Datasheet
APPLICATION INFORMATION
PF = cos θ
UDG-98183
1
11
7
16GND DRVOUT
R17
20
Ω
15
C3
1
µ
F CER
VCC
C2
100
µ F AI EI
14
C1
560pF
13
C4 0.01
µ
F
12
R1 12k
R3 20k
R2
499k
R4
249k
R5
10k
C5 1
µF
9
4
10
V
REF
VCC
CT
SS
RT
VSENSE
OVP/EN
VREF
VAOUT
3
8
2
VFF
C6 2.2µF
C7 150nF
R7 100k
6
5
R9
4.02k
C8 270pF
R8 12k
D6
R10
4.02k
D5
R11
10k
R12
2k
R14
0.25
Ω
3W
C13
0.47
µ
F
600V
C14
1.5
µ
F
400V
R13
383k
IAC
R18
24k
R15
24k
R16
100
Ω
VCC
C10
1 µ F
C11
1 µF
D7
D8
L1
1mH
D2
6A, 600V
D1
8A, 600V
C12
220µF
450V
V
OUT
385V−DC
+
−
PKLIMIT
CAOUT
CAI
MOUT
IAC
V
O
UCC2817
V
LINE
85−270 V
AC
V
REF
C9 1.2nF
R6 30k
6A 600V
D3
Q1
F1
V
O
D4
R19
499k
R20 274k
R21
383k
AC2
AC1
C15 2.2
µ
F
IRFP450
UCC2817-EP
UCC2818-EP
www.ti.com
........................................................................................................................................................................................... SLUS716 – DECEMBER 2008
The UCC2817 is a BiCMOS average current mode boost controller for high-power-factor, high-efficiency,
preregulator power supplies. Figure 1 shows the UCC2817 in a 250-W PFC preregulator circuit. Off-line
switching power converters normally have an input current that is not sinusoidal. The input current waveform has
a high harmonic content because current is drawn in pulses at the peaks of the input voltage waveform. An
active power-factor correction circuit programs the input current to follow the line voltage, forcing the converter to
look like a resistive load to the line. A resistive load has 0 ° phase displacement between the current and voltage
waveforms. Power factor (PF) can be defined in terms of the phase angle between two sinusoidal waveforms of
the same frequency:
Therefore, a purely resistive load would have a power factor of 1. In practice, power factors of 0.999 with total
harmonic distortion (THD) of less than 3% are possible with a well-designed circuit. Following guidelines are
provided to design PFC boost converters using the UCC2817.
NOTE: Schottky diodes, D5 and D6, are required to protect the PFC controller from electrical over stress during
system power up.
Figure 1. Typical Application Circuit
Copyright © 2008, Texas Instruments Incorporated Submit Documentation Feedback 7
Product Folder Link(s): UCC2817-EP UCC2818-EP