| 摘要 |
PURPOSE:To suppress output voltage rise by inserting a dummy resistor, when a chopper control step-down power supply utilized in railroad enters into a load current zone where the voltage of an output filter capacitor starts to rise and the output voltage exceeds a predetermined target level, thereby decreasing the average current level with time while simultaneously switching the chopper control operation from continuous operation to intermittent operation. CONSTITUTION:A DC current collected from a DC stringing 1 through a pantograph 2 is converted through a chopper 6 into a rectangular wave which is then fed through a reactor 10 to a load 15. The chopper 6 normally compares a detected output voltage 9 from the chopper with a set output voltage 17 in a comparing circuit 18 and controls a gate circuit 19. Upon abrupt increase of output voltage due to abrupt load drop, the chopper is stopped by a signal fed from a judging circuit 22 through a voltage detector 21 thus preventing voltage rise. Upon output voltage rise due to decrease of load current, conduction rate of a transistor 14 is decreased with time and current flow into a dummy resistor 13 is decreased thus preventing heating of the resistor. |
