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NCP1240: Controller, Fixed Frequency, Current Mode, Dual OCP for Flyback Converters

The NCP1240 is a new fixed−frequency current−mode controller featuring 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. The NCP1240 differentiates itself from the rest of the fixed frequency flyback controllers with active X2 discharge and HV start up by implementing a Dual-Level Overcurrent protection. For some applications (e.g. limited power supplies), it is necessary that the controller maintains regulation while it has detected a first level of overload. This is to authorize a transient peak power higher than the maximum continuous output power. This product is IEC60950 compliant. Please see the test report and certification in the Conformance report section below.

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