| 摘要 |
PURPOSE:To widen a dynamic range by inputting the output of a constant-multiple-voltage generating circuit to a comparator through a Miller integration circuit, opening and closing a switch by an output signal of pulse-width modulation, and leading in a signal proportional to current consumption. CONSTITUTION:A current transformer 11 performs conversion to the signal proportional to the current consumption of a feeder, and a pulse-width modulation type time-series multiplying circuit 12 inputs the signal under the on/off control of a switch circuit 124 and supplies it to an LPF13 with an integration function. A voltage obtained by integration is converted by a voltage-frequency converting circuit 14 into a pulse signal, which is counted to integrate the current. The circuit 12 is equipped with the constant-multipled-voltage generating circuit 121 which generates a constant multiple voltage, Miller integration circuit 122, and comparator A4 which compares and feed the output of the circuit 122 back to the circuit 122 and imposes pulse-width modulation upon the constant multiple voltage, and the circuit 124 is turned on and off according to the output signal of the comparator and its inverted signal. Consequently, the current is integrated with high precision even at the time of less loading and against a distortion wave. |
