Optimum design of nondissipative snubbers by the evaluation of transistor's switching loss, surge voltage, and surge current

A nondissipative LC snubber has recently been used to suppress transistor's surge voltage and switching power loss in a switching power converter. Its suppression capability is improved with the increase in snubber capacitance, if the reactor current is assumed to be independent of the snubber. However, the increase in snubber capacitance yields the increase in reactor current. Both the surge and Switching loss increase with the reactor current. From these facts, there exists the limitation in suppressing the surge and switching loss. This paper clarifies the limitation of snubber effect quantitatively through the detailed analysis of the fundamental characteristics and the turnoff transient operation in a typical buck-boost converter.