| 摘要 |
PURPOSE:To improve the safety and reliability of a DC power unit even when the capacity of the constant-voltage element of a surge voltage absorption circuit is set larger or even when the constant-voltage element short-circuits due to a surge voltage. CONSTITUTION:The series circuit of capacitors 8 and 9 and parallel circuit of the series circuit and a varister ZV act on and absorb a normal-mode surge voltage applied across the lines H and N of an AC power source 1 and the series circuit of the capacitor 8 or 9 and a constant-voltage element 10 acts on and absorbs a common-mode surge voltage applied across the line H or N and a frame ground FG. In both cases, the withstand voltage and power capacity can be increased as compared with such a case that the element 10 or varister ZV independently acts and, at the same time, an occurrence of firing or an electrical shock can be eliminated even when the element is short- circuited, since no leakage current flows into the frame ground FG. |
