MP4050 – NON-ISOLATED, HIGH BRIGHTNESS, LED DRIVER

MP4050 Rev.1.02

www.MonolithicPower.com

11

1/18/2016

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OPERATION

MP4050 is a non-isolated, cost-effective, high

efficiency converter designed to drive high-

brightness light emitting diodes (LEDs) from an

85Vac to 265 Vac line, or a DC input. As shown

in the typical application diagram, the regulator

is designed to operate with a minimum number

of external components. It incorporates the

following features:

Start-up and Under Voltage Lock-out (UVLO)

The IC is self supplied by the internal high

voltage regulator which is drawn from the Drain

pin. The IC starts switching and the internal

high voltage regulator turns off as soon as the

the internal high voltage regulator turns on

small capacitor such as several μF capacitor is

smaller capacitor also reduce component cost.

voltage regulator recharges the Vcc capacitor.

When fault conditions happen, such as Short

Lamp Protection, Open Lamp Protection and

Over Temperature Protection (OTP), MP4050

stops working and a 18uA internal current source

time can be calculated by the following equation,

restart

Vcc

Vcc

Vcc 2.37V

4.65V 2.37V

tC

C

18 A

5mA











Figure 2 shows the typical waveform with VCC

under voltage lock out.

VCC

Internal

Voltage

Regulator

Driving

Signal

ON

OFF

Figure 2: VCC Under-Voltage Lock Out

(UVLO)

Constant Current Operation

MP4050 is a fully integrated regulator, the

internal feedback logic responds to the internal

sample and hold circuit to achieve constant

output current regulation. The voltage of the

the internal reference 0.194V, when the

reference voltage, which indicates insufficient

output current, the integrated MOSFET is

turned ON. The ON period is determined by the

peak current limit. After the ON period elapses,

the integrated MOSFET is turned OFF. The

detail operation is shown as Figure 3.

MOS

Diode

0.194V

Thus by monitoring the internal sampling

capacitor voltage, the output current can be

regulated and the output current is determined

by the following equation:

O

0.194V

I

R1

