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Nobukazu TAKAI Yukihiro FUJIMURA
Sawtooth wave generator which has very steep down-slope and little amplitude and oscillation frequency error, is proposed. Because the down-slope is achieved by switching two triangular waves exclusively, the shape of the down-slope becomes very steep. The proposed method realizes not only the steep down-slope but also less amplitude error and less oscillation frequency error compared with conventional method. Spectre simulations are performed by using 0.18 µm CMOS process and transient simulation results show the proposed circuit has quite less amplitude and frequency error for 5 MHz oscillation compared with the conventional method.
Ibuki MORI Yoshihisa YAMADA Santhos A. WIBOWO Masashi KONO Haruo KOBAYASHI Yukihiro FUJIMURA Nobukazu TAKAI Toshio SUGIYAMA Isao FUKAI Norihisa ONISHI Ichiro TAKEDA Jun-ichi MATSUDA
This paper proposes spread-spectrum clock modulation algorithms for EMI reduction in digitally-controlled DC-DC converters. In switching regulators using PWM, switching noise and harmonic noise concentrated in a narrow spectrum around the switching frequency can cause severe EMI. Spread-spectrum clock modulation can be used to minimize EMI. In conventional switching regulators using analog control it is very difficult to realize complex spread-spectrum clocking, however this paper shows that it is relatively easy to implement spread-spectrum EMI-reduction using digital control. The proposed algorithm was verified using a power converter simulator (SCAT).