AN2644 Datasheet, PDF (1/64 Pages) STMicroelectronics – An introduction to LLC resonant

AN2644
Application note
An introduction to LLC resonant
half-bridge converter
Introduction
Although in existence for many years, only recently has the LLC resonant converter, in
particular in its half-bridge implementation, gained in the popularity it certainly deserves. In
many applications, such as flat panel TVs, 85+ ATX PCs or small form factor PCs, where the
requirements on efficiency and power density of their SMPS are getting tougher and
tougher, the LLC resonant half-bridge with its many benefits and very few drawbacks is an
excellent solution. One of the major difficulties that engineers are facing with this topology is
the lack of information concerning the way it operates. The purpose of this application note
is to provide insight into the topology and help familiarize the reader with it, therefore, the
approach is essentially descriptive.
Figure 1. LLC resonant topology schematics and waveforms
September 2008
Rev 2
1/64
www.st.com