Recentely, the size of electrical, electronic, and communicational devices are becoming small with development in LSI technology. Accordingly, outside noise and voltage fluctuation of device are causing fatal damage to the devices. And so, constant voltage transformer(CVT) such as AVR and UPS are adopted to prevent that kind of damage.
In this paper, CVT is investigated at the input of converter for stable input voltage. When input voltage of CVT is changed from 180V to 240V, the fluctuation of output voltage is about 2V. And so, Buck converter can be supplied stable DC voltage through rectifier. Because output voltage waveform of CVT is flat top, its r.m.s. value of voltage is almost the same.
Designed CVT is installed in front of rectifier and Buck converter. To minimize THD of the system, input filter is designed and inserted on the basis of extra element theorem.
Based on the analyses, a series of simulation using the MATLAB and PSIM is carried out and an experimental system is designed and fabricated. As a result, when input voltage changes from 180V to 240V, output voltage of the buck converter is stable. And THD of converter is within 8%.