Resonance Analysis and Soft-Switching Design of Isolated Boost Converter With Coupled Inductors for Vehicle Inverter Application

Abstract—
The comprehensive resonance analysis and soft-switching design of the isolated boost converter with coupled inductors are investigated in this paper. Due to the resonance participated by the voltage doubler capacitor, clamping capacitor, and leakage inductance of coupled inductors, the reverse-recovery problem of the secondary diodes is restrained within the whole operation range. By choosing appropriate magnetic inductance of the coupled inductors, zero-voltage switching ON of the main MOSFETs is obtained collectively at the same working conditions without any additional devices. Moreover, the range of duty ratio is enlarged to achieve soft switching and an optimal operation point is obtained with minimal input current ripple, when duty ratio approaches
0.5. Additionally, two kinds of resonances are analyzed and an op-timized resonance is utilized to achieve better power density. The prototype is implemented for the vehicle inverter requiring a 150 W output power, input voltage range varying from 10.8 to 16 V, and 360 V output voltage. Experiment results verify the design and show that the minimum efficiency is about 93.55% and 90.53% at low load and full load, respectively.

Optimal Design of DCM LCC Resonant Converter With Inductive Filter Based on Mode Boundary Map

Abstract—
LCC resonant converter with inductive filter operating in discontinuous current mode (DCM) can achieve zero-current switching (ZCS) for both the power switches and rectifier diodes. Therefore, it is suitable for high-power, low-voltage, high-current power supplies. The DCM LCC resonant converter with inductive filter might operate in different operating modes when input voltage or load changes, which challenges the design. This paper derives a mode boundary map, from which the operating mode of the converter can be easily determined. Based on the mode boundary map, a generalized optimal design procedure is proposed and a set of optimal and normalized converter parameters is determined, which can be easily converted into real parameters according to the converter specification. Three 5 kW prototypes with different converter parameters are fabricated and tested in the lab, and the experimental results show that with the set of optimal parameters, the converter can achieve the highest efficiency over the entire input voltage and load range.

Naturally Clamped Zero-Current Commutated Soft-Switching Current-Fed Push–Pull DC/DC Converter: Analysis, Design, and Experimental Results

Abstract—
The proposed converter has the following features:
1) zero-current commutation (ZCC) and natural voltage clamping (NVC) eliminate the need for active-clamp circuits or passive snub-bers required to absorb surge voltage in conventional current-fed topologies. 2) Switching losses are reduced significantly owing to zero-current switching of primary-side devices and zero-voltage switching of secondary-side devices. Turn-on switching transition loss of primary devices is also negligible. 3) Soft switching and NVC are inherent and load independent. 4) The voltage across primary-side device is independent of duty cycle with varying input voltage and output power and clamped at rather low reflected output voltage enabling the use of low-voltage semiconductor devices. These merits make the converter good candidate for interfacing low-voltage dc bus with high-voltage dc bus for higher current applications. Steady state, analysis, design, simulation, and experimental results are presented.

Interleaved Phase-Shift Full-Bridge Converter With Transformer Winding Series–Parallel Autoregulated (SPAR) Current Doubler Rectifier

Abstract—
The analysis and design guidelines for a two-phase interleaved phase-shift full-bridge converter with transformer winding series–parallel autoregulated current doubler rectifier are presented in this paper. The secondary windings of two transformers work in parallel when the equivalent duty cycle is smaller than 0.25 but in series when the duty cycle is larger than 0.25 owing to the series–parallel autoregulated rectifier. With the proposed rectifying structure, the voltage stress of the rectifier is reduced. Also, the interleaving operation reduces the output current ripple. A 1-kW prototype with 200–400-V input and 50-V/20-A output is built up to verify the theoretical analysis.

Hybrid-Type Full-Bridge DC/DC Converter With High Efficiency

Abstract—
This paper presents a hybrid-type full-bridge dc/dc converter with high efficiency. Using a hybrid control scheme with a simple circuit structure, the proposed dc/dc converter has a hybrid operation mode. Under a normal input range, the proposed converter operates as a phase-shift full-bridge series-resonant converter that provides high efficiency by applying soft switching on all switches and rectifier diodes and reducing conduction losses. When the input is lower than the normal input range, the converter operates as an active-clamp step-up converter that enhances an operation range. Due to the hybrid operation, the proposed converter operates with larger phase-shift value than the conventional converters under the normal input range. Thus, the proposed converter is capable of being designed to give high power conversion efficiency and its operation range is extended. A 1-kW prototype is implemented to confirm the theoretical analysis and validity of the proposed converter.

Hybrid Transformer ZVS/ZCS DC–DC Converter With Optimized Magnetics and Improved Power Devices Utilization for Photovoltaic Module Applications

Abstract—
This paper presents a nonisolated, high boost ratio dc–dc converter with the application for photovoltaic (PV) modules. The proposed converter utilizes a hybrid transformer to incorporate the resonant operation mode into a traditional high boost ratio active-clamp coupled-inductor pulse-width-modulation dc– dc converter, achieving zero-voltage-switching (ZVS) turn-on of active switches and zero-current-switching turn-off of diodes. As a result of the inductive and capacitive energy being transferred simultaneously within the whole switching period, power device utilization (PDU) is improved and magnetic utilization (MU) is op-timized. The improved PDU allows reduction of the silicon area required to realize the power devices of the converter. The optimized MU reduces the dc-bias of magnetizing current in the magnetic core, leading to smaller sized magnetics. Since the magnetizing current has low dc-bias, the ripple magnetizing current can be utilized to assist ZVS of main switch, while maintaining low root-mean-square (RMS) conduction loss. The voltage stresses on the active switches and diodes are maintained at a low level and are independent of the wide changing PV voltages as a result of the resonant capacitor in series in the energy transfer loop. The experimental results based on 250 W prototype circuit show 97.7% peak efficiency and system CEC efficiencies greater than 96.7% over 20 to 45 V input voltages. Due to the high efficiency over wide power range, the ability to operate with a wide variable input voltage and compact size, the proposed converter is an attractive design for PV module applications.

High-Power-Factor Rectifier Using the Modified SEPIC Converter Operating in Discontinuous Conduction Mode

Abstract—
The theoretical and experimental analysis of a modified version of the SEPIC dc–dc converter used as preregulator operating in discontinuous conduction mode (DCM) is presented in this paper. The proposed converter presents a low input current ripple operating in DCM, and the switch voltage is lower than the output voltage. The switch voltage reduction increases the converter reliability and a low drain-to-source on-resistance (RDSon ) MOSFET can be used depending on the converter specification. Moreover, a digital control technique is applied to the proposed converter in order to reduce the third-harmonic input current distortion resultant of the operation in DCM. Finally, a 100-W prototype was developed operating with efficiency equal to 95.6%.

High-Frequency-Fed Unity Power-Factor AC–DC Power Converter With One Switching Per Cycle

Abstract—
This paper presents a power converter and its control circuit for high-frequency-fed ac to dc conversion. Based on the resonant technique, the input current is shaped to be sinusoidal and is forced to follow the high-frequency sinusoidal input voltage so as to achieve unity power factor. With the proper selection of the characteristic impedance of the resonant tank, the converter is able to perform the function of a buck, boost, or buck–boost converter. The initial condition of the resonant tank is used to control the output voltage gain of the converter. Since all the switches are operated at the fundamental frequency of the input ac source, the switching loss of the converter is small. A control scheme is also proposed for the converter. A proof-of-concept prototype operating at 400 kHz is constructed and its performance is experimentally measured. Results show that the proposed converter operates as theoretically anticipated.