G2SB20 datasheet(21/62 Pages) VISHAY

21 / 62 page

Rectifiers for Power Factor Correction (PFC)

Application Note

www.vishay.com

Vishay General Semiconductor

Revision: 15-Nov-16

Document Number: 88868

For technical questions within your region: DiodesAmericas@vishay.com, DiodesAsia@vishay.com, DiodesEurope@vishay.com

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000

HOW A STANDARD PFC CIRCUIT WORKS

Fig. 4. shows the typical topology of a PFC pre-stage that is

built of a standard boost converter driven by a control IC. It

is important that at the output of the Rectifier BR1 there will

be no ”large” smoothing capacitor with several μF

connected, because that would eliminate all efforts of the

PFC circuit, although it would operate sufficiently. The input

voltage of the PFC is a rectified DC voltage pulsed with

double line frequency. The shown switch is usually

implemented by an IGBT or Power-MOS transistor.

Operation principle:

The instantaneous value of the current through the boost

inductor has to be adapted as well as possible to the

instantaneous value of the line voltage through suitable

pulse-width modulation of the transistor switch T. The actual

inductor current can be won by the voltage drop at R3. The

input voltage can be found at the voltage divider R1, R2. The

current amplitude will be regulated on the value of the

output voltage, R4, R5.

To be able to control the current through the boost inductor,

the output voltage of the PFC has to be higher at every

moment of operation than the crest of the line input voltage.

For 230 V mains the DC output should be about 400 V. A

large capacitor at the output does not affect the power

factor, but is good for smoothing the DC voltage.

An additional advantage of PFC circuit is the regulated DC

voltage that gives the opportunity of having a following

SMPS to be wide range operated (e.g. 110 V to 230 V input

voltage).

ADVANTAGES OF CIRCUITS WITH PFC

• The use of PFC allows the manufacturer of electrical load to use smaller, more cost-effective mains rectifiers because of

smaller RMS current with PFC.

• Offers a stable regulated output voltage which is the input voltage for the following electrical load. Indeed the PFC makes it

a system based wide-range power supply itself.

• The following electrical load (SMPS, electronic ballast unit or other electrical load) can be much simpler, which is also a cost

saving factor.

Vishay General Semiconductor recommends the use of their ultrafast rectifier series of PFC rectifier.

RECOMMENDED REVERSE VOLTAGES FOR MOST USED LINE VOLTAGE LEVELS

VLINE RMS

(V)

VRRM

(V)

110

400

120

400

230

600

277

600

G2SB20 Datasheet(PDF) 21 Page - Vishay Siliconix

G2SB20 Datasheet(HTML) 21 Page - Vishay Siliconix

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

Datasheet Download

Link URL