PFS7523 datasheet(12/36 Pages) POWERINT

12 / 36 page

Rev. A 06/15

PFS7523-7529/7533-7539

www.power.com

Application Example

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

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

HiperPFS- 3 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, 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.

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

events by effectively clamping the input voltage seen by the power

supply.

The boost converter stage consists of inductor L1, and the Hiper-

PFS-3 IC U1. This stage functions as a boost converter and controls

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 simultane-

ously charging output capacitor C17.

Thermistor RT1 limits the inrush input current of the circuit at

start-up and prevents saturation of L1. In most high-performance

designs, a relay will be used to bypass the thermistor after start-up to

improve power supply efficiency. Thermistor RT1 is bypassed by the

electro-mechanical relay RL1 after the output voltage is in regulation

and a power-good signal from U1 is asserted low. Resistor R3, R4,

and 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

optocoupler 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 PFS7527H IC requires a regulated supply of 12 V for operation

and must not exceed 15 V. 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 of 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.

R14, C12 and C13 are required for shaping the loop response of the

feedback network.

400 µH

J3-1

J2-2

J4-1

J4-2

RL1

J2-1

OUT

J3-3

PGT

VCC

REF

CONTROL

HiperPFS-3

PFS7527H

PI-7257-061615

Power

Good

90 - 264

VAC

510 kΩ

1 Ω

10 kΩ

16.2 kΩ

3.01 kΩ

S1AB-13-F

47 µF

50 V

680 nF

450 V

1 µF

35 V

C10

1 µF

50 V

R14

30.1 kΩ

R15

332 kΩ

C11

470 pF

50 V

MMBT4403

LTV817A

MMBT4401LT1G

1 Ω

2.21 kΩ

510 kΩ

680 pF

250 VAC

BR1

GBU8K-BP

800 V

9 mH

330 nF

275 V

680 pF

250 VAC

680 pF

250 VAC

680 pF

250 VAC

5 A

RV1

320 VAC

VCC

Supply

330 nF

275 VAC

RT1

2.5 Ω

CAPZero

CAP003DG

330 µH

C14

1 nF

50 V

C17

180 µF

450 V

R19

162 kΩ

R16

3.74 MΩ

R10

6.2 MΩ

R11

6.2 MΩ

R12

3.74 MΩ

R13

162 kΩ

R17

6.2 MΩ

R18

6.2 MΩ

C15

10 nF

1 kV

C13

1 µF

50 V

1N5408-T

C12

100 nF

25 V

C16

470 pF

50 V

Figure 13. 275 W PFC using PFS7527H.

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