Battery charger with a capacitor-diode clamped LLC resonant converter

The paper proposes a novel battery charger through use of two serially-connected LLC resonant converters. The first stage utilises a capacitor-diode clamped LLC resonant converter which allows operation in both constant voltage (CV) and constant current (CC) modes, as found in most battery chargers, to be realised, whilst the second stage provides the necessary gain and line and load regulation. A design example is included that demonstrates the resulting converter topology operating under the full battery charging conditions and its inherent current-limiting capability. Experimental results are used to validate the underlying approach.