實(shí)驗(yàn)(3)開(kāi)關(guān)穩(wěn)壓電源制作實(shí)驗(yàn)報(bào)告

電源技術(shù)實(shí)訓(xùn)報(bào)告開(kāi)關(guān)穩(wěn)壓電源制作系別：機(jī)電工程系專業(yè)：應(yīng)用電子技術(shù)姓名：同組成員：學(xué)號(hào)：0906020122指導(dǎo)老師：2011年11月 目錄1、任務(wù)與要求·············································11.1、任務(wù)······················································11.2、要求······················································12、方案論證··············································1 2.1DC-DC主回路拓?fù)洹ぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁぁ? 2.2控制方法及實(shí)現(xiàn)方案·········································13.電路設(shè)計(jì)···············································2 3.1電路整體設(shè)計(jì)···············································2 3.2主回路器件的選擇··········································2 3.3控制電路設(shè)計(jì)···············································3 3.4效率的理論分析及算·········································3 3.5過(guò)流/過(guò)壓保護(hù)電路原理與設(shè)計(jì)································34．測(cè)試方法與數(shù)據(jù)········································44.1測(cè)試儀器···················································44.2測(cè)試方法···················································45．測(cè)試結(jié)果分析··········································55.1實(shí)驗(yàn)結(jié)果··················································55.2誤差分析···················································55.3改進(jìn)措施···················································56．電路圖原理圖及PCB圖··································67．參考文獻(xiàn)·············································78.元件清單············································71任務(wù)與要求1.1、任務(wù)設(shè)計(jì)并制作如圖1所示開(kāi)關(guān)穩(wěn)壓電源。圖1-1

電路框圖

1.2、要求 在電阻負(fù)載條件下，使電源滿足下述要求：基本要求(1)輸出電壓Uo可調(diào)范圍：30V-36V;(2)最大輸出電流Iomax：1A；(3)U2從18V變到21V時(shí)，計(jì)算電壓調(diào)整率：Su≤2%；(4)計(jì)算DC-DC變換器的效率n(5)具有過(guò)流保護(hù)功能,動(dòng)作電流Io(th)=1.3+0.2A;2、方案論證2.1DC-DC主回路拓?fù)鋱D2-1 主電路2.2控制方法及實(shí)現(xiàn)方案采用電壓型脈寬調(diào)制技術(shù)，產(chǎn)生頻率固定，脈沖寬度可調(diào)整的方波脈沖，采用電壓反饋環(huán)控制系統(tǒng)，它的反饋信息取自輸出電壓，用反饋電壓調(diào)整控制器的輸出脈沖寬度，改變脈沖占空比，實(shí)現(xiàn)開(kāi)關(guān)電源的穩(wěn)定。3.電路設(shè)計(jì)3.1電路整體設(shè)計(jì)通過(guò)TL494控制輸出脈寬控制IRF640的開(kāi)關(guān)頻率，使電感儲(chǔ)存電能的時(shí)間不同，從而控制輸出電壓的高低。 圖3-1 TL494管腳分布和內(nèi)部電路圖3.2主回路器件的選擇TL494、IRF640、FR157、600uH電感、220uF/50V電容3.3控制電路設(shè)計(jì)通過(guò)電阻R10、R11、R12分壓采樣反饋到TL494的1腳，然后與2腳的基準(zhǔn)電壓比較，從而改變3腳電位的高低，達(dá)到控制脈寬的寬窄。通過(guò)電阻R14的電壓采樣反饋到TL494的16腳，后與15腳電壓進(jìn)行比較，改變3腳電位的高低，即可控制脈寬的寬窄。3.4效率的理論分析及計(jì)算在U2=18V，輸出電壓UO=45V，輸出電流IO=2A的測(cè)試條件下。此電路的額定功率PO=90W，為了使此電路的效率達(dá)到%90以上則要求輸入功率為100W，允許損耗的功率為10W。 電路的損耗一般包括電感儲(chǔ)能損耗，整流二極管損耗，開(kāi)關(guān)管的損耗。 （1）儲(chǔ)能電感損耗，儲(chǔ)能電感損耗公式如下： PIND=PCO+PPE=I2rmsRe+△Bm 其大致功率為1.4w。 （2）肖特基二極管的損耗，當(dāng)二極管導(dǎo)通時(shí)流過(guò)二極管的電流等于電感電流，約為IO=3.86A，為降低損耗可以采用雙管并聯(lián)的方式，每只二極管的電流約為1.8A，對(duì)應(yīng)其UD=0.42V，二極管導(dǎo)通損耗PD=IOUD=1.8w（3）開(kāi)關(guān)管的損耗包括開(kāi)關(guān)損耗和導(dǎo)通損耗。開(kāi)關(guān)管的損耗直接與開(kāi)關(guān)頻率有關(guān)系，其功率損耗的計(jì)算公式為 P=I2RTonf+0.5×2∫50i2Rf。 取Ton=T/2,f=50kHz,則開(kāi)關(guān)管得損耗約為1.5W。經(jīng)計(jì)算，可得到電路的功率損耗約為4.7W，其效率可達(dá)到95.3%3.5過(guò)流/過(guò)壓保護(hù)電路原理與設(shè)計(jì)過(guò)流保護(hù)：如圖R14電阻對(duì)負(fù)載電流進(jìn)行取樣，返回至TL494的16腳，與15腳電壓進(jìn)行比較，當(dāng)16腳電壓超過(guò)15腳電壓時(shí)，使3腳電壓上升，從而降低輸出的占空比；過(guò)壓保護(hù)；如圖3與圖4，將可調(diào)電阻R14的2腳電壓接至LM339的正端，輸出端接至TL494的4腳，當(dāng)Uref電壓超過(guò)負(fù)端電壓時(shí)，輸出端為高電平，使TL494的4腳電壓為高電平，從而使TL494輸出占空比為0；圖3-2 過(guò)壓保護(hù)電路4、測(cè)試方法與數(shù)據(jù)4.1測(cè)試儀器數(shù)字萬(wàn)用表、電源4.2測(cè)試方法①電路板焊接完后，用萬(wàn)用表測(cè)試電路板是否有短路、斷路；②檢查無(wú)誤后，給電路板上電，電壓表打到DC200V檔，紅表筆接TL494的12腳，黑表筆接7腳，測(cè)得電壓是否為電源電壓，若不相等，先檢查下電路板；③用示波器測(cè)量TL494的5腳，測(cè)得為三角波；④用萬(wàn)用表測(cè)量TL494的4腳是否為低電平，若不是，則調(diào)整可調(diào)電阻R15，使4腳電壓為低電平；⑤調(diào)整可調(diào)電阻R6，使15腳電壓與16腳電壓進(jìn)行比較，從而改變輸出的占空比。5、測(cè)試結(jié)果分析5.1測(cè)試結(jié)果1) 電源端接18V電壓 2）實(shí)測(cè)時(shí)候5腳和6腳震蕩所產(chǎn)生的鋸齒波圖7-1 電路震蕩波形圖5.2誤差分析溫度變化時(shí)，電阻阻值會(huì)變化，計(jì)算結(jié)果會(huì)產(chǎn)生誤差。器件的選擇和儀器的選擇不可避免的產(chǎn)生一定的誤差。電路板受外界的電磁干擾也會(huì)影響電路的讀數(shù)。在PC