Special resistors are a relatively rare type in our daily lives and are usually found in specific products. However, we also classify varistors and thermistors as special resistors. These two resistors are often seen on the power module, so what role do these two special resistors play in the power module? The power module circuit usually has AC-DC circuit design. The application of varistor and thermistor in this road is very important. Let's analyze the specific effects of these two resistors.


First, the role of the thermistor in the power module
A thermistor is a resistor designed for temperature. In a power module resistor, an NTC thermistor and a PTC thermistor are commonly used. The NTC thermistor has a negative temperature coefficient, that is, the higher the temperature, the smaller the impedance.
If the temperature coefficient of the PTC thermistor is used, that is, the higher the temperature, the greater the impedance. The use of impedance-to-temperature sensitivity plays an important role in the design of power module circuits.
 
Second, the role of varistor in the power module
In power modules, the use of varistors is often designed to protect critical electronic components, that is, to protect circuits. When the varistor is broken down, the resistance of the varistor is reduced to shunt the current, preventing the latter stage from being damaged or disturbed by excessive transient voltage. Circuit protection is the use of the non-linear characteristics of varistor. When an overvoltage occurs between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thus protecting the latter circuit.
   
The above two special resistors play a very important role in the power module, and many engineers use this design to design the power module. However, it is worth noting that these special resistors only build a layer of protection circuits on the periphery, but the safety of the entire circuit cannot rely on these two resistors, and more circuit safety design is needed.