New efficient AC-DC converters and their applications

Abstract

AC-DC converters are mostly used as power supplies for microelectronic systems, battery chargers, wind energy applications, electric appliances in household and dc motor drives. Switched-capacitor (SC) network based converters can be good solution to the challenges of 21st century having high voltage conversion ratio and low EMI emissions. The application of this type of converters is in microprocessor based systems where the line voltage requires a steep step down to 3V or even less in order to drive integrated circuits (ICs). In this paper, a new high step down bridgeless single switch AC-DC converter with switched capacitor is proposed. The absence of transformer as well as bridge rectifier reduce the components count, size and cost of the converter. Unlike the existing converters, this proposed buck boost converter is able to achieve simple control structure with single switch, high efficiency, low total harmonic distortion (THD) and high input power factor. Power supplies for microelectronic systems, battery chargers, wind energy applications, electric appliances in the household and dc motor drives require AC-DC converters. The proposed bridgeless Cuk PFC converter in this paper is featured with common ground, transformerless structure, and clear energy delivery process. The absence of bridge rectifiers, transformer and the presence of only two semiconductor switches in the current flowing path during each switching cycle result in less conduction losses and improved thermal management, reducing components count, size and cost of the converter compared to the conventional SEPIC and Cuk PFC converters. Moreover, the presence of two power switches for different half cycles leads to less stress on the power switch. Unlike the existing converters, this proposed bridgeless Cuk PFC converter is able to achieve simple control structure with high efficiency, low total harmonic distortion (THD) and high input power factor. This letter describes a new application of single-ended primary converter (SEPIC) and Cuk converter for dc bipolar net-work. A dc–dc converter configuration based on a combination of both converters is proposed. In the resulting topology, the switching node is shared by the SEPIC and Cuk converter since they have the same instantaneous duty cycle. The main advantage of this topology is that synchronization of various switches is not required, and control terminal is connected to ground which simplifies the design of the gate drive. On the other hand, this configuration allows the connection of renewable energy sources to microgrids (MG)-type bipolar dc link and to cover the current needs of new distributed generation units with efficient, economical, and easy way. To verify its performance, a prototype was designed. Experimental results show as this combination of two converter topologies with appropriated modulation schemes are adequate to use in dc MG.