MP4056—TRIAC DIMMABLE, NON-ISOLATED OFFLINE LED CONTROLLER WITH APFC

MP4056 Rev.1.01

www.MonolithicPower.com

16

11/9/2016

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

© 2016 MPS. All Rights Reserved.

OPERATION

The MP4056 is a non-isolated TRIAC and PWM

dimmable, offline LED controller designed for

high-performance LED lighting. The adaptive

dimmer type detection and phase-cut-based

dimming control bring good dimmer compatibility

and deep dimming range.

It achieves a high

power factor to eliminate noise pollution on the

AC line. The integrated VCC charging circuit

achieves fast start-up without any perceptible

delay. The programmable thermal current fold

back function prolongs the life time of the LED.

Because duty ratio varies inversely to the

dimming

cycle,

it

easily

supports

color

temperature and brightness control for warm

sunset dimming applications. The MP4056 also

supports analog dimming with PWM input.

Boundary-Conduction Mode

increases linearly from zero to the peak value

turn on, and the inductor current decreases

linearly from the peak value to zero. When the

current decreases to zero, the voltage drop on

the main MOSFET drain-to-source falls and

oscillates.

The

oscillation

frequency

is

determined by the inductor and the combined

parasitic

capacitances.

The

resonance

is

reflected on the auxiliary winding (see Figure 2).

V

DS

V

V

BUS

I

pk

t

on

t urn-on

V

ZCD

0

I

Lm

Figure 2: Boundary-Conduction Mode

+

Vcc

ZCD

Auxiliary Winding

Figure 3: Zero-Current Detector

The zero-current detector generates the external

MOSFET turn-on signal when the ZCD voltage

and ensures the MOSFET turns on at a relatively

low voltage (see Figure 3).

As a result, there are relatively small switching on

losses and no diode reverse-recovery losses.

This ensures high efficiency and low EMI noise

Real-Current Control

The

proprietary

real-current

–control

method

allows the MP4056 to control the output LED

current based on the inductor current information.

The approximate output LED mean current can

be calculated as:





REF

o

s

V

I

2R

Where:

 V

REF

is

the

internal

reference

voltage

(typically 0.414), and

 R

MOSFET source and GND.

Power-Factor Correction

The MULT pin is connected to the tap of a

resistor divider from the rectified instantaneous

line voltage, driving a sinusoidal multiplier output.

This signal provides the reference for the current

comparator, which shapes the primary-peak

current into a sinusoid and has the same phase

with the input line voltage. This guarantees a

high power factor.