MP44014 – BOUNDARY MODE PFC CONTROLLER

MP44014 Rev. 1.01

www.MonolithicPower.com

10

11/10/2015

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OPERATION

The MP44014 is a boundary conduction mode

PFC controller optimized for the PFC pre-

regulator up to 300W and fully complies with

IEC1000-3-2 specification.

Output Voltage Regulation

The output voltage is sensed at FB through a

resistor divider from the output voltage to ground.

The accurate on-chip reference voltage and the

high performance error amplifier regulate the

output voltage accurately.

Over-Voltage Protection (OVP)

The MP44014 offers two stages of over-voltage

protection: dynamic over-voltage protection and

static over-voltage protection. With two-stage

protection, the circuit operates reliably.

The MP44014 achieves OVP by monitoring the

current flow through COMP.

During steady-state operation, the current flow

through the high-side feedback resistor (R9) and

the low-side feedback resistor (R10) is calculated

with Equation (1):

OFB

FB

R9

R10

VV

V

II

R9

R10







(1)

the compensation network connected between

FB and COMP takes time to achieve high power

factor (PF) due to the long RC time constant, the

voltage on FB will still be kept at the reference

value. The current through R10 remains equal to

calculated with Equation (2):

'

OO

FB

R9

VV

V

I

R9







(2)

This

current

has

to

flow

into

COMP.

Simultaneously, this current is monitored inside

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

voltage of the multiplier will be forced to decrease,

and the energy delivered to the output will be

reduced. If this current continues to rise to about

40µA, the dynamic OVP can be triggered.

Consequently, the gate driver is blocked to turn

off the external power MOSFET, and the device

enters an idle state. This state is maintained until

the current falls below 10µA, the point at which

the internal starter will be re-enabled and allow

the switching to restart.

When the load is very light, the output voltage

tends to stay steadily above the nominal value. In

this condition, the error amplifier output will

saturate low. When the error amplifier output is

lower than 2.25V, static OVP will be triggered.

Consequently, the gate driver will be blocked to

turn off the external power MOSFET, and the

device will enter an idle state. Normal operation

resumes once the error amplifier output returns

to the regulated region (see Figure 2).

Figure 2: OVP Detector Block

Disable Function

The MP44014 can be disabled by pulling the

zero-current sensing (ZCS) pin lower than

190mV. This helps to further reduce quiescent

current when the PFC pre-regulator needs to be

shut down. After releasing ZCS, it will stay at a

lower clamp voltage when there is no external

voltage from the auxiliary winding (see Figure 3).

Figure 3: ZCS Triggering and Disable Block