NCP1378

NCP1378 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 ms 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. The transformer core reset detection is done through an auxiliary winding which, brought via a dedicated pin, also enables fast Over Voltage Protection (OVP). Once an OVP has been detected, the IC permanently latches off. The NCP1378 also features an efficient protective circuitry that, in presence of an overcurrent condition, disables the output pulses and enters a safe burst mode, trying to restart. Once the default has gone, the device auto- recovers. Finally an internal 1.0 ms Soft- Start eliminates the traditional startup stress. The NCP1378 is tailored for low voltage applications having UVLO thresholds of 8.4 V (on) and 7.5 V (off). Features  Free- Running Borderline/Critical Mode Quasi- Resonant Operation  Latched Ov...