MP44011 – BOUNDARY-MODE PFC CONTROLLER WITH HARMONIC INJECTION

MP44011 Rev. 1.01

www.MonolithicPower.com

12

1/12/2012

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© 2012 MPS. All Rights Reserved.

DESIGN EXAMPLE FOR FLYBACK

PFC WITH MP44011

1. Design Specifications:

Input voltage range:

Typical mains frequency:

DC output voltage:

Maximum output power:

Δ

Minimum switching frequency:

Harmonic injection ratio:

Reflected voltage:

Leakage inductance overvoltage:

Δ

V=100V

Expected efficiency:

η

=85%

2. Preliminary Calculations:

Minimum Input Peak Voltage:

Maximum Input Peak Voltage:

Maximum Input Power:

Peak-to-Reflected Voltage Ratio:

Characteristic functions value:

-3

V

V

V

0.5+1.4 10

K

F2(K )=

1+0.815 K





-4

V

V

V

0.424+5.7 10 K

F3(K )=

1+0.862 K





-3

V

V

V

0.25-1.5 10

K

F4(K )=

1+1.074 K





2.1 Peak Primary Current

1in

PKp

PKmin

V

2K P

I1.51A

VF2(K )







primary-current

ratio

compared

with

the

2.2 RMS Primary Current:

V2

RMSp

PKp

F2(K K )

I=I

=0.53A

3





2.3 Peak Secondary Current:

OUT

PKs

OUT

V

V

2P

I =

=4.29A

VK F2(K )





2.4 RMS Secondary Current:

V

RMSs

PKs

F3(K )

I=I

=1.03A

3



Power Stage Design

3. Diode Bridge

The maximum input RMS current is:

in

AC _ max

AC_min

P

I0.42(A)

V



To provide a sufficient margin, select GBU406

(600V/4A).

4. Input Capacitor

By setting the coefficient r to 0.1, obtain the input

capacitance by using the equation below:

AC_max

6

in

min

AC _ min

I

C =

0.19 10 (F)

2π fr V





 

Use a 0.22μF tantalum capacitor with a 630V

voltage rating as the input capacitor to provide

high-frequency energy during switching cycle.

5. Transformer

Calculate the primary Inductance using the

following:

PKmin

2

p

2V

min

PKp

VK

L=

=1.0mH

(1+K K ) f

I





