A Family of High Step-Up Cascade DC–DC Converters With Clamped Circuits

In this article, a novel passive lossless clamped circuit composed of two capacitors and one diode is proposed. One of the two capacitors is used to construct a flowing path for the energy of leakage inductor and the other is used to store the leakage energy. Compared with a classical passive lossless clamped circuit, the novel circuit structure is more flexible and versatile, and the number of the extra capacitor and diode is consistent to the classical circuit for recycling the energy. Moreover, an idea of using more capacitors in series instead of a single output capacitor to reduce voltage stress and volume is presented. In order to extend their application scope and demonstrate their practical value, the novel clamped circuits and the idea are integrated into a family of cascade dc–dc converters based on the popular boosting cell, such as voltage-lift cell, symmetric voltage multiplier cell and asymmetric voltage multiplier cell. As a representative, a novel cascade converter, which integrates the novel passive lossless clamped circuit and the idea is analyzed in detail. The proposed converter has a high voltage gain and low ripple input current. The voltage stresses of an output diode and output capacitor can be effectively reduced. Its output capacitor adopts a 20-uF polypropylene (CBB) capacitor rated at 250 V to replace the higher rated electrolytic capacitor. A prototype circuit in the laboratory is established to verify its performances.