Main characteristics and circuit description

AN3014

8/29

Doc ID 16064 Rev 2

The L6563H implements its own burst-mode function. If the COMP voltage falls below 2.5 V,

the IC stops switching, causing an output voltage drop. As a consequence, the COMP

voltage rise again and the IC starts switching again.

In order to achieve better load transient response, the PFC burst-mode operation is partially

forced by the resonant converter: as soon as the L6599A stops switching due to load drops,

its PFC_STOP pin pulls down the L6563H's PFC_OK pin, disabling PFC switching. Thanks

to this simple circuit, the PFC is forced into an idle state when the resonant stage is not

switching, and rapidly wakes up when the downstream converter restarts switching. This

solution prevents significant drop of the bulk voltage in case of abrupt load rising.