| 摘要 |
PURPOSE:To improve the efficiency of degaussing of an electromagnetic chuck and the like by a method wherein the voltage of the 1st capacitor, provided to a differential amplifier, is gradually reduced by FF and the charging speed of the 2nd capacitor, charged by FF, is gradually increased by comparing the 2nd capacitor voltage with the 1st capacitor voltage and the source whose plus and minus amplitude is alternately reduced gradually is used. CONSTITUTION:When a switch 10 is ON, an output (c) of a NOR circuit 11 becomes H through FFs 7, 8 and a thyristor T9 becomes conductive and a DC source is applied to a chuck 3 to magnetize it. When a switch 9 is ON for a certain period, an output Q of FF15 becomes H and an output Q' of FF17 becomes L and a coil 26 is excited and contacts K1, K2 are changed. The voltage of a capacitor C3 is reduced gradually and a capacitor C4 begins being charged. When an output of a differential amplifier is produced, a one-shot multiplexer 24 is triggered to discharge the capacitor C4 and the coil 26 is not excited and the contacts K1, K2 are changed. By repeating above procedure, the degaussing voltage is reduced gradually. |
