The application of the high gain boost DC-DC converter is gaining more attention due to an increasingly wide range of applications for sustainable green energy solutions, as well as other high voltage applications. In this study, a modified high gain quadratic boost converter is proposed using a single switch. The proposed topology is a member of the family of the non-isolated category with a common ground feature and can operate in a wide range of duty ratios, and is able to provide the required voltage gain. In this proposed circuit configuration, a dual voltage boost cell was formed by incorporating two capacitors in series with two inductors of a conventional quadratic boost converter. Additionally, a capacitor was integrated with a second voltage boost cell. This special configuration increases the voltage gain as well as reduces the voltage stress across the switch. To show its feasibility, a 200-W prototype setup with 48 V input and 400 V output was designed, and the required PWM signal was fed from the microcontroller unit. A detailed analysis of the design parameters and losses are formulated and are shown in this paper. The simulation was performed in SIMPLIS software, and the experimental results agreed with the obtained output voltage gain. The proposed topology showed a peak efficiency of 94.5% at 150-W output power after considering the power losses in all the components of the PCB.
Graphene heat-dissipating coating (GNHC) of 0.6 wt % GN concentration is utilized to promote the cooling performance of automotive light-emitting diode (LED) lamps. Three cases are studied as follows: Case 0 is the original automotive LED lamp as the baseline. Case 1 is to apply GNHC to reduce the thermal resistance of the junction surfaces between the components of automotive LED lamps. The aluminum fin radiator of Case 1 is further coated with GNHC on the surface that becomes Case 2. The spectrum, illuminance, power consumption, and surface temperature are measured at different ambient temperatures (Ta) to fully evaluate the feasibility of applying GNHC to improve cooling performance and the impacts on the related characteristics of automotive LED lamps. The results show that the maximum illuminance efficacy of Case 1 and Case 2 with high beam, irradiation angle of 0 degrees, and Ta of 80 °C is 11.03% and 8.70% higher than that of Case 0, respectively. The minimum temperature difference of heat dissipation path of Case 1 and Case 2 with high beam, irradiation angle of 90 degrees, and Ta of 80 °C is 6.41% and 5.33% lower than that of Case 0, respectively, indicating GNHC as a promising coating material for improving the cooling performance of automotive LED lamps.
In this study, the authors propose a method for evaluating the influence of ambient temperature (Ta) on the optical characteristics and power consumption of a LED lamp used for the automotive headlamp, which helps the designer to figure out the acceptable range of the ambient temperature for the LED lamps to work well in the practical case. The LED lamp was fixed on the test holder and placed in a fixed position in the air circulation temperature control oven to measure the illuminance, spectrum in three different directions, and power consumption under various Ta. The experimental results indicate that Ta has little effect on the correlated color temperature (CCT), chromaticity coordinates, and angular distribution of the emitting light. In contrast, Ta has a significant effect on the lamp’s resistance, thus affecting illuminance and power consumption. When the Ta increased from 30 °C to 60 °C, the illuminance of the low beam and high beam decreased on average by 16.6% and 21.7%, respectively, while the power consumption of the low beam and high beam decreased on average by 21.4% and 22.2%, respectively. The drop in the luminous flux output indicates the probability of originally qualified automotive LED headlamps becoming unqualified in high Ta.
QR code as a technology enhanced learning tool is prevailing not only in daily life, but also in education settings. The present study aims to explore the usage of QR code as a social medium in searching and learning profession knowledge of auto-repairing. The experiment contains 3 learning courses and 3 lessons for 155 students. Moreover, based on the theory of planned behavior, questionnaires are designed for students to fill out. A total of 153 copies are valid questionnaires. Confirmatory factor analysis is conducted while structural equation model is established. Research outcome indicates that Internet cognitive capacity correlates with hedonic and epistemic values, which reflect directly in learning attitudes of auto-repairing students using QR code. As sustaining intent of usage for QR code has to do with learning attitude of students, the study suggests that instructors should decrease complex contents of QR code before providing them to students for learning.
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