Thermistor in the charger

The charge thermistor is generally based on a PTC ceramic and is applied to a capacitor in a smooth power supply. When the charger has an unexpected failure or short circuit, it can control the current to a guaranteed range. Generally, ordinary resistors are often used to control current when charging capacitors, but this also has certain technical risks. The self-protecting charge thermistor is based on PTC (Positive Temperature Coefficient) ceramics and is used to smooth the capacitors in the power supply. When a short circuit occurs, they limit the current to a level, such as when the capacitor is shorted, if the capacitor is shorted or the relay fails, the resistor will continue to be exposed to high power levels.

When the capacitor is charged, it is usually necessary to connect a resistor in series to control the charging current to avoid generating a strong current peak that exceeds the allowable range. This is usually done using a fixed normal resistor or a negative temperature coefficient (NTC) thermistor. In most cases, a time or voltage controlled relay is used to short the current limiting component after charging.

The regulation of the charging current is very important for the rectifier and converter system, because the peak value of the generated inrush current, if not controlled, may trigger the fuse or subject the rectifier to a high current exceeding the allowable range. If there is no interference during operation, the combination of the above conventional resistor and relay is sufficient to control the charging current. However, disturbances that occur during or after charging can cause these thermistors to fail completely and cause malfunctions of other components of the system.