Improvement of Power-Conversion Efficiency of AC-DC Boost Converter Using 1:1 Transformer

Abstract

This thesis proposes a circuit structure that can improve the power-conversion efficiency ηe of an AC?DC boost converter. The circuit uses a 1:1 transformer and a voltage boost circuit composed of an inductor, a capacitor, and a diode. The transformer forces the converter to operate in continuous conduction mode for input current, and thereby reduces input ripple. The voltage boost circuit enables the switch to operate in critical conduction mode, so the power loss due to turn-ON of switch and reverse recovery of diode is minimized. The proposed converter has high ηe over a wide range of AC input voltage Vac : ηe = 92.9% at Vac = 85 V and ηe = 97.4% at Vac = 265 V, when the converter was operated at DC output voltage of 400 V and output power of 500W. The temperature of the switch stabilized at ∼84 °C for Vac = 85 V, at ∼70 °C for Vac = 110 V, and at∼42 °C for Vac = 220 V, whereas that in other AC?DC converters either failed or stabilized at much higher levels. The proposed converter is well suited to systems that require an input voltage range of 85?265 V in root-mean-square value.