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Controller has I/O protection, PFC interface, adaptive UVLO

Posted: 11 Jan 2008 ?? ?Print Version ?Bookmark and Share

Keywords:flyback power converters? multimode controllers? AC/DC adapters?

STMicroelectronics has released a flexible and cost-saving controller for high-performance flyback power converters. The device can operate in either fixed-frequency (FF) or quasi-resonant (QR) mode, the two principal operating modes used in flyback SMPSselectable by connection of a single pin. This enables manufacturers to stock and qualify a single component to meet the requirements of different applications. The chip integrates many protection capabilities commonly implemented with external components, as well as energy-saving features that help the designer to meet the most severe energy regulations.

The L6566 selectable multimode controller is suitable in applications such as flyback AC/DC adapters, TV and LCD monitors, small size LCD TVs, high-end chargers and in other consumer equipment such as DVD players and STBs.

Under very light load conditions, in both operating modes, the chip enters a controlled burst-mode state at low frequency (a few hundred Hertz) with constant peak current, to minimize total power requirements and to comply with global energy-saving recommendations. The controller's quiescent current (less than 3mA) and on-board non-dissipative start-up circuita product of ST's high-voltage process technologyfurther improve the overall efficiency.

The chip is available in two versions: L6566A and L6566B. L6566A is designed for converters supplied through a front-end Power Factor Corrector (PFC) circuit; it provides an interface to the PFC to turn off the regulator under light or no-load conditions and during all the fault conditions. The L6566B version is intended for applications where a front-end PFC is not used, and it includes an oscillator frequency modulation input to reduce EMI emissions, saving cost and size of the line filter when FF operation is selected.

On-chip I/O protection features include over-voltage, cycle by cycle over-current (OCP) and over-temperature protection, brownout protection, and inductor saturation detection (hi-cap mode OCP). An innovative adaptive UVLO circuit prevents the possibility of intermittent operation which can occur under no- load conditions due to the possible IC's own supply voltage fluctuations caused by the transformer's parasitics. This high level of integration enables designers to reduce the number of external components, minimizing PCB area, reducing costs and increasing the reliability of the power supply.

Housed in an SO-16 package, L6566 is available in volume now. Pricing starts at 50 cents in quantities of 2,500 pieces.

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