Step-up converter with high voltage gain employing three-state switching cell and voltage multiplier

Abstract

This work proposes a new non-isolated DC-DC converter with high voltage gain using a three-state switching cell and voltage multiplier stages based on capacitors. The value of the gain can be modified depending on the requirements of the application by means of the number of multiplier stages and the duty cycle. The proposed converter can be employed in renewable energy systems where commonly low input voltages (12 Vdc to 48 Vdc) are involved or in uninterrupted power supply (UPS) systems in order to avoid the necessity of a step-up transformer. One first advantage of the proposed solution is the reduced voltage stress across the active switches that is lower than half of the output voltage, what allows the use of MOSFETs with lower drain-to-source resistance. Moreover, by employing the three-state switching cell, the size of the inductor is reduced because the operating frequency of the inductor is double of the switching frequency. The current share between the active switches allows further reduction of the conduction losses. A prototype was built for an input voltage range of 30-45 V, 400 V output voltage and 250 W output power. The operation was evaluated and the experimental waveforms and experimental efficiency curves as a function of the output power are presented.