A High Step-Up Interleaved Current-Fed Resonant Converter for High-Voltage Applications

Abstract

A current-fed LLC resonant converter is proposed for high-voltage and high-power applications. Here, a two-phase interleaved structure is used in the input stage under the continuous conduction mode (CCM) to effectively reduce the input current and output voltage ripple values and the input filter and the output capacitors volumes. Due to the expandable structure and high voltage gain, the proposed configuration is suitable for high voltage applications since low voltage stresses are applied across its components. In fact, voltage stresses across the power semiconductors, i.e., MOSFETs and output diodes, along with the output capacitors, are almost one-third of the output voltage in the implemented three-stage configuration of the proposed converter. Here, the switching frequency is chosen close to, but less than, the converter series resonant frequency to reduce its different components' current stresses and perform softswitching operation for all power devices under wide input voltage and output power variations. Therefore, conduction and switching losses, and EMI noises are effectively reduced. Consequently, efficiency is improved and high-frequency operation is possible, which reduces the volume of passive components to achieve high-power density. The given topology is thoroughly analyzed mathematically. Also, a 1 kW prototype converter has been implemented to validate the given simulations and analyses. Here, wide input voltage (100 V-200 V) and output power (100 W-1000 W) variations are applied, and an asymmetric pulse width modulation (APWM) technique is used at 143 kHz switching frequency to regulate the output voltage at 1 kV. The obtained maximum efficiency value is 95.3%.INDEX TERMS Asymmetric pulse width modulation (APWM), current-fed converter, interleaved technique, LLC resonant converter, multi-winding transformer.

Application-Oriented Review of the LLC-Based Resonant Converters

“…To achieve high voltage gains, an interleaved Boost-LLC based resonant converter is proposed in [103,104]. This design incorporates series-connected capacitors at the output side to reduce voltage stresses when higher voltage values are desired.…”