在各大中型城市中一大批智能化小區、花園別墅、智能大型綜合體育設施等建筑拔地而起， 客觀上要求有與其相配套的高效能環保的照明設備的出現。LED 是發光二極管的統稱， 它工作在低電壓、小電流的狀態下， 所以具有發熱量小、功耗低的顯著特征。而且其使用方面， 可以根據不同場合的使用要求方便地進行多顆LED 的組合。所以在LED 技術基礎上發展起來的LED 光伏路燈是一種新型環保且具有高光效的節能設備， 具有安全抗震、使用方便、費用低、壽命長、節約能源、無污染等優點， 在許多領域可代替現在廣泛使用的白熾燈、日光燈等光效相對較低的照明設備。其工作原理就是通過太陽電池光伏陣列將太陽能轉化為電能， 給蓄電池進行充電， LED 驅動器則通過蓄電池為其提供工作電源， 完成對LED 燈的驅動和保護功能。其優點是克服了目前市場上所使用的其它照明設備普遍存在的耗能大、光效差、不穩定、蓄電池使用壽命短等多種弊端。大功率LED 路燈充電器設計的一個關鍵的部分就是光伏充電器的(de)設(she)計問題， 因為(wei)光(guang)(guang)伏充(chong)(chong)電(dian)器不僅完成了把太陽能(neng)轉換成電(dian)能(neng)的(de)重任(ren)， 而且還(huan)對蓄電(dian)池提(ti)供了智能(neng)充(chong)(chong)電(dian)管理(li)， 因此光(guang)(guang)伏充(chong)(chong)電(dian)器的(de)性能(neng)直接(jie)決(jue)定了太陽能(neng)能(neng)量利用的(de)效(xiao)率和系統使(shi)用的(de)壽命。本文從原理(li)、控制(zhi)策(ce)略和實際(ji)應用等幾個方(fang)面介紹一種光(guang)(guang)伏充(chong)(chong)電(dian)器及其控制(zhi)系統的(de)設(she)計思想。

　　1 系統構成

　　1.1 LED 的工(gong)作特性(xing)

　　發光二極管LED（Light Emitting Diode）的(de)工作原理(li)是(shi)(shi)在半導(dao)體p-n 結上加一正(zheng)向電(dian)壓， 從而使其(qi)電(dian)子(zi)與(yu)(yu)空穴復合(he)（即(ji)結區變窄(zhai)）， 這種復合(he)是(shi)(shi)電(dian)子(zi)從高能級的(de)導(dao)帶(dai)釋(shi)放能量(liang)(liang)回到價帶(dai)與(yu)(yu)空穴復合(he)， 其(qi)釋(shi)放的(de)能量(liang)(liang)以光子(zi)的(de)形式(shi)出現， 即(ji)發光。

　　根據半導體(ti)(ti)物理中(zhong)的(de)(de)公式： λ=1.24/Eg式中(zhong)： Eg 為(wei)半導體(ti)(ti)材料(liao)導帶與(yu)(yu)價帶之間的(de)(de)禁帶寬度(du)， λ為(wei)波(bo)長(chang)。從式中(zhong)可以(yi)(yi)(yi)看出， 對(dui)于不同材料(liao)的(de)(de)半導體(ti)(ti)來(lai)說， 由(you)于它們的(de)(de)Eg 不同， 因此它們的(de)(de)波(bo)長(chang)# 也不一樣(yang)， 所(suo)以(yi)(yi)(yi)發光(guang)(guang)(guang)(guang)(guang)(guang)(guang)的(de)(de)顏(yan)色不同。顯然， 一般LED 多(duo)(duo)為(wei)單(dan)顏(yan)色光(guang)(guang)(guang)(guang)(guang)(guang)(guang)， 如紅光(guang)(guang)(guang)(guang)(guang)(guang)(guang)、綠光(guang)(guang)(guang)(guang)(guang)(guang)(guang)、黃(huang)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)、藍(lan)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)等。所(suo)謂白(bai)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)是多(duo)(duo)種顏(yan)色的(de)(de)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)混合而成， 以(yi)(yi)(yi)人類眼睛所(suo)能見到(dao)的(de)(de)白(bai)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)形(xing)式至少必(bi)須兩種以(yi)(yi)(yi)上(shang)的(de)(de)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)混合， 一般有下列兩種混合方(fang)式： 二(er)波(bo)長(chang)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)―――藍(lan)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)與(yu)(yu)黃(huang)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)混合； 三(san)波(bo)長(chang)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)―――紅光(guang)(guang)(guang)(guang)(guang)(guang)(guang)、綠光(guang)(guang)(guang)(guang)(guang)(guang)(guang)與(yu)(yu)藍(lan)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)混合。目前已經商品化(hua)的(de)(de)白(bai)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)LED 產品多(duo)(duo)為(wei)二(er)波(bo)段(duan)藍(lan)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)單(dan)晶(jing)片加(jia)(jia)上(shang)YAG 黃(huang)色熒(ying)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)粉； 三(san)波(bo)長(chang)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)以(yi)(yi)(yi)無機(ji)紫(zi)外線光(guang)(guang)(guang)(guang)(guang)(guang)(guang)晶(jing)片加(jia)(jia)R、G、B 三(san)顏(yan)色熒(ying)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)粉。此外， 有機(ji)單(dan)層三(san)波(bo)長(chang)型白(bai)光(guang)(guang)(guang)(guang)(guang)(guang)(guang)LED 也有成本低、制作容(rong)易等優點。

　　1.2 太陽(yang)電池的工作特性

　　圖1、圖2 分別給出了太陽(yang)電池(chi)溫度(du)在25 ℃時， 工作電壓、電流和(he)日(ri)(ri)照(zhao)（ W/m2） 的關系(xi)曲線(xian)及(ji)太陽(yang)電池(chi)的輸出功(gong)率和(he)日(ri)(ri)照(zhao)、電壓之間的曲線(xian)。

　　從(cong)圖(tu)1 的(de)(de)I/U 關系(xi)可(ke)以看出， 太陽(yang)電(dian)(dian)池(chi)陣列既非恒(heng)壓源，也非恒(heng)流源， 而是(shi)(shi)一種非線性直流電(dian)(dian)源， 電(dian)(dian)池(chi)輸出電(dian)(dian)流在(zai)大(da)(da)部分(fen)工(gong)(gong)作(zuo)電(dian)(dian)壓范圍內相(xiang)當(dang)恒(heng)定(ding)， 最終在(zai)一個足(zu)夠高的(de)(de)電(dian)(dian)壓之后，電(dian)(dian)流迅速下降至零。由圖(tu)2 可(ke)知(zhi)， 太陽(yang)電(dian)(dian)池(chi)的(de)(de)工(gong)(gong)作(zuo)效(xiao)率(lv)等(deng)于輸出功(gong)率(lv)與(yu)投射到(dao)太陽(yang)電(dian)(dian)池(chi)面積上的(de)(de)功(gong)率(lv)之比。因此， 為了提高本系(xi)統(tong)的(de)(de)工(gong)(gong)作(zuo)效(xiao)率(lv)， 必(bi)須(xu)盡可(ke)能地使太陽(yang)電(dian)(dian)池(chi)在(zai)最大(da)(da)功(gong)率(lv)點處工(gong)(gong)作(zuo)， 這樣就(jiu)可(ke)以用功(gong)率(lv)盡可(ke)能小的(de)(de)太陽(yang)電(dian)(dian)池(chi)獲得(de)最大(da)(da)的(de)(de)功(gong)率(lv)輸出， 這就(jiu)是(shi)(shi)進行(xing)最大(da)(da)功(gong)率(lv)點跟蹤的(de)(de)意義所在(zai)。如圖(tu)1 和圖(tu)2 所示， 圖(tu)中的(de)(de)A、B、C、D、E 點分(fen)別對(dui)應不(bu)同(tong)日(ri)照時(shi)的(de)(de)最大(da)(da)功(gong)率(lv)點。

　　1.3 鉛酸(suan)蓄電池的工作特性

　　目前在光伏充(chong)電(dian)器系統中大量使(shi)用(yong)的(de)是鉛(qian)酸蓄(xu)電(dian)池， 它的(de)工作(zuo)原理是依(yi)靠鉛(qian)酸正(zheng)極(ji)(ji)的(de)活性物質(zhi)二(er)氧(yang)化(hua)鉛(qian)（ PbO2） 和負極(ji)(ji)的(de)活性物質(zhi)海綿狀(zhuang)鉛(qian)（ Pb） 與電(dian)解液(ye)硫(liu)酸（ H2SO4） 進(jin)行化(hua)學反應生(sheng)(sheng)成硫(liu)酸鉛(qian)（ PbSO4） , 在此工作(zuo)過程中將引起硫(liu)酸（ H2SO4） 的(de)減(jian)少， 而(er)且在正(zheng)極(ji)(ji)板上(shang)不斷生(sheng)(sheng)成水（ H2O） , 從(cong)而(er)引起電(dian)解液(ye)的(de)密度降低。在充(chong)電(dian)期間， 正(zheng)極(ji)(ji)極(ji)(ji)板上(shang)的(de)硫(liu)酸鉛(qian)（ PbSO4） 氧(yang)化(hua)成了(le)二(er)氧(yang)化(hua)鉛(qian)（ PbO2） , 此時負極(ji)(ji)極(ji)(ji)板上(shang)的(de)硫(liu)酸鉛(qian)（ PbSO4） 還原成鉛(qian)（ Pb） , 同時生(sheng)(sheng)成硫(liu)酸（ H2SO4） , 耗去了(le)蓄(xu)電(dian)池中的(de)水（ H2O） , 使(shi)電(dian)池中電(dian)解液(ye)的(de)密度上(shang)升， 完成充(chong)電(dian)過程。

　　2 系統(tong)的工(gong)作原理

　　2.1 系統(tong)的主(zhu)控制芯片介紹

　　充電器系統的(de)硬件(jian)框圖如圖3 所示。

　　主控芯片采用(yong)Microchip 公司的(de)PIC16F874, 它(ta)采用(yong)RISC 指令系統(tong)， 哈(ha)佛總(zong)線結構， 低功耗， 高速度(du)。內(nei)部集成了ADC、SPI 和Flash 程序(xu)存儲(chu)器(qi)等模塊(kuai)， 具(ju)有10 位A/ D 轉換、PWM 輸(shu)出、LCD 驅動等功能， 此外它(ta)還(huan)帶(dai)有128 個字節的(de)E2PROM 存儲(chu)器(qi)， 能方便寫入調整量以(yi)備后(hou)用(yong)。PIC16F874通過SPI 接口(kou)(kou)可以(yi)實現(xian)與(yu)(yu)CAN 控制器(qi)MCP2510 的(de)無縫(feng)連接， 且同時同步(bu)串行模塊(kuai)（ SSP） 為以(yi)后(hou)與(yu)(yu)工控機聯網奠定了基礎(chu)。PIC16F874 的(de)I/O 資源(yuan)豐(feng)富(fu)， 共(gong)有A、B、C、D、E 五個I/O口(kou)(kou)， 每個I/O 口(kou)(kou)除了基本用(yong)途外還(huan)有一(yi)些特殊功能。豐(feng)富(fu)的(de)資源(yuan)和強(qiang)大的(de)功能， 使之十分適合于作為控制系統(tong)的(de)控制核心芯片。

　　2.2 系統的(de)工作過程(cheng)分析

　　充電器系(xi)統的控制(zhi)框(kuang)圖(tu)如圖(tu)4 所示(shi)。

　　由(you)(you)圖4 可以看(kan)出， 在蓄電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)階(jie)段， 控(kong)制回路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)環(huan)僅(jin)由(you)(you)太(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)構成(cheng)。此(ci)時(shi)， 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)環(huan)的輸(shu)(shu)出為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)環(huan)的給定(ding)(ding)(ding)(ding)，通(tong)過檢(jian)測(ce)主電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路中蓄電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)與給定(ding)(ding)(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相(xiang)比較來改變(bian)SG3525 的輸(shu)(shu)出脈(mo)沖寬度(du)， 使(shi)太(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)跟蹤給定(ding)(ding)(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。由(you)(you)圖1 可知， 當太(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)下降， 在穩態時(shi)， 太(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)等于給定(ding)(ding)(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)， 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)環(huan)的給定(ding)(ding)(ding)(ding)亦(yi)為穩定(ding)(ding)(ding)(ding)值， 蓄電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)等于給定(ding)(ding)(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)； 反之， 當太(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)小于給定(ding)(ding)(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)時(shi)，SG3525