Chenhao Nan

A New Soft-Switching Topology for Switched Inductor High Gain Boost

This paper proposes a new high-gain soft-switching dc–dc topology based on a switched inductor boost converter (SIBC). A conventional SIBC as a high gain boost topology has the issues of high conduction loss in switching diodes and high switching loss in the main switches. Also, it has severe electromagnetic interference (EMI) issue due to high-frequency ringing formed by parasitic inductance and diode junction capacitors. The new topology is derived with the objective of achieving zero voltage switching (ZVS) turn on of the main switch. Instead of adding extra active clamp zero voltage transition (ZVT) path at the switching node, the proposed topology augments the auxiliary ZVT path to the switching diode path. This is achieved by replacing the switching diodes with synchronous switches. The new topology can achieve soft switching for all the switches and alleviate the EMI issue. All the diodes achieve zero current switching (ZCS) turn off without reverse recovery. Auxiliary switches have ZCS turn on and ZVS turn off, and the main switches have ZVS turn on. The soft-switching SIBC also reduces the conduction loss in the switching diodes. A numerical simulation in PLECS and a prototype hardware are built corresponding to a micro-inverter application with 100xa0kHz switching frequency. Peak power conversion efficiency of 94.76% is achieved in the hardware prototype with Si devices.

Coupled inductor implementation improves performance of output feedback ZVT in full bridge inverters

This paper proposes a topology based on output feedback zero-voltage-transition (ZVT) technique with coupled inductor to realize zero-voltage-switching (ZVS) for all the main switches of the full bridge inverters, and inherent zero-current-switching (ZCS) for the auxiliary switches. The advantages of the strategy include the provision to implement zero state modulation schemes such as unipolar or hybrid scheme in the full bridge inverters to decrease the THD significantly, naturally adaptive auxiliary inductor current and without the requirement of large balancing capacitors. The coupled inductor can decrease the core loss compared with the previously reported individual inductor method and can decrease the auxiliary current needed to realized ZVS of the main switches. The modulation scheme and the commutation process are analyzed in detail. Finally a 1 kW, 400 kHz switching frequency inverter of the proposed topology using SiC MOSFETs has been built to validate the theoretical analysis. The proposed ZVT with hybrid modulation technique is implemented in DSP TMS320F28335 resulting in full ZVS for the main switches. Compared with no ZVT case, the proposed method can improve the system CEC efficiency significantly from 95.58% to 97.29% and peak efficiency from 96.29% to 97.86%.

A high efficiency resonant switched-capacitor converter for data center

In this paper, a resonant switched-capacitor dc-dc converter is proposed for data center application. The proposed converter possesses features such as high efficiency, high power density and light-weight. Zero current switching (ZCS) can be achieved with the resonant operation, which allows the converter operating under high efficiency. Proper switching device selection and in-depth power loss analysis on different devices have been performed to support better design of the proposed converter. Simulation results are provided in this paper to validate operation principle of the proposed converter. A GaN based prototype with nominal 450W, 54V input and 9V output has been built to verify the theoretical analysis. The maximum power rating of the designed prototype is 600W. Power density of the prototype reaches 750W/in3. When the prototype operating at 253kHz, it achieves 98.55% peak efficiency.