Novel high-power-factor ZCS-PWM preregulators

This paper introduces novel zero-current-switching (ZCS) pulsewidth-modulat ed (PWM) preregulators based on a new soft-commutation cell, suitable for i nsulated gate bipolar transistor applications. The active switches in these proposed rectifiers turn on in zero current and turn off in zero current-z ero voltage. In addition, the diodes turn on in zero voltage and their reve rse-recovery effects over the active switches are negligible. Moreover, bas ed on the proposed cell, an entire family of de-to-de ZCS-PWM converters ca n be generated, providing conditions to obtain naturally isolated converter s, for example, derived buck-boost, Sepic. and Zeta converters. The novel a c-to-dc ZCS-PWM boost and Zeta preregulators are presented in order to veri fy the operation of this soft-commutation cell, In order to minimize the ha rmonic contents of the input current, increasing the ac power factor, the a verage-current-mode control is used, obtaining preregulators with ac power factor near unity and high efficiency at wide load range. The principle of operation, theoretical analysis, design example, and experimental results f rom test units for the novel preregulators are presented. The new boost pre regulator was designed to nominal values of 1.6 kW output power, 220 V-rms input voltage, 400 V-dc output voltage, and operating at 20 kHz. The measur ed efficiency and power factor of the new ZCS-PWM boost preregulator were 9 6.7% and 0,99, respectively, with an input current total harmonic distortio n (THD) equal to 3.42% for an input voltage with THD equal to 1.61%, at rat ed load, The new ZCS-PWM Zeta preregulator was designed to voltage step-dow n operation, and the experimental results were obtained from a laboratory p rototype rated at 500 W, 220 V-rm, input voltage, 110 V-dc output voltage, and operating at 50 kHz. The measured efficiency of the new ZCS-PWM Zeta pr eregulator is approximately 96.9% and the input power factor is 0.98, with an input current THD equal to 19.07% while the input voltage THD is equal t o 1.96%, at rated load.