Eloi Agostini

This article proposes a three-level isolated soft-switching DC-DC converter based on a modified T type commutation cell. While wide-range zero-voltage switching (ZVS) in three-level converters is often achieved using auxiliary circuits or additional resonant elements, the proposed topology ensures wide ZVS operation by relying solely on the effective series inductance and the transformer magnetizing inductance. All active switches operate under ZVS over a wide load range, extending the application of the modified T-type cell to isolated PWM DC-DC conversion. A simple PWM strategy is employed, and both continuous and discontinuous conduction modes are described and investigated. A detailed mathematical analysis covering both continuous and discontinuous conduction modes is presented, supporting the development of a comprehensive, step-by-step design methodology. In addition, a small-signal analysis provides information about the dynamic behavior of the converter, enabling the proper design of a closed loop control system. Experimental results obtained with a 1.5 kW prototype operating at 100 kHz, with an input voltage of 450 V and an output voltage of 300 V, confirm the feasibility of the proposed topology. The prototype exhibits an efficiency curve that remains nearly constant over the 10–100% load range, achieving efficiencies above 95.40% across the entire operating range and a peak efficiency of 97.47% at 1.2 kW.

A non-isolated single-stage LED driver based on the totem-pole rectifier requiring reduced dc-bus voltage is introduced in this article. The proposed topology requires a low component count and exhibits high efficiency. Charge-pump and resonant capacitor concepts are used to achieve reduced LED current ripple, high power factor and dc-bus voltage levels close to the input voltage peak value. Experimental results of two built prototypes operating with input voltages of 127 V-rms and 220 V-rms, output voltage of 90 V and 140 V, and rated power of 45 W and 70 W, respectively, are presented and validate the analysis carried out. The measured dc-bus voltage at rated power condition is 220 V for an input voltage of 127 V-rms and 360 V for 220 V-rms, demonstrating the capability of the proposed circuit to guarantee reduced dc-bus voltage levels. In addition, both prototypes exhibited efficiencies up to 95.2%, therefore indicating the potential of the proposed LED driver for high-efficiency operation.

Renewable solar energy is an excellent alternative to conventional energy sources and, recently, it has shown remarkable growth on electrical power grid in various countries around the world. Maximum power point tracking (MPPT) has critical importance in solar energy generation since it increases the system's efficiency in many scenarios. Photovoltaic modules (PV) are influenced by environmental factors such as temperature and solar irradiation density, changing the amount of energy generated throughout the day. In order to extract the maximum available power from a PV, it’s necessary to use the MPPT technique, which considers the system’s nonlinearities. Maximum power tracking (MPP) is done by tuning the duty cycle of the DC-DC converter, so that the PV's terminal voltage is modulated to match the environmental conditions. This tuning, generally, is dependent on sensor readings. Normally, only the module’s voltage and current sensors are used, due to the low cost and ease of acquisition of these signals. However, intelligent techniques demand the usage of temperature and irradiation sensors, increasing the complexity of the system’s implementation. The use of intelligent control techniques applied to the energy generation system has had a notable presence in recent publications. The high efficiency obtained from its application demonstrates that the use of intelligent systems in the decision-making process is a useful tool in obtaining maximum generation power. The objective of the present study is the development and simulation via MATLAB/SIMULINK of a battery charging system with solar energy, which consists of a PV, a Buck converter, a 12V battery, and the MPPT controller. The intelligent fuzzy logic MPPT technique (FLS) and the classical incremental conductance technique (INC) will be compared, both techniques using only voltage and current measurements.

This article proposes an improved isolated four-switch three-level half-bridge dc-dc converter suitable for high-input-voltage applications. The primary switches operate under ZVS for a wide load range, which is accomplished by the inclusion of an auxiliary inductance in the circuit. In addition, the conditions necessary to ensure ZCS for the output rectifiers are determined. A detailed mathematical analysis is carried out, allowing the proper design of the circuit. Output voltage control and input voltage balance are also investigated in detail. The analyses are validated by experimental tests performed with a 1 kW prototype, operating at 100 kHz, with an input voltage range of 700–800 V and output voltage of 400 V. Efficiency levels up to 96.13% and higher than 90% for the entire output power range of 20–100% are demonstrated in laboratory.

This paper introduces a quasi-resonant high-efficiency high-step-up DC–DC converter requiring a reduced number of components. The proposed circuit uses a coupled inductor associated with voltage multiplier cells to ensure high-voltage-gain operation without the necessity of an extremely high number of turns ratio. Quasi-resonant operation guarantees zero current switching (ZCS) for some diodes of the converter. A detailed steady-state analysis is carried out aiming at the adequate design of the circuit. Experimental results taken from the testing of a 400 W prototype operating in closed loop with an input voltage range of 25–48 V, output voltage of 400 V and switching frequency of 100 kHz validate the analysis carried out and demonstrate the feasibility of the proposed converter.

This paper introduces a high-step-up dc-dc converter to provide voltage boosting in low-voltage applications. The circuit contains only a single active switch and is based on the boost-type converter using coupled inductor and voltage multiplier cell. The proposed topology exhibits high efficiency, reduced voltage stress on the semiconductors and requires a low component count. The circuit is intended for applications with rated power in the order of a few hundreds of Watts, which corresponds to the typical level of a single photovoltaic (PV) module. A detailed mathematical description of the circuit operation is carried out, providing the means for the adequate design of the converter. The dynamic analysis is also addressed in the paper, and proper closed-loop operation is demonstrated. A 400 W prototype operating at 90 kHz, with an input voltage range of 24-48 V and output voltage of 400 V was built and tested in laboratory. Experimental results validate the analyses carried out and measurements indicate efficiency levels up to 97.5%, which ratifies the proposed converter as a good solution for typical PV applications.

This paper presents a single-stage converter based on the boost-PFC and charge-pump circuits configured as a current source. The integration between the input and the dc-link stages is performed by an output stage consisting of a full wave rectifier associated to a capacitive filter, an LED array and a resonant series inductor. The charge-pump capacitors operate in order to limit the dc-link voltage and to reduce the crest factor of the current on the output inductor, thus contributing to flicker reduction. The proposed converter exhibits high efficiency and power factor (PF), and total harmonic distortion of the input current (THDi) and flicker satisfying the IEC 61000-3-2 Class C and IEEE Std 1789-2015, respectively. The operation stages and a complete mathematical model in steady state are presented in detail, allowing the converter design and implementation. In this work, a prototype operating with universal input voltage range (90270 V), dimming at 127 V and 220 V, switching frequency in the range of 40200 kHz and a nominal output power of 43 W is built to demonstrate the feasibility of the proposed lighting system.

An isolated soft-switching dc-dc converter based on the t-type commutation cell and employing capacitive output filter is introduced in this paper. A hybrid switching strategy is proposed, allowing the circuit to operate with a 3- or 4-level scheme relying on a unique duty cycle definition. The energy transfer process regarding two distinct continuous conduction modes is detailed and a complete static model is derived. Also, the requirements for the occurrence of zero voltage switching (ZVS) on the switches are evaluated, and a small-signal analysis is carried out to provide information on the dynamic behavior of the proposed circuit. The operation of the proposed converter is verified for the conditions of fixed input and output voltage and of wide input voltage range designs. Laboratory tests with a 1.2 kW prototype operating in closed loop demonstrate the feasibility of the proposed circuit and validate the theoretical analysis carried out.

A single-stage high-power-factor LED driver based on the integration of the bridgeless boost rectifier with the nonresonant half-bridge converter (BLB-HB-NR) employing a hybrid modulation strategy is introduced in this article. A key feature of the proposal is that the system can operate with universal input voltage range and dimming from 100% to 10% of rated output power while keeping the dc-link voltage limited to a safe level. In the proposed hybrid scheme, the LEDs current is regulated by pulse-frequency-modulation (PFM) while the dc-link is controlled using an asymmetrical-pulsewidth-modulation strategy. The system owns important operational and constitutive features, such as reduced component count, high-power factor and soft switching on the main switches, thus a high-efficiency operation is achieved. Steady-state and dynamic analyses are discussed in the article and a complete control strategy is also elaborated. Finally, experimental results for a universal input voltage, 42 W output power prototype demonstrates the feasibility of the proposed lighting system.