AN-6961 Datasheet, PDF (1/8 Pages) Fairchild Semiconductor – Critical Conduction Mode PFC Controller

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AN-6961
Critical Conduction Mode PFC Controller
Description
This application note describes a power factor correction
(PFC) circuit using the FAN6961. Both the features of this
controller, as well as the operation of the power factor
correction circuit, are presented in detail. Based on the
proposed design guideline, a design example with detailed
parameters demonstrates the performance of the controller.
Introduction
The FAN6961 PFC controller is an 8-pin Boundary Current
Mode (BCM) IC intended for controlling PFC pre-regulators.
The FAN6961 provides a controlled on-time to regulate the
output DC voltage and achieve natural power factor
correction. The maximum on-time of the switch is
programmable to ensure safe operation during AC
brownouts. An innovative multi-vector error amplifier is built
in to provide rapid transient response and precise output
voltage clamping. Once the output feedback loop is opened,
the output driver (GD) is disabled to provide protection of
the system. The start-up current is lower than 20µA and the
operating current has been reduced to 5mA. The supply
voltage can be operated up to 25V, maximizing application
flexibility. The FAN6961 also enables cycle-by-cycle current
limiting protection for the external power MOSFET.
Figure 1. Power Factor Correction Circuit
© 2009 Fairchild Semiconductor Corporation
Rev. 1.0.2 • 4/8/09
www.fairchildsemi.com