Overview: NCP1205 Single Ended PWM Controller Featuring QR Operation and Soft Frequency Foldback
The NCP1205 combines a true Current Mode Control modulator and a demagnetization detector to ensure full Discontinuous Conduction Mode in any load/line conditions and minimum drain voltage switching (Quasi--Resonant operation, also called critical conduction operation). With its inherent Variable Frequency Mode (VFM), the controller decreases its operating frequency at constant peak current whenever the output power demand diminishes. Associated with automatic multiple valley switching, this unique architecture guarantees minimum switching losses and the lowest power drawn from the mains when operating at no--load conditions. Thus, the NCP1205 is optimal for applications targeting the newest International Energy Agency (IEA) recommendations for standby power.
The internal High--Voltage current source provides a reliable charging path for the VCC capacitor and ensures a clean and short startup sequence without deteriorating the efficiency once off.
The continuous feedback signal monitoring implemented with an Overcurrent fault Protection circuitry (OCP) makes the final design rugged and reliable. The PDIP--14 offers an adjustable version of the OVP threshold via an external resistive network.
