The NCP1623 is a controller designed to drive PFC boost stages. Based on an innovative Valley Synchronized Frequency Fold-back (VSFF) method, it operates in critical conduction mode (CrM) until the power drops below a threshold level. The PFC controller enters discontinuous conduction mode (DCM) with increased dead-time as the load further decays (frequency foldback). VSFF maximizes the efficiency at both nominal and light loads. In addition, an internal circuitry ensures a near-unity power factor even when the switching frequency is reduced.
Housed in a TSOP-6 package, the circuit also incorporates the features necessary for robust and compact PFC stages, with few external components. The A version provides the follower boost capability for drastic low-line efficiency improvement. This controller is also available in the SOIC-8 package, which features an ultra-low-consumption mode externally controlled by the disable pin.