A Simple Open-loop Soft Startup Method Based on Operation Mode Analysis for LCC Converters Used in High-voltage DC Power Supply

LCC converters incorporate the stray parameters of high frequency transformer and are commonly employed as the initial stage of high-voltage DC power supplies, enhancing both efficiency and power density. However, the significant overshoot that occurs during the startup phase of high-voltage DC power supply poses considerable difficulties for the circuit. In this article, a simple open-loop soft startup control method is proposed: First, the operation mode analysis method is used to accurately solve the time-domain model of the LCC converter under different duty cycles in continuous current mode (CCM). Second, an open-loop variable duty cycle soft startup control strategy from the energy transmitted view is derived. Finally, soft startup process corresponding to different startup time requirements are verified on a 200V/20kV experimental prototype.