【正文】 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 this time, sampling the output amplifier with low input voltage sampling, closedloop 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. 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 cutoff switches are being more and more normal state, therefore the protection of the setting up of a boot to tie in with the soft start. D、 Overcurrent protection When the load shortcircuit, overload control circuit failure or unforeseen circumstances, such as would cause the flow of switching voltage regulator transistor current is too large, so that increased power tubes, fever, if there is no overcurrent protection device, high power switching transistor may be damaged. Therefore, the switching regulator in the overcurrent protection is monly used. The most economical way is to use simple fuse. As a result of the heat capacity of small transistors, general fuse protection in general can not play a role in the rapid fuse mon fuse. This method has the advantage of the protection of vulnerable, 桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)英文資料 翻譯 2 but it needs to switch transistor in accordance with specific security requirements of the work area to select the fuse specifications. This disadvantage is overcurrent protection measures brought about by the inconvenience of frequent replacement of fuses. Linear voltage regulator monly used in the protection and current limiting to protect the cutoff in the switching regulator can be applied. However, according to the characteristics of switching regulators, the protection circuit can not directly control the output transistor switches, and over current protection must be converted to pulse output mands to control the modulator to protect the transistor switch. In order to achieve overcurrent protection are generally required sampling resistor in series in the circuit, this will affect the efficiency of power supply, so more for lowpower switching regulator of occasions. In the highpower switching power supply, by taking into account the power consumption should be avoided as far as possible access to the sampling resistor. Therefore, there will usually be converted to overcurrent protection, and undervoltage protection. E、 Overvoltage protection Switching regulator39。最簡(jiǎn)單的極性保護(hù)電路如圖 1 所示。這可用開機(jī)程序控制電路來(lái)保證。 五、過(guò)電壓保護(hù) 開關(guān)穩(wěn)壓器的過(guò)電壓保護(hù)包括輸入過(guò)電壓保護(hù)和輸出過(guò)電壓保護(hù)。簡(jiǎn)單的欠電壓保護(hù)如圖 6 所示。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。在計(jì)算機(jī)保護(hù)發(fā)展初期，曾設(shè)想過(guò)用一臺(tái)小型計(jì)算機(jī)作成繼電保護(hù)裝置。這就要求每個(gè)保護(hù)單元都能共 九、結(jié)語(yǔ) 以上分別討論了在開關(guān)穩(wěn)壓器中的各種保護(hù)方式 ,并介紹了一些具體實(shí)現(xiàn)的方法。通過(guò)邏輯控制 電路使相應(yīng)的開關(guān)三極管截止的方案顯得既靈敏方便又經(jīng)濟(jì)。聲警適用于整機(jī)比較復(fù)雜、電源部分又裝在不顯眼的地方 ,它可以給工作人員以有效的故障告警 。繼電保護(hù)的作用也只限于切除故障元件，縮小事故影響范圍。采用 32 位微機(jī)芯片并非只著眼于精度，因?yàn)榫仁?A/D 轉(zhuǎn)換器分辨率的限制，超過(guò) 16 位時(shí)在轉(zhuǎn)換速度和成本方面都是難以接受的；更重要的是 32 位微機(jī)芯片具有很高的集成度，很高的工作頻率和計(jì)算速度，很大的尋址空間，豐富的指令系統(tǒng)和較多的輸入輸出口。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℃。另外，穩(wěn)壓管存在著參數(shù)的離散性，型號(hào)相同但過(guò)電壓起動(dòng)值卻各不相同，給調(diào)試帶來(lái)了困難。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(guò)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。為了不使該限流電阻消耗過(guò)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(guò)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(duì)開關(guān)穩(wěn)壓器供電。 二、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。s input overvoltage protection, including overvoltage protection and output overvoltage 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 overvoltage protection circuit. Using transistors and relays protection circuit. 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 turnon transistor, relay, normally closed contact off open, cut off the input. Voltage regulator voltage regulator which controls the value of Vs. = EarwaxUBE. The polarity of input power with the input protection circuit can be bined with overvoltage protection, polarity protection constitute a differential circuit and over voltage protection. Output overvoltage 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, the output potential may be increased immediately to the importation of nonregulated DC power supply voltage value, causing great loss instantaneous. Commonly used method is shortcircuit protection thirsted. The simplest overvoltage protection circuit. When the output voltage is too high, the regulator tube breakdown triggered thirstier turnon, the output shortcircuit, resulting in overcurrent 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 桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)英文資料 翻譯 3 of thirstier is about 5 ~ 10μs. The disadvantage is that its action is fixed voltage, temperature coefficient, and action points of instability. In addition, there is a voltage regulator c