Power chip

The NCP1251 is a highly integrated PWM controller capable of providing robust high performance off-line power within a very small TSOP-6 encapsulation. The controller has a supply range up to 28 V, has a dithered 65 kHz or 100 kHz switching circuit, and operates under peak current mode control. When the power on the auxiliary side starts to decrease, the controller automatically folds back its switching frequency to a minimum of 26 kHz. As the power drops further, the part enters a skip cycle while limiting the peak current. Overpower protection (OPP) is a difficult measure, especially when no-load standby requirements drive converter specifications. ON Semiconductor's proprietary integrated OPP allows you to take full advantage of the highest power available with only two external resistors, without compromising standby performance. Combined latched overvoltage protection (OVP) on the same pin. To simplify implementation, the auto-recovery OVP also monitors the Vcc line. These features provide effective protection in the event of optocoupler failure or reverse switching operation. Finally, timer-based short-circuit protection provides the best protection scheme, allowing you to precisely select the protection trip point regardless of the loose coupling between the auxiliary winding and the mains winding.