MP4051—NON-ISOLATED OFFLINE LED CONTROLLER WITH ACTIVE PFC

MP4051 Rev. 1.01

www.MonolithicPower.com

10

1/21/2014

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© 2014 MPS. All Rights Reserved.

OPERATION

The MP4051 is a non-isolated control offline LED

controller which incorporates all the features for

high-performance LED lighting. Active Power

Factor Correction (PFC) eliminates unwanted

harmonic noise to pollute the AC line.

Start Up

Initially, VCC of the MP4051 is charged through

the start up resistor from the AC line. When VCC

reaches 13.6V, the control logic works and the

gate drive signal begins to switch. Then the

power supply is taken over by the auxiliary

winding.

The MP4051 will shut down when VCC drops

below 9V.

Boundary Conduction Mode Operation

increases linearly from zero to the peak value

output diode is turned on and the energy stored

in the inductor is transferred to the load. Then the

from the peak value to zero. The auxiliary

winding is coupled with the inductor to supply the

Vcc voltage and turn on signal detection for ZCD.

The zero-current detector in the ZCD pin

generates the turn-on signal of the external

MOSFET when the ZCD voltage falls below

0.31V (see Figure 3).

As a result, there are virtually no MOSFET turn-

on losses and no output-diode reverse-recover

losses. It ensures high efficiency and low EMI

noise.

Real Current Control

In high-side solution (including both Buck and

Buck-Boost), the current is controlled through FB

Pin, the mean output LED current is directly

sampled by FB pin, so the load regulation of

high-side solution is good. The output LED

current can be set as:

o

FB

V

I

R

In low-side Buck-Boost, the mean output LED

current is calculated through the peak current

sensed from the MOSFET (through CS Pin). And

the mean output LED current can be calculated

approximately as:

≈

⋅

FB

o

s

V

I

2R

0.4V)

the FB RC filter and GND in high-side solution.

MOSFET source and GND in low-side Buck-

Boost.

V

DS

V

V

BUS

I

pk

t

on

turn-on

V

ZCD

0

I

Lm

Figure 2—Boundary Conduction Mode

(Buck-Boost for example)

+

Vcc

ZCD

Auxiliary Winding

0.31V

turn-on

signal

Figure 3—Zero Current Detector