AN-6982 Datasheet, PDF (1/15 Pages) Fairchild Semiconductor – Power Factor Correction Converter Design

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AN-6982
Power Factor Correction Converter Design with FAN6982
Introduction
The FAN6982 is a 14-pin, Continuous Conduction Mode
(CCM) Power Factor Correction (PFC) controller IC, that
employs leading-edge modulation for average current
control and has a number of advanced features for better
performance and reliability. The variable output voltage
function (range function) reduces PFC output voltage at
light-load and low-line conditions to improve light-load
efficiency, but can be also easily disabled using EN pin.
The RDY signal can be used for power-on sequence
control of the downstream DC/DC converter. A TriFault
Detect™ function helps reduce external components and
provides full protection for feedback loops such as open,
short, and over voltage. FAN6982 also includes PFC soft-
start, peak current limiting, line feed-forward, and input
voltage brownout protection.
This application note describes the theory of operation and
step-by-step design considerations for a power factor
correction power supply using the FAN6982 controller. A
typical application circuit is shown in Figure 1, where the
supply voltage, V_DD, is supplied from a standby auxiliary
power supply and the supply voltage for the downstream
converter is controlled by the RDY pin.
F₁
AC Input
C_IF2
C_IF1
L_BOOST
D_BOOST
V_BOUT
R_CS
R_DRV Q1
R_PL
C_BOOST
V_OUT
Downstream
DC/DC Converter
R_RMS1
R_LF
C_RMS1
R_RMS2
C_{RMS2 RRMS3} C_LF
R_EN
Range Enabled/Disabled
VEN = VVREF : Enabled
VEN = GND : Disabled
D₁ D₂
R_IAC
C_IC2
R_IC C_IC1
IEA
IAC
ISENSE
VRMS
RDY
EN
RT/CT
VEA
FBPFC
VREF
VDD
OPFC
PGND
SGND
FAN6982
C_T
R_T
R_FB1
PWM Controller
v_CC
C_DD
R_FB2
R_VC
C_FB
C_VC2
C_VC1
R_reg1
Q₂
C_REF
R_reg2
R_reg3
From Standby Auxiliary Power Supply
C_RDY
Figure 1. Typical FAN6982 Application Circuit
© 2010 Fairchild Semiconductor Corporation
Rev. 1.0.0 • 6/8/10
www.fairchildsemi.com