| 摘要 |
PURPOSE:To prevent the current detection signal of an AC servo motor from being affected by a DC offset portion by connecting a circuit for cancelling the influence of a residual magnetic flux in a core with the output side of a magnetic conversion element. CONSTITUTION:A change of the magnetic flux quantity of a core 1 caused by a change of electric current flowing through the wire wound round said core 1 is converted into an electric signal by a Hall effect element 2 and outputted as a current detection signal S1. Said current detection signal S1 is caused to pass through first and second half-wave rectifier circuits 5, 6 with polarities reversed to each other to obtain respective half-wave rectification signals S2, S3 where only one of positive and negative signals is rectified. Then, said signals S2, S3 are added and smoothed so that a DC offset portion V may be taken out. Said added and smoothed signal S4 and the current detection signal S1 are inputted to an amplifier circuit 7 to obtain a current detection signal where the DC offset portion is cancelled. |
