Pulse Width and Frequency Hybrid Modulated LLC Converter Adapted to Ultra Wide Voltage Range

Abstract

In wide voltage range applications such as electric vehicles (EVs) onboard charging, conventional frequency modulated LLC topology has its intrinsic limitations. Its frequency span is extremely wide and the soft switching feature might get lost. To address this issue, this paper proposes a novel LLC resonant converter. The pulse width and frequency hybrid modulation are adopted to narrow down its switching frequency span. The operating principles, circuit modeling, and the design methodology are presented. A 1 kW rated prototype has been built to realize an efficient power flow between the 400 V DC bus and 200⁻440 V battery pack. The designed prototype validates the effectiveness of the proposed topology and modulation method. 96.8% peak efficiency is measured for the constructed experimental prototype.

Keywords

• LLC
• resonant converter
• PWM
• EV chargers