PWM Current−Mode Controller for Free−Running Quasi−Resonant Operation

The NCP1378 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 8.0 s timer prevents the free−run frequency to exceed 100 kHz (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.

FEATUREs
•Free−Running Borderline/Critical Mode Quasi−Resonant Operation
•Latched Overvoltage Protection
•Auto−Recovery Short−Circuit Protection Via UVLO Crossover
•Current−Mode with Adjustable Skip Cycle Capability
•Internal 1.0 ms Soft−Start
•Internal Temperature Shutdown
•Internal Leading Edge Blanking
•500 mA Peak Current Source/Sink Capability
•External Latch Triggering, e.g. Via Overtemperature Signal
•Direct Optocoupler Connection
•SPICE Models Available for TRANsient Analysis
•Internal 8.0 s Minimum TOFF
•Pb−Free Packages are Available*

Typical Applications
•Battery−Based Operations