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NCP1217P133
Enhanced PWM Current-Mode Controller for High-Power Universal Off-Line Supplies
NCP1217, NCP1217A
Enhanced PWM Current-Mode
Controller for High-Power
Universal Off-Line Supplies
Housed in an SO−8 or PDIP−7 package, the NCP1217 represents
the enhanced version of the NCP1203−based controllers. Thanks to its
high drive capability, NCP1217 drives large gate−charge MOSFETs,
which together with internal ramp compensation and built−in
overvoltage protection, ease the design of modern AC/DC adapters.
NCP1217 offers a true alternative to UC384X−based designs.
With an internal structure operating at different fixed frequencies
(65–100–133 kHz), the controller features a high−voltage startup FET,
which ensures a clean and loss less startup sequence. Its current−mode
control topology provides an excellent input audio−susceptibility and
inherent pulse−by−pulse control. Internal ramp compensation easily
prevents subharmonic oscillations from taking place in continuous
conduction mode designs.
When the current setpoint falls below a given value, e.g. the output
power demand diminishes, the IC automatically enters the so−called
skip cycle mode and provides excellent efficiency at light loads.
Because this occurs at a user adjustable low peak current, no acoustic
noise takes place.
The NCP1217 features two efficient protective circuitries: 1) In
presence of an overcurrent condition, the output pulses are disabled
and the device enters a safe burst mode, trying to restart. Once the
default has gone, the device auto−recovers. 2) If an external signal
(e.g. a temperature sensor) pulls Pin 1 above 3.2 V, output pulses are
immediately stopped and the NCP1217 stays latched in this position.
Reset occurs when the VCC collapses to ground, e.g. the user unplugs
the power supply.
Features Current−Mode with Adjustable Skip−Cycle Capability Built−in Internal Ramp Compensation Auto−Recovery Internal Output Short−Circuit Protection Internal 1.0 ms Soft−Start (A Version Only) Limited Duty−Cycle to 50% (A Version Only) Full Latchoff if Adjustment Pin is Brought High Extremely Low No−Load Standby Power Internal Temperature Shutdown 500 mA Peak Current Capability Fixed Frequency Versions at 65 kHz, 100 kHz and 133 kHz Direct Optocoupler Connection Internal Leading Edge Blanking SPICE Models Available for TRANsient and AC Analysis Pb−Free Packages are Available
Typical Applications High Power AC/DC Converters for TVs, Set−Top Boxes, etc. Offline Adapters for Notebooks Telecom DC−DC Converters
