直接开关电源的外文文献翻译.docx

1、直接开关电源的外文文献翻译DC switching power supply for protection technologyAbstract: The DC switching power supply protection system, protection system design principles put forward and the whole protective measures, analysis of the switching power supply of the various protection features and design, introduc

2、es several practical protection Circuit.Keywords: switching power supply; protection circuit ;System Design1 Introduction DC switching regulator for use in the more expensive high-power switching devices, the control circuit is also more complex, In addition, the load switching regulators are genera

3、lly level with a large number of highly integrated electronic systems installed on the device. Power transistors and integrated device tolerance, poor thermal shocks. Thus the protection switching regulator should take into account the regulator itself and load security. Many different types of circ

4、uit protection, polarity protection described here, program protection, over current protection, over voltage, under voltage protection and thermal protection circuits. Some protection is usually chosen to be combined to form a comprehensive protection system.2 polarity protection DC switching regul

5、ators are generally unregulated input DC power supply. Due to operation errors or unexpected circumstances will the wrong polarity will damage the switching power supply. Polarity protection purposes, is to make the switching regulator only when the correct polarity connected to the unregulated DC p

6、ower to work. Using a single device can be achieved through the wizard power polarity protection. Simple polarity protection circuit shown in Figure 1. To flow through the diode D switching regulators input total current, so this circuit is used in low power switching regulator on the more appropria

7、te. In the high power of the occasion, put the polarity protection circuit as a part of the protection program, can save the power required for polarity protection diode, power consumption will be reduced. For convenient operation, easy to identify the polarity is correct or not, the diode in Figure

8、 1, the received light. 3 program protectionSwitching power supply circuit is more complex, basically can be divided into low-power control section and power switch part. Switching transistors are high power, to protect the switching transistor is turned on or off the power when the security must le

9、t modulators, amplifiers and other small power control circuit. To this end, to ensure that the correct boot process. The input of switching regulator typically take a small inductance and large capacitance of the input filter. Moment in the boot, will flow through a large filter capacitor inrush cu

10、rrent, the inrush current can be several times the normal input current. Make such a large surge current ordinary power switch contacts or relay contact melting, and to enter the fuse blows. In addition, the inrush current can also damage the capacitor, so that shortened life expectancy, premature d

11、amage. To this end, the boot should be access to a limiting resistor, through the current limiting resistor to charge the capacitor. In order not to consume too much of the current limiting resistor power, which affects the normal operation of switching regulators, power-transient process in the end

12、, with a relay automatically pick it short so DC power directly to the switching regulator Power supply, shown in Figure 2. Such that the switching regulator circuit termed a soft startcircuit. Switching regulator control circuit logic components or op-amp auxiliary power supply required. To this en

13、d, the auxiliary power supply must be in the switch circuit. This control circuit can be used to ensure that the boot process. Normal boot process are: identification of the polarity of the input power, voltage protection boot auxiliary power supply circuit and through the current limiting resistor

14、R of the switching regulator input capacitor C charging modulation switching regulator circuit,short circuit limiting resistor switching regulator stability. In the switching regulator, the just-machine, because the output capacitor capacity, rated output voltage charge to take some time. During thi

15、s time, the sampling amplifier input low output voltage sampling, closed-loop regulation characteristics of the system will force the switching transistor conduction time longer, this way, the switching transistor during this period will tend to continuous conduction And easily damaged. To do this,

16、start this period of time required, the switching modulation circuit output to the switching transistor base drive signal pulse-width modulation, to ensure the switch transistor gradually become normal by the end of the switch state, and therefore should be protected to meet the additional power of

17、soft Start.4 over-current protectionWhen the load short-circuit, overload, or unforeseen circumstances such as the failure control circuits, will cause flow through the regulator in the switching transistor current is too large, the pipe increases power consumption, heat, if there is no over-current

18、 protection devices, power switching transistor There may be damaged. Therefore the switching regulator in the over-current protection is commonly used. The most economic and simple method is to fuse. Heat capacity of the transistor is small, generally can not play normal fuse protection, commonly u

19、sed is fast fuse. This approach has the advantage of protection is easy, however, need to switch transistor according to the specific requirements of the safety of the work area to select the fuse specifications. This disadvantage is over-current protection measures to bring the inconvenience of fre

20、quently replacing the fuse. Commonly used linear regulator current limit protection and current end protection switching regulator can apply. However, according to the characteristics of switching regulators, such protection can not directly control the output of the circuit switching transistor, so

21、 that over-current protection must be converted to a pulse output instruction to control the modulator to protect the switching transistor. In order to achieve over-current protection generally need to use sampling resistor in series in the circuit, this will affect the efficiency of power supply, s

22、o much for low power switching regulator of occasions. In the high-power switching power supply, taking into account power consumption, should try to avoid access to the sampling resistor. Therefore, over-current protection usually convert over, under voltage protection.5 over-voltage protection Swi

23、tching regulators input over-voltage protection, including over-voltage protection and output over-voltage protection. Switching regulator is not used by the regulated DC power supply such as batteries and rectifier if the voltage is too high, the switching regulator is not working properly, or even

24、 damage to the internal device, therefore, necessary to use the input over-voltage protection circuit. Formed by transistors and relays protection circuit shown in Figure 3. In this circuit, when the input DC power voltage is higher than the diode breakdown voltage regulator, the regulator of the br

25、eakdown, a current flows through the resistor R, V turns on the transistor, relay, normally closed contacts break Open, cut off the input. In which the value of steady pressure regulator tube Vz = ESrmax-UBE. Input power supply polarity protection circuit with the combination of the input over-volta

26、ge protection, polarity protection form identification and over-voltage protection circuit. Output over voltage protection in a switching power supply is crucial. Particular output is 5V, switching regulators, it loads a large number of highly integrated logic devices. If you work, the switching tra

27、nsistor switching regulator suddenly damage, the output potential to be immediately increased to the unregulated DC input voltage value, instantaneous cause great losses. Commonly used method is thyristor short circuit protection. Simple over-voltage protection circuit shown in Figure 4. When the ou

28、tput voltage is too high, the regulator is the breakdown, triggered thyristor, the output short-circuit, resulting in over-current, through the fuse or circuit protection device will enter the cut, protecting the load. This circuit is equivalent to the response time of the opening time of thyristor

29、is about 5 10s. The disadvantage is that operation voltage is fixed, the temperature coefficient, the action point of instability. In addition, the regulator there are discrete parameters, the same model but the over-voltage start value is different, makes it difficult to debug. Figure 5 is the impr

30、oved circuit. In which R1, R2 is a sampling circuit, Vz is the reference voltage. Esc sudden increase in the output voltage, the transistor V1, V2 conducting, thyristor conduction. Reference voltage Vz by the type To determine, UBE1 for the V1 of the emitter (BE) voltage drop. Operation voltage of t

31、he circuit variable, and the action point of fairly stable. When the regulator to 7V, its temperature coefficient of the emitter and the transistor V1 (BE) can offset voltage temperature coefficient, temperature coefficient can drop very low. But the output is 5 5.5V DC switching regulators, its usu

32、al operation voltage is 5.5 6V. Then the regulator will be in the 3.5V voltage below the voltage regulator near the temperature change coefficient is -20 -30mV / . Therefore, large temperature protection circuit will be the occasion malfunction. Used to detect the voltage comparator integrated circu

33、it switching regulator output voltage, is more commonly used methods, the use of the comparator output changes state match with the corresponding logic, constitute over-voltage protection circuit, this circuit is both sensitive and Stability. 6 under-voltage protection Output voltage below the specified value, refl