Design of a 2.5-kW 400/12-V High-Efficiency DC/DC Converter Using a Novel Synchronous Rectification Control for Electric Vehicles

This paper proposes the design of a 2.5-kW 400/12 V high-efficiency isolated dc/dc converter for electric vehicles. The designed system accommodates the wide-range input voltage (450 V–220 VDC) and output voltage (16 V–6 VDC). An LLC half-bridge topology is adopted as the primary side of the dc/dc converter. For the secondary side, a novel synchronous rectification control (SRC) strategy is developed to switch metal oxide semiconductor field effect transistors (MOSFETs) through accurately tracking the target switching moments. Experimental results were carried out to charge the on-board 12-V battery and validate the proposed control algorithm. The maximum system efficiency is 93.2%. System power loss is also itemized.

I. Introduction

Battery electric vehicles (BEVs) have no internal combustion engines (ICEs), where high-voltage (e.g., 400 V) lithium-ion batteries become the only energy source. Therefore, a 400/12-V VDC isolated dc/dc converter is a must to bridge the high-voltage battery pack with the 12-V lead-acid battery and its auxiliary circuits, acting as an electric alternator. Such converter is also known as the accessory power module (APM). Given the scenario when all the 12-V utilities (GPS, radio, air conditioners, etc.) are on, a 2.5-kW power rating is required, which represents output current at the 12 VDC side.