onsemi (Ansemi)

PDIP-7

Tube

50

The NCP1129 provides everything needed to build a reliable and compact AC-DC switching power supply with minimal peripheral components. Converters built using the NCP1129 incorporating MOSFETs with an avalanche rating of 650 V can be safely designed for international conditions without compromising overall reliability. The NCP1129 implements peak current mode control and adjustable slope compensation to ensure stability in continuous conduction mode (CCM) operation. The maximum peak current is adjustable using an external resistor, allowing designers to add slope compensation to stabilize the CCM supply. Short circuit fault conditions are detected independently from the auxiliary winding voltage, thus improving short circuit protection with true overload detection. The SOURCE pin provides access to the MOSFET source for overpower compensation. With a supply range up to 26 V, the switch also offers a dithered 65 kHz or 100 kHz switching frequency and operates under peak current mode control. When the power on the auxiliary side starts to decrease, the switch 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.