A new transformer-less buck-boost converter is proposed, which owns a quadratic voltage gain ratio. The proposed converter (a) has only one active switch, which makes the implementation of the gate driver and control system simpler; (b) has a quadratic voltage gain without using a transformer, which equips the designers to obtain a high-voltage gain ratio and avoid the complexity of magnetic utilisations; (c) works both in step-up or step-down mode, while most of the existing quadratic topologies are able to work either in step-up or step-down mode; and (d) shares a common ground between the input and output terminals. The operating states of the proposed converter along with its steady-state performance are analysed. Then, the small-signal modelling and the power loss analysis are performed. A comparison shows the unique features of the converter, specifically in terms of voltage gain ratio and the count of power switches. Finally, the experimental results of a laboratory prototype, as well as the simulation results from PSIM software, are used for validation. The converter was tested in different conditions to inspect its transient response and to record its efficiency. The maximum recorded efficiencies in boost and buck modes, respectively were 94.7 and 93%.

This paper proposes a modified coupled-inductor SEPIC dc-dc converter for high voltage gain (< < 10) applications. It utilizes the same components as the conventional SEPIC converter with an additional diode. The voltage stress on the switch is minimal, which helps the designer to select a low voltage and low RDS-on MOSFET, resulting in a reduction of cost, conduction and turn ON losses of the switch. Compared to equivalent topologies with similar voltage gain expression, the proposed topology uses lower component-count to achieve the same or even higher voltage gain. This helps to design a very compact and lightweight converter with higher power density and reliability. Operating performance, steady-state analysis and mathematical derivations of the proposed dc-dc converter have been demonstrated in the paper. Moreover, extension of the circuit for higher gain (> 10) application is also introduced and discussed. Finally, the main features of the proposed converter have been verified through simulation and experimental results of a 400 W laboratory prototype. The efficiency is almost flat over a wide range of load with the highest measured efficiency of 96.2%, and the full-load efficiency is 95.2% at a voltage gain of 10.

In this paper, a new Semi-Quadratic High Step-Up Coupled-Inductor DC/DC Converter (SQHSUCI) with continuous input current and low voltage stress on semiconductor components is presented. The proposed structure employs a coupled-inductor (CI) and two power switches with simultaneous operation to achieve an extremely high voltage conversion ratio in a semiquadratic form. The voltage stress across the main power switch is clamped by two regenerative clamp capacitors. Here, the switching losses of both MOSFETs have been reduced by applying quasi-resonance operation of the circuit created by the leakage inductance of the CI along with the balancing and clamp capacitors. Therefore, by considering the high gain conversion ratio along with low voltage stress on components, the magnetic and semiconductors losses of the SQHSUCI are reduced significantly. Also, the energy stored in the leakage inductance of CI is recycled to the output capacitor. These features make the proposed SQHSUCI more suitable for industrial applications. The operation principle, steady-state and also comparisons with other related converters in Continuous Conduction Mode (CCM) are discussed in detail. Finally, experimental results of a prototype with 20 V input and 200 W-200 V output at 50 kHz switching frequency, verify the theoretical advantages of the proposed strategy.

Summary This paper presents a novel transformerless semi‐quadratic buck‐boost converter (SQBuBoC). In the proposed SQBuBoC, two power switches with simultaneous operation are used and a higher step‐up/step‐down voltage conversion ratio is achieved compared with the traditional buck‐boost, Cuk, single‐ended primary‐inductor converter, and Zeta converters. The positive polarity of the output voltage, along with low ripple continuous input current and common ground between the source and the output voltages, are some features that make the suggested topology more suitable for many applications with wide range of output voltage such as photovoltaic systems. Moreover, the total voltage stress across the power switches in this converter is lower than the cascade boost, and the traditional buck‐boost converters led to power MOSFETs selection with lower drain‐source ON resistance (Rds) and efficiency improvement. All the steady‐state analysis and comparisons in continuous conduction mode (CCM) are discussed in details. In addition, to study the low frequency behavior of the SQBuBoC by means of the state‐space averaging technique, the small and large signal models of this converter in CCM are presented. Finally, the SQBuBoC analysis is justified using experimental results of a 50 W step‐up 25 V to 120 V and a 28 W step‐down 25 V to 14 V laboratory prototypes.

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