Surge characteristics of resonant converters in start-up transient response

One of most serious difficulties of resonant converters is the current and voltage stress. There are two types of stress in the resonant converters. One is the stress due to the resonant phenomenon around the switch. This stress is inherent in the resonant converters, and therefore many interesting techniques, like soft switching techniques, have been developed to reduce it. The other is the surge stress in large-signal response, particularly in start-up transient response, and it has not been completely reported yet. This paper studies the surge characteristics of resonant converters in start-up transient response by analysis, simulation, and experiments. As a result, it clarified that the surge current occurs in ZVS (zero voltage switching) resonant converters and the surge voltage occurs in ZCS (zero current switching) resonant converters, which have not been studied before