MP44010 – BOUNDARY MODE PFC CONTROLLER

MP44010 Rev. 1.11

www.MonolithicPower.com

10

10/17/2012

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2012 MPS. All Rights Reserved.

When the current of the Boost inductor reaches

zero, the voltage on the inductor will be reversed.

Then ZCS generates the turn-on signal of the

MOSFET by sensing the falling edge of the

voltage on the auxiliary winding coupled with the

inductor. If the voltage of the ZCS pin rises above

2.1V, the comparator waits until the voltage falls

below 1.35V. Once the voltage falls below 1.35V,

the MP44010 turns on the MOSFET. The 7.8V

high clamp and 0.55V low clamp protect the ZCS

pin. The internal 175µs timer generates a signal

to turn on the MOSFET if the driver signal has

been low for more than 175µs. This also allows

the MOSFET to turn on during start-up period

since no signal is generated from ZCD then.

Zero-crossing Compensation

The MP44010 offers 30mV voltage offset for

multiplier output near the zero-crossing of the line

voltage which can force the circuit to process

more energy at the bottom of the line voltage.

With this function, the THD of the current could

be evidently reduced.

To prevent redundant energy, this offset is

reduced as the instantaneous line voltage

increases. Therefore the offset will be negligible

near the top of the line voltage.

Power Factor Correction

The MP44010 senses the inductor current

through the current sense pin and compares to

the sinusoidal-shaped signal which is generated

from the output of the multiplier. When the

external power MOSFET turns on, the inductor

current rises linearly. When the peak current hits

the sinusoidal-shaped signal, the external power

MOSFET begins to turn off and the diode turns

on. The inductor current also begins to fall. When

the inductor current reaches zero, the power

MOSFET begins to turn on again, which causes

the inductor current to start rising again. The

power circuit works in boundary conduction mode,

and the envelope of the inductor current is

sinusoidal-shaped. The average input current is

half of the peak current, so the average input

current is also sinusoidal-shaped. A high power

factor can be achieved through this control

method.

Multiplier output

Inductor current

Input average current

Figure 4—Inductor Current Waveform

The control flow chart of the MP44010 is shown

in Figure 5.

Turn On

Latch off IC

Very low

consumption

VCC > 12.4V

Y

N

COMP Clamp to

2.2V

Monitor Vcc

Monitor

Vcc< 9.5 V

Y

N

Burst operation

EA output

goes back

to linear

region?

N

Y

Continuous operation

37uA<

OVP step 1:

the Mult output is

forced to decrease

OVP step 2:

Gate driver is

off

Y

N

IC is disabled.

Very low

consumption

Y

N

Figure 5—Control Flow Chart