| 摘要 |
PURPOSE:To enable the use of an electrolytic capacitor within a high-temperature range about 100 deg.C by stabilizing an output voltage of a switching source thermally by arranging a positive characteristic thermistor having a resistance value under a specified value at room temperature near an electrolytic capacitor so as to connect said thermistor with said electrolytic capacitor in series. CONSTITUTION:To a semiconductor ceramic mainly consisting of BaTiO3, a Curie-point shifting material such as CaTiO3, MgTiO3 SrTiO3, and PbTiO3 each of 0.1 to 10% and BaSnO3 and SrSnO3 each of 0.01 to 10% for reducing its resistance are added. Then, a positive characteristic thermistor whose resistance value is 1OMEGA or under at room temperature and up to a required temperature is calcined without losing the PTC characteristics. This positive characteristic thermistor fabricated into a cylindrical form is put, surrounding an electrolytic capacitor of a switching source and is connected with that capacitor in series. If the temperature of the electrolytic capacitor increases according to an increase in environmental temperature or ripple currents, the temperature of the positive characteristic thermistor arranged near that capacitor increases and when its temperature reaches the Curie point or over, the resistance value increases remarkably to restrain the ripple currents and to accordingly prevent thermal breakdown of the electrolytic capacitor. |
