High Step-down ZCS Buck Converter with Switched Capacitor

In order to extend the output voltage range of buck converter, a new topology of two-stage buck converter with switched capacitor is proposed in this paper. An input inductor is adopted in the first stage of the converter to suppress the current spikes caused by switched capacitor. At the same time, when the input inductance and the switching capacitance are less than or equal to the theoretical values, the first stage can realize zero current switching (ZCS).To achieve the ZCS of other switching devices, an auxiliary resonant circuit is added in the second stage of the converter, and it is necessary to ensure that the switching on time in advance of the auxiliary switch is within the theoretical range. This converter has the features of high step-down ratio, soft switching on/off, and low device stress. After the working principle and the characteristics of the converter are introduced in detail, the feasibility of the proposed topology is verified by simulation and experimental results.