【正文】 In order to easy to operate, make it easier to identify the correct polarity or not, collect the next light. C、 Procedures to protect Switching power supply circuit is rather plicated, basically can be divided into lowpower and highpower part of the control part of the switch. Switch is a highpower transistors, for the protection of the transistor switch is turned on or off power safety, we must first modulator, amplifier and other lowpower control circuit. To this end, the boot to ensure the correct procedures. Switching Regulators generally take the input of a small inductor, the 桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)英文資料 翻譯 1 input filter capacitor. Moment in the boot, filter capacitor will flow a lot of surge current, the surge current can be several 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. In addition, the capacitor surge current will damage to shorten the life span of premature damage. To this end, the boot should be access 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 relays it to DC power supply directly to the switching regulator power supply. This circuit switching regulator called a soft start circuit. Switching regulator control circuit of the logic ponents required or opamp auxiliary power supply. To this end, the auxiliary power supply must 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 → charge modulation switching regulator circuit, → short circuit current limiting resistor stability switching regulator. 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 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。s output voltage, the lower limit of the output is off, due to the voltage value of voltage protection. Overcurrent 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 appropriate. 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 plex machines, power supply parts and do not stand out in a place, it can give staff an effective warning of failure。由于操作失誤或者意外情況會(huì)將其極性接錯(cuò) ,將損壞開關(guān)穩(wěn)壓電源。開關(guān)晶體管則屬大功率，為保護(hù)開關(guān)晶體管在開啟或關(guān)斷電源時(shí)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。這種電路稱之謂開關(guān)穩(wěn)壓器的“軟啟動(dòng)”電路。