| 摘要 |
PURPOSE:To fix an unbalance detection level irrespective of the amplitude of load current by detecting the ripple of the load current and by operating a comparison circuit according to the ratio of the ripple to the load current determined by the partial voltage ratio between two partial voltage resistors. CONSTITUTION:The load current is detected by a current transformer 2 and rectified by a rectifying circuit 3. When the load current falls into unbalance or the like, an output waveform appearing between a pair of output terminals 3a and 3b of the rectifying circuit 3 turns to be a ripple waveform containing a ripple portion V01 at a waveform value V1. Therefore, a capacitor 4 is charged at the waveform value V1. Next, in the root part of the output waveform, a voltage corresponding to the ripple portion V01 is to be discharge through two partial voltage resistors 6 and 7 because of the presence of a diode 5. And, the ratio of the ripple of the load current becomes larger than a fixed value determined by the partial voltage ratio between the partial-voltage resistors 6 and 7, and when the ratio becomes larger than a prescribed voltage value, the comparison circuit 8 operates to deliver an output. By such a constitution, the unbalance detection level can be fixed irrespective of the amplitude of the load current. |
