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Output Voltage Increase of a Series Resonant DC-DC Converter
Osamu Matsuo,Hirofumi Matsuo,Yoichi Ishizuka,Koji Kuwahara,Hiroyuki Ota,Katsuhiro Izumi 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
It has been considered that the series resonant converter takes the maximums of the output voltage in the resonant frequency. However, in practice, the series resonant converter takes the maximums of the output voltage that appears in the lower frequency band compared with the resonant frequency. We analyzed the output voltage characteristics of a series resonant converter circuit when the switching frequency is lower than the resonant frequency including the transformer magnetizing inductance from a transformer. As a result, it was confirmed that for the series resonant converter, the output voltage takes maximum at a lower frequency than the resonant frequency, and the output voltage is larger than the input voltage; that is, the converter has the output boost characteristics, and consequently, this converter can be used when the input voltage is varied widely. In addition, the switching frequency is clarified when the output voltage takes the maximum according to the load resistance and magnetizing inductance.
Mutsuyoshi Asano,Hirofumi Matsuo,Haruya Mae,Fujio Kurokawa,Masahiro Sasaki 전력전자학회 1995 ICPE(ISPE)논문집 Vol.1995 No.10
This paper deals with the analysis of the output characteristics of the new digitally controlled dc-dc converter with auxiliary switches, which are used to prevent the extremely lowering of the switching frequency caused by the decrease of the load current and/or the increase of the input voltage. This dc-dc converter with auxiliary switches has two major operation modes; that is, the frequency control and on-time control modes. Taking account of the forward voltage drops and loss resistances of the main switches, auxiliary switches and diodes, and the winding series resistances of the transformer, the detailed circuit operation and the output characteristics are analysed. As a result of analysis, it is clarified that the superior regulation characteristics of the output voltage is obtained, and that the power efficiency of the digitally controlled dc-dc converter with auxiliary switches is improved in the relatively light load region, compared with that of the conventional one with analog control circuit.
Feedback System Using the PWM (Pulse Width Modulation) Power Amplifier with Huge Bandwidth
Shigeaki Wachi,Hirofumi Matsuo 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
A feedback system using a PWM power amplifier has time delay and nonlinearity problems. In this paper, we discuss the time delay problem that causes narrowing bandwidth of the feedback system, and the nonlinearity problem that causes the instability of the feedback system. And, we propose the solutions for both of them for the purpose of expanding the bandwidth. For the time delay problem, we propose an improved PWM method where we lade its information both on the rising edge and the falling edge. For the nonlinearity problem, we propose the PWM gain controller to cancel the nonlinearity.
Analysis of the Radiation Noise and Efficiency Characteristics in a Quasi-resonant Converter
Hironobu SHIROYAMA,Hirofumi MATSUO,Yoichi ISHIZUKA 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
In this paper, the radiation noise and efficiency of the quasi-resonant converter are analyzed. A quasiresonant converter using the flyback topology can realize the soft switching with simpler circuit. However, switching devices with the high withstand voltage is necessary to achieve the complete ZVS and it causes the low power efficiency because a switching device with the high withstand voltage has the high on-voltage. On the other hand, the swithching device with the low withstand voltage and then the low on-resistance can be used with the non-ZVS. Therefore the performance characteristics such as the efficiency and radiation noise are analyzed on the quasiresonant converter with the ZVS and the non-ZVS. As a result, it is clarified that the low radiation noise and high power efficiency are achieved with the non-ZVS.
Masahiro Yoneda,Miwa Yamada,Nao Suzuki,Rie Uemura,Akie Fujimoto,Yosuke Masuo,Hirofumi Fukuchi,Hiromitsu Morita,Kazuhiko Yamada,Tadayuki Matsuo,Ayako Ishii,Chihiro Koga,Takao Hirofuji 대한예방치과학회 2015 International Journal of Clinical Preventive Denti Vol.11 No.1
Objective: Fukuoka Dental College established a satellite clinic, the Center for Oral Diseases (COD), in December 2011. In this study, we analyzed halitosis patients and the role of dental hygienists. Methods: Approximately 70% of the patients were female and most were in their 40s. We analyzed the possible causes of halitosis. Results: More than half of the patients exhibited a thick tongue coating. Low salivary flow was present in 23.6% of males and in 39.4% of females. Pocket depth ≥6 mm was found in 44.2% of males and in 16.7% of females. We also analyzed treatment provided after breath odor measurement. Most of the patients with physiological halitosis and pseudohalitosis did not receive further treatment, but some were treated at the COD with scaling and professional tooth cleaning. Many of the patients with genuine halitosis received dental treatment at the COD. We referred patients from other clinics and from distant locations to their local doctors for treatment. Conclusion: Halitosis had various causes, and the role of dental hygienists, including scaling, root planing, and tooth brushing instruction, are important in decreasing breath odor. Dental hygienists play an important role in communication with halitosis patients.