A novel current-limiting method for LLC DC/DC resonant converter

Abstract

Constant current control is a difficult issue for LLC resonant converter due to its variable frequency operation. After detailed analysis on the short circuit operation of conventional LLC DC-DC converter, a novel current-limiting method with the help of diode clamping is proposed. Against the conventional wisdom, the switching frequency is reduced toward zero to control the output current under over-load and short circuit condition ultimately. By doing so, the ultra-high frequency operation can be avoided for current-limiting at short circuit. A 480W 12V/40A prototype with proposed concept has been built to verify the theoretical analysis.