MP4032-2—OFFLINE LED DRIVER WITH FULLY-INTEGRATED INTERNAL MOSFET

MP4032-2 Rev.1.01

www.MonolithicPower.com

12

10/23/2014

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OPERATION

The MP4032-2 is a TRIAC-dimmable, offline LED

driver with an integrated high-voltage MOSFET.

It incorporates multiple features specifically for

high-performance LED lighting. It uses a real-

current-control method to accurately control LED

current. It can achieve a high power factor to

eliminate pollution on the AC-line.

System Start-Up and Power Supply

The VCC pin supplies power to both the control

signal and the gate drive signal. After connecting

the AC line, the VCC capacitor charges from the

DRAIN pin through an internal high-voltage

DRAIN charger. Once VCC reaches 13.8V, the

control logic initiates and the gate drive signal

forces

the

integrated

high-voltage

power

MOSFET to begin switching for normal operation.

Meanwhile, the DRAIN charger stops. The

auxiliary winding takes over the power supply

after charging.

13.8V. If a fault occurs, the system stops

switching and the auto-restart function activates

Power-Factor Correction

The MULT pin connects to the tap of the resistor

divider from the rectified instantaneous line

voltage. It is one of the inputs of the Multiplier.

The multiplier’s output has a sinusoidal shape.

This signal provides the reference for the current

comparator, and is compared with the inductor

current sensed by the CS pin: The CS pin

shapes the inductor peak-current envelope

sinusoid to match the input line voltage. This

control method can achieve a high power factor.

Inductor current

Multiplier output

Input average current

Figure 2: Power-Factor Correction

The maximum voltage of the multiplier output to

the current comparator is clamped to 2.24V to

limit the cycle-by-cycle current.

Boundary-Conduction Mode

increases linearly from zero to the peak value

energy stored in the inductor transfers to the LED

load and turns on the output rectifier diode to

decrease linearly from the peak value to zero.

When the inductor current reaches zero, the

magnetizing inductance and all the parasitic

capacitances decrease the MOSFET drain-

source voltage—this decrease is also reflected

on the auxiliary winding (see Figure 3). The zero-

current detector on the ZCD pin generates the

internal MOSFET’s turn-on signal when the ZCD

voltage falls below 0.35V, and ensures that the

MOSFET turns on at a valley voltage (see Figure

4).

Figure 3: Boundary-Conduction Mode