Half Bridge Converter
Half-bridge converters are mainly used in AC-to-DC power supplies, when a reduced voltage stress on the primary switching devices together with a high system efficiency are required. Generally a power factor corrector (PFC) front-end stage is used to deliver a stable high-voltage bus to the downstream converter. The block diagram will help you make the right choice from a wide range of recommended products.
AN993: Electronic ballast with PFC using L6574 and L6561