Variable frequency PWM controlled soft switched FB-PESI Dc/Dc converter

Phase-shift full-bridge (PSFB) Dc/Dc converter has been investigated for decade years and many auxiliary techniques and improvements have been proposed already in the foregoing works to overcome its inherent drawbacks, such as narrow ZVS range for the lagging leg switches, large duty cycle loss and primary-side circulation loss with heavy output load. However, the additional loss and cost are always the key bottleneck for the widely utilization of these works. Phase-shift full-bridge Dc/Dc converter with primary-side energy storage inductor (PSFB-PESI) has been proposed and investigated in recent years. Compared with the traditional PSFB Dc/Dc converter, it has advantages in high conversion efficiency and high power density. However, it is not fit for the wide input voltage range because of its inherent buck -derived characteristic. LLC resonant Dc/Dc converter can improve the conversion efficiency further, but it still has over 1% difference in the full-load efficiency when applied in the areas with wide input voltage range. This paper presents a novel variable frequency PWM control strategy utilized for the FB-PESI Dc/Dc converter to obtain relatively high conversion efficiency over a wide input voltage range.