Different snubber circuit configurations

?? There are several ways to build a snubber circuit in a power device. Figure 1 shows four common configurations.

??Figure 1. Four most common snubber circuit configurations--(a) C-type snubber circuit, (b) RC-type snubber circuit, (c) discharge RCD-type snubber circuit, (d) non-discharge RCD-type snubber circuit .

?? The design of the C-type snubber circuit shown in Figure (a) is relatively simple, without resistance, and is most suitable for two-in-one modules, not suitable for circuits with discrete components. In the RC-type snubber circuit shown in Figure (b) with added resistance, the energy stored in the CSNB is dissipated via the RSNB during each switching transient. Adding resistors to the snubber circuit reduces the discharge current of the capacitor and protects the circuit from higher di/dt.

?? For higher power applications, further diodes can be added to create RCD-type snubber circuits as shown in Figures (c), (d), where the diodes are used to block the current in the network when the transistor is turned on. RCD type snubber circuit can be divided into two types - discharge type and non-discharge type. For a discharge RCD type snubber circuit, the inrush current flows through the diode, making CSNB absorption more effective than RC absorption. The non-discharged RCD type snubber circuit consumes only the energy of the surge voltage, which means that the energy consumption of the RSNB does not increase much at high switching frequencies.

??Factors to Consider When Choosing the Right Capacitor for a Snubber Circuit

?? Whether the snubber circuit is designed based on SiC, Si or GaN technology, a snubber capacitor (as shown in Figure 1) is required. However, because SiC has very different properties than Si or GaN and is often required for applications at high voltages and high currents, understanding how to select the most suitable capacitors is critical.

?? Snubber capacitors used in SiC circuits usually have a small capacitance value and need to be close to the switch to reduce parasitic inductance. Specifications to consider when selecting include: package size and type, dielectric, electrode type, voltage and capacitance ranges, and current capability. Since SiC parts also tend to generate heat, the snubber capacitor also needs to have heat resistance.