Buck Converter with Optocoupler Based Switching

Abstract

This paper presents a new DC-DC buck converter with an optocoupler as a switching device. Conventional buck converters use a transformer for galvanic isolation for the PWM signal, which has a copper, hysteresis, and eddy current losses. In the proposed converter, isolation is achieved with the optocoupler, which prevents losses and has a much higher switching frequency. The proposed circuit consists of a complementary metal-oxide-semiconductor (CMOS)-based half-bridge circuits with anti-phase freewheeling diodes running in an optocoupler device rather than regular switching elements such as insulated gate bipolar transistor (IGBT) or metal oxide semiconductor field-effect transistors (MOSFET). The optocoupler is the latest technology, which is CMOS-based, with high current output and up to 250kHz frequency capability. Because of frequency and current capabilities, it is suitable to use in dc-dc converters. At the same time, the CMOS-based half-bridge circuit has the current blocking capability, and there is no need for a diode that is used at conventional circuits. Finally, the prototype of the proposed converter is tested to verify its efficiency in different applications such as renewable energy battery chargers and a commonly used 12V to 5V converter design. Efficiency calculations are done in comparison with three different conventional converters. As a result, an average 1.1% increase in efficiency is achieved.