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PFC controller handles critical conduction mode apps

Posted: 05 Jul 2010 ?? ?Print Version ?Bookmark and Share

Keywords:power controller? power-factor correction? PFC? MOSFET?

The FAN7830 from Fairchild Semiconductor is an active power-factor correction (PFC) controller for boost applications that operate in critical conduction mode (CRM). It is designed to support LCD and PDP TV applications, as well as applications using less than 200W where PFC is mandated, including Class C lighting equipment greater than 25W, and Class D PC, TV and monitors greater than 75W.

The device uses a voltage-mode pulse-width modulator, which compares an internal ramp signal to the error amplifier output, resulting in a MOSFET turn-off signal. It does not need rectified AC line voltage information, thus avoiding the power loss of an input voltage sensing network necessary for a current-mode CRM PFC controller.

The controller is packaged in an 8-pin SOP that includes a PFC-ready pin which can be used to trigger the next power stages, as an example in the logic link control conversion stage, when PFC output voltage reaches the proper level with hysteresis. Also in the next power stage, the PFC-ready pin eliminates the need for an external circuit for PFC undervoltage lockout while reducing power loss.

It also features AC Absent Detection function to increase system reliability during the fast AC On-Off Test or in the event of a short electric power failure. The FAN7930 also has soft-start and overshoot-less functions, reducing voltage and current stress at startup while eliminating audible noise from unwanted overvoltage protection triggering.

Pricing for the FAN7930 is at $1.00 each for 1,000 units.

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