MP44011 – BOUNDARY-MODE PFC CONTROLLER WITH HARMONIC INJECTION
MP44011 Rev. 1.01 www.MonolithicPower.com 9
1/12/2012 MPS Proprietary Information. Patent Protected.
Unauthorized Photocopy and Duplication Prohibited.
© 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
IR9
IR10
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
If there is an abrupt rise on the output (ΔV
O
), the
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
R10 remains equal to V
FB
/R10, but the current
through R9 becomes:
'
OOFB
R9
VVV
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
Vaux
Figure 3: ZCS, Triggering, and Disable Block
