Patent ID: 7589432

Claim:
A switching device comprising: a switching element that turns on/off in response to a drive signal which is set to control a controlled variable of a controlled system at a desired amount thereof; control means that variably controls the switching element based on the drive signal; and setting means that sets the drive signal on the basis of a desired variable duty to control the controlled variable, wherein i) the drive signal is set by repeating a basic interval pattern comprising a period time T wherein the basic interval pattern consists of a plurality of intervals between leading edges Th or falling edges Tl of drive pulses and wherein all the intervals comprise different lengths to each other, so that overlaps in a frequency spectrum, among switching frequencies of both ON and OFF operations of the drive pulses are avoided even when the desired variable duty is changed for controlling the controlled variable, and ii) wherein, among a plurality of basic interval patterns which are different to each other and which are set so that the overlaps are avoided, the basic interval pattern is selectively switched in response to the desired variable duty.