André Luís Kirsten

A Novel Flyback-Based Input PFC Stage for Electronic Ballasts in Lighting Applications

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and analyzed, and a design example for a 50-W light-emitting diode lamp is presented. The most relevant simulation and experimental results are also shown, in order to validate the idea. A comparison in terms of efficiency for the input stage is carried out between the proposed topology and the conventional flyback converter, showing an efficiency enhancement in the proposed converter. However, the most important advantage of the proposed converter is outlined in the final part of this paper. This advantage comes from the avoidance of the input diode bridge, thus enabling the bidirectional power flow at the input stage. Therefore, the topology can be used to deliver energy into the power grid. In recent lighting applications, the use of micro renewable generators in lighting points has made the use of special electronics to handle the energy flows in the ballast necessary. The present topology is an alternative to standard bidirectional input stages.

Microcontroller-Based High-Power-Factor Electronic Ballast to Supply Metal Halide Lamps

The analysis, design, and implementation of a microcontroller-based electronic ballast to supply metal halide (MH) lamps are presented. The proposed topology is based on the integration of the buck and flyback converters, the former providing power factor correction and the latter controlling lamp power. The lamp is supplied by a low-frequency square-waveform current, which is a convenient way to avoid acoustic resonances in high-intensity discharge lamps. Both converters operate in discontinuous conduction mode, thus allowing the use of only one high-frequency switch and simplifying the control. The electronic ballast is digitally controlled by using a low-cost microcontroller PIC16F684. The microcontroller performs all the necessary tasks during starting, warming-up, and steady state, including closed-loop control of lamp current and protections. The closed-loop control takes into account the lamp dynamical impedance. Experimental results for a 35-W MH lamp are presented, and the obtained overall efficiency is 90%.

Digital Control Strategy for HID Lamp Electronic Ballasts

This paper presents the analysis, design, simulation and experimental results of a digital control strategy applied to an electronic ballast to supply a 70-W high-pressure-sodium lamp. The electronic ballast consists of a single-stage converter that integrates a buck converter to provide power factor correction and two flyback converters to supply the lamp, with low frequency square waveform, in order to avoid the acoustic resonance phenomenon occurrence. The proposed digital control strategy is composed of three control loops: voltage loop for lamp ignition and warm-up, an inner current loop for steady state, and a slow outer power loop to maintain the lamp power constant during its useful life. The lamp dynamic model is included to the ac model of the converter, so the effects of its right-half-plane zero are considered to design the digital control system. Fixed-point simulation is presented using Q base number format, where the exact variable values employed in the microcontroller code are used. Experimental results are included to demonstrate the performance of the proposed digital control strategy.

A novel flyback-based input PFC stage for electronic ballasts in lighting applications

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and analyzed, and a design example for a 50-W light-emitting diode lamp is presented. The most relevant simulation and experimental results are also shown, in order to validate the idea. A comparison in terms of efficiency for the input stage is carried out between the proposed topology and the conventional flyback converter, showing an efficiency enhancement in the proposed converter. However, the most important advantage of the proposed converter is outlined in the final part of this paper. This advantage comes from the avoidance of the input diode bridge, thus enabling the bidirectional power flow at the input stage. Therefore, the topology can be used to deliver energy into the power grid. In recent lighting applications, the use of micro renewable generators in lighting points has made the use of special electronics to handle the energy flows in the ballast necessary. The present topology is an alternative to standard bidirectional input stages.

Bidirectional Grid-Tie Flyback Converter Applied to Distributed Power Generation and Street Lighting Integrated System

This paper presents a multifunctional bidirectional converter applied to street lighting and photovoltaic (PV) microgeneration systems. The proposed converter works as an electronic driver supplying a street lighting luminaire based on light emitting diodes (LEDs) at night, from ac single-phase mains with high power factor and reduced harmonic distortion. During daylight hours, the converter injects the produced energy by a PV panel to the grid, working as a grid-tie inverter. The proposed topology is based on the integration of two flyback converters, one for each half-cycle of the grid voltage, avoiding the usual diode bridge rectifier for LED lamps drives, thus providing a bidirectional power flow. A prototype of the proposed electronic stage has been designed, built, and tested, in order to validate the system. Finally, experimental results are presented. In rectifier mode, an efficiency of 86% was achieved, whereas an efficiency of 89% was obtained in inverter mode.

Analysis of the Output Capacitor and Lamp voltage Inversion for the Bidirectional Flyback Converter

This paper presents a lamp voltage inversion methodology and output capacitor analysis applied to a bidirectional flyback converter. The converter integrates the power control and the inversion stage, feeding a HPS lamp with a low frequency symmetrical square waveform, avoiding the acoustic resonance phenomenon occurrence. A detailed design of the lamp parallel capacitor is developed with parameters of stability, lamp power high frequency ripple and the lamp voltage inversion time to avoid lamp re-ignition. Experimental results are presented to validate the proposed topology.

Study of a flyback-based stage as grid interface topology for micro-generation applications

Nowadays, different power generation strategies for grid-connected systems can be found, ranging from single high power plants (tens and hundreds of MW), to thousands of small wattage (below 1 kW) micro-generators. This paper studies a new power topology for the latter, based on a bidirectional Flyback converter. The comparison with the standard topology for this kind of converters is carried out, and the constraints for the control scheme are also studied.

Performance analysis of modular converter for solid state transformers

This paper proposes a performance analysis of a modular topology applied to solid state transformers regarding the conduction losses in the converters. The modular concept presents high reliability in medium and high voltage applications. However, the definition of the number of modules for one specific application is a difficult task. The full analysis of the semiconductors conduction losses for a module with a cascade multilevel, a dual active bridge and a full bridge inverter is presented. An algorithm that returns the lowest losses for n number of cells is developed.

Bidirectional Flyback converter connected to the grid and applied to a distributed microgeneration and street lighting system

This paper presents a multifunctional bidirectional converter. The proposed converter works as a grid-tied inverter, injecting power coming from a PV subsystem to the AC mains in the daytime hours, but also supplies energy to a LED-based street lighting system at night. The topology is based on the integration of two Flyback converters thus allowing the desired bidirectional energy flux. Each Flyback has a different polarity, making energy flowing in both directions possible. A prototype was built in order to prove the feasibility of the proposed topology and experimental results are shown below. In rectifier mode, an efficiency of 86% was achieved while a 88.9% in inverter mode.

Hybrid system of distributed power generation and street lighting based on LEDs: Grid connection

This work proposes an electronic driver for street lighting systems integrated to renewable energy. In recent lighting applications, the use of micro renewable generators in lighting points makes necessary the use of special electronics to handle the bidirectional energy flow in the ballast. The proposed input stage is a topology based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage, allowing the converter operate with bidirectional energy flow. Thus, this system has two distinct operation modes. The rectifier mode is responsible to supply a street lighting system based on LEDs from de utility grid during the night, and the inverter mode must deliver energy into the power grid provided by a solar panel during the day. This work focuses in the inverter stage, which comprises a boost converter, responsible for the Maximum Power Point Tracking (MPPT), and a flyback inverter. The present topology is an alternative to standard bidirectional input stages, as it can be used to deliver energy into the power grid, due the avoidance of the input diode bridge.