The role and selection of thermistor in the switching power supply.Human Body Temperature Monitoring Sensor

　　The NTC thermistor is small and the power is large and the power is large. The main function of the power supply circuit is to inhibit the surging current. Generally, it is connected in series on the input of the city. It has a rated zero -power resistance value. When connected in the power loop, it can effectively suppress the booting wave current, and the power consumed can almost ignore it.

　　At normal temperature, NTC thermistor has high resistance, namely nominal zero power resistance values. In terms of traditional fixed resistance value limit resistance, this means that the power consumption on the resistance has decreased by dozens to hundreds of times due to the decline in resistance. Switch power product. After power off, the NTC thermistor is cooled, and the resistance value will gradually return to the nominal zero -power resistance value. The recovery time will take tens of seconds to a few minutes. When the next start is started, the cycle is circulated in the above process.

　　When the switching power supply cannot be changed when the capacitor voltage cannot be changed, a large charging current will be generated. This current is the input wave current we often say, which is generated when the filter capacitor is initially charged. Although this wave current is very short, if it is not suppressed, it will reduce the life of the input capacitance and the rectifier bridge, and it may also reduce the voltage of the input power supply. The normal work of the equipment is interfered.

　　The selection of NTCI thermistor should consider the following points:

　　Maximum rated voltage and filter electricity value

　　The maximum startup current value and long -term loading on NTC thermist resistance of NTC heat -sensitive resistance

　　The working environment of NTC thermal resistance

　　Product quality and safety

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