Technical Session - 1

Title:            Improving Battery Charging Efficiency with Soft Switching Technique
Authors:       Ngo Phi Thuong, Nam Nguyen-Quang
Abstract:     Battery is an essential component of energy systems, especially in renewable applications, where power imbalance between supply side and load side exists. Chargers are used to store redundant energy when generated power (from renewable sources) is larger than the load consumption, with an expectation for high conversion efficiency. This paper presents an implementation of the DC/DC converter for battery charging applications, aiming at improving energy conversion efficiency. This converter is controlled with soft switching methods with respect to variations in input voltages and load conditions. It has zero voltage turn on for its primary switches thus reducing losses and increasing energy efficiency. The results obtained using this design along with synchronous rectifier can lead to an efficiency in the range of 95% or higher, which is difficult to achieve using hard switching converters. Soft switching techniques also help increase the operating frequency of the converter, which in turn reduces the volume/size of passive components, leading to lighter and smaller chargers. This paper proposes a new approach where frequency control is combined with synchronous rectification in a DC/DC resonant converter. The resulting system consists of a high efficiency DC/DC converter and has been simulated in LTSpice and designed to be controlled by an ARM Cortex-M4 microcontroller. The performance of the proposed system has been experimentally verified on a 120 W prototype of battery charger, supplied by two PV panels connected in series, confirming the feasibility of the proposed converter design and control method.

Keywords:  Battery Charging, Efficiency, Soft Switching, Zero Voltage Switching, Frequency Control, Synchronous Rectification
Pages:        214-220

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