Title:
PULSE WIDTH MODULATION CIRCUIT
Document Type and Number:
Japanese Patent JP3952970
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To reduce a noise peak value without enlarging a circuital size of a semiconductor integrated circuit, by dispersing an oscillating frequency with a fixed frequency span.
SOLUTION: A pulse width modulation circuit 10 includes a triangular wave oscillator 1 for generating a triangular wave signal voltage VOSC with a fixed magnitude through charge and discharge of a capacitor, a comparator 2 for generating a pulse width modulation signal by comparing the triangular signal generated from the triangular wave oscillator 1 with an error voltage signal VFB as an output from an output voltage feed-back circuit 11, and a modulation signal generator 3. The modulation signal generator 3 includes a reference current generating circuit and a pseudo random number generating circuit. By switching discretely the magnitude of charging and discharging current of the capacitor at the triangular oscillator 1 with timing synchronizing with the triangular signal, the oscillation frequency of the triangular signal voltage VOSC is spread with a fixed transition without adding a new resistor.
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Inventors:
Yasushi Katayama
Satoshi Sugawara
Satoshi Sugawara
Application Number:
JP2003057703A
Publication Date:
August 01, 2007
Filing Date:
March 04, 2003
Export Citation:
Assignee:
Fuji Electric Device Technology Co., Ltd.
International Classes:
H02M3/155; H03K7/08; H03K4/06; (IPC1-7): H03K7/08; H02M3/155; H03K4/06
Domestic Patent References:
| JP7264849A | ||||
| JP4058756A | ||||
| JP5327427A | ||||
| JP7245942A | ||||
| JP2002252970A | ||||
| JP2003324944A |
Attorney, Agent or Firm:
Takeshi Hattori