Unlike existing single-stage AC/DC converters with uncontrolled intermediate bus voltage, a new single-stage AC/DC converter achieving power factor correction (PFC), intermediate bus voltage output regulation, and output voltage regulation is proposed. The converter is formed by integrating a boost PFC converter with a two-switch clamped flyback converter into a single power stage circuit. The current stress of the main power switch is reduced due to separated conduction period of the two source currents flowing through the power switch. A dual-loop current mode controller is proposed to achieve PFC, and ensure independent bus voltage and output voltage regulations. Experimental results on a 24-V/100-W hardware prototype are given to confirm the theoretical analysis and performance of the proposed converter.

A Single-Stage AC/DC Converter With High Power Factor, Regulated Bus Voltage, and Output Voltage

Unlike existing single-stage AC/DC converters with uncontrolled intermediate bus voltage, a new single-stage AC/DC converter achieving power factor correction (PFC), intermediate bus voltage output regulation, and output voltage regulation is proposed. The single-power-stage circuit is formed by integrating a boost PFC converter with a two-switch-clamped forward converter. The current stress of the main power switches is reduced due to separated conduction period of the two source currents flowing through the power switch. A dual-loop peak-current-mode controller is proposed to achieve PFC and ensure independent bus voltage and output voltage regulations. Experimental results on a 24-V/100-W hardware prototype are given to confirm the theoretical analysis and performance of the proposed converter. The converter has conversion efficiency ranging from 86% to 92% at full-load condition.

Single-Stage AC/DC Boost–Forward Converter With High Power Factor and Regulated Bus and Output Voltages

A new low-power single-stage ac-dc converter is proposed in the paper. The outstanding feature of the converter is that it can operate with a sinusoidal input current and a low primary-side dc bus voltage that is much less variable than that found in other single-stage converters. The operation of the converter is discussed in the paper and its various modes of operation are explained in detail. An analysis of the converter's steady-state characteristics is performed and the results are used in the design of the converter. Experimental results obtained from a prototype converter are also presented.

A Low-Power AC–DC Single-Stage Converter With Reduced DC Bus Voltage Variation

In a voltage source inverter, overmodulation is required to extend the range of operation and enhance the dc-link voltage utilization. A carrier-based implementation of a modulation strategy for the three-level neutral-point-clamped inverter is proposed for the overmodulation region. The modulation strategy ensures zero average neutral-point current in a switching period. A newly proposed boundary compression is used to regulate the dc-link voltage at all operating points. A description of the algorithm to implement the modulation strategy is also presented. The main advantage of the proposed algorithm is its simplicity. The reference signals for the PWM can be calculated using maximum six steps and does not require knowledge of the reference vector angle. The modulation strategy has been implemented in a three-level neutral-point-clamped inverter, and experimental results are presented.

A carrier-based approach for overmodulation of three-level neutral-point-clamped inverter with zero neutral-point current

A flyback-based single-stage power factor correction scheme with time-multiplexing control is proposed. Main and auxiliary switches operate independently within a same time cycle. High power factor and low output line-frequency voltage ripple are both obtained in discontinuous conduction mode. The major output power is directly delivered to the load. A single transformer is used for the power conversion. The main and auxiliary outputs are fully isolated. The experimental results confirm the effectiveness of the proposed scheme with high power factor and tight output regulation.

Yoshiyuki Ishihara

Papers

High Efficiency Single Stage AC-DC Converter by Hybrid Parallel Structure