NTC thermistor for negative temperature coefficient thermistor, its feature is that as the temperature rises, the resistance value is nonlinear, is suitable for switching power supply, switching power supply, the USB power supply, all kinds of electric heaters, electronic energy-saving lamps, electronic ballast, the protection of various electronic equipment power supply circuit and color display tube, the filament of an incandescent lamps and other lighting protection. NTC thermistor if users do not pay attention to the use of it is easy to cause inrush current suppression failure, the following introduction to the use of NTC thermistor need to pay attention to two points:
1) Maximum rated voltage and filter capacitance
The size of the filter capacitor determines how large the NTC should be. For a certain size of NTC thermistor, there is a strict requirement on the size of the filter capacitor allowed to access, and this value is also related to the maximum voltage rating. In power supply applications, startup surges are caused by capacitor charging, so the ability of an NTC thermistor to withstand surges is usually evaluated by the capacity of the capacitor to be plugged at a given voltage value. In simple terms, the larger the input voltage, the smaller the maximum capacitor value allowed to access, and vice versa. Specifications for NTC thermistor products generally define the maximum capacitance allowed for access at 220Vac.
2) The maximum starting current allowed by the product and the working current loaded on the NTC thermistor for a long time
The resistance of an NTC thermistor is determined by the maximum allowable starting current of an electronic product. The current applied to the NTC thermistor shall not exceed the current specified in the specification when the product is in normal operation.
3)NTC thermistor working environment
The resistance of the thermistor is constantly changing with the temperature, so the temperature of the working environment of the NTC thermistor is a key point that cannot be ignored. NTC thermistor working environment because the NTC thermistor is greatly affected by the environmental temperature, generally in the product specifications only given at room temperature (25¡æ) resistance value, if the product application conditions are not at room temperature, or due to the design or structure of the product itself, resulting in NTC thermistor ambient temperature is not room temperature, You must calculate the resistance value of the NTC in the initial state before you can choose the above steps. In practical application, the ambient temperature of NTC thermistor should not exceed the upper/lower limits specified by the manufacturer.