NCP1282 High Performance Active Clamp/Reset PWM Controller
Featuring 500 V Startup
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.