February 2013
?2008 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN9612 " Rev. 1.1.7
FAN9612
Interleaved Dual BCM PFC Controllers
Features
?   Sync-Lock" Interleaving Technology for 180?/SPAN>
Out-of-Phase Synchronization Under All Conditions
?   Automatic Phase Disable at Light Load
?   Dead-Phase Detect Protection
?   2.0 A Sink, 1.0 A Source, High-Current Gate Drivers
?   High Power Factor, Low Total Harmonic Distortion
?   Voltage-Mode Control with (V
IN
)
2
Feedforward
?   Closed-Loop Soft-Start with User-Programmable
Soft-Start Time for Reduced Overshoot
?   Minimum Restart Frequency to Avoid Audible Noise
?   Maximum Switching Frequency Clamp
?   Brownout Protection with Soft Recovery
?   Non-Latching OVP on FB Pin and Latching Second-
Level Protection on OVP Pin
?   Open-Feedback Protection
?   Power-Limit and Current Protection for Each Phase
?   Low Startup Current of 80 ?/SPAN>A Typical
?   Works with DC and 50 Hz to 400 Hz AC Inputs
Applications
?   100-1000 W AC-DC Power Supplies
?   Large Screen LCD-TV, PDP-TV, RP-TV Power
?   High-Efficiency Desktop and Server Power Supplies
?   Networking and Telecom Power Supplies
?   Solar Micro Inverters
Description
The FAN9612 interleaved dual Boundary-Conduction-
Mode (BCM) Power-Factor-Correction (PFC) controller
operates two parallel-connected boost power trains 180?
out of phase. Interleaving extends the maximum practical
power level of the control technique from about 300 W to
greater than 800 W. Unlike the continuous conduction
mode (CCM) technique often used at higher power
levels, BCM offers inherent zero-current switching of the
boost diodes, which permits the use of less expensive
diodes without sacrificing efficiency. Furthermore, the
input and output filters can be smaller due to ripple
current   cancellation   and   effective   doubling   of   the
switching frequency.
The converter operates with variable frequency, which is
a function of the load and the instantaneous input /
output   voltages.   The   switching   frequency   is   limited
between   16.5 kHz   and   525 kHz.   The   Pulse   Width
Modulators (PWM) implement voltage-mode control with
input voltage feedforward. When configured for PFC
applications, the slow voltage regulation loop results in
constant on-time operation within a line cycle. This PWM
method, combined with the BCM operation of the boost
converters, provides automatic power factor correction.
The controller offers bias UVLO of 12.5 V / 7.5 V, input
brownout,   over-current,   open-feedback,   output   over-
voltage, and redundant latching over-voltage protections.
Furthermore, the converters output power is limited
independently of the input RMS voltage. Synchronization
between the power stages is maintained under all
operating conditions.
Figure 1.   Simplified Application Diagram