57 Snubber Components
Because power FET devices are not subject to the same secondary breakdown mechanisms that occur with bipolar devices, from a reliability standpoint, it is often considered that snubber components are not essential. However, in most FET applications, a small RC snubber network will still be fitted across the FETs to reduce RF radiation and meet the dv/df limitations of the FET. (With very high dvldt, some power FETs display a failure mode resulting from conduction of the internal parasitic transistor.) However, it is true that the larger snubber components normally associated reducing secondary breakdown stress for bipolar transistors are not required with power FETs.
To reduce the length of the primary HF current path, a low-inductance capacitor should be fitted across the supply lines as close to the power switches and energy recovery diodes Dl and D2. This is particularly important in high-frequency converters.
Post a comment