET的(de)(de)(de)理想二(er)(er)(er)極管來替代(dai)肖(xiao)(xiao)特(te)基二(er)(er)(er)極管。這將把(ba)正向(xiang)(xiang)(xiang)電(dian)壓降減小到低(di)至20mV,從而顯著地減少(shao)功(gong)耗(hao),同時降低(di)散(san)熱(re)布局的(de)(de)(de)復雜性、外形尺寸和成本。幸(xing)運的(de)(de)(de)是(shi),由(you)于已經有(you)一些(xie)IC供應商制造出了具有(you)這種規格(ge)的(de)(de)(de)理想二(er)(er)(er)極管(比(bi)如:由(you)凌力(li)爾特(te)公司(si)提供的(de)(de)(de)LTC4412),因此上述目標得以(yi)輕松實現。
不過,有兩個問題依然存在,即:“至滿充電電池的浮動電壓控制”和“在最佳發電點給電池板加載”。這些問題常常可以通過采用一個開關模式充電器和一個高(gao)效率(lv)降壓型穩(wen)壓器來加以(yi)解決。
凌力爾特已經開發出了(le)這樣一款電(dian)(dian)路(lu),它由(you)LTC1625 No RESNSE(無檢測電(dian)(dian)阻器(qi))同(tong)步降壓型控(kong)制器(qi)、LTC1541微功率運算放大器(qi)、比較器(qi)和基準、以及LTC4412理想二極(ji)管組成(cheng)。下面給出了(le)該電(dian)(dian)路(lu)以供參(can)考:
圖1中(zhong)的(de)(de)電(dian)(dian)路(lu)被置于(yu)太陽(yang)能電(dian)(dian)池(chi)(chi)板(ban)和電(dian)(dian)池(chi)(chi)之(zhi)間,用于(yu)調節電(dian)(dian)池(chi)(chi)浮(fu)動電(dian)(dian)壓。基于(yu)LTC1541的(de)(de)附加控制(zhi)環(huan)路(lu)強制(zhi)充電(dian)(dian)器在(zai)最(zui)大(da)電(dian)(dian)池(chi)(chi)板(ban)功(gong)率(lv)點上(shang)運作。這(zhe)(zhe)種效率(lv)的(de)(de)提升縮減了所需的(de)(de)電(dian)(dian)池(chi)(chi)板(ban)尺(chi)寸,因而(er)降低了總體解決(jue)方(fang)案的(de)(de)成(cheng)本。當(dang)電(dian)(dian)池(chi)(chi)板(ban)峰值(zhi)電(dian)(dian)源(yuan)電(dian)(dian)壓和電(dian)(dian)池(chi)(chi)電(dian)(dian)壓之(zhi)間存在(zai)失(shi)配時,這(zhe)(zhe)款電(dian)(dian)路(lu)的(de)(de)重要優點表現得尤(you)為突(tu)出。