N. Lakshmi Narasamma

Bio: N. Lakshmi Narasamma is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Ćuk converter & Auxiliary power unit. The author has an hindex of 2, co-authored 2 publications receiving 98 citations.

An Active Soft Switched Phase-Shifted Full-Bridge DC–DC Converter: Analysis, Modeling, Design, and Implementation

Abstract: A novel active soft switched phase-shifted full-bridge (PSFB) dc-dc converter is presented in this paper. An auxiliary circuit is added to the pulse width modulation counterpart to achieve the soft switching. The proposed circuit achieves soft switching for both main and auxiliary switches, without increasing the main device current/voltage rating. The auxiliary circuit is gated appropriately in order to achieve zero voltage switching for lagging leg. Tapping in the primary winding of power transformer is added for the purpose of commutation. The proposed circuit is capable of operating at elevated switching frequencies of several hundreds of kilohertz in a range of line and load variations. Steady-state analysis and evaluation of losses for the proposed circuit is presented. Analytical models valid for steady state and dynamic performance are proposed. A 350-W, 100-kHz active soft switched PSFB dc-dc converter prototype is implemented. The proposed analytical models are validated experimentally on 350-W prototype. Experimental results verifying steady state and dynamic models are presented.

A new auxiliary current injection circuit for improved transient response of step-up/step-down DC-DC converters

Abstract: In this paper, a new auxiliary current injection circuit (ACIC) is developed aiming at improvement in the dynamic response of DC-DC converters under load transients. The developed ACIC can be used as a generic auxiliary module for both step-up/step-down DC-DC converters. The auxiliary current injection circuit is a bidirectional power converter, designed for low power ratings with higher bandwidth, to operate only during load transients. The performance of the developed auxiliary power converter has been evaluated in conjunction with an interleaved boost converter as main converter, which has limitation on bandwidth due to its inherent right half plane zero. Experimental results for a 250 W, 100 kHz interleaved boost converter prototype with auxiliary current injection circuit are presented. The peak overshoot/undershoot and the transient recovery time are reduced significantly with the incorporation of developed ACIC.

Soft-Switching DC–DC Converter for Distributed Energy Sources With High Step-Up Voltage Capability

Abstract: This paper presents high step-up dc-to-dc converter for low voltage sources such as solar photovoltaics, fuel cells, and battery banks. To achieve high voltage gain without large duty cycle operation, combination of coupled inductor and switched capacitor voltage doubler cells are used. By incorporating active clamp circuit, voltage spike due to the leakage inductance of the coupled inductor is alleviated and zero-voltage switching turn on of the main and auxiliary switch is obtained. Due to the use of MOSFETs of low voltage rating and soft turn on of the switches, conduction loss and switching losses are reduced. This improves the efficiency and power density of the converter. The proposed converter can achieve high voltage gain with reduced voltage stress on MOSFET switches and output diodes. Design and analysis of the proposed converter is carried out, and finally, a 500-W experimental prototype is built to verify theoretical analysis.

A New ZVS Full-Bridge DC–DC Converter for Battery Charging With Reduced Losses Over Full-Load Range

Abstract: A new zero-voltage switching full-bridge dc–dc converter for battery charging is proposed in this paper. The proposed isolated dc–dc converter is used for the dc–dc conversion stage of the electric vehicle charger. The primary switches in dc–dc converter turn- on at zero voltage over the battery-charging range with the help of passive auxiliary circuit. The diode clamping circuit on the primary side minimizes the severity of voltage spikes across the secondary rectifier diodes, which are commonly present in conventional full-bridge dc–dc converters. The main switches are controlled with an asymmetrical pulse-width modulation (APWM) technique resulting in higher efficiency. APWM reduces the current stress of the main switches and the circulating losses compared with the conventional phase-shift modulation method by controlling the auxiliary inductor current over the entire operating range of the proposed converter. The steady-state analysis of auxiliary circuit and its design considerations are discussed in detail. A 100-kHz 1.2-kW full-bridge dc–dc converter prototype is developed. The experimental results are presented to validate the analysis and efficiency of the proposed converter.

Secondary-Side Phase-Shift-Controlled Dual-Transformer-Based Asymmetrical Dual-Bridge Converter With Wide Voltage Gain

Abstract: A novel dual-transformer-based asymmetrical dual-bridge (DT-ADB) converter with secondary-side phase-shift control strategy is proposed. The primary side of the DT-ADB converter is a fully active full bridge, and the secondary side is a semiactive bridge comprising of one active leg and two passive legs. The current and power of the two transformers in the converter are shared automatically by adopting primary-side-series and secondary-side-parallel configuration, and the turns ratio of the transformer is reduced by employing two transformers. The high-frequency-link inductor is reduced because the voltage applied on the inductor is reduced compared to previous converters, and hence the efficiency and power density can be improved. Zero-voltage turn-on of all the active switches and zero-current turn-off of all the diodes are achieved in a wide operation range. Furthermore, the turn-off losses of the secondary-side active switches are reduced because only half of the output current flows through the switches. Moreover, the proposed topology offers several other advantages including continuous output current and smaller output filter requirement. The operation principle is analyzed and experimental results are provided to verify the effectiveness and advantages of the proposed converter.

An Overview of High-Conversion High-Voltage DC–DC Converters for Electrified Aviation Power Distribution System

Abstract: This article presents the state-of-the-art review of high-conversion high-voltage (HCHV) dc–dc converters for a modern aerial vehicle’s power distribution system. Higher dc bus voltages have become a trend in recent aerial vehicle development because of the potential reduction in size and weight of the rest of the power system and an increase in power density. Some front-end dc energy sources, such as fuel cells, batteries, and supercapacitors, may level at a low voltage and require HCHV dc–dc converters to integrate with the high-voltage dc bus. On the other hand, high-conversion step-down converters are required between the dc bus and various low-voltage electronic loads. A detailed review of HCHV dc–dc converters for an aviation power distribution system is limited in the literature. This article presents two main architectures of such converters. Architecture-I employs individual two-port dc–dc converters to link each source to the dc bus, and Architecture-II uses a single multiport converter (MPC) to connect all the sources to the dc bus. Architecture-I categorizes the two-port dc–dc converter topologies into unidirectional and bidirectional converters, followed by further classifications based on isolation and control schemes. Multiport dc–dc converters for Architecture-II are categorized based on port numbers and then source connection methods. This review investigates multiple topologies within each category or classification, highlighting selected circuit diagrams and their features and shortcomings. This article presents several insightful comparisons, among various bidirectional converters for Architecture-I, and MPCs for Architecture-II, for a designer to choose a proper converter. In terms of converter characteristics, this article focuses on dc voltage gain, power density, efficiency, and reliability, as these qualities are of utmost importance in an aviation application.

Integrated Dual Full-Bridge Converter With Current-Doubler Rectifier for EV Charger

Abstract: A novel converter topology for high-power battery charger applications is proposed in this paper. The topology adopts the integration structure of two full-bridge converters, which shares one leg of switching device called center-leg. The two full-bridge converters are placed in parallel on the primary side, and are driven in a phase-shift manner. The integrated form of two current-doubler rectifier is adopted on the secondary side, and it has full-bridge structure. With this structure, the proposed converter can overcome drawbacks of the conventional phase-shift full-bridge converter; narrow zero-voltage-switching range, large duty-cycle loss, and high component counts. The validation of the proposed converter is confirmed by the experiment with a prototype battery charger of 5.7 kW and 13.5 A.