The NCP12400 is a new fixed−frequency current−mode controller
featuring the Dynamic Self−Supply. This function greatly simplifies
the design of the auxiliary supply and the VCC capacitor by activating
the internal startup current source to supply the controller during
start−up, transients, latch, stand−by etc. This device contains a special
HV detector which detects the application unplug from the ac input
line and triggers the X2 discharge current. This HV structure allows
the brown−out detection as well.
It features a timer−based fault detection that ensures the detection of
overload and an adjustable compensation to help keep the maximum
power independent of the input voltage.
Due to frequency foldback, the controller exhibits excellent
efficiency in light load condition while still achieving very low
standby power consumption. Internal frequency jittering, ramp
compensation, and a versatile latch input make this controller an
excellent candidate for the robust power supply designs.
A dedicated Off Mode allows to reach the extremely low no load
input power consumption via “sleeping” whole device and thus
minimize the power consumption of the control circuitry.

Features
• Fixed−Frequency Current−Mode Operation 65 kHz or 100 kHz
Frequency Options
• Frequency Foldback then Skip Mode for Maximized Performance
in Light Load and Standby Conditions
• Timer−Based Overload Protection with Latched (Option A) or
Autorecovery (Option B) Operation
• High−Voltage Current Source with Brown−Out Detection and
Dynamic Self−Supply, Simplifying the Design of the VCC Circuitry
• Frequency Modulation for Softened EMI Signature
• Adjustable Overpower Protection Dependant on the Mains Voltage
• Fault Input for Overvoltage and Over Temperature Protection
• VCC Operation up to 28 V, with Overvoltage Detection
• 300/500 mA Source/Sink Drive Peak Current Capability
• 4/10 ms Soft−Start
• Internal Thermal Shutdown
• No−Load Standby Power < 30 mW
• X2 Capacitor in EMI Filter Discharging Feature
• These are Pb−Free Devices

Typical Applications
• Offline Adapters for Notebooks, LCD, and Printers
• Offline Battery Chargers
• Consumer Electronic Power Supplies
• Auxiliary/Housekeeping Power Supplies
• Offline Adapters for Notebooks