| 摘要 |
PURPOSE:To suppress the adverse influence to the exterior such as a noise defect by providing an equivalent disturbing current detector, and varying the modulating frequency when the output exceed the prescribed value. CONSTITUTION:An AC input current detected by a curretn transformer CT is also input to an equivalent disturbing current detector EQ, and is compared by a Schmitt circuit SCH with the allowable value of the equivalent disturbing current. As a result, a relay circuit RY is operated while the Schmitt circuit generates an output to switch the modulating frequency. In other words, if the disturbing current exceeds the alllowable value, the output of the second triangular wave generator TRG2 having high modulating frequency is selected. Thus, the band of the harmonics generated in the input current is shifted to a high frequency range to reduce the disturbing current. |
