High-Efficiency Digital-Controlled Interleaved Power Converter for High-Power PEM Fuel-Cell Applications

Abstract

A high-efficiency digital-controlled interleaved dc-dc converter is designed and implemented to provide a regulated high voltage output for high-power proton-exchange-membrane fuel-cell applications. Ripple cancellation on input current and output voltage can be achieved by the studied interleaved dc-dc power conversion technique to reduce hysteresis energy losses inside the fuel-cell stacks and meet battery charging considerations on the high-voltage dc bus. An active-clamped circuit is also used to reduce the voltage spike on the power switches for raising the system reliability. The operation principles and the design considerations of the studied power converter are analyzed and discussed in detail. Finally, a 10-kW laboratory prototype is built and tested. The experimental results are shown to verify the feasibility of the proposed scheme.

High-Efficiency DC–DC Converter With Fast Dynamic Response for Low-Voltage Photovoltaic Sources

Abstract

This paper proposes a high-efficiency dc-dc converter with fast dynamic response for low-voltage photovoltaic (PV) sources. The voltage stress of power switches is reduced at low-voltage side. Zero-current turn-off of output diodes is achieved at high-voltage side. Power efficiency is improved by reducing switching power losses. A modified proportional and integral controller is also suggested to achieve fast output voltage control. The dynamic response of the proposed converter is improved. The performance of the proposed converter is verified based on an experimental prototype for a 200-W PV module.

Analysis and Design of a Push–Pull Quasi-Resonant Boost Power Factor Corrector

Abstract

This paper proposes a novel power-factor corrector (PFC), which is mainly composed of two-phase transition-mode (TM) boost-type power-factor correctors (PFCs) and a coupled inductor. By integrating two boost inductors into one magnetic core, not only the circuit volume is reduced, but also the operating frequency of the core is double of the switching frequency. Comparing with single-phase TM boost PFC, both the input and output current ripples of the proposed PFC can be reduced if the equivalent inductance of the coupled inductor equals the inductance of single-phase TM boost PFC. Therefore, both the power-factor value and the power density are increased. The proposed topology is capable of sharing the input current and output current equally. A cut-in-half duty cycle can reduce the conduction losses of the switches and both the turns and diameters of the inductor windings. The advantages of a TM boost PFC, such as quasi-resonant (QR) valley switching on the switch and zero-current switching (ZCS) of the output diode, are maintained to improve the overall conversion efficiency. Detailed analysis and design procedures of the proposed topology are given. Simulations and experiments are conducted on a prototype with a universal line voltage, a 380-V output dc voltage and a 200-W output power to verify its feasibility.

A Modified High-Efficiency LLC Converter With Two Transformers for Wide Input-Voltage Range Applications

Abstract

This paper proposed a modified LLC converter with two transformers in series, which has four operation configurations, covering the range of four times the minimum input voltage. To optimize the proposed LLC converter in an attempt to achieve good efficiency, a numerical method is developed based on the LLC converter's steady-state equations. In order to minimize the magnetizing current and thus minimize the conduction and core losses, an optimal objective is proposed to find the maximum magnetizing inductance. An optimization procedure and a design example are given. A 250-W 210-V output prototype with input voltage ranging from 25 to 100 V is built to verify the developed numerical model and optimal design method. The dc gain obtained from experimental data agrees pretty well with that from the developed numerical model. Two conventional LLC converters are designed using fundamental harmonic approximation and the proposed optimal design, respectively, to make comparison with the proposed LLC converter and validate the proposed optimal design. Experimental results show that the proposed converter with proposed optimal design can achieve the peak efficiency up to 98%, while maintaining a very wide input voltage range.

A High Step-Down Transformerless Single-Stage Single-Switch AC/DC Converter

Abstract

This paper presents a high step-down tranformerless single-stage single-switch ac/dc converter suitable for universal line applications (90-270 V_rms) . The topology integrates a buck-type power-factor correction (PFC) cell with a buck-boost dc/dc cell and part of the input power is coupled to the output directly after the first power processing. With this direct power transfer feature and sharing capacitor voltages, the converter is able to achieve efficient power conversion, high power factor, low voltage stress on intermediate bus (less than 130 V) and low output voltage without a high step-down transformer. The absence of transformer reduces the component counts and cost of the converter. Unlike most of the boost-type PFC cell, the main switch of the proposed converter only handles the peak inductor current of dc/dc cell rather than the superposition of both inductor currents. Detailed analysis and design procedures of the proposed circuit are given and verified by experimental results.