NCP1308

The NCP1308 combines a true current mode modulator and a demagnetization detector to ensure full borderline/Critical Conduction Mode in any load/line conditions and minimum drain voltage switching (Quasi−Resonant operation). Due to its inherent skip cycle capability, the controller enters burst mode as soon as the power demand falls below a predetermined level. As this happens at low peak current, no audible noise can be heard. An internal 10 s timer prevents the free−run frequency to exceed a high frequency (therefore below the 150 kHz CISPR−22 EMI starting limit), while the skip adjustment capability lets the user select the frequency at which the burst foldback takes place.

The Dynamic Self−Supply (DSS) drastically simplifies the transformer design in avoiding the use of an auxiliary winding to supply the NCP1308. This feature is particularly useful in applications where the output voltage varies during operation (e.g. battery chargers). Thanks to its high−voltage technology, the IC is directly connected to the high−voltage DC rail. As a result, the short−circuit trip point is not dependent upon any V_CC auxiliary level.

The NCP1308 transformer core reset detection is done through an auxiliary winding which, brought via a dedicated pin. If an OVP is detected on the V_CC pin, the IC permanently latches off.

Finally, the NCP1308 continuous feedback signal monitoring implemented with an Overcurrent fault Protection circuitry (OCP) makes the final design rugged and reliable.