A 90 Watt High Efficiency, Notebook Adapter Power Supply With Inherent Power Factor Correction

Introduction This application note describes a relatively novel and simple way to produce an off−line, power factor corrected, 15 V output (and higher) power supply for notebook adapters and similar applications using an isolated, single−stage conversion topology. The power topology is essentially a buck−boost derived flyback converter operating in continuous conduction mode (CCM) and utilizing ON Semiconductor’s NCP1652 controller which was designed specifically for this application. The power supply described in this application note is a 19 V, 5 A supply with universal AC input and is intended as a notebook adapter. Efficiencies approaching 90% were achieved with a power factor exceeding 0.95 for most typical loads. The supply also includes overcurrent protection, overvoltage protection, brownout detection, and an input EMI Filter The NCP1652 converter circuitry is sufficiently versatile that the basic design CAN be modified for LED ballast or other similar applications that require a constant voltage, constant current (CVCC) output characteristic with typical output voltages of 12 V and higher in the 25 to 150 W power range. Background Applications that require an isolated, regulated output voltage along with input power factor correction typically involve a two stage conversion process as depicted in Figure 1. This scheme is composed of an input boost power factor corrector stage which converts and pre−regulates the input line into a 400 Vdc bus. This bus then provides the voltage for a conventional dc−to−dc converter which CAN be of any appropriate topology. For lower power applications of 150 W and less, this is usually a flyback converter.
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Single Stage Converter Schematic
Single Stage Converter Schematic

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