High-efficiency Bidirectional Buck-Boost Converter for Residential Energy Storage System

This paper proposes a bidirectional dc-dc converter for residential micro-grid applications. The proposed converter can operate over an input voltage range that overlaps the output voltage range. This converter uses two snubber capacitors to reduce the switch turn-off losses, a dc-blocking capacitor to reduce the input/output filter size, and a 1:1 transformer to reduce core loss. The windings of the transformer are connected in parallel and in reverse-coupled configuration to suppress magnetic flux swing in the core. Zero-voltage turn-on of the switch is achieved by operating the converter in discontinuous conduction mode. The experimental converter was designed to operate at a switching frequency of 40-210 kHz, an input voltage of 48 V, an output voltage of 36-60 V, and an output power of 50-500 W. The power conversion efficiency for boost conversion to 60 V was >= 98.3% in the entire power range. The efficiency for buck conversion to 36 V was >= 98.4% in the entire power range. The output voltage ripple at full load was <3.59 V-p.p for boost conversion (60 V) and 1.35 V-p.p for buck conversion (36 V) with the reduced input/output filter. The experimental results indicate that the proposed converter is well-suited to smart-grid energy storage systems that require high efficiency, small size, and overlapping input and output voltage ranges.11Ysciescopu

Miniature DC-DC Boost Converter for Driving Display Panel of Notebook Computer

This paper proposes a miniature DC-DC boost converter to drive the display panel of a notebook computer. To reduce the size of the circuit, the converter was designed to operate at a switching frequency of 1 MHz. The power conversion efficiency improved using a passive snubber circuit that consisted of one inductor, two capacitors, and two diodes; it reduced the switching losses by lowering the voltage stress of the switch and increased the voltage gain using charge pumping operations. An experimental converter was fabricated at 2.5 cm &times; 1 cm size using small components, and tested at input voltage 5 V &le; VIN &le; 17.5 V and output current 30 mA &le; IO &le; 150 mA. Compared to existing boost converters, the proposed converter had ~7.8% higher power conversion efficiency over the entire range of VIN and IO, only ~50% as much voltage stress of the switch and diodes, and a much lower switch temperature TSW = 49.5 &deg;C. These results indicate that the proposed converter is a strong candidate for driving the display panel of a notebook computer

High-Efficiency Asymmetric Forward-Flyback Converter for Wide Output Power Range

This paper proposes an asymmetric forward-flyback dc-dc converter that has high power-conversion efficiency ��e over a wide output power range. To solve the problem of ringing in the voltage of the rectifier diodes and the problem of duty loss in the conventional asymmetric half-bridge (AHB) converter, the proposed converter uses a voltage doubler structure with a forward inductor Lf in the second stage, instead of using the transformer leakage inductance, to control output current. Lf resonates with the capacitors in the voltage doubler to achieve a zero-voltage turn-on of switches and a zero-current turn-off of diodes for a wide output power range. The proposed converter could operate at a wider input voltage range than the other AHB converters. ��e was measured as 95.9% at output power Po = 100 W and as 90% at Po = 10 W, when the converter was operated at input voltage 390 V, output voltage 142 V, and switching frequency 100 kHz. ? 2016 IEEE.1133Nsciescopu

Off-Time Control of LLC Resonant Half-Bridge Converter to Prevent Audible Noise Generation Under a Light-Load Condition

This paper presents a control method that can prevent audible noise generation in an LLC resonant half-bridge dc-dc converter under a light-load condition, while achieving the same input voltage range and power-conversion efficiency eta(e) as the burst-control method that generates an audible noise. The proposed method reduces switching and conduction losses at light load by skipping several pairs of switch-control pulses, while varying the switching frequency less than the normal-control method does. This skip-control method enables the LLC resonant converter to have a large magnetizing inductance, and to have high eta(e) over a wide range of load variation. At an input voltage of 385 V, an output voltage of 24 V, and a resonant frequency of 180 kHz, the proposed method achieved eta(e) >= 85.46% for an output power range of 7.2-360 W; the highest eta(e) was 96.08% at P-o = 336 W.11Nsciescopu

Stimulation of Vibrio vulnificus Pyruvate Kinase in the Presence of Glucose to Cope With H2O2 Stress Generated by Its Competitors

The bacterial phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) regulates a variety of cellular processes in addition to catalyzing the coupled transport and phosphorylation of carbohydrates. We recently reported that, in the presence of glucose, HPr of the PTS is dephosphorylated and interacts with pyruvate kinase A (PykA) catalyzing the conversion of PEP to pyruvate in Vibrio vulnificus. Here, we show that this interaction enables V. vulnificus to survive H2O2 stress by increasing pyruvate production. A pykA deletion mutant was more susceptible to H2O2 stress than wild-type V. vulnificus without any decrease in the expression level of catalase, and this sensitivity was rescued by the addition of pyruvate. The H2O2 sensitivity difference between wild-type and pykA mutant strains becomes more apparent in the presence of glucose. Fungi isolated from the natural habitat of V. vulnificus retarded the growth of the pykA mutant more severely than the wild-type strain in the presence of glucose by glucose oxidase-dependent generation of H2O2. These data suggest that V. vulnificus has evolved to resist the killing action of its fungal competitors by increasing pyruvate production in the presence of glucose

Image_1_Stimulation of Vibrio vulnificus Pyruvate Kinase in the Presence of Glucose to Cope With H2O2 Stress Generated by Its Competitors.pdf

<p>The bacterial phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) regulates a variety of cellular processes in addition to catalyzing the coupled transport and phosphorylation of carbohydrates. We recently reported that, in the presence of glucose, HPr of the PTS is dephosphorylated and interacts with pyruvate kinase A (PykA) catalyzing the conversion of PEP to pyruvate in Vibrio vulnificus. Here, we show that this interaction enables V. vulnificus to survive H₂O₂ stress by increasing pyruvate production. A pykA deletion mutant was more susceptible to H₂O₂ stress than wild-type V. vulnificus without any decrease in the expression level of catalase, and this sensitivity was rescued by the addition of pyruvate. The H₂O₂ sensitivity difference between wild-type and pykA mutant strains becomes more apparent in the presence of glucose. Fungi isolated from the natural habitat of V. vulnificus retarded the growth of the pykA mutant more severely than the wild-type strain in the presence of glucose by glucose oxidase-dependent generation of H₂O₂. These data suggest that V. vulnificus has evolved to resist the killing action of its fungal competitors by increasing pyruvate production in the presence of glucose.</p