MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC

MP4031 Rev.1.03

www.MonolithicPower.com

12

5/8/2013

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

© 2013 MPS. All Rights Reserved.

OPERATION

The MP4031 is a TRIAC and analog dimmable,

primary-side–controlled, offline LED controller

designed for high-performance LED lighting. The

MP4031 can accurately control the LED current

using the real-current–control method based on

primary-side information. It can also achieve a

high power factor to eliminate noise pollution on

the AC line. The integrated VCC charging circuit

can achieve fast start-up without any perceptible

delay. The MP4031 is suitable for TRIAC-based

dimming with an extended dimming range. And

the

special

current

sense

structure

can

implement analog dimming.

Boundary-Conduction Mode

rectified input voltage applied across the primary-

increases linearly from zero to the peak value

energy stored in the inductor forces the

secondary-side diode to turn on, and the inductor

current decreases linearly from the peak value to

zero. When the current decreases to zero, the

parasitic resonance caused by the inductor and

the combined parasitic capacitances decreases

the MOSFET drain-source voltage that is also

reflected on the auxiliary winding (see Figure 2).

The zero-current detector generates the external

MOSFET turn-on signal when the ZCD voltage

falls below 0.35V after a blanking time and

ensures the MOSFET turns on at a relatively low

voltage (see Figure 3).

turn-on

0

Inductor

current

Figure 2: Boundary-Conduction Mode

+

Vcc

ZCD

Auxiliary Winding

0.35V

Figure 3: Zero-Current Detector

As a result, there are virtually no primary-switch

turn-on losses and no secondary-diode reverse-

recovery losses. This ensures high efficiency and

low EMI noise.

Real-Current Control

The

proprietary

real-current–control

method

allows the MP4031 to control the secondary-side

LED current based on primary-side information.

The output LED mean current can be calculated

approximately as:

FB

o

s

NV

I

2R

⋅

≈

⋅