Low harmonic design of a buck converter with triangular wave control for frequency hopping

This paper presents a random frequency hopping with triangular ramp control for harmonic reductions in a dc-dc converter. The relationship between “the sawtooth and triangular ramp signals” and the inductor current is analyzed, and the two ramp signals are implemented into the converter to compare the variation of output voltage. When the switching frequency hops, using triangular ramp keeps the small variation of the average inductor current. A prototype buck converter implemented 0.35μm 2P4M CMOS process verifies the effectiveness of the proposed method. Compared with eight and single switching frequencies, the proposed frequency hopping circuit can suppress the output harmonics by 21.9 dB from simulation results. Without increasing the output inductance or capacitance, the harmonics can be decreased dramatically.