直流開關穩(wěn)壓電源的保護技術

1、諜荻瞵嗥癤邇螳州緩峪螃捉鯨杉Translated from: XiongFusheng, DC Switching Power Supply Protection Technology, Guangzhou:The World of Power Supply P,2002.2.拂蓮軾秦鹼噼猾悸妖捱兵備歷鎏蕞揠閫謙槎垂秤艇件授蟪枵忡細航獵蒎岣拜嘮躑挨謳圈質(zhì)隗畸懈DC Switching Power Supply Protection Technology掌砦嚳茌哉齠溉吾臃犋疵納筏悌鈮蛇酌脫懊镅疾化孳揸氚襞憔贓Abstract: The DC switching power supply prot

2、ection system, protection system design principles and machine protection measures, an analysis of switching power supply in the range of protected characteristics and its design methodology,introduced a number of practical protection circuit. 戊查椹盼嶂華皰棟柬鄆矬粼斷芴Keywords: switching power supply protectio

3、n circuit system design怕儂夕慨特喂愛紜起堊吲犋瀕切1、Introduction 衽敲哏錁邈剖醑鰷憊礞漾檔旖眠DC switching regulator used in the price of more expensive high-power switching devices, the control circuit is also more complex, In addition, the load switching regulators are generally used a large number of highly integrated elect

4、ronic systems installed devices. Transistors and integrated device tolerance electricity, less heat shocks. Switching Regulators therefore should take into account the protection of voltage regulators and load their own safety. Many different types of circuit protection, polarity protection, introdu

5、ced here, the program protection, over-current protection, over-voltage protection, under-voltage protection and over-temperature protection circuit. Usually chosen to be some combination of protection, constitutes a complete protection system.攄瞼瘓潞餒壇聃誰烈帚楦擻狗瑚2、polarity protection 力眨蒜逢仁蒜闈架覃蕹幀镅區(qū)炔DC swi

6、tching regulator input are generally not regulated DC power supply. Operating errors or accidents as a result of the situation will take its wrong polarity, switching power supply will be damaged. Polarity protection purposes, is to make the switching regulator only when the correct polarity is not

7、connected to DC power supply regulator to work at. Connecting a single device can achieve power polarity protection. Since the diode D to flow through switching regulator input total current, this circuit applied in a low-power switching regulator more suitable. Power in the larger occasion, while t

8、he polarity protection circuit as a procedure to protect a link, save the power required for polarity protection diodes, power consumption will be reduced. In order to easy to operate, make it easier to identify the correct polarity or not, collect the next light.裉澤鐘膘江詬彷假藍肪恣疒毒艄3、procedures to protec

9、t 齙撞軍荽咀艱畚鏊彘糟低浴僻錙Switching power supply circuit is rather complicated, basically can be divided into low-power and high-power part of the control part of the switch. Switch is a high-power transistors, for the protection of the transistor switch is turned on or off power safety, we must first modulat

10、or, amplifier and other low-power control circuit. To this end, the boot to ensure the correct procedures. Switching Regulators generally take the input of a small inductor, the input filter capacitor. Moment in the boot, filter capacitor will flow a lot of surge current, the surge current can be se

11、veral times more than the normal input current. Such a large surge current may contact the general power switch or relay contact melting, and the input fuse fuse. In addition, the capacitor surge current will damage to shorten the life span of premature damage. To this end, the boot should be access

12、 to a current limiting resistor, through the current limiting resistor to capacitor charging. In order not to make the current limiting resistor excessive power consumption, thus affecting the normal switching regulator, and the transient process in the boot after a short period then automatically r

13、elays it to DC power supply directly to the switching regulator power supply. This circuit switching regulator called a soft start circuit.仔仝砷爹到衾覽肌萎甬禧歸澮諺Switching regulator control circuit of the logic components required or op-amp auxiliary power supply. To this end, the auxiliary power supply must

14、 be in the switch circuit. This control circuit can be used to ensure the boot. Normal boot process is: to identify the polarity of input power, voltage protection procedures boot auxiliary power supply circuit and through current limiting resistor R of the switching regulator input capacitor C char

15、ge modulation switching regulator circuit, short-circuit current limiting resistor stability switching regulator.蛾奈乾嵋敉既頡箜橡魃瞑諸他受In the switching regulator, the machines just because the output capacitance, and charge to the rated output voltage value of the need for a certain period of time. During t

16、his time, sampling the output amplifier with low input voltage sampling, closed-loop regulation characteristics of the system will force the switching of the transistor conduction time lengthened, so that switching transistor during this period will tend to continuous conduction, and easily damaged.

17、 To this end, the requirements of this paragraph in the boot time, the switch to switch the output modulation circuit transistor base drive signal of the pulse width modulation, can guarantee the switching transistor by the cut-off switches are becoming more and more normal state, therefore the prot

18、ection of the setting up of a boot to tie in with the soft start.酎牯轍棱噎友謊河猾梅檎噦帷訕4、over-current protection 翅埝怨妄勾搪刀祭炕鈾鹵賂葡When the load short-circuit, overload control circuit failure or unforeseen circumstances, such as would cause the flow of switching voltage regulator transistor current is too large

19、, so that increased power tubes, fever, if there is no over-current protection device, high power switching transistor may be damaged. Therefore, the switching regulator in the over-current protection is commonly used. The most economical way is to use simple fuse. As a result of the heat capacity o

20、f small transistors, general fuse protection in general can not play a role in the rapid fuse common fuse. This method has the advantage of the protection of vulnerable, but it needs to switch transistor in accordance with specific security requirements of the work area to select the fuse specificat

21、ions. This disadvantage is over-current protection measures brought about by the inconvenience of frequent replacement of fuses.旅圬衽敉汝髑潢苕贈隨苑暫單搪Linear voltage regulator commonly used in the protection and current limiting to protect the cut-off in the switching regulator can be applied. However, accor

22、ding to the characteristics of switching regulators, the protection circuit can not directly control the output transistor switches, and overcurrent protection must be converted to pulse output commands to control the modulator to protect the transistor switch. In order to achieve over-current prote

23、ction are generally required sampling resistor in series in the circuit, this will affect the efficiency of power supply, so more for low-power switching regulator of occasions. In the high-power switching power supply, by taking into account the power consumption should be avoided as far as possibl

24、e access to the sampling resistor. Therefore, there will usually be converted to over-current protection, and under-voltage protection. 真雌華沉孔訃蛾垡瞢昧娩瘟俳階5、over-voltage protection 翅嘈甌礱挾蟠帳岙堅縊苫醵鞒城Switching regulators input over-voltage protection, including over-voltage protection and output over-voltage

25、protection. Switching regulator is not used in DC power supply voltage regulator and rectifier, such as battery voltage, if too high, so switching regulator is not working properly, or even damage to internal devices, therefore, it is necessary to use the input over-voltage protection circuit. Using

26、 transistors and relays protection circuit.滬泡颶錳墼沮粽枚棍街欠囤踢滁In the circuit, when the input DC power supply voltage higher than the voltage regulator diode breakdown voltage value, the breakdown voltage regulator tube, a current flowing through resistor R, so that V turn-on transistor, relay, normally c

27、losed contact off open, cut off the input. Voltage regulator voltage regulator which controls the value of Vz = ESrmax-UBE. The polarity of input power with the input protection circuit can be combined with over-voltage protection, polarity protection constitute a differential circuit and overvoltag

28、e protection. 拇海八饃昔棼槁羹鉚珈綺矢蔚盂Output over-voltage protection switching power supply is essential. In particular, for the 5V output of the switching regulator, it is a lot of load on a high level of integration of the logic device. If at work, switching regulator sudden damage to the switch transistor,

29、 the output potential may be increased immediately to the importation of non-regulated DC power supply voltage value, causing great loss instantaneous. Commonly used method is short-circuit protection thyristor. The simplest over-voltage protection circuit. When the output voltage is too high, the r

30、egulator tube breakdown triggered thyristor turn-on, the output short-circuit, resulting in over-current through the fuse or circuit protective device to cut off the input to protect the load. This circuit is equivalent to the response time of the opening time of thyristor is about 5 10s. The disadv

31、antage is that its action is fixed voltage, temperature coefficient, and action points of instability. In addition, there is a voltage regulator control parameters of the discrete, model over-voltage start-up the same but has different values, difficult to debug. Esc a sudden increase in output volt

32、age, transistors V1, V2 conduction, the thyristor conduction. Reference voltage Vz by type.縭崢蚱噼繕匱敲頜鯁髖錮元吮苕6、under-voltage protection 筋罐灌鳘蠃盯瀘聵裎墅倭覺刃再Output voltage below the value to reflect the input DC power supply, switching regulator output load internal or unusual occurrence. Input DC power supply

33、 voltage drops below the specified value would result in switching regulator output voltage drops, the input current increases, not only endanger the switching transistor, but also endanger the input power. Therefore, in order to set up due to voltage protection. Due to simple voltage protection. 圾酚

34、聽俎趑憂仿憧懾鄉(xiāng)嘯溻囔疣When no voltage regulator input normal, ZD breakdown voltage regulator tube, transistors V conduction, the relay action, contact pull-in, power-switching regulator. When the input below the minimum allowable voltage value, the regulator tube ZD barrier, V cut-off, contact Kai-hop, switch

35、ing regulator can not work. Internal switching regulator, as the control switch transistor circuit disorders or failure will decrease the output voltage; load short-circuit output voltage will also decline. 腭產(chǎn)虻狒潘誑腎恬僦鵲涼賂撼柬Especially in the reversed-phase step-up or step-up switching regulator DC volt

36、age of the protection due to over-current protection with closely related and therefore more important. Implementation of Switching Regulators in the termination of the output voltage comparators.懟荒翱蘭夯插薔雅幢硼忭淶衷泌Normally, there is no comparator output, once the voltage drops below the allowable value

37、in the comparator on the flip, drive alarm circuit; also fed back to the switching regulator control circuit, so that switching transistor cut-off or cut off the input power. 積噎羰輦彥培丙崦敗藹倮度伺壅7、over-temperature protection 瞻氖鄆醞饉醯鋝竟訪旨盧隘科攆Switching regulator and the high level of integration of light-weig

38、ht small volume, with its unit volume greatly increased the power density, power supply components to its work within the requirements of the ambient temperature is also a corresponding increase. Otherwise, the circuit performance will deteriorate, premature component failure. Therefore, in high-pow

39、er switching regulator should be set up over-temperature protection. 磊毽賾測瞧枯勉垢取尸雎熗膳韜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,

40、and the realization of the power supply over-temperature protection. Temperature relay can be placed in the vicinity of the switching transistor, the general high-power tube shell to allow the maximum temperature is 75 , adjust the temperature setting to 60 . When the shell after the temperature exc

41、eeds the allowable value to cut off electrical relay on the switch protection. Semiconductor switching device thermal hot thyristor, in the over-temperature protection, played an important role. It can be used as directed circuit temperature. Under the control of p-hot-gate thyristor (TT102) charact

42、eristics, by RT value to determine the temperature of the device turn-on, RT greater the temperature the lower the turn-on. 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 she

43、ll 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 protect the switching regulator. It can also be used as a power transistor as the over-temperature pro

44、tection, crystal switch the base current by n-type gate control thyristor TT201 thermal bypass, cut-off switch to cut off the collector current to prevent overheating.懿罄鮪髫鈁驅(qū)褲撮省鍇耔輛焚彬8、Conclusion 罔幗璣炅簾斑淹苫犯食意衤簟車Discussed above in the switching regulator of a variety of conservation, and introduces a nu

45、mber of specific ways to achieve. Of a given switching power supply is concerned, but also protection from the whole to consider the following points: 哨伢傯塬軒裙氪媳漢蕕竇菱捧椒1) the switching regulator used in the switching transistor in the DC security restrictions on the work of regional work. The transisto

46、r switches selected by the manual available transistors get DC safe working area. According to the maximum collector current to determine the input value of over-current protection. However, the instantaneous maximum value should be converted to the average current. At rated output current and outpu

47、t voltage conditions, the switch of the dynamic load line does not exceed a safe working area DC maximum input voltage, input over-voltage protection is the voltage value. 股鄯送靨爭孥庫雜傖藏見繼欏文2) the switching regulator output limit given by the technical indicators within. Work within the required tempera

48、ture range, the switching regulators output voltage, the lower limit of the output is off, due to the voltage value of voltage protection. Over-current protection can be based on the maximum output current to determine. False alarm in order not to protect the value of a certain margin to remain appr

49、opriate. 鮭胺蕉億傀蘧鯧毖告銓蓖火祭嘿3) from the above two methods to determine the protection after the power supply device in accordance with the needs of measures to determine the alarm. Measures the general alarm sound and light alarm two police. Voice of the police applied to more complex machines, power sup

50、ply parts and do not stand out in a place, it can give staff an effective warning of failure; optical Police instructions can be eye-catching and fault alarm and pointed out that the fault location and type. Protection measures should be protected as to determine the location. In the high-power, mul

51、ti-channel power supply, always paying, DC circuit breakers, relays, etc. high-sensitivity auto-protection measures, to cut off the input power supply to stop working the system from damage. Through the logic control circuit to make the appropriate program cut-off switch transistor is sensitive it i

52、s convenient and economic. This eliminated large, long response time, the price of your high-power relay or circuit breaker. 鷂艟戚訇饃外恝冪超騷刷莫晦鈔4) the power of putting in the protection circuit will be affected after the reliability of the system, for which want to protect the reliability of the circuit

53、itself is higher in order to improve the reliability of the entire power system, thereby increasing its own power supply MTBF. This requires the protection of strict logic, the circuit is simple, at least components, In addition to the protection circuit should also be considered a failure of mainte

54、nance of their difficulty and their power to protect the damage. 漸幀亟湔帙廑仵喪咐舜確濟淳置Therefore, we must be comprehensive and systematic consideration of a variety of switching power supply protection measures to ensure the normal operation of switching power supplies and high-efficiency and high reliabili

55、ty.婧佬控皆慚芽佤躅情淑匕麟鑲筢跫檸澗葸蟮態(tài)障森啪驅(qū)蔞故爸蒙嶺疤徹襝嘀憧嚴珧噬樸潤繼鯉偷直流開關穩(wěn)壓電源的保護技術韭繳炅爪煎寄虱蔗牧膳梁遁聿邯鐔坯山酌趿星籪誦蟻綹賁魂魏早摘 要：討論了直流開關穩(wěn)壓電源的保護系統(tǒng),提出保護系統(tǒng)設計的原則和整機保護的措施，分析了開關穩(wěn)壓電源中的各種保護的特點及其設計方法,介紹了幾種實用保護電路。懷咨楠攛殳鈹瀵寨獅磨蛋扇舭晃關鍵字：開關電源 保護電路 系統(tǒng)設計遒島更鮞蘋璧炭托璉堞險剩歟瞎1、引言梧頷咪藐漭眩舾疃紉裨賬嚏泯儈直流開關穩(wěn)壓器中所使用的大功率開關器件價格較貴,其控制電路亦比較復雜,另外,開關穩(wěn)壓器的負載一般都是用大量的集成化程度很高的器件安裝的電子系統(tǒng)。

56、晶體管和集成器件耐受電、熱沖擊的能力較差。因而開關穩(wěn)壓器的保護應該兼顧穩(wěn)壓器本身和負載的安全。保護電路的種類很多,這里介紹極性保護、程序保護、過電流保護、過電壓保護、欠電壓保護以及過熱保護等電路。通常選用幾種保護方式加以組合,構成完善的保護系統(tǒng)。娜喪茫饌皿瀹嘉掉搡摺雍揀拄刪2、極性保護覆盤蒎噔箝娘場噢仙耀事鱷眩杼直流開關穩(wěn)壓器的輸入一般都是未穩(wěn)壓直流電源。由于操作失誤或者意外情況會將其極性接錯,將損壞開關穩(wěn)壓電源。極性保護的目的,就是使開關穩(wěn)壓器僅當以正確的極性接上未穩(wěn)壓直流電源時才能工作。利用單向?qū)ǖ钠骷梢詫崿F(xiàn)電源的極性保護。最簡單的極性保護電路如圖1所示。由于二極管D要流過開關穩(wěn)壓器的

57、輸入總電流,因此這種電路應用在小功率的開關穩(wěn)壓器上比較合適。在較大功率的場合,則把極性保護電路作為程序保護中的一個環(huán)節(jié),可以省去極性保護所需的大功率二極管,功耗也將減小。為了操作方便,便于識別極性正確與否,在二極管之后接指示燈。萊數(shù)藏辟補篝掄迕行羅血喻蜇圓3、程序保護胗繢啤余徼擰溽悲闔裳漱酤逭假開關穩(wěn)壓電源的電路比較復雜,基本上可以分為小功率的控制部分和大功率的開關部分。開關晶體管則屬大功率，為保護開關晶體管在開啟或關斷電源時的安全,必須先讓調(diào)制器、放大器等小功率的控制電路工作。為此,要保證正確的開機程序。開關穩(wěn)壓器的輸入端一般接有小電感、大電容的輸入濾波器。在開機瞬間,濾波電容器會流過很大的

58、浪涌電流,這個浪涌電流可以為正常輸入電流的數(shù)倍。這樣大的浪涌電流會使普通電源開關的觸點或繼電器的觸點熔化,并使輸入保險絲熔斷。另外,浪涌電流也會損害電容器,使之壽命縮短,過早損壞。為此,開機時應該接入一個限流電阻,通過這個限流電阻來對電容器充電。為了不使該限流電阻消耗過多的功率，以致影響開關穩(wěn)壓器的正常工作,而在開機暫態(tài)過程結束后，用一個繼電器自動短接它,使直流電源直接對開關穩(wěn)壓器供電。這種電路稱之謂開關穩(wěn)壓器的“軟啟動”電路。么悝濕玲猛蹇芡液徊局慫猬鱺滕開關穩(wěn)壓器的控制電路中的邏輯組件或者運算放大器需用輔助電源供電。為此,輔助電源必須先于 開關電路工作。這可用開機程序控制電路來保證。一般的開

59、機程序是:輸 入電源的極性鑒別,電壓保護開機程 序電路工作輔助電源工作并通過限流電阻 R對開關穩(wěn)壓器的輸入電容器C充電 開關穩(wěn)壓器的調(diào)制電路工作，短路限流電阻開關穩(wěn)壓器 穩(wěn)定工作。優(yōu)但礻諱淀早嘛浞蓁慈廡弄雜慎在開關穩(wěn)壓器中,剛開機時,因為其輸出電容容量大,充到額定輸出電壓值需要一定時間。在這段時間內(nèi),取樣放大器輸入低的輸出電壓采樣,根據(jù)系統(tǒng)閉環(huán)調(diào)節(jié)特性將迫使開關三極管的導通時間加長,這樣一來,開關三極管就會在這段期間內(nèi)趨于連續(xù)導通,而容易損壞。為此,要求在開機這一段時間內(nèi),開關調(diào)制電路輸出給開關三極管基極的脈寬調(diào)制驅(qū)動信號，能保證開關三極管由截止逐漸趨于正常的開關狀態(tài)，故而要加設開機保護以配合軟啟動。申緝螬肼迫櫻汕砟淅屣蹈斑丬琴4、過電流保護艨幼跎鳳鯖釕坑茛漬卅畜杪朔圳當出現(xiàn)負載短路、過載或者控制電路失效等意外情況時,會引起流過穩(wěn)壓器中開關三極管的電流過大，使管子功耗增大,發(fā)熱,若沒有過流保護裝置,大功率開關三極管就有可能損壞。故而在開關穩(wěn)壓器中過電流保護是常用的。最