Jun. 17, 2022
Ceramic capacitors are widely used in military electronic equipment, system communication equipment, industrial control equipment, automotive electronics, consumer electronic products, etc. field.
The low internal resistance of ceramic capacitors is very helpful for low output ripple and can suppress high-frequency noise, but the capacitance of ceramic capacitors attenuates at high voltage. Why?
The capacitance decay of ceramic capacitors at high voltage is related to the properties of the materials used in ceramic capacitors.
All capacitors are made of two conductors, which are insulated from each other. When a voltage is applied between the two conductors, an electric field is formed between the two conductors. Under the action of the electric field, the dielectric charges between the conductors will gather in the direction of the two conductors. The electric field formed by them is opposite to the original electric field, and the electric field inside the dielectric becomes weaker. The ratio of the original applied electric field to the strength of the electric field in the dielectric is the relative permittivity of the dielectric.
The material used in the ceramic capacitor is a ceramic with a high dielectric constant, the main component is barium titanate, the relative dielectric constant is about 5000, and the dielectric constant is relatively high.
Since the dielectric can reduce the strength of the electric field, it is not easy to be broken down, so the ability of the capacitor to store electric charge can be improved, that is, the capacitance is improved. However, under high voltage, the electric field strength in the dielectric will continue to increase, and the dielectric constant will gradually decrease, which is why the capacitance of ceramic capacitors decays under high voltage.
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