| 摘要 |
PROBLEM TO BE SOLVED: To accurately measure the amount of AC power without using an LPF.SOLUTION: An average value calculation circuit 11 calculates an average power value in each period, and outputs the average value in a previous period from a latch circuit 12 for a current period. A comparator 14 is applied with the average value in the previous period at one input terminal, compares this average value with a signal applied to the other input terminal, and controls switching means 15 so as to output smaller one of the signals. An adder 16 subtracts the signal outputted from the switching means, from the signal applied to the other input terminal of the comparison means, and a previous value holding circuit 17 stores a signal obtained by the subtraction and outputs a signal obtained by the subtraction in the previous sampling. An adder 13 adds the signal from the previous value holding circuit 17 and a power value at the current sampling time and applies a result to the other input terminal of the comparator. Since the output of the switching circuit 15 becomes constant, an integrated value Wh2 obtained by an integrator 105 is linearly increased to avoid the occurrence of variation in period of a pulse train from a pulsing circuit 106. |
