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 proposes two nonisolated single-stage high power factor converters requiring low dc-link capacitance for power LEDs systems. Both converters result from the integration of the power factor correction and the LEDs driver stages, and require a relatively low dc-link capacitance value. A high power factor is demonstrated to be an inherent property of the proposed topologies and no input current control is necessary. The LEDs current is regulated by a symmetrical soft-switching half-bridge converter associated with a capacitive output filter. An accurate mathematical analysis valid for the two converters is detailed, yielding the elaboration of a step-by-step design procedure. In order to verify the analyses carried out, experimental results for two 90 W, 50 kHz, and 220 V converters are also presented.

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.

This paper proposes a nonisolated single-stage electronic system for driving power LEDs using the charge-pump and valley-fill concepts. Both concepts are related to the topological configuration based on the integration of a full-wave rectifier at the input stage with a half-bridge inverter at the output, characterizing a single-stage system. The charge-pump configuration is used to reduce the LEDs' current ripple. The valley fill is employed to limit the dc bus voltage at levels below the peak value of the input voltage but maintaining a high-power factor operation. Therefore, it is possible to use bus capacitors with reduced voltage ratings. The operating principle of the proposed converter, which includes three operating modes in steady state, is presented and analyzed. The design methodology and the experimental results are also presented so that the operational characteristics of the proposed system can be verified. A 47-W, 220-Vac input, 67 kHz, 93.5% peak-efficiency prototype is built and tested to validate the carried out analyses.

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.

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.