電器類畢業(yè)設(shè)計(jì)外文翻譯----開關(guān)穩(wěn)壓電源-其他專業(yè)-wenkub.com
2025-01-15 03:21 本頁面
【正文】 這就要求保護(hù)的邏輯嚴(yán)密 ,電路簡單、元器件最少，除此而外還要考慮到保護(hù)電路本身出故障時(shí)維修難度和其所保護(hù)的電源損壞程 度。在大功率 ,多路電源的場合 ,總是用交、直流斷路器 ,高靈敏繼電器等構(gòu)成自動(dòng)保護(hù)措施 ,切斷電源的輸入使系統(tǒng)停止工作 ,免受損害。一般告警措施有聲警和光警兩種。在所要求的工作溫度范圍內(nèi) ,開關(guān)穩(wěn)壓器的輸出電壓的上、下限就是輸出過、欠電壓保護(hù)的電壓值。根據(jù)集電極電流的最大值來確定輸入過電流的保護(hù)值。它亦可以用作功率晶體管的過熱保護(hù)，晶體開關(guān)管的基極電流被 n 控制柵型熱晶閘管TT201 旁路，開關(guān)管截止，切斷集電極電流 ,防止過熱。根據(jù) p型控制柵熱晶閘管 (TT102)的特性，由 RT 值確定該器件的導(dǎo)通溫度， RT越大，導(dǎo)通溫度越低。亦可將溫度繼電器置于開關(guān)三極管的附近，一般大功率管允許的最高管殼溫度是 75℃ ，調(diào)節(jié)溫度整定值為 60℃ 。 過熱保護(hù) 開關(guān)穩(wěn)壓器的高集成化和輕量小體積，使其單位體積內(nèi)的功率密度大大提高，電源裝置內(nèi)部的元器件對其工作環(huán)境溫度的要求也相應(yīng)提高。特別在升壓型或反相升壓型的直流開關(guān)穩(wěn)壓器中欠電壓的保護(hù)是跟過電流保護(hù)緊密相關(guān)的，因而更加重要。簡單的欠電壓保護(hù)如圖 6所示。另外，穩(wěn)壓管存在著參數(shù)的離散性，型號相同但過電壓起動(dòng)值卻各不相同，給調(diào)試帶來了困難。常用的方法是晶閘管短路保護(hù)。輸入 電源的極性保護(hù)電路可以跟輸入過電壓保護(hù)結(jié)合在一起 ,構(gòu)成極性 保護(hù)鑒別與過電壓保護(hù)電路。 9 過電壓保護(hù) 開關(guān)穩(wěn)壓器的過電壓保護(hù)包括輸入過電壓保護(hù)和輸出過電壓保護(hù)。但是 ,根據(jù)開關(guān)穩(wěn)壓器的特點(diǎn) ,這種保護(hù)電路的輸出不能直接控制開關(guān)三極管 ,而必須使過電流保護(hù)的輸出轉(zhuǎn)換為脈沖指令 ,去控制調(diào)制器以保護(hù)開關(guān)三極管。由于晶體管的熱容量小 ,普通保險(xiǎn)絲一般不能起到保護(hù)作用 ,常用的是快速熔斷保險(xiǎn)絲。為此 ,要求在開機(jī)這一段時(shí)間內(nèi) ,開關(guān)調(diào)制電路輸出給開關(guān)三極管基極的脈寬調(diào)制驅(qū)動(dòng)信號，能保證開關(guān)三極管由截止逐漸趨于正常的開關(guān)狀態(tài)，故而要加設(shè)開機(jī)保護(hù)以配合軟啟動(dòng)。這可用開機(jī)程序控制電路來保證。為了不使該限流電阻消耗過多的功率，以致影響開關(guān)穩(wěn)壓器的正常工作 ,而在開機(jī)暫態(tài)過程結(jié)束后，用一個(gè)繼電器自動(dòng)短接它 ,使直流電源直接 對開關(guān)穩(wěn)壓器供電。在開機(jī)瞬間 ,濾波電容器會(huì)流過很大的浪涌電流 ,這個(gè)浪涌電流可以為正常輸入電流的數(shù)倍。 程序保護(hù) 開關(guān)穩(wěn)壓電源的電路比較復(fù)雜 ,基本上可以分為小功率的控制部分和大功率的開關(guān)部分。最簡單的極性保護(hù)電路如圖 1 所示。 極性保護(hù) 直流開關(guān)穩(wěn)壓器的輸入一般都是未穩(wěn)壓直流電源。晶體管和集成器件耐受電、熱沖擊的能力較差。 also fed back to the switching regulator control circuit, so that switching transistor cutoff or cut off the input power. overtemperature protection Switching regulator and the high level of integration of lightweight small volume, with its unit volume greatly increased the power density, power supply ponents to its work within the requirements of the ambient temperature is also a corresponding increase. Otherwise, the circuit performance will deteriorate, premature ponent failure. Therefore, in highpower switching regulator should be set up overtemperature protection. Relays used to detect the temperature inside the power supply temperature, when the internally generated power supply overheating, the temperature of the relay on the action, so that whole circuit in a warning alarm, and the realization of the power supply overtemperature protection. Temperature relay can be placed in the vicinity of the switching transistor, the general highpower tube shell to allow the maximum temperature is 75 ℃ , adjust the temperature setting to 60 ℃ . When the shell after the temperature exceeds the allowable value to cut off electrical relay on the switch protection. Semiconductor switching device thermal hot thyristor, in the overtemperature protection, played an important role. It can be used as directed circuit temperature. Under the control of photgate thyristor (TT102) characteristics, by RT value to determine the temperature of the device turnon, RT greater the temperature the lower the turnon. When placed near the power switching transistor or power device, it will be able to play the role of temperature instructions. When the power control the temperature of the shell or the internal device temperature exceeds the allowed value, the heat conduction thyristor on, so that LED warning light. If the optocoupler with, would enable the whole circuit alarm action to protec t the switching regulator. It can also be used as a power transistor as the overtemperature protection, crystal switch the base current by ntype gate control thyristor TT201 thermal bypass, cutoff switch to cut off the collector current to prevent overheating. Conclusion 6 Discussed above in the switching regulator of a variety of conservation, and introduces a number of specific ways to achieve. Of a given switching power supply is concerned, but also protection from the whole to consider the following points: 1) the switching regulator used in the switching transistor in the DC security restrictions on the work of regional work. The transistor switches selected by the manual available transistors get DC safe working area. According to the maximum collector current to determine the input value of overcurrent protection. However, the instantaneous maximum value should be converted to the average current. At rated output current and output v
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