Rev. F 08/20

13

PFS7x23-7x29/7633-7636

www.power.com

Application Example for H and L Packages

A High Efficiency, 275 W, 385 VDC Universal Input PFC

The circuit shown in Figure 13 is designed using a device from the

HiperPFS-4 family of integrated PFC controllers. This design is rated

for a continuous output power of 275 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 the event of a fault. Diode bridge BR1 rectifies the AC input

voltage. Capacitors C1-C7 together with inductors L2 and L3 form

the EMI filter which reduces the common mode and differential mode

noise. Resistors R1, R2 and CAPZero-2, IC U2 are required to

discharge the EMI filter capacitors once the circuit is disconnected.

CAPZero-2 eliminates static losses in R1 and R2 by only connecting

these components across the input when AC is removed.

Metal oxide varistor (MOV) RV1 protects the circuit during line surge

events by effectively clamping the input voltage seen by the power

supply.

Inductor L1 and boost diode D4 in conjunction with HiperPFS-4 IC U1,

form the boost converter stage, controlling the input current of the

power supply while simultaneously regulating the output DC voltage.

Diode D2 prevents a resonant buildup of output voltage at start-up by

bypassing inductor L1 while simultaneously charging output capacitor

C18.

Thermistor RT1 limits the inrush input current of the circuit at start-up

and prevents saturation of L1. However in the highest efficiency

designs, an electro-mechanical relay RL1 will be used to bypass the

thermistor once the output voltage is in regulation as indicated by a

power good signal (asserted low). Resistors R3 and R4, and transistor

Q1, drive relay RL1 and optocoupler U3. Diode D1 clamps the relay

coil reverse voltage during de-assertion transitions. Resistor R5 limits

the current to the diode in the optocoupler. IC U3 provides optocou-

pler isolation through connector J2 for a power-good output signal if

required.

Capacitor C15 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 edge.

The PFS7627H IC requires a regulated supply of 12 V for operation

(15 V max). Resistors R6, R7, R8, Zener diode VR1, and transistor Q2

form a series pass regulator that prevents the supply voltage to IC U1

from exceeding 15 V. Capacitors C8, and C9 filter the supply voltage

and provide bypassing and decoupling to ensure reliable operation of

IC U1. Diode D3 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. Capacitor C14 provides noise

immunity on the POWER GOOD THRESHOLD pin.

IC U1 is configured in full power mode by capacitor C10 which is

connected to the REFERENCE pin.

The rectified AC input voltage of the power supply is sensed by IC U1

using resistors R10-R13. These resistors values are large to minimize

power consumption. Capacitor C11 connected in parallel with the

bottom resistor R13 filters noise coupled into the VOLTAGE MONITOR

pin.

Output voltage divider network comprising resistors R16 – R19 are

used to scale the output voltage and provide feedback to the IC.

Capacitor C16 in parallel with resistor R19 attenuates high frequency

noise.

Components R14, C12 and C13 are required for shaping the loop

response of the feedback network.

L1

400 µH

VO

J3-1

J2-2

J4-1

J4-2

RL1

J2-1

DC

OUT

+

VO

J3-3

PI-8054a-120418

N

Power

Good

90 - 264

VAC

E

L

R1

510 kΩ

R6

1 Ω

1%

R3

10 kΩ

1%

R4

16.2 kΩ

1%

R5

3.01 kΩ

1%

D1

S1AB-13-F

C8

47 µF

50 V

C7

680 nF

630 V

C9

1 µF

35 V

C10

1 µF

50 V

R14*

30.1 kΩ

1%

R15

332 kΩ

1%

C11

470 pF

50 V

Q1

MMBT4403

3

4

2

1

U3

LTV817A

Q2

MMBT4401LT1G

R7

1 Ω

1%

R8

2.21 kΩ

1%

R2

510 kΩ

C2

680 pF

250 VAC

BR1

GBU8K-BP

800 V

L2

9 mH

C4

330 nF

275 V

C6

680 pF

250 VAC

C5

680 pF

250 VAC

C1

680 pF

250 VAC

F1

5 A

RV1

520 VAC

VCC

Supply

C3

330 nF

275 VAC

RT1

2.5 Ω

D1

CAPZero

U2

CAP200DG

D2

L3

330 µH

+

+

C14

1 nF

50 V

C18

180 µF

450 V

R19

162 kΩ

1%

R16

3.74 MΩ

1%

R10

6.2 MΩ

1%

R11

6.2 MΩ

1%

R12

3.74 MΩ

1%

R13

162 kΩ

1%

R17

6.2 MΩ

1%

R18

6.2 MΩ

1%

C15

10 nF

1 kV

C13*

1 µF

50 V

D2

1N5408-T

D4

LXA06T600

C12*

100 nF

25 V

C16

470 pF

50 V

tO

S

D

C

PGT

FB

VCC

PG

REF

G

V

CONTROL

HiperPFS-4

U1

PFS7627H

Figure 13. 275 W PFC using PFS7627H (*Note: Use R14 = 20 kW, C13 = 2.2 mF, C12 = 150 nF When Designing with PFS7626C and PFS7628C).