Low-dropout voltage regulator for stabilizing LEDs drives in dimmable group current sinks
The well-developed constant current sink (CCSK) supplied from a constant voltage source (CVS) has been widely qualified for driving group-parallel strings of power LEDs. This approach takes advantage of current balancing between multiple parallel strings of the LEDs for producing uniform luminous output. However, the drain-to-source voltage vds of the driver MOSFET may move into triode region when the sink current increases since the change of the forward voltage of the string LEDs and the voltage drop on source resistor cannot be compensated with the CVS. In this paper, a low-dropout controlled voltage regulator (LDCVR) is proposed to adaptively well bias the string LEDs and to prevent the sink MOSFETs from working in triode region when dimming for high luminous needs. An experimental to design approach is adopted in design considerations to facilitate the control means between CCSKs and LDCVR so as to stabilize the luminous output uniform with low conduction loss in the sink MOSFETs.
Reliability study of LED driver - A case study of black box testing
Abstract A method to evaluate the reliability of the Integrated Circuit without knowing the details of the internal circuit is developed. This method is called Pseudo Black Box testing because the basic knowledge of circuit theory is needed. In this paper, this black box testing is applied to the reliability study of a commercial LED driver and the circuit degradation model is built. The possible failure mechanisms of the LED driver are proposed and verified through failure analysis.
Students as promoters of rural extension in aquaculture in the Marajó archipelago, Pará, Brazil
Aquaculture is the creation of aquatic organisms. An expanding activity, being of great importance its approach in rural extension. Thus, the objective of this study was to analyze the contribution of extension activities in aquaculture in the professional training of students in Marajó, Amazon, Brazil. The project “Technology transfer through training and technical assistance for tambaqui breeders, Colossoma macropomum, in the archipelago of Marajó/PA” was developed by 10 technician and under graduate students from rural education course and the technical course in aquaculture from the Federal Institute of Education, Science and Technology of Pará (IFPA) Campus Breves, in the city of Curralinho. They participated in the stages of data collection in aquaculture enterprises, training for producers and monitoring of aquaculture production, acting as researchers, instructors and extension workers, respectively. The duration of the project was from August 2019 to March 2020. At the end of the project, a questionnaire was applied to the students involved. The results showed that the aquaculture extension activities developed were relevant and significant, for the construction of knowledge in a mutual way between those involved (students and aquaculture producers). The acquired experiences will substantiate and subsidize the professional practice of these students in a concrete and effective way. In conclusion, the extension project represents an excellent tool in the teaching-learning process for students.