A Step-Variable Soft Start Control Method Applied to Boost Type PFC Rectifier

The widely used Boost type front-end Power factor correction (PFC) circuit for electric vehicle (EV) chargers has a common problem that, the bulky dc-bus capacitor will cause uncontrollable start-up surge current, which is a hidden trouble for system reliability. The reason for surge current is analyzed and a step-variable soft start control method is developed in this paper. A CPLD based phase shift control strategy with variable step size is designed. Experimental results show that this method is easy to be implemented, and the peak inrush current is restrained effectively while the start up speed can be accelerated simultaneously.