Edilson M. Sa

Junction Temperature Estimation for High Power Light-Emitting Diodes

The understanding of the thermal properties of a high power LEDs is essential in order to achieve the highest optical performance of the device without sacrificing its reliability. In addition to that, the good thermal management is also a key factor to avoid thermal induced variation of the photometric / colorimetric properties of power LEDs, such as variation of relative light output or the spectrum. This paper proposes a methodology to estimate junction temperature of high power LEDs. This method allows discarding the influence of the intrinsic series resistance of the LED electric model in 1-V curve, avoiding, as a consequence measurement errors.

A switched-capacitor driver for power LEDs

This paper proposes a switched-capacitor converter to drive power light emitting diodes (LEDs). In contrast to conventional constant dc current drivers, the current pulse is provided by this switched-capacitor LED driver. In the present driver, the capacitor is charged and discharged through of the output circuit and the current flow direction is controlled by switch. Based on the charge control analysis, the effects of switching devices on the proposed converter are discriminated and evaluated. The experimental results demonstrated the technical feasibility of using the proposed converter for LEDs.

Single stage switched capacitor LED driver with high power factor and reduced current ripple

This paper presents a switched capacitor-based converter to drive high power light emitting diodes (LEDs). Unlike the traditional switched capacitor based one, the proposed converter uses an inductor to avoid the forced charging and discharging operation reducing stress current in circuit. The proposed converter provides inherent power factor correction (PFC) and the switched capacitors are used as isolation capacitors. The proposed converter also uses a LC filter to reduce the output current ripple through LED array instead using a bulk electrolytic capacitor. The basic description of the topology is presented and a laboratory prototype of 48 W has been implemented. The experimental results presented demonstrate the technical feasibility of the proposed converter applied as LED driver.

Off-line a single-stage resonant switched capacitor high-power-factor LED driver

This paper proposes a resonant switched capacitor-based converter to driver high power light emitting diodes (LEDs). Unlike the traditional switched capacitor based one, the proposed converter uses an inductor to avoid the forced charging and discharging operation reducing stress current in circuit. The proposed converter provides inherent power factor correction (PFC) and the switched capacitors are used as isolation capacitors. The basic description of the topologcy is presented and a 49 W, 220 V ac grid laboratory prototypes has been implemented. The experimental results presented demonstrate the technical feasibility of the proposed converter applied as LED driver.

AC-DC single-switch three-phase converter with peak current control for power LEDs

This paper presents the development of a three-phase AC-DC flyback converter without electrolytic capacitor with power factor correction applied on street lighting using power LEDs. Recent studies suggest that the lifetime and reliability of an electronic ballast can be improved removing the electrolytic capacitors, considering that the lifetime of these devices has strong influence of the operating temperature. A single-switch three-phase topology is proposed, and a prototype is developed. The experimental results prove the feasibility of this technology in electronic ballasts for LEDs. The prototype has an output power of 54 W, power factor of up to 0.99 and efficiency up to 77%, depending on the operating conditions. This prototype can operate in a wide range of input voltages and also has a peak current control strategy, which reduces design costs due the using of a low cost controller.

A LED driver with switched capacitor

This paper proposes a switched capacitor-based converter to drive high-power light-emitting diodes (LEDs). In contrast to conventional constant current dc drivers, the current pulse is provided by a switched capacitor. The proposed approach differs from the traditional switched-capacitor-based one, because it uses a small inductor to improve the switching behavior of the converter. Based on the charge control analysis, the effects of switching devices on the proposed converter are evidenced and evaluated. A 6 W, 24 V laboratory prototype has been implemented, while experimental results are presented and discussed to demonstrate the technical feasibility of the proposed converter applied as LED driver.

A step-up switched-capacitor converter for LEDs applied to photovoltaic systems

This paper proposes a DC-DC step-up converter with a switched capacitor to power light-emitting diodes (LEDs), which may be applied to an autonomous system, e.g. PV system. In the converter is used a small additional inductor operating in discontinuous conduction mode (DCM) which allows zero current switching (ZCS), reducing circuit losses. Moreover, the LED current can be stabilized through the switching frequency as a function of input voltage only. Thus, the converter does not need current sensors, allowing cost reduction. The prototype assembled in laboratory was designed for a lamp of 54 W, operating in a frequency of approximately 153 kHz and presented an efficiency of 93%.

A step-up converter with switched capacitor using a small inductor in CCM to drive power leds

This paper presents the use of a DC-DC step-up converter with a switched capacitor to power light-emitting diodes (LEDs), presented in [11], with a input inductor operating in continuous conduction mode (CCM) and with dimming of LEDs. This converter has the advantage of stabilizing the LEDs current in open loop control through frequency modulation, which is obtained according to the input voltage. Therefore, the converter does not need current sensors, allowing cost reduction. The prototype assembled in laboratory was designed for a lamp of 54 W, operating in a frequency of approximately 88 kHz and presented a maximum efficiency of 95.5% and 93.9% in nominal conditions.

Low Cost Educational Tool to Trace the Curves PV Modules

This paper proposes a low-cost educational tool to trace the curves of PV modules. A MOSFET transistor was used to operate as a variable electronic load, which is driven by a simple RC circuit with a low cost objective. The data were captured with a basic digital oscilloscope, which allowed viewing captured curves and save the results for later analysis. The study of the photovoltaic cell electrical model allowed estimating the level of solar radiation, the maximum power point and the PV module temperature at the time of data capture. The theoretical analysis and experimental results of a KC65T module manufactured by Kyocera validated the proposal.

High gain qZS dc/dc converter with coupled inductor

This paper proposes a non-isolated qZS converter to feed a frequency inverter applied on a standalone photovoltaic tricycle. The converter uses the clipping voltage of the power switch to be added to the output voltage, which allows reducing the duty cycle values and increase the gain of the converter. Some converter topologies, based on high gain coupled inductors and voltage multiplier cells cause large current ripple in the input and voltage spike at the power switch. As a consequence the lifespan of the components and the converter efficiency are reduced. The proposed converter showed a low current ripple in the input and the power switch was submitted to lower voltage. High gain qZS dc-dc converters operation principle and analysis are shown, and verified by simulation and experimental results as well as a losses analysis.