An LLC Converter with Capacitive Insulation

Abstract

Offline power converter products must apply for and pass the national electrical safety code before they can be marketed. The transformers of offline power converters must be made from certificated materials with a high voltage rating and high electrical insulation, which increases the volume of the transformers and the printed circuit boards. In most studies, the miniaturization of a power converter is usually achieved by increasing the conversion efficiency and reducing the heat sink, or by increasing the switching frequency to reduce the size of the transformers. In this paper, the insulation material is reduced to miniaturize the transformer of the LLC converter. The resonant capacitor of the LLC converter is used to meet the requirements of insulation voltage, leakage current, creepage, and clearance. A prototype with the specifications of 12 V and 10 A rated output was built to verify the proposed method.

Keywords

• capacitive isolation
• LLC converter
• leakage current
• touch current