PURPOSE: To dynamically control according to change by selectively using a digital power control sampling rate corrected for adjusting transfer function.

CONSTITUTION: The initial output parameter of a device to be controlled is sampled (102), and the other sampling of the output parameter is operated in a successively selected time (104). At least three samples, that is, the selected sample, the previous sample, and the sample to be selected are obtained. Next, a first difference between the selected sample of the output parameter and the previous sample is judged (106), and a second difference between the selected sample, and a sample to be selected is judged (110). In this case, when the second difference, the present difference is more than the first difference, the previous difference, and the first difference is substantially equal to zero (114), a maximum sampling rate FNS is set (118).