PFS7523LSLASHH datasheet(13/37 Pages) POWERINT

13 / 37 page

Rev. D 04/25

PFS7523-7529/7533-7539

www.power.com

Application Example 2

A High Efficiency, 750 W, 385 VDC High-Line Input PFC

The circuit shown in Figure 14 is designed using a device from the

HiperPFS- 3 family of integrated PFC controllers. This design is rated

for a continuous output power of 750 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 and BR2 rectifies the

AC input voltage. Capacitors C32, C33, C35, C36, C37, C38, C60, C61

and C62 together with inductors L1, L2 and L4 form the EMI filter

which reduces the common mode and differential mode noise.

Resistors R42, R43 and CAPZero, IC U5 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 T2, and the Hiper-

PFS-3 IC U6. This stage functions as a boost converter and controls

the input current of the power supply while simultaneously regulating

the output DC voltage. Diode D8 prevents a resonant buildup of

output voltage at start-up by bypassing inductor T2 while simultane-

ously charging output capacitors C40 and C49.

Thermistor RT1 limits the inrush input current of the circuit at

start-up and prevents saturation of T2. 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.

Resistor R45, R46 and Q10 drive relay RL1 with a signal from Down

Stage DC/DC converter. Diode D9 clamps the relay coil reverse

voltage during de-assertion transitions.

Capacitor C41 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 U6 at each switching edge.

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

and must not exceed 15 V. Resistors R52, R71, Zener diode VR3,

Diode D11 and transistor Q2 form a series pass regulator that

prevents the supply voltage to IC U6 from exceeding 15 V. Capacitor

C47 filter the supply voltage and provide bypassing and decoupling to

ensure reliable operation of IC U6.

Resistor R53 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 C43 provides noise immunity

on the POWER GOOD THRESHOLD pin.

IC U6 is configured in full power mode by capacitor C44 which is

connected to the REFERENCE pin.

The rectified AC input voltage of the power supply is sensed by IC U6

using resistors R48, R50, R51 and R56. These resistors values are

large to minimize power consumption. Capacitor C45 connected in

parallel with the bottom resistor R56 filters noise coupled into the

VOLTAGE MONITOR pin.

Output voltage divider network comprising of resistors R47, R49, R55

and R57 are used to scale the output voltage and provide feedback to

the IC. Capacitor C48 in parallel with resistor R57 attenuates high

frequency noise.

R54, C46 and C42 are required for shaping the loop response of the

feedback network.

PFS7523L/H 数据表(PDF) 13 Page - Power Integrations, Inc.

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