PFS7323-7329
Application Example
A High Efficiency, 350 W, 385 VDC Universal Input PFC
The circuit shown in Figure 14 is designed using a PFS7328H
device from the HiperPFS-2 family of integrated PFC controllers.
This design is rated for a continuous output power of 350 W
and provides a regulated output voltage of 385 VDC nominal
maintaining a high input power factor and overall efficiency from
light load to full load.
Fuse F1 provides protection to the circuit and isolates it from the
AC supply in case of a fault. Diode bridge BR1 rectifies the AC
input. Capacitors C1, C2, C3, and C4 together with inductors
L1, L2, and L3 form the EMI filter reducing the common mode
and differential mode noise. Resistors R1, R2 and CAPZero, IC
U2 are required to discharge the EMI filter capacitors once the
circuit is disconnected. CAPZero eliminates static losses in R1
and R2 by only connecting these components across the input
when AC is removed.
The boost converter stage consists of inductor L5, and the
HiperPFS-2 IC U1. This converter stage works as a boost
converter and controls the input current of the power supply
while simultaneously regulating the output DC voltage. Diode
D3 prevents a resonant build up of output voltage at start-up by
bypassing inductor L5 while simultaneously charging output
capacitor C13. Thermistor RT1 limits the inrush input current of
the circuit at start-up and prevents saturation of L5. In most
high-performance designs, a relay will be used to bypass the
thermistor after start-up to improve power supply efficiency.
Capacitor C10 is used for reducing the loop length and area of
the output circuit to reduce EMI and overshoot of voltage
across the drain and source of the MOSFET inside U1 at each
switching instant.
The PFS7328H IC requires a regulated supply of 12 V for
operation and must not exceed 15 V. Resistors R10, R11, R12,
Zener diode VR1, and transistor Q2 form a series pass regulator
that prevents the supply voltage to IC U1 from exceeding 12 V.
Capacitors C6, and C9 filter the supply voltage and provide
decoupling to ensure reliable operation of IC U1. Diode D5
provides reverse polarity protection.
Resistor R15 programs the output voltage level [via the POWER
GOOD THRESHOLD (PGT) pin] below which the POWER
GOOD [PG] pin will go into a high-impedance state. IC U1 is
configured in full power mode by resistor R14. Capacitor C8
decouples REFERENCE pin of IC U1.
The rectified AC input voltage of the power supply is sensed by
IC U1 using resistors R7, R8 and R9. The capacitor C7 filters
any noise on this signal.
Divider network comprising of resistors R18, R19, R20, and
R21 are used to scale the output voltage and provide feedback
to IC U1. Capacitor C14 enables rapid correction of output
voltage overshoot or undershoot resulting from transient loading.
Resistor R17, R16, and capacitors C12 and C11 are required for
shaping the loop response of the feedback network. The
combination of resistor R16 and capacitor C12 provide a low
frequency zero and the resistor R17, R16 and capacitor C12
form a low frequency pole. C15 and R22 attenuate high-
frequency noise.
Diode D6 protects against an accidentally shorted capacitor
C12 by safely shutting down the IC.
D3
1N5408-T
F1
6.3 A
L
R1
220 kΩ
D1
CAPZero
U2
CAP005DG
BR1
GBU8K-BP
800 V
R7
1.5 MΩ
1%
D
K
V
O
R18
1.5 MΩ
1%
C14
47 nF
200 V
R19
787 kΩ
R20
1.6 MΩ
1%
L5
360
µH
+
C1
680 nF
275 VAC
L2
9 mH
C2
220 nF
275 V
C3
680 pF
250 VAC
RV1
320 VAC
R3
10
Ω
2W
1%
RT1
2.5
Ω
t
L1
Ferrite Bead
O
C5
1
µF
450 V
C4
680 pF
250 VAC
R8
1.5 MΩ
1%
CONTROL
PG
VCC
FB
C
PGT
S
V
G
R
E
R2
220 kΩ
N
D2
R9
1 MΩ
1%
HiperPFS-2
U1
PFS7328H
R17
487
Ω
L3
220
µH
R16
7.5 kΩ
1%
C13
270
µF
450 V
DC
OUT
R5
16 kΩ
R4
10 kΩ
Q1
MMBT4403
R10
1
Ω
1%
D4
BAV16
Q2
MMBT4401LT1G
C10
10 nF
1 kV
D6
BAV116
+
R12
2.2 kΩ
1%
3
1
R6
3 kΩ
+
Remote
ON
U3
LTV817A
D1
S1AB
D2
Auxiliary
Power
Supply
D5
S1AB
C6
47
µF
50 V
VR1
1N4743A
13 V
R14
24.9 kΩ
1%
R15
100 kΩ
1%
C8
470 pF
50 V
C9
3.3
µF
25 V
C11
22 nF
25 V
C12
2.2
µF
25 V
R22
3 kΩ
C15
47 nF
25 V
R21
60.4 kΩ
1%
2
4
R11
1
Ω
1%
C7
22 nF
50 V
V
O
PI-6971-041713
Figure 14. 350 W PFC using PFS7328H.
12
Rev. B 06/13
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POWERINT [ POWER INTEGRATIONS, INC. ]
