MP44019

– CRM/DCM MULTI-MODE PFC CONTROLLER WITH SECOND OVP

MP44019 Rev. 1.0

MonolithicPower.com

20

4/30/2021

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© 2021 MPS. All Rights Reserved.

APPLICATION INFORMATION

Design Requirements

Table 1 lists recommended design requirements.

Table 1: Recommended Designs

Parameter

Symbol

Value

Input AC RMS voltage

VAC

85VAC to

265VAC

Input AC voltage

frequency

fLINE

47Hz to

63Hz

Output voltage

VOUT

400V

Output voltage ripple

VO_RIPPLE

≤3% VOUT

Output voltage OVP

threshold

∆OVP

40V

Output power

POUT

240W

Efficiency

η

≥93%

Power Stage Design

Selecting the Bridge

The diode bridge should withstand the maximum

reverse input AC voltage and the maximum input

current. When selecting a diode bridge, consider

the maximum instantaneous voltage (the peak

voltage of the line voltage) and the maximum

input RMS current (the input RMS current at low-

line). In addition, the package size and thermal

performance should also be considered. To

handle the line frequency current, use a standard,

low-cost diode bridge with a slow recovery.

In this case, the maximum input RMS current

can be calculated with Equation (15):



OUT

AC_MAX

MIN

AC_MIN

P

I

=

= 3.04(A)

V

(15)

The maximum instantaneous voltage can be

estimated with Equation (16):

IN_MAX

AC_MAX

V

=

2 V

= 375(V)



(16)

A standard 600V/8A bridge can be selected to

provide enough margin.

Selecting the Input Capacitor

The input capacitor that is placed before the

boost inductor provides a bypass path for the

high switching frequency current and minimizes

fluctuation on the rectified sinusoidal input

voltage. In general, a voltage drop up to 10% on

the input capacitor may be expected. The worst-

case condition occurs when the input voltage is

below its minimum threshold voltage due to a

large current ripple.

The input capacitor (CIN) can be calculated with

Equation (17):

AC_MAX

IN

SW

AC_MIN

I

C

=

2

f

r

V

 

 

(17)

Where r is the coefficient (0.01 to 0.1), and fSW is

the switching frequency at the peak of the

minimum input AC voltage.

Select a capacitor with good high-frequency

performance, such as a film capacitor. For

example, assume a minimum fSW (e.g. 40kHz)

and set r to be 0.05. Then the input capacitance

can be calculated with Equation (18):

AC_MAX

IN

SW

AC_MIN

I

C

=

= 2.85 F

2

f

r

V





 

(18)

Two 1μF film capacitors with a 450V voltage

rating are recommended to act as the input

capacitors because they provide high-frequency

energy during the switching cycle.

Boost Inductor Design

The boost inductance value (LMAX), which is

required to ensure that the maximum load can

be delivered from the minimum input voltage,

can be estimated with Equation (19):

 



2

AC_MIN

ON_MAX

MAX

OUT

Vt

L

=

2P

(19)

The boost inductance value should be below

LMAX. A normal inductance is recommended to

use a 60% to 70% ratio for LMAX to avoid tON being

close to tON_MAX.

If the ratio is selected to be 60%, the actual

inductance can be calculated with Equation (20):

 







2

AC_MIN

ON_MAX

ACTUAL

OUT

V

t

Ratio

L

=

= 182 H

2P

(20)

The boost inductance value should exceed LMIN.

To avoiding triggering over-current protection

(OCP) when triggering the over-current limit

(OCL), there is a delay time (tCS_DELAY) of 100ns,

as well as a MOSFET turn-off delay.