MP4030—PRIMARY-SIDE-CONTROL, OFFLINE LED CONTROLLER WITH PFC

MP4030 Rev.1.02

www.MonolithicPower.com

12

4/16/2013

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© 2013 MPS. All Rights Reserved.

OPERATION

The MP4030 is a TRIAC-dimmable, primary-side-

control, offline LED controller designed for high-

performance LED lighting. The MP4030 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.

fast start-up without any perceptible delay. The

MP4030 is suitable for TRIAC-based dimming

with an extended dimming range.

Boundary-Conduction Mode

rectified input voltage applied across the primary-

side inductor (Lm) increases the primary current

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).

I

P

Turn ON

0

Inductor

current

I

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 MP4030 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







Where:

 N is the turn ratio of the primary side to the

secondary side,

(typically 0.4), and

MOSFET source and GND.

Power-Factor Correction

The MULT pin connects to the tap of a resistor

divider from the rectified instantaneous line

voltage. The multiplier output also has a

sinusoidal shape. This signal provides the

reference for the current comparator against the

primary-side–inductor current, which shapes the

primary-peak current into a sinusoid with the

same phase as the input line voltage. This

achieves a high power factor.