Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck-flyback converter (IBFC) developed in previous works. In this application, the converter is used to provide power-factor correction from a universal ac source. A control loop using the LM3524 IC has been implemented for testing the feasibility of Enabling pulsewidth modulation dimming mode. First, the LED load has been linearized and modeled in order to calculate the IBFC topology properly. Second, the converter has been designed and tested at the laboratory. The converter has also been modeled in order to design a fixed-frequency constant-current control. The dynamics of all the stages involved in the closed loop have been taken into account in order to develop an adequate controller. Finally, the experimental results obtained from the laboratory tests are discussed.

In this paper, a new technique for controlling dc-dc resonant converters is investigated. A variable inductance is used to control and regulate the dc output voltage maintaining constant switching frequency for the half-bridge transistors. The output voltage characteristics of the series resonant and parallel resonant converters under the proposed magnetic control are obtained and analyzed. In order to evaluate the proposed technique, a laboratory prototype for a 48 V-input 5 V/10 A-output 500 kHz parallel resonant converter is presented. A methodology for obtaining the converter dynamic response using a step response test is carried out. From the dynamic response, a compensator for operating the converter at closed loop is developed and tested in the laboratory. The results prove that the proposed technique is suitable for controling resonant inverters at constant frequency using a low-cost half-bridge inverter.

The use of supply frequencies above 50-60 Hz allows for an increase in the power density applied to the ozonizer electrode surface and an increase in ozone production for a given surface area, while decreasing the necessary peak voltage. Parallel-resonant converters are well suited for supplying the high capacitive load of ozonizers. Therefore, in this paper the current-fed parallel-resonant push-pull inverter is proposed as a good option to implement high-voltage high-frequency power supplies for ozone generators. The proposed converter is analyzed and some important characteristics are obtained. The design and implementation of the complete power supply are also shown. The UC3872 integrated circuit is proposed in order to operate the converter at resonance, allowing us to maintain a good response disregarding the changes in electric parameters of the transformer-ozonizer pair. Experimental results for a 50-W prototype are also provided.

The goal of this paper is the evaluation of the interleaved buck converter as a high-brightness (HB) LEDs electronic driver, comparing its performance with the standard buck converter. The main drawbacks of the standard converter come from the high inductor value necessary to guarantee low output current ripple, which result in high inductor losses and rough switching waveforms at the semiconductors. Additionally, when the application demands pulsewidth modulation (PWM) dimming, this high inductance value yields to a relatively low dimming frequency that can result in audible noise problems due to several phenomena as magnetostrictive effects at the inductors or piezoelectric effects at the capacitors. The proposed interleaved converter obtains low output current ripple with much smaller inductances, thus allowing PWM dimming at higher frequencies (20 kHz and beyond), avoiding audible noise. Moreover, such low inductances, along with the triangular waveforms obtained with the proposed control method, yield to a higher efficiency than in the standard converter. After reviewing the main operation concept of the interleaved converter, a full design process is particularized for driving HB LEDs. A full-dimming range experimental setup has been built and tested, and experimental results are shown and discussed, compared with those obtained for the standard converter.

Due to the high rise in luminous efficiency that HB-LEDs have experienced in the last recent years, many new applications have been researched. In this paper, a streetlight LED application will be covered, using the integrated buck-flyback converter developed in previous works, which performs power factor correction (PFC) from a universal AC source, as well as a control loop using the LM3524 IC, which allows PWM dimming operation mode. Firstly, the LED load will be linearized and modeled in order to calculate the IBFC topology properly. Afterwards, the converter will be calculated, presenting the one built in the lab. Secondly, the converter will be modeled in order to build the closed loop system, modeling the current sensor as well in order to develop an adequate controller. Finally, experimental results obtained from the lab tests will be presented.