Step-down controller integrates active PFC

A new integrated controller aims to simplify the design of power-factor-corrected isolated power convertors, reducing both part count and overall design costs for distributed power systems up to 200W.

The NCP1651 is an integrated controller that facilitates the simplest possible implementation of power-factor corrected, isolated power convertors and reduces both part count and overall design costs for power conversion applications such as battery chargers and distributed power systems up to 200W.

The NCP1651 provides a low-cost, low component-count solution that is compliant with IEC1000-3-2 harmonic standards for isolated AC/DC convertors with mid to high output voltage requirements.

Fixed-frequency continuous conduction mode (CCM) operation simplifies the design of the input EMI filter and optimises efficiency.

The controller also can operate in discontinuous conduction mode for maximum design flexibility.

Compared with a conventional power conversion design that uses a PFC controller followed by a DC/DC convertor, the unique single-stage design of the NCP1651 eliminates one entire power switching section including the boost inductor, the power mosfet, the high-voltage capacitor and ancillary components.

Unlike other "single-stage" solutions, the NCP1651 approach reduces the power stage requirements to a minimum: a single magnetic element, a switch, a diode and a capacitor.

An internal high-voltage startup circuit reduces component count further by eliminating external startup circuitry.

Other features of the NCP1651 include a high-accuracy multiplier that reduces overdesign of the power components, an overtemperature shutdown and an undervoltage lockout.

ON Semiconductor offers a design tool for the NCP1651 that reduces the time needed to produce a first-pass working circuit from days to hours.

Starting with a few key metrics provided by the design engineer, the tool uses a sophisticated design methodology to select the correct component values and produce a complete bill of materials.

The tool also displays graphs of key performance parameters to aid in system fine-tuning.

The NCP1651 design aid is downloadable from the ON Semiconductor website.

"The NCP1651 is ideally suited for notebook adapters, distributed power systems and any similar application where the designer is concerned about minimising cost, component count, and size, yet still requires high-input power factor and low THD (total harmonic distortion)," said Andy Williams, ON Semiconductor Director of Power Conversion Products.

The NCP1651 is offered in a compact SO-16 package and is priced at $1.50 per unit in 10,000-unit quantities.

Back to top