Carlos Henrique Gonçalves Treviso

A new ZCS-ZVS-PWM boost converter with unity power factor operation

This paper introduces the self-resonance concept as a new way to obtain power converters without switching losses. Using this new approach, a self-resonant ZCS-ZVS-PWM boost power converter is presented. It is suitable for high switching frequency, high power operation and wide range of power. The converter control is done by using PWM technique, with constant frequency operation. The complete theoretical analysis and simulation results for the self-resonant PWM boost power converter, operating without power factor correction, are presented. Moreover, experimental results for this new boost converter, operating with unity power factor, support the validity of this new approach.<<ETX>>

A self-resonant-PWM boost converter with unity power factor operation by using a bang-bang current control strategy with fixed switching frequency

A boost converter operating with high power factor and without commutation losses is presented in this paper. The almost unity power factor operation is obtained by using a bang-bang hysteresis current waveshaping technique with fired switching frequency. A self-resonant PWM auxiliary circuit is incorporated in the hard boost converter and a lossless commutation is performed. The operational characteristics of the converter are verified by simulation.

Non-isolated DC-DC converters with wide conversion range used to drive high-brightness LEDs

Light emitting diodes (LEDs) have many features that make them attractive for use in an increasing number of applications. Particularly in lighting, the small size of LEDs compared to fluorescent and incandescent bulbs is a prominent advantage. This paper presents two topologies based on the buck converter, which have higher step-down characteristic than that of the original converter. The quadratic buck converter is studied and used to drive series-connected LEDs. Improved characteristics if compared with the traditional converter include the continuous current maintained through the LEDS and the possibility of driving several types of LED arrays. The study is then extended to the cubic buck converter, as a novel arrangement to obtain the mentioned step-down characteristic is introduced in this work. The use of such converter allows obtaining lower output voltages than those resulting from the quadratic buck converter. Experimental prototypes of the converters are implemented and fully tested. It must be also mentioned that a PIC microcontroller is used to control the current through the LED array, what provides robustness and flexibility in the adjust of the control algorithm without the need of hardware modification.

A 1.5 kW operation with 90% efficiency of a two transistors forward converter with non-dissipative snubber

This paper presents a nondissipative snubber forward power converter. As result of this topology, the switching losses are reduced. The proposed approach allows one to obtain better operating performances than those already known for hard-switching PWM operating at higher switching frequencies and with a wide range of power. The switches are not submitted to overvoltages and the peak of current across the switches can be adjusted by the suitable choice of the resonant capacitor and inductor.

An unity power factor operation symmetrical power supply

This paper presents an AC/DC power converter which can operate as a symmetrical power supply. The AC input voltage and current waveforms are closely in phase and present a very low harmonic distortion. Consequently, the proposed power converter is able to work with unity power factor. A symmetrical output voltage source was obtained by associating Cuk and SEPIC converters using a common input stage. A 500 watts prototype operating at 100 kHz fixed switching frequency was implemented. PSPICE simulation and a laboratory prototype operating with open and closed loops was realized and the results have proved the operating principles of the structure and the implemented control strategy.

A 1.5 kW two transistors forward converter using a non-dissipative snubber

This paper will present a 1.5 kW operation with 90% efficiency at full load of a two transistors forward converter with non-dissipative snubbers. The proposed approach allows building a converter with high frequency operation. A detailed analysis of the operation will be presented. The output voltage is controlled by PWM with a constant frequency. The complete operating principles, theoretical analysis, relevant equations, simulation and experimental results will be presented.

Complete design for a 1,2 kVA UPS, with sinusoidal output stabilized, operating with digital control for DSC (digital signal controller)

This paper presents a UPS topology formed by a rectifier, a fly-back converter that serves to keep the batteries charged, two Forward converters operating in parallel lagged by 180° that feed the inverter in the absence of commercial network 260 V and with a full bridge inverter circuit. The resultant power is 1200 W, with a pulse frequency of 25 kHz, the control, signs and protections are implemented in digital form through a digital signal controller (DSC). It presented a comprehensive analysis of the stages of operation and the design procedures for the correct operation of this topology. Simulation results, corresponding to the full functioning of the circuit, are presented to validate the system analysis.

A 6 kW rectifier, unity power factor, three-phase, nondissipative commutation in DC-DC converter and synchronized control in frequency

This paper presents a three-phase rectifier, unity power factor, nondissipative commutation in DC-DC converter and synchronized frequency control, working with 89% of global efficiency and low level RFI. The proposed structure allows the operation with high switching frequency. The output voltage is controlled by PWM with a constant frequency. The operation principle, theoretical analysis from DC converter, relevant equations, current balance control technique and experience results, are also showed in this paper.