A discretized proportional base driver for Silicon Carbide Bipolar Junction Transistors

Silicon Carbide Bipolar Junction Transistors require a continuous base current in the on-state. This base current is usually made constant and is corresponding to the maximum collector current and maximum junction temperature that is foreseen in a certain application. In this paper, a discretized proportional base driver is proposed which will reduce, for the right application, the steady-state power consumption of the base driver. The operation of the proposed base driver has been verified experimentally, driving a 1200V/40A SiC BJT in a DC-DC boost converter. In order to determine the potential reduction of the power consumption of the base driver, a case with a dc-dc converter in an ideal electric vehicle driving the new European drive cycle has been investigated. It is found that the steady-state power consumption of the base driver can be reduced by approximately 63 %. The total reduction of the driver consumption is 2816 J during the drive cycle, which is slightly more than the total on-state losses for the SiC BJTs used in the converter. © 2013 IEEE.

Statistics anxiety, state anxiety during an examination, and academic achievement.

BACKGROUND: A large proportion of students identify statistics courses as the most anxiety-inducing courses in their curriculum. Many students feel impaired by feelings of state anxiety in the examination and therefore probably show lower achievements. AIMS: The study investigates how statistics anxiety, attitudes (e.g., interest, mathematical self-concept) and trait anxiety, as a general disposition to anxiety, influence experiences of anxiety as well as achievement in an examination. SAMPLE: Participants were 284 undergraduate psychology students, 225 females and 59 males. METHODS: Two weeks prior to the examination, participants completed a demographic questionnaire and measures of the STARS, the STAI, self-concept in mathematics, and interest in statistics. At the beginning of the statistics examination, students assessed their present state anxiety by the KUSTA scale. After 25 min, all examination participants gave another assessment of their anxiety at that moment. Students' examination scores were recorded. Structural equation modelling techniques were used to test relationships between the variables in a multivariate context. RESULTS: Statistics anxiety was the only variable related to state anxiety in the examination. Via state anxiety experienced before and during the examination, statistics anxiety had a negative influence on achievement. However, statistics anxiety also had a direct positive influence on achievement. This result may be explained by students' motivational goals in the specific educational setting. CONCLUSIONS: The results provide insight into the relationship between students' attitudes, dispositions, experiences of anxiety in the examination, and academic achievement, and give recommendations to instructors on how to support students prior to and in the examination.

Switch mode constant current LED Driver with high efficiency, high precision and wide dimming ratio

A high efficiency hard switching constant current LED driver is presented with high overall efficiency, high current precision, high LED efficacy, flicker-free and wide constant current dimming ratio. The high stable lighting source provides the best solution for office light, reading light and LCD backlight. © 2013 IEEE.

A discretized proportional base driver for silicon carbide bipolar junction transistors

Silicon carbide (SiC) bipolar junction transistors (BJTs) require a continuous base current in the on-state. This base current is usually made constant and is corresponding to the maximum collector current and maximum junction temperature that is foreseen in a certain application. In this paper, a discretized proportional base driver is proposed which will reduce, for the right application, the steady-state power consumption of the base driver. The operation of the proposed base driver has been verified experimentally, driving a 1200-V/40-A SiC BJT in a dc-dc boost converter. In order to determine the potential reduction of the power consumption of the base driver, a case with a dc-dc converter in an ideal electric vehicle driving the new European drive cycle has been investigated. It is found that the steady-state power consumption of the base driver can be reduced by approximately 60%. The total reduction of the driver consumption is 3459 J during the drive cycle, which is slightly more than the total on-state losses for the SiC BJTs used in the converter. © 2013 IEEE.