| 摘要 |
PURPOSE:To execute normal detection of a DC power supply by providing a gain limiter for limiting a frequency near a double-wave frequency to a band- pass filter part of a selective amplifier. CONSTITUTION:The output voltage of a detection winding 43 increases excessively if excessive DC current flows to the input windings of troidal cores 40a, 40b and, therefore, the selective amplifier 5 which selectively amplifies the double-wave component among the same limits the frequency near the frequency of the double-wave component by the gain limiter in the band-pass filter of a twin T type, thereby suppressing the inversion of a phase error at the time of the phase detection of the double-waves from the detection winding 43 by a phase detector 6. The negative feedback to a feedback winding 44 is so prevented as not to become a positive feedback. The dynamic range of the input/output characteristics of the current detector are thereby widely maintained. The excess input at the frequency near the double-wave frequency is limited and the negative feedback operation is, therefore, maintained at all times and the normal detection of the DC current is realized. |
