Patent ID: 7245106

Claim:
A controller of a pulse width modulation signal-driven device, comprising: 1) an instruction input for inputting an instruction of operating the pulse width modulation signal-driven device; 2) a control section for generating, with the instruction from the instruction input, a control clock which operates the pulse width modulation signal-driven device; 3) a frequency modulator for frequency-modulating the control clock which is an output of the control section, to thereby give to the control clock a frequency variation in a predetermined frequency range; 4) a frequency varier for generating a modulation signal to be inputted to the frequency modulator, the frequency varier including: i) a first signal generator for setting a range of diffusing a switching noise in a frequency range, the switching noise being caused by a switching element, and ii) a unit for shifting a frequency band of the switching noise by giving a predetermined offset voltage to a first output voltage of the first signal generator; and 5) a first switching member for driving the switching element which flows a predetermined drive current to the pulse width modulation signal-driven device based on the frequency-modulated control clock, width wherein the frequency varier includes a plurality of the first signal generators having different amplitudes and offset voltages, and the unit of the frequency varier includes: a) a second signal generator for making an instruction for a switching, and b) a second switching member which switches the first output voltages of the plurality of the first signal generators at a predetermined period based on second output voltage of the second signal generator, to thereby cause the predetermined offset voltage.