Low Spur and Harmonic Buck Converter with Triangular-Wave Control

• Main Authors: CHUAN-FENG WU, 巫權峰
• Other Authors: Yu-Kang Lo
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/92323203554217236761

碩士 === 國立臺灣科技大學 === 電子工程系 === 101 === This thesis introduces a random frequency hopping with triangle-wave control to implement a buck converter with spur and harmonic reduction. The sawtooth-wave and triangle-wave are analyzed the relation with the inductor current, and are integrated into the converter to compare the variation of output voltage further. A random frequency hopping scheme is used to reduce harmonics, and the frequency spectrum of the output voltage is compared with eight and single switching frequencies. The power MOSFET are integrated into the chip of spur reduction design of a buck converter for decreasing the PCB area and cost. The chip is implemented with TSMC 0.35 μm 2P4M CMOS process. The specifications are as follows: the input voltage is 5 V, output voltage is 2.5 V, the operating frequency is from 1.5 MHz to 3.25 MHz, and the maximum output current is 500 mA. To compare with eight and single switching frequencies, the proposed frequency hopping circuit can suppress the output harmonics by 27 dB from simulation results. When switching frequency is from low to high with the sawtooth wave, the variation of the output voltage is 42 mV and the recovery time is 70 μs. The variation of the output voltage is 45 mV and the recovery time is 92 μs when switching frequency hops from 3.25 MHz to 1.5 MHz. Similarly, when switching frequency is from low to high with the triangle wave, the variation of the output voltage is 28 mV and recovery time is 47 μs. The variation of the output voltage is 36 mV and the recovery time is 30 μs when switching frequency hops from 3.25 MHz to 1.5 MHz. The output voltage variation and recovery time with the triangle wave are better than those of the sawtooth wave.