NCP1282 Series

The NCP1282 is a voltage mode controller designed for ac-dc or dc-dc converters requiring high efficiency and low parts count. This controller incorporates two in phase outputs with an overlap delay to prevent simultaneous conduction and facilitates soft switching. The main output is designed for driving a forward converter primary MOSFET. The secondary output is designed for driving an active clamp circuit MOSFET, a synchronous rectifier on the secondary side, or an asymmetric half bridge circuit. The NCP1282 reduces component count and system size by incorporating high accuracy on critical specifications such as maximum duty cycle limit, undervoltage detector and overcurrent threshold. Two distinctive features of the NCP1282 are soft-stop and a cycle skip current limit with a time threshold. Soft-stop circuitry powers down the converter in a controlled manner if a severe fault is detected. The cycle skip detector enables a soft-stop sequence if a continuous overcurrent condition is present. Additional features found in the NCP1282 include line feedforward, frequency synchronization up to 1.0 MHz, cycle by cycle current limit with leading edge blanking (LEB), independent under and overvoltage detectors, adjustable output overlap delay, programmable maximum duty cycle, internal startup circuit and soft-start.