MP44019

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

MP44019 Rev. 1.0

MonolithicPower.com

17

4/30/2021

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© 2021 MPS. All Rights Reserved.

VCOMPI

22µs

tD

VCOMPI_BOFF

VCOMPI_C2D

Figure 6: Dead Time Extension

The maximum dead time (tDEAD_MAX) is 23µs.

During this time, COMP reaches its minimum

voltage and linearly approaches 0V as the

internal COMP (VCOMPI) reaches its threshold

(VCOMP_C2D, typically 0.38V).

With this control scheme, the system smoothly

alternates between CrM and DCM as the load is

gradually reduced. This means the switching

frequency is automatically reduced for maximum

efficiency. Figure 7 shows how the switching

frequency changes in a line cycle.

VAC = 230V

fSW

(Hz)

25% Load

64%

Load

100% Load

π

θ

Figure 7: Switching Frequency in a Line Cycle

Figure 8 shows the relationship between the

switching frequency and the load.

fSW

(Hz)

VAC = 90V

VAC = 265V

0%

20%

80%

60%

40%

100%

Load

Figure 8: Switching Frequency vs. Load

Burst Mode Operation

Figure 9 shows a burst mode control diagram.

IP

Soft On

COMPI

VOUT

0

393v

IOUT

60mV

OVP

Soft

Off

120mV

430v

400v

383v

Figure 9: Burst Mode Control

Depending on how the COMP voltage indicates

the load information, the device enters DCM.

The device only enters burst mode under certain

loads to improve light-load efficiency and reduce

standby power loss.

As the load decreases, COMP gradually drops.

When VCOMPI drops below VCOMPI_BOFF (typically

60mV), switching stops with five soft-off pulses.

As VCOMPI ramps up to VCOMPI_BON (typically

120mV), switching resumes with five soft-on

pulses. This soft-on/off control avoids abrupt

inductor current changes, and attenuates the

acoustic noise accordingly.

During the burst-off period, the IC shuts down

most of internal block to ensure that the supply

current is below IQ (typically 180µA).

Improved THD

Under heavy loads, the MP44019 works in CrM.

The average input current in one cycle can be

estimated with Equation (4):













AC

AC

IN

ON

EQ1

v

( )

v

( )

I ( )

t

( )

2 L

R

(4)

Where VAC is the RMS of the line voltage,

calculated with Equation (5):









AC

AC

v ( )

2 V

sin( )

(5)

And REQ1 is the equivalent input resistor, which

can be can be calculated with Equation (6):







EQ1

ON

2L

R

t ( )

(6)

Where tON (θ) is the on time.