MP44011 – BOUNDARY-MODE PFC CONTROLLER WITH HARMONIC INJECTION

MP44011 Rev. 1.01

www.MonolithicPower.com

9

1/12/2012

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© 2012 MPS. All Rights Reserved.

APPLICATIONS

The MP44011 is a boundary-conduction–mode

PFC controller with internal harmonic injection

that is optimized for LED lighting drivers.

Output Voltage Regulation

The FB pin senses the output voltage through a

resistor divider from the output voltage to ground.

An accurate on-chip reference voltage and a

high-performance

error

amplifier

accurately

regulate the output voltage.

Over-Voltage Protection

MP44011 offers two of over-voltage protection

methods: dynamic and static. These two

methods ensure that the circuit operates in a

reliably safe region.

When the load is very low, the output voltage

tends to stay steadily above the nominal value.

Under this condition, the error amplifier output

saturates low. When the error amplifier output

falls below 2.2V, the static OVP triggers and

blocks the gate driver to turn off the external

power MOSFET and enter an idle state. Normal

operation resumes until the error amplifier output

goes back into the regulated region.

2.5V

+

-

INV

COMP

UVLO

GATE

Multiplier

Overvoltage

detection

Driver

Vo

R9

R10

Figure 2: OVP Detector Block

For the boost PFC application, MP44011

implements OVP by monitoring the current

through the COMP pin.

In steady-state operation, the current flows

through the high-side feedback resistor (R9) and

low-side feedback resistor (R10) are:

OFB

FB

R9

R10

VV

V

II

R9

R10







voltage on FB pin remains at the reference value

as the compensation network between FB pin

and COMP pin features a long time-constant for

a high power factor (PF). The current through

through R9 becomes:

'

OO

FB

R9

VV

V

I

R9







The current must flow into the COMP pin. At the

same time, the chip internally monitors the

current. If the current rises to 35µA, the output

voltage of the multiplier decreases, thus reducing

the the energy delivered to output. If the current

rises to about 40µA, the dynamic OVP triggers.

Then gate driver is blocked to turn off the

external power MOSFET and the MP44011

enters an idle state. The device will remain in this

state until the current falls below 10µA. Then the

internal starter is re-enabled and allows switching

to restart.

Disable Function

Pulling the zero current sensing (ZCS) pin lower

than 190mV disables to MP44011 in order to

further reduce the quiescent current when the

PFC pre-regulator needs to be shutdown. After

releasing the ZCS pin, it will stay at lower clamp

voltage if there is no external voltage from the

auxiliary winding.

Boundary Conduction Mode

ZCS

GATE

R

SQ

+

-

2.1V

1.35V

Disable

starter

Driver

Figure 3: ZCS, Triggering, and Disable Block