An Integrated AC-DC Isolated Converter Electrolytic-Free With Intrinsic Active Low-Frequency Ripple Reduction

Abstract

Capacitance reduction in single-phase rectifiers has been the focus of several works, allowing, in many cases, the replacement of short-lifetime electrolytic with film capacitors, prolonging the lifespan of the converter. Among the different techniques used to promote this capacitance reduction, the use of modulation and control strategy has the advantage of not adding extra elements to the circuit. Thus, this work proposes the application of a hybrid modulation in a converter derived from integrating an interleaved boost rectifier and a full-bridge Zero Voltage Switching (ZVS) DC-DC converter to reduce the output low-frequency ripple actively. Besides the active low-frequency voltage ripple reduction allowing employ only film capacitors, the proposed solution presents low DC bus voltage, reducing the voltage stress, low input current ripple, simple control strategy, and fast dynamic response. Experimental results of a prototype with a rated power of 300 W are presented to validate of the proposed solution, operating with an efficiency of 92.4%, a power factor of 0.9936, and a total harmonic distortion (THD) of 10%. The adopted hybrid modulation and control strategies allow for reducing the voltage output ripple with a capacitance/watts ratio of $0.18~\mu $ F/W, a 33 times capacitance reduction, avoiding electrolytic capacitors, and maintaining a fast dynamic response of output voltage.

Keywords

• Electrolytic capacitor-free
• low frequency ripple reduction
• power factor correction (PFC)
• power decoupling
• hybrid modulation strategy
• integrated converter