Controller of pulse width modulation signal-driven device, and method of reducing noise of the device

1. 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.

2. The controller of the pulse width modulation signal-driven device as claimed in claim 1 , wherein

the pulse width modulation signal-driven device is a stepping motor.

3. The controller of the pulse width modulation signal-driven device as claimed in claim 1 , wherein

the pulse width modulation signal-driven device is a DC-DC converter.

4. 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,

wherein

the unit of the frequency varier includes:

a) a second signal generator, and

b) an adder for adding a second output voltage of the second signal generator to the first output voltage of the first signal generator, to thereby cause the predetermined offset voltage,

the frequency varier includes:

i) a third signal generator for changing an amplitude of an output voltage which is the addition by using the adder, and

ii) a synchronizer for synchronizing the second output voltage of the second signal generator with a third output voltage of the third signal generator,

the controller further comprises a receiving frequency sensor,

with the receiving frequency sensor, the second signal generator senses a receiving frequency of a receiver in a vicinity of the first switching member, and changes the offset voltage corresponding to the receiving frequency, and

with the receiving frequency sensor, the third signal generator senses the receiving frequency of the receiver in the vicinity of the first switching member, and changes corresponding to the receiving frequency the amplitude of the output voltage which is the addition by using the adder.

5. The controller of the pulse width modulation signal-driven device as claimed in claim 4 , wherein

the first output voltage of the first signal generator is a triangle wave having a predetermined amplitude, and

the second output voltage of the second signal generator and the third output voltage of the third signal generator each are a rectangular wave having a predetermined amplitude.

6. A method of controlling a pulse width modulation signal-driven device, comprising:

1) inputting an instruction of operating the pulse width modulation signal-driven device;

2) generating, with the thus inputted instruction, a control clock which operates the pulse width modulation signal-driven device;

3) frequency-modulating the thus generated control clock, to thereby give to the control clock a frequency variation in a predetermined frequency range;

4) generating a modulation signal to be inputted to a frequency modulator for the frequency-modulating, the generating of the modulation signal including:

i) first signal generating for setting a range of diffusing a switching noise in a frequency range, the switching noise being caused by a switching element, and

ii) shifting a frequency band of the switching noise by giving a predetermined offset voltage to first output voltage generated by the first signal generating; and

5) 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,

wherein

the generating of the modulation signal includes a plurality of the first signal generatings causing different amplitudes and offset voltages, and

the shifting of the frequency band of the switching noise includes:

a) second signal generating for making an instruction for a switching, and

b) second switching which switches the first output voltages of the plurality of the first signal generatings at a predetermined period based on a second output voltage of the second signal generating, to thereby cause the predetermined offset voltage.

7. A controller of a pulse width modulation signal-driven device, comprising:

1) inputting means for inputting an instruction of operating the pulse width modulation signal-driven device;

2) controlling means for generating, with the instruction from the inputting means, a control clock which operates the pulse width modulation signal-driven device;

3) frequency-modulating means for frequency-modulating the control clock which is an output of the controlling means, to thereby give to the control clock a frequency variation in a predetermined frequency range;

4) frequency-varying means for generating a modulation signal to be inputted to the frequency-modulating means, the frequency-varying means including:

i) first signal generating means for setting a range of diffusing a switching noise in a frequency range, the switching noise being caused by a switching element, and

ii) shifting means for shifting a frequency band of the switching noise by giving a predetermined offset voltage to a first output voltage of the first signal generating means; and

5) first switching means 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,

wherein

the frequency varying means includes a plurality of the first signal generating means having different amplitudes and first offset voltages, and

the shifting means of the frequency varying means includes:

a) second signal generating means for making an instruction for a switching, and

b) second switching means which switches the first output voltages of the plurality of the first signal generating means at a predetermined period based on a second output voltage of the second signal generating means, to thereby cause the predetermined offset voltage.