Apart from reducing the intermediate bus voltage, the con- verter in [19] employs resonant technique to further increase the step-down ratio based on a buck converter to eliminate the use of intermediate storage capacitor. The converter features with zero-current switching to reduce the switching loss. However, without the intermediate storage, the converter cannot provide hold-up time and presents substantial low-frequency ripples on its output voltage. Besides, the duty cycle of the converter for high-line input application is very narrow, i.e., < 10%. This greatly increases the difficulty in its implementation due to the minimum on-time of pulse-width-modulation (PWM) IC and rise/fall time of MOSFET. More details on comparing different approaches will be given in the Section V.