What Is a Snubbing Capacitor?


Snubbers are one of many energy-absorbing circuits designed to protect devices from voltage spikes. These voltage spikes come from circuit inductance, the aspect of the circuit generating the voltage, caused by a semiconductor switch. A semiconductor is a material that can conduct electricity. The snubber stops voltage by creating a different path for the current to flow through.

RC Snubber Networks

  • The snubber moves energy from the switching transistor --- a semiconductor that switches electronic signals --- and releases energy in the resistor, a component providing electrical resistance, so the highest temperature of the semiconductor drops. The snubbing capacitor reduces ringing to limit the peak voltage in switching transistor or rectifying diode.

Series Resistor

  • The most often used snubber circuit is the capacitor and series resistor connected across a single switch. The snubber circuit has a resistor that is not inductive, such as a carbon composition resistor.

AC Capacitors

  • AC capacitors serve as dampening or snubbing capacitors. They are connected together in a series with a resistor. They dampen undesirable voltage spikes resulting from the carrier storage effect when switching power semiconductors.

Bridge Rectifiers

  • The bridge rectifier is a common part of the modern amplifier and helps make transformer design more efficient. It has a transformer that is not center-tapped --- which is when the engineer makes a connection to a halfway point along a transformer or inductor --- and has at least four diodes. Diodes are electronic components that only conduct electricity in one direction. Two diodes conduct and the other two are switched off at a specific time. Engineers typically use silicone rectifiers --- devices that convert alternating currents into direct currents --- with bridge rectifiers. If engineers use more than one diode in a series, the capacitor needs to be parallel to each one to make sure the voltage is shared equally between the diodes. These capacitors will act as snubbing capacitors that will suppress the voltage created by the switching diodes.

Resistor Capacitor Network

  • Resistor capacitor networks serve as snubbing capacitors. They provide noise suppression. Two types of discharges can cause damage to the switching contacts and create noise: arc discharges and glow discharges. Arc discharges occur at lower voltages and glow discharges come from gases igniting between contacts. The resistor capacitor networks can keep the voltage between the contacts below 300 V and keep the rate of voltage charge below one volt per millisiemens.

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