【文章內容簡介】 ower 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. Switching regulator39。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 Vz = ESrmaxUBE. The polarity of input power with the input protection circuit can be bined with overvoltage protection, polarity protection constitute a differential circuit and overvoltage 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 thyristor. The simplest overvoltage protection circuit. When the output voltage is too high, the regulator tube breakdown triggered thyristor 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 of thyristor 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 control parameters of the discrete, model overvoltage startup the same but has different values, difficult to debug. Esc a sudden increase in output voltage, transistors V1, V2 conduction, the thyristor conduction. Reference voltage Vz by type.Output voltage below the value to reflect the input DC power supply, switching regulator output load internal or unusual occurrence. Input DC power supply 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. When no voltage regulator input normal, ZD breakdown voltage regulator