The NCP1246 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 detect 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 and 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

Auto−Recovery (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 Bulk Voltage

• Latch−off Input Combined with the Overpower Protection Sensing Input

• VCC Operation up to 28 V, With Overvoltage Detection

• 500/800 mA Source/Sink Drive Peak Current Capability

• 10 ms Soft−Start, 4 ms Soft−Start (AL/BL Versions)

• Internal Thermal Shutdown

• No−Load Standby Power < 30 mW

• X2 Capacitor in EMI Filter Discharging Feature

• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS Compliant

Typical Applications

• AC−DC Adapters for Notebooks, LCD, and Printers

• Offline Battery Chargers

• Consumer Electronic Power Supplies

• Auxiliary/Housekeeping Power Supplies

• Offline Adapters for Notebooks