PFS7323L datasheet(4/30 Pages) POWERINT

4 / 30 page

Rev. D 06/15

PFS7323-7329

www.power.com

Figure 3.

Functional Block Diagram.

Functional Description

The HiperPFS-2 is a variable switching frequency boost PFC

solution. More specifically, it employs a constant amp-second

on-time and constant volt-second off-time control algorithm.

This algorithm is used to regulate the output voltage and shape

the input current to comply with regulatory harmonic current

limits (high power factor). Integrating the switch current and

controlling it to have a constant amp-sec product over the

on-time of the switch allows the average input current to follow

the input voltage. Integrating the difference between the output

and input voltage maintains a constant volt-second balance

dictated by the electro-magnetic properties of the boost

inductor and thus regulates the output voltage and power.

More specifically, the control technique sets constant volt-

seconds for the off-time (t

OFF). The off-time is controlled such

that:

OINOFF

(1)

Since the volt-seconds during the on-time must equal the

volt-seconds during the off-time, to maintain flux equilibrium in

the PFC choke, the on-time (t

ON) is controlled such that:

(2)

The controller also sets a constant value of charge during each

on-cycle of the power MOSFET. The charge per cycle is varied

gradually over many switching cycles in response to load

changes so it can be regarded as substantially constant for a

half line cycle. With this constant charge (or amp-second)

control, the following relationship is therefore also true:

(3)

Substituting t

ON from (2) into (3) gives:

(4)

PI-6697-050312

BIAS POWER (VCC)

BOOST DIODE CATHODE (K)

DRAIN (D)

SOURCE (S)

GROUND (G)

POWER GOOD

(PG)

POWER GOOD

THRESHOLD

(PGT)

FEEDBACK

(FB)

COMPENSATION

(C)

REFERENCE

(R)

VCC+

INTERNAL

SUPPLY

REFERENCE

AND BAND GAP

SOFT-

START

VOLTAGE MONITOR (V)

MON

INPUT

LINE INTERFACE

Peak

Detector

IVPK

Input UV

(IUV+/IUV-)

FBOV

~(VO-VIN)

Internal

Reference

VREF

Transconductance

Error-Amplier

FEEDBACK/

COMPENSATION Pin

OV/UV

senseFET

Power

MOSFET

C-UV/OFF

Comparator

IREF

OFF (IREF - IV)

CINT

CUV/

FBOFF/

COFF IOCP

VREF

VPG(H) IPGT

FBCOV

FBCUV

FBCOV

FBON/

FBOFF V

VCC

Buffer and

De-Glitch Filter

CUV/COFF

VFB

VPG(H)

VCC

IPGT

IOCP

VOFF

CINT

IVPK

PON × MON × IS

VCC

Latch

Comparator

INPUT UV

OTP SOA

Comparator

1 kHz Filter

Frequency

Slide

mON is the switch

current sense scale

factor which is a function

of the peak input voltage

OCP

LEB

Feedback-OVP/OFF

Comparator

VOFF is a function of the error-voltage

(VE) and is used to reduce the

average operating frequency as a

function of output power

FBGM

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