What is a varistor?
The full name is "voltage-sensitive resistor", and the English name is "Voltage Dependent Resistor", abbreviated as "VDR". It is a special resistor whose resistance is not constant, but changes with the change of the voltage applied to its two ends. In other words, the resistance of the varistor is in a certain relationship with the applied voltage. This characteristic makes the varistor widely used in circuits.
How does a varistor work?
The basic principle of the varistor is to use the nonlinear characteristics of semiconductor materials. When the voltage is low, its resistance is large and it is in a high-resistance state; when the voltage reaches a certain value, the resistance drops rapidly and it is in a low-resistance state. This characteristic makes the varistor have important applications in overvoltage protection, lightning protection, power supply filtering, signal modulation and other fields.
This process is easy to understand: when the voltage across the varistor is lower than its threshold voltage, the current flowing through it is extremely small, which is equivalent to a resistor with infinite resistance. This means that when the voltage applied to it is lower than its threshold, it is equivalent to an open switch. When the voltage applied to a varistor is higher than its threshold voltage, the current flowing through it surges, equivalent to a resistor with infinitely small resistance. This means that when the voltage applied to it is higher than its threshold, it is equivalent to a closed switch.
Comments on “Basic knowledge of varistors: working principle, function, application and selection principle”